JPH0446491B2 - - 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 a transmitter and the like in rural communication between TDMA communication ground stations.

(Prior Art) FIG. 8 is a block diagram of a conventional high frequency power amplifier circuit of this type. This power amplifier circuit controls the output waveform in order to prevent the spectrum of the transmission output signal from expanding to the extent that it adversely affects other transmission channels or the receiving channel of the own station due to burst switching. In an output with little spectral spread, the rise and fall of the envelope are gentle, and FIG. 7 shows an example of such a preferable envelope. In the high frequency power amplifier circuit shown in FIG. 8, the input level control circuit 10 attenuates the input high frequency signal 121 according to the level control signal 104 and outputs an attenuated high frequency signal 110. The amplifier 2 power amplifies the attenuated high frequency signal 110 and outputs a high power high frequency signal 102. Detector 3
performs envelope detection on the high power high frequency signal 102 and outputs an envelope signal 103. The reference envelope signal generating circuit 5 generates a DC reference envelope signal 105 having a positive half or a negative half of the waveform shown in FIG.
Reference envelope signal 105 is the desired waveform for envelope signal 103. The comparison circuit 4 outputs a level control signal 104 having a waveform of a radio wave difference between the envelope signal 103 and the reference envelope signal 105. Level control signal 104 represents the error of envelope signal 103 relative to reference envelope signal 105. The circuit of FIG. 8 thus constitutes a closed loop and operates so that the envelope of the high power, high frequency signal 102 is similar to the waveform of the reference envelope signal 105.

FIG. 9 is a circuit diagram of the input level control circuit 10. In the conventional input level control circuit, two pin diodes 15 are connected in series between an input terminal 31 and an output terminal 32, as shown in this figure.
The circuit shown in this figure has hysteresis, as shown in the characteristic diagram of FIG. 3, in that the pin diode 15 does not turn on until it reaches a certain bias value, and then suddenly turns on when it reaches a certain bias value.
Therefore, when the input high frequency signal 121 to the input level control circuit 10 enters the hysteresis region, the pin diode 15 suddenly turns on and the power amplifier 2
As the input level to the power amplifier 2 increases rapidly, the waveform of the output 102 of the power amplifier 2 becomes steep as shown in FIG. I get tired.

(Problem to be Solved by the Invention) Conventionally, in order to suppress the spread of this spectrum, the control signal 1 is controlled so as to avoid the hysteresis region.
However, since the pin diode 15 cannot be completely turned off, the envelope of the high power high frequency signal 102 has a waveform as shown in FIG.
Therefore, in the conventional circuit, it was not possible to maintain a dynamic range of the carrier leak ratio during burst-on and burst-off. As described above, the conventional high frequency power amplifier circuit has a problem in that the spectrum spreads greatly during burst switching of a high frequency signal.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a high frequency power amplifier circuit in which the spectrum spread is small during burst switching of a high frequency signal.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides an input level control system that applies attenuation to an input high frequency signal according to a level control signal and outputs an attenuated high frequency signal. a circuit, an amplifier that amplifies this attenuated high frequency signal and outputs a high power high frequency signal, a detector that detects this high power high frequency signal and outputs an envelope signal of the high power high frequency signal, and the envelope signal. a circuit for generating a reference envelope signal representing an envelope that rises gently and falls smoothly; and a comparison circuit for generating the level control signal representing a difference in waveform between the envelope signal and the reference envelope signal. The input level control circuit includes a point contact type silicon diode and a pin diode connected in series between an input terminal for the input high frequency signal and an output terminal for the attenuated high frequency signal. It is characterized by

(Example) Next, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention. In this embodiment, the input 101 to the power amplifier 2 is controlled by the input level control circuit 1 in accordance with the reference envelope signal 105 having gentle rising and falling waveforms generated by the reference envelope signal generating circuit 5. Further, the output 102 of the amplifier 2 is envelope-detected by the detector 3, and the output 103 of the detector 3 is compared with the output 105 of the reference envelope signal generation circuit 5 by the comparator circuit 4. The error signal is input to the input level control circuit 1 as a level control signal 104 to operate, forming a closed loop, and the envelope waveform of the output signal 102 of the power amplifier 2 is input to the reference envelope signal generation circuit 5.
By controlling the signal to be similar to the output signal 105 of the output signal 105, the spread of the spectrum of the output signal 102 during burst switching is suppressed.

The input level control circuit 1 in this embodiment has a point contact type silicon diode 6 and a two-stage pin diode 7 connected in series between an input terminal 31 and an output terminal 32, as shown in the circuit diagram in FIG. By adding a point contact type silicon diode 6, compared to the conventional input level control circuit 10 consisting of two stages of pin diodes,
As shown in the characteristic diagram in FIG. 4, hysteresis is significantly reduced.

In this way, if this embodiment is used, the comparator circuit 4
Since the pin diode can be controlled from an on state to an almost off state by the level control signal 104 from the high power high frequency signal 102, the envelope waveform becomes as shown in FIG. The high-power high-frequency signal 102 with an envelope waveform as shown in FIG. 7 has smooth rising and falling waveforms without spectrum expansion, and has a sufficient dynamic range of output ratio between burst-on and burst-off. It's taken away.

(Effects of the Invention) As explained above, according to the present invention, the spread of the spectrum during burst switching of a high frequency signal is small, and furthermore, the burst switching
It is possible to provide a high frequency power amplification circuit that significantly improves the carrier leakage ratio when turned off.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a circuit diagram showing a specific example of the input level control circuit in the embodiment shown in FIG. FIGS. 5 and 6 are diagrams showing examples of the envelope waveform of high-frequency output in a conventional high-frequency power amplifier circuit. FIG. FIG. 1 is a diagram showing an example of the envelope waveform of the high frequency output in the embodiment; FIG. 8 is a block diagram showing an example of a conventional high frequency power amplifier circuit;
This figure is a circuit diagram showing an input level control circuit in the conventional high frequency power amplifier circuit of FIG. 8. 1, 10...input level control circuit, 2...amplifier,
3... Detector, 4... Comparison circuit, 5... Reference envelope signal generation circuit, 6... Silicon diode, 7, 15...
Pin diode, 8...control signal application circuit, 9...coil.

Claims (1)

[Claims] 1. An input level control circuit that applies attenuation to an input high frequency signal according to a level control signal and outputs an attenuated high frequency signal, an amplifier that amplifies this attenuated high frequency signal and outputs a high power high frequency signal, and this high power high frequency signal. a detector that detects the high-power high-frequency signal and outputs an envelope signal of the high-power high-frequency signal; a circuit that generates a reference envelope signal that represents a gently rising and gently falling envelope that is desired as the envelope signal;
A high frequency power amplification circuit comprising a comparator circuit that generates the level control signal representing a difference in waveform between the envelope signal and the reference envelope signal, wherein the input level control circuit is connected to an input terminal of the input high frequency signal and the attenuator. A high-frequency power amplifier circuit comprising a point-contact type silicon diode and a pin diode connected in series between a high-frequency signal output terminal.