I.V. Kolikov1, V.V. Utkin2, A.V. Letin3

1–3 Military University of Radio Electronics (Cherepovets, Russia)

1–3 vure@mil.ru

The development of radio technical systems in conditions of increasing requirements to them on electromagnetic compatibility and the possibility of functioning in a saturated electromagnetic environment determines the widespread use of complex signals, including those with linear-frequency modulation. Modern communication systems, radar stations and control systems for unmanned systems are examples of radio engineering systems that use signals with linear-frequency modulation. The known advantages of using linear-frequency modulation impose significant limitations on the detection and registration of signals by special services of electronic control in the conditions of a priori uncertainty of frequency-time parameters of signals and low values of signal-to-noise ratio. Given the properties of signals with linear-frequency modulation, it is reasonable to use the autocorrelation function in the task of their detection. The paper presents the results of experimental studies of detection of signals with linear-frequency modulation at critically low signal-to-noise ratios based on the autocorrelation function using the developed software.

The purpose of the paper is to investigate the possibility of detecting radio pulses with linear-frequency modulation at critically low values of signal-to-noise ratio based on the calculation of the autocorrelation function.

The initial radio signals were records of real radar station emissions in raw-format, where each two-byte value represents in-phase and quadrature components.

The developed software on C++ language is a set of algorithms for calculation of normalized autocorrelation function of initial radio signals with the possibility of their artificial noise with selected characteristics of the noise component. The program implements the possibility of selecting the duration of the sampling window of the original signal and the size of the intersection of two successive windows of radio signal samples. The software estimates the width of the main lobe of the autocorrelation function, the number of its oscillations in the main lobe, the dispersion of the autocorrelation function in the region of known large values of the offset.

The paper presents the results of the study of detection of radio pulses with linear-frequency modulation at critically low values of signal-to-noise ratio using the developed software based on the calculation of the autocorrelation function. In the case of analyzing the radio pulses of the TRX-22 radar station, in 86% of cases the signal was detected, with the noise level exceeding the level of the useful signal. Detection was realized without using a priori information about the frequency and time parameters of the signal.

The necessary characteristics of the autocorrelation function of the noise component of the signal samples of the investigated radar station radiation records are investigated. Theoretical results of calculations of the values of the main statistical parameters of the autocorrelation function of radio pulses with linear-frequency modulation in the presence of noise have been confirmed. The value of the detection threshold of radio pulses with linear-frequency modulation on the basis of autocorrelation processing of real radio signals of radar stations is obtained.

Practical significance is that the obtained results of the study can be used in the development of radio technical devices for detecting signals with linear-frequency modulation and in the educational process of training specialists in the operation of special radio technical systems.

Kolikov I.V., Utkin V.V., Letin A.V. Experimental studies on the detection of radio pulses with linear frequency modulation at a critically low signal-to-noise ratio. Electromagnetic waves and electronic systems. 2024. V. 29. № 6. P. 5−12. DOI: https://doi.org/10.18127/j15604128-202406-01 (in Russian)

1. Leushin A.V. LORA modulation as a new kind of modulation. Principle of operation, basic parameters, noise immunity. Radio communication technology. 2022. № 2(53). P. 28–42. (in Russian)
2. Why ExpressLRS is the best radio link now? [Electronic resource] – Access mode: https://www.oscarliang.com/expresslrs, date of reference 17.06.2024.
3. Babanov N.Yu., Dmitriev V.V., Zamyatina I.N. Chirped waveforms in non-linear radar applications. Bulletin NGIEI. 2018. № 3(82). P. 18‒27. (in Russian)
4. Dotsenko V.V., Osipov M.V., Khlusov V.A. Rising of energetic potential of radar with continuous LFM-signal. Reports of TUSUR. 2011. № 1(23). P. 29–33. (in Russian)
5. Kupryashkin I.F., Sokolik N.V. Algorithm of signal processing in the radar system with continuous frequency modulated radiation for detection of small-sized aerial objects, estimation of their range and velocity. Journal of the Russian Universities. Radioelectronics. 2019. V. 22. № 1. P. 39–55. DOI 10.32603/1993-8985-2019-22-1-39-47. (in Russian)
6. Wang. P., Qiu T.S., Li J.-C., Tan H.-F. Parametrs estimation of LFM signal based on Gaussian-weighted fraction Fourier transform. Journal of Communications. 2016. V. 37. № 4. P. 107–115. DOI 10.11959/j.issn.1000-436x.2016077.
7. Utkin V.V., Kolikov I.V., Bosyi A.S. Method for evaluating the parameter of a radio emission source located on an unmanned aerial vehicle of an aircraft type, based on the Doppler effect. Electromagnetic waves and electronic systems. 2020. V. 25. № 6. P. 32−37. DOI 10.18127/j15604128-202006-04. (in Russian)
8. Tuzov G.I. Statistical theory of reception of complex signals. M.: Soviet radio. 1977. 400 p. (in Russian)
9. Sokolik N.V. Determination of Fast-Moving Objects’ Speed and Range with Linear Frequency Modulation Continuous Wave Radar Using Autocorrelation Scheme. Journal of the Russian Universities. Radioelectronics. 2020. V. 23. № 2. P. 63–72. DOI 10.32603/1993-8985-2020-23-2-63-72. (in Russian)
10. Pavlikov S.N., Ubankin E.I. Study of the autocorrelation function of a new class of broadband signals. H&ES Research. 2019. V. 11. №. 3. P. 46–59. DOI 10.24411/2409-5419-2018-10268. (In Russian)
11. Boykov I.V., Pivkina A.A. On one approximate method for recovering a function from its autocorrelation function. University proceedings. Volga region. Physical and mathematical sciences. 2022. № 3(63). P. 43–57. DOI 10.21685/2072-3040-2022-3-5. (In Russian)