Digital doppler processor

Claim 2

In a pulsed energy type ranging system, digital doppler processing means for processing the range-gated video signals received in a given range bin over a preselected number of pulse repetition intErvals of said system to determine the power spectral density thereof for a set of selected discrete doppler frequencies corresponding to a selected bandwidth, and characterized by digital integral filter means for each discrete frequency for providing an output indicative of the cross-correlation function of the video received signal for a given range bin with each of said discrete frequencies; adjustable periodic signalling means responsive to a system trigger of said pulsed energy system for providing periodic control signals indicative of a selected discrete frequency for modulation control of the integral filter means; and adjusting means for adjusting the frequency and phase of the periodic control signals.

Claim 3

In a radar system including an intermediate frequency stage coherent receiver having a synchronous detector responsive to a source of an intermediate frequency reference, digital doppler processing means for processing signals received by said receiver and comprising digital integral filter means having an input responsively coupled to an output of said synchronous detector; voltage-controlled phase-shift means interposed between said input of said synchronous detector and said output of said intermediate frequency reference source and having a control input; and compensatory signalling means drivingly connected to said control input of said phase shift means for selectively varying at least one of the phase and frequency of the reference input to said synchronous detector.

Claim 4

In a radar system including an intermediate frequency stage coherent receiver having a synchronous detector responsive to a source of an intermediate frequency reference, digital doppler processing means for processing signals received by said receiver and comprising digital integral filter means having an input responsively coupled to an output of said synchronous detector; voltage-controlled phase-shift means interposed between said input of said synchronous detector and said output of said intermediate frequency reference source and having a control input; and compensatory signalling means drivingly connected to said control input of said phase shift means for selectively varying at least one of the phase and frequency of the reference input to said synchronous detector.

Claim 5

The device of claim 2 in which said compensatory signalling means further includes means for varying the bandpass of said digital integral filter means.

Claim 6

The device of claim 2 in which said compensatory signalling means includes means for concomitantly varying said phase of said reference source and the bandpass of said digital integral filter means in a preselected relationship.

Claim 7

In a radar system including an intermediate frequency stage coherent receiver having a synchronous detector responsive to a source of an intermediate frequency reference, digital doppler processing means for processing signals received by said receiver and comprising digital integral filter means having an input responsively coupled to an output of said synchronous detector; voltage-controlled phase-shift means interposed between said input of said synchronous detector and said output of said intermediate frequency reference source and having a control input; and compensatory signalling means drivingly connected to said control input of said phase shift means for selectively varying at least one of the phase and frequency of the reference input to said synchronous detector, said digital integral filter means including means responsive to the system trigger of said system for generating the sine and cosine functions of the argument 2 pi nf''ji/PRF where: PRF system pulse repetition frequency n a successive one of a preselected number N of system pulse repetition intervals f''ji a selected one (j) of a set of doppler frequencies for a given range bin (i), multiplying means responsive to said first mentioned means for obtaining the products of the amplitude Ani of the receiver signal associated with such range bin (i) and pulse repetition interval (n) and each of said sine and cosine functions, signal integrating means responsive to said multiplying means for generating the functions

Claim 8

In a radar system including an intermediate frequency stage coherent receiver having a synchronous detector responsive to a source of an intermediate frequency reference, digital doppler processing means for processing signals received by said receiver and comprising digital integral filter means having an input responsively coupled to an output of said synchronous detector; voltage-controlled phase-shift means interposed between said input of said synchronous detector and said output of said intermediate frequency reference source and having a control input; and compensatory signalling means drivingly connected to said control input of said phase shift means for selectively varying at least one of the phase and frequency of the reference input to said synchronous detector, said digital integral filter means including means responsive to the system trigger of said system for generating the sine and cosine functions of the argument 2 pi nf''ji/PRF where: PRF system pulse repetition frequency n a successive one of a preselected number N of system pulse repetition intervals f''ji a selected one (j) of a set of doppler frequencies for a given range bin (i), multiplying means responsive to said first mentioned means for obtaining the products of the amplitude Ani of the receiver signal associated with such range bin (i) and pulse repetition interval (n) and each of said sine and cosine functions, signal integrating means responsive to said multiplying means for generating the functions

Claim 9

The device of Claim 5 in which said compensatory signalling means includes means for varying the selected doppler frequency f''ji by a selected amount n Delta fji from a preselected starting frequency Fji in the argument 2 pi nf''ji/PRF.

Claim 10

The device of claim 5 in which said compensatory signalling means includes means for varying the selected doppler frequency f''ji from a preselected starting frequency fji associated with each range bin Ri as a function of radar platform altitude h substantially in accordance with the relationship f''ji fji Square Root Ri2 - h2/Ri.

Claim 11

The device of claim 5 in which said compensatory signalling means includes means for varying the selected doppler frequency f''ji from a preselected starting frequency fji associated with each range bin Ri as a function of radar platform altitude substantially in accordance with the relationship f''ji fji (1-(h2/2Ri2) + (h4/8Ri4)).

Claim 12

The device of claim 5 in which said compensatory signalling means includes means for varying the starting frequency fji of each range bin Ri for each integration interval N/PRF by the amount Delta fdi as a function of platform velocity V in accordance with the relationship, Delta fdi fo (Vsin2 theta /Ri, where theta is the look angle between the platform velocity vector and a boresight axis of the radar system.