SU1663578A1 - Circuit analyzer - Google Patents

Abstract

This invention relates to a radio measuring technique. The purpose of the invention is to reduce the measurement error. The analyzer contains a microwave signal generator 1, a control and computing unit 2, an in-phase quadrature converter 3, tees 4 and 5, measuring heads 6 and 16, controlled attenuators 7, 8 and 9, a unit 10 for generating measuring signals, an adder 11, studied quadrupole 12, controlled phase shifters 13, 14 and 15. The reduction of measurement errors introduced by the mismatch in the measuring path is achieved by maximally approximating the directional incident wave coupler, which is used as a tee 4, to the object measurement, which is used as the analyzed quadripole tee 12. Placement 4 directly with the input unit 10, and use a directional coupler as a tee 4 reduces the mismatch error in 2 - 3 times. 3 il.

Description

about ave eaten vi

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figure 1

The invention relates to radio metering technology and can be used to create multi-functional parameter meters (reflection coefficients and transmissions of S-parameters, group delay time, total input resistances and conductivities) of microwave two- and four-port networks.

The purpose of the invention is to reduce the measurement error.

Figure 1 shows a structural electrical circuit of a network analyzer; 2 is the same, the measuring signal generation unit; in FIG. 3 - the same, in-phase-square converter.

The network analyzer (figure 1) contains the generator 1 of the microwave signal, the control and computing unit (UVB) 2, the in-phase quadrature converter (UPC) 3, the first 4 and the second 5 tees, the first measuring head 6, the first 7, the second 8 and third 9 controlled attenuators, the measuring signal generating unit 10, the adder 11, the quadrupole 12 under study, the first 13, the second 14 and the third 15 controlled phase shifters and the second measuring head 16,

Block 10 (figure 2) consists of a directional coupler (BUT) 17, matched load 18 and matching device 19.

UPC (FIG. 3) includes the first tee 20, BUT 21, the second 22 and the third 23 tees, measuring heads 24-27 and the matched load 28.

The network analyzer operates as follows.

The measurement result of the Sfk parameter of the studied quadrupole. 12 is determined from the ratio of the voltages Vx, VY and V4 to the voltage Vn. Using the automatic power adjustment circuit (APM) of the generator 1 and the corresponding selection of the parameters of the network analyzer circuit, a quadratic mode of operation of the measuring heads 6 and 16 is provided. Therefore, it is assumed that the voltages Vn and V4 are respectively equal;

Vn m0 I Un I2: (1)

V4 n0IU4l2, (2)

where m0 and Po - scalar constants, taking into account the values of parameters of measuring heads 6 and 16.

To simplify the recording of the ratios of voltages Vx, VY, V4 to Vn, the value m0 is taken to be 1 for Sik Ui / Un, I 1.2, which allows you to record the ratios of voltages Vx. VY and V / i to Vn in the following form:

 e, + M ,, Y + ЈJ (x4Y) vn

 + WjXthjY E X1 2)

Q.-rteiif tv ")

with X ReStk: Y ImS.k. (5)

Constants ei - EL. mi. m2, m02, n0 are determined from calibration and measurements. The calibration process is carried out automatically by commands from UVB 2. After pressing the Calibrate button on the front panel of UVB 2, the controlled attenuators 7–9 and the controlled phase shifters 13–15 are reset to the initial position. measurement of signals Ui and IJ2. Therefore, when the signal Ui is measured. automatically

a controlled attenuator 9 is turned on to turn off the signal U2, and when measuring the signal Ua, a controlled attenuator 8 is turned on automatically to turn off the signal Ui.

When calibrating the network analyzer, any of the signals (Ui or 1/2) can be used. For this purpose, controlled phase shifters 13 and 14 are installed in both measuring channels. Let's pretend that

the signal Ui (parameters Sik) is measured. those. controlled attenuator 9 is closed.

Under such conditions, the initial position is that the controlled attenuators 7 and 8 are opened, controlled

Phase shifters 13 and 14 are set to p and the operator’s command is displayed on the UVB 2 display screen. Turn on the direct coupling of the measuring path, i.e. ensure compliance

  one; Y 0. (6)

After the operator performs this command and presses the Calibration button again, the UVB 2 command turns off the signal using a controlled attenuator 8, thereby simulating the condition

Sik X -HY 0. (7)

The UVB 2 memory records the measurement result.

Ri Ei; Si Ј2. (8)

The controlled attenuator 8 returns to its initial position, and the Ko signal is switched off by means of the controlled attenuator 7. This will ensure that:

| Uil -1: lUol 0; X2 + Y2 1 (9)

second gauge measurement

Rz without; S2 &i; 0.2 п0, (10)

the result of which is entered into the memory of the UVB 2. The values found Ј1 - EA and pr are substituted into formulas (3). As a result, the system of quadratic equations (3) reduces to a system of linear equations for Xi Y:

i

R-R-, -; r Q m.X m, V;

u L

5, lM)

5 5 -, - -Ј- Q rnl,

where the variables R and S are determined from the results of further measurements of R, S and Q.

Then both signals (U0 and Ui) are turned on, thereby ensuring the fulfillment of condition (6) and the measurement result is entered in the memory of CBEE 1

R 3 mi 1

S 3-m2), (12)

after which, using a controlled phase shifter 15, a phase shift p0 is introduced, approximately equal to

po - (13)

and a fourth calibration measurement is taken. Measurement results

R (4 miXo + niY0 -f4

S 4 m2X0 + n2Y0 JIm /

is stored in the memory of the UVB 2, where Ho is PO cos (pa, Yo is PO sin (; d-measurement p, entered by the controlled phase shifter 15.

Then, using a controlled phase generator 13, a second phase shift is introduced, approximately equal to:

 , Q5)

and making the fifth calibration measurement.

Measurement result

(XuXo-YllYohni (XoYlJ + X, JY0) r,

(Xl, Xo-YuY0) -1-n2 (X0Yli + XuYo) J is stored in the memory of UVB 2, where

Xu pu cos; Yu sin: () the factor in front of mi and gp2 is equal to p0-ri cos (p0 +), and the factor in front of um and P2 is equal to p0ri sin ((p0) where /, is the change in / 9 introduced by the controlled phase shifter 13.

After this, the resetting of the controlled phase shifter 15 and the sixth calibration measurement are carried out.

Measurement result

R e miXu + niYu

S e t2Hi + n2U is stored in the memory of the UVB 2.

From the system of equations (12). (14), (16) and (17) The UVB 2 finds the values of the constants mi, GP2, ni, P2, stores them in the memory of the UVB 2 and returns the controlled phase shifter 13 to the initial position. This completes the calibration process.

The quadrupole 12 under study 12 is inserted into the rupture of the measuring path of the block 10 and the measurement result is entered into the memory of the UVB 2

R ik miXik + niYik

S, k m2X, Hri2Y, k) .U9)

From the solution of the system of equations (19) is the measured parameter

S, v - X, k iYik (20)

A reduction in the calibration errors of the network analyzer is achieved by a transition from the calibration of the network analyzer with a single phase shifter, the magnitude and phase of the transfer coefficient of which is specified with an error of at least +0.5 dB modulo + 5 ° in phase, to a calibration using two phase shifters, transmission ratios which do not affect the result of the calibration of the network analyzer.

The introduction of the measuring head 16 allows us to simplify the data processing algorithm by reducing the system of quadratic equations (3) with respect to X and Y by substituting Q from (A) into them for the system of linear equations (8), (11), (12), (14) , (16) and (18) in the calibration process and to the system (19) in the measurement process

Solving the system of equations (3) with respect to X and Y using UVB 2 in the prototype is possible only by the method of successive approximations and takes a long time, which does not allow realizing the panoramic measurement mode in the frequency band in real time.

Solving the system of equations (11) with respect to the X and YB network analyzer is reduced to the direct calculation of X and Y by formulas.

(21)

. -

50

55

and is not difficult to implement using microprocessor UVB 2.

Reducing the measurement errors of the network analyzer introduced by the mismatch in the measuring path of the network analyzer is achieved by maximizing the incident wave coupler Un, which is used as a tee 4, to the measurement object - the quadrupole 12 under study. As this tee of a directional coupler with a VSWR of the primary path of not more than 1.1, it is possible to reduce mismatch errors by a factor of 2-3.

Claims (1)

The invention includes a network analyzer containing a microwave signal generator connected in series, the first and second tees and the first measuring head, the first controlled attenuator connected to the first input of the quadrature-phase converter, the second and third controlled attenuators connected to the inputs of the adder, whose output connected to the second input of the in-quadrature converter; the forming unit of measuring signals, the input of which is connected to the output of the second tee, and the outputs are to connect the studied quadrupole, and the control-computing unit, the inputs of which are connected to the output of the first measuring head and the output of the in-phase-quadrature converter, and the outputs to the control inputs of the first, second and third controlled attenuators and the microwave signal generator , characterized in that, in order to reduce the error 2 0 five 0 the first controlled phase shifter connected between the second output of the first tee and the first controlled attenuator, the second controlled phase shifter connected between the output signal of the incident wave of the measuring signal generation unit and the second controlled attenuator, the third controlled phase shifter connected between the output of the signal of the last wave unit of the formation of the measuring signals and the third controlled attenuator, the adder is made in the form of a double waveguide tee, to the second Exit is coupled introducing a second measuring head, wherein the control inputs of controlled phase shifters are connected to additional outputs capstan control and computing unit. FIG. 3