Variable PRF target tracking radar

Claim 3

The method of claim 1 wherein said step of reducing spurious signals in the target reflected high PRF signal below a predetermined level includes the step of mixing said target reflected high PRF signal with a first frequency to provide an intermediate frequency above 300 MHz.

Claim 4

The method of claim 1 wherein said step of reducing spurious signals in the target reflected high PRF signal below a predetermined level includes the step of shaping the rise and fall time of the edges of said predetermined receive time interval.

Claim 5

The method of claim 1 wherein said step of comparing the arrival of one of said pulses of a target reflected high PRF signal includes the steps of: generating a first signal corresponding to the portion of the reflected signal received during a first part of said predetermined receive time interval, generating a second signal corresponding to the portion of the reflected signal received during a second part of said predetermined receive time interval, and combining arithmetically said first and second signals to form said early/late signal.

Claim 6

The method of claim 1 further including the steps of: generating a target verification signal from said pulses of said target reflected high PRF signal received during said predetermined receive time intervals indicative of the absence of said pulses of said target reflected high PRF signal during said predetermined receive time intervals, calculating a first signal indicative of a change in PRF based upon target range and a constant L, said constant L represents the number of equal time shifts to be made in reacquiring the target, and changing the PRF of the transmitted signal in accordance with said first signal at times when said target verification signal exceeds a predetermined value to reacquire said target.

Claim 7

The method of claim 1 further including the steps of: comparing said new high PRF signal with a predetermined upper PRF limit, and changing said new high PRF signal below said upper PRF limit at times when said new high PRF signal exceeds said upper PRF limit.

Claim 8

The method of claim 1 further including the steps of: comparing said new high PRF signal with a predetermined lower PRF limit, and changing said new high PRF signal above said lower PRF limit at times when said new high PRF signal is less than said lower PRF limit.

Claim 9

A pulse doppler radar for tracking a moving target wherein initial target range and doppler frequency information is provided, comprising: means for generating a high PRF signal, said signal being constituted by a series of time spaced pulses, means for transmitting said high PRF signal, means for repeatedly receiving at least a portion of one of said pulses of a target reflected high PRF signal during a predetermined receive time interval between said time-spaced pulses of said high PRF signal being transmitted, means for reducing spurious signals in the target reflected high PRF signal below a predetermined level which are incidentally generated by modulation of the main beam clutter, said modulation results from receiving during said predetermined receive time intervals, means for tracking the doppler frequency of said target reflected signals to provide a signal indicative of target velocity, means for generating a target range signal indicative of the present target range utilizing said initial range, target velocity signal and the time lapsed from the time of the initial range measurement, means for repeatedly comparing the arrival of one of said pulses of a target reflected high PRF signal with said predetermined receive time interval to provide an early/late signal indicative of whether said pulse of a target reflected high PRF signal is centered with respect to said predetermined receive time interval, means for varying the PRF of said high PRF signal by calculating a new PRF based upon said target range, target velocity and early/late signal to align said pulses of said target reflected signal towards the center of said predetermined receive time intervals.

Claim 10

A pulse doppler radar for tracking a moving target wherein initial target range and doppler frequency information is provided, comprising: means for generating a high PRF signal, said signal being constituted by a series of time spaced pulses, means for transmitting said high PRF signal, means for repeatedly receiving at least a portion of one of said pulses of a target reflected high PRF signal during a predetermined receive time interval between said time-spaced pulses of said high PRF signal being transmitted, means for reducing spurious signals in the target reflected high PRF signal below a predetermined level which are incidentally generated by modulation of the main beam clutter, said modulation results from receiving during said predetermined receive time intervals, means for tracking the doppler frequency of said target reflected signals to provide a signal indicative of target velocity, means for generating a target range signal indicative of the present target range utilizing said initial range, target velocity signal and the time lapsed from the time of the initial range measurement, means for repeatedly comparing the arrival of one of said pulses of a target reflected high PRF signal with said predetermined receive time interval to provide an early/late signal indicative of whether said pulse of a target reflected high PRF signal is centered with respect to said predetermined receive time interval, means for varying the PRF of said high PRF signal by calculating a new PRF based upon said target range, target velocity and early/late signal to align said pulses of said target reflected signal towards the center of said predetermined receive time intervals.

Claim 11

The pulse doppler radar of claim 8 wherein said means for reducing spurious signals in the target reflected high PRF signal below a predetermined level includes means for mixing said target reflected high PRF signal with a first frequency to provide an intermediate frequency above 300 MHz.

Claim 12

The pulse doppler radar of claim 8 wherein said means for reducing spurious signals in the target reflected high PRF signal below a predetermined level includes means for shaping the rise and fall time of the edges of said predetermined receive time interval.

Claim 13

The pulse doppler radar of claim 8 wherein said means for comparing the arrival of one of said pulses of a target reflected high PRF signal includes: means for generating a first signal corresponding to the portion of the reflected signal received during a first part of said predetermined receive time interval, and means for generating a second signal corresponding to the portion of the reflected signal received during a second part of the said predetermined receive time interval, and means for combining arithmetically said first and second signals to form said early/late signal.

Claim 14

The pulse doppler radar of claim 8 further including: means for generating a target verification signal from said pulses of said target reflected high PRF signal received during said predetermined receive time intervals indicative of the absence of said pulses of said target reflected high PRF signal during said predetermined receive time interval, means for calculating a first signal indicative of a change in PRF based upon target range and a constant L, said constant L represents the number of equal time shifts to be made in reacquiring the target, and means for changing the PRF of the transmitted signal in accordance with said first signal at times when said target verification signal exceeds a predetermined value to reacquire said target.

Claim 15

The pulse doppler radar of claim 8 further including: means for comparing said new high PRF signal with a predetermined upper PRF limit, and means for changing said new high PRF signal below said upper PRF limit at times when said new high PRF signal exceeds said upper PRF limit.

Claim 16

The pulse doppler radar of claim 8 further including: means for comparing said new high PRF signal with a predetermined lower PRF limit, and means for changing said new high PRF signal above said lower PRF limit at times when said new high PRF signal is less than said lower PRF limit.