Terrain-following radar system

Claim 2

In a terrain-following directionally ranging system for airborne use, spatial filter means for detecting a discrete obstacle projecting amid a general clutter background and comprising first means responsive to a sampled received signal output of said system for providing a time-averaged sampled bipolar direction angle signal, averaged over a preselected (n) number of successive system pulse repetition intervals, second means responsive to said sampled received signal output for providing a signal indicative of any substantially common value occurring for at least M samples of said sampled signal over said n successive pulse repetition intervals, and logic means responsive to said first and second means for gating-on the larger of said time averaged sampled signal and said substantially common value as a warning signal of interest.

Claim 3

The device of claim 1 in which there is further included bipolar scannable threshold means for providing a reference value signal, the value of which is progressively varied over the interval of each pulse repetition interval from a maximum value through null to a minimum value, said first means being responsive thereto for thresholding of said sampled signal output.

Claim 4

The device of claim 2 in which said logic means is responsive to the coincidence of that M state of said second means and a state of said reference value exceeding said time averaged value for gating-on the coincident value of said reference value signal as a warning signal of interest.

Claim 5

The device of claim 2 in which said logic means is further responsive to said threshold means for normally gating-on said time-averaged sampled signal unless either said reference value signal exceeds said time average signal or said M state of said second means occurs.

Claim 6

In a terrain-following directionally ranging system adapted for airborne use, logic apparatus for improved reliable signalling of the existence of an on-boresight terrain obstacle of interest, comprising first two-state signalling means responsive to a receiver signal output of said system for indicating whether Said receiver signal output is of at least a preselected threshold level; second two-state signalling means responsive to a target direction indicating signal output of said system for indicating whether an on-boresight target condition exists; third two-state signalling means responsive to a system trigger of said system for indicating a range-time interval corresponding to that within preselected minimum and maximum range distances; and coincidence gating means responsive to an output of each of said three two-state signalling means for indicating a coincidence of the output states of said two-state signalling means.

Claim 7

In a terrain-following directionally ranging system adapted for airborne use, logic apparatus for improved reliable signalling of the existence of an on-boresight terrain obstacle of interest, comprising first two-state signalling means responsive to a receiver signal output of said system for indicating whether Said receiver signal output is of at least a preselected threshold level; second two-state signalling means responsive to a target direction indicating signal output of said system for indicating whether an on-boresight target condition exists; third two-state signalling means responsive to a system trigger of said system for indicating a range-time interval corresponding to that within preselected minimum and maximum range distances; and coincidence gating means responsive to an output of each of said three two-state signalling means for indicating a coincidence of the output states of said two-state signalling means.

Claim 8

The device of claim 5 in which said second means for indicating whether an on-boresight target condition exists includes means for disabling said coincidence gating means in the presence of an off-boresight target condition resembling an on-boresight target condition.

Claim 9

The device of claim 5 in which said ranging system comprises a monopulse system of the sum and difference type and in which said second two-state signalling means comprises fourth signalling means responsive to a monopulse difference channel output of said ranging system for providing an output signal indicative of the occurrence of a difference channel null output; and fifth signalling means responsive to said monopulse difference channel output and to a monopulse sum channel output of said system for providing an output signal indicative of the occurrence of a monopulse difference channel output magnitude less than that of said monopulse sum channel output, the output signals of said fourth and fifth signalling means being fed to respective inputs of said coincidence gating means.

Claim 10

In a terrain-following radar including means for detecting a terrain profile, gamma (R), spatial filtering means for providing increased discrimination of discrete terrain obstacles from general terrain clutter and comprising sample-and-hold means for sampling the terrain profile direction signal at a selected range (Ri) over a preselected number (n) of successive pulse repetition intervals, signal combining means responsive to said preselected number of successive samples at said selected range for providing an output corresponding to the pulse-to-pulse time-averaged history of the magnitudes thereof, scannable threshold means for providing a threshold signal indicative of a threshold value, difference detector means responsively coupled to said threshold means and said signal combining means for providing a signal indicative of the sense of the magnitude difference between said outputs of said threshold means and said signal combining means, two-state comparator means responsively coupled to said threshold means and said sample and hold means for providing a first-state output indicative of those terrain profile samples exceeding said threshold signal, two-state logic means responsive to said comparator means for providing a first-state output indicative of the occurrence of at least a preselected number (M) of said n samples which exceed said threshold signal, coincidence gate means responsive to said difference detector means and to said threshold means for providing a first-state logic output indicative of the coincidence of both the non-occurrence of a terrain profile sample exceeding said threshold value and the non-occurrence of said first-state of said logic means, and double-throw switch means having a control input responsive to the output of said coincidence gate means for alternatively selecting a predetermined one of said outputs of said signal combining means and said logic means in response to a preselected output state of said coincidence gate means.

Claim 11

In a terrain-following radar including means for detecting a terrain profile, gamma (R), spatial filtering means for providing increased discrimination of discrete terrain obstacles from general terrain clutter and comprising sample-and-hold means for sampling the terrain profile direction signal at a selected range (Ri) over a preselected number (n) of successive pulse repetition intervals, signal combining means responsive to said preselected number of successive samples at said selected range for providing an output corresponding to the pulse-to-pulse time-averaged history of the magnitudes thereof, scannable threshold means for providing a threshold signal indicative of a threshold value, difference detector means responsively coupled to said threshold means and said signal combining means for providing a signal indicative of the sense of the magnitude difference between said outputs of said threshold means and said signal combining means, two-state comparator means responsively coupled to said threshold means and said sample and hold means for providing a first-state output indicative of those terrain profile samples exceeding said threshold signal, two-state logic means responsive to said comparator means for providing a first-state output indicative of the occurrence of at least a preselected number (M) of said n samples which exceed said threshold signal, coincidence gate means responsive to said difference detector means and to said threshold means for providing a first-state logic output indicative of the coincidence of both the non-occurrence of a terrain profile sample exceeding said threshold value and the non-occurrence of said first-state of said logic means, and double-throw switch means having a control input responsive to the output of said coincidence gate means for alternatively selecting a predetermined one of said outputs of said signal combining means and said logic means in response to a preselected output state of said coincidence gate means.

Claim 12

In a terrain-following radar including means for detecting a terrain profile, gamma (R), spatial filtering means for providing increased discrimination of discrete terrain obstacles for general terrain clutter and comprising meaNs responsive to samples of the terrain profile direction signal gamma (R) at a selected range (Ri) over a preselected number (n) of successive pulse repetition intervals for providing a signal indicative of the sense of the magnitude difference between a time average of said samples and a selected threshold value, two-state comparator means responsive to said threshold value and said time-averaged n samples for providing a first-state output indicative of those terrain profile samples exceeding said threshold value, logic means responsive to said comparator means for providing a first-state output indicative of the occurrence of at least a preselected number (M) of said time-averaged n samples which exceed said threshold value, coincidence gate means for providing a first-state logic output indicative of the coincidence of both the non-occurrence of a terrain profile sample exceeding said threshold value and the non-occurrence of said first-state of said logic means, and double-throw switch means having a control input responsive to the coincidence of both the non-occurrence of a terrain profile time-averaged sample exceeding said threshold value and the non-occurrence of said first-state of said logic means for alternatively selecting a predetermined one of said time-averaged samples and the output of said logic means in response to a preselected output state of said coincidence gate means.

Claim 13

In a terrain-following radar including means for detecting a terrain profile, gamma (R), spatial filtering means for providing increased discrimination of discrete terrain obstacles for general terrain clutter and comprising meaNs responsive to samples of the terrain profile direction signal gamma (R) at a selected range (Ri) over a preselected number (n) of successive pulse repetition intervals for providing a signal indicative of the sense of the magnitude difference between a time average of said samples and a selected threshold value, two-state comparator means responsive to said threshold value and said time-averaged n samples for providing a first-state output indicative of those terrain profile samples exceeding said threshold value, logic means responsive to said comparator means for providing a first-state output indicative of the occurrence of at least a preselected number (M) of said time-averaged n samples which exceed said threshold value, coincidence gate means for providing a first-state logic output indicative of the coincidence of both the non-occurrence of a terrain profile sample exceeding said threshold value and the non-occurrence of said first-state of said logic means, and double-throw switch means having a control input responsive to the coincidence of both the non-occurrence of a terrain profile time-averaged sample exceeding said threshold value and the non-occurrence of said first-state of said logic means for alternatively selecting a predetermined one of said time-averaged samples and the output of said logic means in response to a preselected output state of said coincidence gate means.

Claim 14

In a terrain-following radar including means for detecting a terrain profile, gamma (R), spatial filtering means for providing increased discrimination of discrete terrain obstacles from general terrain clutter and comprising means responsive to samples of the terrain profile direction signal gamma (R) at a selected range (Ri) over a preselected number (n) of successive pulse repetition intervals for providing a signal indicative of the sense of the magnitude difference between a time average of said samples and a selected threshold value, logic means for providing a first-state output indicative of the occurrence of at least a preselected number (M) of said time-averaged n samples which exceed said threshold value, coincidence gate means for providing a first-state logic output indicative of the coincidence of both the non-occurrence of a terrain profile sample exceeding said threshold value and the non-occurrence of said first-state of said logic means, and double-throw switch means having a control input responsive to the coincidence of both the non-occurrence of a terrain profile time-averaged sample exceeding said threshold value and the non-occurrence of said first-state of said logic means for alternatively selecting a predetermined one of said time-averaged sample and said output of said logic means in response to a preselected output state of said coincidence gate means.

Claim 15

In a terrain-following radar including means for detecting a terrain profile, gamma (R), spatial filtering means for providing increased discrimination of discrete terrain obstacles from general terrain clutter and comprising means responsive to samples of the terrain profile direction signal gamma (R) at a selected range (Ri) over a preselected number (n) of successive pulse repetition intervals for providing a signal indicative of the sense of the magnitude difference between a time average of said samples and a selected threshold value, logic means for providing a first-state output indicative of the occurrence of at least a preselected number (M) of said time-averaged n samples which exceed said threshold value, coincidence gate means for providing a first-state logic output indicative of the coincidence of both the non-occurrence of a terrain profile sample exceeding said threshold value and the non-occurrence of said first-state of said logic means, and double-throw switch means having a control input responsive to the coincidence of both the non-occurrence of a terrain profile time-averaged sample exceeding said threshold value and the non-occurrence of said first-state of said logic means for alternatively selecting a predetermined one of said time-averaged sample and said output of said logic means in response to a preselected output state of said coincidence gate means.

Claim 16

The device of claim 10 in which said terrain-following radar is of the frequency agility type transmitting a different one of n discrete frequencies upon each of n successive pulse repetition intervals, corresponding to the period over which said samples are time-averaged.

Claim 17

The device of claim 10 in which said selected threshold value is a progressively varying one over a pulse repetition interval, varying from a maximum positive value through a null to a maximum negative value.

Claim 18

The device of claim 10 in which said terrain-following radar is of the frequency agility type transmitting a different one of n discrete frequencies upon each of n successive pulse repetition intervals, corresponding to the period over which said samples are time-averaged and in which said selected threshold value is a progressively varying one over a pulse repetition interval, varying from a maximum positive value through a null to a maximum negative value.

Claim 19

The device of claim 10 in which said double-throw switch means selects said time-averaged sample in response to an output state of said coincidence of bOth non-occurrence of a terrain time-averaged sample exceeding said threshold value and the non-occurrence of at least a preselected number (M) of said n time-averaged samples.

Claim 20

In a terrain-following radar including means for detecting a terrain profile, gamma (R), spatial filtering means for providing increased discrimination of discrete terrain obstacles from general terrain clutter and comprising means responsive to samples of the terrain profile direction signal gamma (R) at a selected range (Ri) over a preselected number (n) of successive pulse repetition intervals for providing a signal indicative of the sense of the magnitude difference between a time average of said samples and a selected threshold value, logic means for providing a first-state output indicative of the occurrence of at least a preselected number (M) of said time-averaged n samples which exceed said threshold value, and alternative output gating means having a two-state logic control input responsive in a first state to the coincidence of both the non-occurrence of a time-averaged sample exceeding said threshold value and the non-occurrence of at least a preselected number (M) of time-averaged samples of said n successive time-averaged samples which exceed said threshold value for gating-on said time-averaged sample, said threshold value being alternatively gated-out in an alternative second state of said logic control input.

Claim 21

In a terrain-following radar including means for detecting a terrain profile, gamma (R), spatial filtering means for providing increased discrimination of discrete terrain obstacles from general terrain clutter and comprising means responsive to samples of the terrain profile direction signal gamma (R) at a selected range (Ri) over a preselected number (n) of successive pulse repetition intervals for providing a signal indicative of the sense of the magnitude difference between a time average of said samples and a selected threshold value, logic means for providing a first-state output indicative of the occurrence of at least a preselected number (M) of said time-averaged n samples which exceed said threshold value, and alternative output gating means having a two-state logic control input responsive in a first state to the coincidence of both the non-occurrence of a time-averaged sample exceeding said threshold value and the non-occurrence of at least a preselected number (M) of time-averaged samples of said n successive time-averaged samples which exceed said threshold value for gating-on said time-averaged sample, said threshold value being alternatively gated-out in an alternative second state of said logic control input.