JPH06260946A - Reflected power sensor circuit - Google Patents

Abstract

PURPOSE:To provide a power sensor circuit which can perform the correct control of operation of a transmitter by sensing only the carrier component of the reflected power. CONSTITUTION:A directional coupler 4 takes a reflected power component out of a BPF 2 set between a transmitter 1 and an antenna 3. Then the reflected power is transmitted through a sensor circuit BPF 5 which is especially prepared and has the band pass characteristic equivalent to that of the BPF 2. A detector 6 detects a signal component out of the reflected power, and the transmitter 1 is controlled based on the detected signal component. The spurious component generated by the transmitter 1 in a switching state of an exciter, etc., is reflected by the BPF 2 and taken out by the coupler 4. However the spurious component does not reach the detector 6 due to the presence of the BPF 5. Thus only the desired carrier component is sensed by a reflected power sensor circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission system having a bandpass filter on the output side of a transmitter, and more particularly to a reflected power detection circuit for detecting a reflected wave from the bandpass filter.

[0002]

2. Description of the Related Art FIG. 2 is a diagram showing a configuration of a conventional reflected power detection circuit, which includes a transmitter 1, a bandpass filter 2, and
Antenna 3 and directional coupler 4 for extracting reflected power component
, A detector 6 for extracting a signal component from the extracted reflected power, and a comparator 7 for comparing the amount of reflected power with a predetermined value.
The control unit 8 controls the operation of the transmitter based on the output of the comparator, and protects the transmitter from the reflected power.

[0003]

In the conventional reflected power detection circuit described above, when the transmitter 1 has the bandpass filter 2 having a narrow bandpass characteristic for preventing cross-modulation on the output side, The spurious component generated from the transmitter when the exciter of the machine is switched or the program input system is switched is input to the bandpass filter 2 having a narrow band characteristic.
However, this spurious component is blocked by the narrow band characteristic of the bandpass filter, returns to the transmitter as reflected power, and is detected as a reflection abnormality. In this way, the reflected power abnormality is detected even when the carrier component, which is the original purpose, is reflected. For this reason, conventionally, the processing has been performed by allowing the reflection abnormality to a certain extent or less by experience, but there is a drawback that the sensitivity to the reflection of the carrier component, which is the original purpose, is reduced by the allowance.

In view of the above drawbacks, the present invention seeks to provide a reflected power detection circuit that is not affected by spurious components from the transmitter.

[0005]

According to the present invention, a reflected power component from a bandpass filter provided between a transmitter and an antenna is extracted by a directional coupler, and a signal is detected by a detector from the extracted reflected power. In a transmission system of a method of detecting a component and controlling the transmitter based on the detected signal component, for a detection circuit having a pass band characteristic equivalent to that of the band pass filter between the directional coupler and the detector. A reflected power detection circuit having a bandpass filter is obtained.

[0006]

1 is a diagram showing the configuration of an embodiment of the present invention. The power output from the transmitter 1 passes through the bandpass filter 2 having a narrow band characteristic and is transmitted to the antenna 3. However, the spurious component generated from the transmitter at the time of switching the exciter in the transmitter 1 or switching the program input system cannot pass through the bandpass filter 2, is reflected, and is extracted as a reflected power component by the directional coupler 4. To be done. However, this reflected power component is
The spurious component is removed by the bandpass filter 5 for the detection circuit, which has the same passband characteristic as the above, and the reflected power of only the target carrier component passes. A signal component is extracted from the detector 6 from the passed power component and sent to the comparator 7. The comparator compares the signal of this reflection component with a preset specified signal S, and the control unit 8 controls the transmitter 1 based on the comparison result.

Although the pass band characteristic of the detector band pass filter 5 and the pass band characteristic of the band pass filter 2 are equal to each other in the above description, it is most preferable that they are completely the same, but it is practically small. The term "equivalent" is used with such a meaning in the present specification because it can be used even if there is a deviation.

[0008]

As described above, the present invention is a bandpass filter having a cutoff characteristic equivalent to that of a bandpass filter used on the output side of a broadcaster between a directional coupler for detecting abnormal reflection and a detector. By inserting, it is possible to detect only the reflected power of the carrier component, which is the original purpose, and it is possible to accurately detect the reflected power.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of a conventional device.

[Explanation of symbols]

 1 Transmitter 2 Bandpass Filter 3 Antenna 4 Directional Coupler 5 Detection Circuit Bandpass Filter 6 Detector 7 Comparator 8 Control Section S Specified Signal

Claims (1)

[Claims] 1. A reflected power component from a bandpass filter provided between a transmitter and an antenna is extracted by a directional coupler, a signal component is detected by a detector from the extracted reflected power, and the detected signal component is detected. In the transmission system of the method for controlling the transmitter based on the above, a detection circuit bandpass filter having a passband characteristic equivalent to that of the bandpass filter is provided between the directional coupler and the detector. Reflected power detection circuit.