Demodulation of Energy Hidden Linear-Frequency-Modulated Signals
DOI:
https://doi.org/10.20535/RADAP.2021.86.45-51Keywords:
demodulation, linear-frequency-modulated signal, autocorrelation algorithm, a priori uncertainty, energy latent signal, correlation method, radio monitoring, complex signal, broadband signalAbstract
Statement of the problem in general
Recently, there has been a tendency to increase the number of telecommunications systems that use spread spectrum signals: binary phase-shift keying (BPSK) signals with linear frequency modulation, chirp signals and their combinations. Due to this, the anti-jamming of telecommunication systems is increased, the stealth mode of their functioning is provided.
This tendency raises issues in the field of radio monitoring systems implementation. The use of spread-spectrum signals in telecommunication systems significantly reduces the spectral height of radio emission and their energy availability. Detection such radio emission, classifying the signals, measuring their parameters and demodulation in the absence of any information about the signals of telecommunication systems, is a complex scientific and technical task.
Analysis of recent research and publications
One of the important scientific and technical task in the direction of research of telecommunication systems radiomonitoring problems that use signals with linear frequency modulation (chirp signals), is demodulation of such signals in the conditions of uncertainty.
Previously, scientists solved the problem of detecting an energetically hidden chirp signal, determining its parameters using a discrete model of an autocorrelation receiver with quadrature processing and recognizing linear frequency modulation based on an autocorrelation receiver with double quadrature processing. Therefore, the problem of demodulation of energetically hidden signals with linear frequency modulation should be solved using the obtained scientific results as much as possible.
The scientific literature does not sufficiently cover the issue of demodulation of energetically hidden chirp signals of telecommunication systems in conditions of a priori uncertainty about the type and parameters of the signal and energetic concealment.
Thus, the relevance of the article is determined by its purpose, which is to develop a methodological apparatus for demodulation (recognition of the type of frequency) of energy-hidden chirp signals of telecommunications systems based on the autocorrelation method.
Presenting the main material
The article analyzes the uncertainty diagram of a rectangular chirp radio pulse. Characteristic features and cross-sectional features of the uncertainty diagram are revealed. An approach to demodulation of received energetically hidden chirp signals based on the use of the features of the uncertainty diagram of the elementary radio pulse is proposed. The possibility of their demodulation is substantiated. Simulation of the remodeling procedure was performed using Matlab R2016a and MathCAD 14 software packages. The simulation results confirm the ability of the proposed algorithm to demodulate chirp signals in the input combination at low signal-to-noise ratios.
Conclusion
To solve the problem of demodulation of chirp signals of telecommunication systems, an approach based on the results of the analysis of the location of the elliptical uncertainty diagram is used.
The sequence of steps for demodulation of chirp signals is determined.
It is established that the proposed autocorrelation algorithm with double quadrature processing is able to demodulate a chirp signal in the input combination with a signal-to-noise ratio of less than one.
The simulation results show that during the accumulation of 10-3 s it is possible to demodulate the binary symbols of the chirp signal with base 104 at a signal-to-noise ratio of minus 17 dB with a probability of error of 10-2.
Prospects for further development of the study
In the future, it is advisable to explore the possibility of recognizing other signals (BPSK), which can be used in the energy-hidden mode of telecommunications systems.
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Перелік посилань
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