US3879729A — Moving target indicator with minimum clutter inte…

Claim 1

Independent Claim 233 words

In a moving target detection system for use on a moving platform the combination comprising: transmission means for projecting pulses of electromagnetic radiation; scanning means operating on said transmission means to vary the direction of projection of said pulses in a repetitive scan pattern covering a field extending on at least one side of the tracking line of said platform; means for receiving data signals reflected from objects within said field, each successive set of data signals representing the return from a different one of said radiation pulses; a filter circuit connected to said receiving means and having at least two stages, a first of said stages being operable to generate an intermediate signal representing the difference between two successive sets of data signals, said second of said stages operating on said intermediate signal to attenuate frequency components thereof in a band centered about 0 Hz; tuning means for varying the parameters of said filter circuit other than the parameters of said first stage to alter the overall frequency suppression characteristics of said circuit for frequencies near 0 Hz; means for operating said tuning means in synchronism with said scanning means to widen the band of said suppressed near-zero frequencies as the direction of projection of said radiation pulses deviates away from said tracking line and to narrow the band of said suppressed frequencies as said projection direction closes toward said tracking line.

Claim 2

Dependent Claim 233 words

In a moving target detection system for use on a moving platform the combination comprising: transmission means for projecting pulses of electromagnetic radiation; scanning means operating on said transmission means to vary the direction of projection of said pulses in a repetitive scan pattern covering a field extending on at least one side of the tracking line of said platform; means for receiving data signals reflected from objects within said field, each successive set of data signals representing the return from a different one of said radiation pulses; a filter circuit connected to said receiving means and having at least two stages, a first of said stages being operable to generate an intermediate signal representing the difference between two successive sets of data signals, said second of said stages operating on said intermediate signal to attenuate frequency components thereof in a band centered about 0 Hz; tuning means for varying the parameters of said filter circuit other than the parameters of said first stage to alter the overall frequency suppression characteristics of said circuit for frequencies near 0 Hz; means for operating said tuning means in synchronism with said scanning means to widen the band of said suppressed near-zero frequencies as the direction of projection of said radiation pulses deviates away from said tracking line and to narrow the band of said suppressed frequencies as said projection direction closes toward said tracking line.

Claim 3

Dependent Claim 233 words

In a moving target detection system for use on a moving platform the combination comprising: transmission means for projecting pulses of electromagnetic radiation; scanning means operating on said transmission means to vary the direction of projection of said pulses in a repetitive scan pattern covering a field extending on at least one side of the tracking line of said platform; means for receiving data signals reflected from objects within said field, each successive set of data signals representing the return from a different one of said radiation pulses; a filter circuit connected to said receiving means and having at least two stages, a first of said stages being operable to generate an intermediate signal representing the difference between two successive sets of data signals, said second of said stages operating on said intermediate signal to attenuate frequency components thereof in a band centered about 0 Hz; tuning means for varying the parameters of said filter circuit other than the parameters of said first stage to alter the overall frequency suppression characteristics of said circuit for frequencies near 0 Hz; means for operating said tuning means in synchronism with said scanning means to widen the band of said suppressed near-zero frequencies as the direction of projection of said radiation pulses deviates away from said tracking line and to narrow the band of said suppressed frequencies as said projection direction closes toward said tracking line.

Claim 4

Dependent Claim 233 words

In a moving target detection system for use on a moving platform the combination comprising: transmission means for projecting pulses of electromagnetic radiation; scanning means operating on said transmission means to vary the direction of projection of said pulses in a repetitive scan pattern covering a field extending on at least one side of the tracking line of said platform; means for receiving data signals reflected from objects within said field, each successive set of data signals representing the return from a different one of said radiation pulses; a filter circuit connected to said receiving means and having at least two stages, a first of said stages being operable to generate an intermediate signal representing the difference between two successive sets of data signals, said second of said stages operating on said intermediate signal to attenuate frequency components thereof in a band centered about 0 Hz; tuning means for varying the parameters of said filter circuit other than the parameters of said first stage to alter the overall frequency suppression characteristics of said circuit for frequencies near 0 Hz; means for operating said tuning means in synchronism with said scanning means to widen the band of said suppressed near-zero frequencies as the direction of projection of said radiation pulses deviates away from said tracking line and to narrow the band of said suppressed frequencies as said projection direction closes toward said tracking line.

Claim 5

Dependent Claim 18 words

The system set forth in claim 1 further comprising: means for displaying the output of said filter circuit.

Claim 6

Dependent Claim 43 words

The system set forth in claim 2 wherein said display means comprises a CRT device operating to display each series of outputs from said filter circuit on a radial line diverging from a center point representing the instantaneous position of said moving platform.

Claim 7

Dependent Claim 153 words

A filter circuit for use in analyzing radar return signals generated by a pulsed radar system carried on a moving platform and arranged to scan from side-to-side across a field of view extending on either side of the line of movement of said platform comprising, in combination: a first canceller circuit receiving the radar return signals and generating a signal representing the difference between the return signals received from each successive pair of radar pulses; a multiplier circuit connected to operate on the output of said first canceller; a second canceller circuit connected to operate on the output of said multiplier; and control means responsive to the angle of said scan relative to said line of movement for changing the parameters of said second canceller to alter the frequency response of said filter and for simultaneously changing the parameters of said multiplier to maintain the overall average gain of said filter substantially constant.

Claim 8

Dependent Claim 153 words

A filter circuit for use in analyzing radar return signals generated by a pulsed radar system carried on a moving platform and arranged to scan from side-to-side across a field of view extending on either side of the line of movement of said platform comprising, in combination: a first canceller circuit receiving the radar return signals and generating a signal representing the difference between the return signals received from each successive pair of radar pulses; a multiplier circuit connected to operate on the output of said first canceller; a second canceller circuit connected to operate on the output of said multiplier; and control means responsive to the angle of said scan relative to said line of movement for changing the parameters of said second canceller to alter the frequency response of said filter and for simultaneously changing the parameters of said multiplier to maintain the overall average gain of said filter substantially constant.

Claim 9

Dependent Claim 44 words

The filter circuit set forth in claim 4 wherein said first canceller comprises a single delay feed-forward canceller circuit incorporating a delay elemEnt constructed and arranged to impart to said return data a delay substantially equal to the time interval between said radar pulses.

Claim 10

Dependent Claim 45 words

The filter circuit set forth in claim 4 wherein said second canceller comprises a double delay feedback filter having means actuatable by said control means for varying the magnitude and sign of the feedback signal transmitted by at least one of the feedback delay loops.

Claim 11

Dependent Claim 114 words

The filter circuit set forth in claim 4 wherein said control means comprises: means for generating a scan signal tracking the scan angle; and means responsive to said scan signal for changing the parameters of said second canceller in a first predetermined sequence when said system is scanning away from the line of movement of said platform and for changing said parameters in an opposite sequence when said system is scanning toward said line of movement, said first predetermined sequence operating to progressively increase the range of low frequency signal components suppressed by said filter and said opposite sequence operating to progressively decrease the range of low frequency signal components suppressed by said filter.

Claim 12

Independent Claim 103 words

The method of detecting the position of moving objects from a high speed platform comprising the steps of: projecting pulsed rf energy in a scan pattern subtending an angle deviating from the tracking line of said platform; processing received signal returns in a canceller circuit having a cancellation notch centered about zero Hz and displaying the output therefrom in a PPI display format; and varying the parameters of said canceller circuit to control the width of said cancellation notch in accordance with the angle of said scan, the circuit parameters so varied being only those affecting the a.c. components of said signal returns.

Claim 13

Independent Claim 103 words

The method of detecting the position of moving objects from a high speed platform comprising the steps of: projecting pulsed rf energy in a scan pattern subtending an angle deviating from the tracking line of said platform; processing received signal returns in a canceller circuit having a cancellation notch centered about zero Hz and displaying the output therefrom in a PPI display format; and varying the parameters of said canceller circuit to control the width of said cancellation notch in accordance with the angle of said scan, the circuit parameters so varied being only those affecting the a.c. components of said signal returns.

Claim 14

Dependent Claim 37 words

The method set forth in claim 8 comprising the further step of varying the parameters of said canceller circuit in accordance with the angle of said scan to maintain a constant average power gain through the canceller.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1978-04-21	1978-10-21	1979-04-22	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1982-04-21	1982-10-21	1983-04-22	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1986-04-21	1986-10-21	1987-04-22	$7700.00	Window Closed / Lapsed

Moving target indicator with minimum clutter interference

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