JPH04306906A - Balance type microwave band amplifier - Google Patents

Abstract

PURPOSE:To suppress a ripple in a frequency characteristic by providing a line whose length is 1/2 wavelength with respect to a 2nd harmonic and whose other terminal is connected to ground in terms of high frequency in parallel with a main line at an output side of a unit amplifier via a resistor. CONSTITUTION:Input terminals of a couple of unit amplifiers 5,6 are connected in parallel through a hybrid 7 and main lines 1 at an output side are connected in parallel through a hybrid 8. Each of 2nd harmonic absorption circuits 9,10 is connected to one terminal of a line 3 whose length is 1/4 wavelength with respect to a fundamental wave and 1/2 wavelength with respect to a 2nd harmonic via a resistor 2 in parallel with the main line 1. The other terminal of the line 3 is connected to ground via a capacitor 4 in terms of high frequency so that the 2nd harmonic wave is absorbed in the resistor 2. Thus, the fundamental wave passes through the main line without any change but the 2nd harmonic wave is absorbed in the 2nd harmonic absorption circuits 9,10 and is not given to the hybrid 8 at the output side being a load, then no mixture of the 2nd harmonic wave onto the fundamental wave is caused. Thus, the effect of the 2nd harmonic wave in a nonlinear region is avoided.

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 microwave band amplifier is used in which a pair of unit amplifiers are operated in parallel. Each unit amplifier is connected in parallel to each other by a 90 degree hybrid on each of the input side and output side.

0003

[Problems to be Solved by the Invention] In this conventional balanced microwave band amplifier, when the operating level enters the saturation region, nonlinear operation occurs, 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, a hybrid 22 on the output side is a load of a unit amplifier 21.
is the required 50Ω load for odd harmonic components such as the fundamental wave f, the third harmonic 3f, ..., but the second harmonic 2f, 4
For even-order harmonic components such as harmonics, etc., the load does not become 50Ω. For this purpose, the even-order harmonic components are reflected by the hybrid 22 and returned to the output side of the unit amplifier 21, and mixed with the fundamental wave f, for example, the second harmonic component 2.
f produces a component of the same frequency as the fundamental wave f, 2f-f=f. Since this component is out of phase with the fundamental wave component f amplified by the unit amplifier 21, there is a problem in that ripples occur in the frequency characteristics of the combined output.

[0005]

Means for Solving the Problems The balanced microwave band amplifier of the present invention has a 90 degree hybrid before and after a pair of unit amplifiers, in which the main line on the output side of the unit amplifier is and a resistor connected in parallel with 1/2 for the double harmonic component of the required frequency.
The line has a wavelength length and has one end connected to the resistor and the other end short-circuited in terms of high frequency.

[0006]

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

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

Referring to FIG. 1, a pair of unit amplifiers 5,
The input terminals of 6 are connected in parallel by a hybrid 7. Main lines 1 on the output side of unit amplifiers 5 and 6 are connected in parallel by a hybrid 8, and double wave absorption 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, and have a wavelength of 1/4 for the fundamental wave and a wavelength of 1/4 for the second harmonic. One end of a line 3 having a length of two wavelengths is connected, and the other end of the line 3 is grounded at high frequency by a capacitor 4, so that the second harmonic is absorbed by the resistor 2. For example, when the fundamental wave frequency is 12 GHz, the resistance value of the resistor 2 is 25 Ω, the characteristic impedance of the line 3 is 70 Ω, and the capacitance value of the capacitor 3 is 3.9 pF.

FIG. 3 shows a change in the transmitting end impedance ZA when the receiving end of the line 3 shown in FIG. 2 is short-circuited. The wavelength is λ
, when the characteristic impedance and length of the line 3 are Z and L, ZA=jZtanβL (however, β=2π/λ), so the impedance ZA seen from the sending end of the line 3 which has 1/4 wavelength in the fundamental wave becomes infinite, and the second harmonic absorption circuits 9 and 10 do not operate with respect to the fundamental wave. The line 3 becomes a line with a 1/2 wavelength for the second harmonic component, and the impedance ZA seen from the sending 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 hybrid 8 on the output side, which serves as a load, so mixing with the fundamental wave is required. does not occur. Therefore, the influence of the second harmonic component in the nonlinear region is eliminated.

FIG. 4 is an explanatory diagram of the second harmonic absorption circuits 9 and 10 absorbing the second harmonic. Odd-numbered harmonic components such as the fundamental wave component and 3rd harmonic component flow toward the hybrid 8 on the output side, but even-numbered harmonic components such as the 2nd harmonic component flow to the 2nd harmonic absorption circuits 9 and 10. Flow, Hybrid 8 does not flow.

0012

Effects of the Invention As explained above, the present invention provides a 1/4 wave wavelength for the fundamental wave and a 1/2 wave for the double wave harmonic component through a resistor in parallel with the main line on the output side of the unit amplifier. By providing a line with a length that corresponds to the wavelength and whose receiving end is grounded at high frequency with a capacitor, etc., even-order harmonic components such as second harmonic components are absorbed without affecting the fundamental wave. This has the effect of suppressing ripples in frequency characteristics in the nonlinear region and reducing amplitude deviations and amplitude slopes.

[Brief explanation of the drawing]

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

2 is a diagram showing the configuration of second harmonic absorption circuits 9 and 10 in FIG. 1. FIG.

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

FIG. 4 is a diagram for explaining absorption of even 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]

1 Main line 2 Resistance ３　　　Railway 4 Capacitor 5, 6 unit amplifier 7,8 Hybrid 9,10 Second harmonic absorption circuit

Claims (1)

[Claims] Claim 1. A balanced microwave band amplifier having a 90-degree hybrid before and after a pair of unit amplifiers, including a resistor connected in parallel with the main line on the output side of the unit amplifier, and a second harmonic of a desired frequency. A balanced microwave band amplifier comprising a line having a length of 1/2 wavelength relative to a wave component, one end of which is connected to the resistor, and the other end of which is short-circuited in terms of high frequency.