JP2927981B2 - Balanced microwave band amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balanced microwave band amplifier.

[0002]

2. Description of the Related Art In order to increase the output power level of a microwave band amplifier, a balanced type microwave band amplifier in which a pair of unit amplifiers are operated in parallel has been used. The unit amplifiers are connected in parallel to each other on the input side and the output side by a 90-degree hybrid.

[0003]

In the conventional balanced microwave band amplifier, when the operation level enters a saturation region, the operation becomes non-linear, and in addition to the fundamental frequency component f, the second harmonic 2f, the third harmonic 3f, ... Equal harmonic components are generated.

Referring to FIG. 5, in a balanced amplifier, an output hybrid 22 which is a load of a unit amplifier 21 is provided.
Are required 50Ω load for odd harmonic components such as fundamental wave f, third harmonic 3f,.
The load is not 50Ω for even harmonic components such as harmonics. Therefore, the even-order harmonic components are reflected by the hybrid 22 and return to the output side of the unit amplifier 21 to be mixed with the fundamental wave f. For example, the second harmonic component 2f is equal to the fundamental wave f of 2ff−f = f. Produces components of the same frequency. Since this component is out of phase with the fundamental wave component f amplified by the unit amplifier 21, there is a problem that a ripple occurs in the frequency characteristic in the combined output.

[0005]

SUMMARY OF THE INVENTION A balanced microwave band amplifier according to the present invention is a balanced microwave band amplifier having a 90-degree hybrid before and after a pair of unit amplifiers. And a resistor connected in parallel to each main line in parallel with each main line , a length of １ ／ wavelength for a second harmonic frequency component of a required frequency, one end connected to the resistor, and the other end connected to a high frequency. And a short-circuited line.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a configuration of the second harmonic wave absorbing circuits 9 and 10 in FIG.

Referring to FIG. 1, a pair of unit amplifiers 5,
6 are connected in parallel by a hybrid 7. The main lines 1 on the output sides of the unit amplifiers 5 and 6 are connected in parallel by a hybrid 8, and second harmonic wave absorbing circuits 9 and 10 are connected to these main lines, respectively.

As shown in FIG. 2, the second-harmonic absorption circuits 9 and 10 are connected in parallel with the main line 1 through a resistor 2 to provide a 1/4 wavelength for the fundamental wave and a 1 / wavelength for the second harmonic. One end of the line 3 having a length of two wavelengths is connected, and the other end of the line 3 is grounded at a high frequency by a capacitor 4 so that the second harmonic is absorbed by the resistor 2. For example, when the fundamental frequency is 12 GHz, the resistance value of the resistor 2 is 25Ω, the characteristic impedance of the line 3 is 70Ω, and the capacitance value of the capacitor 3 is 3.9 pF.

FIG. 3 shows a change in the sending end impedance ZA when the receiving end of the line 3 in FIG. 2 is short-circuited. Assuming that the wavelength is λ, the characteristic impedance of the line 3 and the length are Z and L, ZA = jZtanβL (.β = 2π / λ). The impedance ZA seen is infinite, and the second-harmonic absorption circuits 9 and 10 do not operate on the fundamental wave. Track 3
Is a line having a 波長 wavelength in the second harmonic component, the impedance ZA seen from the transmitting end becomes 0, and the second harmonic component flows into the second harmonic absorption circuits 9 and 10 and is absorbed by the resistor 2. Therefore, the fundamental wave passes through the main line 1 as it is, but the second harmonic component is absorbed by the second harmonic absorption circuits 9 and 10 and does not flow to the output-side hybrid 8 serving as a load. Does not occur. Therefore, the influence of the second harmonic component in the nonlinear region is eliminated.

FIG. 4 is an explanatory diagram in which the second harmonic wave absorbing circuits 9 and 10 absorb the second harmonic wave. Odd-order harmonic components such as fundamental wave components and third-order harmonic components flow toward the output-side hybrid 8, while even-order harmonic components such as second-order harmonic components pass through the second-harmonic absorption circuits 9 and 10. Flow, hybrid 8 does not flow.

[0012]

As described above, according to the present invention, in parallel with the main line on the output side of the unit amplifier, a 1/4 wavelength in the fundamental wave and a 1/2 harmonic component in the fundamental wave via the resistor. By providing a line that has the length of the wavelength and the receiving end is grounded at a high frequency with a capacitor or the like, even harmonic components such as the second harmonic component are absorbed without affecting the fundamental wave. Hold down the ripple of the frequency characteristic in the nonlinear region,
This has the effect that the amplitude deviation and the amplitude gradient can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of second harmonic absorption circuits 9 and 10 in FIG.

FIG. 3 is a diagram showing a change with respect to a length L of a transmission end impedance ZA of a line 3 in FIG. 2;

FIG. 4 is a diagram for explaining absorption of even-order harmonic components in the embodiment of FIG. 1;

FIG. 5 is a diagram for explaining mixing of a second harmonic component and a fundamental wave in a conventional balanced microwave band amplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main line 2 Resistance 3 Line 4 Capacitor 5,6 Unit amplifier 7,8 Hybrid 9,10 2nd harmonic absorption circuit

Continuing from the front page (72) Inventor Takahiro Asada 2-4-1-18 Shin-Yokohama, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Inside of NEC Aerospace Systems Co., Ltd. (56) References JP-A-61-100011 (JP, A) Hei 2-55721 (JP, U) Actually open Hei 2-134729 (JP, U)

Claims (1)

(57) [Claims] 1. A pair balanced microwave band amplifier having a 90 ° hybrid before or after the unit amplifier, connected to the main line of the each parallel with the main line of each of the output side of the unit amplifier of said pair And a line having a length of a half wavelength with respect to a second harmonic frequency component of a required frequency and having one end connected to the resistor and the other end short-circuited at a high frequency. Waveband amplifier.