JPH0528131U - Automatic transmission power control circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] A rising transient response of an automatic transmission power control circuit in which the transmission output is kept constant by a gain control voltage obtained from the transmission output in which the transmission carrier is amplitude-modulated by the transmission ON signal and power amplified. Improve. A DC voltage b obtained from a low pass filter 7 after detecting a transmission output of a power amplifier 4 and a reference voltage from a reference voltage generator 8 by a transmission ON signal a are differentiated by a differentiating circuit 10 to obtain a DC voltage b. The voltage obtained by adding the voltage c having the opposite characteristic by the adder 11 is supplied to the power amplifier 4 as the gain control voltage d so that the stable transmission output e can be obtained at the same time as the transmission is turned on.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an automatic transmission power control circuit (APC) circuit of a transmitter, and relates to improvement of transient response at the start of transmission.

[0002]

[Prior Art]

 FIG. 3 shows an example of the configuration of a general automatic transmission power control circuit of a low power stage modulation type amplitude modulation (AM) transmitter. In the figure, a carrier wave generated by an oscillator (OSC) 1 of a synthesizer or the like is input to a switch (SW) 2 and is turned on by a transmission on signal (this signal causes a transmitter to change from a standby state to a transmission state). .

The switch 2 controls transmission on / off. The output of the switch 2 is input to the modulator 3 and is modulated by the modulation signal. The modulated carrier wave from the modulator 3 is input to the power amplifier 4, amplified to a predetermined power, and output.

This power amplifier is a variable gain amplifier, and the gain is controlled by the APC control voltage which is the output of the low pass filter (LPF) 7. This is to obtain a constant transmission output by compensating for gain variations due to differences in temperature, frequency, and gain of the power amplifier itself (individual difference).

The output of the power amplifier 4 passes through the directional coupler (DC) 5 and becomes a transmission output. The directional coupler 5 extracts a part of the transmission output and outputs it to the detector 6.

The detector 6 outputs a voltage proportional to the transmission output, but since the transmission output is AM-modulated, an envelope component of the modulation signal appears in the output. Therefore, the LPF 7 removes the modulation component of the envelope and generates a gain control voltage proportional to the average power. The gain control voltage controls the gain of the power amplifier 4 to keep the transmission output constant. FIG. 4 is a waveform diagram of each part showing a transient response of a transmission output waveform when such a conventional automatic transmission power control circuit is used. The modulation component is omitted in FIG. 4 for the sake of clarity. In FIG. 4, a is a transmission ON signal, and the transmitter is in the transmission state at point A. b is the waveform of the transmission output. When the transmission is started at the point A and the switch 2 is turned on, the transmission output is the maximum output C of the power amplifier 4. This is because there is no output from the LPF 7 at point A immediately after the start of transmission, as shown by the waveform c, and the voltage output rises with a delay due to the time constant of the LPF 7.

Therefore, since the control voltage (low voltage) that maximizes the gain is generated in the power amplifier 4 after the start of transmission, the power amplifier 4 is in the maximum gain state. After that, the specified output D is obtained after a lapse of time (time from A to B) substantially equal to the time constant of the LP F7.

[0008]

[Problems to be solved by the device]

 For this reason, the output becomes transiently excessive, and the modulation component is also distorted, so that communication immediately after the start of transmission cannot be performed normally. The object of the present invention is to eliminate the excessive output and distortion distortion of the transmitter transiently generated immediately after the start of transmission, and to obtain a stable transmission output immediately after the start of transmission. It is to provide a power control circuit.

[0009]

[Means of the Invention for Solving the Problems]

 In the automatic transmission power control circuit of the present invention, the transmission carrier is amplitude-modulated by the transmission ON signal, the transmission output is sent out by the power amplifier, and a part of the transmission output is detected and proportional to the transmission average power obtained by the low-pass filter. In the automatic transmission power control circuit configured to apply a voltage to the power amplifier as a gain control voltage to keep the transmission output constant, an output rising characteristic of the low-pass filter is input by inputting a predetermined reference voltage by the transmission ON signal. A differentiating circuit that outputs a voltage waveform having a characteristic opposite to that of the above, and an adder that adds the output of the differentiating circuit and the output of the low-pass filter and outputs the gain control voltage given to the power amplifier. The configuration is such that the desired transmission output is obtained immediately after the transmission ON signal is applied. It

[0010]

【Example】

 FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention. In FIG. 1, the circuits 1 to 7 are the same as in the conventional case of FIG. FIG. 2 is a voltage waveform diagram of each part showing a transient response from the start of transmission by the transmission ON signal to the stabilization of the transmission output. Also in FIG. 2, the modulation component is omitted for the sake of clarity. In FIG. 2, when transmission is started from the point A by the transmission on signal a, the output of the LPF 7 shows a voltage waveform as shown by b due to its time constant. Here, the adder 11 adds the output of the differentiating circuit 10 for generating a voltage waveform opposite to the rising voltage waveform of the LPF 7 and the output of the LPF 7.

The output waveform of the adder 11 is shown in FIG. The initial voltage of the output of the differentiating circuit 10 is obtained by the reference voltage from the reference voltage generator 8. The trigger is obtained by closing the switch (SW) 9 with a transmission ON signal. The setting of the reference voltage is adjusted to the gain control voltage (output of the adder 11) when the transmitter is producing the specified output. When there is an error between this reference voltage and the output of the adder 11 after a sufficient time equal to or longer than the time constant of the LPF 7, for example, when the reference voltage is high, the waveform becomes as shown by the broken line in FIG. However, the fluctuation is smaller than before.

Further, the error of the reference voltage can be made extremely small by adding a voltage generating circuit corresponding to the frequency characteristic and a correction circuit generating a voltage proportional to temperature and adding the output to the reference voltage output. . As described above, as shown in e of FIG. 2, a desired stable transmission output waveform can be obtained immediately after the start of transmission.

[0013]

[Effect of the device]

 By implementing the present invention, the transient characteristics at the transmission start-up are improved, the modulation wave is prevented from being lost at the start-up of the transmitter, the distortion rate is improved, and the equipment connected to the next stage of the transmitter is prevented from being destroyed. It has a great effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform chart of each part of FIG.

FIG. 3 is a block diagram of a conventional circuit configuration.

FIG. 4 is a waveform diagram of each part of FIG.

[Explanation of symbols]

 1 carrier wave oscillator 2 switch 3 amplitude modulator 4 power amplifier 5 directional coupler 6 detector 7 LPF (low-pass filter) 8 reference voltage generator 9 switch 10 differentiator circuit 11 adder

Claims (1)

[Scope of utility model registration request] 1. A transmission carrier is amplitude-modulated by a transmission ON signal, a transmission output is transmitted by a power amplifier, and a voltage proportional to the transmission average power obtained by a low-pass filter is detected by detecting a part of the transmission output and gain control is performed. In an automatic transmission power control circuit configured to be given to the power amplifier as a voltage to keep the transmission output constant, a predetermined reference voltage is input by the transmission ON signal and a characteristic opposite to the output rising characteristic of the low-pass filter. A transmission ON signal, and a differential circuit that outputs a voltage waveform as described above, and an adder that adds the output of the differential circuit and the output of the low-pass filter and outputs the gain control voltage to be applied to the power amplifier. An automatic transmission power control circuit, characterized in that a desired transmission output is obtained immediately after the voltage is applied.