JPH0688844A - Measuring method for s' parameter of multiport circuit - Google Patents

Abstract

PURPOSE:To calculate the true S parameter of a multiport circuit by calculating S parameters which cause errors between the ports and measuring ends of a vector network analyzer and reflection coefficients which cause errors in nonreflective terminators. CONSTITUTION:Before measuring the S parameter of a four-port circuit 5, a computer 15 calculates S parameters which cause errors between the ports 11 and 12 and measuring ends 6 and 7 of a vector network analyzer 18 by the TRL method. In addition, reflection coefficients are measured by successively inserting transmission lines having short electrical lengths between nonreflective terminators 13 and 14 which are coaxial with the end 6 and reflection coefficients which cause errors in the terminators 13 and 14 are calculated from the measured results. Then the S parameter is measured by connecting the ports 1 and 2 of a four-port circuit 5 which is an object to be measured to the ends 6 and 7 and terminators 13 and 14 to the ports 3 and 4 of the circuit 5. From the measured S parameter, the S parameters which cause errors and reflection coefficients are removed by using the computer 15. Therefore, the real S parameter of the circuit 5 can be calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for measuring the true S-parameters of a multiport circuit using a vector network analyzer having two measuring ports connected to the first and second measuring ends, respectively. Regarding improvement.

[0002]

2. Description of the Related Art In recent years, with the widespread use of microwave and millimeter wave devices, S-parameter measurement technology has become important. In particular, as disclosed in Japanese Patent Application No. 3-91754, research on multiport circuits has become active, such as using a 4-port circuit as a matching circuit for a low noise amplifier.
Accurate measurement of S-parameters in multiport circuits has become especially important. As a widely used measuring method of S-parameters at present, as shown in FIG. Connect to the measuring ends 6 and 7 of the vector network analyzer,
A method of measuring the remaining two ports 3 and 4 by non-reflecting terminations (16, 17) by some means is used. The measuring ends 6 and 7 of the network analyzer are calibrated by the TRL method, and it is intended that the S parameter of the DUT inserted between the measuring ends can be accurately measured. TRL
The method is, for example, IEEE Trans. Microwave Theory Tech.,
The calibration method disclosed in Vol. MTT-27, No. 12, Dec. 1979. p. 987-993 is a method suitable for measurement of a microstrip line circuit.

[0003]

The conventional measuring method shown in the example of FIG. 5 uses the remaining (N-2) ports other than the two ports used for the measurement among the four ports of the DUT. Is measured with a non-reflective termination by some means, but it is generally very difficult to accurately perform a non-reflective termination. Therefore, there is a problem in that the S parameter measured by the conventional method includes an error and does not become the true S parameter of the measured object.

An object of the present invention is to provide a measuring method for removing an error factor from an S parameter of a multiport circuit measured by a vector network analyzer to obtain a true S parameter.

[0005]

In order to achieve the above object, the measuring method of the present invention comprises a 1-port load having a large reflection coefficient and two transmission lines having different electric lengths as calibration standards. The first measurement end is connected to the load to measure the reflection coefficient, the second measurement end is connected to the load to measure the reflection coefficient, and the electrical length is provided between the first measurement end and the second measurement end. Insert a short transmission line of 4 and measure 4 S-parameters.
Between the first measuring end and the (N-2) non-reflective terminator by inserting a transmission line having a long electrical length between the measuring end of the second measuring end and the second measuring end to measure four S-parameters. A transmission line with a short electrical length is sequentially inserted into to measure the reflection coefficient, and from these measurement results, the error factor S parameter from the first measurement port to the first measurement end of the vector network analyzer,
The error factor S parameter from the second port to the second measurement end and the error factor reflection coefficient of the (N−2) non-reflection terminators are calculated, and N ports are actually measured at the time of measurement of the N port circuit. The (N-2) non-reflective terminators are connected to (N-2) ports that are not used for measurement, and the above-mentioned error factors are removed from the measured S-parameters to determine the true S-value of the N-port circuit. The point is to get the parameters.

[0006]

In the measuring method of the present invention, the S parameter of the error factor from the first port to the first measuring end of the vector network analyzer and the S parameter of the error factor from the second port to the second measuring end, It is possible to calculate the reflection coefficient of the slight difference factor of (N-2) non-reflection terminators, and when actually measuring the N-port circuit, do not use (N-2) of the N ports Above (N-2) on the port
The non-reflective terminators can be connected to obtain the true S-parameters of the N-port circuit by removing the above error factors from the measured S-parameters.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show an embodiment of the measuring method of the present invention, in which 5 is a 4-port circuit having 4 ports 1 to 4, 6 and 7 are vector network analyzers 1.
The first and second measuring terminals 8 and 9 respectively connected to the first port 11 and the second port 12 of the reference numeral 8, 9 and 10 respectively represent a load serving as a TRL calibration standard, a transmission line with a short electrical length, and an electrical length. It is a long transmission line. Reference numerals 13 and 14 are coaxial type non-reflective terminators, 15 is a computer, and 16 and 17 are non-reflective terminators.

First, before measuring the S parameter of the 4-port circuit 5, the TRL (Through REFLEC
T-LINE) In order to calibrate, the reflection coefficient is measured by connecting the first measuring end 6 and the load 8 and the reflection coefficient is measured by connecting the second measuring end 7 and the load. A transmission line 9 having a short electrical length is inserted between the end 6 and the second measuring end 7 to measure four S-parameters, and the electrical length is placed between the first measuring end 6 and the second measuring end 7. Of the long transmission line 10 is inserted and four S-parameters are measured. From these measurement results, the computer 15 causes the computer 15 to calculate the error factor S parameter from the first port 11 to the first measuring end 6 and the error factor S parameter from the second port 12 to the second measuring end 7. The parameters are calculated by the TRL method.

Further, since the non-reflective end portion is calibrated by the procedure shown in FIG. 3, the electrical length between the first measuring end 6 and the two non-reflective terminators 13 and 14 used for the measurement is sequentially short. The transmission line 9 is inserted and the reflection coefficient is measured. From these results, the computer 15 uses the two anti-reflection terminators 1
The reflection coefficients of error factors 3 and 14 are calculated.

Next, as shown in FIG. 3, the S of the 4-port circuit 5 is
In order to measure the parameters, two ports 1 and 2 used for the measurement are connected to the measurement ends 6 and 7 of the vector network analyzer 18, and the remaining two ports 3 and 4 are provided with coaxial reflectionless terminators 13. 14 is connected and the S-parameter is measured. From the measured S parameter, the S parameter and the reflection coefficient of the error factor are removed by using an external calculation means such as the computer 15. In this way, the true S parameter of the 4-port circuit 5 that is the DUT is calculated.

FIG. 4 is a flowchart showing each procedure of the above-described measuring method of the present invention.

[0012]

As described above, according to the measuring method of the present invention, the S parameter of the error factor from the first port to the first measuring end of the vector network analyzer and the second measurement from the second port. The S parameter of the error factor up to the end and the reflection coefficient of the error factor of the (N-2) non-reflection terminators are calculated, and at the time of actual measurement of the N port circuit,
Of the N ports, the (N-2) non-reflective terminators are connected to the (N-2) ports that are not used for measurement, and the error factor is removed from the measured S-parameters to obtain N.
The true S-parameters of the port circuit can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a procedure of TRL calibration.

FIG. 2 is an explanatory diagram showing a procedure for calibrating a non-reflection end portion by the method of the present invention.

FIG. 3 is a block diagram showing an embodiment of the present invention.

FIG. 4 is a flowchart of the measuring method of the present invention.

FIG. 5 is a block diagram showing a conventional method of measuring a 4-port circuit.

[Explanation of symbols]

 1 port 1 2 port 2 3 port 3 4 port 4 5 4 port circuit 6 1st measuring end 7 2nd measuring end 8 Load (TRL calibration standard) 9 Transmission line with short electrical length (TRL calibration standard) 10 Transmission line with long electrical length (standard device for TRL calibration) 11 First port of vector network analyzer 12 Second port of vector network analyzer 13 Coaxial non-reflection terminal 1 14 Coaxial non-reflection terminal 2 15 Computer 16 None Reflection termination 1 17 Non-reflection termination 2

Claims (1)

[Claims] 1. A first connected to the first and second measuring ends.
And a method of measuring the S parameter of an N (integer of 3 or more) port circuit using a vector network analyzer having a second measurement port, wherein a load of one port having a large reflection coefficient and a different electrical length are used.
Equipped with two transmission lines as a calibration standard, connecting the first measuring end and the load to measure the reflection coefficient,
The reflection coefficient is measured by connecting the second measuring end and the load, and a transmission line having a short electrical length is inserted between the first measuring end and the second measuring end to obtain four S parameters. The measurement is performed, a transmission line having a long electrical length is inserted between the first measurement end and the second measurement end, and four S parameters are measured, and the first measurement end and (N-2) pieces are measured. The transmission coefficient of the electrical length is sequentially inserted between the non-reflective terminators of the above, and the reflection coefficient is measured. From these measurement results, the error from the first measurement port of the vector network analyzer to the first measurement end is measured. The factor S parameter, the error factor S parameter from the second port to the second measurement end, and the error factor reflection coefficient of the (N−2) non-reflection terminators are calculated, and there are N of the N port circuits. The above (N-2) is added to (N-2) ports that are not used for measurement. Connecting the non-reflective terminators, measuring the S-parameters of the circuit, and removing the S-parameters and reflection coefficients of the error factors from the measured S-parameters to obtain the true S-parameters of the N-port circuit. A characteristic S-parameter measuring method for a multiport circuit.