JPH046131B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high frequency power amplification circuit used in microwave band communication equipment and the like.

[Conventional technology]

Figure 2 shows, for example, the published patent publication No. 58-159002,
It is a circuit diagram of a conventional high frequency power amplifier circuit shown in "Semiconductor circuit for high frequency power", 1 is a base bias voltage supply terminal, 2 is a collector bias voltage supply terminal, 3 is a first RF choke coil, 4
is the second RF chain coil, 5 is the input side RF terminal, 6 is the input side DC blocking capacitor, 7 is the input side impedance matching line, 8 is the input side impedance matching variable capacitor, 9 is the base of the transistor Tr, 10 is the Emitter of transistor Tr, 1
1 is the collector of the transistor Tr, 12 is an output side impedance matching line, 13 is an output side DC blocking capacitor, 14 is an output side RF terminal, 15 is a variable capacitor for output side impedance matching, 16 is a strip line, and 17 is a capacitor. be.

Here, matching between the input impedance between the base and emitter of the transistor Tr and the input side RF terminal (typically 50Ω) is achieved by adjusting the input side impedance matching line 7 and the input side impedance matching variable capacitor 8. , are configured so that matching can be achieved at the fundamental wave.

Furthermore, matching between the output impedance between the collector and emitter of the transistor Tr and the output side RF terminal (typically 50Ω) can be achieved by adjusting the output side impedance matching line 12 and the output side impedance matching variable capacitor 15. It is configured so that matching can be achieved using the fundamental wave.

Note that the length lx of the strip line 16 is a quarter wavelength of the operating fundamental frequency.

With this configuration, the impedance looking into the strip line 16 from node a in FIG.
On the assumption that the reactance of the capacitor 17 is sufficiently small, Zin becomes ZinjZ ₀ ·tan2πlx/λeff.

Here, Z ₀ is the characteristic impedance of the strip line 16, and λeff is the propagation wavelength of the strip line. Therefore, impedance Zin is lx=λeff/4 for the fundamental wave, so Zin=j·Z ₀ ·tanπ/2, which becomes infinite. However, for even harmonics, for example, the second harmonic, the impedance Zin has a relationship of lx = 1/4 (2λeff) because the wavelength is halved, so Zin = jZ ₀ tanπ, and the node a, that is, the transistor output side The impedance looking into the strip line 16 is zero.

Therefore, the impedance Z _l looking into the load from the transistor output side is always Z _l =0 for even harmonics of the fundamental wave.

Further, for the third harmonic of the fundamental wave, the impedance Zin=jZ ₀ tan3/2π, and Zin=−∞.

Therefore, for odd harmonics of the fundamental wave,
Zin=±∞.

By the way, as a method of increasing the efficiency of a transistor amplifier, there is a method of operating the transistor in class F mode.

The conditions for F-class operation are as follows (),
().

() For even harmonics of the fundamental wave, impedance Z _l looking into the load from the transistor output side
is always 0.

() For odd harmonics of the fundamental wave, impedance Z _l looking into the load from the transistor output side
is always infinite.

In other words, in the conventional high-frequency power amplifier circuit shown in FIG. 2, since the impedance Zin looking into the strip line 16 from node a is ±∞ with respect to the odd gray harmonics of the fundamental wave, the impedance looking into the load from the transistor output side Z _l is determined by the output side impedance matching line 12 and the output side impedance matching variable capacitor 15, and Z _l of odd harmonics is ∞
It won't be. Therefore, the conventional high frequency power amplifier circuit shown in FIG. 2 satisfies the above condition (), but does not satisfy the above condition ().

[Problem that the invention seeks to solve]

As described above, the conventional high-frequency power amplifier circuit does not simultaneously satisfy the above conditions () and () for class F operation, and therefore has the problem that the efficiency cannot be made sufficiently high.

In order to solve this problem, the present invention aims to obtain a high frequency power amplifier circuit that satisfies the above condition (), can make the impedance Z _l of the third harmonic wave ∞, and satisfies part of the condition (). With the goal.

[Means for solving problems]

Therefore, in the high frequency power amplification circuit according to the present invention, a high frequency signal is inputted to the input terminal of the amplification element via the input side impedance matching circuit, and is amplified from the output side of the amplification element via the output side impedance matching circuit. In a high-frequency power amplifier circuit that outputs a high-frequency signal, a short-circuit means for short-circuiting the second harmonic or all even-numbered harmonics and a short-circuiting means for short-circuiting the second harmonic or all even harmonics are provided between the output side of the amplification element and the output side impedance matching circuit, and The inductor resonates in series with the first
A third harmonic parallel resonant circuit consisting of a series circuit of capacitors and a second capacitor connected in parallel to the series circuit and having a capacity approximately 1/8 of the first capacitor is provided. It is something.

[Effect]

In the high frequency power amplifier circuit according to the present invention, a triple harmonic parallel resonant circuit in which the inter-terminal impedance is 0 at the fundamental wave and ∞ at an angular frequency three times the fundamental wave is connected to the output side of the amplification element and the output side impedance matching circuit. Since the impedance _Zl considering the load of the amplification element can be set to ∞ for an angular frequency three times that of the fundamental wave. Note that at this time, the impedance Z _l of the fundamental wave looking into the load from the output side of the amplification element does not change by loading the triple parallel resonant circuit.

Therefore, when class F operation is performed, the efficiency increases for both even harmonics and odd harmonics of the fundamental wave.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a high frequency power amplifier circuit according to the present invention. In Fig. 1, 18 is an inductor;
19 is the first capacitor for resonance, 20 is the second capacitor for resonance, and 21 is the inductor 18 and the first capacitor.
This is a triple harmonic parallel resonant circuit composed of a series circuit consisting of a capacitor 19 and a second capacitor 20 connected in parallel to this series circuit.

Here, the inductance of the inductor 18 is
L ₁ , the capacitance of the first capacitor 19 is C ₁ , and the capacitance of the second capacitor 20 is C ₃ .

Let the angular frequency of the fundamental wave be ω ₁ , and the inductance
L ₁ and the capacitance C ₁ of the first capacitor shall be determined to satisfy the following equation (1).

In addition, the first capacitor C ₁ and the second capacitor C ₃
shall be determined so as to satisfy the following equation (2).

C ₁ = 8・C ₃ ...(2) Admittance between node b and node c in Figure 1
Y _bc is expressed by the following equation (3).

Y _bc = j(ωC ₃ +ωC ₁ /1−ω ² C ₁ L ₁ ) ...(3) At the fundamental wave (angular frequency ω ₁ ), from equation (1), ω ² ₁ C ₁ L ₁
= 1, so Y _bc (ω ₁ ) = ∞ For the third harmonic (angular frequency 3ω ₁ ), by substituting equation (2) into equation (3) and using the relationship ω ² ₁ C ₁ L ₁ = 1, we get Y _bc (3ω ₁ )=0.

From the above, the impedance Z _l looking into the load from the output side of the transistor Tr is infinite for the third harmonic wave, and the fundamental wave is not affected by loading the resonant circuit.

Note that the impedance looking into the load from the output side of the transistor Tr is zero for even harmonics, similar to the conventional high frequency power amplifier circuit, due to the strip line 16 as the short circuit means.

The high-frequency power amplifier circuit according to the present invention can make the impedance Z _l of the third harmonic wave ∞ of the above condition ( ) for transistor F class operation and simultaneously satisfy a part of the condition ( ), so Higher efficiency compared to amplifier circuits.

In addition, the first capacitor 19 and the second capacitor 2
0 can block direct current, so the direct current blocking capacitor 13 of the conventional high frequency power amplifier circuit
becomes unnecessary.

Note that in the above embodiment, a transistor was used as the amplification semiconductor element, but the present invention is not limited to this, and a FET (field effect transistor) may also be used.

〔Effect of the invention〕

As explained above, this invention inputs a high frequency signal to the input end of an amplification element via an input side impedance matching circuit, and outputs an amplified high frequency signal from the output side of the amplification element via an output side impedance matching circuit. In a high-frequency power amplification circuit, a short-circuit means for short-circuiting the second harmonic or all even harmonics and a series resonance with respect to the fundamental frequency are provided between the output side of the amplification element and the output side impedance matching circuit. A triple harmonic parallel resonant circuit consisting of a series circuit of an inductor and a first capacitor, and a second capacitor connected in parallel to the series circuit and having a capacity of about 1/8 of the first capacitor is provided. Therefore, there is an advantage that the efficiency is higher than that of a conventional amplifier that satisfies the condition for operating the transistor in class F only for even-numbered harmonics.

Further, since direct current can be blocked by the two capacitors of the resonant circuit, there is an advantage that the conventional direct current blocking capacitor is not required.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a high frequency power amplifier circuit according to the present invention, and FIG. 2 is a circuit diagram of a conventional high frequency power amplifier circuit. In the figure, 1 is the base bias voltage supply terminal, 2 is the collector bias voltage supply terminal, and 3 is the first RF
Chi York coil, 4 is the second RF Chi York coil,
5 is an input side RF terminal, 6 is an input side DC blocking capacitor, 7 is an input side impedance matching line (circuit), 8 is a variable capacitor for input side impedance matching,
Tr is a transistor (amplification element), 9 is the base of the transistor (input end), 10 is the emitter of the transistor, 11 is the collector of the transistor (output end), 12 is the output side impedance matching line (circuit), 14 is the output side RF terminal, 15 is a variable capacitor for output side impedance matching, 16 is a strip line, 17 is a capacitor, 18 is an inductor, 1
9 is the first capacitor, 20 is the second capacitor, 2
1 is a triple harmonic parallel resonant circuit. It should be noted that the same or corresponding parts in the drawings are designated by the same reference numerals.

Claims (1)

[Claims] 1. A high-frequency signal inputting a high-frequency signal to the input end of an amplification element via an input-side impedance matching circuit, and outputting an amplified high-frequency signal from the output side of the amplification element via an output-side impedance matching circuit. In the power amplification circuit, a shorting means for shorting the second harmonic or all even-numbered harmonics and an inductor that resonates in series with the fundamental frequency are provided between the output side of the amplification element and the output side impedance matching circuit. and the first
A third harmonic parallel resonant circuit consisting of a series circuit of capacitors and a second capacitor connected in parallel to the series circuit and having a capacity approximately 1/8 of the first capacitor is provided. High frequency power amplifier circuit.