Method of and device for removing range ambiguity in a pulse-doppler radar and radar including such a device

Claim 1

A device for removing range ambiguity in a pulse Doppler radar having a high repetition frequency f R (k) which varies at times T k =kΔt, where Δt is the duration of a measurement cycle, operating in the tracking mode, and including a measurement circuit which supplies the measured ambiguous range corresponding to the repetition frequency f R (k) and an estimation circuit which supplies an estimation of the ambiguity number and of the radar-to-target range as well as the standard deviation of the error in the estimated range corresponding to the repetition frequency f R (k), device wherein the repetition frequency is controlled by a servo-loop which, from the measured ambiguous range and from the estimated ambiguity number at the repetition frequency f R (k) calculates the repetition frequency f R (k+1) to be used for the following measurement cycle, such that the ambiguity number at f R (k+1) remains constant, the servo-loop having a transfer function which is of the first order and being composed of the following circuits connected in series: a first subtraction circuit in which the quantity c/4 f R (k), is subtracted from the measured ambiguous range supplied by the radar, c being the velocity of the light; an amplifier having a gain G; a second substration circuit in which the output signal of the amplifier is reduced by the variation of the radar-to-target range during the time lapse Δt, said variation being calculated by a first circuit which multiplies by the duration Δt the radial velocity of the target relative to the radar as supplied by the pulse Doppler tracking radar; a second circuit multiplying the output signal of the second subtraction circuit by a coefficient 1/[n(k)+0.5] calculated by a first calculating circuit supplied with the estimated ambiguity number n(k) corresponding to the repetition frequency f R (k); an adding circuit the first input of which receives the output signal of the second multiplying circuit and which delivers a signal equal to c/2 f R (k+1) and applied to its second input through a delay circuit having a transfer function z -1 ; a second calculating circuit supplied with the output signal c/2 f R (k+1) of the adding circuit and delivering the repetition frequency f R (k+1) which is supplied to the pulse Doppler radar for the following measurement cycle.

Claim 2

A device for removing range ambiguity in a pulse Doppler radar having a high repetition frequency f R (k) which varies at times T k =kΔt, where Δt is the duration of a measurement cycle, operating in the tracking mode, and including a measurement circuit which supplies the measured ambiguous range corresponding to the repetition frequency f R (k) and an estimation circuit which supplies an estimation of the ambiguity number and of the radar-to-target range as well as the standard deviation of the error in the estimated range corresponding to the repetition frequency f R (k), device wherein the repetition frequency is controlled by a servo-loop which, from the measured ambiguous range and from the estimated ambiguity number at the repetition frequency f R (k) calculates the repetition frequency f R (k+1) to be used for the following measurement cycle, such that the ambiguity number at f R (k+1) remains constant, the servo-loop having a transfer function which is of the first order and being composed of the following circuits connected in series: a first subtraction circuit in which the quantity c/4 f R (k), is subtracted from the measured ambiguous range supplied by the radar, c being the velocity of the light; an amplifier having a gain G; a second substration circuit in which the output signal of the amplifier is reduced by the variation of the radar-to-target range during the time lapse Δt, said variation being calculated by a first circuit which multiplies by the duration Δt the radial velocity of the target relative to the radar as supplied by the pulse Doppler tracking radar; a second circuit multiplying the output signal of the second subtraction circuit by a coefficient 1/[n(k)+0.5] calculated by a first calculating circuit supplied with the estimated ambiguity number n(k) corresponding to the repetition frequency f R (k); an adding circuit the first input of which receives the output signal of the second multiplying circuit and which delivers a signal equal to c/2 f R (k+1) and applied to its second input through a delay circuit having a transfer function z -1 ; a second calculating circuit supplied with the output signal c/2 f R (k+1) of the adding circuit and delivering the repetition frequency f R (k+1) which is supplied to the pulse Doppler radar for the following measurement cycle.