Motion-compensation arrangements for MTI radars

Claim 2

In radar system of the type wherein search pulses are periodically radiated in a directional beam, a system for compensating backscattered signals for the effects of the radar's motion comprising: an array antenna for receiving the backscattered signals including first and second sub-arrays for forming similarly-shaped first and second receive beams, the lines of center of said first and second receive beams at the array being separated by a predetermined amount; first forming means coupled to said first and second sub-arrays for forming sum and difference outputs of the signals received; first optimization means coupled to receive difference signals corresponding to the difference output of said first forming means for adjusting the difference signals in phase and amplitude; first correction-forming means receiving the output of said first optimization means as an input, said first correction-forming means delaying its input signal for an interpulse period and adding the delayed input signal to the following input signal to produce a correction signal at its output; a first delay circuit coupled to receive sum signals corresponding to the sum output of said first forming means as its input, said first delay circuit delaying its input signal for an interpulse period; and a first addition circuit having a first input coupled to the output of said first correction-forming means and a second input coupled to the output of said first delay circuit, the output of said first addition circuit being a signal which in synchronized in time and phase with the signal in the sum output of said first forming means.

Claim 3

The system as recited in claim 1, further comprising a synchronizing means which comprises: a plurality of delay circuits, each of said plurality of delay circuits delaying an input signal for an interpulse period, the first of said plurality of delay circuits having its input coupled to the output of said first addition circuit; and a plurality of addition circuits, each of said plurality of addition circuits having a first input coupled to the output of one of said plurality of delay circuits and a second input coupled to the output of said first correction-forming means, said plurality of addition circuits being coupled to said plurality of delay circuits so that an input signal to the first of said plurality of delay circuits is repetitively delayed for an interpulse period and repetitively combined with the output of said first correction-forming means to form a series of signals which are synchronized in time and phase with the signal in the sum output of said first forming means.

Claim 4

The system as recited in claim 2, wherein the distance between the lines of center of said first and second receive beams at the array is related to a predetermined linear velocity of the radar and to the interpulse period, the lines of center of said first and second receive beams being parallel.

Claim 5

The system as recited in claim 1, wherein the distance between the lines of center of said first and second receive beams at the array is related to a predetermined linear velocity of the radar and to the interpulse period, the lines of center of said first and second receive beams being parallel.

Claim 6

The system as recited in claim 4, further comprising a first subtraction circuit having a first input coupled to the sum output of said first forming means and a second input coupled to the output of said first addition circuit, the output of said first subtraction circuit being a signal in which clutter has been cancelled.

Claim 7

The system as recited in claim 5 wherein said array antenna further comprises: a third sub-array for forming a third receive beam having a shape similar to that of said first and second receive beams, the distance between the lines of center of said second and said third receive beams at the array being related to a pre-determined linear velocity of the radar and to the interpulse period, the lines of center of said second and third receive beams being parallel; said system further comprising: second forming means coupled to said second and third sub-arrays for forming sum and difference outputs of the received signals; second optimization means coupled to receive difference signals corresponding to the difference output of said second forming means for adjusting the difference signals in phase and amplitude; second correction-forming means receiving the output of said second optimization means as an input, said second correction-forming means delaying an input signal for an interpulse period and adding the delayed input signal to the following input signal to produce a correction signal at its output; a second delay circuit having the sum output of said second forming means as its input, said second delay circuit delaying its input signal for an interpulse period; a second addition circuit having a first input coupled to the output of said second correction-forming means and a second input coupled to the output of said second delay circuit, the output of said second addition circuit being a signal which is synchronized in time and phase with the signal in the sum output of said second forming means; a second subtraction circuit having a first input coupled to the sum output of said second forming means and a second input coupled to the output of said second addition circuit, the output of said second subtraction circuit being a signal in which clutter has been cancelled; a third forming means coupled to receive the outputs of said first and second subtraction circuits for forming sum and difference outputs of the signals received; a third optimization means coupled to receive the difference output of said third forming means for adjusting the difference signals in phase and amplitude; a third correction-forming means receiving the output of said third optimization means as an input, said third correction-forming means delaying an input signal for an interpulse period and adding the delayed input signal to the following input signal to produce a correction signal at its output; a third delay circuit having the sum output of said third forming means as its input, said third delay circuit delaying its input signal for an interpulse period; a third addition circuit having a first input coupled to the output of said third correction-forming means and a second input coupled to the output of said third delay circuit, the output of said third addition circuit being a signal which is synchronized in time and phase with the signal in the sum output of said third forming means; and a third subtraction circuit having a first input coupled to the sum output of said third forming means and a second input coupled to the output of said third addition circuit, the output of said third subtraction circuit being a signal in which clutter has been cancelled.

Claim 8

The system as recited in claim 2, wherein the angle between the lines of center of said first and second receive beams is related to the angular velocity of the antenna and to the interpulse period, the lines of center of said first and second receive beams intersecting at the antenna.

Claim 9

The system as recited in claim 1, wherein the angle between the lines of center of said first and second receive beams is related to the angular velocity of the antenna and to the interpulse period, and wherein the lines of center of said first and second receive beams intersecting at the antenna.

Claim 10

The system as recited in claim 8, further comprising a first subtraction circuit having a first input coupled to the sum output of said first forming means and a second input coupled to the output of said first addition circuit, the output of said first subtraction circuit being a signal in which clutter has been cancelled.