JPH02182007A - High frequency amplifier circuit - Google Patents

Abstract

PURPOSE:To decrease the deviation in the amplitude in the overall passing characteristic and to attain broad band by providing a hybrid circuit having nearly opposite passing characteristic to that of the passing characteristic of the amplitude deviation to an output side of a high frequency amplifier when an input signal is amplified by the high frequency amplifier having a passing characteristic with the amplitude deviation. CONSTITUTION:An input side matching circuit 21, a FET 22, an output side matching circuit 23 and bias circuits 24, 25 form a high frequency amplifier 2, and a branch line hybrid 31 constitutes a hybrid circuit. Suppose that the input side matching circuit 21 and the output side matching circuit 23 have a double peak characteristic having resonance points at frequencies f1, f2. Thus, a signal whose amplitude versus frequency characteristic is flat between frequencies f1 and f2 is amplified by the FET 22 through the input side matching circuit 21 and the amplitude frequency characteristic shows a double peak at an output point of the output side matching circuit 23. A signal having the amplitude frequency characteristic is fed to a terminal A of the branch line hybrid 31 and extracted at a terminal B, then since the amplitude frequency characteristic of the branch line hybrid 31 is a single peak characteristic, the amplitude frequency characteristic between the frequencies f1 and f2 is made flat.

Description

[Detailed Description of the Invention] [Summary] For example, the purpose of this invention is to reduce the amplitude deviation of the overall pass characteristic and achieve a wide band in a high frequency amplifier circuit used in the transmitter of a 4-6 GHz multiplex radio device. When an input signal is amplified by a high frequency amplifier having a pass characteristic with an amplitude deviation, a hybrid circuit having a pass characteristic substantially opposite to the pass characteristic is provided on the output side of the high frequency amplifier.

(Industrial Application Field) The present invention relates to a high frequency amplification circuit used in a transmitting section of a multiplex radio device for example 4 to 5 GHz.

In recent years, the transmission capacity of multiplex radio equipment has increased.

From the point of view of effective use of frequencies, the adoption of multilevel modulation methods such as 64-quadrature amplitude modulation and common amplification methods that commonly amplify multiple carriers at the same time is progressing.

For this reason, the performance requirements for each circuit constituting a wireless device have become stricter, and it is desired that high-frequency amplifier circuits reduce the amplitude deviation of the pass characteristic, that is, the in-band amplitude deviation, and thereby widen the band.

[Prior Art] FIG. 5 is a block diagram of a conventional example, and FIG. 6 is an explanatory diagram of the operation of FIG. 5.

As shown in Fig. 5, the high-frequency amplifier is composed of, for example, a gallium arsenide field effect transistor (hereinafter abbreviated as PET),
Input side matching circuit 11. The output side matching circuit 13 is composed of a bias circuit vr14.15.

The input side matching circuit 11 is composed of, for example, a microstrip line, but is shown as a lumped constant circuit in FIG. 1 for the sake of simplicity.

Now, the input signal is passed through the hexagonal matching circuit 11 to the FE712.
After being amplified, the signal is output through the output side matching circuit 13, but the band of this high frequency amplifier is determined by the capability of the FET and the matching circuit.

- When making a high frequency amplifier broadband.

For example, a matching circuit is configured as shown below. That is, the resonance frequency of the input side matching circuit 11 and the output side matching circuit 13 is f
,, Determine the values of inductance L11 capacitor C1 and inductance L2 + capacitor c2 so that f. As a result, as shown in FIG. 6, the frequency f,
A bimodal characteristic is obtained in which the amplitude is maximum at f, and is convex downward between one frequency f I - f z, making it possible to widen the band of the high frequency amplifier.

[Problems to be Solved by the Invention] Here, if the input/output matching circuit is made to have bimodal characteristics, the high frequency amplifier will have a wider band, but this will increase the in-band amplitude deviation, and the amplitude required by the wireless device will increase. It becomes difficult to satisfy the deviation.

For example, when the 64 quadrature amplitude modulated waves have an amplitude modulation component, the amplitude of the amplitude modulation component changes in response to the in-band amplitude deviation, and the error rate deteriorates when demodulated on the receiving side. It should be noted that the number of multi-values must be increased (indeed, the band must be widened, and the deviation of the in-band amplitude characteristics must be reduced).

That is, there is a problem in that in order to cope with the increase in transmission capacity, the high frequency amplifier must have a wider band, and the in-band amplitude deviation must be reduced.

An object of the present invention is to reduce in-band amplitude deviation and achieve one wide band.

[Means to solve problems]

FIG. 1 shows a block diagram of the principle of the present invention.

In the figure, numeral 3 indicates a hybrid circuit having a pass characteristic almost opposite to the pass characteristic.

Then, the high print circuit is configured to be provided on the output side of the high frequency amplifier.

[Operation] The present invention connects the hybrid circuit 3 having a pass characteristic such that when the amplitude deviation of the pass characteristic of a high frequency amplifier is compensated for, the amplitude deviation after compensation falls within a predetermined range, on the input side of the high frequency amplifier, or By installing it on the output side, the high-frequency amplifier and hybrid circuit as a whole achieve a wide band and reduce the amplitude deviation of the one-pass characteristic.

〔Example〕

FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is an explanatory diagram of the operation of FIG. 2, and FIG. 4 is an example of a characteristic diagram of the hybrid circuit shown in FIG.

Here, the symbols in FIG. 3 indicate the waveforms of the portions with the same symbols in FIG. 2. In addition, an input side matching circuit 21PET 22.
Output side matching circuit 23. The bias circuits 24 and 25 are components of the high frequency amplifier 2, and the branch line hybrid 31.
indicates the components of the hybrid circuit. The operation of FIG. 2 will be described below with reference to FIG.

First, it is assumed that the input-side matching circuit 21 and the output-side matching circuit 23 exhibit bimodal characteristics with resonance points at frequencies f and f2, similar to the conventional example. For this reason, as shown in Figure 3-■, the frequency f,
A signal with a flat amplitude-frequency characteristic between ~f2 passes through the input-side matching circuit 21, is amplified by the FET 22, and is sent out from the output-side matching circuit 23, resulting in an amplitude-frequency characteristic as shown in Fig. 3-■. is bimodal and the in-band amplitude deviation is large.

When a signal with such an amplitude frequency characteristic is added to the terminal of the branch line hybrid 31 and taken out from the terminal B, the amplitude frequency characteristic of the hybrid 31 at that time becomes a single peak characteristic as shown in Fig. 3-■. , as shown in FIG. 3-■, the amplitude frequency characteristics between frequencies f and -f2 become flat, and the in-band amplitude deviation decreases.

Here, in FIG. 2, the branch line hybrid 31 is provided after the output side matching circuit, but the same effect can be obtained even if it is provided before the input side matching circuit.

Note that terminals C and D are terminated with 1, for example, 50Ω.

Furthermore, as shown in Fig. 4(a), when input is input from terminal A and taken out from terminal C, the amplitude characteristic of the branch line hybrid becomes a single peak that is gentler than that of terminal B on terminal B. Terminate 50Ω with 50Ω at the terminal.

Next, if an input/output side matching circuit is provided so that the amplitude frequency characteristic of the high frequency amplifier becomes unimodal, the amplitude frequency characteristic of the rat race type hybrid shown in Fig. 4(b) will have an inverse convex downward characteristic. If the output side matching circuit is connected to the terminal where the signal becomes, and the output side is taken out from the terminal C, the in-band amplitude deviation can be reduced.

Note that if it is taken out from terminal A to terminal B, it will have an upwardly convex single peak characteristic.

i.e. by using a hybrid circuit.

It is possible to reduce the in-band amplitude deviation of the high frequency amplifier and achieve a wider band.

It goes without saying that the same effect can be obtained even if a branch line hybrid is provided on the input side in the above explanation.

〔Effect of the invention〕

As described above in detail, the present invention has the effect of reducing in-band amplitude deviation and achieving one wider band.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the invention, Fig. 3 is an explanatory diagram of the operation of Fig. 2, and Fig. 4 is a characteristic diagram of the hybrid circuit in Fig. 2. Example, 5th
The figure shows a block diagram of a conventional example, and FIG. 6 shows an operation explanatory diagram of FIG. 5. In the figure, 2 indicates a high frequency amplifier, and 3 indicates a hybrid circuit. bite, l',, :', V, this full day of the moon, the cape, Choributsu Dtsu 7 figure 1 undiscovered Meitojishobu 1n block 2 figure 152 island Qy) movement i￥ i; l g month D33 Figure/42 Figure

Claims (1)

[Claims] When an input signal is amplified by a high frequency amplifier (2) having a pass characteristic with an amplitude deviation, a hybrid circuit (3) having a pass characteristic almost opposite to the pass characteristic is used as the output of the high frequency amplifier. A high frequency amplification circuit characterized in that it is configured to be installed on the side.