Radar proximity fuse and processing method of an echo radar signal for the acquisition of distance information between a target and a doppler radar

Abstract

Radar proximity fuse ( 1 ) adapted to receive an echo radar signal (s_rx) produced by the reflection on a target (T) of a transmitted radar signal (s_tx), the transmitted signal (s_tx) comprising a sequence of M impulses coded with a phase code (p_cd). The radar proximity fuse ( 1 ) comprising: a radiofrequency analog receiving front end ( 15 ) for receiving the echo radar signal (s_rx), adapted to provide in output a baseband signal starting from the echo radar signal (s_rx) received; an analog to digital converter ( 12 ) positioned at the output of the analog receiving front end ( 15 ) adapted to sample the baseband signal to obtain in output a sequence of digital samples (d_rx); a digital processing block ( 20 ) comprising a plurality of digital processing channels (C 1 , C 2 , . . . CN) each associated to a respective range gate and each adapted to receive in input said sequence of digital samples (d_rx).

1 . Radar proximity fuse ( 1 ) adapted for receiving a radar echo signal (s_rx) produced by the reflection on a target (T) of a transmitted radar signal (s_tx), the transmitted signal (s_tx) comprising a sequence of M pulses coded with a phase code (p_cd), the radar proximity fuse ( 1 ) comprising:
 a phase code generator ( 4 ) adapted to provide said phase code (p_cd);   a radiofrequency analog receiving front end ( 15 ) for receiving the radar echo signal (s_rx), adapted to provide in output a baseband signal starting from the received radar echo signal (s_rx);   an analog to digital converter ( 12 ) placed at the output of the analog receiving front end ( 15 ) adapted for sampling the baseband signal to obtain in output a sequence of digital samples (d_rx);   a digital processing block ( 20 ) comprising a plurality of digital processing channels (C 1 , C 2 , . . . CN) configured to operate in parallel and each associated to a respective observation distance and each adapted for receiving in input said sequence of digital samples (d_rx);   wherein each digital processing channel (C 1 , C 2 , . . . CN) comprises:   a delay block ( 21 ) adapted for producing a replica of the phase code (p_cd) delayed with a respective time delay (d 1 , . . . , dN) corresponding to a respective observation distance between the fuse ( 1 ) and the target (T);   a digital multiplier ( 22 ) adapted for multiplying the sequence of digital samples with digital samples of said delayed replica to produce in output a phase decoded sequence of digital samples;   a digital information extraction block ( 23 ) adapted for processing the phase decoded sequence of digital samples to extract information correlated to the distance between the target (T) and the digital fuse ( 1 ).   
     
     
         2 . Radar proximity fuse ( 1 ) according to  claim 1 , wherein the phase code (p_cd) is dynamically programmable during the operation of said fuse ( 1 ). 
     
     
         3 . Radar proximity fuse ( 1 ) according to  claim 1 , wherein said respective time delay (d 1 , . . . , dN) is dynamically programmable during the operation of said fuse ( 1 ). 
     
     
         4 . Radar proximity fuse ( 1 ) according to  claim 1 , wherein each digital processing channel (C 1 , . . . CN) comprises an extraction block of distance information ( 23 ) comprising a sum block ( 30 ) configured to obtain in output a sequence of samples in which each sample is obtained, by means of a digital evaluation operation of a moving sum or a moving average, from a number K of samples of the respective phase decoded sequence of digital samples, in which K is an integer which represents the number of samples acquired by the analog to digital converter ( 12 ) for said sequence of M pulses of the radar echo signal (s_rx). 
     
     
         5 . Radar proximity fuse ( 1 ) according to  claim 4 , in which in the Z transform domain the sum block ( 30 ) is configured as a cascade between a perfect integrator and a mobile observation window of length equal to K samples. 
     
     
         6 . Radar proximity fuse ( 1 ) according to  claim 5 , wherein said distance information extraction block ( 23 ) comprises a band reduction digital block ( 31 ) at the output of the sum block ( 30 ). 
     
     
         7 . Radar proximity fuse ( 1 ) according to  claim 6 , wherein the band reduction block ( 27 ) comprises a sum and re-sampling block ( 32 ) configured to obtain, by means of an evaluation operation of a sum or an average, an output sample starting from each disjoint group of J* consecutive samples of the sequence of digital samples obtained in output from the sum block ( 30 ), in which J* is an integer representing a band reduction factor. 
     
     
         8 . Radar proximity fuse ( 1 ) according to  claim 6 , wherein the band reduction block ( 27 ) comprises at the output of the sum and re-sampling block ( 32 ) a low pass digital filter ( 33 ) and at the output of said low pass digital filter ( 33 ) a re-sampling block ( 34 ) to take into account of the band restriction performed by the low pass digital filter ( 33 ). 
     
     
         9 . Radar proximity fuse ( 1 ) according to  claim 1 , wherein said baseband signal has a bandwidth of the useful signal of the order of hundreds of MHz. 
     
     
         10 . Radar proximity fuse ( 1 ) according to  claim 1 , wherein said transmitted radar signal is a signal in the Ku band. 
     
     
         11 . Radar proximity fuse ( 1 ) according to  claim 1 , wherein said digital processing block ( 20 ) is adapted to directly receive in input the phase code (p_cd) produced in output by the code generator ( 4 ). 
     
     
         12 . Radar proximity fuse ( 1 ) according to  claim 1 , in which the radio frequency analog receiving front end ( 15 ) is a single channel and single-output front end, the analog to digital converter ( 12 ) is adapted to only sample amplitudes of the baseband analog signal produced in output by the radio frequency analog receiving front end ( 15 ) for providing as output digital samples representative of said amplitudes. 
     
     
         13 . Radar proximity fuse ( 1 ) according to  claim 1 , wherein said analog to digital converter is a multi-bit converter. 
     
     
         14 . Missile or rocket or weapon comprising a radar proximity fuse ( 1 ) according to  claim 1 . 
     
     
         15 . Processing method of a radar echo signal for the acquisition of distance information between a target (T) and a Doppler radar, comprising the steps of:
 receiving a radar echo signal (s_rx) produced by the reflection on a target (T) of a transmitted radar signal (s_tx), the transmitted radar signal (s_tx) comprising pulses coded with a phase code (p_cd) provided by a phase code generator ( 4 ):   processing the radar echo signal (s_rx) in the analog domain to obtain a baseband analog signal;   sampling the baseband analog signal to obtain in output a sequence of digital samples (d_rx);   performing a parallel digital processing on several channels of said sequence of digital samples (d_rx), each channel being associated to a respective observation distance; wherein said digital processing comprises for each channel the steps of:   producing a replica of the phase code (p_cd) delayed by a respective time delay corresponding to a respective observation distance between said fuse ( 1 ) and said target (T);   multiplying said sequence of digital samples with said delayed replica to produce in output a phase decoded sequence of digital samples;   processing the phase decoded sequence of digital samples to extract information correlated to the distance between the target (T) and the digital fuse ( 1 ).