**Abstract.** A compression algorithm
for radar signals that has an area of zero sidelobes in the vicinity of the
central peak of the autocorrelation function has been considered. These
signals, which are called coherent additional signals, are a burst of two coherent
phase-code-manipulated pulses coded by a pair of complementary sequences. The
zero sidelobe area of the aucorrelation function of the coherent additional signals
permits to reduce the threshold of detection of radar targets to the noise
level, thus increasing the detection probability. Also, by virtue of the
relatively large base these signals have high compression coefficients, which
makes it possible to solve the problem of discerning targets that are closely
located in space to each other and have close radial velocities as well as
measuring their coordinates with high precision.

The device for compression
of the coherent additional signals consists of the input register with *N*
cells, a discrete transform processor with *N* inputs and two outputs, a
shift register with *Q·N* cells and an adder, where *N* is the number
of the elements in the complementary sequence and *Q* is the parameter
inverse to the duty ratio. It has been shown that the block diagram of the
coherent additional signal compression device is an equivalent block diagram of
a matched filter, the discrete transform processor being the main element of
it. The algorithm of the processor’s operation is an algorithm of fast
Walsh–Hadamard transform (Haramard ordered), the signal graph of which contains
complementary real weighing coefficients «‑1» from the first to the
penultimate iteration. The reports of the discrete transform spectrum for
computing one autocorrelation function are taken from one of the *N*/2
pairs of its outputs. Therefore, *N*/2 various autocorrelation functions
can be obtained — according to the number of the different pairs of the
complementary sequences *N *long.

The considered compression
algorithm for the coherent additional signals makes it possible to achieve
effective real-time solutions of the problems of discerning and measuring the
coordinates of grouped targets of the radar that have close radial velocities.

**Key words**: burst of pulses,
complementary sequences, autocorrelation function, sidelobe, signal detection
threshold, radial velocity, matched filter, Walsh-Hadamard transform, signal
graph, weighting coefficient.

**References**

1.
Ipanov
R.N. Coherent additional signals and their application in radiolocation. *Zhurnal Radioelektroniki - Journal of Radio Electronics, *2015, No. 2.* *Available
at
http://jre.cplire.ru/jre/feb15/8/text.pdf
(In Russian).

2.
Velti. Quaternary codes for pulsed radar. *Zarubezhnaya
radiotehnika - Foreign radiotechnics,* 1961, No. 4, pp. 3-19. (In
Russian).

3.
Trahtman
A.M., Trahtman V.A. *Osnovy teorii diskretnyh signalov na konechnyh
intervalah.* [Undamentals of the theory of discrete signals on finite
intervals]. Moscow, Sov. Radio Publ, 1975, 208 p. (In Russian).