JPH04284001A - Microwave detector - Google Patents

Abstract

PURPOSE:To obtain high-quality microwave outputs by preventing distortion caused by reflection from the diode of a detection circuit concerning a microwave detector for microwave power detection or the like. CONSTITUTION:At the microwave detector to detect microwaves while branching a part of the microwave transmitted on a microwave transmission line T, a 3dB 90 deg. hybrid M is provided to output the two microwaves having equal output power and phases different at 90 deg. from one microwave input, and detection circuits Da and Db having the same configuration are provided while being respectively connected to two output terminals M1 and M2 of this hybrid M. Thus, the microwaves branched from the microwave transmission line T are supplied to an input terminal Mi of the 3dB 90 deg. hybrid M.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention monitors the power of microwaves output from the output stage of a microwave transmitter and is transmitted on a microwave transmission line, or keeps this microwave power constant. The present invention relates to a microwave detection device used to obtain control signals for.

0002

[Prior Art] Fig. 3(a) conceptually shows a control system for keeping the microwave power output from the output stage of a microwave transmitter constant. A part of the microwave power of a microwave transmission line from a certain output amplifier to, for example, an antenna radiator is branched by a coupling part using coupling using electrostatic capacitance and supplied to a microwave detection device. The microwave output is kept constant by feeding back the output as a gain control signal to the output amplifier.

FIG. 2B shows a conventional example of the above-mentioned detection device composed of a microstrip line provided on a dielectric substrate, where T is a microwave transmission line for transmitting a microwave transmission signal; C is a coupler for branching a part of the microwave power transmitted on this transmission line T;
D is a diode detector, Rm is the detector D of the coupler C above.
A resistor that terminates at the opposite end of the side.

The output side of the detector D is also composed of a microstrip line, and the stub Z and land L are adjustment microstrip lines with an impedance of 50Ω. Adjustments are made by sequentially connecting conductively with copper foil or the like.

[0005] Both S1 and S2 are choke stubs, and this choke stub S1 is formed by a high impedance microstrip line having a length of a quarter wavelength of a microwave, and the choke stub S2 is a choke stub constituted by a microstrip line with an impedance of 50Ω and a length equal to a quarter wavelength of a microwave.

As mentioned above, the output of the detection circuit having such a configuration is used as a control signal for monitoring the microwave power on the microwave transmission line or for keeping the output of the microwave transmitter constant. used. In addition, R
d is the load resistance of the detector D.

[0007]

[Problem to be Solved by the Invention] In such a microwave detection circuit, the effective impedance of the diode detector D changes non-linearly depending on the amplitude of the microwave, and especially as the amplitude of the microwave increases. Then, due to the non-linear impedance change of the diode detector D, a distortion component is added to the microwave reflected from the diode D, which is superimposed on the microwave signal on the microwave transmission line T, and as a result, the transmitted microwave There was a problem that the signal quality deteriorated.

[0008] An object of the present invention is to provide a microwave detection device that can obtain high-quality microwaves by preventing deterioration of distortion in the transmitting device due to reflection from the diode of the detection circuit. do.

[0009]

[Means for solving the problem] Figure 1 showing the principle of the present invention
To quote, in a microwave detection device that branches and detects a part of the microwave transmitted on the transmission line T,
A 3dB 90 degree hybrid M that outputs two microwaves with the same output power and 90 degrees different phase from one microwave input, and a detection circuit with the same configuration connected to the two output terminals M1 and M2 of this hybrid M, respectively. Da and Db were provided, and the microwave branched from the transmission line T was configured to be supplied to the input terminal of the 3 dB 90 degree hybrid M.

0010

[Operation] The 3dB 90 degree hybrid M is constructed by combining four transmission lines Ma, Mb, Mc, and Md, each having an effective length of a quarter wavelength of the target microwave, into a square or rectangular shape as a whole. It is something that has been done,
The microwave inputted from the input terminal Mi provided at the connection point between the transmission lines Ma and Md is shifted by 1/4 wavelength, that is, by 90 degrees, and then sent to the first output terminal provided at the connection point between the transmission lines Ma and Mb. Output from M1.

On the other hand, microwaves arrive at the second output terminal M2 from the input terminal Mi through the transmission paths Ma and Mb and the transmission paths Md and Mc, but these paths are Since both have a path length of 2×1/4 wavelength, the phase is further delayed by 90 degrees from the phase of the microwave at the first output terminal M1.

Now, when the microwave input from the input terminal Mi is reflected by the first output terminal M1 and reaches this input terminal Mi again, it has a wavelength of 2/4, that is, 1
The phase is shifted by 80 degrees, and when the microwave input from the input terminal Mi is reflected by the second output terminal M2 and reaches this input terminal Mi again, it has one wavelength, that is, 3
The phase is shifted by 60 degrees.

Therefore, at this input terminal Mi, the phases of the microwave reflected by the first output terminal M1 and the microwave reflected by the second output terminal M2 are 180 degrees out of phase with each other. The waves will cancel each other out.

[0014] Then, this 3dB 90 degree hybrid M
Since the microwave power input to the input terminal Mi is equally distributed to each output terminal M1, M2 with a loss of 1/2, that is, 3 db, it is connected to the output terminals M1, M2. If the loads have the same microwave reflection characteristics, the microwaves reflected from the terminals M1 and M2 at the input terminal Mi cancel each other out with equal amplitude, and become substantially "0".

In the present invention, the output terminals M1, M
2 detection circuits Da and D each having the same configuration.
b is connected, the reflection of the microwave by these detection circuits Da and Db is always equal, and therefore becomes substantially "0" at the input terminal Mi of the 3 dB 90 degree hybrid M. Therefore, the transmission line coupled to this input terminal Mi This reflected wave no longer affects the microwave transmitted on T. It goes without saying that the two diodes used in each of the detection circuits Da and Db should have the same characteristics as possible.

[0016]

[Embodiment] FIG. 2 shows an embodiment of the present invention configured with a microstrip line provided on a dielectric substrate.
Components corresponding to those shown in FIGS. 1 and 3 are given the same reference numerals as in FIGS. 1 and 3.

A coupler C placed close to the transmission line T
branches the microwave transmitted on the transmission line T via the capacitance, and supplies the branched microwave from one terminal to the input terminal of the 3 dB 90 degree hybrid M. Note that the other terminal of this coupling portion C is connected to a terminating resistor Rm
connected to.

Regarding this hybrid M, first refer to FIG.
Since the operation of the present invention has been explained in detail with reference to , the explanation of the operation will be omitted. Incidentally, the vacant terminal of this hybrid M is grounded via a terminating resistor Rz to prevent unnecessary reflections.

As explained with reference to FIG. 1, detection circuits Da and Db having the same configuration are connected to the two output terminals of this hybrid M, respectively. Note that the two diodes used in each of these detection circuits Da and Db are also selected to have the same characteristics as possible.

As mentioned above, the two detection circuits Da and Db
Since the configurations of are the same, the configuration of one of the detection circuits Da will be explained. The stub Z and the land L, which are configured by a microstrip line on the detection output side of the detection diode D, constitute an adjustment microstrip line with an impedance of 50Ω. The impedance is adjusted by sequentially conductively connecting this stub Z and an appropriate number of lands L using copper foil or the like.

S1 is a choke stub formed by a high impedance microstrip line having a length of a quarter wavelength of a microwave, and S2 is an impedance 50Ω having a length of a quarter wavelength of a microwave.
This is a choke stub constituted by a microstrip line, and prevents microwave components from being output from this detection circuit Da as a detection output.

The outputs from the detection circuits Da and Db as described above are combined by a common connection, and a signal indicating the power of the microwave on the microwave transmission line T is obtained as a voltage between the terminals of the load resistor Rd. can be used as a control signal to keep the output of a microwave transmitter constant, or as a signal to monitor microwave power on a microwave transmission line.

[0023]

According to the present invention, the reflected waves generated by the two microwave detection circuits cancel each other out and are not output to the input terminal of the 3 dB 90 degree hybrid.
Therefore, the reflected waves do not affect the microwaves transmitted by the microwave transmission line coupled to this input terminal, so that the quality of the transmitted microwaves can be maintained at a good quality.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a microwave detection device according to the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a conventional example.

[Explanation of symbols]

T Microwave transmission line M 3dB90 degree hybrid Mi 3dB9
0 degree hybrid input terminals Ma to Md 3 dB 90 degree hybrid transmission lines M1, M2 3 dB90
Degree hybrid output terminals Da, Db Detection circuit C Coupler D
Detection diode Rm, Rd,
Rz terminating resistor

Claims (1)

[Claims] Claim 1: In a microwave detection device that branches and detects a part of microwaves transmitted on a microwave transmission line, one microwave input detects two waves having the same output power and 90 degrees different phase. It is equipped with a 3 dB 90 degree hybrid that outputs microwaves, and a detection circuit of the same configuration connected to each of the two output terminals of this hybrid, and the microwave branched from the microwave transmission line is sent to the input terminal of the 3 dB 90 degree hybrid. A microwave detection device characterized in that it is configured to supply