JPH0815344A - Vswr detection circuit - Google Patents

Abstract

PURPOSE:To detect the standing wave ratio VSWR accurately by disposing two detection connectors on one surface of a waveguide while spacing apart by a distance corresponding to a quarter of wavelength in the waveguide. CONSTITUTION:Two detection connectors 3, 4 are disposed on one surface of a waveguide 2 while being spaced apart by a distance corresponding to a quarter of wavelength lambda in the waveguide. Outputs from the connectors 3, 4 are detected through detectors 6a, 6b and converted into DC levels 7, 8. The DC levels 7, 8 are compared through a comparator 9 and the amplitude of VSWR is detected based on the level difference. Since A-B=lambda/4, the difference of outputs detected at points A and B corresponds to the amplitude of VSWR at all times. Furthermore, since the connectors 3, 4 are located at positions just corresponding to the positive and negative peaks of VSWR, the difference of detected output represents the amplitude of VSWR itself.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VSWR (standing wave ratio) detection circuit, and more particularly to a VSWR detection circuit used in a microwave band high power amplifier.

[0002]

2. Description of the Related Art In a conventional VSWR detection circuit of this type,
As shown in FIG. 3, an output power detecting directional coupler 11 and a reflected power detecting directional coupler 12 are provided between the output terminal of the microwave high power amplifier 1 and the load circuit 5. The waveguide coaxial converters 13 and 14 are connected to the respective directional couplers 11 and 12, respectively.

The output voltage of the output power detecting directional coupler 11 is converted into a DC voltage 8 by a detector 6a and supplied to an output voltage measuring circuit (not shown). Also, the output voltage of the directional coupler 12 for detecting the reflected power is the DC voltage 7 by the detector 6b.
Is converted to the VSWR detection circuit 15 and sent to the VSWR detection circuit 15 and compared with a preset reference level. This DC voltage 7
Is above the reference level, it is considered that the VSWR characteristic has deteriorated, and an alarm 10 is issued to the amplifying apparatus 1 to cut off the amplified output.

The set value of the reference level in this case is determined by the ratio of the output power and the reflected power.

On the other hand, Japanese Utility Model Laid-Open No. 2-36217 discloses that
A technique for controlling the amplification factor of a microwave high power amplifier so that the amplified output is constant is disclosed. With this technology, it is necessary to detect the amplified output accurately regardless of VSWR and feed it back to the amplification device to control the amplification factor.
Performed at two detection points provided with a quarter wavelength interval,
Accurate output detection independent of VSWR is performed by adding and synthesizing the detection outputs at these two detection points.

[0006]

[Problems to be Solved] In the configuration shown in FIG.
Since the waveguide directional coupler is used for detecting the SWR, there is a drawback that the waveguide circuit is structurally complicated and large-scale. Further, when the output power becomes large, it is necessary to extremely reduce the coupling amount of the waveguide directional coupler, so that there is a drawback that a high machining accuracy is required, which causes a cost increase.

In the technique disclosed in Japanese Utility Model Laid-Open No. 2-36217, VSWR is not detected, but conversely, the influence of the fluctuation of VSWR is completely eliminated to accurately detect the amplified output voltage. Therefore, VSWR cannot be detected.

An object of the present invention is to provide a VSWR detection circuit capable of accurately detecting VSWR with an extremely simple structure.

Another object of the present invention is to provide a VSWR detection circuit which can easily detect VSWR even when the output power becomes large and vice versa.

[0010]

According to the present invention, there is provided a VSWR detection circuit of an amplifying device, wherein an amplified output of the amplifying means is led out by a waveguide and supplied to a load. VSW having two detection connectors provided on one tube surface with a distance corresponding to 1/4 of the in-tube wavelength
An R detection circuit is obtained.

[0011]

[Function] 1/4 of the guide wavelength of the waveguide for deriving the amplified output
Since the detection output difference at a place separated from each other by a distance corresponding to is always shown as a value proportional to the amplitude value of VSWR, this fact is utilized to guide the wavelength inside the waveguide on one surface of the waveguide. Two detection connectors are provided at positions separated from each other by a distance corresponding to 1/4 of the above.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A is a circuit diagram of an embodiment of the present invention, and the same portions as those in FIG. 4 are designated by the same reference numerals. In the figure, the output of the microwave band high power amplifier 1 and the load 5
A waveguide 2 is connected between and, and the waveguide 5 supplies amplified power to the load 5.

On one surface of this waveguide 2 (a wide surface is good)
Is provided with two detection connectors 3 and 4 which are provided apart from each other by a distance corresponding to ¼ of the guide wavelength λ. The detection outputs of the detection connectors 3 and 4 are detected by the wave detectors 6a and 6b, respectively, and the DC levels 7 and 8 are detected.
Is converted to. These conversion DC levels 7 and 8 are the comparator 9
Then, the levels are compared and the level difference between the two DC levels 7 and 8 is detected.

Here, referring to FIG. 1B, there is shown the relationship between the distance of the waveguide 2 from the load 5 and the voltage of VSWR. The wavelength of VSWR is the wavelength of the amplified output of the amplifier 1. It is 1/2 of (wavelength λ in the waveguide 2).
If the distances of the detection connectors 3 and 4 from the load 5 are A and B, then A−B = λ / 4. Therefore, the difference between the detection outputs at these points A and B is always the amplitude of VSWR. It can be seen that the value corresponds to the value.

In the example of FIG. 1B, the connectors 3 and 4 are
Since the positions of 1 and 2 respectively correspond to the positive peak and the negative peak of VSWR, the difference between the detected outputs of these two shows exactly the amplitude of VSWR itself. Therefore, ideally, the connectors 3 and 4 should be provided at the positions A and B shown in FIG. 1B, and these positions can be easily determined by measuring the VSWR.

Therefore, the comparison result of the comparator 9 is VSW.
When the amplitude of R becomes equal to or higher than a predetermined level, the warning 10 is supplied to the amplifying device 1 to control the cutoff of the amplified output or the like.

FIG. 2 is a view showing an example of the detection connectors 3 and 4, and the center conductor 30 of the connectors 3 and 4 is used as an antenna to extract the signal inside the waveguide 2.
Since the extracted power differs depending on the shape and length of the center conductor 30, if these shapes and lengths are appropriately selected and used, even if the amplified output power becomes large or small, the desired power can be obtained. Can be extracted. Incidentally, the shape of the central conductor is generally a cylindrical shape, and the extraction power is changed by changing the inner diameter or the outer diameter of the cylindrical shape.

[0019]

As described above, according to the present invention, there is an effect that the structure is simple and the cost is low because the connector can be attached to the waveguide in an extremely simple structure. Further, since the amount of power detected by the detector can be changed only by changing the length and shape of the central conductor of the connector, it is possible to easily deal with the magnitude of the power of the amplified output.

[Brief description of drawings]

1A is a circuit diagram of an embodiment of the present invention, and FIG. 1B is a diagram for explaining the principle of the present invention.

FIG. 2 is a diagram showing the configuration of the detection connector of FIG.

FIG. 3 is a diagram showing a circuit example of a conventional VSWR detection circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microwave power amplifier 2 Waveguide 3,4 Detection connector 5 Load 6a, 6b Detector 9 Comparator

Claims (3)

[Claims] 1. A VSWR detection circuit of an amplification device in which an amplified output of an amplification means is derived by a waveguide and is supplied to a load, wherein a 1 / wavelength of a guide wavelength is provided on one surface of the waveguide.
A VSWR detection circuit having two detection connectors provided at a distance corresponding to 4. 2. The VSWR detection circuit according to claim 1, wherein VSWR is detected according to a difference between outputs of the detection connectors. 3. A detection means for detecting the output of each of the detection connectors, and a comparison means for detecting the difference between these detection outputs, wherein the VSWR is detected based on the comparison result. Item 2. The VSWR detection circuit according to item 2.