METHOD OF PROCESSING HYDROACOUSTIC NOISE-LIKE PHASE-SHIFT KEYED SIGNALS Russian patent published in 2015 - IPC H04B1/10 

FIELD: radio engineering, communication.

SUBSTANCE: method of processing hydroacoustic noise-like phase-shift keyed signals includes receiving a signal s(t), digitising the signal, obtaining y_k, pre-equalising the amplitude $${\dot{y}}_k=sign[y_k],$$ where $$sign[x]=\{\begin{array}{l}+1приx\ge 0\\ -1приx<0\end{array},$$ performing shift into the low-frequency region and determining the real component and the imaginary component of the signal (f_s is the centre frequency of the noise-like phase-shift keyed signal being processed, f_d is the sampling frequency of the signal processing system, N_s is the processing window length, which must be equal to an integer number of periods in sampling frequency readings, i.e. N_s=n·T_s·f_d, where n=1, 2, 3…), for the obtained signal $${\tilde{y}}_j=A_j+i{B}_j$$ ( $$i=\sqrt{-1}$$ - imaginary unit) using a low-pass filter, suppressing high-frequency components, is the pulse response of the filter, N_f if the length of the pulse response of the filter), decimating the sampling frequency with an interval N_s of the signal where N_s is the sampling interval, which is equal to the radio of the sampling frequency f_d of the source signal and the doubled cutoff frequency $$N_s=\frac{f_d}{2f_{cp}}=\frac{f_d}{\Delta f},$$ after which the sampling frequency of the signal becomes equal to f_d2=2f_cut=Δf, repeating signal amplitude equalisation $${\dot{y}}_j^s=sign[y_j^s]$$ and for the obtained signal $${\dot{y}}_j^{д}$$ , calculating the value of a correlation function $$Y_j={\Sigma }_{k=1}^{N_{cut}}{\dot{y}}_j^s\cdot m_k,$$ where N_cut is the duration of the processed signal in sampling frequency readings f_d2, m_k is the reference correlator signal in symbol form, calculating a threshold value $${{\rm Y}}_{thres}=\frac{n-2k}{n},$$ where n is the number of symbols in the modulating pseudorandom sequence, k is an integer defined by a given false response probability ρ_false, wherein k≤n and is selected as the greatest number for which the condition $${\rho }_{false}\approx {0.5}^k{\Sigma }_{j=k}^n{C}_n^i$$ is satisfied, where $$C_n^i$$ is the number of combinations i through $$n:C_n^i=\frac{n!}{i!(n-i)!}),$$ comparing the value of the correlation function Y_j with the threshold value Y_thres, and presence of a signal is determined when the value of the correlation function exceeds the threshold value.

EFFECT: improved noise-immunity when detecting a hydroacoustic signal in real operating conditions with low hardware computational power.