JPH0666127U - High frequency power amplifier circuit - Google Patents

Abstract

(57) [Summary] [Object] To provide a high-frequency power amplifier circuit capable of changing the resonance frequency of a series resonance circuit as a harmonic elimination means while maintaining a good matching state. [Structure] A capacitor C3 is connected in parallel to a series resonance circuit 21 provided as a harmonic wave removing means in the preceding stage of a coupling circuit 22 connected between the drain of the FET 1 and the output terminal 3. When the resonance frequency of the series resonance circuit 21 is changed, the value of the capacitor C3 is adjusted to
And the combined impedance of the series resonance circuit 21 is matched with the input impedance of the coupling circuit. [Effect] The resonance frequency of the series resonance circuit can be adjusted to the frequency of the harmonic without affecting the matching of the fundamental wave.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a high frequency power amplifier circuit, and more particularly to improvement of its output matching circuit.

[0002]

[Prior art]

 2. Description of the Related Art Conventionally, a high-frequency power amplifier circuit using a series resonance circuit in which an inductance element and a capacitance element are connected in series is known as a means for removing harmonics. An example of this is shown in FIG. In the figure, 1 is a field effect transistor (hereinafter referred to as FET), 2 is an output matching circuit, SL1 to SL4 are strip lines constituting an inductance element, and C1 and C2 are capacitors.

A predetermined voltage Vb is applied to the drain of the FET1 via the strip line SL1, and the source thereof is grounded. Further, the drain of the FET 1 is connected to the output terminal 3 via the output matching circuit 2.

The output matching circuit 2 includes the above-described strip lines SL2 to SL4 and capacitors C1 and C2. One end of the strip line SL2 is connected to the drain of the FET1 and the other end is grounded via the capacitor C1. . The strip line SL3 and the strip line SL4 are connected in series between the drain of the FET1 and the output terminal 3, and the connection point between the strip line SL3 and the strip line SL4 is grounded via the capacitor C2.

As a result, the stripline SL2 and the capacitor C1 form a series resonance circuit 21, and the striplines SL3 and SL4 and the capacitor C2 form a coupling circuit 22.

Further, in the coupling circuit 22, each element is arranged so that its input side impedance becomes an optimum drain load resistance of the FET 1 with respect to the fundamental frequency and has a high impedance with respect to harmonics. The value of is set. Further, in the series resonance circuit 21, the values of the respective elements are set so that the resonance frequencies match the second harmonic wave or the third harmonic wave, and the impedance thereof is matched to the input side impedance of the coupling circuit 22. Is set to.

According to the above-described configuration, the second harmonic or the third harmonic in the high frequency signal output from the drain of the FET 1 is removed by the series resonance circuit 21, and further the other harmonic component by the coupling circuit 22. Are removed and only the fundamental frequency component is output to the output terminal 3.

[0008]

[Problems to be solved by the device]

 However, in the above-described conventional high-frequency power amplifier circuit, since the inductance element of the series resonance circuit 21 is formed by the strip line SL2, if the width or the like of the strip line SL2 varies during manufacture, the resonance frequency of the strip line SL2 may change. Not only changes, but when the capacitance of the capacitor C1 is changed to adjust the resonance frequency, the impedance of the series resonance circuit 21 changes, the matching state with the coupling circuit 22 collapses, and the matching state of the fundamental wave changes. There was a problem of getting worse.

In view of the above problems, an object of the present invention is to provide a high frequency power amplifier circuit capable of changing the resonance frequency of a series resonance circuit as a means for removing harmonics while maintaining a good matching state. .

[0010]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a high frequency power amplifier circuit including an output matching circuit having a coupling circuit and a series resonance circuit in which an inductance element and a capacitance element are connected in series as harmonic elimination means. In, a high-frequency power amplifier circuit is proposed, in which a capacitance element connected in parallel to the series resonance circuit is provided.

[0011]

[Action]

 According to the present invention, for example, when the inductance element of the series resonance circuit is formed by the strip line, an error occurs in the width of the strip line, etc., and the inductance value becomes different from the design value. When the resonance frequency of the resonance circuit does not match the frequency of the harmonic to be removed, the value of the capacitor element of the series resonance circuit is adjusted to set the resonance frequency of the series resonance circuit to the frequency of the harmonic. To match. At this time, the impedance of the series resonant circuit with respect to the fundamental wave is different from the input side impedance of the coupling circuit, and the matching state is broken, but a capacitance element is connected in parallel with the series resonant circuit, and By adjusting the value, the combined impedance of the capacitance element and the series resonant circuit can be matched with the input impedance of the coupling circuit.

[0012]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment. In the figure, the same components as those in the conventional example described above are designated by the same reference numerals and the description thereof will be omitted. Further, the difference between the conventional example and the present embodiment is that the capacitor C3 is connected in parallel to the series resonance circuit 21.

As a result, even if an error occurs in the width of the stripline SL2 of the series resonance circuit 21 at the time of manufacture, and the inductance value thereof is different from the designed value, the capacitance of the capacitors C1 and C3 is reduced. The optimum matching state can be obtained by adjusting.

That is, when the resonance frequency of the series resonance circuit 21 does not match the frequency of the harmonic to be removed, for example, the frequency of the second harmonic, the value of the capacitance element C 1 of the series resonance circuit 21 is adjusted to set the series resonance circuit 21. The resonance frequency of the resonance circuit 21 is made to match the harmonic frequency. As a result, the impedance of the series resonance circuit 21 becomes the minimum value for the second harmonic output from the drain of the FET 1, and the current component of the second harmonic is short-circuited via the series resonance circuit 21. .

At this time, the impedance Z1 of the series resonant circuit 21 and the input impedance Z21 of the coupling circuit 22 with respect to the fundamental wave become different, and the matching state is broken, but by adjusting the value of the capacitor C3, The combined impedance Z of the capacitor C3 and the series resonance circuit 21 can be matched with the input side impedance Z21 of the coupling circuit 22, and an optimum matching state for the fundamental wave can be obtained.

[0016]

[Effect of device]

 As described above, according to the present invention, when the resonance frequency of the series resonance circuit is changed, the value of the capacitance element connected in parallel to the series resonance circuit is changed to combine these combined impedances into a coupling circuit. It is possible to adjust the resonance frequency of the series resonance circuit while maintaining an optimum matching state with respect to the fundamental wave, since it can be matched with the impedance of the series resonance circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional example.

[Explanation of symbols]

1 ... FET, 2 ... Output matching circuit, SL1 to SL4 ... Strip line (inductance element), C1 to C3 ... Capacitor, 3 ... Output terminal.

Claims (1)

[Scope of utility model registration request] 1. A high-frequency power amplifier circuit including an output matching circuit having a coupling circuit and a series resonance circuit formed by connecting an inductance element and a capacitance element in series as a harmonic elimination means, wherein A high-frequency power amplifier circuit, comprising a capacitance element connected in parallel.