RU2003989C1 - Oscillographic phase meter - Google Patents

Abstract

The phasometer relates to radio measurement technology and can be used to visually evaluate the carrier frequency and type of modulation of the received signal, as well as to determine the radiation source of complex signals with linear frequency modulation. SUMMARY OF THE INVENTION A phase meter comprises a sweep generator, two local oscillators, two mixers, a first intermediate frequency amplifier, a drive, a delay line, four CRTs, a sawtooth voltage generator, a key, a second intermediate frequency amplifier, three multipliers by two, four and eight, three frequency dividers by two four and eight, four amplitude detectors, two antennas, a switch, a narrow-band filter, a counting pulse generator, an And element, a differentiating circuit, a counter, a multiplier, a low-frequency amplifier, an electric but-counting frequency, the arithmetic unit 7 and the indicator yl

Description

The phasometer relates to radio measurement technology and can be used to visually evaluate the carrier frequency and the type of modulation of the received signal.

An orcillographic phasometer is known which provides a visual assessment of the carrier frequency and the type of modulation of the received signal, but does not allow finding the source of its radiation (ed. St. USSR No. 1539676, class G 01 R 25 / 00.1988).

There are phase and amplitude methods for measuring angular coordinates (direction finding). In the phase method, the difference in the times of reception of signals by two spaced antennas is fixed as the phase difference of these signals (Fig. 7):

Ay 2rr -COSj6,

where d is the distance between the antennas (measuring base);

A is the wavelength;

/ 3-angle of arrival of the radio wave.

The phase direction finding method has a contradiction between the requirements of measurement accuracy and the uniqueness of the angle reading. Indeed, according to the above formula, the phase system is the more sensitive to the angle change, the larger the relative size of the base d / A, however, with increasing dA, the phase difference exceeds 2tg, i.e. ambiguity of counting occurs. The ambiguity of direction finding by the phase method can be eliminated in two 1 ways; the use of highly directional antennas and the use of several measuring bases (multiscale).

Direction finding systems with highly directional antennas have a long range and high resolution in direction. However, they do require a search for the radiation source prior to the measurement and its automatic tracking in the direction of the antenna beam during the measurement.

Multi-scalability is achieved using multiple measurement bases. Moreover, a smaller base forms a rough but unambiguous reference scale, and a larger accurate, but ambiguous reference scale. The use of a multiscale method for resolving the ambiguity of direction finding using spaced omnidirectional antennas does not require a preliminary search for the radiation source. However, systems using this method have a limited range and complex technical implementation.

The proposed phasometer uses a modified phase method for direction finding of a radiation source of complex signals with linear frequency modulation (LFM), based on multiplying LFM signals received by two spaced antennas, extracting the beat voltage, measuring the beat frequency f6 and the rate of change of the frequency of the whisker inside the pulse. the value of which determines the angle of arrival of the radio wave

With fe

/ arccos

5

0

5 0 5

0 5

0.

5

where c is the speed of propagation of light.

The aim of the invention is to expand the functionality by accurate and unambiguous direction finding of the source, emitting complex signals with chirp.

The goal is achieved by introducing into the phase meter the first and second antennas, a switch, a narrow-band filter, a fourth amplitude detector, a counting pulse generator, an I element, a differentiating circuit, a meter, a multiplier, a low-frequency amplifier, an electron-counting frequency meter, an arithmetic unit and an indicator, moreover, the first antenna is connected to the first input of the first mixer and through the switch to a series-connected narrow-band filter, the fourth amplitude detector, element And, the second input of which is connected to the output of the counter pulse generator, a counter, the second input of which is connected through the differentiating circuit to the output of the fourth amplitude detector, an arithmetic unit and an indicator, and a multiplier is connected in series to the second antenna, the second input of which is connected to the first antenna via a switch, a low-frequency amplifier, and an electron-counting frequency meter whose output is connected to the second input of the arithmetic unit.

Structural diagram of the proposed phase meter is presented in figure 1; a possible view of the waveforms on the screens of a CRT is shown in FIG. 2; the arrangement of the symbolic frequencies of the signals with multiple frequency manipulation is shown in Fig. 3; a phase diagram of a frequency-manipulated signal is shown in FIG. 4; frequency and timing diagrams illustrating the operation of the phase meter are shown in Figs. 5 and 6; the principle of direction finding of the radiation source of the LFM signals by the phase method in the same plane is illustrated in Fig. 7

The oscillographic phase meter contains a sweep generator 1, a first local oscillator 2, a first mixer 3, an amplifier 4 of a first intermediate frequency, a drive 5, a delay line b, a first CRT 7, a ramp generator 8, a key 9, a second oscillator 10, and a second mixer 11, amplifier 12 of the second intermediate frequency, the first 13.1, second 13.2 and third 13.3 frequency multipliers by two, four and 10 seven, the first 14. By the second 14.2 and third 14.3 frequency dividers by two, four and eight, the first 15.1, second 15.2 and third 15.3 amplitude detectors, second 16.1, third 16.2 and four Werth 16.3 CRT, the first 17 and second 18 antenna 15, a switch 19, narrow. band-pass filter 20, fourth amplitude detector 21, counting pulse generator 22, element 23, differentiating circuit 24. counter 25, multiply 26, 20 low-frequency amplifier 27, electron-counting frequency counter 28, arithmetic unit 29 and indicator 30. Go to the first the output of the sweep generator 1 is connected in series to a local oscillator 2, a mixer 3, the second input of which is connected to the antenna 17, an amplifier 4 of the first intermediate frequency, a drive 5, the second input of which is connected to its output through the delay line 6, and a vertical CRT electrode 7, burn ontal- ny electrode 30 which is connected to the second output of the sweep generator 1. A sawtooth voltage generator 8, the second input of which is connected to the output of the delay line 35 6, a local oscillator 10, a mixer 11, the second input of which is connected via the key 9 to the output of the amplifier 4 of the first intermediate frequency and the input of the drive 5, is connected in series to the output of drive 5, an amplifier 12 of the second intermediate frequency and 40 ri of the signal processing channel, each of which consists of a series-connected frequency multiplier 13.1 (13.2. 13.3), a frequency amplifier 14.1 (14.2,14.3), an amplitude detector 15.1 (15.2, 15.3) and a vertical 45 Electrode CRT 16.1 (16,2, 16.3), the horizontal electrode of which is connected to the output of the sawtooth voltage generator 8. In the first signal processing channel, the second intermediate frequency is multiplied and divides 50 s by two, in the second by four and in the third by eight. A switch 19, a narrow-band filter 20, an amplitude detector 21, an I element 23, the second input of which is 55 connected to the output of the counting pulse generator 22, a counter 25, the second input of which through a differentiating circuit 24 is connected to the output of the amplitude detector 1, are connected in series with the antenna 17 , arithmetic unit 29 and indicator 30.

A multiplier 26 is serially connected to the antenna 18, the second input of which is connected via the switch 19 to the antenna 17, a low-frequency amplifier 27 and an electronically counted frequency meter 28, the output of which is connected to the second input of the arithmetic unit 29.

The principle of operation of the phase meter is based on a search in a given frequency range of the signal Df and a visual assessment of the type of modulation and its main parameters, as well as direction finding of its radiation source.

The phasometer works as follows.

The specified frequency range Df is viewed with the help of a sweep generator 1, which periodically, according to a sawtooth law, tunes the frequency of the local oscillator 2. At the same time, the sweep generator generates a horizontal scan of the CRT 7, which is used as the frequency axis, and its length corresponds to the frequency span.

If a binary phase shift signal (FMn-2) is fed to the input of the phase meter, then it can be analytically written as follows:

Uc (t) Vc cos 2l fct + pk (g) + 0 t Tc,

where Vc, fc, pc and Tc are the amplitude, carrier frequency, initial phase and signal duration, respectively;

pk ($ 0, K is the manipulated component of the phase that displays the law of phase manipulation, and y (t) const at Kgi t (K + 1) Ti and can change abruptly at t K Hz, i.e., at the boundaries between elementary premises (K 1,2N-1);

7i and N are the duration and number of chips that make up a signal of duration Tc (Tc N Ti).

The specified signal from the antenna 17 is fed to the first input of the mixer 3, to the second input of which the voltage of the local oscillator 2

Url (t) Vr1 COS (2ttfrit +

+ jryri xi2 + pm); about t tp,

where Vri, frl, RG and Tn are the amplitude, initial frequency, initial phase and the repetition period of the local oscillator voltage;

yi - speed - frequency changes

 P

local oscillator.

At the output of the mixer 3, voltages of combination frequencies are generated. 5 The voltage of the first intermediate frequency is extracted by amplifier 4.

Unpi (t) - Vnpi cos 2tg1pr1 + pk (t) - -moon2 #iPi; Q: StSTc, 1

where Vnpi- ЈKtVC Vri;

Ki is the transfer coefficient of the mixer; fnp e fc - f g - first intermediate frequency; i.

Pnp1 PC - pM,

which, after accumulating and exceeding the threshold level, the Stop in the drive 5 acts on the control input of the sweep generator 1, puts it into a stop mode, on the control input of the key 9, opening it, on the first input of the generator 8, turning it on, and on the vertical CRT electrode 7, the horizontal electrode of which is connected to the second output of the sweep generator 1. Key 9 in the initial state is closed. From this point in time, the signal search process is stopped for the duration of the visual analysis, which is determined by the delay time Ts of the delay line 6. The accumulation time and the threshold level Vnop in the drive 5 are selected so that this level does not exceed random interference. In this case, a pulse (frequency mark) is generated on the CRT screen 7, the position of which on the horizontal scan uniquely determines the carrier frequency fc of the received FMN-2 Sipal.

To visually assess the type of modulation (manipulation) of the received signal, a second frequency conversion of the received signal and three signal processing channels of the second intermediate frequency are used.

When the tuning of the local oscillator 2 ceases, the voltage is released by the amplifier 4 of the first intermediate frequency

UnplW - Vnp1 COS (2L fnplt +

 + yJnpi,

which through the public key 9 enters the first input of the mixer 11, on the second

the input of which the voltage of the local oscillator 10 is applied

Ur2 (t) - Vr2 COS (2L f r2t + +

+ pa) 0 t 5 ra,

where Vr2, fg2 and fti are the amplitude, initial frequency and initial phase of the local oscillator voltage;

Y2 - - rate of change of frequency

local oscillator 10;

DGD2 frequency deviation.

At the output of the mixer 11, combinational frequency voltages are generated. Amplifier 12 isolates the voltage of the second intermediate frequency

Unp2 (t) - Vnp2-COS 2ttfnp2t +

+ yv (t) - + 0 t Tc,

where VnP2 TT Ki Vnpi Vrg;

fnp2 m fnpi - fr2 second, intermediate frequency;

# pr2 tp1 - # V2,

which goes to the inputs of the three signal processing channels. At the outputs of the frequency multipliers by two 13.1, four 13.2 and eight 13.3 the corresponding oscillations are formed:

Ul (t) Vnp2 COS (4tffnp2t -2l ang. + 2 rpr2);

U2 (t) - Vnp2 COS (8LH fnp2t - -Al yjt2 + 4 pnp2);

Us (t) Vnp2 Cos (16l: fnp2t -8 l-tfjt2 + 8); 0 t Tc,

in which phase manipulation is already absent.

The spectral width of the second Af2, fourth & 4 and eighth -Afe harmonics is determined by the duration Tc of the signal (Afz Af4 Afe m

), while the width of the spectrum Afc FMN C

2-signal is determined by the duration

“Of his elementary premises (Afc -).

y

Therefore, when the second intermediate frequency is multiplied by two, four, and eight, the spectrum of the QPSK-2 signal is collapsed N times (-d ± - - N) and trans-

formed into single spectral components, which after dividing in frequency dividers by two 14.1, four 14.2 and eight 14.3 and detection in amplitude detectors 15.1, 5.2 and 15.3 are viewed on CRT screens 16.1, 16.2 and 16.3 (Fig. 2a ) This circumstance is a sign of the arrival of an FMN-2 signal at the input of the phase meter, for which the phase shift margin is m 2 and the magnitude of the phase jumps.

The delay time e of the delay line b is selected so that it is possible to visually evaluate the main parameters of the received PSK-2 signal by observing the oscillograms on screens 7, 16.1, 16.2 and 16.3. After this time, the voltage from the output of the delay line 6 is supplied to the second input of the sawtooth voltage generator 8, turning it off, and to the reset input of the drive 5, resetting its contents to the initial (zero) state. In this case, the sweep generator 1 is put into search mode, and the key 9 is closed, i.e. is returned to its original state. From this moment in time, viewing the specified frequency range D1 and searching for signals continues. In case of detection (of the next QPSK-2 signal, the operation of the phasemeter proceeds similarly.

Therefore, the generator 8 generates a sawtooth voltage, the duration of which is determined by the delay time T3 of the delay line 6. The indicated voltage is necessary for the spectral decomposition of the received signal.

If the phasemeter input

TT T

FMN-4-signal (t) 0, -rj-n, -nft, then on

i Ј

the output of the frequency multiplier 13.1 by two produces an FMN-2 signal (t) 0, lg, 2tg, Zl, the spectrum of which is observed on the CRT screen 16.1 (Fig.2b), and the outputs of the frequency multiplier 13.2 are four and the frequency multiplier 13.3 by eight, the corresponding harmonic oscillations U2 (t) HU3 (t) are formed, which are observed on CRT screens 113.2 and 16.3. The parameters of the received FMN-4 signal are evaluated in a similar way.

If the input of the phasemeter receives FMN-

l p 3 5 3 1 8-signal pk (} 0,, Tj, tЈL, -cl:

then at the outputs of the frequency multipliers two 13.1 and four 13.2 FMN-4 are formed

PSK-2 signals whose spectra are observed on CRT screens 16.1 and 16.2, respectively, and at the output of the frequency multiplier 13.3 by eight, a harmonic oscillation from (t) is generated, the spectral component of which is observed on the CRT screen 16.3 (Fig. 2c). The multiplicity of phase manipulation m in this case is equal to 8 (m «8), and the quantity

phase jumps.

If the input of the phase meter receives the ChMn-2 signal (Fig. 3a)

Uc (t) Vc cos 2 fcpt + $ t) + pc 0 t TC,

where fcp f i

fi + fe

- average signal frequency;

fcp - h fcp + symbol3jr, frequencies;

y (t) is the time-varying phase function (Fig. 4);

then at the outputs of the frequency multipliers by two 13.1, by four 13.2 and by eight 13.3 its spectrum is transformed into two spectral components with indices D 1,2,4, respectively (Fig. 2d).

By the mutual arrangement of the spectral components, knowing the average frequency of the received FMN-2 signal (it is visually evaluated on the CRT 7 screen), we can visually evaluate the frequencies fi, f2 and the duration of the elementary transmissions (symbol intervals).

If an FMN-3 signal is input to the phase meter (Fig. 3b), then at the output of the frequency multipliers four 13.2 and eight 13.3 its spectrum is transformed into three spectral components. These spectral components are observed on CRT screens 16.2 and 16.3. On the CRT screen 16.1, the spectrum of the FSK-3 signal is observed (Fig. 2e).

If the FMN-5 signal is input to the phase meter (Fig. 3Sv), then five spectral components are formed at the output of the frequency multiplier 13.3 by eight. These spectral components are visually evaluated on a CRT screen 16.3. On the CRT screens 16.1 and 16.2, the spectra of the received FSK-5 signal are visually observed (Fig. 2e).

If a phasing signal is input to the phase meter

Uc (t) Vc cos (2tfTfct + l yct2 +

nrs); OrSt Ј Tc,

where Vc, 1c, pc and Tc are the amplitude, initial frequency, initial phase and signal duration, respectively;

Afa

The rate of change is often increased - I s

you are inside the impulse;

 - frequency deviation, then the voltage is generated at the output of the intermediate frequency amplifier 12

Unp2 (t) - Vnp2 COS 2 L fap2t +

(

+ Usg2-7gu2g2 + pnpu15

This voltage is applied to the inputs of the signal processing channels ex. At the same time, at the output of multipliers 13.1, 13.2 and 13.3 astots by two, four and eight, the following LFM signals are formed:

Ui (t) - Vnp2 cos (43rfnp2t + In yct - -4 yxP + 2 phP2); U2 (t) - Vnp2 cos (8 jrfpp2t yct -, -4 ttyat2 + 4 pnpg);

(J3 (t) - Vnp2 cos (167Tfnp2t + 8 jryct - -8 + 8 pnpz); 0 gt STC.

Since the duration Tt of the LFM signal 35 at the fundamental, second, fourth, and eighth harmonics of the second intermediate frequency is the same, an increase in the mustache by a factor of 2, 4, and 8 occurs due to an increase in the frequency deviation of Afg by a factor of 2.4 and 8. It follows that the spectral width of the LFM signals at the second, fourth, and eighth harmonics is 2, 4, and 8 times greater than its fundamental-harmonic spectrum width of the second intermediate frequency Afc (Af2 - 2A fe; Af4 - 4A fc; Afв - 8 Afc) . Consequently, on the CRT screens 16.1, 16.2 and 16.3, spectra of LFM signals are visually observed, the width of which is the same (Fig. 2g). This circumstance is a sign of the recognition of the chirp signal and leads to translation by the operator. switch 19 to the closed position. In this case, the received LFM signal Uc (t) from the antenna 17 through the closed switch 19 is fed to the first input of the multiplier 26, the second input of which is supplied from the antenna 18 with the LFM signal

Uc (t + t) Vc cos 2l fc (t + t) +

40

45

55

2 °

orj

oi

+ lus (t + t) 2 + 0 t Tc, where G DK lag timeww

not from the signal arriving at the antenna 18 with respect to the signal arriving at the antenna 17.

As a result of multiplication, the resulting voltage

U 2ft) - Uc (t) Uc (t + t) - V6 cos (2l fet +

+ b) + Ve cos (Al fct + 2l f6t + p + + 2gustg + 2).

rfleVe- | K2-Vc2;

Kg - gear ratio multiply i

Fe US t - the beat frequency;

(pa 2lfcr + l: ycg2 is the initial phase of the beats.

The amplifier 27 low frequency is allocated voltage beats (voltage differential frequency)

Ue (t) Ve cos (2ttf6t + pb); 0 t Tc.

The angle of arrival of the radio wave is determined as follows:

/ arccosЈ- |.

Since when the angle / changes, the magnitude of the beat frequency fe is also imputed. then the latter uniquely identifies the bearing to the radiation source of the LFM signals (Fig. Ba). To determine the angle of arrival / radio wave, it is necessary to measure the beat frequency fe and the rate of change of the frequency of the whisker inside the pulse. The beat frequency fe (Fig. 56) is measured using an electronically counted frequency meter 28. Short pulses are generated from the continuous alternating voltage Ub (t), the repetition rate of which remains equal to fe. If we count the number of pulses w for a known time interval At, then we can easily determine the desired frequency fe -.

In particular, if At 1s, then the measured number of pulses m is numerical, equal to the unknown frequency fe. The counted number of pulses u from the output of the electronically counted frequency meter 28 is supplied to the first input of the arithmetic unit 29.

To measure the rate of change of the frequency of the whisker inside the pulse, the voltage Uc (t) from the antenna 17 through the closed switch 19 is fed to the input of the narrow-band filter 20 with a passband Af (Fig. B). At the output of the narrow-band filter 20, a radio pulse is generated for a long time Af, strictly Ti-u (Fig. Bb). This radio pulse

arrives at the input of the amplitude detector 21, which distinguishes its envelope. A rectangular video pulse from the output of the amplitude detector 21 (Fig. Bb) is supplied to the first input of the element And 23, to the second input of which counting pulses are fed from the output of the generator 22 (Fig. Bg). At the output of element And 23, counting pulses are formed, the number of P2 of which is counted by the counter 25. The video pulse from the output of the amplitude detector 21 (Fig. Bb) simultaneously enters the input of the differentiating circuit 24, at the output of which two short different-polarity pulses are generated (Fig. B). Moreover, the counter 25 is returned to the initial (zero) state by a positive short pulse, i.e. getting ready for work; and with a negative short pulse, the counted number of counting pulses is transferred to the arithmetic unit 29, in which the angle of arrival ft of the radio wave in the digital code is determined. The latter is recorded by indicator 30.

Thus, the proposed phasometer in comparison with the prototype provides accurate and unambiguous direction finding of the radiation source of the LFM signals. This is achieved by receiving the LFM signals at two spaced antennas, multiplying them with each other, isolating the beat voltage, measuring the beat frequency fe and the rate of change of the frequency of the whisker inside the pulse, the value of which accurately and unambiguously determines the bearing to the radiation source of the LF signals, moreover, the presentation of direction finding results in digital code provides for their long-term storage, long-distance transmission over communication channels and interfacing with computer technology. Thus, the functionality of the phase meter is expanded.

(56) Belovsky P.S. and other fundamentals of radio navigation. M .: Transport, 1982, p. 126-128.

USSR copyright certificate No. 1539676, cl. G 01 R 25/00, 1990.

Claims (1)

The claims OSCILLOGRAPHIC PHASOMETER containing a local oscillator, a mixer, the second input of which is the analyzer input, an intermediate frequency amplifier and a drive, the second input of which is connected to the output of the delay line, and the output is connected to the input of the scan generator, to the input of the delay line, to the vertical electrode of the electronic beam tube and to the second input of the key, the first input of which is connected to the output of the intermediate frequency amplifier, a horizontal electron beam electrode is connected to the output of the generator and a sweep, which also contains a servo-shaped voltage generator, the second input of which is connected to the output of the delay line, the second local oscillator, the second mixer, the second input of which is connected to the key output, an amplifier of the second intermediate frequency and three signal processing channels, also connected in series to the output; each of which contains a cathode ray tube and series-connected frequency multiplier, frequency divider, amplitude detector connected to a vertical electrode of the corresponding cathode ray tube, the horizontal electrodes of which are connected to the output of the sawtooth voltage generator 5, characterized in that, in order to expand the scope due to the possibility of direction finding of the source, the radiation of complex signals with a linear frequency modulation is introduced into it first and second antennas, switch, narrow-band filter, fourth amplitude detector, counting pulse generator, AND element, differentiating circuit, counter, multiplier, low-frequency amplifier, electric a counting frequency counter, an arithmetic unit and an indicator, the first antenna being connected to the first input of the first mixer and through the switch to a series-connected narrow-band filter, the fourth amplitude detector, element I, the second input of which is connected to the output of the counter-pulse generator, a counter, the second input of which through a differentiating circuit it is connected to the output of a fourth amplitude detector, an arithmetic unit and an indicator, the second multiplier is connected in series to the second antenna 5 ABOUT 5 swarm input of which through the switch the totomer, the output of which is connected to the second, is connected to the first § antenna, the amplifier is equipped with an input of an arithmetic unit, low frequency and electronic counting hours t 2 . W K (fl and G "- -: f  and 1 ± Jl-1 , i 3Ј and t L and I jt jc j  f, fa 5- .isZ FMN-2 FMN-H FMch-Z AND CHMN-5LUM Fis2 j -And ChMn-2 ± J Pw 2003989 I t € 4T LD LIIt t hi g llllllHIIIHmillllimmillllllinmnu , illl € 1 f -U V8 Fisb Editor T. Yurchikova iFig 7 Compiled by V. Dikarev Tehred M. Morgenthal Corrector O. Kravtsova Gf I - Fis5 V8