Search for binary code sequences with low autocorrelation sidelobes by the evolutionary method
Keywords:
code sequence, sidelobe, autocorrelation function, genetic algorithm, recombination, selectionAbstract
Introduction: The parameters chosen for complex coded signals used in active radar systems of aircraft for detecting objects largely
determines their qualitative characteristics and the possibility of covert operation. An important task in the design of such on-board
systems is the formation of ensembles of pseudorandom-noise binary code sequences of a fixed length with predefined characteristics.
Purpose: Search for PRN binary code sequences of a given length, optimal by the criterion of the minimum level of the sidelobes of the
aperiodic autocorrelation function. Results: A procedure of search for binary code sequences with specified parameters based on the
evolutionary approach is proposed. The minimum level of positive sidelobes of the autocorrelation function is used as a criterion for
the selection of code sequences. An additional restriction is imposed on the length of a substring of codes of the same character. The
possibility of forming a representative array of sequences with the best ratio of the main peak of the aperiodic autocorrelation function
to its maximum positive sidelobe is shown on the example of 31-bit code sequences. An algorithm is proposed for generating a PRN
series of signals using the code sequences found. The Hamming distance is used as a measure of the difference between two binary code
sequences in the series. The proposed approach is advantageous as compared to the well-known method of generating PRN signals based
on pseudorandom m-sequences. Practical relevance: The results obtained can be used in algorithms of airborne radar systems with a
high range resolution to detect physical objects on the background of an underlying surface, for example, objects on the water surface.