U.S. patent application number 16/440352 was filed with the patent office on 2019-09-26 for high-frequency front end circuit.
The applicant listed for this patent is Murata Manufacturing Co., Ltd.. Invention is credited to Isao TAKENAKA.
Application Number | 20190296694 16/440352 |
Document ID | / |
Family ID | 64272607 |
Filed Date | 2019-09-26 |
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United States Patent
Application |
20190296694 |
Kind Code |
A1 |
TAKENAKA; Isao |
September 26, 2019 |
HIGH-FREQUENCY FRONT END CIRCUIT
Abstract
A high-frequency front end circuit includes an antenna terminal,
a reception circuit that is directly or indirectly connected to the
antenna terminal, and a transmission circuit that is directly or
indirectly connected to the antenna terminal, wherein the
transmission circuit has an amplification circuit, the
amplification circuit includes an input terminal and an output
terminal, an amplification element provided on a path connecting
the input terminal and the output terminal, and a bias circuit
having an LC resonance circuit and connected to between the
amplification element and the output terminal. A frequency pass
band of the transmission circuit is lower than a frequency pass
band of the reception circuit, and a value of a resonant frequency
of the bias circuit is smaller than a value of a frequency pass
band width of the transmission circuit.
Inventors: |
TAKENAKA; Isao; (Kyoto,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Murata Manufacturing Co., Ltd. |
Kyoto |
|
JP |
|
|
Family ID: |
64272607 |
Appl. No.: |
16/440352 |
Filed: |
June 13, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15978823 |
May 14, 2018 |
10367455 |
|
|
16440352 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 1/0458 20130101;
H03F 2200/165 20130101; H03F 2200/222 20130101; H04B 1/40 20130101;
H03F 3/19 20130101; H03F 1/56 20130101; H03F 3/195 20130101; H03F
3/245 20130101; H04B 1/18 20130101; H03F 1/26 20130101; H03F
2200/171 20130101; H03F 2200/387 20130101; H03F 2200/255 20130101;
H03F 2200/318 20130101; H03F 2200/451 20130101 |
International
Class: |
H03F 1/26 20060101
H03F001/26; H03F 1/56 20060101 H03F001/56; H03F 3/24 20060101
H03F003/24; H04B 1/04 20060101 H04B001/04; H04B 1/18 20060101
H04B001/18; H04B 1/40 20060101 H04B001/40; H03F 3/19 20060101
H03F003/19; H03F 3/195 20060101 H03F003/195 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2017 |
JP |
2017-097220 |
Claims
1. A high-frequency front end circuit comprising: an antenna
terminal; a reception circuit that is connected to the antenna
terminal; and a transmission circuit that is connected to the
antenna terminal and that comprises a first amplification circuit,
wherein the first amplification circuit comprises: an input
terminal and an output terminal; an amplification element connected
in a signal path between the input terminal and the output
terminal; and a bias circuit comprising an LC resonance circuit, a
first end of the bias circuit being connected to the signal path,
wherein a frequency pass band of the transmission circuit is higher
than a frequency pass band of the reception circuit, and wherein a
resonant frequency of the bias circuit is greater than a frequency
pass band width of the transmission circuit.
2. The high-frequency front end circuit according to claim 1,
wherein the first end of the bias circuit is connected to the
signal path between the amplification element and the output
terminal.
3. The high-frequency front end circuit according to claim 2,
further comprising an output matching circuit in the signal path
between the amplification element and the output terminal, wherein
the first end of the bias circuit is connected to the signal path
between the amplification element and the output matching
circuit.
4. The high-frequency front end circuit according to claim 1,
wherein the transmission circuit further comprises at least one
additional amplification circuit, the first amplification circuit
and the at least one additional amplification circuit being
connected in a multistage arrangement, wherein the first
amplification circuit is the closest amplification circuit to the
antenna terminal.
5. The high-frequency front end circuit according to claim 1,
comprising a plurality of the first amplification circuits
connected in a multistage arrangement.
6. The high-frequency front end circuit according to claim 1,
wherein the first end of the bias circuit is connected to the
signal path between the input terminal and the amplification
element.
Description
[0001] This is a division of U.S. application Ser. No. 15/978,823,
filed May 14, 2018, which claims priority from Japanese Patent
Application No. 2017-097220 filed on May 16, 2017. The content of
these applications are incorporated herein by reference in their
entireties.
BACKGROUND
[0002] The present disclosure relates to a high-frequency front end
circuit including a reception circuit and a transmission circuit
having an amplification circuit. A high-frequency front end circuit
including a reception circuit and a transmission circuit is
provided in a communication apparatus such as a cellular phone. As
an example of the transmission circuit of the high-frequency front
end circuit of this type, Japanese Unexamined Patent Application
Publication No. 2014-116844 discloses a transmission circuit having
a plurality of power amplification circuits. The transmission
circuit amplifies transmission signals having different frequency
bands by the power amplification circuits corresponding to the
respective transmission signals and outputs the transmission
signals.
[0003] However, in the case in which the transmission circuit
disclosed in Japanese Unexamined Patent Application Publication No.
2014-116844 is connected to a reception circuit with an antenna
terminal interposed therebetween, for example, when a frequency
band of the reception circuit is present so as to be adjacent to a
frequency band of the transmission circuit, there is a problem that
distortion components generated in the power amplification circuits
of the transmission circuit leak to the side of the frequency band
of the reception circuit, and frequency characteristics of the
reception circuit are deteriorated.
BRIEF SUMMARY
[0004] Accordingly, the present disclosure suppresses leakage of a
distortion component generated in a power amplification circuit of
a transmission circuit to the side of a frequency band of a
reception circuit in a high-frequency front end circuit in which
the transmission circuit and the reception circuit are connected to
an antenna terminal.
[0005] According to an embodiment of the present disclosure, a
high-frequency front end circuit includes an antenna terminal, a
reception circuit that is directly or indirectly connected to the
antenna terminal, and a transmission circuit that is directly or
indirectly connected to the antenna terminal, wherein the
transmission circuit has an amplification circuit, the
amplification circuit includes an input terminal and an output
terminal, an amplification element provided on a path connecting
the input terminal and the output terminal, and a bias circuit
having an LC resonance circuit and connected to at least one of
between the amplification element and the output terminal and
between the input terminal and the amplification element, a
frequency pass band of the transmission circuit is lower than a
frequency pass band of the reception circuit, and a value of a
resonant frequency of the bias circuit is smaller than a value of a
frequency pass band width of the transmission circuit.
[0006] This configuration can cancel odd-numbered order
intermodulation distortion which is generated at the high frequency
side of a transmission signal. Therefore, generation of leakage
power at the high frequency side of the transmission signal, that
is, the side of the frequency band of the reception circuit can be
suppressed.
[0007] According to another embodiment of the present disclosure, a
high-frequency front end circuit includes an antenna terminal, a
reception circuit that is directly or indirectly connected to the
antenna terminal, and a transmission circuit that is directly or
indirectly connected to the antenna terminal, wherein the
transmission circuit has an amplification circuit, the
amplification circuit includes an input terminal and an output
terminal, an amplification element provided on a path connecting
the input terminal and the output terminal, and a bias circuit
having an LC resonance circuit and connected to at least one of
between the amplification element and the output terminal and
between the input terminal and the amplification element, a
frequency pass band of the transmission circuit is higher than a
frequency pass band of the reception circuit, and a value of a
resonant frequency of the bias circuit is larger than a value of a
frequency pass band width of the transmission circuit.
[0008] This configuration can cancel odd-numbered order
intermodulation distortion which is generated at the low frequency
side of a transmission signal. Therefore, generation of leakage
power at the low frequency side of the transmission signal, that
is, the side of the frequency band of the reception circuit can be
suppressed.
[0009] The bias circuit may be connected to between the
amplification element and the output terminal.
[0010] With this configuration, the bias circuit can be made to act
on a signal that is output from the amplification circuit, and
generation of leakage power at the side of the frequency band of
the reception circuit can be suppressed efficiently.
[0011] Furthermore, the high-frequency front end circuit may
further include an output matching circuit on a path connecting the
amplification element and the output terminal, wherein the bias
circuit is connected to between the amplification element and the
output matching circuit.
[0012] With this configuration, a signal output from the
amplification circuit can be output in a state of matching with a
circuit or an element of an output destination.
[0013] According to still another embodiment of the present
disclosure, a high-frequency front end circuit includes a reception
circuit and a transmission circuit having a plurality of
amplification circuits connected in multistage, wherein the
amplification circuit that is the closest to an output side of the
transmission circuit among the plurality of amplification circuits
is the amplification circuit according to any one of the
above-described paragraphs.
[0014] With this configuration, the bias circuit can be made to act
on a signal that is output from the amplification circuit located
at the most posterior side among the plurality of amplification
circuits, and generation of leakage power at the side of the
frequency band of the reception circuit can be suppressed
efficiently.
[0015] Furthermore, each of the plurality of amplification circuits
may be the amplification circuit according to any one of the
above-described paragraphs.
[0016] Provision of the bias circuit in each of the amplification
circuits as described above can increase control factors for
suppressing generation of leakage power, thereby suppressing
generation of the leakage power with high accuracy.
[0017] Other features, elements, characteristics and advantages of
the present disclosure will become more apparent from the following
detailed description of embodiments of the present disclosure with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0018] FIG. 1 is a schematic diagram illustrating an output signal
spectrum of a transmission circuit of a high-frequency front end
circuit in a comparative example;
[0019] FIG. 2 is a functional block diagram of a high-frequency
front end circuit according to a first embodiment;
[0020] FIG. 3 is a circuit configuration diagram of an
amplification circuit included in a transmission circuit of the
high-frequency front end circuit according to the first
embodiment;
[0021] FIG. 4 is a schematic diagram illustrating impedance
characteristics of a bias circuit included in the amplification
circuit in the first embodiment;
[0022] FIG. 5 is a schematic diagram illustrating an output signal
spectrum of the transmission circuit in the first embodiment;
[0023] FIG. 6 is a functional block diagram of a high-frequency
front end circuit according to a second embodiment;
[0024] FIG. 7 is a circuit configuration diagram of an
amplification circuit included in a transmission circuit of the
high-frequency front end circuit according to the second
embodiment;
[0025] FIG. 8 is a schematic diagram illustrating impedance
characteristics of a bias circuit included in the amplification
circuit in the second embodiment;
[0026] FIG. 9 is a schematic diagram illustrating an output signal
spectrum of the transmission circuit in the second embodiment;
[0027] FIG. 10 is a functional block diagram of a high-frequency
front end circuit according to a third embodiment;
[0028] FIG. 11 is a circuit configuration diagram of an
amplification circuit in a fourth embodiment; and
[0029] FIG. 12 is a circuit configuration diagram of an
amplification circuit in another mode.
DETAILED DESCRIPTION
[0030] First, description is made using, as an example, a
high-frequency front end circuit in a comparative example.
[0031] The high-frequency front end circuit in the comparative
example includes a reception circuit and a transmission circuit
having an amplification circuit (not illustrated). In the
high-frequency front end circuit in the comparative example, a
frequency pass band of the transmission circuit is set to be at a
lower frequency side relative to a frequency pass band of the
reception circuit.
[0032] FIG. 1 is a schematic diagram illustrating an output signal
spectrum of the transmission circuit of the high-frequency front
end circuit in the comparative example. FIG. 1 indicates an output
signal of the transmission circuit having a frequency pass band
width .DELTA.f when the amplification circuit amplifies a
modulation signal.
[0033] In general, an output signal spectrum of a transmission
circuit is set such that the high frequency side and the low
frequency side are symmetric to each other with respect to a
transmission signal frequency pass band, as illustrated in FIG. 1.
However, input and output characteristics of the amplification
circuit in the transmission circuit has nonlinearity. As electric
power that is used in the transmission circuit is increased,
non-linear distortion is generated and leakage power to the outside
of the frequency pass band is generated. For this reason, when a
reception signal frequency band is adjacent to a transmission
signal frequency band, for example, there is a problem that the
above-described leakage power enters the reception signal frequency
band and reception quality of a reception circuit is
deteriorated.
[0034] To cope with this problem, in a high-frequency front end
circuit according to an embodiment of the present disclosure, an
output signal spectrum of a transmission circuit is set such that
the high frequency side and the low frequency side are asymmetric
to each other with respect to a transmission signal frequency pass
band. The output signal spectrum is made asymmetric by, for
example, decreasing electric power at the high frequency side at
the outside of the transmission signal frequency pass band (see
FIG. 5). This asymmetric output signal spectrum can decrease
leakage power entering a reception signal frequency band which is
present at the high frequency side and suppress deterioration in
reception quality. Hereinafter, the configuration for making the
output signal spectrum of the transmission circuit be asymmetric
will be described.
[0035] Hereinafter, embodiments of the present disclosure will be
described in detail with reference to the embodiments and the
drawings. It should be noted that all the embodiments which will be
described below indicate comprehensive or specific examples.
Numerical values, shapes, materials, components, arrangement and
connection forms of the components, and the like which will be
described in the following embodiments are examples and are not
intended to limit the present disclosure. Components that are not
described in the independent claims of the disclosure among the
components in the following embodiments are described as arbitrary
components. The sizes or size ratios of the components illustrated
in the drawings are not necessarily strict.
First Embodiment
[0036] A high-frequency front end circuit 1 according to a first
embodiment is a circuit for transmitting and receiving
high-frequency signals (signals of approximately 700 MHz to 2700
MHz) in accordance with the long term evolution (LTE) standard, for
example.
[0037] FIG. 2 is a functional block diagram of the high-frequency
front end circuit 1. FIG. 2 illustrates a communication apparatus
100 and an antenna element 2.
[0038] The communication apparatus 100 includes the high-frequency
front end circuit 1, an RF signal processing circuit (RFIC) 3, and
a baseband signal processing circuit (BBIC) 4. The high-frequency
front end circuit 1 is arranged in, for example, a front end
portion of a cellular phone.
[0039] The high-frequency front end circuit 1 includes a
transmission circuit 30a having an amplification circuit 10a and a
transmission filter 20, and a reception circuit 70a having a low
noise amplifier circuit 50 and a reception filter 60.
[0040] Both of the transmission circuit 30a and the reception
circuit 70a are electrically connected to an antenna terminal Pant.
In the embodiment, the transmission circuit 30a and the reception
circuit 70a are directly connected to the antenna terminal
Pant.
[0041] In the embodiment, a frequency pass band of the transmission
circuit 30a is set to be lower than a frequency pass band of the
reception circuit 70a. For example, the frequency pass band of the
transmission circuit 30a is equal to or higher than approximately
704 MHz and equal to or lower than approximately 716 MHz and the
frequency pass band of the reception circuit 70a is equal to or
higher than approximately 734 MHz and equal to or lower than
approximately 746 MHz.
[0042] The amplification circuit 10a configures a power amplifier
that amplifies a high-frequency transmission signal output from the
RF signal processing circuit 3 and outputs the amplified
high-frequency transmission signal to the transmission filter 20.
The amplification circuit 10a is a primary part of the present
disclosure and details thereof will be described later.
[0043] The transmission filter 20 is a transmission filter element
that filters the transmission signal output from the amplification
circuit 10a by a predetermined pass band and outputs the
transmission signal to the antenna element 2 with the antenna
terminal Pant interposed therebetween. The transmission filter 20
is, for example, a surface acoustic wave (SAW) filter.
[0044] The reception filter 60 is a reception filter element that
inputs a reception signal received by the antenna element 2 with
the antenna terminal Pant interposed therebetween, filters the
reception signal by a predetermined pass band, and outputs it to
the low noise amplifier circuit 50. The reception filter 60 is, for
example, an SAW filter.
[0045] The low noise amplifier circuit 50 configures a low noise
amplifier that amplifies a high-frequency reception signal output
from the reception filter 60 and outputs the amplified
high-frequency reception signal to the RF signal processing circuit
3.
[0046] The RF signal processing circuit 3 is, for example, a radio
frequency integrated circuit (RFIC). The RF signal processing
circuit 3 performs signal processing on a transmission signal input
from the baseband signal processing circuit 4 by up conversion or
the like, and outputs a high-frequency transmission signal
generated by the signal processing to the amplification circuit
10a. Furthermore, the RF signal processing circuit 3 performs
signal processing on a high-frequency reception signal input from
the antenna element 2 while passing through a reception-side signal
path by down conversion or the like, and outputs a reception signal
generated by the signal processing to the baseband signal
processing circuit 4.
[0047] The baseband signal processing circuit 4 is a circuit that
performs signal processing using an intermediate frequency band
that is lower than the frequency of the high-frequency signal in
the high-frequency front end circuit 1.
[0048] FIG. 3 is a circuit configuration diagram of the
amplification circuit 10a included in the transmission circuit 30a
of the high-frequency front end circuit 1.
[0049] The amplification circuit 10a has an input terminal Pin, an
input matching circuit 14, an amplification element Tr, a bias
circuit 13a, an output matching circuit 15, and an output terminal
Pout.
[0050] The amplification element Tr is provided on a path
connecting the input terminal Pin and the output terminal Pout. The
amplification element Tr is a power amplification element that
amplifies the transmission signal input from the input terminal Pin
side and outputs the amplified transmission signal to the output
terminal Pout side, and is, for example, a heterobipolar transistor
or an electric field effect transistor.
[0051] The input matching circuit 14 is provided on a path
connecting the input terminal Pin and the amplification element Tr.
The input matching circuit 14 is a circuit that matches impedance
at the RF signal processing circuit 3 side and impedance at the
amplification element Tr side, and has, for example, a capacitor
and an inductor.
[0052] The output matching circuit 15 is provided on a path
connecting the amplification element Tr and the output terminal
Pout. The output matching circuit 15 is a circuit that matches
impedance at the amplification element Tr side and impedance at the
transmission filter 20 side, and has, for example, a capacitor and
an inductor.
[0053] The bias circuit 13a is a circuit that is connected to a
connection point cp located between the amplification element Tr
and the output matching circuit 15 and supplies a bias voltage to
the amplification element Tr. The bias circuit 13a has an LC
resonance circuit LC1 configured by series connection of an
inductor L1 and a capacitor C1. The inductor L1 of the LC resonance
circuit LC1 is connected to the connection point cp, the capacitor
C1 is connected to the ground, and a power supply voltage Vcc is
supplied to between the inductor L1 and the capacitor C1.
[0054] FIG. 4 is a schematic diagram illustrating impedance
characteristics of the bias circuit 13a included in the
amplification circuit 10a. FIG. 5 is a schematic diagram
illustrating an output signal spectrum of the transmission circuit
30a. In FIGS. 4 and 5, a transmission signal frequency pass band
width .DELTA.f is .DELTA.f=f.sub.2-f.sub.1 (f.sub.1<f.sub.2).
Hereinafter, the frequency pass band width .DELTA.f is referred to
as a band width .DELTA.f.
[0055] A resonant frequency fr of the bias circuit 13a having the
LC resonance circuit LC1 is expressed by fr=1/(2.pi. LC).
Therefore, as illustrated in FIG. 4, the impedance of the bias
circuit 13a is minimum at the resonant frequency fr and is inclined
upward to the right toward the higher frequency side relative to
the resonant frequency fr.
[0056] In the embodiment, a value of the resonant frequency fr of
the bias circuit 13a is set to be smaller than a value of the band
width .DELTA.f of the transmission circuit 30a. In other words, the
value of the band width .DELTA.f is larger than the value of the
resonant frequency fr and the impedance of the bias circuit 13a is
a large value in a state in which an inductor component is
dominant. The above-described impedance setting in the bias circuit
13a can superimpose an even-numbered order distortion component
which is generated at the low frequency side (for example,
f.sub.2-f.sub.1) at the outside of the transmission signal
frequency pass band on odd-numbered order intermodulation
distortion which is generated at the high frequency side of the
transmission signal (for example, 2f.sub.2-f.sub.1) in an opposite
phase. Usage of the distortion component cancels the odd-numbered
order intermodulation distortion of the transmission signal and
leakage power which is generated at the high frequency side of the
transmission signal can be suppressed, as illustrated in FIG.
5.
[0057] For example, when the value of the resonant frequency fr and
the value of the band width .DELTA.f are set to be the same, the
output signal spectrum becomes symmetric as illustrated in FIG. 1
and the leakage power which is generated at the high frequency side
of the transmission signal is increased. By contrast, when the
value of the resonant frequency fr is set to be smaller than the
value of the band width .DELTA.f as in the embodiment, the
odd-numbered order intermodulation distortion at the high frequency
side of the transmission signal is canceled and the output signal
spectrum becomes asymmetric. This asymmetric output signal spectrum
can suppress the leakage power which is generated in the reception
signal frequency band present at the high frequency side of the
transmission signal.
[0058] That is to say, the high-frequency front end circuit 1 in
the embodiment includes the reception circuit 70a and the
transmission circuit 30a having the amplification circuit 10a,
wherein the amplification circuit 10a includes the input terminal
Pin and the output terminal Pout, the amplification element Tr
provided on the path connecting the input terminal Pin and the
output terminal Pout, and the bias circuit 13a having the LC
resonance circuit LC1 and connected to between the amplification
element Tr and the output terminal Pout. The frequency pass band of
the transmission circuit 30a is lower than the frequency pass band
of the reception circuit 70a and the value of the resonant
frequency fr of the bias circuit 13a is smaller than the value of
the band width .DELTA.f of the transmission circuit 30a.
[0059] The high-frequency front end circuit 1 has the
above-described configuration, so that the odd-numbered order
intermodulation distortion which is generated at the high frequency
side of the transmission signal can be canceled using the
even-numbered order distortion component which is generated at the
low frequency side at the outside of the transmission signal
frequency pass band. Therefore, generation of the leakage power at
the high frequency side of the transmission signal, that is, the
side of the frequency band of the reception circuit can be
suppressed.
Second Embodiment
[0060] In a high-frequency front end circuit 1A according to a
second embodiment, a reception signal frequency band is set to be
present at the lower frequency side relative to a transmission
signal frequency band.
[0061] FIG. 6 is a functional block diagram of the high-frequency
front end circuit 1A. FIG. 6 illustrates the communication
apparatus 100 and the antenna element 2.
[0062] The communication apparatus 100 includes the high-frequency
front end circuit 1A, the RF signal processing circuit (RFIC) 3,
and the baseband signal processing circuit (BBIC) 4. The
high-frequency front end circuit 1A is arranged in, for example, a
front end portion of a cellular phone.
[0063] The high-frequency front end circuit 1A includes a
transmission circuit 30b having an amplification circuit 10b and
the transmission filter 20, and a reception circuit 70b having the
low noise amplifier circuit 50 and the reception filter 60.
[0064] Both of the transmission circuit 30b and the reception
circuit 70b are electrically connected to the antenna terminal
Pant. In the embodiment, the transmission circuit 30b and the
reception circuit 70b are directly connected to the antenna
terminal Pant.
[0065] In the embodiment, a frequency pass band of the transmission
circuit 30b is set to be higher than a frequency pass band of the
reception circuit 70b. To be specific, in the high-frequency front
end circuit 1A, a reception signal frequency band is set to be
present at the lower frequency side relative to a transmission
signal frequency band so as to be adjacent thereto.
[0066] The amplification circuit 10b configures a power
amplification circuit that amplifies a high-frequency transmission
signal output from the RF signal processing circuit 3 and outputs
the amplified high-frequency transmission signal to the
transmission filter 20.
[0067] The transmission filter 20 is a transmission filter element
that filters a transmission signal output from the amplification
circuit 10b in a predetermined pass band and outputs the
transmission signal to the antenna element 2 with the antenna
terminal Pant interposed therebetween.
[0068] The reception filter 60 is a reception filter element that
inputs a reception signal received by the antenna element 2 with
the antenna terminal Pant interposed therebetween, filters the
reception signal in a predetermined pass band, and outputs it to
the low noise amplifier circuit 50.
[0069] The low noise amplifier circuit 50 is a high-frequency
amplification circuit that amplifies a high-frequency reception
signal output from the reception filter 60 and outputs the
amplified high-frequency reception signal to the RF signal
processing circuit 3.
[0070] The RF signal processing circuit 3 performs signal
processing on a transmission signal input from the baseband signal
processing circuit 4 by up conversion or the like, and outputs a
high-frequency transmission signal generated by the signal
processing to the amplification circuit 10b. The RF signal
processing circuit 3 performs signal processing on a high-frequency
reception signal input from the antenna element 2 while passing
through a reception-side signal path by down conversion or the
like, and outputs a reception signal generated by the signal
processing to the baseband signal processing circuit 4.
[0071] The baseband signal processing circuit 4 is a circuit that
performs signal processing using an intermediate frequency band
that is lower than the frequency of the high-frequency signal in
the high-frequency front end circuit 1A.
[0072] FIG. 7 is a circuit configuration diagram of the
amplification circuit 10b included in the transmission circuit 30b
of the high-frequency front end circuit 1A.
[0073] The amplification circuit 10b has the input terminal Pin,
the input matching circuit 14, the amplification element Tr, a bias
circuit 13b, the output matching circuit 15, and the output
terminal Pout.
[0074] The amplification element Tr is provided on a path
connecting the input terminal Pin and the output terminal Pout. The
amplification element Tr is a power amplification element that
amplifies the transmission signal input from the input terminal Pin
side and outputs the amplified transmission signal to the output
terminal Pout side.
[0075] The input matching circuit 14 is provided on a path
connecting the input terminal Pin and the amplification element Tr.
The input matching circuit 14 is a circuit that matches impedance
at the RF signal processing circuit 3 side and impedance at the
amplification element Tr side.
[0076] The output matching circuit 15 is provided on a path
connecting the amplification element Tr and the output terminal
Pout. The output matching circuit 15 is a circuit that matches
impedance at the amplification element Tr side and impedance at the
transmission filter 20 side.
[0077] The bias circuit 13b is a circuit that is connected to the
connection point cp located between the amplification element Tr
and the output matching circuit 15 and supplies a bias voltage to
the amplification element Tr. The bias circuit 13b has an LC
resonance circuit LC2 configured by series connection of an
inductor L2 and a capacitor C2. The inductor L2 of the LC resonance
circuit LC2 is connected to the connection point cp, the capacitor
C2 is connected to the ground, and the power supply voltage Vcc is
supplied to between the inductor L2 and the capacitor C2.
[0078] FIG. 8 is a schematic diagram illustrating impedance
characteristics of the bias circuit 13b included in the
amplification circuit 10b. FIG. 9 is a schematic diagram
illustrating an output signal spectrum of the transmission circuit
30b. In FIGS. 8 and 9, a transmission signal band width .DELTA.f is
.DELTA.f=f.sub.2-f.sub.1 (f.sub.1<f.sub.2).
[0079] A resonant frequency fr of the bias circuit 13b having the
LC resonance circuit LC2 is expressed by fr=1/(2.pi./LC).
Therefore, as illustrated in FIG. 8, the impedance of the bias
circuit 13b is minimum at the resonant frequency fr and is inclined
upward to the left toward the lower frequency side relative to the
resonant frequency fr.
[0080] In the embodiment, a value of the resonant frequency fr of
the bias circuit 13b is set to be larger than a value of the band
width .DELTA.f of the transmission circuit 30b. In other words, the
value of the band width .DELTA.f is smaller than the value of the
resonant frequency fr and the impedance of the bias circuit 13b is
a large value in a state in which a capacitor component is
dominant. The above-described impedance setting in the bias circuit
13b can superimpose an even-numbered order distortion component
which is generated at the low frequency side (for example,
f.sub.2-f.sub.1) at the outside of the transmission signal
frequency pass band on odd-numbered order intermodulation
distortion which is generated at the low frequency side of the
transmission signal (for example, 2f.sub.2-f.sub.1) in an opposite
phase. Usage of the distortion component cancels the odd-numbered
order intermodulation distortion at the low frequency side of the
transmission signal and leakage power which is generated at the low
frequency side of the transmission signal can be suppressed, as
illustrated in FIG. 9.
[0081] For example, when the value of the resonant frequency fr and
the value of the band width .DELTA.f are set to be the same, the
output signal spectrum becomes symmetric as illustrated in FIG. 1
and the leakage power which is generated at the low frequency side
of the transmission signal is increased. By contrast, when the
value of the resonant frequency fr is set to be larger than the
value of the band width .DELTA.f as in the embodiment, the
odd-numbered order intermodulation distortion which is generated at
the low frequency side of the transmission signal is canceled and
the output signal spectrum becomes asymmetric. This asymmetric
output signal spectrum can suppress the leakage power which is
generated in the reception signal frequency band present at the low
frequency side of the transmission signal.
[0082] That is to say, the high-frequency front end circuit 1A in
the embodiment includes the reception circuit 70b and the
transmission circuit 30b having the amplification circuit 10b,
wherein the amplification circuit 10b includes the input terminal
Pin and the output terminal Pout, the amplification element Tr
provided on the path connecting the input terminal Pin and the
output terminal Pout, and the bias circuit 13b having the LC
resonance circuit LC2 and connected to between the amplification
element Tr and the output terminal Pout. The frequency pass band of
the transmission circuit 30b is higher than the frequency pass band
of the reception circuit 70b and the value of the resonant
frequency fr of the bias circuit 13b is larger than the value of
the band width .DELTA.f of the transmission circuit 30b.
[0083] The high-frequency front end circuit 1A has the
above-described configuration, so that the odd-numbered order
intermodulation distortion which is generated at the low frequency
side of the transmission signal can be canceled using the
even-numbered order distortion component which is generated at the
low frequency side at the outside of the transmission signal
frequency pass band. Therefore, generation of the leakage power at
the low frequency side of the transmission signal, that is, the
side of the frequency band of the reception circuit can be
suppressed.
Third Embodiment
[0084] A high-frequency front end circuit 1B according to a third
embodiment has the circuit configuration of the high-frequency
front end circuit 1 in the first embodiment and the circuit
configuration of the high-frequency front end circuit 1A in the
second embodiment, and is configured so as to be used in
multiband.
[0085] FIG. 10 is a functional block diagram of the high-frequency
front end circuit 1B.
[0086] The high-frequency front end circuit 1B includes the
transmission circuit 30a and the reception circuit 70a in the first
embodiment and the transmission circuit 30b and the reception
circuit 70b in the second embodiment.
[0087] The transmission circuit 30a and the reception circuit 70a
are indirectly connected to the antenna terminal Pant with a switch
SW2 interposed therebetween. The transmission circuit 30b and the
reception circuit 70b are indirectly connected to the antenna
terminal Pant with the switch SW2 interposed therebetween.
[0088] In the third embodiment, a frequency pass band of the
transmission circuit 30a is set to be lower than a frequency pass
band of the reception circuit 70a, and a frequency pass band of the
transmission circuit 30b is set to be higher than a frequency pass
band of the reception circuit 70b.
[0089] The high-frequency front end circuit 1B includes a switch
SW1 and the switch SW2. The switch SW1 is provided on a path
connecting the amplification circuit 10a of the transmission
circuit 30a and the transmission filter 20 and on a path connecting
the amplification circuit 10b of the transmission circuit 30b and
the transmission filter 20. The switch SW2 is provided on a path
connecting a duplexer configured by the transmission filter 20 of
the transmission circuit 30a and the reception filter 60 of the
reception circuit 70a and the antenna terminal Pant and on a path
connecting a duplexer configured by the transmission filter 20 of
the transmission circuit 30b and the reception filter 60 of the
reception circuit 70b and the antenna terminal Pant.
[0090] Either one of the transmission circuit 30a and the reception
circuit 70a and the transmission circuit 30b and the reception
circuit 70b is selected by switching the switch SW2 and the switch
SW1. Both of the selected transmission circuit and the selected
reception circuit are electrically connected to the antenna
terminal Pant. Furthermore, the selected transmission circuit and
the selected reception circuit are used as band processing circuits
in the high-frequency front end circuit 1B. The switching is
performed based on a control signal from a control IC mounted on
the high-frequency front end circuit 1B, for example.
[0091] In the embodiment, the frequency pass band of the
transmission circuit 30a is lower than the frequency pass band of
the reception circuit 70a and the value of the resonant frequency
fr of the bias circuit 13a of the amplification circuit 10a is
smaller than the value of the band width .DELTA.f of the
transmission circuit 30a. Therefore, when the transmission circuit
30a and the reception circuit 70a are selected with the switches
SW1 and SW2, generation of leakage power at the high frequency side
relative to the transmission signal frequency band can be
suppressed.
[0092] Furthermore, in the embodiment, the frequency pass band of
the transmission circuit 30b is higher than the frequency pass band
of the reception circuit 70b and the value of the resonant
frequency fr of the bias circuit 13b of the amplification circuit
10b is larger than the value of the band width .DELTA.f of the
transmission circuit 30b. Therefore, when the transmission circuit
30b and the reception circuit 70b are selected with the switches
SW1 and SW2, generation of leakage power at the low frequency side
relative to the transmission signal frequency band can be
suppressed.
Fourth Embodiment
[0093] In a high-frequency front end circuit 1 according to a
fourth embodiment, an amplification circuit 10A is configured by
amplification circuits in multistage.
[0094] FIG. 11 is a circuit configuration diagram of the
amplification circuit 10A in the fourth embodiment.
[0095] The amplification circuit 10A has the amplification circuit
10a and an amplification circuit 10c connected in multistage. The
amplification circuit 10c is located at a posterior stage relative
to the amplification circuit 10a.
[0096] The amplification circuit 10c has the input terminal Pin,
the input matching circuit 14, the amplification element Tr, a bias
circuit 13c, the output matching circuit 15, and the output
terminal Pout. The input terminal Pin of the amplification circuit
10c is connected to the output terminal Pout of the amplification
circuit 10a located at an anterior stage. The output terminal Pout
of the amplification circuit 10c is connected to the transmission
filter 20. The output matching circuit 15 of the amplification
circuit 10a and the input matching circuit 14 of the amplification
circuit 10c may be integrated in either of them to form a matching
circuit.
[0097] The bias circuit 13c is a circuit that is connected to the
connection point cp located between the amplification element Tr
and the output matching circuit 15 and supplies a bias voltage to
the amplification element Tr. The bias circuit 13c has an LC
resonance circuit LC3 configured by series connection of an
inductor L3 and a capacitor C3. The inductor L3 of the LC resonance
circuit LC3 is connected to the connection point cp, the capacitor
C3 is connected to the ground, and the power supply voltage Vcc is
supplied to between the inductor L3 and the capacitor C3. The bias
circuit 13c is located at the closest position to the output side
of the transmission circuit 30a.
[0098] The high-frequency front end circuit 1 in the embodiment
includes the reception circuit 70a and the transmission circuit 30a
having the amplification circuit 10A. The amplification circuit 10A
is configured by the amplification circuit 10a and the
amplification circuit 10c connected in multistage. A frequency pass
band of the transmission circuit 30a is lower than a frequency pass
band of the reception circuit 70a and a value of a resonant
frequency fr of the bias circuit 13a is larger than a value of a
frequency pass band width .DELTA.f of the transmission circuit 30a.
A value of a resonant frequency fr of the bias circuit 13c is
larger than the value of the band width .DELTA.f of the
transmission circuit 30a.
[0099] The high-frequency front end circuit 1 has the
above-described configuration, so that odd-numbered order
intermodulation distortion which is generated at the high frequency
side of the transmission signal can be canceled using an
even-numbered order distortion component which is generated at the
lower frequency side at the outside of the transmission signal
frequency pass band. Therefore, generation of leakage power at the
high frequency side of the transmission signal, that is, the side
of the frequency band of the reception circuit can be
suppressed.
[0100] (Other Modes)
[0101] Although the high-frequency front end circuits 1, 1A, and 1B
according to the embodiments of the present disclosure have been
described above, the present disclosure is not limited to the
above-described embodiments. The present disclosure can also
encompass modes obtained by adding the following variations on the
above-described embodiments, for example.
[0102] For example, the bias circuit 13a may be provided at the
input side of the amplification element Tr as in an amplification
circuit 10d illustrated in FIG. 12. To be specific, the bias
circuit 13a may be connected to a connection point cp1 located
between the input matching circuit 14 and the amplification element
Tr. An input-side bias voltage Vb is supplied to between the
inductor L1 and the capacitor C1. Even when the amplification
circuit 10d is used instead of the amplification circuit 10a of the
high-frequency front end circuit 1, effects obtained in the first
embodiment can also be obtained.
[0103] Although the inductor L1 and the capacitor C1 in the LC
resonance circuit LC1 are connected in series in the bias circuit
13a illustrated in FIG. 3, the LC resonance circuit is not limited
thereto. The LC resonance circuit may be configured by connecting
the inductor L1 and the capacitor C1 in parallel.
[0104] Furthermore, each of the high-frequency front end circuits 1
to 1B may include a transmission circuit and a reception circuit
that transmit and receive signals in accordance with standards (for
example, the W-CDMA standard) other than the LTE standard.
Moreover, each of the transmission filter and the reception filter
is not limited to the SAW filter and may be a bulk acoustic wave
(BAW) filter.
[0105] Although each of the reception circuit connected to the
antenna terminal and the transmission circuit connected to the
antenna terminal is configured by the duplexer in the above
description, each of them may be configured by a multiplexer.
[0106] The present disclosure can be widely used for communication
apparatuses such as a cellular phone and a base station, as a
high-frequency front end circuit that can suppress the leakage of
the transmission signal amplified by the amplification circuit to
the adjacent frequency band.
[0107] While embodiments of the disclosure have been described
above, it is to be understood that variations and modifications
will be apparent to those skilled in the art without departing from
the scope and spirit of the disclosure. The scope of the
disclosure, therefore, is to be determined solely by the following
claims.
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