Autocorrelation sidelobe suppression device for a continuous periodic phase-coded signal

Claim 2

Autocorrelation apparatus for a psuedo-random coded radar employing means for generating a continuous periodic phase code whose code sequence is such that the sum itself and the same code shifted one bit has a uniform zero amplitude between main correlation peaks, comprising: first means for obtaining the autocorrelation signal from said phase-code as a first autocorrelation function; second means for obtaining the autocorrelation signal from said phase-code shifted one bit as a second autocorrelation function; and third means for summing said first and second autocorrelation functions to provide a third autocorrelation function in which sidelobes are suppressed between main autocorrelation peaks.

Claim 3

Apparatus according to claim 1 in which said means for generating said phase code is arranged to generate a periodic signal s'(t) formed of a series of subpulses each of duration T, and including means for generating said periodic signal s'(t) by multiplying alternately by +1 and -1 the successive subpulses of a periodic signal s(t) generated over the period by a "cyclically almost perfect code" of n bits of level C i where i=1 to n.

Claim 4

An autocorrelator with sidelobe suppression, comprising: in a pseudo-random coded CW radar system, autocorrelation apparatus which includes processing means for generating a pseudo-random code and for autocorrelating a coded signal s'(t), said processing means including a conventional receiver matched to a period of said s'(t) signal, the combination comprising: first means for delaying the autocorrelated signal by a time T corresponding to the duration of one code bit to provide a delayed autocorrelated signal; and second means comprising a summer for providing the sum of said autocorrelated and delayed autocorrelated signals, thereby to provide an autocorrelation function free of sidelobes between successive correlation peaks.

Claim 5

An autocorrelator with sidelobe suppression, comprising: in a pseudo-random coded CW radar system, autocorrelation apparatus which includes processing means for generating a pseudo-random code and for autocorrelating a coded signal s'(t), said processing means including a conventional receiver matched to a period of said s'(t) signal, the combination comprising: first means for delaying the autocorrelated signal by a time T corresponding to the duration of one code bit to provide a delayed autocorrelated signal; and second means comprising a summer for providing the sum of said autocorrelated and delayed autocorrelated signals, thereby to provide an autocorrelation function free of sidelobes between successive correlation peaks.

Claim 6

An autocorrelation sidelobe suppression device according to claim 2, usable for the case in which n is even, containing a filter matched to the "subpulse", receiving the reflected signal r'(t) corresponding to the transmitted signal s'(t), followed by (n-1) identical delay lines each introducing a delay T, n multipliers placed at the output of the said filter and of the said delay lines and respectively carrying out the multiplication of the n output signals by n coefficients C" i (i=1 to n), and an adder S1, characterized in that the coefficients C" i are related to the coefficients C i , conjugates of C i , by the equations: C".sub.1 =C.sub.1 -C.sub.n C".sub.i =(-1).sup.i-1 (C.sub.i -C.sub.i-1) for i≠1.

Claim 7

A device according to claim 4, usable for the case in which n is odd, characterized in that it also contains another adder S4 receiving, on the one hand, the output signal of the adder S1 delayed by a time nT by means of a delay line and, on the other hand, the output signal of the said adder S1 multiplied by -1 by means of a multiplier.

Claim 8

An autocorrelation sidelobe suppression device according to claim 2, containing a multiplier receiving the reflected signal r'(t) and followed by a gate and an integrator, characterized in that: the said multiplier also receives the two added signals s'(t) and s'(t-T); the said gate conducts during a time nT when n is even and during a time 2nT when n is odd.

Claim 9

A device according to claim 2 further defined in that means are included for applying said level of C i with a value of +1.

Claim 10

A device according to claim 2 further defined in that means are included for applying said level of C i with a value of -1.

Claim 11

A device according to claim 4 further defined in that means are included for applying said level of C i with a value of +1.

Claim 12

A device according to claim 4 further defined in that means are included for applying said level of C i with a value of -1.

Claim 13

A device according to claim 6 further defined in that means are included for applying said level of C i with a value of +1.

Claim 14

A device according to claim 6 further defined in that means are included for applying said level of C i with a value of -1.