SU1538149A1 - Device for measuring amplitude-frequency and phase-frequency characteristics of four-terminal networks having frequency converter - Google Patents

Abstract

This invention relates to a measurement technique. The purpose of the invention is to improve the accuracy of measuring the phase-frequency characteristics of quadrupoles with a frequency converter. By means of the control unit 3, the oscillators 1 and 2 of the oscillating frequency in the microwave range are synchronously pumped. Phase-locked loop systems are composed of mixers 7 and 11, phase detectors 12 and 16, and a tunable intermediate-frequency generator 17. Using switches 6, 8, 9, 15, 18, 20, a circuit is implemented for measuring the phase difference between the two-port 13 under study and the reference mixer 14. Before the measurement, the electrical lengths of the measuring and reference channels are equalized. The attenuation of the attenuator 5 compensates the gain of the amplifier 10. Using the heterodyne signal supplied from the second output of the tunable generator 17, the signals of the first intermediate frequency in mixers 21 and 22 of the intermediate frequency of the measuring and reference channels are converted into signals of the second constant low intermediate frequency Ω, which are supplied to the input of the indicator 23, the result of the comparison enters the decision device 24. The device also contains 4 signal dividers and 19 signals. 2 Il.

Description

The invention relates to measurement technology and can be used to measure the phase-frequency and amplitude-frequency characteristics of quadrupoles containing a frequency converter (mixer), a frequency converter, in the ultra-high frequency (EH) frequency band.

The purpose of the invention is to improve the accuracy of measuring the phase-frequency characteristics of quadrupoles with a frequency converter.

The drawing shows a block diagram of a device for measuring the amplitude-frequency and phase-frequency characteristics of quadrupoles with a frequency converter.

The device contains oscillating frequency generators 1 and 2, a control unit 3, a divider 4 signals, an attenuator 5, a switch 6, a phase locked loop 7, switches 8 and 9, an amplifier 10, a phase locked mixer 11, a phase detector 12, a quadrupole under study 13 with frequency converter, reference mixer 14, switch 15, phase detector 16, tunable intermediate frequency generator 17, switch 18, divider 19 signals, switch 20, intermediate frequency mixer 21 of the measuring channel, mix 22 Tel intermediate reference channel frequency indicator 23 and a decision unit 24.

The first control input of the oscillating frequency generator 1 and the control input of the oscillating frequency generator 2 are connected to the first and second outputs of control unit 3, respectively, the input of the oscillating frequency generator 1 is connected to the input of splitter 4 signal and the first input of phase auto-tuning mixer 7, oscillating frequency generator 2 connected to the first (heterodyne) inputs of the studied quadrupole 13 with the frequency converter and the reference mixer 14 and the second input of the mixer 7 of the phase-locked loop, the output to torogo connected to the first input of the phase detector 12 and the first input of the mixer 11 of the phase construction avtopod- frequency kotorog second input coupled to the second output of tunable oscillator 17 of intermediate

frequencies. The output of the phase locked phase mixer 11 is connected to the peen input of the phase detector 18, the input of which is connected to the third output of the tunable intermediate frequency generator 17, the input of which is connected to the third output of the control unit 3, the output of the phase detector 16 is connected to the third control input of the generator and 1 swinging frequencies. The output of the studied quadrupole 13 with a frequency converter through the intermediate frequency mixer 21 of the measuring channel is connected to the first input of the indicator 23 whose second input is connected to the output of the intermediate frequency mixer 22 of the reference channel, and the heterodyne inputs of the 2J and 22 intermediate frequencies of the measuring and reference channels are respectively connected to the second the output of the tunable intermediate frequency generator 17, the first output of which is connected to the second input of the phase detector 12, the output of which It is connected with the second input of the oscillating frequency generator 1. The input of the decisive device 24 is connected to the output of the indicator 23. The first output of the divider 4 signals through an attenuator 5 is connected to the first fixed contact of the switch 6, the second fixed contact of which is connected to the second fixed contact of the switch 9, the movable contact of the switch 6 through the amplifier 10 is connected to the movable contact of the switch 15, the first fixed contact of which is connected to the first fixed contact of the switch 9, and the second fixed contact to the second fixed contact of the switch 8, ne vy fixed contact of which is connected to the second output signal of divider 4, the movable contact of which is connected to a second (signal) input of the test quadrupole 13 with a frequency converter. The movable contact of the switch 9 through the reference mixer 14 is connected to the movable contact of the switch 18, the first fixed contact of which is connected to the fixed fixed contact of the switch 20, the movable contact of which is connected to the second (signal) input of the mixer 22 of the intermediate clock

the reference channel motes, the second fixed contacts of the switches 58 and 20 are connected to the first and second outputs of the signal divider 19, the input of which is connected to the first output of the tunable intermediate frequency generator 17.

Control unit 3 contains a resistor unit, a power supply unit, a sweep generator, a tuning time switch, an operation mode switch, an adder, a mark generator, a digital indicator, and is a device commercially available as part of a sweeping frequency generator.

The digital indicator is a B2-29 voltmeter.

The device works as follows.

The oscillators 1 and 2 of the oscillating frequency can operate in a variable intermediate frequency mode and in a constant intermediate frequency mode.

In the variable intermediate frequency mode, the voltage from the control unit 3 establishes the initial difference between the frequency-J1 of the oscillating frequency generator 1 and the frequency L2 of the oscillating frequency generator 2, equal to the initial intermediate frequency of the analysis of the quadrupole with frequency conversion under study. The same voltage sets the initial value of the first variable intermediate frequency 0) 3 signals of the tunable intermediate frequency generator I7, taken from the first output, equal to the initial frequency of the analysis band.

Then, with respect to the oscillating frequency generator 2 tuned to a fixed frequency, the oscillating oscillator 1 oscillating frequency 1 is switched on in the range equal to the analysis band at the intermediate frequency of the quadripole 13 under test with the frequency converter. At the same time, synchronizing with the oscillating frequency generator 1, sweeps and tunes the intermediate frequency generator 17 in a given range of intermediate frequencies. Simultaneously with the signals of the first intermediate frequency, in the tunable intermediate frequency generator 17, auxiliary intermediate frequency signals are generated538149

five

0

five

0

five

0

five

0

S

you, taken from its second output, are shifted by a constant value -D, relative to the signals of the first intermediate frequency with accuracy to the phase at any frequency point. The part of the signals of the first variable intermediate frequency shee from the output of the phase locked loop mixer 7 is fed to one of the inputs of the phase locked loop mixer, where it is mixed with the auxiliary frequency signal from the tunable intermediate frequency generator 7.

The resulting signal of the second constant intermediate frequency S1 from the output of this mixer is fed to one of the inputs of the phase detector 16, which is compared with the reference signal of frequency 51 produced in the tunable intermediate frequency generator 17 and removed from its third output, and the result is compared with output of the phase detector 16 is supplied to one of the inputs of the oscillating frequency generator 1 by controlling its frequency so that the difference between it and the frequency of the oscillating frequency generator 2 with an accuracy to the phase of the sub It is equal to the current value of the first variable of the intermediate frequency and

In the mode of constant intermediate frequency W3, the control unit 3 controls the oscillators J and 2 oscillating frequencies s of the microwave range synchronously, while at one input of the first mixer 7 of the phase-locked loop, some signals are output from the outputs of these generators, and the resulting mixing the signals of the first intermediate frequency from the output of the mixer 7 of the phase-locked loop frequency are fed to one of the inputs of the phase detector 12, where they are compared with the signals of the first intermediate frequency used by as a reference from the first output of the tunable generator 17 intermediate frequencies. The result of the comparison is applied to one of the inputs of the oscillating frequency generator 1, controlling its frequency in the wobble process so that the frequency difference between it and the oscillating frequency generator 2 is equal to the first intermediate frequency to which the tunable intermediate frequency generator is tuned.

 B position 1 of switches b, 8, 9, 15, 18, and 20 — a circuit is implemented for measuring the phase difference between the quadrupole 13 under study with the frequency converter and the reference mixer 14. Before measuring, the electrical lengths of the measuring and reference channels and the channels of the local oscillator signals are aligned branching, marking of the device channels is carried out so that, when measuring the phase difference, the phase in the measuring channel is reduced, and in the reference channel - subtracted in this difference.

In the circuit for measuring the phase difference, the signal from the oscillating frequency generator 1 is divided by a transmitter of 4 signals into two channels — a measuring and a reference.

The signal in the measuring channel can be represented as

and; (Gj, t + tf ;, s

where and is the magnitude of the signal in the measuring channel UJn, is the amplitude value of the signal

la, (/ - the initial phase of the signal in

measuring canapes at the signal input of a quadrupole with a frequency converter. The signal in the reference channel can be represented as

 uJ-TCsi t f

(2)

where TJ t - the signal value in the reference

channel1, U - amplitude value of the signal, la A

P1 - the initial phase of the signal in

the reference channel at the inlet of the reference mixer. The signal of the measuring channel through the switch 8 is fed to the signal input of the quadrupole 13 under study with a frequency converter, and the signal of the reference channel through the attenuator 5, switch 6, amplifier 10, switch 15 and switch 9 is fed to the signal input of the reference mixer 14, where it is converted by signal from oscillator 2 frequency in the first

Jq 15

381498

(variable) intermediate frequency W}. In this case, attenuation of the attenuator 5 compensates for the gain of the amplifier 10. Frequency conversion can be as

 up,

to razheniyu

and down, and you answer W3 ui, + Ы2,

(3)

0

five

0

"

0

five

where (j) 3 is the first intermediate frequency j coz is the frequency of the signals of the second

oscillating frequency generator j

Ы, is the frequency of the signals of the first oscillating frequency generator. Suppose that the proposed device has a transformation

UJ3 s, u) 2. (four)

Then at the output of the studied quadrupole 13 with a frequency converter, the signal described by the expression

T1 s- (s, -) t +, - t / j + 41 / J, (5)

where Uj is the signal of the first intermediate frequency in the measuring channel;

U is the amplitude value of the signal; C - the initial phase of the signals from

oscillating frequency generator 1 at the signal input of the quadrupole 13 under study with a frequency converter; 7 initial phase of signals from

2

oscillator frequency generator 2 at the heterodyne input of a quadrupole 13 under study with a frequency converter;

D is the desired phase shift and the studied quadrupole 13 with a frequency converter, which it introduces into the phase of the signals of the first intermediate frequency during the conversion. Taking into account the condition (4); we have that

Us U m3sin (wst + + 44-1 / 41. (6) After the conversion, at the output of the reference mixer 14, the signal described by the expression

j - UjUeinC (u,) t + tf {+ + & H3 + atf4- if, (7)

de U C - signal of the first intermediate frequency in the reference

Channel: „“

itz - the amplitude value of the signal, Yu

If - the initial phase of the signals

from the oscillating frequency generator 1 at the signal input of the reference mixer;

Cf is the initial phase of the ts signals from the oscillating frequency generator 2 at the heterodyne input of the reference mixer 14;

/ jLfy phase shift attenuator 5; 20

/ Jt / 3 phase shift amplifier 10;

The flUV phase shift of the reference mixer 14 is introduced by it into the phase of the signals of the first intermediate frequency in the conversion process. Taking into account the condition (4), we have that

j jsin (+ if4, + & 4t + LCL +

(eight)

+ tf4 1 / j).

The signals of the first intermediate frequency from the outputs of the studied quadrupole 13 with a frequency converter and reference mixer 14 are supplied to the signal inputs of the mixers 21 and 22 of the intermediate frequency of the measuring and reference channels, respectively, where using a heterodyne signal supplied from the second output of the tunable generator 17 intermediate the frequencies are converted into signals of the second constant low intermediate frequency Si, which are fed to the inputs of the ratio indicator 23, where the ratios of their amps are compared itud and the phase difference, and the comparison result is supplied to a decision unit 24, which is fixed.

The assumption that the amplitude-frequency and phase-frequency characteristics of the mixers 21 and 22 of the intermediate frequency of the measuring and reference channels are identical, and the ratio indicator 23 measures the phase difference between the signals of the measuring and reference channels of the second, low intermediate frequency, the result of comparing the difference

J538J4910

phases in the indicator. can be quickly represented by the expression

s

0

five

0

5 0 45 0

55

And KfOJa, Up (H + H, - H, + i / 5 - 9 Va «/ 4) t (9)

where A is the measured phase difference in

degrees, taking into account the sign of j K, is the coefficient of proportionality.

f (uj,

U) Functions, realizable by phase

the detector.

Virtually all microwave attenuators have a linear phase-frequency characteristic and, therefore, their electrical length can be compensated for by the electrical length of the microwave path. Taking this circumstance into account, it can be argued that the phase shift and Tsg of the attenuator 5 can be compensated for by the electrical path length of the measuring channel h, i.e.

c. I / + 4lfr (S)

Taking into account (10) and believing that the electrical lengths of the measuring and reference channels and the local oscillator channels (, 1/5) are equal in pairs, we get i / j 2 Relationship indicator 23 will record the result of measuring phase shifts in the form

A (yCh, - - Champions League). (YU

In position 2 of the switches 6.8, 9, 15.18, and 20, a circuit is implemented for measuring the sum of the phase shifts of the reference mixer 14 and the quadripole 13. under study with a frequency converter.

The signal of the first variable intermediate frequency Ш3 from the first output of the tunable intermediate frequency generator 17 by the signal divider 19 is divided into two channels: measuring and reference.

The signal of the measuring channel through the switch 18 is fed to the output of the intermediate frequency of the reference mixer 14. In this case, the reference mixer 14 and the quadripole 13 under study with a frequency converter switches 6, 8, 9 and 15 are connected in series so that the signal of the microwave quadrupole 13 with a frequency converter through the amplifier 10 is connected g

1115

the input signal of the microwave reference mixer) 14. In this case, the input signal of the microwave reference mixer 14 as a result of the inverse transformation and its selective properties appears the signal of the total frequency (s3 + wg) w, quadrupole 13 with a frequency converter. At the input of the studied quadrupole with a frequency converter, a signal is taking place, which is described by the expression

u m and; sin (yue + w2) t +1 /; +

+ + if,, (12)

where dtf is the initial phase of the signal from

tunable generator 17 intermediate frequencies in the measuring channel; L phase shift amplifier 10; Atf, - phase shift introduced by the reference

the mixer 14 when converting the intermediate frequency signal CjOj Lf to the phase of the signal — the initial phase of the signal from

a second oscillating frequency generator at the heterodyne input of the quadrupole 13 under study with a frequency converter.

The gain of amplifier 10 is set in such a way as to compensate for the conversion loss of the reference mixer 14. Consequently, the amplitude of the signal at the input of the quadrupole 13 under study with the frequency converter does not practically change as compared with its switching scheme for measuring the difference in phase shifts.

After conversion in the studied quadrupole 13 with a frequency converter, a signal appears at its output

U Tilsit (w3 + wa -Y2H +

I /,

- if + а м + л ц „+ and U sin (u) 3t + Ul + - Ч + aif, +

that

+ dche + dm,)

(13)

Where

 - the initial phases of the signals is opposite to the hetero49

12

the home channels of the reference mixer J4 and the quadripole 13 under study with a frequency converter} AC - the phase shift of the reference mixer 14.

The connection of the local oscillator to the reference mixer 14 and the quadrupole 13 under study with the frequency converter remains unchanged compared with the circuit for measuring the phase difference and therefore

U UmjSinCwjt + з + & Ч, + ЧЧ3 +

+ d%)

(14)

five

0

0

five

0

Then this signal of the first variable intermediate frequency is fed to the signal input of the intermediate frequency mixer 21 of the measuring channel, where, using the heterodyne signal from the second output of the tunable intermediate frequency generator I7, as well as in the reference channel, the intermediate frequency reference channel 22 is converted into signals of the second constant intermediate frequency, which are fed to the measuring and reference inputs of the ratio indicator 23.

Considering that the relationship indicator 23 determines the phase difference between the signals at its first and second inputs, the result can be represented as

In K, - f (u 3, UJ)

  + 4iX, 4 4if4 - H, (15)

where K, is the proportionality coefficient;

f (u 3,

Up is a phase detector function,

indicator,

C1 - the initial phase of the signal from the tunable generator 17 intermediate frequencies in the reference canape. With equal electrical lengths of the measuring and reference channels

“;

(sixteen)

The relationship indicator 23 will record the measurement of the sum of the phase shifts in the form

B and if3 + fll (4l (17)

13J5381

which enters solver 24. After the sum of the phase shifts B arrives therein, it produces a solution to the system of equations

L W, - and 1 / e - & if.

& Lf, + DU3 + & Ts4

one

08)

and determining the true value of the phase shifts introduced by the studied 4-1 pole 13 with a frequency converter during the conversion to the phase of the intermediate frequency signal in the form

/,

A t B

(nineteen)

taking into account the signs of the sum and the phase difference.

As can be seen from expression (19), when substituting the values of A and B into it, the phase shift of the amplifier 1 OL if3 when measuring the sum and the phase difference mutually compensates and does not affect the measurement result.

Compensation of the phase shift and q of the amplifier 10 occurs only if, when measuring the difference in phase shifts, it is included in the reference channel before the reference mixer 1 4.

The oscillating oscillator 1 of the oscillating frequency is synchronized with the oscillator 17 by sawtooth voltage from the control unit 3, the amplitude of which is set using the controls on its front panel. The constant shift I. is selected as follows: this is the second intermediate frequency of the device, on which the indicator 23 operates, its value in order to avoid interference should not be a multiple of the 50 Hz frequency of the network. The value I must be such as to ensure the required bandwidth of the indicator 23, to ensure its required speed and not to lie within the range of the first variable intermediate frequency.

The frequency of the generator 1 is controlled, for example, by means of a modulation coil built into the generator, which changes the magnetic field of a sphere made of an yttrium garnet.

Knowing the true phase shift of the studied quadrupole with a frequency converter at a frequency point, it is possible, but to determine the true phase shift of the reference mixer at this point, and by the known difference phase frequencies

81

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five

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35

55

40

45

0

4914

The characteristic characteristics of the reference mixer and the studied quadrupole with a frequency converter determine the true phase shift at any other frequency point.

The proposed device allows to determine the absolute value of the phase shift introduced by a two-port network with high accuracy (5-15 °).

Claims (1)

Invention Formula A device for measuring amplitude-frequency and phase-frequency characteristics of quadrupoles with a frequency converter, containing a series-connected tunable intermediate frequency generator and a first phase detector, serially connected control unit, a first oscillating frequency generator, a first phase-locked frequency-tuning mixer, a second phase-locked frequency tuning mixer and a second phase detector connected in series a second oscillator of oscillating frequencies and terminals for connecting The studied quadrupole with a frequency converter, an intermediate frequency mixer of the measuring channel and the first indicator, the first signal divider, the reference mixer and the intermediate frequency mixer of the reference channel, the output of which is connected to the second input of the first indicator, is connected to the output of the first phase locked loop mixer the second input of the first oscillating frequency generator, the output of which is connected to the input of the first signal divider, the third input of the first generator The oscillating frequency is connected to the output of the second phase detector, the input of the second oscillating frequency generator is connected to the second output of the control unit, the third output of which is connected to the input of a tunable intermediate frequency generator, the second and third outputs of which are connected respectively to the second input of the second phase locked loop mixer and the second the input of the second phase detector, the output of the second oscillating frequency generator is connected to the second input of the first phase locked loop mixer, rearrange second entrance 151 The intermediate frequency generator is connected to the second input of the intermediate frequency mixer of the measuring channel and to the first input of the intermediate frequency mixer of the reference channel, the first input of the reference mixer is connected to the output of the second oscillating frequency generator, characterized in that, in order to improve the accuracy of measurements of the phase characteristics of four-poles with a converter frequencies, it additionally includes six switches, an attenuator, an amplifier, a second signal divider and a resolver, turn connected to the output indicator, the first output of the first divider signals through an attenuator connected to the first fixed contact of the first switch 1, the second fixed contact which is connected to the second fixed contact of the third switch, the movable contact of the first switch via an amplifier connected to the movable contact of the fourth switch, the first nepod 0 81 five 0 five Vision contact of which is connected to the first fixed contact of the third switch, and second contact of the fixed contact with the second fixed contact of the second switch, the first fixed contact of which is connected to the second output of the first signal divider, the movable contact of the second switch connected to the terminals for connection the second input of the studied quadrupole with a frequency converter, the movable contact of the third switch through the reference mixer is connected to the movable contact of the fifth switch, n The first fixed contact is connected to the first fixed contact of the sixth switch, the moving contact of which is connected to the second input of the reference channel intermediate frequency mixer, the second fixed contacts of the fifth and sixth switches are connected to the first and second outputs of the second splitter, the input of which is connected to the first output of the tunable intermediate frequency generator.