JPS6066166A - Reflected wave power detecting circuit - Google Patents

Abstract

PURPOSE:To detect exactly a reflected wave power even if a position of a mismatching part is varied, by deriving a ratio of a traveling wave power from a directional coupler and a reflected wave power. CONSTITUTION:A reflected wave power from a terminal 28 of a directional coupler 20 is inputted to a differential amplifier 26 after a DC portion has been detected by a detecting circuit 22. Also, a traveling wave power from a terminal 29 is distributed by a distributor 21, and one is adjusted 23 to a regulated level, and thereafter, inputted to the amplifier 26 after a DC portion has been detected by a detecting circuit 24. An output of this amplifier 26 becomes that which corresponds to a ratio of the traveling wave power and the reflected wave power, and it is sent to a control part 27. The control part 27 is controlled only when it is detected 25 that the other traveling wave power distributed by the distributor 21 is the regulated level. In this way, even if a position of a mismatching part is varied, the reflected wave power can be detected exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reflected wave power detection circuit for protecting an amplifying element of a power amplifier from load fluctuations.

In recent years, the output of fully fixed power amplifiers has been increasing, and units exceeding IKW have been put into practical use in the VHF band. In addition, high-efficiency power amplifiers that are more compact and power-saving are being used that do not use circulators to increase the efficiency of the amplifier element and reduce output circuit loss as much as possible. It has become to. However, in power amplifiers that do not use this circulator, the amplifier element may be destroyed by the reflected wave power caused by load fluctuations, and to prevent this, the reflected wave power is detected. Lower the input signal level of the power amplifier.

An example of a reflected wave/power detection circuit that has been used as the above-mentioned preservation means is as shown in FIG. 1, for example.

' Municipal power amplifiers ii and t, a directional coupler 3 is provided between the amplifier section 2 and the output terminal 13, and a detection circuit 20 and a control section 3 are provided.
o. Then, the reflected wave '17L force is taken out from the force detection terminal 13 as the reflected wave 1 of the directional coupler 3, and is controlled by the voltage detected by the wave detector.

However, this prescriptive pressure varies depending on the location of the impedance mismatch that occurs between the output terminal 13 of the power multiplier 1 and the antenna. As shown in Figure 2, the power changes between Pl and P2 depending on the distance from the output terminal 13 to the mismatched part.As a result, the detection of reflected power becomes inaccurate.
This has the drawback of causing malfunction of the control section 3o.

The present invention aims to overcome these conventional drawbacks and provide a reflected wave power detection circuit that detects the ratio of the traveling wave to the reflected wave that is always constant even if the position of the mismatched portion changes. be. Specifically, it includes a directional coupler that is coupled to the output line of the power multiplier and has a traveling wave power detection terminal and a reflected wave power detection terminal, and a high frequency signal from the reflected wave power detection terminal of the directional coupler. a first detection circuit that detects a direct current component corresponding to the reflected wave power; and a distributor that receives a high frequency signal from the traveling wave detection terminal of the directional coupler and divides the high frequency signal into two prescribed distributions. , a level adjuster that receives the output of one of the dividers and adjusts the high-frequency signal to a specified level; and a second detection circuit that receives the output of the level adjuster and detects a DC component corresponding to the output power. and a differential amplifier receiving the outputs of the first and second detection circuits, and a third detection circuit receiving the output of the other of the distributors and detecting a prescribed level; It is an object of the present invention to provide a reflected wave power detection circuit comprising a control section that is controlled by the output signal of the differential amplifier only when a signal is detected.

The present invention will be explained below based on an embodiment shown in FIG. Note that, in the following, parts common to those in the prior art will be given the same reference numerals, and explanations of multiplying and dropping will be omitted.

In the figure, 20 is a directional coupler, 21 is a distributor, 22 is a first detection circuit that detects the DC component corresponding to the reflected wave power, 23 is a level adjuster that adjusts the traveling wave power by 17 levels, and 24 is the level a second detection circuit that detects a DC component corresponding to the output power of the regulator 23; 25, a third detection circuit that detects whether the traveling wave power is at a specified level; 26, a differential amplifier;
7 is a control section. Reference numeral 28 indicates a reflected power detection terminal of the directional coupler, and 29 indicates a traveling wave power detection terminal of the directional coupler 2o.

Here, the high frequency signal from the reflected wave power detection terminal 28 of the directional coupler 2o is sent to one of the long sword terminals of the differential amplifier 26 via the first detection circuit 22 which outputs a DC component corresponding to the reflected wave power. join. In addition, the high frequency signal from the traveling wave power detection terminal 29 of the directional coupler 20 is distributed by the distributor 21 into υ prescribed distributions, and one of the signals is distributed to the power amplifier 1 by the power amplifier l.
The level adjuster 23 adjusts the voltage so that the VSWR (voltage standing wave ratio, hereinafter abbreviated) corresponds to the reflected wave power that does not destroy the element.

This adjusted high frequency signal is applied to the other long terminal of the differential amplifier 26 via the second detection circuit 24 which detects the output corresponding to the power indicated by the signal. Then, the output of the differential amplifier 26 corresponds to the ratio of the traveling wave power to the reflected wave power, that is, the VSWR of the load, and this output signal is sent to the control section 27.

By the way, when power amplifiers 1 are used in parallel, it is often the case that due to variations in the start-up of the power amplifiers 1, before one power amplifier starts up, another power amplifier outputs an output. , the signal goes around through the combiner, so that the signal from the output terminal enters with its own traveling wave being 0, and the differential amplifier 26 outputs the signal with infinite VSWR. Therefore, the power of the other traveling wave from the distributor 21 is at a specified level (a level that does not destroy the amplifying element of the amplifying section 2 even if the traveling wave power is totally reflected). , to the control unit 27, and only when there is a specified traveling wave power, the control unit 27 is controlled by the signal from the differential amplifier 26.

Since the reflected wave power detection circuit according to the present invention is as described above, there is no error such as changes in the reflected wave power depending on the location of the mismatched part, and accurate detection is possible, which greatly contributes to high reliability. Effects can be obtained.

[Brief explanation of the drawing]

Figure 1 shows gravity increase using a conventional reflected wave power detection circuit.
] block diagram of the device, Figure 2 is a characteristic diagram showing the change in the output power of the reflected wave power detection terminal of the directional coupler by changing the distance of the reflection point,
Figure 3 is a block diagram of a gravity amplifier including an embodiment of the present invention. 1...' Gravity amplifier 2... Amplifying section 12... Output line 20... Directional coupler 21... Distributor 2
2...Sense-detection circuit 23..."Level adjuster 24
...Second detection circuit 25...Third detection circuit 26...
・Differential multiplier 1j 27...control unit 28...reflected wave power detection terminal 29...travelling wave power detection terminal Applicant: NEC Corporation

Claims (1)

[Claims] A directional coupler having a traveling wave power detection terminal and a reflected wave power output terminal and coupled to an output line of a power increaser [1], and reflected wave power detection of the directional coupler. a first detection circuit that receives a high frequency signal from the terminal and detects a DC component corresponding to the reflected wave power; and a first detection circuit that receives a high frequency signal from the traveling wave detection terminal of the directional coupler and distributes the high frequency signal in a prescribed manner. a divider that divides into two; a level adjuster that receives the output of one of the dividers and adjusts the high frequency signal to a specified level; and a level adjuster that receives the output of the level adjuster and adjusts the DC component corresponding to the output power. a second detection circuit for detecting; and said first detection circuit. A differential amplifier receives the output of the second detection circuit, and an output signal 4i4iK of the differential amplifier receives the output of the other of the distributors and is controlled by the output signal 4i4iK only when a signal that detects a specified level is detected. A reflected wave power detection circuit comprising a control section.