JPS623929Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power control circuit suitable for controlling the transmission power of a transmitter of a wireless communication device to a constant level. In particular, the present invention relates to an automatic power control circuit that can easily read fluctuations in the amplification degree of an amplifier and that does not send out excessively high level signals when the signal is interrupted.

In the conventional automatic power control circuit of this type, the transmission output level is stabilized by the function of the power control circuit, so that the decrease in amplification expected at the end of the life of the transmission tube cannot be detected from the transmission output level. Tubes used in normal communications equipment are often replaced after a certain period of use to maintain good reliability of the power amplifier, regardless of the quality of the tube, but transmitting tubes in satellite communications are expensive. It is often used while monitoring the condition until the characteristics of the transmitting tube deteriorate. Monitoring the amplification of a transmitting tube is important because the life of the transmitting tube is reflected in a decrease in its amplification.

FIG. 1 is a system diagram showing a conventional automatic power control circuit. A signal supplied to the input terminal 1 passes through a voltage controlled attenuator 2, is amplified by an amplifier 3, and is sent out from an output terminal 4. A part of the output signal is taken out at the output terminal of the amplifier 3, the level is detected by the detector 5, and the detected signal voltage is compared with the output voltage of a separately provided reference voltage source 8 by the comparator amplifier 7, and the error signal is controlled. Voltage controlled attenuator 2 via system switch 9
will be given negative feedback. The error signal controls the voltage controlled attenuator 2 so that the output voltage of the reference voltage source 8 and the detection signal voltage of the detector 5 are equal in steady state. Therefore, the output level of the amplifier 3 is determined by the output voltage of the reference voltage source 8, and at the same time is stabilized at a constant level.

The alarm circuit 6 monitors the detection signal voltage of the detector 5 and indirectly determines the presence or absence of the transmission signal. If the transmission signal disappears, the switch 9 is opened, and the amount of attenuation of the voltage-controlled attenuator 2 is fixed. As controlled by the output voltage of bias 10, and if there is a transmit signal,
The switch 9 is closed and the output signal of the comparison amplifier 7 is superimposed on the output signal of the fixed bias 10. The output voltage of the fixed bias 10 is set such that a standard output level is obtained at the output terminal 4 when the switch 10 is open. The alarm circuit 6, the switch 9, and the fixed bias 10 are configured such that when the transmission signal is interrupted, if the switch 9 is always closed, the amount of attenuation of the voltage-controlled attenuator 2 becomes the minimum while the transmission signal is interrupted, and then the transmission is interrupted. An excessive transmission signal appears at the output terminal 4 at the moment the transmission starts, so if there is no transmission signal, set the attenuation amount of the voltage-controlled attenuator 2 to the standard value with the output voltage from the fixed bias 10, and then start transmission. It is used to prevent the occurrence of excessive transmission signals, which is sometimes expected.

In the conventional circuit shown in FIG. 1, the amount of attenuation of the voltage-controlled attenuator 2 can be measured by monitoring the control voltage applied to the voltage-controlled attenuator 2. Control attenuator 2
The controlled voltage of the amplifier 3 is recorded and compared with the measured controlled voltage to measure the change in amplification degree of the amplifier 3 over time. In this method, the controlled voltage is recorded when the tube is replaced, and the amount of change in amplification is determined by calculation, so the measurement is troublesome, and if the measurement is not performed when the tube is replaced, subsequent measurements will not be possible. Ta.

Furthermore, in the conventional circuit shown in FIG. 1, when there is no transmission signal, the output signal of the comparator amplifier 7 sends out a voltage that minimizes the amount of attenuation of the voltage controlled attenuator 2, and when transmission is started, the switch 9 There is also the drawback that the attenuation amount of the voltage controlled attenuator 2 becomes small at the moment when the voltage controlled attenuator 2 is closed, and excessive power is sent out.

This invention directly displays the change in the amplification level of the amplifier on the meter, making it easy to measure the change in amplification level, and prevents the transmission of an excessively high transmission signal when the transmission signal is interrupted. The purpose is to provide a control circuit.

Examples will be described below. FIG. 2 is a diagram showing the configuration of an apparatus according to an embodiment of the present invention. The output signal of the comparator amplifier 2 is connected to the switch 9 via a bipolar voltage-to-current converter 11 (hereinafter abbreviated as current converter) and a bipolar ammeter 12, and is further connected to the switch 9 in parallel with the switch 9. The feature is that a resistor 13 having resistance is connected. The rest of the structure is the same as the conventional example shown in FIG.

When replacing the tube of the amplifier 3, first adjust the fixed bias output voltage after replacement to obtain the required level at the output terminal 4, and then adjust the output of the reference voltage source 8 so that it is the same as the output voltage of the detector 5. adjust the voltage,
After that, the automatic power control system is closed.

If the amplification degree of the amplifier 3 does not change, the controlled voltage of the voltage controlled attenuator 2 will not change at all whether the automatic power control system is opened or closed. No current flows out,
Ammeter 12 shows zero. Next, when the amplification degree of the amplifier 3 increases, the current converter 11 absorbs some or all of the current flowing to the voltage controlled attenuator 2, so the ammeter 12 displays a negative value and the amplifier 3
shows an increase in the degree of amplification. Further, when the amplification degree of the amplifier 3 decreases, the current converter 11 is changed to the voltage controlled attenuator 2.
Since the current flowing through the amplifier 3 increases, the ammeter 12 displays a positive value, indicating a decrease in the amplification degree of the amplifier 3.
The magnitude of the fluctuation in the amplification degree is expressed as the magnitude of the deflection of the pointer of the meter 12, so the amplification degree of the amplifier 3 can be easily monitored.

Furthermore, when the transmission signal is intermittent, the following operation prevents the transmission of an excessively high level signal. In other words, when there is no transmission signal, the alarm circuit 6 is activated by the switch 9.
At the same time as opening, the output current of the current converter 11 is set to zero. In this case, resistor 1 with a high resistance value
3, fixed bias 10 and current converter 11
Since the output terminal of current converter 1 is connected,
The output voltage of 1 is the same as the voltage of fixed bias 10. Next, when transmission is started, the alarm circuit 6
First, close the switch 9. At this instant, the voltage of the fixed bias 10 and the output voltage of the current converter 11 are the same, so there is no variation in the bias voltage applied to the voltage controlled attenuator 2.

The alarm circuit 6 returns the current converter 11 to a normal state after a certain delay time. At this moment, the comparator amplifier 7 detects the difference between the detector 5 and the reference voltage source 8, and the integrator provided at the input end of the current converter 11 integrates the difference, so the voltage controlled attenuator The control voltage of 2 does not vary significantly, but monotonically increases or decreases from the fixed bias 10 voltage to the bias voltage set by the automatic power control circuit.

FIG. 3 is a specific example configuration diagram of the current converter 1. As shown in FIG.
The input signal supplied to the input terminal 21 is connected to the resistor 3
1, a comparator amplifier 32, and a capacitor 33, and then is supplied to the output terminal 22 via a resistor 34. The voltage across the resistor 34 is amplified by a differential amplifier 35 having a constant amplification degree, and is negatively fed back to the other input terminal of the comparison integrator to supply a bipolar constant current proportional to the input voltage. . The input terminal 23 is a control signal input terminal, and provides a control signal to a switch 36 formed of a relay, a transistor, or the like that connects the input terminal of the comparator amplifier 32 and ground. When the switch 36 closes, the output current of the current converter is set to zero.
When the switch 36 opens, the output current of the current converter converges to a value proportional to the input voltage with a certain time constant.

Furthermore, the present circuit is useful when the automatic power control circuit is used by providing only one circuit in the amplifier circuit of the active standby configuration. That is, in FIG. 4, a signal applied to input terminal 1 passes through voltage controlled attenuator 2 and amplifier 3, and appears at output terminal 4. Further, the standby signal applied to the input terminal 14 passes through the voltage controlled attenuator 16 and the amplifier 17 and appears at the output terminal 15. The high frequency switch 19 switches the output signals of both the active and standby devices and supplies them to the detector 5. The output voltage of the detector 5 is determined by the reference voltage source 8 as in FIG.
The comparison amplifier 7 compares the voltage with the current converter 1.
1 is converted into a current, and is negatively fed back to the fixed bias 10 or 18 of the voltage controlled attenuator 2 or 16 via the ammeter 12 and the switch 9, and via the switch 20 linked to the high frequency switch 19.

In the working backup configuration shown in FIG. 4, since the amplification degrees of the normal amplifier 3 and 17 are different, the fixed biases of the voltage controlled attenuators 2 and 16 are 10 and 18.
voltage is different. When switching automatic power control from the active device to the standby device, first
9 to cut off the high frequency signal to the detector 5,
The alarm 6 causes the switch 9 to open, and then the switch 2
0 is connected to the standby side, and the high frequency switch 19 is connected to the standby side.

Even if you perform the above operations to switch the automatic power control system from active to standby, or from standby to active,
The bias voltages of the voltage-controlled attenuators 2 and 16 of both active and backup devices only monotonically increase or decrease between the voltages of the fixed biases 10 and 18 and the voltage when automatic power control is performed, and no large changes appear. do not have. Also, when the automatic power control circuit is connected to the active equipment, the ammeter 12 indicates the change in the amplification degree of the active equipment, and when it is connected to the standby equipment, it accurately shows the change in the amplification degree of the amplifier of the standby equipment. .

As described above, the present invention can display changes in the amplification degree of the amplifier by simply adding a simple circuit to the conventional automatic power control circuit, and can completely prevent the transmission of excessive signals when the transmission signal is intermittent. Obtain an automatic power control circuit that can

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional automatic power control circuit. FIG. 2 shows an automatic power control circuit according to an embodiment of the present invention. FIG. 3 is a diagram showing a specific example of a voltage-to-current converter. FIG. 4 is another configuration diagram of the embodiment of the present invention. 1... Signal input terminal, 2... Voltage controlled attenuator,
3... Amplifier, 4... Signal output terminal, 5... Signal level detector, 6... Alarm circuit, 7... Voltage comparison amplifier, 8... Reference voltage source, 9... Switch, 10
... Fixed bias, 11 ... Voltage to current converter,
12... Ammeter, 13... High resistor, 21... Input terminal, 22... Output terminal, 23... Control signal input terminal, 31... Resistor, 32... Comparison amplifier,
33... Capacitor, 34... Resistor, 35...
Differential amplifier, 36...Switch.

Claims (1)

[Scope of utility model registration request] A detector that branches a part of the output signal of the power amplifier to obtain a DC voltage corresponding to the output signal, a voltage comparator amplifier that compares and amplifies the output of this detector with a reference voltage, and detects when the output of the detector has an abnormal value. an alarm circuit for detecting overheating; a switch for opening and closing the output of the voltage comparator amplifier controlled by the output of the alarm circuit; and a switch for superimposing the output of the switch on a fixed bias voltage and using it as a control voltage as an input for the power amplifier. a voltage-controlled attenuator for controlling a signal level; and a bipolar voltage-to-current converter between the output of the voltage comparison amplifier and the switch; An automatic power control circuit comprising: a double-oscillator ammeter through which an output current passes, and a high resistor in parallel with the switch.