JP2000244262A - High frequency power amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency power amplifier which can correspond to even a request for making it smaller without necessity for adding a higher harmonic control circuit as an independent circuit and which is provided with a higher harmonic control function. SOLUTION: The high frequency power amplifier is provided with a high frequency amplifier part Q11, an input matching circuit, an output matching circuit and a DC bias circuit B connected to the output electrode of the part Q11. The bias circuit B comprises a distribution factor line L13, an inductor L14 serially connected to it and a capacitor C15 connected to L14 in parallel. The amplifier has a synthetic reactance component functioning as a part of the output matching circuit and also a resonance point of high-order higher harmonics with the line L13, the inductor L14 and the capacitor C15. The bias circuit B functions as a higher harmonic control circuit by which a direct current is supplied, the resonance point is finely adjusted and the high-order higher harmonics are removed so that the control circuit is not required to be added as independent circuit. Thus, the amplifier can to made smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency power amplifier used for amplifying high-frequency power in a microwave band or the like in communication equipment or the like.

[0002]

2. Description of the Related Art In recent years, various power amplifiers having a harmonic control circuit have been proposed as high-frequency power amplifiers used in communication equipment using high-frequency signals in a microwave band or the like. Above all, attention has been paid to a class F power amplifier that performs harmonic control for high-efficiency operation.

FIG. 2 is a circuit diagram showing an example of a typical circuit configuration of a high-frequency class F power amplifier having such a harmonic control circuit.

In FIG. 2, Q1 is a high-frequency transistor as a power amplifying unit for performing power amplification. Here, a field effect transistor (FET) is shown. C1 and C5 are decoupling capacitors for cutting off DC components between the high-frequency power amplifier and other circuits.
C2 · L1 and C4 · L3 are a capacitor and a distributed constant line (for example, a microstrip line) for optimizing impedance matching with an input / output circuit in order to bring out the performance of the high-frequency transistor Q1.

R1 and R2 are resistors constituting a bias circuit for supplying a bias voltage to a gate (control electrode) as an input electrode of the high-frequency transistor Q1.

L4 is a distributed constant line constituting a drain which is an output electrode of the high-frequency transistor Q1 and a bias circuit for supplying a current for output, and usually has a length of a quarter wavelength of the fundamental frequency. The impedance is seen to be infinite when viewed from the drain side of the high-frequency transistor Q1, or the line length is set to a negligibly large impedance when viewed from the impedance of the circuit. Further, the distributed constant line L4 may be shorter than the line length and used as a reactance component of a part of the matching circuit.

[0007] C6 and C7 are bypass capacitors for AC grounding.

[0008] Of these, the distributed constant line L4 and the bypass capacitor C6 can supply a DC current while maintaining an insulation state with respect to a high-frequency signal of a fundamental frequency. The power supply circuit S shown by a broken line in the drawing. Is composed.

The distributed constant line L2 and the capacitor C3 constitute a trap circuit T for higher harmonics, for example, a second harmonic, as a harmonic control circuit enclosed by a broken line in the figure.

Since the class F power amplifier amplifies the voltage waveform to a rectangular wave and the power waveform to a half wave and removes even-order frequency components of the fundamental frequency unnecessary for the rectangular wave, the trap circuit T includes, for example, It is set to have a series resonance point for a frequency twice as high as the fundamental wave, thereby removing the second harmonic by causing the impedance to appear to be zero and being grounded for the second harmonic. To be a higher harmonic control circuit.

As a result, the second harmonic component is reduced at the drain, which is the output of the high-frequency transistor Q1, so that the drain efficiency is improved.

[0012]

However, according to the conventional high-frequency class F power amplifier shown in FIG. 2, a trap circuit T as a harmonic control circuit must be added as a circuit separate from the amplifier circuit. In other words, the entire circuit becomes large, and there is a problem that it is not possible to meet the demand for further miniaturization of the high-frequency power amplifier.

When the distributed constant line L4 is used as a reactance component of a part of a matching circuit, the distributed constant line L4 is formed as an inner layer using a multilayer wiring board in response to a demand for downsizing of a high-frequency power amplifier. In some cases, since the length of the distributed constant line L4 cannot be finely adjusted, there is a problem that it is difficult to set an output matching circuit so as to obtain desired output characteristics.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and does not require the addition of a harmonic control circuit as a separate circuit. It is an object of the present invention to provide a high-frequency power amplifier having a function.

[0015]

A high-frequency power amplifier according to the present invention comprises: a high-frequency amplifier for amplifying a high-frequency signal from an input electrode and transmitting the amplified signal from an output electrode; an input matching circuit connected to the input electrode; An output matching circuit and a DC current bias circuit connected to the output electrode, wherein the DC current bias circuit is connected in parallel with the distributed constant line, an inductor connected in series in the middle of the distributed constant line, and the inductor. Having a combined reactance component necessary to function as a part of the output matching circuit, and having a resonance point with respect to a higher-order harmonic of a fundamental frequency of the high-frequency signal. Is what you do.

According to the high-frequency power amplifier of the present invention, a distributed constant line, an inductor connected in series in the middle of the distributed constant line, It consists of a capacitor connected in parallel with the inductor and also connected in series in the middle of the distributed parameter line, which is necessary to function as a part of the output matching circuit by the line length of the distributed parameter line, the inductance of the inductor, and the capacitance of the capacitor. And a distributed constant line to which the combined reactance is connected, the combined reactance having a combined reactance component, and having a capacitance component combined by the capacitance (capacity) of the capacitor and the inductance of the inductor to which the capacitor is connected in parallel. Inductance component And the series resonance frequency is set as the resonance point for the higher harmonics of the fundamental frequency.Therefore, this bias circuit has an almost infinite impedance with respect to the fundamental frequency. To supply the direct current while blocking the current, or to supply the direct current while becoming a reactance component of the output matching circuit, and for any higher-order harmonic of the fundamental frequency. When viewed from the output electrode of the high-frequency amplifier, it is grounded and functions as a harmonic control circuit that can remove any higher harmonics. As a result, there is no need to add a harmonic control circuit as a separate circuit, and a high-frequency power amplifier having a harmonic control function capable of responding to a demand for further miniaturization is provided.

In the bias circuit, the inductance component of the inductor, the capacitance component of the capacitor, the combined reactance of the capacitance component of the capacitor and the inductance component of the inductor to which this capacitor is connected in parallel, or the inductor and the capacitor connected in series The combined reactance with the distributed constant line and the inductance component of the distributed constant line can be easily adjusted by adjusting the capacitance value of the capacitor, the inductance of the inductor, the line length of the distributed constant line, etc. The resonance frequency, that is, the resonance point can be easily adjusted for any higher harmonic such as the second or third, fourth, or fifth harmonic as the higher harmonic. , F class power amplification It can be applied to other high-frequency power amplifier not only, but can also be used for the purpose of removing spurious harmonics included in the output of the high frequency power amplifier.

Further, the inductance of the inductor and the capacitance of the capacitor connected in series to the distributed constant line of the bias circuit can be easily finely adjusted at the time of circuit configuration or after the circuit configuration. Since fine adjustment can be easily performed, the high-frequency power amplifier can easily adjust the electrical characteristics of the high-frequency power amplifier with high accuracy.

Furthermore, when the distributed constant line is internally formed using a multilayer wiring board in response to the demand for downsizing of the high-frequency power amplifier, the capacitance of the inductor and the capacitor of the inductor is reduced while downsizing the high-frequency power amplifier. It is possible to easily set an output matching circuit so that the desired output characteristics can be adjusted and adjusted.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing an example of a circuit configuration of a high-frequency power amplifier according to the present invention, and shows a high-frequency class F power amplifier as in FIG.

In FIG. 1, Q11 is a high-frequency transistor as a high-frequency amplifier for performing power amplification, and is an amplifier used in a frequency range such as several hundred MHz to several GHz to which a distributed constant line can be applied. Here, a field effect transistor is shown as an example. C11 and C14 are decoupling capacitors for cutting off DC components between the high-frequency power amplifier and other circuits. C
Reference numerals 12 and L11 denote a capacitor and a distributed constant line (for example, a microstrip line) constituting an input matching circuit for matching impedance between the high-frequency transistor Q11 and the input circuit in order to bring out the performance of the high-frequency transistor Q11. C13 and L13 are capacitors and distributed constant lines (for example, microstrip lines) constituting an output matching circuit for achieving matching that satisfies desired output characteristics such as distortion characteristics, output power, and current consumption independently or simultaneously. It is. These input matching circuits are gates (control electrodes) which are input electrodes of the high-frequency transistor Q11.
The output matching circuit is connected to the drain (output electrode) of the high-frequency transistor Q11.

R11 and R12 are resistors constituting a bias circuit for supplying a bias voltage to the gate of the high-frequency transistor Q11.

L13 is a distributed constant line composed of, for example, a microstrip line or a strip line which constitutes a bias circuit for supplying a direct current for drain and output of the high-frequency transistor Q11. L14 is an inductor connected in series with a part of the distributed constant line L13, here a part on the power supply side, and C15 is a capacitor connected in parallel with the inductor L14. It is connected. The line length of the distributed constant line L13, the inductance of the inductor L14, and the combined reactance component due to the capacitance of the capacitor C15 are set to function as a part of the output matching circuit.

The impedance of the distributed constant line L13 is not limited to the line length of one quarter wavelength of the fundamental frequency so that the impedance looks infinite as an impedance or the quarter wavelength of the fundamental frequency. Even if it is shorter than the length, it is not necessary to set it to a length that is negligible from the viewpoint of the circuit impedance, such as 10 times or more the impedance at the fundamental frequency of the circuit. May be set to a required value in accordance with the design specifications of the circuit within a range that is not negligible and has an influence on the circuit.

In this example, on the power supply side, an inductor L14 is connected in series and a capacitor C15 is connected in parallel with the inductor L14, and the inductance of the inductor L14 and the capacitor C15 in the middle of the distributed constant line L13.
By changing the capacitance, the output impedance of the output matching circuit can be adjusted to a desired output characteristic by changing the impedance of the harmonic. At this time, when the impedance of the fundamental frequency changes, the adjustment may be performed by changing the value of each element of the output matching circuit, for example, the capacitance of C13 and C14.

Then, a combined reactance having a capacitance component combined by the capacitance of the capacitor C15 and the inductance of the inductor L14 to which the capacitor C15 is connected in parallel, and the inductance component of the distributed constant line L13 to which the combined reactance is connected Constitutes a resonance circuit section D (shown by a dashed line in the figure) which is a series resonance circuit, and the series resonance frequency is adjusted to an arbitrary higher-order harmonic of the fundamental frequency. The resonance circuit section D has a resonance point for any higher harmonic of the fundamental frequency.

C16 and C17 are bypass capacitors for grounding each other AC. The bypass capacitor C16 and the inductor L14
A resonance circuit section D having a harmonic control function is provided by a capacitor C15 and a distributed constant line L13 in which they are connected in series.
, And constitutes a DC current bias circuit B enclosed by a broken line in the figure.

As described above, the high-frequency power amplifier of the present invention is connected to the high-frequency amplifier section for amplifying the high-frequency input signal supplied to the input electrode and outputting the high-frequency output signal from the output electrode as the high-frequency output signal. An input matching circuit for matching input impedance with respect to a fundamental frequency of a high-frequency input signal, an output matching circuit connected to the output electrode for matching desired output durability, and connected to the output electrode; And a bias circuit including a distributed constant line for supplying a direct current, an inductor connected in series in the middle of the distributed constant line, and a capacitor connected in parallel to the inductor, and the bias circuit includes: It has a combined reactance component necessary to function as a part of the output matching circuit, and has the distributed constant line and the inductor It is characterized in that it has a resonance point with respect to higher harmonics of the fundamental frequency by motor and said capacitor.

According to the high frequency power amplifier of the present invention, the bias circuit B is connected to the distributed constant line L13 and the inductor L14 and the inductor L14 connected in series to the distributed constant line L13.
14 has a resonance point for any higher-order harmonic of the fundamental frequency by the resonance circuit portion D constituted by the capacitor C15 connected in parallel with the capacitor C15, so that the impedance becomes zero for any higher-order harmonic. It is visible and grounded.
For example, in the case of a class F power amplifier, by setting the resonance point to the second harmonic of the fundamental frequency, an even order of the fundamental frequency, that is, 2nd harmonic, which is unnecessary to approximate the voltage waveform to a rectangular wave.
The second harmonic can be removed. As a result, in the drain which is the output electrode of the high-frequency transistor Q11, the component of the second harmonic is reduced and the drain efficiency is improved.

Here, the inductance value of the inductor L14 and the capacitance value (capacitance value) of the capacitor C15.
Only replaces inductors and capacitors,
Alternatively, since the adjustment can be easily performed by using a variable inductor or a variable capacitor, an arbitrary resonance point can be set by the resonance circuit section, whereby fine adjustment of the resonance point can be easily and accurately performed.

Further, since the second harmonic of the fundamental frequency can be removed without adding another harmonic control circuit,
It becomes a very small high frequency power amplifier.

As the inductor L14 in the bias circuit B of the high-frequency power amplifier of the present invention, for example, a conductor winding pattern is formed on the surface of a dielectric sandwiched between two electrodes, which is often used in high-frequency circuits. If the chip inductor described above is used, it can be arranged on the surface of the substrate constituting the high-frequency power amplifier and its inductance can be finely adjusted, which is preferable. Further, as the capacitor C15, for example, if a multilayer ceramic chip capacitor, which is often used in high-frequency circuits, is used, the capacitance can be similarly fine-adjusted by arranging it on the surface of a substrate constituting a high-frequency power amplifier. It becomes suitable. Thereby, the resonance point of the resonance circuit section D can be easily finely adjusted.

The above embodiment has been described based on an example in which a high-frequency class F power amplifier has a harmonic control function for removing a second harmonic of a fundamental frequency.
The high-frequency power amplifier of the present invention is not limited to these, and various changes and improvements can be made without departing from the scope of the present invention. For example, as described above, the resonance point may be adjusted for higher harmonics than the second order, and the present invention may be applied to a high frequency power amplifier other than the class F power amplifier. Further, it may be used for the purpose of removing spurious harmonics contained in the output of the high frequency power amplifier.

As the high frequency amplifying unit, a high frequency power amplifying circuit having a similar high frequency power amplifying function may be used in addition to the high frequency transistors such as the field effect transistor shown in the above example.

[0035]

According to the high frequency power amplifier of the present invention,
As a bias circuit for supplying a DC current to the output electrode of the high-frequency amplifier, a distributed constant line, an inductor connected in series in the middle of the distributed constant line, and a capacitor connected in parallel to the inductor are provided. Due to the line length of the line, the inductance of the inductor, and the capacitance of the capacitor, it has a combined reactance component required to function as a part of the output matching circuit,
In addition, a series resonance circuit is formed by a combined reactance having a capacitance component synthesized by the capacitance of the capacitor and the inductance of the inductor connected in parallel with the capacitor, and the inductance component of the distributed constant line to which the combined reactance is connected. Since the series resonance frequency is the resonance point for higher harmonics of the fundamental frequency, this bias circuit has an almost infinite impedance to the fundamental frequency and supplies DC current while blocking high-frequency signals. Or to achieve the original purpose of supplying DC current while becoming a reactance component of the output matching circuit,
Any higher-order harmonic of the fundamental frequency is grounded when viewed from the output electrode of the high-frequency amplifier, and functions as a harmonic control circuit that can remove the higher-order harmonic. Become. As a result, there is no need to add a harmonic control circuit as a separate circuit, and a high-frequency power amplifier having a harmonic control function capable of responding to a demand for further miniaturization is obtained.

In this bias circuit, the inductance component of the inductor, the capacitance component of the capacitor, and the inductance component / capacitance component of the distributed constant line adjust the inductance of the inductor, the capacitance of the capacitor, and the line length of the distributed constant line, respectively. As a result, the resonance point can be adjusted easily and with high accuracy, so that the resonance point can be easily adjusted not only for the second harmonic but also for higher harmonics. It can also be used for the purpose of removing spurious harmonics contained in the output of the high-frequency power amplifier.

Further, even when the distributed constant line forming the bias circuit is formed as an inner layer on the multilayer wiring board, the inductor and the capacitor connected in series to the distributed constant line can be formed by using a small chip inductor or chip capacitor. By arranging it on the surface of the board, the impedance of the harmonics can be easily changed by changing the inductance of the inductor and the capacitance of the capacitor, and the output matching circuit can be matched to the desired output characteristics. it can.

Furthermore, a high frequency power amplifier having a harmonic control function can be constructed without mounting a harmonic control circuit by simply mounting one inductor and one capacitor on the substrate for one bias circuit. As a result, a high-frequency power amplifier that can meet the demand for miniaturization is obtained.

Therefore, according to the present invention, there is provided a high-frequency power amplifier having a harmonic control function, which does not need to add a harmonic control circuit as a separate circuit and can respond to a demand for further miniaturization. Could be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an example of a circuit configuration of a high-frequency power amplifier according to the present invention.

FIG. 2 is a circuit diagram showing an example of a circuit configuration of a conventional high-frequency class F power amplifier.

[Explanation of symbols]

 Q11: High-frequency transistor (high-frequency amplifier) L13: Distributed constant line L14: Inductor C15: Capacitor B: DC current bias circuit

Claims (1)

[Claims] A high-frequency amplifier for amplifying a high-frequency signal from an input electrode and transmitting the amplified signal from an output electrode; an input matching circuit connected to the input electrode; an output matching circuit connected to the output electrode; A bias circuit, wherein the DC current bias circuit comprises a distributed constant line, an inductor connected in series in the middle of the distributed constant line, and a capacitor connected in parallel to the inductor, and a part of the output matching circuit. A high-frequency power amplifier having a combined reactance component necessary for functioning as a power supply, and having a resonance point with respect to a higher-order harmonic of a fundamental frequency of the high-frequency signal.