Patent RU-2552534-C1 (RU)
Inventor: BEZRUCHKO FEDOR VLADIMIROVICH
IPC: H04B1/10
Filed: 2014-03-26
Granted: 2015-06-10
Abstract: 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            y   ˙     k     =   s   i   g   n   [     y   k     ]   ,         
 where        s   i   g   n   [   x   ]   =     {         +   1       п   р   и       x   ≥   0           −   1       п   р   и       x   <   0           ,         
 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            y   ˜     j     =     A   j     +   i     B   j           
 (       i   =       −   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     =         f   d         2     f     c   p           =         f   d         Δ   f       ,         
 after which the sampling frequency of the signal becomes equal to f d2 =2f cut =Δf, repeating signal amplitude equalisation            y   ˙     j   s     =   s   i   g   n   [     y   j   s     ]         
 and for the obtained signal            y   ˙     j   д           
, calculating the value of a correlation function          Y   j     =     Σ     k   =   1         N     c   u   t               y   ˙     j   s     ⋅     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          Υ     t   h   r   e   s       =       n   −   2   k     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          ρ     f   a   l   s   e       ≈       0.5     k       Σ     j   =   k     n       C   n   i           
 is satisfied, where          C   n   i           
 is the number of combinations i through        n   :     C   n   i     =       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.