Correlation arrangements

Claim 2

A radar fuze device including: a transmitter for transmitting a signal which is binary phase modulated according to a reference code; a receiver for receiving the transmitted signal reflected from a target to produce a demodulated signal representing the reference code; a multiplier for receiving the demodulated signal and a signal representing the reference code to produce a signal representing the product of the code with itself delayed by an amount dependent on the range of the target from the fuze device; and an integrator for integrating the product signal over the duration T of the reference code to produce a signal representing the autocorrelation function of the reference code; and wherein, in order to reduce the effect, on the autocorrelation, of a Doppler frequency shift of the received signal, which shift would otherwise introduce a Doppler frequency component into the signal integrated by the integrator, the device further includes, prior to the integrator, means for causing mixing of a further frequency component with the Doppler frequency component so that the signal integrated by the integrating means has a component, derived from the Doppler frequency component, of frequency f, where fT is less than 1/4.

Claim 3

A device according to claim 1, wherein the means for causing mixing comprise a source of the further component and a mixer having inputs connected to the source and to the multiplier, and an output connected to the integrator.

Claim 4

A radar fuze device including a transmitter for transmitting a signal which is binary phase modulated according to a reference code; a receiver for receiving the transmitted signal reflected from a target to produce a demodulated signal representing the reference code; and a multiplier for receiving the demodulated signal and a signal representing the reference code to produce a signal representing the product of the code with itself delayed by an amount dependent on the range of the target from the fuze device, and wherein a plurality of signal paths are commonly connected to the multiplier, each path including an integrator for integrating over a time T substantially equal to the duration of the reference code to produce a signal representing the autocorrelation function of the reference code, and in order to reduce the effect, on the autocorrelation, of a Doppler frequency shift of the received signal, which shift would otherwise introduce a Doppler frequency component into the signala integrated by the integrator, means, provided in the path prior to the integrator, for causing mixing of a further frequency component with the Doppler frequency component so that the signal integrated by the integrating means has a component, derived from the Doppler frequency component of frequency f, where fT is less than 1/4.

Claim 5

A radar fuze device including a transmitter for transmitting a signal which is binary phase modulated according to a reference code; a receiver for receiving the transmitted signal reflected from a target to produce a demodulated signal representing the reference code; and a multiplier for receiving the demodulated signal and a signal representing the reference code to produce a signal representing the product of the code with itself delayed by an amount dependent on the range of the target from the fuze device, and wherein a plurality of signal paths are commonly connected to the multiplier, each path including an integrator for integrating over a time T substantially equal to the duration of the reference code to produce a signal representing the autocorrelation function of the reference code, and in order to reduce the effect, on the autocorrelation, of a Doppler frequency shift of the received signal, which shift would otherwise introduce a Doppler frequency component into the signala integrated by the integrator, means, provided in the path prior to the integrator, for causing mixing of a further frequency component with the Doppler frequency component so that the signal integrated by the integrating means has a component, derived from the Doppler frequency component of frequency f, where fT is less than 1/4.

Claim 6

An arrangement according to claim 3, wherein each path includes filter means provided in the path prior to the mixing means, for selecting a respective predetermined frequency range.

Claim 7

An arrangement according to claim 3 or 4, comprising a further signal path, connected in parallel to the said paths to the combining means, the further path comprising an integrator for integrating over the time T.

Claim 8

An arrangement according to claim 5, wherein the further path also comprises a filter means for selecting a predetermined frequency range.