U.S. patent application number 09/746896 was filed with the patent office on 2001-07-05 for voltage-controlled oscillator and electronic device using same.
Invention is credited to Goma, Shinji, Oshita, Teruaki.
Application Number | 20010006358 09/746896 |
Document ID | / |
Family ID | 26581609 |
Filed Date | 2001-07-05 |
United States Patent
Application |
20010006358 |
Kind Code |
A1 |
Oshita, Teruaki ; et
al. |
July 5, 2001 |
Voltage-controlled oscillator and electronic device using same
Abstract
A voltage-controlled oscillator has a frequency of oscillation
that is varied using a substrate on which the same circuit pattern
as that of the voltage-controlled oscillator is printed. In a
resonant circuit included in the voltage-controlled oscillator, a
first land is arranged substantially parallel to an inductor. A
second land is arranged substantially parallel to the inductor and
to a variable-capacitance diode. The capacitances of capacitors
attached to the first land and second land are changed in order to
vary the frequency of oscillation of the voltage-controlled
oscillator. The frequency of oscillation can be varied without the
necessity of scraping the inductor through which a major signal
passes. Therefore, electrical characteristics of the
voltage-controlled oscillator are not degraded and the frequency of
oscillation is very steady. The frequency of oscillation can be
varied merely by changing the capacitances of the capacitors
attached to the first and second lands. Consequently, a step of
scraping a strip line can be excluded, and manufacturing efficiency
can be improved.
Inventors: |
Oshita, Teruaki;
(Omihachiman-shi, JP) ; Goma, Shinji;
(Ishikawa-ken, JP) |
Correspondence
Address: |
Keating & Bennett LLP
Suite 312
10400 Eaton Place
Fairfax
VA
22030
US
|
Family ID: |
26581609 |
Appl. No.: |
09/746896 |
Filed: |
December 22, 2000 |
Current U.S.
Class: |
331/96 ;
331/117D; 331/117R; 331/167; 331/177V |
Current CPC
Class: |
H03B 5/1203 20130101;
H03B 5/1231 20130101; H03B 5/1243 20130101 |
Class at
Publication: |
331/96 ;
331/117.00R; 331/117.00D; 331/167; 331/177.00V |
International
Class: |
H03B 005/12; H03B
005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 1999 |
JP |
11-364756 |
Dec 5, 2000 |
JP |
2000-370250 |
Claims
What is claimed is:
1. A voltage-controlled oscillator comprising: a resonant circuit;
and an amplification circuit; wherein said resonant circuit
includes an inductor having a first terminal thereof connected to
said amplification circuit and a second terminal that is grounded
via a variable-capacitance diode, and a land to which a capacitor
is mounted; and said land has a first terminal connected to one of
the first and second terminals of said inductor and a second
terminal connected to the other of the first and second terminals
of said inductor.
2. The voltage controlled oscillator according to claim 1, further
comprising a plurality of inductors defined by strip lines and a
plurality of capacitors defined by chip capacitors.
3. The voltage controlled oscillator according to claim 1, wherein
the inductor includes at least one adjustment terminal.
4. A voltage-controlled oscillator according to claim 1, wherein a
transmission line element is interposed between said
variable-capacitance diode and a ground.
5. A voltage-controlled oscillator according to claim 4, wherein
said transmission line element has an adjustment terminal arranged
to change an impedance thereof by disconnecting from the
ground.
6. A voltage-controlled oscillator comprising: a resonant circuit;
and an amplification circuit, wherein said resonant circuit
includes an inductor having a first terminal connected to said
amplification circuit and a second terminal that is grounded via a
variable-capacitance diode, and a land to which a capacitor can be
mounted; and said land has a first terminal connected to one of the
first and second terminals of said inductor and a second terminal
that is grounded.
7. The voltage controlled oscillator according to claim 6, further
comprising a plurality of inductors defined by strip lines and a
plurality of capacitors defined by chip capacitors.
8. The voltage controlled oscillator according to claim 6, wherein
the inductor includes at least one adjustment terminal.
9. A voltage-controlled oscillator according to claim 6, wherein a
transmission line element is interposed between said
variable-capacitance diode and a ground.
10. A voltage-controlled oscillator according to claim 6, wherein
said transmission line element has an adjustment terminal arranged
to change an impedance thereof by disconnecting from the
ground.
11. A voltage-controlled oscillator according to claim 6, wherein a
transmission line element is interposed between said land and a
ground.
12. A voltage-controlled oscillator comprising: a resonant circuit;
and an amplification circuit; wherein said resonant circuit
includes an inductor having a first terminal connected to said
amplification circuit and a second terminal grounded via a
variable-capacitance diode, and first and second lands to which a
capacitor can be mounted; and said first land has a first terminal
thereof connected to one of the first and second terminals of said
inductor and a second terminal connected to the other of the first
and second terminals of said inductor, and said second land has a
first terminal thereof connected to one of the first and second
terminals of said inductor and a second terminal that is
grounded.
13. The voltage controlled oscillator according to claim 12,
further comprising a plurality of inductors defined by strip lines
and a plurality of capacitors defined by chip capacitors.
14. The voltage controlled oscillator according to claim 12,
wherein the inductor includes at least one adjustment terminal.
15. A voltage-controlled oscillator according to claim 12, wherein
a transmission line element is interposed between said second land
and a ground.
16. A voltage-controlled oscillator according to claim 12, wherein
a transmission line element is interposed between said
variable-capacitance diode and a ground.
17. A voltage-controlled oscillator according to claim 12, wherein
said transmission line element has an adjustment terminal arranged
to change an impedance thereof by disconnecting from the
ground.
18. A voltage-controlled oscillator according to claim 12, wherein
said transmission line element has an adjustment terminal arranged
to change an impedance thereof by disconnecting from the
ground.
19. An electronic device comprising at least one voltage-controlled
oscillator according to claim 1.
20. An electronic device comprising at least one voltage-controlled
oscillator according to claim 6.
21. An electronic device comprising at least one voltage-controlled
oscillator according to claim 12.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a voltage-controlled
oscillator and an electronic device incorporating a
voltage-controlled oscillator, or more particularly, the present
invention relates to a voltage-controlled oscillator adaptable to
communication devices and an electronic device incorporating the
voltage-controlled oscillator.
[0003] 2. Description of the Related Art
[0004] In recent years, a voltage-controlled oscillator having a
frequency of oscillation that can be varied diversely has been
demanded for use with various electronic devices including a
portable telephone. For providing the voltage-controlled oscillator
having a frequency of oscillation that can be varied diversely, a
new printed-circuit board may be designed for each frequency of
oscillation. However, this approach has enormous costs. According
to an alternative approach, an inductive component to be included
in a resonant circuit is realized with a strip line, the stripline
is scraped in order to vary the inductance of the inductive
component, and thus, the frequency of oscillation of a
voltage-controlled oscillator is varied.
[0005] Moreover, for designing a voltage-controlled oscillator,
simulation is often carried out using a computer. However, there is
an error between a theoretical value determined via simulation and
a measured value obtained using a prototype. A generally adopted
procedure for correcting the error is to scrape a strip line
included in the resonant circuit so as to change the inductance of
the inductive component.
[0006] Moreover, the work for adjusting electrical characteristics
such as a carrier-to-noise ratio includes scraping of the strip
line included in the resonant circuit.
[0007] FIG. 6 shows a conventional voltage-controlled oscillator.
Referring to FIG. 6, a voltage-controlled oscillator 3 consists
mainly of a resonant circuit 31 and an amplification circuit 12.
The resonant circuit 31 has one terminal of an inductor L1, which
is a strip line, connected to the amplification circuit 12 via a
capacitor C2. The other terminal of the inductor L1 is connected to
the cathode of a variable-capacitance diode VD1. The cathode of the
variable-capacitance diode VD1 is connected to a control voltage
terminal a2 via an inductor L3 that is a choke coil. The anode of
the variable-capacitance diode VD1 is grounded. The capacitor C2 is
a coupling capacitor.
[0008] The resonant circuit 31 is connected to the base of a
transistor Tr1 which functions as an amplification element in the
amplification circuit 12. The emitter of the transistor Tr1 is
connected to an output terminal a3 via a capacitor C7. The
collector of the transistor Tr1 is grounded via a capacitor C4. A
power terminal a4 is grounded via a capacitor C5, and connected to
the collector of the transistor Tr1 via an inductor L4 that is a
choke coil. The base and emitter of the transistor Tr1 are biased
by resistors R1, R2, and R3. A capacitor C3 is connected between
the base and emitter of the transistor Tr1.
[0009] In the thus-configured voltage-controlled oscillator 3, the
inductance of the inductor L1 is adjusted in order to vary the
frequency of oscillation of the voltage-controlled oscillator or
improve the electrical characteristics thereof such as a
carrier-to-noise ratio. The inductor L1 is a circuit element
enabling variation of the frequency of oscillation and greatly
contributing to the electric characteristic such as the
carrier-to-noise ratio.
[0010] Moreover, in the thus-configured voltage-controlled
oscillator 3, the variable-capacitance diode VD1 and inductor L1
are connected in series with each other to thus realize a series
resonant circuit suitable for expanding a frequency band within
which the frequency of oscillation can be varied. The series
resonant circuit has a property that when the frequency band within
which the frequency of oscillation is variable is larger than 10%
of the frequency of oscillation, a loss caused by the resonant
circuit 31 hardly depends on the frequency of oscillation.
[0011] In the voltage-controlled oscillator 3, the inductor L1
included in the resonant circuit 31 having the series resonant
circuit and realized with a strip line is scraped using a laser in
order to vary the frequency of oscillation of the
voltage-controlled oscillator and to improve the electrical
characteristics thereof such as a carrier-to-noise ratio.
[0012] However, since a major signal passes through the inductor
L1, when the inductor L1 must be adjusted, quite delicate and very
accurate adjustment is required. This poses a problem in that
manufacturing efficiency is degraded. Moreover, since the major
signal passes through the inductor L1, when the inductor L1 is
adjusted, the electrical characteristics of the voltage-controlled
oscillator 3 is likely to be degraded or the frequency of
oscillation thereof is likely to be unstable. Moreover, the step of
scraping the inductor L1 is needed for every product. This degrades
the manufacturing efficiency. These problems become more serious
when the frequency band within which the frequency of oscillation
is variable is wider.
SUMMARY OF THE INVENTION
[0013] In order to overcome the problems described above, preferred
embodiments of the present invention provide a voltage-controlled
oscillator having a frequency of oscillation that is readily varied
and an electrical characteristic thereof such as a carrier-to-noise
ratio readily improved even when a frequency band within which the
frequency of oscillation is variable is wide.
[0014] Other preferred embodiments of the present invention provide
a voltage-controlled oscillator having a frequency of oscillation
can be varied greatly without the necessity of scraping a strip
line.
[0015] Further preferred embodiments of the present invention
provide a voltage-controlled oscillator having an electric
characteristic thereof that is not degraded and a frequency of
oscillation thereof that is stable even when a strip line is
scraped in order to adjust part of a resonant circuit for the
purpose of varying the frequency of oscillation or improving the
electrical characteristics thereof such as a carrier-to-noise
ratio.
[0016] According to one preferred embodiment of the present
invention, a voltage-controlled oscillator includes a resonant
circuit and an amplification circuit. The resonant circuit includes
an inductor having one terminal that is connected to the
amplification circuit and another terminal that is grounded via a
variable-capacitance diode, and a land to which a capacitor can be
mounted. The first land has one terminal thereof connected to one
terminal of the inductor and the other terminal thereof connected
to the other terminal of the inductor.
[0017] Moreover, according to other preferred embodiments of the
present invention, a voltage-controlled oscillator includes a
resonant circuit and an amplification circuit. The resonant circuit
includes an inductor having one terminal that is connected to the
amplification circuit and another terminal that is grounded via a
variable-capacitance diode, and a land to which a capacitor can be
mounted. The land has one terminal thereof connected to one
terminal of the inductor and the other terminal thereof
grounded.
[0018] Moreover, according to other preferred embodiments of the
present invention, a voltage-controlled oscillator includes a
resonant circuit and an amplification circuit. The resonant circuit
includes an inductor having one terminal that is connected to the
amplification circuit and another terminal that is grounded via a
variable-capacitance diode, and first and second lands to which a
capacitor can be mounted. The first land has one terminal thereof
connected to one terminal of the inductor and the other terminal
thereof connected to the other terminal of the inductor. The second
land has one terminal thereof connected to one terminal of the
inductor and the other terminal thereof grounded.
[0019] Moreover, according to other preferred embodiments of the
present invention, a voltage-controlled oscillator has a
transmission line element interposed between the land and a ground
terminal.
[0020] Moreover, according to other preferred embodiments of the
present invention, a voltage-controlled oscillator has a
transmission line element interposed between the
variable-capacitance diode and a ground.
[0021] Moreover, according to other preferred embodiments of the
present invention, in a voltage-controlled oscillator, the
transmission line element has an adjustment terminal to change an
impedance of the transmission line element by disconnecting from
the ground terminal.
[0022] Moreover, according to other preferred embodiments of the
present invention, an electronic device includes the
voltage-controlled oscillators according to other preferred
embodiments of the present invention.
[0023] As a result of the unique features of preferred embodiments
of the present invention, a voltage-controlled oscillator in
accordance with preferred embodiments of the present invention has
its frequency of oscillation varied without the necessity of
scraping an inductor through which a major signal passes.
Therefore, the electrical characteristics of the voltage-controlled
oscillator will hardly be deteriorated and the frequency of
oscillation thereof will hardly be unstable.
[0024] Moreover, in a voltage-controlled oscillator in accordance
with preferred embodiments of the present invention it is not
necessary to scrape an inductor through which a major signal passes
for the purpose of varying the frequency of oscillation thereof or
improving a carrier-to-noise ratio thereof. Therefore, a chip coil
exhibiting a high Q factor may be adopted as the inductor. In this
case, the electrical characteristics of the voltage-controlled
oscillator such as the carrier-to-noise ratio can be improved.
[0025] Moreover, the frequency of oscillation of a
voltage-controlled oscillator in accordance with preferred
embodiments of the present invention can be varied greatly by
changing the capacitances of discrete capacitors mounted to the
first and second lands. It is not necessary to scrape a strip line.
Otherwise it is possible to reduce an amount by which the strip
line is scraped. Consequently, manufacturing efficiency
improves.
[0026] Moreover, a magnitude by which the frequency of oscillation
of a voltage-controlled oscillator in accordance with preferred
embodiments of the present invention or the electrical
characteristics thereof such as a carrier-to-noise ratio can be
adjusted varies depending on what portion of a transmission line
element is cut. By selecting a proper portion of the transmission
line, the frequency of oscillation or the electrical
characteristics such as a carrier-to-noise ratio can be adjusted
properly.
[0027] Moreover, a resonant circuit of a voltage-controlled
oscillator in accordance with other preferred embodiments of the
present invention includes first and second lands and a
transmission line element defining circuit elements used to adjust
the frequency of oscillation of the voltage-controlled oscillator
or the electrical characteristics thereof such as a
carrier-to-noise ratio. The first and second lands enable
adjustment by a large magnitude. The line element enables
adjustment by a small magnitude. These increase the freedom of
design. Consequently, the frequency of oscillation or the
electrical characteristics such as a carrier-to-noise ratio can be
adjusted readily.
[0028] Moreover, a communication device in accordance with a
preferred embodiment of the present invention incorporates a
voltage-controlled oscillator in accordance with other preferred
embodiments of the present invention that prevents degradation of
electrical characteristics and has a very reliable frequency of
oscillation. The communication device is therefore regarded as an
electronic device achieving excellent output characteristics.
[0029] Other features, elements, characteristics and advantages of
the present invention will become apparent from the detailed
description of preferred embodiments thereof with reference to the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a circuit diagram showing a preferred embodiment
of a voltage-controlled oscillator in accordance with the present
invention;
[0031] FIG. 2A and FIG. 2B are plan views of another preferred
embodiment of the voltage-controlled oscillator in accordance with
the present invention;
[0032] FIG. 3 is an enlarged view of a line element included in the
voltage-controlled oscillator shown in FIG. 2;
[0033] FIG. 4A and FIG. 4B are circuit diagrams showing a resonant
circuit included in still another preferred embodiment of the
voltage-controlled oscillator in accordance with the present
invention;
[0034] FIG. 5 is a block diagram showing a preferred embodiment of
an electronic device in accordance with the present invention;
and
[0035] FIG. 6 is a circuit diagram showing a conventional
voltage-controlled oscillator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] FIG. 1 shows a preferred embodiment of a voltage-controlled
oscillator in accordance with the present invention. In FIG. 1, the
same reference numerals are assigned to components identical or
equivalent to those shown in FIG. 6. The description of these
similar components will be omitted.
[0037] Referring to FIG. 1, a resonant circuit 11 included in a
voltage-controlled oscillator 1 has, in addition to the same
components as the resonant circuit 31, a first land Land1, a second
land Land2, a capacitor C1a, a capacitor C1b, and inductors L2a and
L2b that are transmission line elements. The first land Land1 and
second land Land2 are pairs of electrode patterns to which chip
components are mounted. The capacitor C1a is mounted to the first
land Land1, and the capacitor C1b is mounted to the second land
Land2. One terminal of the inductor L1 is connected to one terminal
of the first land Land1 and one terminal of the second land Land2,
and also connected to an amplification circuit 12 via the capacitor
C2. The other terminal of the inductor L1 is connected to the
cathode of the variable-capacitance diode VD1 and to the other
terminal of the first land Land1, and also connected to the control
voltage terminal a2 via the inductor L3. The anode of the
variable-capacitance diode VD1 is grounded via the inductor L2b.
The other terminal of the second land Land2 is grounded via the
inductor L2b. The inductors L2a and L2b are preferably defined by
strip lines, and the capacitors C1a and C1b are preferably defined
by chip capacitors.
[0038] Referring to FIG. 2A and FIG. 2B, a method of switching a
voltage-controlled oscillator 1a of which oscillation frequency is
1.8 GHz, into a voltage-controlled oscillator 1a' of which
oscillation frequency is 3 GHz will be described in accordance with
various preferred embodiments of the present invention. FIG. 2A is
a plan view of the voltage-controlled oscillator 1a having a
frequency of oscillation that is 1.8 GHz, and FIG. 2B is a plan
view of the voltage-controlled oscillator 1a' having a frequency of
oscillation that is 3 GHz. In FIG. 2A and FIG. 2B, the same
reference numerals are assigned to identical or equivalent
components. The description of the components will be not
repeated.
[0039] The voltage-controlled oscillators 1a and 1a' shown in FIG.
2A and FIG. 2B include resonant circuits 11a and 11a' respectively
that do not include the first land Land1, capacitor C1a, and
inductor L2a included in the resonant circuit 11 shown in FIG. 1.
Circuit wirings, the second land Land2, and the inductors L1 and
L2b that are strip lines are printed on a substrate 13 of each of
the voltage-controlled oscillators 1a and 1a'. The capacitors C1b
or C1b' and C2, variable-capacitance diode VD1, inductor L3, and
amplification circuit 12 are mounted on the substrate 13.
[0040] The first and second steps described below are followed
orderly, whereby the voltage-controlled oscillator la having a
frequency of oscillation that is 1.8 GHz can be switched to the
voltage-controlled oscillator 1a' having a frequency of oscillation
that is 3 GHz.
[0041] To begin with, the first step is a step of removing the
capacitor C1b from the second land Land2. At this time, since the
capacitor C1b is constituted of a chip capacitor, the capacitor C1b
can be removed readily. If the frequency of oscillation of the
voltage-controlled oscillator la becomes 3 GHz when the capacitor
C1b is removed, the step described below need not be performed.
[0042] The second step is a step of mounting the capacitor C1b', of
which capacitance is different from that of the capacitor C1b, to
the second land Land2. The capacitances of the capacitors C1b and
Cb1' may be determined so that once the capacitor C1b is replaced
with the capacitor C1b', the frequency of oscillation of the
voltage-controlled oscillator 1a is changed from 1.8 GHz to 3 GHz.
This would greatly improve manufacturing efficiency.
[0043] In the voltage-controlled oscillator 1a, capacitance of the
capacitor C1b as well as the inductor L1 greatly contributes to
switching of the oscillation frequency. When the capacitance of the
capacitor C1b is changed to a proper capacitance with the property
of the inductor L1 remaining original, the frequency of oscillation
can be changed.
[0044] In other words, in preferred embodiments of the present
invention, as apparent from the comparison of the
voltage-controlled oscillator 1i a with the voltage-controlled
oscillator 1a', the frequency of oscillation of a
voltage-controlled oscillator can be varied diversely by simply
mounting a chip capacitor having a proper capacitance to the second
land Land2 on the same substrate on which a circuit pattern is
printed.
[0045] The method of changing the frequency of oscillation of the
voltage-controlled oscillator 1a from one frequency to another has
been described. The advantages of preferred embodiments of the
present invention are not related to varying the frequency of
oscillation. The advantages of preferred embodiments of the present
invention relate to the frequency of oscillation of a
voltage-controlled oscillator being varied diversely depending on
whether or not the capacitors C1a and C1b are mounted to the first
land Land1 and second land Land2 or whatever capacitance a
capacitor mounted has.
[0046] As shown in FIG. 2A and FIG. 2B, each of the
voltage-controlled oscillators 1a and 1a' includes the inductor L2b
that is a strip line. A major signal does not pass through the
inductor L2b. Further, the inductor L2b has a relatively negligible
affect on the frequency of oscillation of the voltage-controlled
oscillator or the electrical characteristics thereof such as a
carrier-to-noise ratio. After changing the oscillation frequency,
if necessary, the oscillation frequency or the electrical
characteristics such as a carrier-to-noise ratio can be adjusted
finely by scraping the inductor L2b using a laser or other suitable
means in the voltage-controlled oscillator 1a and the
voltage-controlled oscillator 1a'.
[0047] FIG. 3 is an enlarged view of the inductor L2b. A method of
finely adjusting the voltage-controlled oscillator 1a' will be
described below. Assume that the frequency of oscillation of the
voltage-controlled oscillator 1a' including the inductor L2b shown
in FIG. 3 is 3 GHz. In this case, if the inductor L2b is cut along
near a dot-dash line x1, the frequency of oscillation is lowered by
approximately 80 MHz. If the inductor L2b is cut along near a
dot-dash line x2, the frequency of oscillation is lowered by
approximately 20 MHz. If the inductor L2b is cut along near a
dot-dash line x3, the frequency of oscillation is lowered by
approximately 2 MHz. Thus, the frequency of oscillation can be
varied by a desired value depending what portion of the inductor
L2b is cut.
[0048] Moreover, the inductor L2b shown in FIG. 3 has an adjustment
terminal g1 and an adjustment terminal g2 that are grounded. An
impedance of the inductor L2b may be adjusted by disconnecting one
of the adjustment terminals g1 and g2 from a ground. The inductor
L2b shown in FIG. 3 may be cut along a dot-dash line x4 in order to
adjust the frequency of oscillation.
[0049] Compared with a case in which the inductor L2b is cut along
the dot-dash line x1, x2, or x3, when the inductor L2b is cut along
the dot-dash line x4 or the adjustment terminal g1 or g2 is
disconnected, the frequency of oscillation or the electrical
characteristics such as a carrier-to-noise ratio can be varied
within a large range. Moreover, these portions of the inductor to
be cut may be combined, whereby freedom in designing is further
increased. Consequently, a pattern space may not be widened but
adjustment of the frequency of oscillation and improvement of the
electrical characteristics such as the carrier-to-noise ratio can
be achieved easily.
[0050] Using the voltage-controlled oscillators 1a and 1a' shown in
FIG. 2A and FIG. 2B, it has been described that the frequency of
oscillation of the voltage-controlled oscillator 1a is varied by
replacing the capacitor C1b attached to the second land Land2 with
the capacitor C1b'. Even the frequency of oscillation of the
voltage-controlled oscillator 1 shown in FIG. 1 can be varied by
replacing the capacitors C1a and C1b attached to the first land
Land1 and second land Land2 with others in the same manner as that
mentioned above or by breaking the inductors L2a and L2b in the
same manner as that mentioned above.
[0051] FIG. 4A and FIG. 4B show a resonant circuit included in
still another preferred embodiment of the voltage-controlled
oscillator in accordance with the present invention. In FIG. 4A and
FIG. 4B, the same reference numerals are assigned to components
identical to those shown in FIG. 1. The description of the
components will be omitted.
[0052] Referring to FIG. 4A, a resonant circuit 11b preferably has
the same circuit elements as the resonant circuit 11 shown in FIG.
1 but does not include the inductor L2a and inductor L2b.
[0053] The resonant circuit 11b does not include the inductor L2a
and inductor L2b that are strip lines. The capacitors C1a and C1b
attached to the first land Land1 and second land Land2 are replaced
with others, whereby the frequency of oscillation of the
voltage-controlled oscillator can be altered. Even when one of the
inductors L2a and L2b is removed, the same operations and
advantages will be obtained.
[0054] Referring to FIG. 4B, a resonant circuit 11c has a
configuration excluding the second land Land2 and capacitor C1b
shown in FIG. 4A. Thus, even when the first land Land1 and
capacitor C1a alone are provided, the frequency of oscillation of
the voltage-controlled oscillator can be varied. FIG. 4B may have
the same circuit elements as removing the second land Land2 and
capacitor C1b or only the capacitor C1b from the resonant circuit
11b shown in FIG. 4A. Even when the capacitor C1a instead of the
capacitor C1b is removed from the resonant circuit 11b shown in
FIG. 4A, the same operations and advantages with the resonant
circuit shown in FIG. 4B are obtained.
[0055] The voltage-controlled oscillator in accordance with
preferred embodiments of the present invention is not limited to
the circuit elements incorporated in the above-described preferred
embodiment to constitute a resonant circuit, amplification circuit,
and a transmission line element. Alternatively, a microstrip line
may be adopted as an inductor or a transmission line element.
[0056] FIG. 5 is a block diagram showing a communication device
that is another preferred embodiment of an electronic device in
accordance with the present invention. Referring to FIG. 5, a
communication device 2 includes a signal processing circuit 21,
bandpass filters 22, 26, 30, and 34, amplifiers 23, 27, 31, and 35,
mixers 25 and 33, a duplexer 28, an antenna 29, and
voltage-controlled oscillators 1b and 1c. Herein, an output
terminal of the signal processing circuit 21 is connected to the
mixer 25 via the bandpass filter 22 and amplifier 23 that are
connected in series with each other. An output terminal of the
voltage-controlled oscillator 1b is connected to the mixer 25. An
output terminal of the mixer 25 is connected to the duplexer 28
connected to the antenna 29 via the bandpass filter 26 and
amplifier 27 that are connected in series with each other. The
duplexer 28 is connected to the mixer 33 via the bandpass filter 30
and amplifier 31 that are connected in series with each other. An
output terminal of the voltage-controlled oscillator 1c is
connected to the mixer 33. An output terminal of the mixer 33 is
connected to the signal processing circuit 21 via the bandpass
filter 34 and amplifier 35 that are connected in series with each
other.
[0057] In the communication device 2, for signal transmission, an
output signal of the signal processing circuit 21 has its
unnecessary components removed by the bandpass filter 22. The
resultant signal is amplified by the amplifier 23, and mixed with a
signal output from the voltage-controlled oscillator 1b by the
mixer 25. The signal is thus frequency-converted into a
radio-frequency signal. The radio-frequency signal has its
unnecessary components removed by the bandpass filter 26. The
resultant signal is amplified by the amplifier 27, and radiated
through the antenna 29 via the duplexer 28. For signal reception, a
radio-frequency signal received through the antenna 29 is input to
the bandpass filter 30 via the duplexer 28. The radio-frequency
signal has its unnecessary components removed by the bandpass
filter 30. The resultant signal is amplified by the amplifier 31,
and mixed with a signal output from the voltage-controlled
oscillator 1c by the mixer 33. The signal is thus
frequency-converted into an intermediate-frequency signal. The
intermediate-frequency signal has its unnecessary components
removed by the bandpass filter 34. The resultant signal is
amplified by the amplifier 35 and input to the signal processing
circuit 21. Transmission and reception of a signal are thus carried
out.
[0058] The thus-configured communication device 2 is realized as an
electronic device achieving an excellent output capability owing to
the inclusion of the voltage-controlled oscillators 1b and 1c each
of which has electrical characteristics that are not degraded and a
very steady frequency of oscillation.
[0059] The communication device 2 has been used as an example in
order to describe an electronic device including a
voltage-controlled oscillator in accordance with a preferred
embodiment of the present invention. The electronic device in
accordance with preferred embodiments of the present invention is
not limited to the communication device having the above-described
configuration.
[0060] According to preferred embodiments of the present invention,
the frequency of oscillation of a voltage-controlled oscillator can
be varied without the necessity of scraping an inductor through
which a major signal passes. Therefore, electrical characteristics
of the voltage-controlled oscillator are not degraded and the
frequency of oscillation thereof is very steady.
[0061] According to preferred embodiments of the present invention,
it is unnecessary to scrape an inductor, through which a major
signal passes, for the purpose of varying the frequency of
oscillation of a voltage-controlled oscillator or improving a
carrier-to-noise ratio thereof. A chip coil exhibiting a high Q
factor can be adopted as the inductor. In this case, the electrical
characteristics such as the carrier-to-noise ratio can be
improved.
[0062] Moreover, according to preferred embodiments of the present
invention, the frequency of oscillation of a voltage-controlled
oscillator can be varied greatly by changing the capacitances of
capacitors attached to first and second lands. This obviates the
necessity of scraping a strip line. Otherwise, the magnitude of
scraping can be reduced. Consequently, manufacturing efficiency is
greatly improved.
[0063] Moreover, according to preferred embodiments of the present
invention, a magnitude of adjustment of the frequency of
oscillation of a voltage-controlled oscillator or electrical
characteristics such as a carrier-to-noise ratio thereof varies
depending on what portion of a line element is cut. Consequently,
the frequency of oscillation and the electrical characteristics
such as the carrier-to-noise ratio can be adjusted readily by
selecting a proper portion of the line element.
[0064] Moreover, according to preferred embodiments of the present
invention, a resonant circuit included in a voltage-controlled
oscillator includes first and second lands and a line element as
circuit elements used to adjust the frequency of oscillation of the
voltage-controlled oscillator or an electric characteristic thereof
such as a carrier-to-noise ratio. The first and second lands enable
adjustment by a large magnitude, while the line element enables
adjustment by a minute magnitude. Consequently, freedom in
designing expands, and the frequency of oscillation or the
electrical characteristics such as the carrier-to-noise ratio can
be adjusted readily.
[0065] Moreover, according to preferred embodiments of the present
invention, a communication device includes a voltage-controlled
oscillator in accordance with other preferred embodiments of the
present invention that has electrical characteristics that are not
degraded and a frequency of oscillation that is very steady. The
communication device is therefore provided as an electric device
achieving an excellent output capability.
[0066] While preferred embodiments of the invention have been
disclosed, various modes of carrying out the principles disclosed
herein are contemplated as being within the scope of the following
claims. Therefore, it is understood that the scope of the invention
is not to be limited except as otherwise set forth in the
claims.
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