SU1744472A2 - Indicator unit - Google Patents

Abstract

The invention relates to indicator and recording devices and can be used for visual analysis and recording of parameters of complex signals with combined linear frequency modulation and multiple phase shift manipulation. The aim of the invention is to increase the reliability of visual assessment of parameters by suppressing spurious signals through specular and combination channels. Indicator device

Description

The invention relates to indicating and registering devices and can be used for visual analysis and recording of parameters of complex signals with combined linear frequency modulation and multiple phase shift manipulation (LFM), and is an improvement of the device according to auth st. No. 1682788.

The known indicator device provides a search in a given frequency range Df LFM - MFMn signals and a visual assessment of their main parameters on the screen of three CRTs.

The disadvantage of this device is the presence of additional reception channels. This is explained by the fact. that the same intermediate frequency fnp can be obtained by receiving signals at two frequencies fc and f3, i.e. fnp fg - fc and

fnp fa fr.

Therefore, if the tuning frequency fc is taken as the main reception channel, then along with it there will be a mirror reception channel, the frequency f3 of which differs from the frequency fc by 2fnp and is located symmetrically (mirror) with respect to the frequency of the local oscillator fr. The conversion in the image receive channel occurs with the same QPR conversion coefficient as in the main channel. Therefore, it has the most significant effect on the selectivity and noise immunity of the device.

In addition to the mirror, there are other additional (combinational) reception channels, the frequency of which is determined from the following equality.

fl - m f + - 1 f tkl n r n n (J

where m. n - integers

The most harmful combinational channels of reception are the channels formed by the interaction of the carrier frequency of the received signal with the second

harmonic frequency of the local oscillator, since the sensitivity of these channels is close to the sensitivity of the main reception channel. So, two combinational channels of reception correspond to frequencies (Fig. 3)

fKi 2fr fnp, fK2 2f, - fnp.

where 2fr is the second harmonic of the local oscillator frequency.

The presence of spurious signals (interference), received by the mirror and combinational channels, reduces the noise immunity and reliability of the visual evaluation of the parameters of the received signal with combined linear frequency modulation and multiple phase shift manipulation.

The aim of the invention is to increase the reliability of the visual estimation of parameters by suppressing spurious signals in the specular and Raman channels.

The goal is achieved by introducing a third frequency detector, a third differentiating circuit, a uni-polarity gate and a coincidence element, a second multiplier, a sixth band filter, a first amplitude detector, a drive and a threshold block, a second amplitude detector , the output connected to another input element of the match, the third and fourth keys, through which the output of the intermediate frequency amplifier is sequentially connected to the information input om a detector, and the other inputs

the third and fourth keys are connected respectively to the outputs of the match element and the threshold block. One input of the second multiplier is connected to the output of the broadband amplifier, another input of the drive is connected to the reset input of the detector, and the output of the intermediate frequency amplifier is connected to another input of the second multiplier and inputs of the third frequency detector and the second amplitude detector.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 - detector circuitry; in fig. 3 is a frequency diagram explaining the process of forming additional reception channels; in fig. 4 - view of possible oscillograms; in fig. - timing diagrams explaining the operation of the device.

The indicator device contains a sweep generator 1, the first CRT 2. receiving antenna 3, broadband amplifier 4, first frequency detector 5, first differentiating circuit 6. second differentiating circuit 7, mixer 8, intermediate frequency amplifier 9, first key 10, first frequency multiplier 11 by eight, the first band-pass filter 12, the first frequency divider 13 by eight, the second band-pass filter 14. the first multiplier 15, the third band-pass filter 16. the second frequency multiplier 17 by eight, the fourth band-pass filter 18, the second frequency divider 19 E eight, fifth band-pass filter 20, phase detector 21, low-pass filter 22, control signal generator 23, controllable delay element 24, detector 25, delay element 26, second switch 27, search block 28, local oscillator 29, second frequency detector 30. phase shifter 31 at 90 °, reference voltage generator 32, second and third CRT 33 and 34, second amplitude detector 35. third frequency detector 36, third differentiating circuit 37, unipolar gate 38. coincidence element 39, third key 40 the second multiplier 41 of the sixth band-pass filter 42, per amplitude detector 43, accumulator 44. threshold unit 45, fourth switch 46. Broadband amplifier 4 is connected to the output of receiving antenna 3. Mixer 8, the second input of which is connected via a local oscillator 29 to the first output of search block 28, intermediate frequency amplifier 9 key 10, the second input of which is connected to the output of the detector 25, frequency multiplier 11 by eight band-pass filter 12, frequency divider 13 by eight, band-pass filter 14, frequency detector 5. differentiating circuit 6, differentiating circuit 7, oscillator 1 sweep horizontally deflecting the CRT 2 plates, vertically deflecting plate which

connected to the output of the differentiating circuit 6.

To the output of the bandpass filter 14 are connected in series an element 24 of a controlled delay, a multiplier 15,

0 the second input of which is connected to the output of the amplifier 9 intermediate frequency, band-pass filter 16, frequency multiplier 17 by eight, band-pass filter 18, frequency divider 19 by eight, band-pass filter 20,

5 a phase detector 21, the second input of which is connected to the output of the generator 32 of the reference voltage, the low-pass filter 22 and the driver 23 of the control signal, the output of which is connected to the second input

0 controllable delay element 24.

A key 27 is connected in series to the output of the bandpass filter 16. A second input of which is connected to an output of detector 25, a frequency detector 30 and modules of a CRT 34, vertically deflecting plates of which are connected to an output of a reference voltage generator 32, and horizontally deflecting plates through a phase shifter by 90 °

0 is connected to the output of the reference voltage generator 32. A frequency detector 36, a differentiating circuit 37, a unipolar ventilator 38, a coincidence element 39, the second input of which is connected via an amplitude detector 35 to the output of the intermediate frequency amplifier 9, key 40, the second input of which is connected to the output Detector 25, the key

0 46, the detector 25, the second input of which through the delay element 26 is connected to its output and the vertical deflection plates of the CRT 33, the horizontal deflection plates of which are connected to the second end of the search block 28.

A multiplier 41 is connected in series to the output of wideband amplifier 4, the second input of which is connected to the output of amplifier 9 of intermediate frequency, band-pass filter 42, amplitude detector 43, accumulator 44, second input of which is connected to output of delay element 26, and threshold unit 45, whose output connected to the second input key 46.

5 The detector 25 is provided with serially connected to its information input 47 by a frequency multiplier 49 by eight, a spectrum width meter 51, a comparison unit 52, the second input of which is connected via the spectrum width meter 50 to the input 47, and a threshold block 53 connected via the reset input 48 to the output of the element 26 delay.

The device works as follows.

The set frequency range D is scanned using search block 28, which periodically, with a period Tn, ramps the LO frequency 29 according to the sawtooth law. At the same time, search block 28 forms a CRT 33 horizontal scan, which is used as a frequency axis and corresponds to the viewing band of a given frequency range. Keys 10, 27, 40, and 46 are always locked in their original state.

The received signal with combined linear frequency modulation and multiple phase shift keying (chirp-MFMn) can be analytically recorded as follows:

Uc (t) Uc cos 2jrfct - l yi-2 + (/} (t) + pc I 0 t g „,

where is DC, fc. p с, тп - amplitude, initial carrier frequency, initial phase and signal duration;

Afq

y is the rate of change of frequency and

you are inside an impulse:

Dtd - frequency deviation:

 W is the manipulated component of the phase, reflecting the law of phase manipulation in accordance with the modulating code M (m) (Fig. 8a). moreover, (t) const at K ge t (K + 1) te and can be abruptly changed at t К ge. i.e. at the boundaries between elementary premises (K 1. 2N

-one),

ge N - the duration and the number of elementary parcels that make up the signal of duration g, (rw N te)

The specified signal from the output of the receiving antenna 3 through the broadband amplifier 4 is fed to the first input of the mixer 8, to the second input of which is applied the voltage of the local oscillator 29 of the linearly varying frequency Uri (t) Ur cos (2; r frt - lu t24 -u / r) , 0 t Tn

where Ur, fr, p r. Tn is the amplitude, the initial frequency, the initial phase and the period of repetition of the heterodyne voltage:

L y - 4-1 - rate of change of frequency

I p

heterodyne.

At the output of the mixer 8, the voltage of the combination frequencies is generated (Fig. 5a):

fc1 П - fc - У t «fnp + (У - t - У) t: fc2 2fr + у 2t - fc - -) t.

0

five

0

five

0

five

0

five

0

five

where the first index denotes the channel on which the signal is received;

the second index denotes the harmonic number of the local oscillator frequency involved in the frequency conversion of the received signal;

y 2 - rate of change of the second harmonic of the frequency of the local oscillator

(Y2 2 yi).

The tuning frequency fHi and the passband of the intermediate frequency amplifier 9 are selected as follows: fHi fnp, Af 1 2fnp.

The tuning frequency 2 and the passband D f2 of the bandpass filter 42 are selected as follows: fH2 fi + fnp. Af2 fnp.

The amplifier 9 allocates only the intermediate frequency voltage (Fig. 6a).

Unpi (t) Unp fnpt - / 3 | (t) + l () i - y) t2 + p np, 0 t rn

where Vnp is Ki Vc Vr;

Ki is the mixer transfer coefficient;

fnp fg - fc intermediate frequency;

rlr - intermediate initial phase.

This voltage is simultaneously applied to the second input of multipliers 41 and 15, to the inputs of keys 10 and 40, amplitude 35, and frequency 36 detectors. The amplitude detector 35. highlights the signal envelope (Fig. 6c), which is fed to the first input of the coincidence element 39.

From the output of the frequency detector 36, the video signal Uze (Fig. 6d), whose shape corresponds to the law of frequency change fc of the signal (Fig. 66), is fed to the input of the differentiating circuit 37, the output voltage (Fig. 6e) of which is fed to the input of the single-pole valve 38 The specified valve only passes positive impulses. The output pulse of the valve 38 (Fig. B) is fed to the second input of the coincidence element 39. Since the voltages arriving at the two inputs of the coincidence element 39 occupy the same time interval on the time axis, the coincidence element is triggered and opens the key 40 with its output voltage (Fig. 6g).

- At the same time, the voltage Unpi (t) from the output of the intermediate frequency amplifier 9 is fed to the second input of the multiplier 41, to the first input of which the received signal Uc (t) is fed from the output of the wideband amplifier 4. The output of the multiplier 41 produces voltage of combination frequencies. However, in the passband bandwidth

filter 42 falls only on the voltage of the sum frequency (FIG. 5a)

Url (t) Ur1 COS (27Tfrt + Jiy it2

0 t rn

one

Where Vri j- Ka Vc Vnp:

K2 is the multiplier transmission coefficient, which, after detection in amplitude detector 43, enters the input of accumulator 44, where it is integrated and then compared to threshold voltage Unopi in threshold block 45. In this case, threshold threshold Unopi is chosen so that it does not exceed random interference. When the Unopi threshold level is exceeded, a constant voltage is generated in the threshold unit 45, which is applied to the control input of the key 46 and opens it.

In this case, the frequency transformed signal Unpi (t) from the output of amplifier 9 of intermediate frequency through open keys 40 and 46 is fed to the input of detector 25. At the output of frequency multiplier 49, eight detector 25 forms an oscillation

Ui (t) V

etc

 COS 16 JTfnp T + 8 L (yi - y) T2 + 8, in which the phase shift manipulation is already absent.

The width of the spectrum Afs of the eighth harmonic signal is determined by the duration

signal tm (Afe -f -) whereas width

pa Afc of the received signal is determined by the duration te of its elementary parcels (), i.e. the width of the spectrum Afe

the eighth harmonic of the signal is N times less than the width of the Atc spectrum of the input signal Afc

Afe

 N.

Therefore, by multiplying the frequency of the LFM - MFMS signal by eight, its spectrum is folded N times. This circumstance makes it possible to detect a chirp - MFMS signal even when its input power is lower than the noise and interference power.

The spectral width A f of the input signal is measured with a meter 50, the spectral width A fa of the eighth harmonic of the signal is measured with a meter 51. Voltages U and Us, proportional to A f c and A fe, respectively, from the outputs of the meters 50 and 51 of the spectrum width is fed to the two inputs of the comparator block 52. Since U Us, then at the output of the comparator block 52 a positive pulse is generated, which is fed to the input of the threshold block 53, where it is compared with the threshold voltage

five

five

0

five

0

five

0

f-

Q p.

Unop2 The threshold voltage Unop2 is exceeded only when detecting a chirp - IFMN signal. When the threshold level Unop2 is exceeded in the threshold block 53, the voltage is applied to the control input of the search block 28, switching it to the stop mode, to the input of the delay element 26, to the control inputs of the keys 10 and 27, and opening them CRT deflection plates 33. From this point in time, the viewing of the specified frequency range Df and the search for the chirp - MFMS signals is stopped for a time of visual analysis of the main parameters of the detected chirp - FFM signal, which is determined by the delay time T3 of the delay element 26. In this case, a pulse (frequency mark) is formed on the screen of the CRT 33, whose position on the horizontal scan unambiguously determines the initial carrier frequency fc of the detected chirp - IFN signal (Fig. 4a).

When viewing the specified frequency range is stopped (when the search block 28 is stopped), the intermediate frequency amplifier 9 selects the voltage (Fig. 86)

Unp2 (t) Vnp ×

xcos 27rfnp t + lug2 + k (t.).

O t G l,

which through the public key 10 is fed to the input of the multiplier 11 frequency eight. At the output of the frequency multiplier 11 eight is formed voltage U2 (t) Vnp

cos 167rfnp t + 8lug2,

0 t rn,

which is separated by a band-pass filter 12 and fed to the input of a frequency divider 12 by eight. At the output of the latter, a voltage is formed (Fig. 8c) from (t) Vnp v

h cos 2 jrfnp t + jfryt2 4-utpr, O t g

which is a chirp signal at an intermediate frequency and is separated by a band-pass filter 14. This voltage is fed to the input of frequency detector 5, the output of which forms a video pulse (Fig. 8d), the shape of which corresponds to the law of linear frequency modulation. This video pulse from the output of the frequency detector 5 is fed to the input of the differentiating circuit 6. An output pulse (Fig. 8e) is fed to vertically deflecting CRT plates 2 and to the input of the differentiating circuit 7, which forms short polarity pulses (Fig. 8e). In this case, a positive short pulse is triggered and a negative short pulse closes the sweep generator 1. The generated sawtooth voltage (Fig. 8g) enters the horizontally deflecting plates of a CRT 2, on which a pulse appears (Fig. 8e), the duration of which is proportional to the duration of the received signal, the amplitude is proportional to the rate of change of the frequency y inside the pulse, and the area of the oscillogram is proportional to the 10 frequency deviation Dtd (Afg - t) of the received chirp-MFMn signal.

For a visual assessment of the main parameters of the received signal, a frequency-15 time grid is plotted on the CRT 2 screen.

The voltage UaW (Fig. 8c) from the output of the band-pass filter 14 simultaneously arrives at the information input of the element 24 of a controlled delay, the output of which 20 forms a voltage

U4 (t) Ua (t -t) and x

2

a cos 2 fnp (t - r) + „t y (t - r) + c / v ,,,

25

About t rn.

This voltage is applied to the second input of the multiplier 15, the first input of which receives the received Unm2 (t) chmn-MFMN signal (Fig. 86) of intermediate frequency 30 from the output of amplifier 9 of intermediate frequency. At the output of the multiplier 15, a beat voltage is formed (fig. 8h) U6i (t) kb fet + (t) + pb I 0 t gi

1235

where u & k2 unp

fe} g-beat frequency 2 jrfnp t lut2 - initial beat phase; 40

which is the FMK signal at the beat frequency. The beat frequency is determined by the rate of change of the frequency of the signal and the magnitude of the delay g. The voltage Uei (t) is separated by a bandpass filter 16 and 45 is fed to the input of frequency multiplier 17 by eight, the output of which forms a harmonic oscillation Ue2 (t) U6 cos (16 fot + 8 web), 0 t t, The voltage LJ62 (t) is separated by a bandpass filter 18 and 50 is input to a frequency divider 19 at eight, the output of which produces a voltage (Fig. 8i)

U63 (t) U6COS (2; rf6t), Oh ti, 55

which is the harmonic oscillation at the beat frequency. The voltage Ue3 (t) is separated by a bandpass filter 20 and is fed to the first input of the phase detector 21, to the second input of which is fed

the voltage from the output of the generator 32 reference voltage

Do (t) Uo COS (2 L f0 t + p0).

where Uo, fo, po is the amplitude, frequency, and initial phase of the generator voltage.

If the indicated voltages differ from each other in frequency and phase, then a control voltage is formed at the output of the phase detector 21. The amplitude and polarity of this voltage depend on the degree and direction of the beat frequency fe on the frequency f0 of the reference voltage generator 32. The control voltage is extracted by the low-pass filter 22 and, using the control signal generator 23, acts on the control input of the controllable delay element 24 by changing the delay value r so that the equality f b y t f0 is satisfied.

For a visual assessment of the magnitude of the phase jumps and the multiplicity of phase manipulation of the received chirp-mfmn signal, a CRT34 with a circular scan is used. The circular sweep is generated by the reference voltage generator 32, the frequency f0 of which is maintained equal to the beat frequency fr, (f0 fa) by means of a phase locked loop system. The voltage Uei (t) (fig. 8z) from the output of the band-pass filter 16 through the public key 27 is fed to the input of the frequency detector 30, the output of which forms a sequence of short polarized pulses (fig. 8k), the temporal position of which corresponds to moments of abrupt phase change signal (Fig. 8h).

The voltage U0 (t) from the output of the generator 32 of the reference voltage goes directly to the vertically deflecting plates, and through the phase shifter 31 by 90 ° to the horizontally deflecting plates of the CRT 34, forming a circular sweep on its screen.

The formed sequence of short bipolar pulses (Fig. 8k) from the output of the frequency detector 30 is fed to the modulating electrode of the CRT 34 and modulates its electron beam by brightness. On the screen of a CRT 34 form. image in the form of several bright points located on a circle (Fig. 4 b, c, d). The number of points determines the multiplicity m of phase shift manipulation, and the angular distance between them is equal to the magnitude of the phase jumps Dg / received by the chirp – MFMn signal. If the frequency inequality (fgf fo), the velocity labels will move around the circumference with a difference frequency and the accuracy of the visual estimate of the multiplicity m

phase shift keying and magnitude of the phase jumps of the received chirp-MFMn signal decreases sharply. A phase locked loop system is used to eliminate this.

The delay time G3 of the delay element 26 is chosen so that it is possible to visually evaluate the main parameters of the signal received by the chirp-MFMS, the oscillograms are observed on the screen of CRT 2, 33 and 34. After this time has elapsed, the voltage from the output of the delay element 26 goes to the reset inputs of the detector 25 (threshold block 53) and accumulator 44 and resets their contents to zero. In this case, the search block 28 is transferred to the rearrangement mode, and the keys 10 and 27 are closed, i.e. are transferred to their original states. From this point in time, the review of the specified frequency range and the search for the chirp-mfmn signals continues.

In case of detection of the next chirp-MFMn signal, the device operates in the same way.

The indicated operation of the device corresponds to the case of receiving a chirp-MFMn signal on the main channel at the frequency fc (Fig. 3).

If a false signal (interferer) is received in the image channel at the frequency fa (Fig. 56), then in mixer 8 it is converted to the voltage of the following frequencies: f3i f3 + y - fr - Y1 t fnp + (y - yi) t

f32 2fr + y t - f3 - y t. However, only the intermediate (differential) frequency voltage (Fig. 7a)

Unp3 (t) Unp X

for COS 2 JT fnp t (t) -; r (yi -y) 2 0 t rn,

where tnp fs - fr intermediate frequency falls into the passband Afi amplifier 9 intermediate frequency. The frequency fai of a given voltage varies according to the law of a linearly falling square (Fig. 76). The booster Unp3 (t) simultaneously enters the inputs of the amplitude 35 and frequency 36 detectors. The amplitude detector 35 isolates the voltage envelope Kz5 (Fig. 7c), which is fed to the first input of the coincidence element 39. From the output of the frequency detector 36, the video pulse Uze (Fig. 7d). the shape of which varies according to the law of a linearly falling saw is fed to the input of the differentiating circuit 37. The output pulse (Fig. 7e) of which is not passed by the same-field valve 38. Therefore, the voltage does not reach the second input of the element 39, Key 40 does not open and false signal (interferer).

received on the image channel at frequency f3, is suppressed.

If a false signal (interferer) is received on the first combinational channel at the frequency (Fig. 5c), then in mixer 8 it is converted to the voltage of the following frequencies:

fl1 fx1 + Y t-fr- Y 11, f | 2 2fr + y2t-fK1- Y t fnp + (yj; y) t.

However, only the voltage fi2 falls into the passband A fi of the intermediate frequency amplifier 9

Unp4 (t) Unp X XCOS 2 H fnp t + (fa (t) - JT (Y2 - y) t2 + yjn

0 t gl

where fnp 2fr - fid is the intermediate frequency.

This voltage goes to the second input of the multiplier 41, the first input of which receives the received chirp-MFMN signal from the output of the wideband amplifier 4. The output of the multiplier 41 produces a voltage

Ur2 (t) Ur2 COS (4 JTfrt -f-Jryz t2 + p ()

0 t gi.

which falls in the passband A f2 of the bandpass filter 42. The key 46 does not open and a spurious signal (interferer) received on the first combination channel at the frequency fKi is suppressed.

For a similar reason, the spurious signal (interference) received on the second Raman channel on the frequency is also suppressed.

Thus, the proposed indicator device, in comparison with the prototype, provides an increase in the noise immunity and reliability of the visual evaluation of the parameters of the received signal with combined linear frequency modulation and multiple phase shift manipulation. This is achieved by suppressing spurious signals (noise) received in the mirror and combinational channels.

Claims (1)

Invention Formula Indicator device auth. St. No. 1682788. characterized in that, in order to increase the reliability of the visual estimation of parameters, by suppressing spurious signals on the specular and combinational channels, a third frequency detector, a third differentiating circuit, a unipolar gate and a coincidence element are connected in series to the second multiplier, are introduced into it, hard band-pass filter, first amplitude detector, storage device and threshold unit, second amplitude detector output connected to another the input of the match element, the third and fourth keys, through which the output of the intermediate frequency amplifier is sequentially connected to the information input of the detector, while the other inputs of the third and fourth keys are connected respectively to the outputs of the match element and the threshold block, one input the second multiplier is connected to the output of the wideband amplifier, another input of the accumulator is connected to the reset input of the detector, and the output of the intermediate frequency amplifier is connected to another input of the second multiplier and the inputs of the third frequency detector and the second amplitude detector. I "-0 CV FIG A 2   ftp. g. 2 l # - 5 2PSh ZLbWLl / Shgs. and FIG. 7 FIG. 8