JPH11284522A - Amplifier control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an amplifier control circuit which controls an amplifier without breaking it in all power ranges independent of the absolute value of amplifier output power and which does not require changes in the design of a control circuit, even at the time of changing power specification. SOLUTION: In a power amplifier consisting of a power amplifying part 3 that performs power amplification of a high frequency signal, a connecting part 10 which extracts a part of power sent from the part 3 to an antenna 6 and an amplification control part which utilizes the extracted power for control over the part 3, the part 10 is provided with a coupler which respectively connects a traveling wave to a reflected wave, uses a voltage standing wave ratio calculated from traveling wave power and reflected wave power obtained from the coupler and controls attenuation or operation interrupt of a transmission output of the transmission power amplifier 3 or a transmission buffer amplifier 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission circuit of a communication device or the like, and more particularly to an amplifier control circuit of a transmission circuit.

[0002]

2. Description of the Related Art FIG. 2 shows a configuration example of an amplifier control circuit in a conventional radio transmitter circuit. In FIG. 2, 1 is a voltage controlled oscillator, 2 is a transmission buffer amplifier, 3 is a transmission power amplifier, 4 is a transmission / reception switch, 5 is a low-pass bandpass filter, 6 is an antenna, 7 is a coupler, and 8 is detection. And 9 is a comparator. In the figure, a high-frequency transmission signal output from a voltage-controlled oscillator 1 is amplified by a transmission buffer amplifier 2 and further amplified by a transmission power amplifier 3 to a specified output power. Thereafter, the signal passes through a transmission / reception switch 4 for switching between transmission and reception, passes through a low-pass bandpass filter 5, and is output from an antenna 6. On the other hand, part of the power output from the transmission power amplifier 3 is taken out by the coupler 7 and converted into a DC voltage by the detector 8. This voltage is compared with a reference voltage in a comparator 9 to control the driving voltage of the transmission buffer amplifier 2 and change the output power of the transmission buffer amplifier 2. As a result, a loop is formed such that the detection voltage and the reference voltage become equal, and the transmission power output from the antenna 6 is controlled to be constant. The same applies to the case where the coupler is a directional coupler and only a traveling wave is used.

[0003]

In a conventional transmission circuit, when a capacitor is employed as a coupler, the antenna is in a mismatched state due to some influence from the outside, and the antenna from the end of the last stage amplifying element in the amplifier circuit to the antenna. When the standing wave is generated during the period, if the position of the coupler is mounted at the distance d as shown in FIG. 3, the amplitude of the power is very small and the automatic power control circuit It determines that the transmission power is insufficient for the set value and operates to increase the power. As a result, the amplitude of the standing wave increases more and more, the voltage amplitude applied to the amplifying element eventually exceeds the rating, and the element is destroyed. Also, when a directional coupler is used as the coupler, the reflected power is not detected, so that the antenna is also affected by the outside and falls into a mismatched state, and the end of the amplifier circuit from the end of the last stage amplifying element. Even when a standing wave occurs up to the antenna, the detection voltage of the traveling wave does not always fluctuate, so the automatic power control circuit operates to maintain a constant transmission power. Therefore, even when the mismatch state is remarkable and the output power of the transmission power amplifier is totally reflected by the antenna, the output power of the transmission power amplifier does not decrease.

As described above, in order to prevent the influence of the reflected wave, there is generally a method of mounting an isolator on a transmission line. However, as the frequency becomes lower, the size of the isolator becomes larger, so that it is mounted on a small radio or the like. Have physical difficulties. Therefore, it is disadvantageous in terms of miniaturization of the wireless device. In addition, the coupling unit detects the reflected wave power, converts the detected power to a current or voltage by a detector, compares the voltage value with an arbitrary set voltage, and attenuates the transmission power of the transmission power amplifier or the transmission buffer amplifier. Or there is a control method to shut down the operation,
This requires a comparator for reflected wave power. As a result, the number of components increases, which is also disadvantageous in terms of miniaturization of the wireless device. Furthermore, when specifications change, every time the transmission power amplifier is changed and the output power changes significantly, an arbitrary set voltage must be reset, and a common circuit for cost reduction was considered. In such a case, it is disadvantageous because the change work efficiency in changing the specifications is poor.

[0005]

In order to solve this problem, the present invention detects an input power and a reflected power obtained from a directional coupler, calculates a voltage standing wave ratio therefrom, and generates an automatic power control circuit. It is an object of the present invention to realize an amplifier control circuit that controls a drive voltage and a drive current of a transmission power amplifier and a transmission buffer amplifier in the above and attenuates transmission power. As a result, control of the transmission power amplifier can be realized in any use situation.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram showing a configuration example of an amplifier control circuit of a radio transmitter according to the present invention. This embodiment is a wireless device that is very small and does not use an isolator due to mounting restrictions, and an example in which an amplifier protection circuit is mounted on a transmission circuit in a wireless device that uses a transmission buffer amplifier for an automatic power control circuit. Is shown. In FIG. 1, 1
Is a voltage controlled oscillator, 2 is a transmission buffer amplifier, 3 is a transmission power amplifier, 4 is a transmission / reception switch, 5 is a low-pass bandpass filter, 6 is an antenna, 8 is a detector, 10 is a directional coupler, 11 Is a reflected wave detector, and 12 is a voltage controller.

In the figure, when the transmission circuit is operating, if the load on the antenna 6 fluctuates due to some influence, the matching from the transmission power amplifier 3 to the antenna 6 changes and falls into a mismatch. A standing wave may be generated between the final stage amplifying element and the antenna 6 or the transmission power amplifier 3
Current consumption increases sharply. At this time, when the automatic power control circuit operates, the output power of the transmission buffer amplifier 2 works to increase or decrease. When the transmission buffer amplifier 2 operates to increase the output power of the transmission power amplifier 3, the input direction power obtained from the directional coupler 10 is detected by the power detector 11, and the reflected power is detected by the reflected power detector. 12, the obtained result is calculated by the voltage controller 13 to calculate the voltage standing wave ratio, the calculated result is compared with the voltage standing wave set value, and the driving voltage of the transmission buffer amplifier 2 is used by using the result. Is controlled to be disconnected. Therefore, under any conditions, the destruction of the amplification element of the transmission power amplifier 3 due to the reflected power can be prevented, and the transmission power amplifier 3 can be protected.

In the above-described embodiment, the mismatching state between the antenna 6 and the transmission power amplifier 3 is determined by using the voltage standing wave ratio data calculated from the traveling wave power and the reflected wave power obtained from the directional coupler 10. And an alarm device such as an alarm can inform the operator of the inconsistency, which is more practical.

[0009]

As described above, according to the present invention, it is possible to control the amplifier not to be destroyed in any power range irrespective of the absolute value of the amplifier output power, and to control even when the power specification is changed. An excellent effect that there is no need to change the circuit design can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a configuration example of an amplifier control circuit in a conventional radio transmission circuit.

FIG. 3 is a diagram showing a problem of the conventional example.

[Explanation of symbols]

1: voltage-controlled oscillator, 2: transmission buffer amplifier, 3: transmission power amplifier, 4: transmission / reception switch, 5: low-pass bandpass filter,
6: antenna, 7: coupler,
8: detector, 9: comparator, 1
0: directional coupler, 11: power detector,
12: reflected power detector, 13: voltage controller.

Claims (3)

[Claims] 1. A power amplification unit for power-amplifying a high-frequency signal, a coupling unit for extracting a part of the power transmitted from the power amplification unit to the antenna, and an amplification control unit for using the extracted power for controlling the power amplification unit. In the power amplifier, comprising a coupler for coupling each of the traveling wave and the reflected wave to the coupling unit, using a voltage standing wave ratio calculated from the traveling wave power and the reflected wave power obtained from the coupler, transmitting An amplifier control circuit for controlling a transmission output of a power amplifier or a transmission buffer amplifier to be attenuated or cut off. 2. The amplifier control circuit according to claim 1, wherein a mismatch state between the antenna and the transmission power amplifier is displayed by using a voltage standing wave ratio calculated from the traveling wave power and the reflected wave power obtained from the coupler. An amplifier control circuit comprising display means for performing the following. 3. The amplifier control circuit according to claim 1, wherein a mismatch between the antenna and the transmission power amplifier is alarmed by using a voltage standing wave ratio calculated from the traveling wave power and the reflected wave power obtained from the coupler. An amplifier control circuit comprising alarm means for informing by means of: