JP2005341447A - High-frequency power amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-frequency amplifier of a wide bandwidth which can be controlled by minimizing influence of a deviation of high and low impedances of a desired frequency bandwidth from an optimum impedance on an frequency bandwidth other than the desired frequency bandwidth. <P>SOLUTION: A high-frequency power amplifier is provided with a high-frequency transistor 1, a basic wave matching circuit 7, and an impedance control circuit 9A supplying direct current to the high-frequency transistor 1 from a power supplying terminal P1 through a bias circuit 8 composed of a high harmonic processing circuit 6, a capacitor 5 for bypass, and a bias line 3 as a distributed constant line, which is composed of a serial circuit of an inductor 10 on the power supplying terminal P1 of the bias circuit 8, a capacitor 11, and resistor 12, for a desired frequency, so that low and high impedances of desired frequency bandwidths may be controlled. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high frequency power amplifier.

FIG. 5 shows a conventional high-frequency power amplifier.
In this example, a high-frequency transistor 1 having a single-stage configuration for amplifying a high-frequency signal and its output matching circuit are included. Pin is a high-frequency signal input terminal, and Pout is a high-frequency signal output terminal. Some high-frequency amplifiers are composed of a plurality of high-frequency transistors.

  A direct current is supplied from the power supply terminal P <b> 1 to the drain of the high-frequency transistor 1 through the bias circuit 8. Specifically, the bias circuit 8 is usually configured by a bias line 3 that secures a length of a quarter of the fundamental frequency (0.9 G to 1.0 GHz). The bias line 3 is designed to have such a length that the fundamental impedance is sufficiently higher than the transmission line 2 on the power supply side to the high-frequency transistor 1.

  If a quarter wavelength of the fundamental wave frequency cannot be secured as the bias line 3, the electrical length of the bias line of the fundamental wave is equivalently converted to an equivalent to the electrical length of the quarter wavelength by the impedance conversion capacitor 4. ing.

The capacitor 5 connected to the DC power supply terminal P1 side of the bias line 3 is a bypass capacitor of about 1000 pF.
On the output side of the high frequency transistor 1, as an output matching circuit for obtaining desired output characteristics, a fundamental wave matching circuit 7 that optimizes the fundamental wave impedance and a harmonic that optimizes the higher harmonic impedance. A wave processing circuit 6 is provided. For example, in the case of class F amplification operation, the harmonic processing circuit 6 is configured to short-circuit even-order harmonics and open odd-numbered harmonics.
JP 2000-106510 A

  In recent mobile communication devices, there is an increasing demand for wider bandwidth. However, in the conventional output load circuit, as the bandwidth becomes wider, the impedance of the high and low frequencies in the desired frequency band becomes more deviated from the optimum impedance matching, making it difficult to obtain the desired output characteristics in the wide band. There is a problem.

  An object of the present invention is to provide a broadband high-frequency amplifier that can suppress a deviation from the optimum impedance of high and low frequencies in a desired frequency band without affecting the frequency band other than the desired frequency band as much as possible. To do.

  The high frequency power amplifier according to claim 1 of the present invention includes a high frequency transistor that amplifies and outputs a high frequency input signal, and a capacitor for AC short-circuiting with a distributed constant line for supplying a direct current to the high frequency transistor. A bias circuit, a fundamental wave matching circuit provided on the output side of the high-frequency transistor for controlling the fundamental frequency of the input signal to an optimum impedance position, and an impedance control circuit provided on the power source side of the bias circuit. The impedance control circuit has a resonance point with respect to a desired frequency by a series circuit of an inductor component, a capacitor component, and a resistance component whose end points are grounded, and the desired impedance without affecting the impedance other than the desired frequency as much as possible. It is characterized by controlling the impedance in the low and high frequencies.

  The high-frequency power amplifier according to claim 2 of the present invention is the high-frequency power amplifier according to claim 1, wherein the plurality of impedance control circuits are connected in parallel on the power supply side of the bias circuit, and the frequency of the resonance point of each impedance control circuit is varied. It is characterized by.

  According to the configuration of the first aspect of the present invention, the load viewed from the output side of the high frequency transistor due to resonance of the series circuit of the inductor component, the capacitor component, and the resistance component as the impedance control circuit installed on the power supply side of the bias circuit. In the impedance, for example, a resonance circle is generated on the Smith chart in the fundamental frequency band by the inductor component and the capacitor component, and the resonance circle is controlled by the resistance component, so that the phase difference between the high frequency band and the low frequency band of the fundamental frequency band Since the impedance control circuit is installed after the bypass capacitor on the power supply side, it is optimally matched in both the high and low frequencies of the fundamental frequency band without affecting the impedance other than the fundamental frequency as much as possible. It is possible to realize a broadband and high-performance high-frequency amplifier capable of taking

  In addition, the fundamental frequency is sufficiently matched by the fundamental matching circuit for the desired characteristics of the amplifier, such as gain, distortion, and efficiency, and there is no need to suppress phase difference in the fundamental frequency band. In the class F amplifier, etc., which controls high-order harmonics, phase control of the high-order harmonic band and impedance control of the frequency band contributing to the oscillation of the amplifier are possible. For example, in the control of higher-order harmonics, the resonance circle generated by the second-order harmonic band enters the inside of the Smith chart by controlling the resonance circle with a resistance component, thereby reducing the efficiency of the amplifier due to the second-order harmonic loss. Without this, it is possible to reduce the phase difference between the high and low frequencies of the high-order frequency band.

  According to the configuration of claim 2 of the present invention, since the impedance control circuit is provided in plural, resonance points can be provided in the plurality of frequency bands, and the load impedance viewed from the output side of the high frequency transistor For example, a class F operational amplifier that is a high-efficiency amplifier that controls the impedance of the fundamental frequency and the higher-order harmonics, and the fundamental frequency band and the higher-order harmonics band by the inductor component and the capacitor component of a plurality of impedance control circuits. By generating a resonance circle on the Smith chart and controlling the resonance circle with a resistance component, it becomes possible to reduce the phase difference between the high frequency band and the low frequency band of the fundamental frequency band and the high-order harmonic band. Since the control circuit is installed on the power supply side after the bypass capacitor, it is affected as much as possible by impedance other than the fundamental frequency and higher harmonic band. Without giving a high-frequency, it can be realized a high-performance high-frequency amplifier in a broad band that can take an optimal matching in both the low frequency range. Further, not only the fundamental frequency and the higher harmonic band, but also the impedance control of the frequency band contributing to the oscillation of the amplifier is possible.

Embodiments of the present invention will be described below with reference to FIGS.
Here, the high-frequency transistor is a field effect transistor and the fundamental frequency is 0.9 GHz to 1.0 GHz, but is not limited thereto. A circuit configuration in which the bias line length is λ / 12 and the fundamental wave impedance is converted to λ / 4 by an impedance conversion capacitor will be described as an example.

(First embodiment)
1 and 2 show a first embodiment of the present invention.
In FIG. 1, on the output side of the high frequency transistor 1, a direct current is supplied to the drain of the high frequency transistor 1 through a bias circuit 8 including a bypass capacitor 5 and a bias line 3 as in the conventional example shown in FIG. Has been.

  The bias line 3 is designed to have such a length that the fundamental impedance is sufficiently higher than the transmission line 2 on the power supply side to the high frequency transistor 1. When the length of a quarter wavelength of the fundamental frequency cannot be secured as the bias line 3, the electrical length of the fundamental bias line is equivalently converted to an equivalent of one quarter electrical length by the impedance conversion capacitor 4. doing. That is, when the capacitor 4 is used, the bias line 3 and the capacitor 4 constitute a distributed constant line for supplying a direct current to the high-frequency transistor 1.

A fundamental wave matching circuit 7 and a harmonic processing circuit 6 are provided on the output side of the high frequency transistor 1.
Further, an impedance control circuit for controlling the impedance with respect to the fundamental frequency consists of a series circuit of an inductor element 10, a capacitor element 11, and a resistor element 12 between the power supply terminal P1 side P2 of the bias line 3 and the reference potential G. 9A is connected.

  Here, the fundamental frequency band is 0.9 GHz to 1.0 GHz, and the resonance frequency due to the inductance component of the inductor element 10 and the capacitance component of the capacitor element 11 is set to the fundamental frequency band.

  In this case, the impedance of the load matching circuit viewed from the drain end of the high-frequency transistor can realize a resonance circle in the fundamental frequency band without affecting as much as possible on the Smith chart other than the fundamental frequency band. By suppressing the size of the circle, it is possible to suppress the impedance change between 0.9 GHz and 1.0 GHz, which are the low and high frequencies.

The effect of impedance in the fundamental frequency band by the impedance control circuit 9A is shown in FIG.
FIG. 2 shows the R and X variations of the impedance Z = R + jX in the fundamental frequency band, and 0.9 GHz is the reference value 0. In the conventional configuration, the impedance variation in the fundamental frequency band of 0.9 GHz to 1.0 GHz is about 1.7Ω for R and about 2Ω for X. In the first embodiment of the present invention, 0.5Ω for R. , X drastically suppresses the impedance change to about 1.3Ω.

  Note that the resistance component of the resistance element 12 can use the parasitic resistance component of the inductor element 10 and the capacitor element 11, so that the resistance chart is not limited to the resistance element, but a Smith chart can be used if a low Q value is used. It is possible to suppress the size of the resonance circle above.

  Here, the case where the resonance point of the impedance control circuit 9A is set to the fundamental frequency band has been described as an example. However, for the fundamental frequency pair, the fundamental characteristic matching circuit 7 sufficiently satisfies the desired characteristics of the amplifier, For example, when the frequency characteristics are flatly matched in terms of gain, distortion, efficiency, etc., and there is no need to suppress the phase difference in the fundamental frequency band, the resonance point of the impedance control circuit 9A is set to the harmonic band, specifically, By setting the second harmonic band, the resonance circle generated by the second harmonic band enters the inside of the Smith chart by controlling the resonance circle with the resistance component. It is possible to reduce the phase difference between the high and low frequencies of the high-order frequency band without reducing the efficiency, and in particular, high-order harmonics in class F amplifiers that control high-order harmonics. Phase control, it is possible to impedance control contributes frequency band to the oscillation of the amplifier.

  Although the configuration is different from that of the first embodiment of the present invention, the impedance change can be suppressed even when the inductor element is installed in series with the bias line. In this case, the bias due to the resistance component of the inductor element is suppressed. This is not effective because it affects the performance degradation of the high-frequency amplifier due to the voltage drop.

(Second Embodiment)
3 and 4 show a second embodiment of the present invention.
The high-frequency amplifier shown in FIG. 3 is different from the first embodiment in that a plurality of impedance control circuits 9A and 9B are connected between the power supply terminal P1 side P2 and the reference potential G. The rest is the same as in the first embodiment.

  Capacitor 5 is a bypass capacitor of about 1000 pF. The impedance control circuit 9A includes a series circuit of an inductor element 10, a capacitor element 11, and a resistance element 12. The impedance control circuit 9B includes a series circuit of an inductor element 14, a capacitor element 15, and a resistance element 16.

  The resonance point of the impedance control circuit 9A is set to the fundamental frequency band 0.9 GHz to 1.0 GHz, and the resonance point of the impedance control circuit 9B is set to the second harmonic.

  In this case, the impedance of the load matching circuit viewed from the drain end of the high frequency transistor has no influence on the fundamental frequency band and the second harmonic band as much as possible on the Smith chart, and the fundamental frequency band and the second harmonic. A resonance circle can be realized in the band, and the size of the resonance circle is controlled by the resistance element 12 and the resistance element 16, respectively, so that the fundamental frequency band is between 0.9 GHz and 1.0 GHz and the second harmonic band. An impedance change between 1.8 GHz and 2.0 GHz can be suppressed.

  Note that the resistance component by the resistance element 12 can use the parasitic resistance component of the inductor element 10 and the capacitor element 11, and thus is not limited to the resistance element. The resistance component due to the resistance element 16 can use the parasitic resistance component of the inductor element 14 and the capacitor element 15, and is not limited to the resistance element.

  Further, FIG. 4 shows the effect of suppressing the impedance change in the second harmonic band by the impedance control circuit 9B. Since the higher-order harmonic phase control affects the efficiency of the amplifier in an amplifier for class F operation or the like, FIG. 4 shows the amount of phase change in the second-order harmonic band. In the conventional configuration, the second-order harmonic is shown. Although the phase change amount of the wave frequency band 1.8 GHz to 2.0 GHz is about “14 degrees”, in the second embodiment of the present invention, the phase change of the second harmonic frequency band 1.8 GHz to 2.0 GHz. Even when multiple impedance control circuits are provided with an amount of "6 degrees", drastic phase change suppression is possible even in the second harmonic frequency band without degrading the impedance suppression effect in the fundamental frequency band. It is.

  In this way, it is possible to reduce the phase difference between the high frequency band and the low frequency band of the fundamental frequency band and the second harmonic band, and the impedance control circuit is installed on the power supply side after the bypass capacitor. It is possible to realize a broadband and high-performance high-frequency amplifier that can achieve optimum matching in both high and low frequencies without affecting the impedance other than the frequency and the second harmonic band as much as possible. Further, it is possible to control the impedance of the frequency band that contributes to the oscillation of the amplifier, as well as the higher harmonic band such as the fundamental frequency and the second order. Specifically, for each frequency whose impedance is to be controlled, three or more impedance control circuits each having a resonance point at that frequency are provided in parallel on the power supply side of the bias circuit 8, so that “frequency contributing to oscillation”. "(1/2 frequency of the fundamental wave, etc.) can be controlled simultaneously, and a more efficient and stable (not oscillating) high-frequency amplifier can be realized.

1 is a circuit diagram of a high-frequency power amplifier according to a first embodiment of the present invention. The figure which shows the impedance control effect of the fundamental frequency band in the same embodiment Circuit diagram of high-frequency power amplifier according to second embodiment of the present invention The figure which shows the phase control effect of the 2nd harmonic band in the same embodiment Circuit diagram of conventional high-frequency power amplifier

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High frequency transistor 2 Transmission line 3 Bias line 4 Capacitor 5 Capacitor 6 Harmonic processing circuit 7 Fundamental wave matching circuit 8 Bias circuit 9A, 9B Impedance control circuit 10 Inductor element 11 Capacitor element 12 Resistance element

Claims (3)

A high-frequency transistor that amplifies and outputs a high-frequency input signal; and
A bias circuit comprising a capacitor for short-circuiting with a distributed constant line for supplying a direct current to the high-frequency transistor; and
A fundamental matching circuit that is provided on the output side of the high-frequency transistor and controls the fundamental frequency of the input signal to an optimum impedance position;
An impedance control circuit provided on the power supply side of the bias circuit, and the impedance control circuit has a resonance point with respect to a desired frequency by a series circuit of an inductor component, a capacitor component, and a resistance component whose end points are grounded. A high frequency power amplifier. 2. The high-frequency power amplifier according to claim 1, wherein a plurality of the impedance control circuits are connected in parallel to the power supply side of the bias circuit, and the frequency of the resonance point of each impedance control circuit is varied. On the power supply side of the bias circuit, a first impedance control circuit in which the resonance point frequency is set to the fundamental frequency and a second impedance control circuit in which the resonance point frequency is set to the second harmonic are connected in parallel. The high frequency power amplifier according to claim 2.

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