U.S. patent application number 09/729338 was filed with the patent office on 2001-08-30 for temperature compensated oscillator, method of controlling temperature compensated oscillator, and wireless communication device.
Invention is credited to Oka, Manabu.
Application Number | 20010017574 09/729338 |
Document ID | / |
Family ID | 26578286 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010017574 |
Kind Code |
A1 |
Oka, Manabu |
August 30, 2001 |
Temperature compensated oscillator, method of controlling
temperature compensated oscillator, and wireless communication
device
Abstract
A temperature compensated oscillator, a method of controlling a
temperature compensated oscillator, and a wireless communication
device are provided, where phase noise of the output signal can be
reduced, frequency of the output signal stabilizes within a short
time, and response of control does not become worse. Accordingly, a
filter circuit is provided that removes noise contained in a
temperature compensation voltage. A switching circuit is connected
in parallel to this filter circuit. A power control circuit
controls power supply to a voltage controlled oscillation circuit
28 and the like. The power control circuit turns on the switching
circuit for a specified period when power supply to the voltage
controlled oscillation circuit is started.
Inventors: |
Oka, Manabu; (Minowa-machi,
JP) |
Correspondence
Address: |
Oliff & Berridge PLC
P.O. Box 19928
Alexandria
VA
22320
US
|
Family ID: |
26578286 |
Appl. No.: |
09/729338 |
Filed: |
December 5, 2000 |
Current U.S.
Class: |
331/116R ;
331/158; 331/176; 331/177V |
Current CPC
Class: |
H03L 1/025 20130101;
H03L 1/023 20130101 |
Class at
Publication: |
331/116.00R ;
331/158; 331/176; 331/177.00V |
International
Class: |
H03B 005/32; H03B
005/36; H03L 001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2000 |
JP |
JP 2000-239003 |
Dec 6, 1999 |
JP |
JP 11-346499 |
Claims
What is claimed is:
1. A temperature compensated oscillator that has a voltage
controlled oscillation circuit where an output signal oscillation
frequency changes according to supplied voltage and a temperature
compensation circuit that outputs temperature compensation voltage
for keeping said output signal oscillation frequency constant based
on temperature, the temperature compensated oscillator comprising:
a filter circuit that removes noise contained in the temperature
compensation voltage; a switching circuit connected in parallel
with said filter circuit, and a power control circuit that controls
power supply at least to said voltage controlled oscillation
circuit and said temperature compensation circuit, respectively,
said power control circuit turning on said switching circuit for a
specified period when power supply to said voltage controlled
oscillation circuit is started.
2. A temperature compensated oscillator that has a voltage
controlled oscillation circuit whose output signal oscillation
frequency changes according to supplied voltage and a temperature
compensation circuit that outputs temperature compensation voltage
for keeping said output signal oscillation frequency constant based
on temperature, the temperature compensated oscillator comprising:
a filter circuit that removes noise contained in said temperature
compensation voltage that is a low-pass filter having capacitance
elements connected in parallel to resistor elements via a switching
circuit, and a power control circuit that controls power supply at
least to said voltage controlled oscillation circuit and said
temperature compensation circuit, respectively, said switching
circuit switching connection locations of one end of all of said
capacitance elements between a temperature compensation voltage
output side and a temperature compensation voltage input side of
said resistor elements, and said power control circuit controlling
said switching circuit to connect one end of said capacitance
elements to the temperature compensation voltage input side of said
resistor elements when power supply to said voltage controlled
oscillation circuit is started, and to the temperature compensation
voltage output side of said resistor elements after a specified
time period has passed.
3. A temperature compensated oscillator that has a voltage
controlled oscillation circuit whose output signal oscillation
frequency changes according to supplied voltage and a temperature
compensation circuit that outputs temperature compensation voltage
for keeping said output signal oscillation frequency constant based
on temperature, the temperature compensated oscillator comprising:
a filter circuit that removes noise contained in said temperature
compensation voltage that has a plurality of stages of low-pass
filters having capacitance elements connected in parallel to
resistor elements via a switching circuit, and a power control
circuit that controls power supply at least to said voltage
controlled oscillation circuit and said temperature compensation
circuit, respectively, said switching circuit switching connection
locations of one end of all of said capacitance elements between a
temperature compensation voltage output side of each corresponding
resistor element and a temperature compensation voltage input side
of a resistor element closest to said temperature compensation
circuit among all of said resistor elements, and said power control
circuit controlling said switching circuit to connect one end of
all of said capacitance elements to the temperature compensation
voltage input side of the resistor element closest to said
temperature compensation circuit when power supply to said voltage
controlled oscillation circuit is started and to said temperature
compensation voltage output side of each corresponding resistor
element after a specified time period has passed.
4. The temperature compensated oscillator described in claim 3,
inductance elements are used in place of said resistor elements in
said filter circuit.
5. The temperature compensated oscillator described in claim 3,
further comprising: an output switching circuit, between said
temperature compensation circuit and said filter circuit, that
switches between a first mode where the output voltage follows the
temperature compensation voltage, and a second mode where the
output voltage is maintained at the temperature compensation
voltage of the mode switching time, said power control circuit
switching said output switching circuit to said first mode when
power supply to said temperature compensation circuit is started,
and to the second mode when power supply to said temperature
compensation circuit is stopped.
6. A temperature compensated oscillator that has a voltage
controlled oscillation circuit whose output signal oscillation
frequency changes according to supplied voltage and a temperature
compensation circuit that outputs temperature compensation voltage
for keeping said output signal oscillation frequency constant based
on temperature, the temperature compensated oscillator comprising:
an output switching circuit that switches between a first mode
where the output voltage follows said temperature compensation
voltage, and a second mode where the output voltage is maintained
at said temperature compensation voltage of the mode switching
time; a filter circuit that removes noise contained in said
temperature compensation voltage output via said output switching
circuit; and a power control circuit that controls power supply at
least to said voltage controlled oscillation circuit and said
temperature compensation circuit, respectively, said power supply
circuit switching said output switching circuit to said first mode
when power supply to said temperature compensation circuit is
started, and to said second modewhen power supply to said
temperature compensation circuit is stopped.
7. The temperature compensated oscillator described in claim 6,
said power control circuit stopping power supply to circuits other
than said output switching circuit, when power supply to said
voltage controlled oscillator and said temperature compensation
circuit are stopped.
8. A temperature compensated oscillator that has a voltage
controlled oscillation circuit whose output signal oscillation
frequency changes according to supply voltage, a temperature
compensation circuit that outputs temperature compensation voltage
for keeping the output signal oscillation frequency constant based
on temperature, a voltage control circuit that outputs frequency
control voltage for making the output signal oscillation frequency
the frequency to be set based on an externally supplied frequency
control signal, and an adder that outputs said temperature
compensation voltage and said frequency control voltage added
together, the temperature compensated oscillator comprising: a
first filter circuit that removes noise contained in said
temperature compensation voltage; a switching circuit connected in
parallel with said first filter circuit; a second filter circuit
that removes noise contained in said frequency control voltage; and
a power control circuit that controls power supply at least to said
voltage controlled oscillation circuit and said temperature
compensation circuit, respectively, said power control circuit
turning on said switching circuit for a specified period of time
when power supply to said voltage controlled oscillation circuit is
started.
9. A temperature compensated oscillator that has a voltage
controlled oscillation circuit whose output signal oscillation
frequency changes according to supplied voltage, a temperature
compensation circuit that outputs temperature compensation voltage
for keeping said output signal oscillation frequency constant based
on temperature, a voltage control circuit that outputs frequency
control voltage for making said output signal oscillation frequency
the frequency to be set based on the externally supplied frequency
control signal, and an adder that outputs said temperature
compensation voltage and said frequency control voltage added
together, the temperature compensated oscillator comprising: a
first filter circuit that removes noise contained in said
temperature compensation voltage and that is a low-pass filter
having capacitance elements connected in parallel to resistor
elements; a second filter circuit that removes noise contained in
said frequency control voltage; a power control circuit that
controls power supplied at least to said voltage controlled
oscillation circuit and said temperature compensation circuit,
respectively; and a switching circuit that switches connection
locations of one end of all of said capacitance elements between a
temperature compensation voltage output side and a temperature
compensation voltage input side, said power control circuit using
said switching circuit to connect one end of said capacitance
elements to the temperature compensation voltage input side of said
resistor elements when power supply to said voltage controlled
oscillation circuit is started, and to the temperature compensation
voltage output side of said resistor elements after a specified
time period has passed.
10. A temperature compensated oscillator that has a voltage
controlled oscillation circuit whose output signal oscillation
frequency changes according to supplied voltage, a temperature
compensation circuit that outputs temperature compensation voltage
for keeping said output signal oscillation frequency constant based
on temperature, a voltage control circuit that outputs frequency
control voltage for making said output signal oscillation frequency
the frequency to be set based on the externally supplied frequency
control signal, and an adder that outputs said temperature
compensation voltage and said frequency control voltage added
together, the temperature compensated oscillator comprising: a
first filter circuit that removes noise contained in said
temperature compensation voltage and that is a low-pass filter
having a plurality of stages having capacitance elements connected
in parallel to resistor elements; a second filter circuit that
removes noise contained in said frequency control voltage; a power
control circuit that controls power supply at least to said voltage
controlled oscillation circuit and said temperature compensation
circuit, respectively; and a switching circuit that switches
connection locations of one end of all said capacitance elements
between a temperature compensation voltage output side of each
corresponding resistor element and a temperature compensation
voltage input side of a resistor element closest to said
temperature compensation circuit among all of said resistor
elements, said power control circuit controlling said switching
circuit to connect one end of said capacitance elements to the
temperature compensation voltage input side of said resistor
element closest to said temperature compensation circuit when power
supply to the voltage controlled oscillation circuit is started,
and to the temperature compensation voltage output side of each
corresponding resistor element after a specified time period has
passed.
11. The temperature compensated oscillator described in claim 10,
an inductance element being used in place of said resistance
element in said first filter circuit.
12. The temperature compensated oscillator described in claim 8,
further comprising an output switching circuit between said
temperature compensation circuit and said first filter circuit that
can switch between a first mode where the output voltage follows
the temperature compensation voltage, and a second mode where the
output voltage is maintained at the temperature compensation
voltage of the mode switching time, said power control circuit
switching said output switching circuit to said first mode when
power supply to said temperature compensation circuit is started,
and to said second mode when power supply to said temperature
compensation circuit is stopped.
13. A temperature compensated oscillator that has a voltage
controlled oscillation circuit in which output signal oscillation
frequency changes according to supplied voltage, a temperature
compensation circuit that outputs temperature compensation voltage
for keeping said output signal oscillation frequency constant based
on temperature, a voltage control circuit that outputs frequency
control voltage for making said output signal oscillation frequency
the frequency to be set based on the externally supplied frequency
control signal, and an adder that outputs said temperature
compensation voltage and said frequency control voltage added
together, the temperature compensated oscillator comprising: an
output switching circuit that switches between a first mode where
the output voltage follows said temperature compensation voltage,
and a second mode where the output voltage is maintained at said
temperature compensation voltage of a mode switching time; a first
filter circuit that removes noise contained in said temperature
compensation voltage output via said output switching circuit; a
second filter circuit that removes noise contained in said
frequency control voltage; and a power control circuit that
controls power supply at least to said voltage controlled
oscillation circuit and said temperature compensation circuit,
respectively, said power control circuit switching said output
switching circuit to said first mode when power supply to the
temperature compensation circuit is started, and to said second
mode when power supply to said temperature compensation circuit is
stopped.
14. The temperature compensated oscillator described in claim 13,
said power control circuit stoping power supply to circuits other
than said output switching circuit when power supply to said
voltage controlled oscillation circuit and said temperature
compensation circuit are stopped.
15. The temperature compensated oscillator described in claim 13, a
cutoff frequency of said second filter circuit being higher than a
cut-off frequency of said first filter circuit.
16. The temperature compensated oscillator described in claim 13,
said second filter circuit comprising resistor elements and
capacitance elements, respectively.
17. The temperature compensated oscillator described in claim 13,
said second filter circuit comprising inductance chips and
capacitance elements, respectively.
18. The temperature compensated oscillator described in claim 13,
said power control circuit controlling power supply to said voltage
controlled oscillation circuit and said temperature compensation
circuit based on the externally supplied control signal.
19. The temperature compensated oscillator described in claim 13,
said power control circuit starting power supply to said voltage
controlled oscillation circuit and said temperature compensation
circuit at the same time and said power supply being stopped at the
same time.
20. The temperature compensated oscillator described in claim 13,
said voltage controlled oscillation circuit comprising an
oscillation circuit that oscillates an piezoelectric resonator and
a variable capacitance element having capacitance changes according
to voltage supplied.
21. The temperature compensated oscillator described in claim 13,
component parts, except said piezoelectric resonator, being
constructed as a one-chip IC.
22. The temperature compensated oscillator described in claim 21,
said one-chip IC and said piezoelectric resonator being stored in
one package.
23. A wireless communication device comprising said temperature
compensated oscillator described in claim 22, and operating based
on the output signal of said temperature compensated oscillation
circuit.
24. A method of controlling a temperature compensated oscillator
that has a voltage controlled oscillation circuit whose output
signal oscillation frequency changes according to supplied voltage,
and a temperature compensation circuit that outputs temperature
compensation voltage for keeping said output signal oscillation
frequency constant based on temperature, the method comprising:
removing noise contained in said temperature compensation voltage
using a filter circuit; and controlling power supply to at least
said voltage controlled oscillation circuit and said temperature
compensation circuit, respectively, using a power control circuit,
said power control circuit turning on a switching circuit connected
in parallel with said filter circuit only for a specified time
period when power supply to said voltage controlled oscillation
circuit is started.
25. The method of controlling a temperature compensated oscillator
described in claim 24, further comprising: switching between a
first mode where the output voltage follows said temperature
compensation voltage and a second mode where the output voltage is
maintained at said temperature compensation voltage of a mode
switching time, using an output switching circuit between said
temperature compensation circuit and said filter circuit, said
power control circuit switching said output switching circuit to
said first mode when power supply to said temperature compensation
circuit is started, and switching said output switching circuit to
said second mode when power supply to said temperature compensation
circuit is stopped.
26. A method of controlling a temperature compensated oscillator
that has a voltage controlled oscillation circuit whose output
signal oscillation frequency changes according to supplied voltage,
and a temperature compensation circuit that outputs temperature
compensation voltage for keeping said output signal oscillation
frequency constant based on temperature, the method comprising:
switching between a first mode where the output voltage follows
said temperature compensation voltage, and a second mode where the
output voltage is maintained at said temperature compensation
voltage of the mode switching time, using an output switching
circuit; removing noise contained in said temperature compensation
voltage output via said output switching circuit using a filter
circuit; and controlling power supply to at least said voltage
controlled oscillation circuit and said temperature compensation
circuit, respectively, using a power control circuit, said power
control circuit switching said output switching circuit to said
first mode when power supply to said temperature compensation
circuit is started, and switching said output switching circuit to
said second mode when power supply to said temperature compensation
circuit is stopped.
27. The method of controlling a temperature compensated oscillator
described in claim 26, said power control circuit stopping power
supply to circuits other than said output switching circuit, when
power supply to said voltage controlled oscillation circuit and
said temperature compensation circuit are stopped.
28. A method of controlling a temperature compensated oscillator
that has a voltage controlled oscillation circuit whose output
signal oscillation frequency changes according to supplied voltage,
a temperature compensation circuit that outputs temperature
compensation voltage for keeping said output signal oscillation
frequency constant based on temperature, a voltage control circuit
that outputs frequency control voltage for making said output
signal oscillation frequency the frequency to be set based on the
externally supplied frequency control signal, and an adder that
outputs said temperature compensation voltage and said frequency
control voltage added together, the method comprising: removing
noise contained in said temperature compensation voltage using a
first filter circuit; removing noise contained in said frequency
control voltage using a second filter circuit; and controlling
power supply at least to said voltage controlled oscillation
circuit and said temperature compensation circuit, respectively,
using a power control circuit, said power control circuit turning
on a switching circuit connected in parallel with said first filter
circuit for a specified time period when power supply to said
voltage controlled oscillation circuit is started.
29. The method of controlling a temperature compensated oscillator
described in claim 28, further comprising: switching between a
first mode where the output voltage follows said temperature
compensation voltage, and a second mode where the output voltage is
maintained at said temperature compensation voltage of a mode
switching time, using an output switching circuit between said
temperature compensation circuit and said first filter circuit,
said power control circuit switching said output switching circuit
to said first mode when power supply to said temperature
compensation circuit is started, and switching said output
switching circuit to said second mode when power supply to the
temperature compensation circuit is stopped.
30. A method of controlling a temperature compensated oscillator
that has a voltage controlled oscillation circuit whose output
signal oscillation frequency changes according to supplied voltage,
a temperature compensation circuit that outputs temperature
compensation voltage for keeping said output signal oscillation
frequency constant based on temperature, a voltage control circuit
that outputs frequency control voltage for making said output
signal oscillation frequency the frequency to be set based on
externally supplied frequency control signals, and an adder that
outputs said temperature compensation voltage and said frequency
control voltage added together, the method comprising: switching
between a first mode where the output voltage follows said
temperature compensation voltage, and a second mode where the
output voltage is maintained at said temperature compensation
voltage of a mode switching time, using an output switching
circuit; removing noise contained in said temperature compensation
voltage output via said output switching circuit using a first
filter circuit; removing noise contained in said frequency control
voltage using a second filter circuit; and controlling power supply
at least to said voltage controlled oscillation circuit and said
temperature compensation circuit, respectively, using a power
control circuit, said power control circuit switching said output
switching circuit to said first mode when power supply to the
temperature compensation circuit is started, and switching said
output switching circuit to said second mode when power supply to
said temperature compensation circuit is stopped.
31. The method of controlling a temperature compensated oscillator
described in claim 30, said power control circuit stoping power
supply to circuits other than said output switching circuit when
power supply to said voltage controlled oscillation circuit and
said temperature compensation circuit are stopped.
32. The method of controlling a temperature compensated oscillator
described in claim 30, said power control circuit controlling power
supply to said voltage controlled oscillation circuit and said
temperature compensation circuit based on an externally supplied
control signal.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] This invention relates to a temperature compensated
oscillator, a control method for a temperature compensated
oscillator, and a wireless communication device.
[0003] 2. Description of Related Art
[0004] Conventionally, as oscillators used for electronic
equipment, such as wireless communication devices, a temperature
compensated oscillator (TCXO) is used because the output of
frequency signals needs to be stable over a wide temperature
range.
[0005] This temperature compensated oscillator utilizes the fact
that oscillation frequency of a piezoelectric resonator changes
according to the load capacity in order to maintain the oscillation
frequency constant through a temperature compensation circuit in
which the load capacity is varied according to temperature.
[0006] Also, among the temperature compensated oscillators, there
are analog oscillators where the temperature compensation circuit
is constructed by an analog circuit, and digital oscillators where
the temperature compensation circuit is constructed by a digital
circuit.
[0007] In an analog temperature compensated oscillator, because the
temperature compensated circuit consists of many resistor elements
and semiconductor elements, noise Vn is added to the temperature
compensation voltage Vc1 output by the temperature compensation
circuit due to thermal noise, shot noise, and the like.
[0008] Therefore, in the analog temperature compensated oscillator
shown in FIG. 15, by inserting a filter circuit 2 that removes the
high-frequency component between a temperature compensation circuit
3 and a voltage controlled oscillation circuit 4, noise Vn can be
removed from the output voltage Vc1+Vn of the temperature
compensation circuit 3.
[0009] In this way, by installing the filter circuit 2 that removes
noise contained in the temperature compensation voltage Vc1 output
from the temperature compensation circuit 3, phase noise of the
output signal is reduced.
[0010] FIG. 16 is a block diagram of a digital temperature
compensated oscillator.
[0011] In a digital temperature compensated oscillator 10, a
temperature compensation circuit 11 consists, for example, of a
temperature sensor 11A, an analog/digital (A/D) converter 11B, a
memory 11C, and a digital/analog (D/A) converter 11D.
[0012] In the temperature compensation circuit 11, temperature
information measured by the temperature sensor 11A is converted
from analog to digital by the A/D converter 11B, converted to
digital signal for compensating the temperature property of a
piezoelectric resonator X memorized in advance in the memory 11C,
converted from digital to analog by the D/A converter 11D, and
output as temperature compensation voltage Vc1.
[0013] In this case, if any change occurs to the digital signal
input to the D/A converter 11D due to temperature change,
step-shape noise Vn occurs to the temperature compensation voltage
Vc1 due to influence of resolution of the D/A converter 11D.
[0014] Because of this, as shown in FIG. 16, by inserting the
filter circuit 2 that removes the high-frequency component between
the temperature compensation circuit 11 and the voltage controlled
oscillation circuit (VCXO) 4, noise Vn is removed from the
temperature compensation voltage Vc1.
[0015] Therefore, by using a filter circuit such as an analog one
in a digital temperature compensated oscillator, phase noise of the
output signal can be reduced.
SUMMARY OF THE INVENTION
[0016] As in a property curve of a filter circuit (LPF), such as
that shown in FIG. 17, the larger the time constant, namely the
lower the cut-off frequency fc, the more decline high frequency
shows in a filter circuit.
[0017] Because of this, for reducing phase noise of output signals
of a temperature compensated oscillator using a filter circuit, it
is better to set the cut-off frequency fc of the filter circuit
low. Here, shown in FIG. 18 is a property curve between the SSB
phase noise at the detuning frequency and cut-off frequency fc of a
filter circuit.
[0018] On the other hand, when power is supplied intermittently to
a temperature compensated oscillator, from a power-saving point of
view as in the standing-by time for a portable wireless
communication device, reduction of time from the oscillation start
until the output frequency becomes stable (called "Oscillation
starting time" below) is desired.
[0019] However, as in a property curve of the oscillation starting
time shown in FIG. 19, the lower the cut-off frequency of a filter
circuit is set, the longer the oscillation starting time Tsta
becomes.
[0020] Because of this, in a temperature compensated oscillator,
there is a problem that realization of both reduction of phase
noise of the output signal and reduction of the oscillation
starting time is difficult.
[0021] Also, as shown in FIG. 20, common as an oscillator of modem
portable wireless communication devices is a VC-TCXO that is
equipped with a frequency control voltage input terminal VC for the
frequency adjustment function that adjusts the frequency even more
precisely based on the signal from the base station.
[0022] Namely, as shown in FIG. 20, VC-TCXO 12 inputs a frequency
control signal .phi.VC supplied to a signal processing circuit of a
portable wireless communication device based on the signal received
from the base station, and converts the voltage of this frequency
control signal .phi.VC to a frequency control voltage Vc2 by a
voltage conversion circuit 13.
[0023] Then, in VC-TCXO 12, the frequency control voltage Vc2 and
temperature compensation voltage Vc1 are added by an adder 14 that
is supplied to a voltage controlled oscillation circuit 4 via the
filter circuit 2. By this, frequency of the output signal is
temperature compensated and changed to the frequency synchronous to
the base frequency of the base station.
[0024] In the circuit described above, if phase noise of the output
signal is reduced using a filter circuit 2 with a large time
constant, a problem also occurs in that response of the oscillation
frequency to the frequency control voltage Vc2 is not good.
[0025] One objective of this invention is to at least provide a
temperature compensated oscillator where phase noise of the output
signal can be reduced, frequency of the output signal stabilizes in
a short time, and response of the control is good. In accordance
with various exemplary embodiments of this invention, a method of
controlling and a wireless communication device equipped with this
temperature compensated oscillator are provided.
[0026] In accordance with one exemplary embodiment of this
invention, a temperature compensated oscillator is provided that
has a voltage controlled oscillation circuit whose output signal
oscillation frequency changes according to supplied voltage, and a
temperature compensation circuit that outputs temperature
compensation voltage for keeping the oscillation frequency of the
output signal constant based on temperature.
[0027] filter circuit that removes noise contained in the
temperature compensation voltage;
[0028] switching circuit connected in parallel with the filter
circuit; and
[0029] power control circuit that controls power supply at least to
the voltage controlled oscillation circuit and the temperature
compensation circuit, respectively,
[0030] wherein the power control circuit turns on the switching
circuit for a specified period when power supply to the voltage
controlled oscillation circuit is started.
[0031] In accordance with another exemplary embodiment of this
invention, a temperature compensated oscillator is provided that
has a voltage controlled oscillation circuit whose output signal
oscillation frequency changes according to supplied voltage and a
temperature compensation circuit that outputs temperature
compensation voltage for keeping the output signal oscillation
frequency constant based on temperature, comprising;
[0032] filter circuit for removing noise contained in the
temperature compensation circuit that is a low-pass filter where
capacitance elements are connected in parallel to resistor elements
via a switching circuit; and
[0033] power control circuit that controls power supply at least to
the voltage controlled oscillation circuit and the temperature
compensation circuit, respectively,
[0034] wherein the switching circuit is circuit for switching the
connection locations of one end of all of the capacitance elements
between the temperature compensation voltage output side and the
temperature compensation voltage input side of the resistor
elements, and the power control circuit connects by the switching
circuit one end of the capacitance elements to the temperature
compensation voltage input side of the resistor elements when power
supply to the voltage controlled oscillation circuit is started and
to the temperature compensation voltage output side of the resistor
elements after a specified period has passed.
[0035] In accordance with another exemplary embodiment of this
invention, a temperature compensated oscillator is provided that
has a voltage controlled oscillation circuit whose output signal
oscillation frequency changes according to supplied voltage and a
temperature compensation circuit that outputs temperature
compensation voltage for keeping the output signal oscillation
frequency constant based on temperature. The temperature
compensated oscillator may include a filter circuit that removes
noise contained in the temperature compensation circuit that is a
plurality of stages of low-pass filters where capacitance elements
are connected in parallel to resistor elements via a switching
circuit, and a power control circuit that controls power supply at
least to the voltage controlled oscillation circuit and the
temperature compensation circuit, respectively. The switching
circuit is a circuit for switching the connection locations of one
end of all of the capacitance elements between the temperature
compensation voltage output side of each corresponding resistor
element and the temperature compensation voltage input side of the
resistor element closest to the temperature compensation circuit
among all of the resistor elements. The power control circuit
connects, by the switching circuit, one end of all of the
capacitance elements to the temperature compensation voltage input
side of the resistor element closest to the temperature
compensation circuit when power supply to the voltage controlled
oscillation circuit is started, and to the temperature compensation
voltage output side of each corresponding resistor element after a
specified period has passed.
[0036] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, inductance elements are used in place of the resistor
elements in the filter circuit.
[0037] In accordance with another exemplary embodiment of this
invention, the temperature compensated oscillator described above
has an output switching circuit between the temperature
compensation circuit and the filter circuit which can switch
between a first mode where the output voltage follows the
temperature compensation voltage, and a second mode where the
output voltage is maintained at the temperature compensation
voltage of the mode switching time. the power control circuit
switches the output switching circuit to the first mode when power
supply to the temperature compensation circuit is started and the
output switching circuit to the second mode when power supply to
the temperature compensation circuit is stopped.
[0038] In accordance with another exemplary embodiment of this
invention, a temperature compensated oscillator is provided that
has a voltage controlled oscillation circuit whose output signal
oscillation frequency changes according to supplied voltage and a
temperature compensation circuit that outputs temperature
compensation voltage for keeping the output signal oscillation
frequency constant based on temperature. The temperature
compensated oscillator may include an-output switching circuit
which can switch between a first mode where the output voltage
follows the temperature compensation voltage, and a second mode
where the output voltage is maintained at the temperature
compensation voltage of the mode switching time, a filter circuit
that removes noise contained in the temperature compensation
voltage output via the output switching circuit, and a power
control circuit that controls power supply at least to the voltage
controlled oscillation circuit and the temperature compensation
circuit, respectively. The power control circuit switches the
output switching circuit to the first mode when power supply to the
temperature compensation circuit is started, and to the second mode
when power supply to the temperature compensation circuit is
stopped.
[0039] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, the power control circuit stops power supply to the
circuits, except the output switching circuit, when power supply to
the voltage controlled oscillator and the temperature compensation
circuit are stopped.
[0040] In accordance with another exemplary embodiment of this
invention, a temperature compensated oscillator is provided that
has a voltage controlled oscillation circuit whose output signal
oscillation frequency changes according to supplied voltage, a
temperature compensation circuit that outputs temperature
compensation voltage for keeping the output signal oscillation
frequency constant based on temperature, a voltage control circuit
that outputs frequency control voltage for making the output signal
oscillation frequency the frequency to be set based on the
externally supplied frequency control signal, and an adder that
outputs the temperature compensation voltage and the frequency
control voltage added together. The temperature compensated
oscillator may include a first filter circuit that removes noise
contained in the temperature compensation voltage, a switching
circuit connected in parallel with the first filter circuit, a
second filter circuit that removes noise contained in the frequency
control voltage, and a power control circuit that controls power
supply at least to the voltage controlled oscillation circuit and
the temperature compensation circuit, respectively. The power
control circuit turns on the switching circuit for a specified
period when power supply to the voltage controlled oscillation
circuit is started.
[0041] In accordance with another exemplary embodiment of this
invention, a temperature compensated oscillator is provided that
has a voltage controlled oscillation circuit whose output signal
oscillation frequency changes according to supply voltage, a
temperature compensation circuit that outputs temperature
compensation voltage for keeping the output signal oscillation
frequency constant based on temperature, a voltage control circuit
that outputs frequency control voltage for making the output signal
oscillation frequency the frequency to be set based on the
externally supplied frequency control signal, and an adder that
outputs the temperature compensation voltage and the frequency
control voltage added together. The temperature compensated
oscillator may include a first filter circuit that is a circuit for
removing noise contained in the temperature compensation voltage
and is a low-pass filter where capacitance elements are connected
in parallel to resistor elements, a second filter circuit that
removes noise contained in the frequency control voltage, and a
power control circuit that controls power supply at least to the
voltage controlled oscillation circuit and the temperature
compensation circuit, respectively. A switching circuit is provided
for switching the connection locations of one end of all of the
capacitance elements between the temperature compensation voltage
output side and the temperature compensation voltage input side of
the resistor elements. The power control circuit connects, by the
switching circuit, one end of the capacitance elements to the
temperature compensation voltage input side of the register
elements when power supply to the voltage controlled oscillation
circuit is started, and to the temperature compensation voltage
output side of the resistor elements after a specified period has
passed.
[0042] In accordance with another exemplary embodiment of this
invention, a temperature compensated oscillator is provided that
has a voltage controlled oscillation circuit whose output signal
oscillation frequency changes according to supplied voltage, a
temperature compensation circuit that outputs temperature
compensation voltage for keeping the output signal oscillation
frequency constant based on temperature, a voltage control circuit
that outputs frequency control voltage for making the output signal
oscillation frequency the frequency to be set based on the
externally supplied frequency control signal, and an adder that
outputs the temperature compensation voltage and the frequency
control voltage added together. The temperature compensated
oscillator may include a first filter circuit that is a circuit for
removing noise contained in the temperature compensation voltage
and is a low-pass filter of plural number of stages where
capacitance elements are connected in parallel to resistor
elements, a second filter circuit that removes noise contained in
the frequency control voltage, and a power control circuit that
controls power supply at least to the voltage controlled
oscillation circuit and the temperature compensation circuit,
respectively. The switching circuit is a circuit for switching the
connection locations of one end of all of the capacitance elements
between the temperature compensation voltage output side of each
corresponding resistor element and the temperature compensation
voltage input side of the resistor element closest to the
temperature compensation circuit among all of the resistor
elements. The power control circuit connects, by the switching
circuit, one end of the capacitance elements to the temperature
compensation voltage input side of the resistor element closest to
the temperature compensation circuit when power supply to the
voltage controlled oscillation circuit is started, and to the
temperature compensation voltage output side of each corresponding
resistor elements after a specified period has passed.
[0043] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, an inductance element is used in place of the resistance
element in the first filter circuit.
[0044] In accordance with another exemplary embodiment of this
invention, the temperature compensated oscillator described above
has, between the temperature compensation circuit and the filter
circuit, an output switching circuit that can switch between a
first mode where the output voltage follows the temperature
compensation voltage, and a second mode where the output voltage is
maintained at the temperature compensation voltage of the mode
switching time. The power control circuit switches the output
switching circuit to the first mode when power supply to the
temperature compensation circuit is started, and to the second mode
when power supply to the temperature compensation circuit is
stopped.
[0045] In accordance with another exemplary embodiment of this
invention, a temperature compensated oscillator is provided that
has a voltage controlled oscillation circuit whose output signal
oscillation frequency changes according to supplied voltage, a
temperature compensation circuit that outputs temperature
compensation voltage for keeping the output signal oscillation
frequency constant based on temperature, a voltage control circuit
that outputs frequency control voltage for making the output signal
oscillation frequency the frequency to be set based on the
externally supplied frequency control signal, and an adder that
outputs the temperature compensation voltage and the frequency
control voltage added together. The temperature compensated
oscillator may include an output switching circuit that can switch
between a first mode where the output voltage follows the
temperature compensation voltage, and a second mode where the
output voltage is maintained at the temperature compensation
voltage of the mode switching time, a first filter circuit that
removes noise contained in the temperature compensation voltage
output via the output switching circuit, a second filter circuit
that removes noise contained in the frequency control voltage, and
a power control circuit that controls power supply at least to the
voltage controlled oscillation circuit and the temperature
compensation circuit, respectively. The power control circuit
switches the output switching circuit to the first mode when power
supply to the temperature compensation circuit is started, and to
the second mode when power supply to the temperature compensation
circuit is stopped.
[0046] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, the power control circuit stops power supply to circuits,
except the output switching circuit, when power supply to the
voltage controlled oscillation circuit and the temperature
compensation circuit are stopped.
[0047] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described in
above, the cut-off frequency of the second filter circuit is higher
than the cut-off frequency of the first filter circuit.
[0048] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, the second filter circuit consists of resistor elements and
capacitance elements, respectively.
[0049] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, the second filter circuit consists of inductance elements
and capacitance elements, respectively.
[0050] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, the power control circuit controls power supply to the
voltage controlled oscillation circuit and the temperature
compensation circuit based on the externally supplied control
signal.
[0051] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, the power control circuit starts power supply to the voltage
controlled oscillation circuit and the temperature compensation
circuit at the same time, and the power supply is stopped at the
same time.
[0052] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, the voltage controlled oscillation circuit has an
oscillation circuit for oscillating an piezoelectric resonator, and
a variable capacitance element whose capacitance changes according
to the voltage supplied.
[0053] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, component parts except the piezoelectric resonator are
constructed as one-chip IC.
[0054] In accordance with another exemplary embodiment of this
invention, in the temperature compensated oscillator described
above, the one-chip IC and the piezoelectric resonator are stored
in one package.
[0055] In accordance with another exemplary embodiment of this
invention, the temperature compensated oscillator described above
operates based on the output signal of the temperature compensated
oscillation circuit.
[0056] In accordance with another exemplary embodiment of this
invention, a method is provided for controlling a temperature
compensated oscillator that has a voltage controlled oscillation
circuit whose output signal oscillation frequency changes according
to the supplied voltage and a temperature compensation circuit that
outputs temperature compensation voltage for keeping the output
signal oscillation frequency constant based on temperature. The
method may include removing noise contained in the temperature
compensation voltage using a filter circuit, and controlling power
supply at least to the voltage controlled oscillation circuit and
the temperature compensation circuit, respectively, using a power
control circuit. The power control circuit turns on a switching
circuit connected in parallel with the filter circuit only for a
specified period when power supply to the voltage controlled
oscillation circuit is started.
[0057] In accordance with another exemplary embodiment of this
invention, the method for controlling a temperature compensated
oscillator described above includes switching between a first mode
where the output voltage follows the temperature compensation
voltage, and a second mode where the output voltage is maintained
at the temperature compensation voltage of the mode switching time,
using an output switching circuit between the temperature
compensation circuit and the filter circuit. The power control
circuit switches the output switching circuit to the first mode
when power supply to the temperature compensation circuit is
started, and switches the output switching circuit to the second
mode when power supply to the temperature compensation circuit is
stopped.
[0058] In accordance with another exemplary embodiment of this
invention, a method is provided for controlling a temperature
compensated oscillator that has a voltage controlled oscillation
circuit whose output signal oscillation frequency changes according
to the supplied voltage and a temperature compensation circuit that
outputs temperature compensation voltage for keeping the output
signal oscillation frequency constant based on temperature. The
method may include switching between a first mode where the output
voltage follows the temperature compensation voltage, and a second
mode where the output voltage is maintained at the temperature
compensation voltage of the mode switching time, using an output
switching circuit, removing noise contained in the temperature
compensation voltage output via the output switching circuit using
a filter circuit, and controlling power supply at least to the
voltage controlled oscillation circuit and the temperature
compensation circuit, respectively, using a power control circuit.
The power control circuit switches the output switching circuit to
the first mode when power supply to the temperature compensation
circuit is started, and to the second mode when power supply to the
temperature compensation circuit is stopped.
[0059] In accordance with another exemplary embodiment of this
invention, in the method for controlling a temperature compensated
oscillator described above, the power control circuit stops power
supply to circuits, except the output switching circuit, when power
supply to the voltage controlled oscillation circuit and the
temperature compensation circuit are stopped.
[0060] In accordance with another exemplary embodiment of this
invention, a method is provided for controlling a temperature
compensated oscillator that has a voltage controlled oscillation
circuit whose output signal oscillation frequency changes according
to supplied voltage, a temperature compensation circuit that
outputs temperature compensation voltage for keeping the output
signal oscillation frequency constant based on temperature, a
voltage control circuit that outputs frequency control voltage for
making the output signal oscillation frequency the frequency to be
set based on the externally supplied frequency control signal, and
an adder that outputs the temperature compensation voltage and the
frequency control voltage added together. The method may include
removing noise contained in the temperature compensation voltage
using a first filter circuit, removing noise contained in the
frequency control voltage using a second filter circuit, and
controlling power supply to the voltage controlled oscillation
circuit and the temperature compensation circuit, respectively,
using a power control circuit. The power control circuit turns on a
switching circuit connected in parallel with the first filter
circuit for a specified period when power supply to the voltage
controlled oscillation circuit is started.
[0061] In accordance with another exemplary embodiment of this
invention, the method for controlling a temperature compensated
oscillator described above includes switching between a first mode
where the output voltage follows the temperature compensation
voltage, and a second mode where the output voltage is maintained
at the temperature compensation voltage of the mode switching time,
using an output switching circuit between the temperature
compensation circuit and the first filter circuit. The power
control circuit switches the output switching circuit to the first
mode when power supply to the temperature compensation circuit is
started, and to the second mode when power supply to the
temperature compensation circuit is stopped.
[0062] In accordance with another exemplary embodiment of this
invention, a method is provided for controlling a temperature
compensated oscillator that has a voltage controlled oscillation
circuit whose output signal oscillation frequency changes according
to supplied voltage, a temperature compensation circuit that
outputs temperature compensation voltage for keeping the output
signal oscillation frequency constant based on temperature, a
voltage control circuit that outputs frequency control voltage for
making the output signal oscillation frequency the frequency to be
set based on externally supplied frequency control signal, and an
adder that outputs the temperature compensation voltage and the
frequency control voltage added together. The method may include
switching between a first mode where the output voltage follows the
temperature compensation voltage, and a second mode where the
output voltage is maintained at the temperature compensation
voltage of the mode switching time, using an output switching
circuit, removing noise contained in the temperature compensation
voltage output via the output switching circuit using a first
filter circuit, removing noise contained in the frequency control
voltage using a second filter circuit, and controlling power supply
at least to the voltage controlled oscillation circuit and the
temperature compensation circuit, respectively, using a power
control circuit. The power control circuit switches the output
switching circuit to the first mode when power supply to the
temperature compensation circuit is started, and to the second mode
when power supply to the temperature compensation circuit is
stopped.
[0063] In accordance with another exemplary embodiment of this
invention, in the method for controlling a temperature compensated
oscillator described above, the power control circuit stops power
supply to circuits, except the output switching circuit, when power
supply to the voltage controlled oscillation circuit and the
temperature compensation circuit are stopped.
[0064] In accordance with another exemplary embodiment of this
invention, in the method for controlling a temperature compensated
oscillator described above, the power control circuit controls
power supply to the voltage controlled oscillation circuit and the
temperature compensation circuit based on externally supplied
control signals.
BRIEF DESCRIPTION OF THE DRAWINGS
[0065] FIG. 1 is a block diagram of a temperature compensated
oscillator related to a first exemplary embodiment of this
invention.
[0066] FIG. 2 is a figure showing an example of construction of a
switch in the temperature compensated oscillator.
[0067] FIG. 3 is a property curve serving as an explanation of the
voltage conversion circuit in the temperature compensated
oscillator.
[0068] FIG. 4 is a circuit diagram of an example of the voltage
controlled oscillation circuit in the temperature compensated
oscillator.
[0069] FIG. 5 is a circuit diagram of an example of the voltage
controlled oscillation circuit in the temperature compensated
oscillator.
[0070] FIG. 6 is a timing chart of the temperature compensated
oscillator.
[0071] FIG. 7 is a block diagram of a temperature compensated
oscillator related to a second exemplary embodiment of the
invention.
[0072] FIG. 8 is a figure showing an example of construction of a
switch in the temperature compensated oscillator.
[0073] FIG. 9 is a block diagram of a temperature compensated
oscillator related to a third exemplary embodiment of the
invention.
[0074] FIG. 10 is a block diagram of a case where the temperature
compensated oscillator is applied to a portable wireless
communication device.
[0075] FIG. 11 is a timing chart of the temperature compensated
oscillator.
[0076] FIG. 12 is a block diagram of a temperature compensated
oscillator related to a fourth exemplary embodiment of the
invention.
[0077] FIG. 13 is an oblique view of a temperature compensated
oscillator related to a first modification example.
[0078] FIG. 14 is an oblique view of a temperature compensated
oscillator related to the first modification example.
[0079] FIG. 15 is a block diagram of a related analog temperature
compensated oscillator.
[0080] FIG. 16 is a block diagram of the digital temperature
compensated oscillator.
[0081] FIG. 17 is a frequency property curve of the filter circuit
(LPF).
[0082] FIG. 18 is a property curve of SSB phase noise of the output
signal of the temperature compensated oscillator.
[0083] FIG. 19 is a property curve of the oscillation starting time
of the output signal of the temperature compensated oscillator.
[0084] FIG. 20 is a block diagram of a VC-TCXO where a filter
circuit is inserted.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0085] Below, exemplary embodiments of this invention are explained
by referring to the drawings when appropriate.
[0086] (1) First Exemplary Embodiment
[0087] (1-1) Construction of the First Embodiment
[0088] Shown in FIG. 1 is a block diagram of a temperature
compensated oscillator related to a first exemplary embodiment of
this invention.
[0089] A temperature compensated oscillator 15 is constructed by
being equipped with a temperature compensation circuit 21, a filter
circuit 23, a switch SW1 connected in parallel to the filter
circuit 23, a voltage control circuit 25, a power control circuit
26, an adder 27, and a voltage controlled oscillation circuit
28.
[0090] Here, the temperature compensation circuit 21 can have a
construction that can output temperature compensation voltage Vc1
so that any change in frequency temperature property of a
piezoelectric resonator X is canceled. For example, the temperature
compensation circuit 21, described in the prior art technology, can
be constructed with a temperature sensor, an analog/digital
converter circuit, a memory, and a digital/analog converter
circuit. After converting temperature information into a digital
signal, it is converted to the data for temperature compensation
prerecorded in the memory, and it can be applied to a digital type
that outputs temperature compensation voltage Vc1 by converting the
data for temperature compensation from digital to analog, or to an
analog type that outputs temperature compensation voltage, Vc1 by
utilizing temperature properties of chips such as a thermistor.
[0091] The filter circuit (the first filter circuit) 23 is a
low-pass filter consisting of resistor elements and capacitors
(capacitance elements), or inductance elements and capacitors, and
removes the high-frequency component of the temperature
compensation voltage Vc1, namely noise contained in the temperature
compensation voltage Vc1.
[0092] Also because the switch SW1 is connected in parallel in this
filter circuit 23, when the switch SW1 is in an ON state, the
temperature compensation voltage Vc1 does not go through the filter
circuit 23. It is output via the switch SW1. FIG. 2 is a circuit
diagram of the switch SW1 surroundings when this switch SW1 is
composed of an analog switch.
[0093] The voltage control circuit 25 is a circuit, that a voltage
conversion circuit of the conventional VC-TCXO-type (13 shown in
FIG. 20), etc., can be applied to, and that generates the frequency
control voltage Vc2 based on the frequency control signal .phi.VC
supplied via the frequency control voltage input terminal VC.
[0094] For example, as the voltage control circuit 25, shown with
codes A, B, and C in FIG. 3, applied is a circuit where inclination
of the frequency control voltage Vc2 relative to the frequency
control signal .phi.VC is changed or polarity of change in the
frequency control voltage Vc2 is changed.
[0095] The adder 27 adds the temperature compensation voltage Vc1,
supplied via the filter circuit 23, and the frequency control
voltage Vc2, and outputs it to the voltage controlled oscillation
circuit 28.
[0096] The voltage controlled oscillation circuit 28 is composed of
an oscillation circuit 29 consisting of a buffer circuit and an
oscillation circuit that oscillates piezoelectric resonator X, such
as a quartz crystal resonator, a ceramic resonator, etc., and a
variable capacitance element Cv. The voltage controlled oscillation
circuit 28 applied is constructed using bipolar transistors Q1 and
Q2 shown in FIG. 4, or a CMOS-type where an inverter IV1 or IV2 is
composed of MOS-type transistors shown in FIG. 5.
[0097] The voltage controlled oscillation circuit 28 is controlled
so that the oscillation frequency of the output signal P remains
constant due to the temperature compensation voltage Vc1 even if
temperature changes. It is also controlled so that oscillation
frequency of the output signal P is to be set by the frequency
control voltage Vc2.
[0098] In FIG. 1 the voltage control circuit (power control
circuit) 26 is a circuit that controls power supply to the
temperature compensation circuit 21, the voltage control circuit
25, and the oscillation circuit 29, and controls power supply to
the individual circuits based on the standby control signal .phi.ST
supplied externally via the standby control terminal STBY. This
power control circuit 26 is provided with power from external power
source via the power terminals VCC and GND.
[0099] Here, the voltage control circuit 26 outputs an output
signal of desired oscillation frequency by having the temperature
compensation voltage Vc1 and the frequency control voltage Vc2
supplied to the voltage controlled oscillation circuit 28 when the
externally supplied standby control signal .phi.ST is at an H
level.
[0100] Also, the power control circuit 26 stops action of each
circuit when externally supplied standby control signal .phi.ST is
at the L level. Namely, by stopping power supply to the temperature
compensation circuit 21, the voltage control circuit 25 and the
oscillation circuit 29, power consumption of the temperature
compensated oscillator 15 can be reduced.
[0101] Furthermore, the power control circuit 26 changes the switch
SW1 to an ON state by setting the switch control signal .phi.S1 to
an H level for a short time, synchronizing it with increase of
externally supplied standby control signal .phi.ST.
[0102] Therefore, when the standby control signal .phi.ST becomes
the H level, the temperature compensation voltage Vc1 is output via
the switch SW1 without going through the filter circuit 23.
[0103] Because of this, when the standby control signal .phi.ST
becomes the H level, the temperature compensation voltage Vc1 is
supplied to the voltage controlled oscillation circuit 28 in a
short time by avoiding the delay time caused by going through the
filter circuit 23 that has a relatively large time constant.
[0104] (1-2) Actions of the First Embodiment
[0105] FIG. 6 is a timing chart of the temperature compensated
oscillator 15, and actions of the temperature compensated
oscillator 15 are explained by referring to this figure. Here, the
temperature compensated oscillator 15 is provided with power
voltage to the power terminal VCC from time T1 as shown in portion
(A), where the standby control signal .phi.ST is supplied to the
standby control terminal STBY as shown in portion (B).
[0106] First of all, if the standby control signal .phi.ST
increases to the H level at time T1, the power control circuit 26
starts to supply power voltage VREG to each circuit, and the
temperature compensation circuit 21, the voltage control circuit
25, the oscillation circuit 29, and the adder 27 start
operating.
[0107] Also, when the standby control signal .phi.ST becomes the H
level, as shown in portion (D), because the switching control
signal .phi.S1 increases to the H level for a short period in
synchronization with the increase of the standby control signal
.phi.ST, the temperature compensation circuit 21 is short-circuited
via the switch SW1.
[0108] Because of this, in the temperature compensated oscillator
15, the rise time of the temperature compensation voltage Vc1 can
be reduced compared with the case where the temperature
compensation voltage Vc1 is supplied via the filter circuit 23 to
the voltage controlled oscillation circuit 28, and the frequency
control of the output signal P, by the temperature compensation
voltage Vc1, can be started in a short time.
[0109] Also, once the power voltage VREG is supplied to the voltage
control circuit 25 at time T1, as shown in portion (C), the voltage
control circuit 25 outputs the frequency control voltage Vc2 based
on the frequency control signal .phi.VC, and by the frequency
control voltage Vc2 being supplied via the adder 27 to the voltage
controlled oscillation circuit 28, frequency control of the output
signal by the frequency control voltage Vc2 is started.
[0110] Next, as shown in portion (D), once the switch control
signal .phi.S1 reaches to the L level at time T2, because the
switch SW1 goes to the OFF position, the temperature compensation
voltage Vc1 is supplied via the filter circuit 23 to the voltage
controlled oscillation circuit 28.
[0111] Therefore, when the switch SW1 goes to the OFF position,
noise contained in the temperature compensation voltage Vc1 is
removed.
[0112] The temperature compensated oscillator 15 can reduce phase
noise of the output signal P by removing noise contained in the
temperature compensation voltage Vc1 using the filter circuit
23.
[0113] Next, once the standby control signal .phi.ST reaches the L
level at time T3 as shown in portion (B), supply of power voltage
VREG to each circuit by the power control circuit 26 is stopped as
shown in portion (C), and actions of the temperature compensation
circuit 21, the voltage control circuit 25, the oscillation circuit
29, and the adder 27 are stopped.
[0114] In this way, the temperature compensated oscillator 15 can
reduce power consumption by starting or stopping output of the
output signal P based on the standby control signal .phi.ST.
[0115] Here, if oscillation frequency of the output signal P, that
this temperature compensated oscillator 15 should output is denoted
as f0, the difference between the actual output oscillation
frequency and the supposed oscillation frequency f0 to be output is
denoted as df. The temperature compensated oscillator 15 can
stabilize the frequency of the output signal P to the desired
frequency f0 to be set within a short time once the standby control
signal .phi.ST increases.
[0116] Also, the temperature compensated oscillator 15, related to
this embodiment, connects the switch SW1 in parallel to the filter
circuit 23, and can stabilize oscillation frequency of the output
signal P to the desired frequency within a short time by setting
the switch SW1 to the ON position for a short time once the standby
control signal .phi.ST increases.
[0117] By these, the temperature compensated oscillator 15, related
to this embodiment, can reduce phase noise of the output signal and
also stabilize the output signal frequency within a short time.
[0118] By the way, when the inventors manufactured this temperature
compensated oscillator 15, a value of about -120 [dBc/Hz] could be
obtained at the offset frequency of 100 [Hz] as the phase noise
property.
[0119] (2) Second Exemplary Embodiment
[0120] (2-1) Construction of the Second Embodiment
[0121] Shown in FIG. 7 is a block diagram of a temperature
compensated oscillator related to a second exemplary embodiment of
this invention.
[0122] Because the temperature compensated oscillator 17 has the
same construction as the temperature compensated oscillator 15
related to the first embodiment, except for the point that a switch
SW1A is different, the same parts are indicated using the same
codes, and duplicate explanations are omitted.
[0123] In this temperature compensated oscillator 17, the switch
SW1A is a switch for switching the connection location of one end
of a capacitor C in the filter circuit 23 between the terminal A
connected to the temperature compensation circuit 21 side
(temperature compensation voltage input side) of the resistor
element R, and the adder 27 side (temperature compensation voltage
output side) of the resistor element R.
[0124] Also, this switch SW1A is constructed so that it connects
the capacitor C to the terminal A when the switch control signal
.phi.S1 is at the H level, and to the terminal B when the switch
control signal .phi.S1 is at the L level, where the application is
a construction in which an inverter is inserted between two analog
switches that become the ON position if an H-level signal is input,
etc., as shown in FIG. 8.
[0125] (2-2) Actions of the Second Embodiment
[0126] Next, actions of this temperature compensated oscillator 17
are explained. Here, because the timing chart of this temperature
compensated oscillator 17 is almost the same as the timing chart of
the temperature compensated oscillator 15, explanation is given to
the parts whose actions are different by using FIG. 6 as a
reference.
[0127] In this temperature compensated oscillator 17, once the
standby control signal .phi.ST reaches the H level at time T1 as
shown in portion (B), the switch control signal .phi.S1 reaches the
H level for a short period in synchronization with the stand-up of
the standby control signal .phi.ST as shown in portion (D), and the
connection located on one end of the capacitor C in the filter
circuit 23 switches from the terminal B to the terminal A only for
a short period.
[0128] Therefore, oscillation starting time delay due to recharging
of the capacitor C caused by the resistor R is reduced.
[0129] By this, in the temperature compensated oscillator 17, after
the connection location of one end of the capacitor C is switched
from the terminal A to the terminal B, delay of the temperature
compensation voltage Vc1 due to a relatively large time constant of
the filter circuit 23 can be reduced.
[0130] When the inventors manufactured the temperature compensated
oscillator 17, a value of about -121 [dBc/Hz] could be obtained at
the offset frequency of 100 [Hz] as the phase noise property.
[0131] (3) Third Exemplary Embodiment
[0132] (3-1) Construction of the Third Embodiment
[0133] Shown in FIG. 9 is a block diagram of a temperature
compensated oscillator related to a third exemplary embodiment of
this invention.
[0134] Because the temperature compensated oscillator 20 has the
same construction as the temperature compensated oscillator 15
related to the first embodiment, except for the point that a filter
circuit 24 is added, the same parts are indicated with the same
codes, and duplicated explanations are omitted.
[0135] A track & hold circuit (output switching circuit) 22
switches between the track mode (first mode) and the hold mode
(second mode) according to the mode control signal .phi.TH supplied
from the power control circuit 26, outputs the input voltage as it
is by passing through as the output voltage under the track mode,
and outputs by maintaining the input voltage at the time of mode
switch. In the case of the circuit shown in FIG. 1, the track &
hold circuit 22 switches to the track mode when the mode control
signal .phi.TH is at the H level, and to the hold mode when the
mode control signal .phi.TH is at the L level. This track &
hold circuit 22 may be constructed using a well-known circuit. As
the simplest basic construction, considered is a circuit
constructed using a switch circuit that changes to the ON position
when the mode control signal .phi.TH is at the H level, and a
capacitor that retains the output voltage when the switch circuit
changes to the OFF position.
[0136] The filter circuit (first filter circuit) 23 is a low-pass
filter consisting of resistor elements and capacitors (capacitor
elements), or inductance elements and capacitors, and it removes
the high-frequency component of the temperature compensation
voltage Vc1 output via the track & hold circuit 22. Namely,
when the track & hold circuit 22 is in the track mode, because
the output voltage is the temperature compensation voltage Vc1
output from the temperature compensation circuit 21, it removes
noise contained in the temperature compensation voltage Vc1.
[0137] Also, because the switch SW1 is connected in parallel to
this filter circuit 23, when the switch SW1 is in the ON position,
the temperature compensation voltage Vc1 output via the track &
hold circuit 22 is output via the switch SW1 without going through
the filter circuit 23.
[0138] As the voltage control circuit 25, the conventional VC-TCXO
voltage conversion circuit (13, shown in FIG. 20) etc. can be
applied, and it is a circuit that produces the frequency control
voltage Vc2 based on the frequency control signal .phi.VC supplied
via the frequency control voltage input terminal VC.
[0139] The filter circuit (second filter circuit) 24 is a low-pass
filter consisting of resistor elements and capacitance elements for
example, and removes the high-frequency component of the frequency
control voltage Vc2 supplied from the voltage control circuit 25.
Therefore, the filter circuit 24 removes noise contained in the
frequency control voltage Vc2 such as noise contained in the
frequency control signal .phi.VC supplied externally to the
frequency control voltage input terminal VC, noise inside the
voltage control circuit 25, etc.
[0140] Also, because the filter circuit 24 can remove noise
contained in the frequency control voltage Vc2, if the cut-off
frequency is set to the level of several 100 Hz to several kHz,
those with relatively small time constants are applied to.
[0141] On the other hand, the filter circuit 23 needs to set the
cut-off frequency to the level of several 10 Hz to several 100 Hz
for removing noise contained in the temperature compensation
voltage Vc1. Because of this, to this filter circuit 23 those with
lower cut-off frequency fc than those of filter circuit 24 are
applied.
[0142] In FIG. 9, the voltage control circuit (power control
circuit) 26 controls power supply to individual circuits based on
the standby control signal .phi.ST supplied externally via the
standby terminal STBY, and also switches the track & hold
circuit 22 to the track mode or the hold mode by outputting the
mode control signal .phi.TH based on the standby control signal
.phi.ST as stated above.
[0143] Namely, the power control circuit 26 supplies the power
voltage VREG to each circuit when the standby control signal
.phi.ST is at the H level, and also sets the mode control signal
.phi.TH to the H level to switch the track & hold circuit 22 to
the track mode.
[0144] On the other hand, the power control circuit 26 stops supply
of the power voltage VREG when the standby control signal .phi.ST
is at the L level, and also sets the mode control signal .phi.TH to
the L level to switch the track & hold circuit 22 to the hold
mode.
[0145] Therefore, the power control circuit 26 has the output
signal of desired oscillation frequency output by having the
temperature compensation voltage Vc1 and the frequency control
voltage Vc2 supplied to the voltage controlled oscillation circuit
28 when the externally supplied standby control signal .phi.ST is
at the H level.
[0146] Also, the power control circuit 26 stops actions of
individual circuits when the externally supplied standby control
signal .phi.ST is at the L level. Namely, by stopping power supply
to circuits, except the power control circuit 26 and the track
& hold circuit 22, power consumption of the temperature
compensated oscillator 20 can be reduced.
[0147] At this time, because the track & hold circuit 22 goes
into the hold mode, it maintains the output voltage at the
temperature compensation voltage Vc1 at the time of switching
modes. Because of this, once the externally supplied standby
control signal .phi.ST goes into the H level and it is switched to
the track mode, the track & hold circuit 22 can immediately
output the temperature compensation voltage Vc1 from the
temperature compensation circuit 21 without a delay.
[0148] Furthermore, the power control circuit 26 sets the switch
SW1 to the ON position for a short period by setting the switch
control signal .phi.S1 to the H level for a short period in
synchronization with the rise of the externally supplied standby
control signal .phi.ST.
[0149] Therefore, once the standby control signal .phi.ST goes into
the H level, the temperature compensation voltage Vc1 output via
the track & hold circuit 22 is output via the switch SW1
without going through the filter circuit 23.
[0150] Because of this, the standby control signal .phi.ST goes
into the H level, and the temperature compensation voltage Vc1 is
supplied to the voltage controlled oscillation circuit 28 within a
short time by avoiding a delay time caused by going through the
filter circuit 23 that has a relatively large time constant.
[0151] FIG. 10 is a block diagram of when this temperature
compensated oscillator 20 is applied to a portable wireless
communication device. This portable wireless communication device
30 is the same as the conventional portable wireless communication
device except that the temperature compensation oscillators are
different and the central processing computing circuit (CPU) 31
outputs the standby control signal .phi.ST to the standby control
terminal STBY of the temperature compensated oscillator 20.
[0152] Also, the shaded part in FIG. 10 is the part where an
intermittent operation is performed for reducing the standby power
consumption when waiting in this portable wireless communication
device 30.
[0153] Although this part for performing an intermittent operation
is the same as in the conventional portable wireless communication
device, this portable wireless communication device 30 can directly
control whether the temperature compensated oscillator 20 should be
driven according to the standby control signal .phi.ST.
[0154] The display/keyboard section 32 is always driven so that it
can always accept input by the user, and the synthesizer for
transmitter 33 and the sending filter/amplifier section 34 are
driven only when sending.
[0155] (3-2) Actions of the Third Embodiment
[0156] FIG. 11 is a timing chart of this temperature compensated
oscillator 20, and explanation is given on the actions of the
temperature compensated oscillator 20 by referring to this figure.
Here, the temperature compensated oscillator 20 is provided with
power voltage to the power terminal VCC from time T1 as shown in
portion (A), and assumed is a case where the standby control signal
.phi.ST is supplied to the standby control terminal STBY as shown
in portion (B).
[0157] First of all, once the standby control signal .phi.ST
reaches the H level at time T1, the power control circuit 26 starts
supplying power voltage VREG to each circuit as shown in portion
(C), and the temperature compensation circuit 21, the voltage
control circuit 25, the oscillation circuit 29, and the adder 27
start operating.
[0158] Also, once the standby control signal .phi.ST reaches the H
level, because the mode control signal .phi.TH reaches the H level
as shown in portion (D), the track & hold circuit 22 switches
to the track mode. By this, the temperature compensation voltage
Vc1 supplied from the temperature compensation circuit 21 can be
output at once without being delayed by the track & hold
circuit 22.
[0159] Furthermore, because the switching control signal .phi.S1
reaches the H level for a short period in synchronization with the
rise of the standby control signal .phi.ST, as shown in portion
(E), the track & hold circuit 22 is short-circuited via the
switch SW1.
[0160] Because of this, in the temperature compensated oscillator
20, initial voltage that can be supplied to the voltage controlled
oscillation circuit 28 can be set high relative to the case where
it goes through the filter circuit 23, and frequency control of the
output signal P by the temperature compensation voltage Vc1 can be
started within a short time.
[0161] Then, once the power voltage VREG is supplied to the voltage
control circuit 25 at time T1, the voltage control circuit 25
outputs the frequency control voltage Vc2 based on the frequency
control signal .phi.VC.
[0162] This frequency control voltage Vc2 has its noise removed by
the filter circuit 24, and is supplied to the voltage controlled
oscillation circuit 28 via the adder 27.
[0163] Here, as stated above, because the cut-off frequency fc of
this filter circuit 24 is set to a high value, the time constant is
set to a relatively small value, the frequency control voltage Vc2
is supplied to the voltage controlled oscillation circuit 28 with
almost no delay by the filter circuit 24.
[0164] Therefore, the temperature compensated oscillator 20 can
start frequency control of the output signal by the frequency
control voltage Vc2 within a short time without sacrificing
frequency control response to the change of the frequency control
voltage Vc2 even if noise of the frequency control voltage Vc2 is
removed using the filter circuit 24.
[0165] Next, as shown in portion (E), once the switching control
signal .phi.S1 becomes the L level at time T2, because the switch
SW1 goes to the OFF position, the temperature compensation voltage
Vc1 is supplied via the filter circuit 23 to the voltage controlled
oscillation circuit 28.
[0166] Therefore, when the switch SW1 goes to the OFF position,
noise contained in the temperature compensation voltage Vc1 is
removed.
[0167] By this, the temperature compensated oscillator 20 can
reduce phase noise of the output signal P by removing noise
contained in the temperature compensation voltage Vc1 and the
frequency control voltage Vc2 by the filter circuits 23 and 24,
respectively.
[0168] Once the standby control signal .phi.ST reaches the L level
at time T3 as shown in portion (B), supply of power voltage VREG by
the power control circuit 26 to each circuit is stopped, and the
temperature compensation circuit 21, the voltage control circuit
25, the oscillation circuit 29, and the adder 27 stop
operating.
[0169] In this way, the temperature compensated oscillator 20 can
reduce power consumption by starting or stopping output of the
output signal P based on the standby control signal .phi.ST.
[0170] Also, as shown in portion (D), because the mode control
signal .phi.TH reaches the L level at time T3, the track & hold
circuit 22 switches to the hold mode, and the output voltage of the
track & hold circuit 22 is maintained at the temperature
compensation voltage Vc1 of the mode switching time.
[0171] By this, when the standby control signal .phi.ST reaches the
H level again at T4, as shown in portion (B), the temperature
compensation voltage Vc1 supplied from the temperature compensation
circuit 21 can be output at once without a delay by the track &
hold circuit 22.
[0172] Here, if oscillation frequency of the output signal P that
this temperature compensated oscillator 20 should output is denoted
as f0, and the difference between the actual output oscillation
frequency and the supposed oscillation frequency f0 to be output is
denoted as df, as this frequency deviation is df/f0 a shown in
portion (G). The temperature compensated oscillator 20 can
stabilize frequency of the output signal P to the desired frequency
f0 to be set within a short time once the standby control signal
.phi.ST has increased.
[0173] Also, the temperature compensated oscillator 20 related to
this embodiment connects the switch SW1 in parallel to the filter
circuit 23, and can stabilize oscillation frequency of the output
signal P to the desired frequency within a short time by setting
the switch SW1 to the ON position for a short time once the standby
control signal .phi.ST has increased.
[0174] By these, the temperature compensated oscillator 20 related
to this embodiment can reduce phase noise of the output signal
further in addition to the efficacy of the embodiment by installing
the filter circuit 24, and also stabilizing the output signal
frequency within a short time by installing the track & hold
circuit 22.
[0175] (4) Fourth Exemplary Embodiment
[0176] Shown in FIG. 12 is a block diagram of a temperature
compensated oscillator related to a fourth exemplary embodiment of
this invention.
[0177] Because this temperature compensated oscillator 20A has the
same construction as the temperature compensated oscillator 20 in
the third embodiment, except for the point that the switch SW1A is
different, the same parts are indicated with the same codes
attached, and duplicated explanations are omitted.
[0178] Also, because the timing chart of this temperature
compensated oscillator 20A is almost the same as the timing chart
of the temperature compensated oscillator 20, parts where their
actions are different are explained using FIG. 11 as a
reference.
[0179] In this temperature compensated oscillator 20A, the switch
SW1A is a switch for switching the connection location of one end
of the capacitor C in the filter circuit 23 between the terminal A
connected to the track & hold circuit 22 side (temperature
compensation voltage input side) of the resistor element R and the
adder 27 side (temperature compensation output side) of the
resistor element R.
[0180] Therefore, in this temperature compensated oscillator 20A,
as shown in portion (E), when the switch control signal S1 reaches
the H level for a short period in synchronization with the rise of
the standby control signal .phi.ST, the connection location of one
end of the capacitor C in the filter circuit 23 switches from the
terminal B to the terminal A only for a short period, and
oscillation starting time delay due to recharging time of the
capacitor C caused by the resistor R is reduced.
[0181] By this, the temperature compensated oscillator 20A obtains
similar effects to that of the other embodiments.
[0182] (5) Modified Examples
[0183] (5-1) First Modified Example
[0184] Although no mention was made on the mounting condition of
the component parts consisting of the temperature compensated
oscillator in the above exemplary embodiments, because the
temperature compensated oscillator can remove noise contained in
the temperature compensation voltage Vc1 or the frequency control
voltage Vc2, elements and the like, composing the temperature
compensated oscillator can be integrated.
[0185] Therefore, component parts, excluding the piezoelectric
resonator X of the temperature compensated oscillator and the
capacitor C, which may consist of the filter circuit 23 (a section
surrounded with an alternate long and short dash line in FIG. 1,
FIG. 7, FIG. 9, and FIG. 12) and component parts, excluding only
the piezoelectric resonator X (a section surrounded with an
alternate long and short dash line including a variable capacity
element in FIG. 4 and FIG. 5), can be constructed as a one-chip IC,
for example. A temperature compensated oscillator with a ceramic
package sealed with a piezoelectric resonator X between itself and
the lid can be constructed as shown in FIG. 13. A temperature
compensated oscillator with a plastic package having a one-chip IC,
the piezoelectric resonator X, and the variable capacity element Cv
sealed by molding can be constructed as shown in FIG. 14.
[0186] Although a one-chip IC is connected to the board by wire
bonding in FIG. 13 and FIG. 14, it is needless to say that other
methods, such as flip chip bonding (FCB) can be applied. In the
same way, component elements such as reactance elements of the
filter circuit 23 or the filter circuit 24 can be mounted to the
capacitor C . Even if the capacitor C is mounted on the exterior of
the package in FIG. 13 and FIG. 14, efficacy of this invention does
not change.
[0187] By this, the temperature compensated oscillator can be
miniaturized, and the number of assembling process steps and
manufacturing cost can be reduced by reducing the number of
parts.
[0188] (5-2) Second Modification Example
[0189] Although this embodiment included a case where the filter
circuit 23 or 24 was constructed with a single-stage low-pass
filter, the invention is not limited to this, and it may be
constructed with a multiple-stage low-pass filter.
[0190] In this case, in the temperature compensated oscillators 17
and 20A related to the second embodiment or the fourth embodiment,
the connection locations of one end of all of the capacitors
contained in the multiple-stage low-pass filter may be switched by
the switch (SW1A) to the temperature compensation circuit side
relative to all of the resistors or inductance elements contained
in the multiple-stage low-pass filter at the start of
oscillation.
[0191] (5-3) Third Modification Example
[0192] Although this embodiment included a case where the invention
was applied to a temperature compensated oscillator that changes
the output signal oscillation frequency based on the frequency
control signal .phi.VC, the invention is not limited to this, and
it may be applied to a temperature compensated oscillator that is
not equipped with a frequency control voltage input terminal VC and
that maintains the output signal oscillation frequency constant
even if temperature changes.
[0193] In this case, the voltage control circuit 25, the filter
circuit 24, and the adder 27 may be removed from the temperature
compensated oscillator related to each embodiment. Also, in this
case, in the same way as the embodiment, phase noise of the output
signal can be reduced, and the output signal frequency can be
stabilized within a short time.
[0194] (5-4) Fourth Modification Example
[0195] Described in the embodiment was a case where this
temperature compensated oscillator was applied to a portable
wireless communication device, this invention is not limited to
this but can be widely applied to temperature compensated
oscillators used in other electronic equipment.
[0196] [Efficacy of the Invention]
[0197] As stated above, in the temperature compensated oscillator
of the invention, the switching circuit is connected in parallel to
the filter circuit with a large time constant so that the
temperature compensation voltage can be supplied to the voltage
controlled oscillation circuit without going through the filter
circuit when oscillation starts, phase noise of the output signal
can be reduced by recharging the capacitor in the filter circuit,
and also the output signal frequency can be stabilized within a
short time without deteriorating the control response.
* * * * *