SU1255987A1 - Device for measuring group lag time of sweep-frequency generators - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to increase the resolution and increase the speed of the device. The device contains the oscillating frequency generator 1 under study, an attenuator 2, a frequency converter 4, a heterodyne 6, a frequency demodulator 7 and a receiver 10. The introduction of a second channel including an attenuator 3, a frequency converter 5 and a frequency demodulator 8 used to form the signal proportional to the phase noise of the measuring channel allows, by means of the subtraction unit 9, to compensate for the irregularities in the group delay time due to the phase noise in the measuring channel and the local oscillator 6. 3 Il. (L SD word; about 00 h srig.1

Description

The invention relates to radio engineering and can be used to measure the group delay time (GDT) of the oscillating frequency generators (HKCH), which include a linearly tunable generator- and frequency modulator, which can be used as transmitters in panoramic measuring GDGs.

The purpose of the invention is to increase the resolution and increase the speed of the device.

Fig. 1 shows a structural electrical circuit of a meter of the state assembly orders of oscillating frequency generators; figure 2 - structural diagram of the GCH; FIG. 3 is a receiver block diagram. A device for measuring the group lag time of the oscillating frequency generators contains the oscillating oscillator 1, the first 2 and second 3 attenuators, the first 4 and second L frequency converters, the local oscillator 6, the first 7 and the second 8 frequency demodulators, the subtractor 9 and the receiver 10 .

The first measuring output of the studied GKCH 1 via the first attenuator 2 connected in series, the first 4 frequency converter and the first frequency demodulator 7 is connected to the input of the subtraction unit 9, the other input of which is connected through the second attenuator 3, the second frequency converter 5 and the second frequency converter the demodulator 8 is connected to the second measuring output of the studied GCF I, and the output of the subtraction unit 9 is connected to the measuring input of the receiver iO, the output of the modulating frequency signal of which is connected to the input of the studied GKCH I. The control output of the GKCH 1 is connected to the combined inputs of the receiver 10 and the local oscillator 6, and the output of the local oscillator 6 is connected to the heterodyne inputs of the converters 4 and 5.

The investigated GKCH (Fig.2) consists of a series-connected frequency tuning unit 11, a tunable generator 12 and a frequency modulator 13, the output of which is the first measuring output, and the input is the input of the modulating frequency signal of the studied GKCH 1, the output of the frequency tuning unit 1I is control output, and the output is

generator 12 - the second measuring output of the GKC 1.

The receiver 10 (FIG. 3) contains a modulating frequency generator 14 connected in series, a phase detector 15 and a panoramic indicator 16, the output of the generator 14 being the output of the modulating frequency of the receiver 10, the input of the phase detector 15 to the measuring input, and the input of the indicator 16 controlling the input of the receiver Y.

The device works as follows.

The signal from the output of the receiver 10

) (at + h)

(one)

enters the modulating input of the studied GCCH 1. At the first measuring output of the GKC I there is a FM signal

Chy

 t + pcos 51t + M o-

4 ,, (2., aJ,) + Xr (-Jc (t))}. Where

(2)

H (,, uJ) GCH with

Lee) Sl

phase shift of the frequency L, introduced by the HKCH at the frequency uJ; amplitude of the FM signal;

- frequency modulation index. The signal at the second measuring output of the studied GCB is unmodulated and is expressed by

and

1H

(t) and (t) + 4, uJ (t)),

(3)

where (. (t)) are the phase noise of the carrier frequency uJ of the tunable generator 12, which is included in the studied GCF 1.

The signal I, through the decoupling attenuator 2, which serves to match the microwave output of the hopper 1 to the converter 4 input, arrives at the measurement input of the frequency converter 4, the heterodyne input of which receives the variable frequency signal uJ from the output of the local oscillator 6:

U (t)

and

Rm

 t + (t), (4)

where H (t) is the heterodyne voltage phase noise.

At the output of the converter 4 frequencies, select the signal differential or total frequency, we obtain:

) K, (H ± 4) t +

+ + H () J +

+, „(D ,,) -N, (H) + fcn (H) +

.H) +% m (HH) ± g (C), (5)

where than (d is the phase shift introduced by the frequency converter 4 to the heterodyne signal of the frequency uJrj × (uJ) phase shift introduced by the converter 4 of the frequency at the carrier frequency a) of the GKCH 1;

W (uJ.) - phase shift introduced by the m-ntf ..- n

we control frequency converter 4 frequency at an intermediate frequency (uJ uJ ± C-); vf () phase shift introduced by frequency converter 4 at the envelope frequency of the modulated measurement signal; K - transfer coefficient

Converter 4 part-you.

The frequencies of the GCCH I and LO signals 6 are tuned so that throughout the entire tuning range of j, the exact frequency uJ remains constant uJ c. const. Phase shifts if ,, (And, 04), vf. (a, u; j, (uJ), H (u |) are temporary functions, the law of change of which is generally unknown in the general case. Simultaneously from the second measuring signal of the GKCH 1, the unmodulated sweep signal U (t) through decoupling attenuator 3 is supplied to the measured 45 input of the second frequency converter 5 (identical to converter 4), the heterodyne input of which receives the local oscillator 6 signal. The output of the second converter 50 of the frequency generator 5 extracts the signal of the total or difference frequency

 five

and (t) K „, and; sin (cJ, ± cJ,) t +, 55 H, K (t)) +, (- Jr (t)) +4, M, (t)) + /

 H, "(HH)).

The signals and (t) and U (t) are fed to

J

the inputs of frequency demodulators 7 and 8, and at their outputs the variable components will be proportional to the derivative of the instantaneous phases of the signals U (t) and UjCt). The signal at the output of the demodulator 7

) K ,,

dMV ,, ((tU + (Sl, .J, (t), / dtdt -

X t (,)) +4, ()) +

 5 + K U-cm

(7)

  d +

+ d ilMit))), (tb dt dt dt J

The second term of expression (7) represents the sum of the components of the phase noise in the spectrum of which there are harmonic components of the O. modulating frequency. During phase detection of the signal (7) in the receiver 10, there is a Vits error in determining the measured GDT value of the oscillating frequency generator under study.

To compensate for the second term of expression (7), the second frequency converter 5 produces a signal U (t), the variable of which after the demodulator 8 takes the form

and (t) K K s) 1

Ug Vl- 1Ч „d U L dt

+) dV, JaJ, it)) d "CiiiIt)) dt dtdt

   , (tb. dt - dt (8)

By applying the signals U, (t) and Ug (t) to the inputs of the subtraction unit 9, with the condition U U, „, we obtain at its output a signal that is free from the constituent phase noise:

u, (t) to k to ", and, +

h- (,, M),. (, J

dt

. sin nt + H ,,, (“y, (t)) + (Sl.M) + 4-,

(9)

where K is the transfer coefficient of subtraction unit 9. From the expression (9) it follows that the information on the non-uniformity of the GDT MQP is contained both in amplitude and in the phase of the signal Ug (t). However, extraction of useful information (a, tJL) (t)) / dt from the amplitude of the signal Uj (t) is almost impossible, since the oscillation of the amplitude of the GCB leads to large errors. Thus, useful information H (a; a)) can be obtained only by phase detection of the signal Uj (t). (phase detector, insensitive to changes in amplitude). The signal and (t) from the output of the subtraction unit 9 is fed to the measuring input of the receiver 10, the indicator of which shows

12559876

The increase in resolution is achieved by introducing a second channel, which serves to form a signal proportional to the phase noise of the measuring channel, which with the help of the subtraction unit makes it possible to compensate for the irregularities of the GDZ arising from the phase noise in the measuring channel and the local oscillator.

ten

Increasing the speed of the proposed device is obtained by eliminating the PLL system.

Claims (1)

15 Claims. A device for measuring the group lag time of oscillating frequency oscillators, comprising The total frequency response of the receiver is consistent, the series of the GDT is consistent with the non-uniformity of the TLD of the frequency converter: c.K,. () , (ten)  GCH where SL 2 P F is the circular modulating frequency;  cm (, 4) 2SI frequency response of the delay group converter 4 frequency. In most practical cases, only the uniformity of the group delay is of interest. In this case, the measured non-uniformity of the GD L1 (uJ) GKCH with + Uu to-).. (P) From the expression (11) it follows that the resolution is a measurement demodulator and a subtractor. irregularities of the group terms L –rkm (H is determined only by the magnitude of the own non-uniformities rB34t (jrt (o.).) of the frequency converter of the measuring channel. The positive effect is in increasing the measurement resolution of the nonuniformity of the HBZ of the oscillating frequency generators and an increase in the meter performance, which will reduce the dynamic measurement error.  the third output terminal of the oscillating frequency oscillator under study is connected to the first input of the second transducer via the second attenuator 45 frequency spreading system, heterodyne the input of which is connected to the output of the g of a tertiary, and the outputs of the first and second frequency converters through the corresponding frequency demodulators 5Q is connected to the inputs of the subtraction unit, the output of which is connected to the measuring unit during the course of the receiver. Increasing the speed of the proposed device is obtained by eliminating the PLL system. Claims. A device for measuring the group lag time of oscillating frequency oscillators, comprising attenuator and frequency converter, as well as the local oscillator and frequency demodulator, the receiver's modulating frequency signal output is connected to the first input terminal for connecting the swept frequency generator under investigation, the first output terminal for connecting which is connected to the attenuator input, and the second one - with the combined control inputs of the receiver and the local oscillator, the output of which is connected to the heterodyne input of a frequency converter, characterized by that, in order to improve resolution with a simultaneous increase in speed, a second attenuator, a second frequency converter, a second frequency and a third output terminal of the swept-frequency generator under study are connected to the first input of the second frequency converter, the heterodyne one the input of which is connected to the output of the local oscillator, and the outputs of the first and second frequency converters through the corresponding frequency demodulators connected to the inputs of the subtraction unit, the output of which is connected to the measuring unit in the course of the receiver. / f Editor N. Dankulich Compiled by M. Katanov Tehred I.Popovich Proofreader O.Lugov Order 4821/46 Circulation 398 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 13 V FIG. 2 Fig.Z