RU1840860C - Device for decoding phase-shift keyed signals - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to devices for demodulating and analysing radio signals. The device includes a phase comparator unit having a certain design, and a synchronous reference signal generator, the output of which is connected to the input of the phase comparator unit, wherein the input of the synchronous reference signal generator is connected to the input of the device through a normally closed switch, the control input of which is connected to the input of the device through a delayed signal envelope detector and a delay line, wherein the on input and the off input of the synchronous reference signal generator are connected to the output of an input signal envelope detector and the delayed signal envelope detector, respectively, and the signal input of the phase comparator unit is connected to the output of the delay line.

EFFECT: high noise-immunity and accuracy of determining time and phase parameters of modulation.

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Description

The present invention relates to the field of radio engineering, in particular to devices for demodulation (decoding) and analysis of radio signals, and can be used to decode phase-shifted signals (PMS) in radio intelligence stations (RTR).

In known devices for decoding (analyzing) PMS with an a priori unknown frequency and modulation parameters to isolate the modulating function, the analyzed signal from the output of the IFR of the reconnaissance receiver is fed to a phase comparison device (UFS), for example, a phase detector, to the second input of which a reference signal is supplied. The result of the analysis is a set of signals by which the code structure of the received signal can be reconstructed (see, for example, A.K. Ivakin "On one radar reconnaissance method with phase-coded manipulated probing signal" WCE, ser. TRR, issue 6, 1968). Moreover, the reference signal is formed either by delaying the received signal in time.

A disadvantage of the known technical solutions, where the reference signal is generated directly from the received one, is reduced noise immunity and measurement accuracy (compared to the case when the frequency of the received signal is precisely known and an autonomous generator can be used as the reference signal source) due to the interfering effect of noise, which this is fed to the phase comparison device via both channels - signal and reference. In addition, in cases of receiving PMS with multiphase codes, devices with the formation of the reference signal according to the Pistolkors scheme do not provide the possibility of determining the phase modulation law, since the reference signal also undergoes a phase shift, the magnitude of which depends on the code shift of the analyzed signal.

The aim of the invention is to increase the noise immunity and accuracy of determining the time and phase parameters of the modulation of the FMS, including signals with multiphase codes. In accordance with the invention, this goal is achieved as a result of the fact that the source of the reference signal is made in the form of a phased generator with additional controls (normally open strobe key, envelope detector, delay line with a delay time equal to the setup time of the oscillation phase of the phased generator, which shorter than the code interval). The controls ensure that the generator is started under the influence of the signal to be decoded and generates harmonic oscillations with a “remembered” initial phase during the duration of the input signal. The output signal of the generator serves as a reference for the phase comparison device, which is made in the form of a parallel-connected phase detector and a digital pulse phase meter, and the output of the phase detector through the former is connected to the control input of data acquisition from the phase meter. The signals from the outputs of the shaper (reflecting the time structure of the code) and the phase meter (reflecting the phase structure) can be sent to subsequent processing devices to perform actions in accordance with the purpose of this equipment (display and registration of signal parameters, control of processing devices to optimize reception conditions, formation of interference signals, etc.).

The proposed FMS decoding device, in comparison with the known ones, has improved noise immunity and accuracy in determining the time and phase parameters of modulation of phase-shifted signals, including signals with multiphase codes.

An analysis of the accuracy characteristics and speed of the proposed decoding device, based on the results of experimental verification of the main components (including a digital pulse phase meter and a phased generator), confirmed its advantages compared to the known ones in terms of increasing noise immunity and accuracy, as well as the ability to decode multiphase codes.

The invention will be clear from the description below and the attached block diagram (Fig. 1).

The proposed FMS decoding device contains a phased generator 1 (FG) connected to the output of the receiver through a normally open gate key 2 (K), an envelope detector of the input signal 3 (DOVS), a phase detector 4 (PD), one input of which is connected via a delay line 5 (LZ) with the output of the receiver, and the second with the output of the phased generator, a digital pulse phase meter 6 (FM) connected to the output of the receiver (via the delay line), with the output of the phased generator and through the former 7 (F) with the output of the phase detector and the detector total delayed signal 8 (DOS), included after the delay line and connected to a gating key, a phased generator and a phase meter.

The operation of the device is as follows. The received (analyzed) signal from the output of the receiver goes to the inputs of the envelope detector of the input signal 3, delay line 5 and through a normally open key 2 to the phased generator 1.

The signal from the output of the envelope detector of the input signal 3, arriving at the other (control) input of the phased generator 1, almost simultaneously with the signal arriving at the first - in-phase - input, opens (turns on) the normally locked phased generator 1. Under the influence of the studied signal in this way turned on phased generator 1 self-oscillations occur with a frequency and phase corresponding to the signal. The oscillation establishment time in the phased generator 1 (by appropriate selection of the circuit parameters) is shorter than the minimum duration of a single code interval (from the range to be analyzed), for example, less than 0.5 μs (a fairly typical minimum duration of a single code of reconnaissable FMS). Such a phased generator can be performed in various ways. For example, according to the scheme described in the article by Vekslin V.N. et al. "On the selection of the optimal scheme of a phased oscillator", VCE, ser. XIV, no. 4, 1963, where the settling time is provided ≤0.2 μs.

The signal passed through the delay line 5 is fed to the inputs of the envelope detector of the input signal 8, phase detector 4, and phasemeter 6. The output signal of the envelope detector 8, after the delay time corresponding to the oscillation establishment time in the phased generator 1, is supplied to the control input of the gate key 2 and closes it , excluding the further effect of the received signal on the oscillation parameters of the phased generator. The output signal of the phased generator 1 is fed to the other inputs of the phase detector 4 and phasemeter 6, where the phase comparison is performed. As a result of comparing the phases of the reference and decoded signals, a voltage is generated in the phase detector 4, which has differences at the moments of phase change inside the decoded signal. This voltage is supplied to the driver 7, which generates signals (read pulses) at time instants corresponding to a phase change. The signals from the output of the shaper 7 are fed to the input for controlling the acquisition of information from the phasemeter 6, which gives the values of the phase difference Δφ of the compared signals at the moments of phase change inside the FMS in accordance with the code.

Thus, at the output of the shaper 7, a sequence of signals is formed that reflects the temporal structure of the code, and at the output of the phasemeter 6, a sequence of signals reflects the phase structure of the code of the analyzed FMS. These signals are issued to the device for further processing. At the end of the input signal by the trailing edge of the video signal from the envelope detector 8, the phased generator 1 is locked, the phase meter 6 is reset, and the gate key 2 is opened, preparing the circuit for receiving the next signal.

Claims (2)

1. A device for decoding phase-shifted signals for electronic intelligence receivers, comprising a phase comparison unit and a synchronized reference signal generator, the output of which is connected to the input of the phase comparison unit, characterized in that, in order to increase decoding noise immunity, the input of the synchronized generator is connected to the device input through normal a closed key, the control input of which is connected to the input of the device through the detector of the envelope of the delayed signal and the delay line, while the input Turning off the generator and input are respectively connected to the output of the envelope detector input signal and the delayed signal of the envelope detector and the signal input of the phase comparator is connected to the output of the delay line. 2. The device for decoding phase-shifted signals according to claim 1, characterized in that, in order to improve accuracy, the phase comparison unit is made in parallel with the inputs of a phase detector and a digital phase meter, the reset input of which is connected to the output of the envelope detector of the delayed signal, and the output a phase detector through a pulse shaper is connected to the control input of the pulse phase meter.

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