SU1659904A1 - Microwave circuit analyzer - Google Patents

Abstract

This invention relates to a radio measuring technique. The purpose of the invention is to improve accuracy. The analyzer contains grs 1 oscillating frequencies, directional couplers 2 and 3, a balanced modulator 5, mixers b and 7, a discrete phase shifter 8, the studied microwave circuit 9, a power divider 11, a control and computing unit 12, a switch 15, g - p 17 of the modulating signal and the synchronous detector 19. The goal is achieved by introducing the directional coupler 4, the matched load 10, the band-pass filter 13, the ratio meter 14, the detector 16 and the controlled amplifier 18, which are used to track the change in the output power of r-1 within all frequency range by generating a control signal to automatically adjust its power, 1 slug.

Description

The invention relates to a radio metering technique and can be used to measure the complex parameters of microwave circuits.

The purpose of the invention is to improve accuracy.

The drawing shows a block diagram of a microwave circuit analyzer.

The microwave circuit analyzer contains a oscillating frequency generator 1, first 2, second 3 and third 4 directional couplers, balanced modulator 5, first 6 and second 7 mixers, discrete phase shifter 8, microwave circuit 9 under study, matched load 10, power divider 11 , control and computing unit 12, band-pass filter 13, meter 14 ratios, switch. 15, the detector section 16, the modulating signal generator 17, the controlled amplifier 18, the synchronous detector 19,

The analyzer microwave circuits works as follows.

The output signal of oscillator 1 is frequency (o is divided by the first directional coupler 2 into two parts, one of which is the reference signal and the other is the measuring signal. In turn, the measuring signal is modulated with the help of a balanced modulator 5 with voltage Oo. At the output of the balanced modulator 5, various spectral components are formed, including (OO + OO and - OO. The carrier itself will be suppressed due to the balanced properties of the modulator. Then the measuring signal, partially reflected from the microwave frequency under study pi Referring 9 and propagates therethrough is converted into a secondary output signals of the second channels and eaten tert w of about

its directional couplers 3 and 4. These signals are fed to the first inputs of the first and second mixers 6 and 7. At the same time, the second inputs of the first and second mixers 6 and 7 receive a reference signal previously divided in half in divider 11 and at each frequency point, for example, OO alternately acquiring two values with equal amplitude and phase shifted by 90 ° (the result of operation of the discrete phase shifter 8). The signals fed to the first and second mixers 6, 7 are mixed, and useful outputs are generated at their outputs carrying the measured parameters with a frequency QO, and spurious harmonic components. Next, the signals with measurement information are fed to the inputs of the switch 15, controlled from the control and computing unit 12, which in turn connects the outputs of the first and second mixers 6, 7 to the inputs of the meter 14 and the band-pass filter 13. Moreover, during the stay of the switch 15 in one of the positions, the discrete phase shifter 8 half of this time is in one position (rotation of the signal passing through it by -45 °), and half the time in the other (rotation of phase by + 45 °). Then, the switch 15 switches to the meter 14, as well as a signal from another mixture of bodies to the band-pass filter 13. Consequently, at each frequency point of operation of the microwave circuit analyzer, four measuring signals are formed and subjected to further processing — two from the output of each of the mixers, and their amplitudes are equal

 -Ei E2,

  Ev Ј2

where K is the total transmission coefficient of the measuring channel (determined during calibration);

EI is the amplitude of the signal coming from generator 1;

E2 - the amplitude of the signal coming from the generator 17;

p is the phase shift between the reference and measurement signals.

The first and second mixers 6 and 7 also play the role of amplitude detectors of the phase-shift signal, which is formed by manipulating the phase of the reference signal as it passes through the discrete phase shifter 8. Moreover, the presence of a signal that is the result of amplitude detection of the phase-shift signal is easy to demonstrate outcome of the following.,

Phase-manipulated oscillations can be represented as

Don Um on COS UAj t + # (t) Umon COS t) cOS fifot - Um on Sin 6 (1) -SinftJot,

te, we get two amplitude-manipulated oscillations that add up in quadrature. In this case, 6 () changes

ranging from -l / 4 to l / 4. Since cos l / 4 cos (- l / 4), cos $ (t) const and specifically for these limits of change. cos $ (t) Vo / o On the other hand, sin 6 (1) is decomposed into a row

one

sln (t) 4 / 7rslrt9maxc (slnQt 4- sirOQt + ...)

2l

about

where Q - y is the frequency of manipulation of the output signal of the discrete phase divider 8.

sin Fpahs Get

sinflft) 2-- (sinQt + gSinSQ t + -,.)

Substituting these values into the original expression, we obtain, taking into account the obvious transformations

, -vTu,

vf ,,

Uon Y j Upwocouifci - j cos (. + A) +

thirty

 + 11. “| (th) (ub-3tlX

coi (tn, -f 3ft) +

Thus, we actually get the AM oscillation spectrum, to which the first or second mixer 6 or 7, which plays the role of an amplitude detector, reacts

So, the harmonic component of the output Q spectrum of the first or

the second mixer 6 or 7, as well as the series of its closest harmonics ZY, 5Q, 7Q, 9Q can be used as a signal to automatically adjust the power of the APM generator 1, since their value

depends only on the output power of the generator 1, propagating in the reference channel, and does not depend on changes in the power in the measuring channel due to the connection of various microwave circuits under study.

In this case, the role of the detector is performed by the mixers themselves without the use of additional detector sections and the directional response of the AWP loop, which improves the measurement accuracy and simplifies the structure of the microwave waveguide path,

Further, the signal from the output of the first or second mixer 6 or 7 goes to the input of the bandpass filter 13, the passband of which includes frequencies Q, 3Q 5Q, etc.

as long as the component (2n 1) - Q is still quite significant from the energy point of view. It was established experimentally that it is possible to limit the value to 9 Q. To make sure that the QH frequency and the QO modulation frequency do not affect each other, it suffices to compare them. Usually Q 256 Hz, Оо 100.000 Hz Gauge 14, the input of which receives a signal from the output

mixer has a selective input

QO modulation frequency. thus, various parasitic harmonics and combinations are filtered out. Upon passage of the bandpass filter 13, the signal enters the detector section 16, which is used to detect the low-frequency signal, turning it into a constant voltage, which is controlled by the controlled amplifier 18. The signal from the generator 17, fed to the controlled amplifier 18, is sent to monitors changes in the output power of the generator 1 and is fed to the input of the AWP generator 1, as well as to the second input of the meter 14, since the power of the generator 1

can within the entire frequency range

change several times, then the AWS system cannot sufficiently provide constant output power. These deviations are eliminated by the use of a meter 14, the output of which varies depending only on the microwave circuit under study, but not on the oscillations of the power of generator 1, since these changes lead to changes in the signal from the output of controlled amplifier 18, and the ratio of signals from both inputs, meter 14 does not change.

With the meter 14, the signal arrives at the synchronous detector 19, which detects synchronously with the signal from the generator 17, and at the output of the detector 19 we obtain constant voltages carrying information about the measured parameters. The information is then processed in the control and computing unit 12 according to known

algorithms.

Claims (1)

The invention The analyzer microwave circuits, containing a series-connected generator . oscillating frequency and the first directional coupler oriented to PA. five ten 20 25 30 35 0 45 50 giving a wave, the output of the secondary channel of which is connected to the input of the discrete phase shifter; the second output is with the control input of the switch, the third output is with the control input of the discrete phase shifter, and the input is with the output of the synchronous detector, the power divider, the first output of which It is connected to the first input of the first mixer, and a second directional coupler, the output of the primary channel of which is intended to connect the microwave circuit under study. the reflected-wave oriented output of the secondary channel is connected to the second input of the first mixer, which is (in order to increase accuracy, the switch output is connected to a controlled one through the serially connected the input of the input controlled amplifier, whose control input is connected to the output of the modulating signal generator, and the output to the first input of the input ratio meter and the power control input of the sweeping frequency generator, the second input measurement The relationship body is connected to the switch output, and the output is connected to the signal input of the synchronous detector. channel is connected to the second input of the entered second mixer, the first input of which is connected to the second output of the power divider, and the output to the second input of the switch, while the output d discrete phase shifter is connected to an input power divider, a balanced modulator connected between the output of the first primary channel and the inlet channel pervichno.o second directional couplers.