SU828115A1 - Device for measuring complex impedance - Google Patents

Description

one

This invention relates to a technique for measuring the impedances of an antenna-feeder path and antennas.

A device for measuring complex impedances is known, comprising a generator, an indicator and an unbalanced bridge with selected shoulder impedances, which allow determining the active and reactive components of complex impedance 1 using a three-dimensional reflection coefficient module.

The disadvantage of the device is low measurement accuracy in a wide frequency range due to imbalance of the bridge,

The aim of the invention is to improve the measurement accuracy of the reflection coefficient modulus in a wide frequency range.

The goal is achieved in that a device containing a generator has an unbalanced bridge composed of two series-connected resistors, the first of which is connected to the moving contact of a two-position switch by one of the conclusions, the first three fixed contacts of which are connected to the second fixed contacts of the switch, the second movable contact of which is connected to the device case, with the first output

a capacitor and a movable contact of the switch, the fixed contact of which is connected to the second output of the capacitor and to one of the inputs of the device, the second input of which is connected to the second output of the second resistor and the indicator, one of the inputs connected at the junction of two resistors and the second input to the housing devices, a second switch, a controlled voltage divider, an amplifier, a reference voltage source input, a current transformer, a reference element, a feedback element, and a control button, and one From the terminals of the first mentioned resistor, it is connected to one of the secondary terminals of the current transformer, the second terminal of which is connected to the second input of the device and to the sub contact of the second switch, the fixed contact of which is connected to the device case, and the excitation winding of the current transformer is connected to one of the terminals the ballast resistor is connected to the device case, and the other output through the amplifier is connected to the output of a controlled voltage divider, the input of which is connected to the output of the generator, and the control input d voltage divider is connected to the output of the comparison element, one of whose inputs is connected to the source entry

the reference voltage, the second input to the control button, and the third input through the feedback element connected to the output of the indicator, made adjustable, while the indicator is designed as a series-connected amplifier, frequency converter, second input connected to the output of the local oscillator, intermediate frequency amplifier detector, voltage limiter, and memory and coding circuits, and the secondary winding of the current transformer is made with a symmetrical output in the form of a short-circuited node located inside the ferr tovogo toroidal core with that serves, ennoy thereon excitation winding enclosed in an electrostatic shield.

FIG. 1 is a block diagram of the device; in fig. Figure 2 shows a grapho-analytical method for determining the impedance.

The device contains a controlled voltage divider 1, a broadband amplifier 2, a comparison element 3, a current transformer 4, an unbalanced bridge 5, an amplifier 6, a frequency converter 7, an intermediate frequency amplifier 8, a detector 9, a feedback element 10, a voltage limiter 11, a memory and coding circuit 12, a working frequency generator 13, a local oscillator 14, a control button 15, a two-position switch 16, a switch 17, a second switch 18, resistors 19-21, a ballast resistor 22, a capacitor 23, an indicator 24, an input 25.

The device works as follows.

Before each measurement of the reflection coefficient module, the measurement input 26 of the unbalanced bridge 5 is short-circuited by the second switch 18 to the housing. When the button 15 is pressed, the high-frequency voltage from the generator 13 enters the circuit of bridge 5 and is adjusted until the bridge sets the set value for the bridge corresponding to the module of the reflection coefficient equal to one (total reflection).

After setting a predetermined voltage level in the generator diagonal of the bridge 5, the measuring input 26 of the latter is switched off by the switch 18 from the housing and connected to the measured resistance 27, for example, the input of the feeder with the antenna.

The measurement of the reflection coefficient module is carried out at different values of the resistance R of the switched arm of the bridge 5.

The reflection coefficient module is also measured with a capacitor 23 connected in series with the measured resistance 27 and one of the resistors of the switched arm R.

The output voltage in the indicator diagonal of bridge 5 by frequency converter 7 is transformed in frequency to intermediate frequency, amplified by intermediate frequency amplifier 8, and detected by amplitude detector 9.

The voltage rectified by the detector 9 simultaneously goes through the feedback circuit 10 to the reference element 3 and through the limiter 11 to the memory and coding circuit 12. The oscillator 14 of the converter 7 uses a generator tuned simultaneously with the change in the operating frequency of the main generator 13, the frequency which is lower by the intermediate frequency of the intermediate frequency amplifier 8.

The measurement data of the three values of the reflection coefficient modulus is used to determine the complex resistance by the graph-analytical method.

The graphical method of determining the impedance using an unbalanced bridge is based on using the impedance plane (Ri ± jx), on which the circles of the equal reflection coefficient module (Fi), (G2) are constructed relative to the specified values of wave resistances i and 2, included in the shoulder 21 of the bridge (Fig. 2).

The impedance is determined by the three measured values of the reflection coefficient module (Fi), (F2) and (Fs), belonging to the respective three circumferences of the constant reflection coefficient module, plotted on a plane) with respect to resistance i

and

Two values of the reflection coefficient, for example, (Fi) and (F2), are measured at two different discrete values of the resistance of the switched arm 21, i.e.

iilL. | g 1,

riL 2 2 I I

m

1G

2

Z. GOLO

Where

B - generator design

the entrance of bridge 5;

 - measured impedance.

The third value of the measured voltage

x 2

| Гз1 Zj. - .Hdod +

It is measured with one of the discrete values of the resistance R of the switched arm, but at the same time with the additional capacity connected in series with the measured resistance. The sign of the reactive component sign of the measured resistance is a decrease (with an inductive character) or an increase (with a capacitive character) voltage in

diagonal compared to the measured voltage without additional capacitance.

The measurement error of the reflection coefficient when the current transformer secondary unit is made in the form of a thin circular disk with a ratio of length to diameter of 0.2 and an inductance of about 0.2 NGN will not exceed 2%.

Claims (3)

1. Device for measuring complex resistances, containing a generator, an unbalanced bridge composed of two series-connected resistors, the first of which is connected to a moving contact of a two-recognition switch by one of the conclusions, the first three non-contact contacts of which are connected to the second fixed contacts switch, the second movable contact of which is connected to the device case, with the first capacitor lead and the movable contact com an unloader, the fixed contact of which is connected to the second capacitor terminal and one of the device inputs, the second input of which is connected to the second terminal of the second resistor, and an indicator connected to the connection point of two resistors by one of the inputs, and the second input to the device that, in order to increase the measurement accuracy of the reflection coefficient modulus in a wide frequency range, a second switch, a controlled voltage divider, an amplifier, a reference voltage source input, a transform current, reference element, feedback element and control button; one of the terminals of the first mentioned resistor is connected to one of the secondary windings of the current transformer, the second terminal of which is connected to the second input of the device and to the moving contact of the second Switch, fixed contact which is connected to the device case, and the excitation winding of the current transformer is connected by one of the terminals through the ballast resistor to the device case, and the other terminal through the amplifier is controlled by the output A voltage divider, the input of which is connected to the generator output, and the control input of the voltage divider are connected to the output of the reference element, one of the inputs of which is connected to the input of the reference voltage source, the second input to the control, and the third input through the reverse link zi is connected to the output of the indicator, made adjustable. 2. The device according to claim 1, characterized in that the indicator is designed as a series-connected amplifier, frequency converter, intermediate frequency amplifier, detector, voltage limiter and memory and coding unit, while the second century of the frequency converter code is connected to the output of the local oscillator . 3. The device according to paragraphs. 1 and 2, characterized in that the secondary winding of the current transformer is made with a symmetrical output in the form of a short-circuited node placed inside a ferrite toroidal core with an excitation winding placed on it enclosed in an electrostatic shield. Sources of information taken into account in the examination 1. Copyright certificate № 124533, cl. G 01R 27/02, 1965 (prototype).  five