JPH10322145A - Power amplifier for high frequency - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power amplifier for high frequencies having a higher harmonics control function, in which it is not necessary to add any higher harmonics control circuit as a separate circuit, and it is possible to facilitate a countermeasure to a request for further miniaturization. SOLUTION: This power amplifier for high frequencies is provided with a high-frequency transistor Q11, an input matching circuit, an output matching circuit, and a bias circuit B connected with the output electrode of the high-frequency transistor Q11, which is constituted of a distribution constant line L13 and a capacitor C15 connected with one part of this in parallel. In this case, the bias circuit B is provided with composite reactance components necessary for functioning as one part of the output matching circuit by the length of the distribution constant line L13 and the capacity of the capacitor C15, and a resonance point for high-order higher harmonics by the distribution constant line L13 and the capacitor C15. The bias circuit B which functions as one part of the output matching circuit supplies DC currents and also functions as a higher harmonics control circuit for removing high-order harmonics. Thus, it is not necessary to provide a separate higher harmonics control circuit.

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 the microwave band or the like. Attention has been focused on class F power amplifiers that perform harmonic control for operation.

FIG. 4 is a circuit diagram showing an example of a circuit configuration of a typical high-frequency class F power amplifier having a harmonic control circuit, which is used in communication equipment and the like.

In FIG. 4, Q1 is a high-frequency transistor for amplifying power, and C1 and C5 are decoupling capacitors for cutting off DC components from 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 the gate of the high-frequency transistor Q1. L4 is a distributed constant line constituting a drain circuit 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 so that the drain of the high-frequency transistor Q1 The length is set so that the impedance looks infinite when viewed from the side, or the impedance becomes negligibly large when viewed from the impedance of the circuit. The length of the distributed constant line L4 can be made shorter than the length and used as a reactance component of a part of the output matching circuit. C
Reference numerals 6 and C7 denote bypass capacitors for alternating-current grounding. Among these, a power supply circuit S enclosed by a broken line is formed, which can supply a DC current while ensuring an insulation state with respect to a high frequency signal of a fundamental frequency by the distributed constant line L4 and the bypass capacitor C6.

[0005] The distributed constant line L2 and the capacitor C3 form a trap circuit T for a second harmonic as a harmonic control circuit indicated by a broken line.

[0006] In the class F power amplifier, since the voltage waveform is amplified with a rectangular wave and a current waveform as a half wave, an even-order frequency component of the fundamental frequency unnecessary for the rectangular wave is removed. 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. 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.

[0008]

However, according to the conventional high-frequency class F power amplifier shown in FIG. 4, 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.

The present invention has been devised 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.

[0010]

A high-frequency power amplifier according to the present invention is connected to a high-frequency transistor for amplifying a high-frequency input signal supplied to a control electrode and outputting it as a high-frequency output signal from an output electrode; An input matching circuit for matching input impedance to a fundamental frequency of the high-frequency input signal, connected to the output electrode, an output matching circuit for matching desired output characteristics, and connected to the output electrode; And a bias circuit including a distributed constant line for supplying a direct current and a capacitor connected in parallel to a part of the distributed constant line, and the bias circuit functions as a part of the output matching circuit. The distributed constant line and the capacitor to resonate with higher harmonics of the fundamental frequency. It is characterized in that it has a.

According to the high frequency power amplifier of the present invention, the bias circuit for supplying a direct current to the output electrode of the high frequency transistor comprises a distributed constant line and a capacitor connected in parallel to a part of the distributed constant line, Due to the length of the distributed constant line and the capacitance of the capacitor, it has a combined reactance component necessary to function as a part of the output matching circuit, and the capacitance of a capacitor connected in parallel with a part of the distributed constant line, Series resonance occurs due to the combined reactance having a capacitor component that is combined with the inductance of the distributed constant line at the portion connected in parallel with the capacitor, and the inductance component of the distributed constant line at a portion other than the portion where the capacitor is connected in parallel. Construct a circuit and adjust its series resonance frequency to higher harmonics of the fundamental frequency. Since the bias point is set, this bias circuit achieves the original purpose of supplying a DC current while becoming a reactance component of a part of the output matching circuit, and at the same time with respect to any higher-order harmonic of the fundamental frequency. As a result, it becomes grounded when viewed from the output electrode of the high-frequency transistor, and functions as a harmonic control circuit capable of removing 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 combined reactance of the capacitance of the capacitor and the distributed constant line to which the capacitor is connected in parallel and the inductance component of the distributed constant line adjust the capacitance value of the capacitor and the length of the distributed constant line, respectively. Therefore, the resonance frequency, that is, the resonance point can be easily adjusted for any higher harmonic such as second, third, fourth, fifth, etc. as the higher harmonic. This is applicable not only to the class F power amplifier but also to other high frequency power amplifiers, and can also be used for the purpose of removing spurious harmonics contained in the output of the high frequency power amplifier.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described 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.
A class power amplifier is shown as an example.

In FIG. 1, Q11 is a high-frequency transistor for amplifying power, for example, several hundred MHz to several GH.
This is used in a frequency range to which a distributed constant line such as z can be applied. C11 and C14 are decoupling capacitors for blocking DC components from other circuits, respectively, and C12 and L11 are input matching circuits for impedance matching with the input / output circuit to bring out the performance of the high-frequency transistor Q11. The constituent capacitors and distributed constant lines, for example, microstrip lines. C13 and L12 are capacitors and distributed constant lines, for example, microstrip lines, which constitute an output matching circuit for achieving matching so as to satisfy desired output characteristics such as distortion characteristics, output voltage, current consumption, etc. singly or simultaneously. is there. These input matching circuits are high-frequency transistors Q11
The output matching circuit is a high-frequency transistor Q11
Are connected to the respective output electrodes. R11 and R12 are the gates (control electrodes) of the high-frequency transistor Q11, respectively.
Is a resistance constituting a bias circuit for supplying a bias voltage to the bias circuit. L13 is a distributed constant line composed of, for example, a microstrip line constituting a drain (output electrode) of the high-frequency transistor Q11 and a bias circuit for supplying a current for output.
The length is set so that the combined reactance of the output matching circuit and the capacitor C15 functions as a reactance component of a part of the output matching circuit. The impedance is set to a quarter wavelength of the fundamental frequency so that the impedance looks infinite as an impedance. Even if the impedance is shorter than a quarter wavelength of the fundamental frequency, the impedance of the circuit at the fundamental frequency is reduced.
Rather than setting the length so that it is negligibly large when viewed from the impedance of the circuit, such as 10 times or more, the range that can not be ignored when viewed from the impedance at the fundamental frequency of the circuit In this case, the value may be set to a required value according to the circuit design specifications.
A capacitor C15 is connected in parallel to a part of the distributed constant line L13 on the power supply side.
And a combined reactance having a capacitance component combined by the capacitance of a capacitor C15 connected in parallel with a part of the capacitor C15 and the inductance of a distributed constant line L13 connected in parallel with the capacitor C15, and connected in parallel with the capacitor C15. A series resonance circuit is formed by the inductance component of the distributed constant line L13 other than the portion where the resonance frequency is set, and the series resonance frequency is adjusted to an arbitrary higher-order harmonic of the fundamental frequency. It has a resonance point for the second harmonic. Also, C16
C17 is a bypass capacitor for grounding each other AC. Of these, capacitor C15
Are connected in parallel to form a bias circuit B enclosed by a dashed line in which a resonance circuit section D having a harmonic control function surrounded by an alternate long and short dash line is constituted by a distributed constant line L13 and a bypass capacitor C16. .

As described above, according to the high-frequency power amplifier of the present invention, the bias circuit B has an arbitrary fundamental frequency by the resonance circuit section D constituted by the distributed constant line L13 and the capacitor C15 connected in parallel to the distributed constant line L13. Has a resonance point with respect to the higher-order harmonics, the impedance appears to be 0 for any higher-order harmonics, and the state is 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-number order, that is, the second harmonic, of the fundamental frequency that is unnecessary to approximate the voltage waveform to a rectangular wave is removed. As a result, in the drain, which is the output of the high-frequency transistor Q11, the second harmonic component is reduced and the drain efficiency is improved.

In addition, 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.

Next, an example of a resonance circuit section in a bias circuit of a high-frequency power amplifier according to the present invention, comprising a distributed constant line and a capacitor connected in parallel to a part of the distributed constant line, is shown in FIGS. It is shown in (c).

FIG. 2A is a plan view showing a resonance circuit section having the same configuration as the resonance circuit section D shown in FIG. 1. L21 is a distributed constant line composed of, for example, a strip line or a microstrip line. A part thereof is bent in a U shape. C21 is a capacitor connected to the bent portion of the distributed constant line L21. In this example, a multilayer ceramic chip capacitor is used, and external electrodes C21b formed at both ends of the capacitor body C21a are shown. Is connected in parallel with the distributed constant line L21.

As a result, a composite having a capacitor component composed of the capacitance of the capacitor C21 connected in parallel with a part of the distributed constant line L21 and the inductance of the distributed constant line L21 in a part connected in parallel with the capacitor C21. The reactance and the inductance component of the distributed constant line L21 other than the portion connected in parallel with the capacitor C21 are set so as to have a resonance point with respect to an arbitrary higher-order harmonic of the fundamental high frequency.

Here, the capacitor C21 is a distributed constant line L
The reactance of the portion connected in parallel to 21 is a combined reactance of the capacitor C21 and the inductance component of the distributed constant line L21 in the parallel portion, and the capacitance component and the inductance component cancel each other. As a result, the capacitance component of the capacitor C21 becomes smaller than the original capacitance value, but the distributed constant line L21
Must be set so that the inductance component is not greater than the capacitance component of the capacitor C21, and the parallel portion is a capacitance component.

The capacitor C21 and the distributed constant line L21
Will have a parallel resonance point, but at a frequency where this circuit is effective, this parallel part is set to have a capacitor component, so the resonance point of the series resonance circuit is lower than this parallel resonance point. Since the frequency is used, the operation and effect of the present invention are not hindered.

Even when the bent portion of the distributed constant line L21 is provided near the center of the line and the capacitor C21 is disposed near the center of the distributed constant line L21, since the resonance circuit has a resonance point as a resonance circuit portion, It has a harmonic control function and is realized as a trap circuit.

FIG. 2B is a plan view showing a resonance circuit portion having another configuration. L22 is a distributed constant line similar to L21. In this example, a U-shaped bent portion is not formed. . C22 is a capacitor (multilayer ceramic chip capacitor) mounted and connected on the distributed constant line L22, and is connected in parallel with the distributed constant line L22 by external electrodes C22b formed at both ends of the capacitor body C22a. Have been.

Thus, a capacitance component synthesized by the capacitance of the capacitor C22 connected in parallel to a part of the distributed constant line L22 and the inductance of the distributed constant line L22 in the part connected in parallel with the capacitor C22 is calculated. And the distributed reactance line L22 of the portion other than the portion connected in parallel with the capacitor C22.
Are set so as to have a resonance point with respect to any higher harmonic of the fundamental high frequency.

In this example, the reactance of the portion where the capacitor C22 is connected in parallel to the distributed constant line L22 becomes a small combined reactance because the inductance component of the distributed constant line L22 of the parallel portion is extremely small, and the capacitance component decreases. Is also small, and there is no influence of the parallel resonance point of the parallel portion of the capacitor C22 and the distributed constant line L22.

In such an example, the capacitor C22 may be arranged near the center of the distributed constant line L22.

FIG. 2C is a plan view showing a resonance circuit portion having still another configuration. L23 is a distributed constant line similar to L21, and a part thereof is formed by bending a portion into a U-shape. And a plurality of short-circuit lines L23
a, L23b and L23c are formed in a ladder shape. C23 is a capacitor (multilayer ceramic chip capacitor) connected to the bent portion of the distributed constant line L23 in the same manner as in FIG.
It is connected in parallel with the distributed constant line L23 by external electrodes C23b formed at both ends of 23a.

As a result, a composite having a capacitance component composed of the capacitance of the capacitor C23 connected in parallel with a part of the distributed constant line L23 and the inductance of the distributed constant line L23 in a part connected in parallel with the capacitor C23. The reactance and the inductance component of the distributed constant line L23 in a portion other than the portion connected in parallel with the capacitor C23 are set so as to have a resonance point for an arbitrary higher-order harmonic of the fundamental high frequency.

Here, in this embodiment, the capacitor C23
The reactance of the portion connected in parallel with the distributed constant line L23 is the capacitor C23 and the distributed constant line L23 of the parallel portion.
Is the combined reactance with the inductance component of
A plurality of short-circuit lines L are provided at the bent portion of the distributed constant line L23.
Since 23a, L23b and L23c are formed in a ladder shape, it is possible to adjust the inductance component of the parallel portion of the distributed constant line L23 by cutting a predetermined short-circuit line among them, and after connecting the capacitor C23. By adjusting the capacitance component of the parallel portion, a desired resonance point can be obtained for the resonance circuit portion.

Incidentally, also in this example, the distributed constant line L23
May be provided near the center of the line, and the capacitor C23 may be arranged near the center of the distributed constant line L23.

In FIGS. 2A to 2C, in order to adjust the capacitance value of the capacitor in order to set the resonance point of the resonance circuit portion to a desired value, for example, it is possible to replace the capacitor with a capacitor having a different capacitance value. Alternatively, the capacitance value may be adjusted using a variable capacitance capacitor.

Next, another example of the circuit configuration of the high frequency power amplifier of the present invention is shown in FIG. 3 in the same circuit diagram as FIG.

In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the difference from the example of FIG. 1 is that the drain (output electrode) of the high-frequency transistor Q11 and the current for output are A capacitor C15 'is connected in parallel to a part of the distributed constant line L13' constituting the bias circuit for supplying the drain (output electrode) of the high-frequency transistor Q11, and this capacitor C15 'and capacitor C15' are connected in parallel.
Are connected in parallel to each other by a distributed circuit L13 'and a bypass capacitor C16' to form a resonance circuit section D 'having a harmonic control function surrounded by a dashed line. It is the point that forms.

With such a high-frequency power amplifier of the present invention, similarly to the example shown in FIG. 1, the bias circuit B '
Has a resonance point for an arbitrary higher-order harmonic of the fundamental frequency by a resonance circuit section D 'constituted by a distributed constant line L13' and a capacitor C15 'connected in parallel to the distributed constant line L13'. The impedance appears to be 0 with respect to the higher-order harmonic, and is grounded. For example, F
In the case of a class power amplifier, by setting the resonance point to the second harmonic of the fundamental frequency, it is possible to remove the even-order, that is, the second harmonic of the fundamental frequency which is unnecessary in order to approximate the voltage waveform to a rectangular wave. As a result, in the drain which is the output of the high-frequency transistor Q11, the second harmonic component is reduced and the drain efficiency is improved.

In addition, 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.

The above embodiment has been described based on an example in which the high-frequency class F power amplifier has a harmonic control function for removing the second harmonic of the fundamental frequency.
The high frequency power amplifier of the present invention is not limited to these, and various changes 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 harmonic.
The present invention may be applied to other high-frequency power amplifiers other than the class power amplifier, and may be used for removing spurious harmonics contained in the output of the high-frequency power amplifier.

[0038]

According to the high frequency power amplifier of the present invention,
As a bias circuit for supplying a direct current to the output electrode of the high-frequency transistor, the bias circuit includes a distributed constant line and a capacitor connected in parallel to a part of the distributed constant line, and the output is determined by the length of the distributed constant line and the capacitance of the capacitor. A capacitor having a combined reactance component necessary to function as a part of a matching circuit, and a capacitance of a capacitor connected in parallel with a part of the distributed constant line, and a distributed constant line of a part connected in parallel with the capacitor A series resonance circuit is composed of a combined reactance having a capacitance component combined with the inductance of the distributed constant line in a portion other than the portion connected in parallel with the capacitor, and the series resonance frequency is set to the fundamental frequency. Because the resonance point for any higher harmonics
This bias circuit achieves the original purpose of supplying a DC current while functioning as a reactance component of a part of the output matching circuit, and also provides an output electrode of a high-frequency transistor for an arbitrary higher-order harmonic of the fundamental frequency. It becomes a grounded state when viewed from above, and also functions as a harmonic control circuit capable of removing any higher harmonics. As a result, it is not necessary 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 downsizing.

In this bias circuit, the capacitance component of the capacitor and the inductance component of the distributed constant line can be easily adjusted by adjusting the capacitance value of the capacitor and the length of the distributed constant line, respectively. The resonance point can be easily adjusted not only for higher harmonics but also for other high-frequency power amplifiers. It can also be used for the purpose of removing spurious harmonics included.

Therefore, according to the present invention, 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 downsizing. 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.

FIGS. 2A to 2C are plan views each showing an example of a configuration of a resonance circuit section of a bias circuit according to the high-frequency power amplifier of the present invention.

FIG. 3 is a circuit diagram showing another example of the circuit configuration of the high-frequency power amplifier of the present invention.

FIG. 4 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 B, B '... Bias circuit L13, L13': Distributed constant line (microstrip line) C15, C15 ': Capacitor

Claims (1)

[Claims] 1. A high-frequency transistor for amplifying a high-frequency input signal supplied to a control electrode and outputting the signal as a high-frequency output signal from an output electrode; An output matching circuit connected to the output electrode for matching to a desired output characteristic; a distributed constant line connected to the output electrode for supplying a direct current; A bias circuit comprising a capacitor connected in parallel to a part of the distributed constant line, the bias circuit having a combined reactance component necessary to function as a part of the output matching circuit, and A high-frequency power amplifier having a resonance point with respect to a higher-order harmonic of the fundamental frequency by a distributed constant line and the capacitor.