RADAR FOR AUTOMATIC TERRAIN AVOIDANCE

• US 3,815,132 A
• Filed: 06/03/1960
• Issued: 06/04/1974
• Est. Priority Date: 06/03/1960
• Status: Expired due to Term

• Current Assignee: Jerome M. Page, Robert O. Case Jr
• Original Assignee: Jerome M. Page, Robert O. Case Jr
• Inventors: Case, Robert O. Jr., Page, Jerome M.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US04/033,860
• Time in Patent Office: 5,114 Days
• Field of Search: 343/16,7,5,7TA,16M
• US Class Current: 342/65
• CPC Class Codes: G01S 13/935 for terrain-avoidance

Abstract

In an airborne radar having a forward looking antenna directed toward the ground at a relatively small depression angle, MEANS INCLUDING SAID ANTENNA FOR GENERATING FIRST AND SECOND SIGNALS INDICATIVE OF THE RANGE AND DIRECTION RESPECTIVELY OF TERRAIN LYING WITHIN THE BEAMWIDTH OF THE ANTENNA; MEANS RESPONSIVE TO SAID RADAR FOR GENERATING A REFERENCE SIGNAL INDICATIVE OF A PRESELECTED CLEARANCE DISTANCE, Ho, divided by said range R; signal combining means responsive to said second signal and said reference signal for providing a warning signal indicative of the difference therebetween.

Claims

1. In an airborne radar having a forward looking antenna directed toward the ground at a relatively small depression angle, means including said antenna for generating first and second signals indicative of the range and direction respectively of terrain lying within the beamwidth of the antenna;

means responsive to said radar for generating a reference signal indicative of a preselected clearance distance, Ho, divided by said range, R;

signal combining means responsive to said second signal and said reference signal for providing a warning signal indicative of the difference therebetween.

2. In an airborne radar having a forward looking antenna directed toward the ground at a relatively small depression angle, means including said antenna for generating first and second signals indicative of the range and direction respectively of terrain lying within the beamwidth of the antenna;

means responsive to said radar for generating a reference signal indicative of a preselected clearance distance, Ho, divided by said range, R;

signal summing means responsive to said first and second mentioned means; and

peak detection means responsive to said signal summing means for providing a maximum value terrain warning signal indicative of a required maneuver angle, C.

3. The device of claim 2 in which said second mentioned means is comprised of a signal bias generator for generating a signal indicative of a preselected clearance distance, Ho;

and a signal divider responsive to said range signals and to said bias generator for providing a signal indicative of the ratio of said preselected clearance distance divided by said range.

4. The device of claim 2 in which is further provided means responsive to said radar for gating on said peak detector during a preselected range interval, said gating means comprising a first gate for gating on said peak detector in response to range signals indicative of a range greater than a preselected minimum range, and a second gate for gating off said peak detector in response to range signals indicative of a range greater than a preselected maximum range.

5. The device of claim 2 in which is further provided a signal utilization device, means for coupling said peak detector to said signal utilization device, an altimeter, and switching means responsive to said altimeter means for overriding the coupling of said peak detector to said utilization device.

6. The device of claim 2 in which is further provided:

signal utilization means, altimeter means for providing a signal indicative of an altitude less than a preselected clearance distance. first coupling means responsive to said radar for coupling the output of said peak-detector and said signal utilization device during a received output from said radar, and second coupling means responsive to said altimeter means for overriding said first coupling means to connect said altimeter means to said signal utilization means during the interval when said altimeter means provides a signal indicative of an altitude less than a preselected clearance distance.

7. Vehicle borne monopulse radar means including an antenna having a multilobe radiation pattern directed towards points on the ground along a boresight axis depressed by a relatively small angle from a selected reference direction and having receiver means for providing an error signal representative of the displacement angle between said boresight axis and the direction to a reflecting point on the ground, means for generating a reference signal representative of the ratio of a predetermined clearance distance to range of said reflecting points, means for generating a depression signal representative of the depression angle of said boresight axis, summing means responsive to said signals for producing a terrain angle signal representative of the difference between said reference signal and said Depression and error signals, a peak detector responsive to said terrain angle signal, and output means responsive to said peak detector.

8. Vehicle borne monopulse radar means including an antenna having a multilobe radiation pattern directed towards points on the ground along a boresight axis depressed by a relatively small angle from a selected reference direction and having receiver means for providing an error signal representative of the displacement angle between said boresight axis and the direction to a reflecting point on the ground, means for generating a reference signal representative of the ratio of a predetermined clearance distance to range of said reflecting points, means for generating a depression signal representative of the depression angle of said boresight axis, means for generating an angle of attack signal representative of the angle of attack of said aircraft, summing means responsive to said signals for producing a terrain angle signal representative of the difference between said reference signal and said depression, error and angle of attack signals, a peak detector responsive to said terrain angle signal, maximum and minimum range generators, a gate generator responsive to said range generators, an enabling connection from said gate generator to said peak detector and to said receiving means, and output means responsive to said peak detector.

9. In combination with an aircraft, an antenna on said aircraft having a boresight axis and a pair of radiation lobes extending on either side of said axis, said axis being depressed through a small angle relative to a reference line on said aircraft, microwave means for additively and subtractively combining energy received by said antenna to produce sum and error signals respectively, sum and error receiver channels respectively responsive to said sum and error signals, instantaneous automatic gain control means responsive to signals in said sum channel for controlling the gain of both said channels, a phase detector having inputs from said sum and error receiver channels and having an output indicative of the angle between said boresight axis and reflecting points on the ground within said radiation lobes, a range generator, a clearance distance reference generator, a divider having inputs from said range and reference generators and having an output indicative of the ratio of clearance distance to range, a depression angle generator having an output indicative of the depression angle of said boresight axis, a summing device having inputs from said depression angle generator and said phase detector and said divider and having an output indicative of the difference between said depression angle and the sum of said divider and phase detector outputs, a peak detector having an input from said summing device, maximum and minimum range generators, a first comparator having inputs from said range generator and said minimum range generator, a second comparator having inputs from said range generator and said maximum range generator, a gate generator having a gate initiating input from said first comparator and a gate terminating input from said second compartor, an enabling gating connection from said gate generator to said receiver channels and to said peak detector, and an aircraft elevation control device having an input from said peak detector.