RU2233551C2 - Radio link noise station - Google Patents

Abstract

FIELD: radio engineering; developing new radio-link noise stations and retrofitting existing ones.

SUBSTANCE: proposed station is designed for continuous radio reconnaissance and suppression of radio links by correlating convolution and attenuating noise signal arriving from transmitting antenna (reflected from underlying terrain). To this end use is made of chirp signal as target noise and local oscillator signal for additional frequency conversion of signals received. Chirp noise is attenuated due to its suppression in rejection filter and expansion of gain-frequency path at second-mixer output. Radio link noise station has receiving antenna 1, mixers 2.1, 2.2, band filters 3.1, 3.2, rejection filter 4, switches 9.1, 9.2, receiver 5, analyzer 6, limiting amplifier 7, detector 8, modulator 14, power amplifier 15, transmitting antenna 16, reference oscillator 10, frequency divider 11, frequency setting unit 12, and line frequency-modulated generator 13.

EFFECT: provision for continuous radio link reconnaissance and noise attenuation.

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Description

The invention relates to the field of radio engineering and can be used in the development of new and modernization of existing jamming stations for radio communication lines.

A known device for generating interference signals for radio stations [US patent No. 3953851, class. N 04 K 3/00, 1976], containing a series-connected receiving antenna, a mixer, parallel-connected the first receiving channel and the second receiving channel with the delay unit, block And, indicator, modulator, power amplifier and transmitting antenna, while the second input mixer connected to the output of the power amplifier.

To detect suppressed radio lines, a local oscillator signal is input from the output of the power amplifier to the mixer input. Such a construction of the known device requires the continuous inclusion of a radiation power amplifier when conducting reconnaissance of suppressed radio links. Constant work on radiation reduces the electromagnetic compatibility of the device for generating interference signals for interference radio stations with electronic means of other purposes, the frequencies of which are within the span.

A disadvantage of the device for generating interference signals for radio stations is the low electromagnetic compatibility when searching for suppressed radio lines with other electronic means whose frequencies are within the field of view.

A known station for suppressing radio telegraph signals [US patent No. 4214208, class. H 04 To 3/00, 1980], comprising a transceiver antenna, the output of which is through a series-connected switch "reception-transmission", the receiver is connected to an adjustable pulse generator, the output of which is connected to the second inputs of the switch "reception-transmission" and key, the second input of which through the exciter is connected to the second output of the receiver, and the key output through the power amplifier is connected to the transceiver antenna.

To detect the emitted radio telegraph signals, the transceiver antenna is connected to the input of the receiving device through the receive-transmit switch. At the output of the adjustable pulse generator, a pulse is generated corresponding to the end of the received high-frequency pulse of the telegraph signal, which is used to control the receive-transmit switch and the key. The receive-transmit switch disconnects the input of the receiver from the transceiver antenna, and the key connects the exciter output to the input of the power amplifier.

The disadvantage of this jamming station is the impossibility of reconnaissance of radio telegraph signals during radiation by a high-frequency energy transmitter.

Of the known jamming stations for radio lines, the closest in technical essence and the achieved effect is a radio jamming station [see Paly A.I. Electronic warfare. Means and methods of suppressing and protecting electronic systems. - M. 1981, p. 56], consisting of a series-connected transceiver antenna, antenna switch, receiver, analyzer, noise voltage generator, modulator, power amplifier, the output of which is connected to the second input of the antenna switch.

To detect the emitted radio signals, the transceiver antenna is connected through the antenna switch to the input of the receiving device. The received radio signals from the output of the receiver are fed to the input of the analyzer. The analyzer determines the type of modulation, the width of the spectrum and other parameters of the received signals. When a suppressed signal is detected from the analyzer output, a signal is received at the input of the radio noise shaping device, allowing the formation of noise voltage. At the same time, the antenna switch disconnects the input of the receiver from the transceiver antenna and connects the output of the power amplifier to it.

The disadvantage of the station is the impossibility of continuous suppression and reconnaissance of suppressed radio lines.

The technical result of the invention is the ability to continuously conduct radio reconnaissance and suppress radio lines of the proposed interference station due to correlation convolution and attenuation of the interference signal from the transmitting antenna (reflected from the underlying surface).

This result is achieved by the fact that in a known radio interference station containing a receiving antenna, a receiver, an analyzer and a series-connected modulator, a power amplifier and a transmitting antenna, a first mixer, a first band-pass filter, a parallel notch filter with the first key, the second mixer and the second band-pass filter, series-connected amplifiers are introduced between the first output of the analyzer and the second input of the first key a spruce-limiter and a detector, as well as a series-connected reference generator, a frequency divider, a frequency setting unit, to the second input of which a second output of the analyzer is connected, a linear frequency-modulated generator and a second key, the second input of which is connected to the output of the detector, and the output of the second the key is connected to the input of the modulator, and the second and third inputs of the linear frequency-modulated generator are connected to the corresponding outputs of the frequency divider and the reference generator, and the fourth input of the linear h -frequency generator is modulated control input station interference, the second inputs of the first and second mixers coupled to the first input of the second key.

As interference it is necessary to use a linear frequency-modulated (LFM) signal. The width of the amplitude-frequency spectrum (frequency deviation) of the LFM interference signal (ΔF _P.LFM ) is selected from the condition [see Paly A.I. Electronic warfare. M .: Military Publishing House, 1974, 272 p., See p. 110, first paragraph above]:

ΔF _P.LFM = (2-3) ΔF _PR , (1)

where ΔF _PR is the receiver bandwidth. The bandwidth of the receiver _PR ΔF matched to the bandwidth of the desired signal ΔF _C.

Correlation convolution of the interference signal S $\genfrac{}{}{0ex}{}{\text{1}}{\text{P.LM}}$ coming to the input of the receiving antenna from the transmitting antenna (reflected from the underlying surface), occurs on the first mixer. Width of the amplitude-frequency spectrum of the minimized interference ΔF $\genfrac{}{}{0ex}{}{\text{1}}{\text{P}}$ is determined from the vertical section of the body ρ (τ, F) by the plane of zero time mismatch τ = 0, where τ, F are the time and frequency mismatches, respectively, [Radioelectronic systems: construction principles and theory. Directory. Shirman Y.D., Losev Yu.I., Minervin N.N., Moskvitin S.V., Gorshkov S.A. et al. / Ed. POISON. Shirman. - M.: ZAO MAKVIS, 1998.828 s, see p. 428, expression (18.10) and p. 437, fig. 18.7, b] according to the formula

ΔF $\genfrac{}{}{0ex}{}{\text{1}}{\text{P}}$ = 1 / T _LFM , (2)

where T _LFM is the duration of the folded LFM interference signal at the output of the first mixer.

So, for the duration of the LFM interference signal T _LFM = 0.1 s, the width of the amplitude-frequency interference spectrum ΔF $\genfrac{}{}{0ex}{}{\text{1}}{\text{P}}$ the output of the first mixer will be 10 Hz.

The width of the amplitude-frequency spectrum of the useful signal ΔF _{C. The LFM} at the output of the first mixer expands by ΔF _LFM :

ΔF _{C. LFM} = ΔF _LFM + ΔF _C. (3)

The amplitude-frequency characteristics of the first band-pass filter and the notch filter are consistent with the amplitude-frequency spectrum of the useful signal | S _C (f) | and interference | S $\genfrac{}{}{0ex}{}{\text{1}}{\text{P}}$ (f) | respectively.

The rejection filter suppression bandwidth ΔF _RF is selected from the condition

ΔF _RF = (2 ÷ 3) ΔF _P. (4)

For a notch LC filter, the attenuation should be more than 30 dB [Eaal R. Filter Calculation Guide: Trans. with him. - M.: Radio and Communications, 1983, - 752 p., See p. 75].

The loss of the useful signal K _POT.S with a percentage when passing the notch filter is determined by the formula

K _POT.S = [ΔF _RF / (ΔF _LFM + ΔF _C )] 100%, (5)

where ΔF _RF is the rejection filter suppression bandwidth. So, for example, for the suppression band of the notch filter from (4) - ΔF _RF = 30 Hz, the deviation of the frequency of the local oscillator signal - ΔF _LFM = 2 × 10 ⁴ Hz and the spectrum width of the useful signal - ΔF _C = 10 ⁴ Hz loss K _POT from ( 5) make up about 0.1 percent of the input level of the useful signal.

In the second mixer, demodulation (restoration) of the amplitude-frequency spectrum of the useful signal | S _{C (} f) | and expanding the amplitude-frequency spectra of the residual signal | S $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ (f) |.

Interference Power P $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ at the output of the second bandpass filter it will be attenuated K _OSL times:

P _OUT.CM2 = P _IN.CM2 / K _OSL , (6)

where K _OSL = ΔF $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ / ΔF $\genfrac{}{}{0ex}{}{\text{1}}{\text{P}}$ ;

ΔF $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ - the width of the amplitude-frequency spectrum of the remains of the interference signal at the output of the second mixer;

ΔF $\genfrac{}{}{0ex}{}{\text{1}}{\text{P}}$ - the width of the amplitude-frequency spectrum of the remnants of the interference signal at the input of the second mixer.

So, for example, for the spectrum width of the interference residues at the input of the second mixer ΔF $\genfrac{}{}{0ex}{}{\text{1}}{\text{P}}$ = 50 Hz, and after their conversion in the second mixer, the spectrum width of the interference residues ΔF $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ will be approximately 2 × 10 ⁴ Hz, the attenuation of K _OSL from (6) will be about 400 times, or 26 dB.

Then, taking into account the attenuation of the interference signal in the notch filter by more than 30 dB and the decrease in the spectral density of the interference power due to the expansion of its spectrum | S $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ (f) | in the second conversion, K _OSL = 26 dB, the total attenuation of the interference signal will be 56 dB.

Spectrum-converted S signals $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ (f) and S _C (f) go to the input of the second band-pass filter. The frequency response of the second bandpass filter is consistent only with the spectrum of the useful signal | S _C (f) |.

The power of the useful signal P _OUT.PF2 at the output of the second band-pass filter, without taking into account losses in the notch filter, exceeds the power of the useful signal at the input of the first mixer (P _VCH.CM1 ) by the compression coefficient over the spectrum of _KF :

P _OUT.PF2 = K _SJ × P _IN.CM1 , (7)

where K _SJ = 1 + ΔF _{C. LFM} / ΔF _C.

So, for the frequency deviation ΔF _LFM = 2 × 10 ⁴ Hz and the width of the amplitude-frequency spectrum of the useful signal at the output of the second band-pass filter ΔF _C = 10 ⁴ Hz, the compression coefficient K _SJ from (7) will be 3 times.

The power of the useful signal P _OUT.PF2 taking into account losses in the notch filter at the output of the second band-pass filter 4.2 is found from the expression

P _OUT.PF2 = | K _SJ -K _POT | × P _BX.CM1. (8)

For the obtained compression coefficients in the spectrum K _SJ = 3 and losses K _POT = 0.001, the modulus of the difference of the coefficients from (8) will be 2.999 times.

Thus, in the proposed station, with an additional frequency conversion of the useful signal S _C (f) and the interference S _{P. LFM} (f), a useful signal is transmitted almost without loss to the input of the analyzer and attenuation of 56 dB or more of the interference minimized by the LFM spectrum is achieved , which provides the possibility of continuous reconnaissance and suppression of radio lines.

Figure 1 presents a structural diagram of a radio jamming station.

Figure 2 presents the amplitude-frequency spectra of the useful signal and the LFM interference at the input of the receiver, at the output of the first and second band-pass filters and the amplitude-frequency characteristics of the first band-pass filter, notch filter and second band-pass filter.

The radio jamming station (Fig. 1) contains a receiving antenna 1, mixers 2.1 and 2.2, bandpass filters 3.1 and 3.2, a notch filter 4, a receiver 5, an analyzer 6, an amplifier-limiter 7, a detector 8, keys 9.1 and 9.2, a reference generator 10 , a frequency divider 11, a frequency setting unit 12, a linear frequency-modulated generator 13, a modulator 14, a power amplifier 15 and a transmitting antenna 16.

Moreover, the receiving antenna 1 through the first mixer 2.1, the first bandpass filter 3.1, parallelly connected the notch filter 4 with the first key 9.1, the second mixer 2.2, the second bandpass filter 3.2, receiver 5, analyzer 6, amplifier-limiter 7, detector 8, second key 9.2 , a modulator 14 and a power amplifier 15 is connected to a transmitting antenna 16, while the reference generator 10 is connected through a frequency divider 11, a frequency setting unit 12, the second input of which is connected to the second output of the analyzer 6, and a linear frequency-modulated the generator 13 is connected to the first input of the second key 9.2 and the second inputs of the first and second mixers 2.1 and 2.2, the second input of the linear frequency-modulated generator 13 is connected to the output of the frequency divider 11, the third input of the linear frequency-modulated generator 13 is connected to the output of the reference generator 10, the fourth input of the linear frequency-modulated generator 13 is the control input of the interference station, and the output of the detector 8 is connected to the second input of the first key 9.1.

To implement a technical solution, standard industrial equipment can be used. So, for example, mixers 2.1 and 2.2 are a diode frequency converter, made according to a balanced circuit [M.S. Shumilin, V.B. Kozyrev, V.A. Vlasov. Design of transistor cascades of transmitters. Textbook for technical schools. - M.: Radio and Communications, 1987. - 320 p., P. 178, fig. 2.77].

Bandpass filters 3.1 and 3.2 can be performed according to the scheme of a three-link bandpass filter [Radio transmitting devices. M.V. Balakirev, Yu.S. Vokhmyakov, A.V. Zhurikov et al. / Ed. O.A. Chelnokova. - M .: Radio and communication, 1982. - 256 p., P. 94, fig. 4.12].

The notch filter 4 can be performed, for example, according to the scheme of the notch LC filter of the sixth order [Eaal R. Reference filter calculation: Per. with him. - M.: Radio and Communications, 1983, - 752 p., See p.75, Fig.8.21].

Amplifier-limiter 7 is a two-way limiter made according to the scheme [MV Halperin Practical circuitry in industrial automation. - Energoatomizdat, 1987. - 132 p., P. 131, Fig.3.20, c, d], and can be implemented, for example, on the high-speed operational amplifier 1433UD1 [Perelman B.L., Shevelev V.I. Domestic microcircuits and foreign analogues. Reference, "Scientific and Technical Center Mikrotekh", 2000 - 375 p., P. 182, 211].

Detector 8 in the case of converting frequency-modulated signals can be performed, for example, on a 533XP1 series microcircuit, and in the case of amplitude-modulated signals, on a 175DA1 or K175DA1 series microcircuits [B. Perelman, V. Shevelev Domestic microcircuits and foreign analogues. Reference book, "Scientific and Technical Center Mikrotekh", 2000 - 375 p., P. 49, 204].

The keys 9.1 and 9.2 can be performed, for example, on microcircuits of the 286KT2 series (K286KT2) [Perelman B.L., Shevelev V.I. Domestic microcircuits and foreign analogues. Reference book, "Scientific and Technical Center Mikrotekh", 2000 - 375 p., P. 193, 222].

The reference generator 10 is a pulse generator with quartz stabilization, made, for example, on a chip series K564LN2 (VN Veniaminov, ON Lebedev, AI Miroshnichenko. Chips and their application: Reference. Manual. - 3- e ed., revised and enlarged. - M.: Radio and Communications, 1989, 240 pp., p. 210, Fig. 7.10, d].

The frequency divider 11 can be performed, for example, on a chip series KM155IE8 [Perelman BL, Shevelev V.I. Domestic microcircuits and foreign analogues. Reference book, "Scientific and Technical Center Mikrotekh", 2000 - 375 p., P. 129, 81].

The frequency setting unit 12 can be performed in a multiplexed manner, for example, on a chip of the K555KP18 series [Perelman B.L., Shevelev V.I. Domestic microcircuits and foreign analogues. Reference book, "Scientific and Technical Center Mikrotekh", 2000 - 375 p., P. 44, 89].

The LFM generator 13 is, for example, a circuit consisting of a phase locked loop (PLL) generator [Design of radar receiving devices: Textbook. A manual for radio engineering specialists of universities, A.P. Golubkov, A.P. Lukoshkin et al. / Ed. M.A. Sokolova. M .: Higher. school., 1984. - 335 p., p. 176, fig. 6.28] and a digital synthesizer of the LFM signal [Kochemasov V.N., Belov L.A., Okoneshnikov V.S. Signal generation with linear frequency modulation. - M .: Radio and communications, 1983. - 192 p., P. 55, fig. 4.12]. PLL ensures accurate tuning of the frequency of the controlled oscillator to the frequency of the reference LFM signal generated by the digital synthesizer, and reducing the noise level in the signal of the LFM generator 13.

The inventive radio jamming station (figure 1) operates as follows.

In the initial state, the notch filter 4 is short-circuited by the key 9.1. The reference generator 10 generates a highly stable sequence of clock pulses with a repetition period T _T. These pulses are fed to the corresponding inputs of the chirp generator 13 and the frequency divider 11. The frequency divider 11 is designed to generate pulses to trigger the chirp signal. The pulse repetition period at the output of the frequency divider 11 is selected from the condition T _LFM >> T _T. From the output of the frequency divider 11, the start pulses of the LFM signal are fed to the first input of the frequency setting unit 12 and the second input of the LFM generator 13. A parallel binary frequency setting code is supplied to the second input of the frequency setting unit 12 from the second output of the analyzer 6. The frequency setting code is written to the first input of the LFM generator 13 when each video pulse arrives at the first input of block 12.

To reduce the level of power penetrating the input of the receiving antenna 1, a transmitting antenna 16 with a polarization vector rotated 90 degrees is used.

Conducting intelligence starts from the moment the control signal arrives at the fourth input of the LFM generator 13. The LFM signal from the output of the LFM generator 13 is fed to the second input of the second key 9.2 and, as a local oscillator signal, to the second inputs of the first and second mixers 2.1 and 2.2.

Frequency response of the LFM signal | S _LFM (f) | at the output of the chirp generator 13 is shown in figb.

From the output of the receiving antenna 1, the useful signal S _C (f) is fed to the input of the first mixer 2.1. The amplitude-frequency spectrum of the useful signal | S _C (f) | at the inlet of the first mixer 2.1 shown in figa. In the first mixer 2.1, the signal S _C (f) is converted in frequency and spreads over the spectrum by the amount of ΔF _LFM . Frequency response of the signal | S _{C. LFM} (f) | shown in Fig.2g. From the output of the mixer 2.1, the signal S _{C. LFM} (f) through a series-connected bandpass filter 3.1 and the first key 9.1 is fed to the input of the second mixer 2.2. The frequency response of the band-pass filter 3.1 is shown in Fig.2d. In the second mixer 2.2, the initial signal spectrum | S _C (f) | (fig.2z). The reconstructed useful signal S _C (f) from the output of the second mixer 2.2 through the second band-pass filter 3.2 is fed to the input of the receiver 5. The amplitude-frequency spectrum of the useful signal | S _C (f) | the output of the second band-pass filter 2.2 is shown in Fig.2k. The receiver 5 amplifies and frequency converts the received signal. From the output of the receiver 5, the signal S _C (f) is input to the analyzer 6. The analyzer 6 determines the type of modulation (manipulation), the width of the spectrum, and other parameters of the received signals [see Paly A.I. Electronic warfare. Means and methods of suppressing and protecting electronic systems. - M. 1981, p. 56].

The signal S _C (f) from the first output of the analyzer 6 through the amplifier-limiter 7 is fed to the input of the detector 8. A positive level from the output of the detector 8 is supplied to the inputs of the keys 9.1 and 9.2.

At the same time, to adjust the average frequency of the chirp generator 13 from the second output of the analyzer 6, information on the frequency of the explored signal in the form of a parallel binary code is received at the second input of the frequency setting unit 12.

A positive level at the second input of the second key 9.2 allows the LFM signal to pass to the input of the modulator 14. Modulator 14 generates LFM interference at the frequency of the explored signal S _C (f). From the output of the modulator 14, the chirped noise through the power amplifier 15 is fed to the input of the transmitting antenna 16. The transmitting antenna 16 provides radiation into the space of high-frequency energy supplied by the feeder [see Paly A.I. Electronic warfare. Means and methods of suppressing and protecting electronic systems. - M. 1981, p. 57].

At the input of the receiving antenna 1, along with the useful signal S _C (f), a part of the power of the chirp interference S $\genfrac{}{}{0ex}{}{\text{l}}{\text{P.LM}}$ (f) radiated by the transmit antenna 16 (reflected from the underlying surface). Spectral view of the useful signal S _C (f) (solid line) and LFM interference S $\genfrac{}{}{0ex}{}{\text{l}}{\text{P.LM}}$ (f) (dashed line) are shown in FIG.

Useful signal S _C (f) and chirp interference S $\genfrac{}{}{0ex}{}{\text{l}}{\text{P.LM}}$ (f) go to the input of the first mixer 2.1. In the first mixer 2.1, a correlation convolution of the LFM interference S occurs $\genfrac{}{}{0ex}{}{\text{l}}{\text{P.LM}}$ (f) and spreading the spectrum of the wanted signal S _C (f) (see FIG. 2d). From the output of the first mixer 2.1, the converted signals through the first bandpass filter 3.1 are fed to the inputs of the parallelly connected notch filter 4 and the first key 9.1. A positive level at the second input of the key 9.1 allows the connection of a notch filter 4 between the output of the first band-pass filter 3.1 and the input of the second mixer 2.2. The frequency response of the notch filter 4 is shown in Fig.2E. From this moment in time, the suppression of the correlation-minimized interference signal of the LFM signal begins.

The width of the spectrum of the useful signal ΔF _{C. LFM} at the output of the first band-pass filter 3.1 exceeds the notch band ΔF of the _RF notch filter 4 (see Fig. 2d, e). From the analysis of expression (5), it follows that the useful signal S _{C. LFM} (f) passes the notch filter 4 almost without loss. The _{form of the} spectra of the useful signal | S _{C. LFM} (f) | and residual chirp interference | S $\genfrac{}{}{0ex}{}{\text{l}}{\text{P}}$ (f) | at the output of the notch filter 4 is shown in Fig.2g.

Useful signal S _{C. LFM} (f) and residual LFM interference S $\genfrac{}{}{0ex}{}{\text{l}}{\text{P.LM}}$ (f) are fed to the input of the second mixer 2.2. In the second mixer 2.2 there is a correlation convolution of the radio signal (restoration of the original spectrum of the radio signal | S _C (f) |) and an additional expansion of the remnants of the spectrum of the chirp interference | S $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ (f) |. Spectral view of the useful signal | S _C (f) | (solid line) and residual chirp interference | S $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ (f) | (dashed line) at the output of the second mixer 2.2 is shown in FIG. Useful signal S _C (f) and residual chirp interference S $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ (f) enter the input of the second band-pass filter 3.2. The frequency response of the band-pass filter 3.2 is shown in Fig.2i. The amplitude-frequency characteristic of the band-pass filter 3.2 is consistent with the amplitude-frequency spectrum of the useful signal | S _C (f) |.

The input of the analyzer 6 receives a useful signal S _C (f) and part of the residues of the chirp interference | S $\genfrac{}{}{0ex}{}{\text{eleven}}{\text{P.LM}}$ (f) | that passed through the second band-pass filter 3.2 (see FIG. 2k).

Thus, in the proposed interference station, it is possible to continuously conduct radio reconnaissance and suppress radio communication lines.

Claims (1)

A radio jamming station comprising a receiving antenna, a receiver, an analyzer and a series-connected modulator, a power amplifier and a transmitting antenna, characterized in that a first mixer, a first band-pass filter, a notch filter with a first key, and a second a mixer and a second band-pass filter, between the first output of the analyzer and the second input of the first key are connected in series-connected amplifier-limiter and detector, and t A reference oscillator, a frequency divider, a frequency setting unit, the second input of which is connected to the second output of the analyzer, a linear frequency-modulated generator and a second key, the second input of which is connected to the output of the detector and the output of the second key are connected to the input of the modulator, are also connected in series the second and third inputs of the linear frequency-modulated generator are connected to the corresponding outputs of the frequency divider and the reference generator, and the fourth input of the linear frequency-modulated generator ora a control input station interference, the second inputs of the first and second mixers coupled to the first input of the second key.

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