SIGNAL-CORRELATING APPARATUS FOR IMPROVING THE ANGULAR RESOLUTION OF A DIRECTIONALLY RANGING SYSTEM

• US 3,710,384 A
• Filed: 11/17/1969
• Issued: 01/09/1973
• Est. Priority Date: 11/17/1969
• Status: Expired due to Term

• Current Assignee: William D. Ashcraft
• Original Assignee: William D. Ashcraft
• Inventors: Ashcraft, William D.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US04/877,311
• Time in Patent Office: 1,149 Days
• Field of Search: 343/7A,16R
• US Class Current: 342/94
• CPC Class Codes: G01S 7/2806 Employing storage or delay devices which preserve the pulse form of the echo signal, e.g. for comparing and combining echoes received during different periods

Abstract

Means for improving the azimuth resolution of an azimuthally scanning ground-mapping radar. The sampled-and-held video for a given range bin is processed by a correlation filter having a preselected impulse response and then differentiated. A negativegoing zero level of the differentiated signal is employed as indicative of the scan time or angular position of the centroid of a sensed target to within less than the angular beamwidth of the antenna.

Claims

1. A method for improving the indicated directional resolution of a range-gated directionally scanned directionally ranging system having received signal utilization means and comprising the steps of subjecting a range-time gated sample-and-held electrical output of said system, indicative of a preselected target range, to a filter circuit having a preselected impulse function corresponding to an analog of a normalized replica of the response of said system to a scanned point source target;

and responsively coupling said signal utilization means to the output of said filter circuit only during an interval of a rate of change of said output of said filter indicative of a maxima thereof.

2. In a data pattern sampling system having output signal utilization means, correlation means for improving the indicated directional resolution of said system and comprising signal shaping means responsive to a range-gated output of said system and having an impulse response corresponding to an analog of a normalized replica of the response of said sampling system to a point source data element;

and gating means responsively coupled to said signal shaping means for coupling an input of said signal utilization means to said system only during a preselected change in sense of the amplitude rate of response of said signal shaping means corresponding to a maximum correlation of said system response with said data element.

3. Means for improving the angular resolution of a directionally scannable directional sensor having a given beamwidth, comprising correlating electrical filter means adapted to be responsively coupled to an electrical output of said sensor and having an impulse response funcTion corresponding to an analog of a normalized replica of the scanned sensor response to a point source target;

and means responsively coupled to said correlating filter for gating-on an output thereof only during a preselected change in sense of the amplitude rate of response of said filter.

4. The device of claim 3 in which said filter means comprises range-time-gated sample-and-hold means adapted to be responsive to an electrical output of said sensor which is indicative of a preselected target range;

and a filter circuit responsive to said sample-and-hold means and having a preselected impulse function.

5. The device of claim 3 in which said means for gating-on comprises rate-signalling means responsive to an output of said filter means for providing a signal indicative of the rate of change of said output of said filter means;

gate control means coupled to an output of said rate-signalling means and responsive to a preselected change of sense of said rate of change signal for generating a gate control signal; and

signal gate means coupled to said output of said filter and having a gate control input responsive to said gate control signal.

6. In a range-gated directionally scanned directionally ranging system having received signal utilization means, means for improving the indicated directional resolution of said system and comprising a correlation filter responsive to a range-gated output of said system and having an impulse response corresponding to an analog of a normalized replica of the response of said scanned system to a point source target;

and gating means responsively coupled to said correlation filter for coupling said signal utilization means to said range-gated system output only during a preselected change in sense of the amplitude rate of response of said filter.

7. The device of claim 6 in which said signal utilization means is responsively coupled to said system by said correlation filter and said gating means in tandem.

8. The device of claim 6 in which said gating means comprises a signal gate gatingly interconnecting an input of said signal utilization means and an output of said filter and having a gate control input responsive to a preselected change in sense in the amplitude rate of change of the output of said filter.

9. The device of claim 6 in which said gating means comprises control signal means responsive to an output of said filter for providing a control signal only during a preselected change in sense of the amplitude rate of response of said output of said filter;

and a signal gate interconnecting an output of said signal utilization means and said output of said filter and having a gate control input responsive to said control signal.

10. The device of claim 6 in which said filter means comprises range-time gated sample-and-hold means adapted to be responsive to an electrical output of said sensor indicative of a preselected target range;

a filter circuit responsive to said sample-and-hold means and having a preselected impulse function.

11. The device of claim 6 in which said means for gating-on comprises rate-signalling means responsive to an output of said filter means for providing a signal indicative of the rate of change of said output of said filter means gate control means responsive to an output of said rate-signalling means responsive to a preselected change of sense of said rate of change signal for generating a gate control signal;

signal gate means coupled to said output of said filter and having a gate control input responsive to said gate control signal.

12. In a directionally scanned directionally ranging system having output signal utilization means, correlation means for improving the indicated directional resolution of said system and comprising range-gated signal shaping means responsive to an output of said system and having an impulse response corresponding to analog of a normalized replica of the response of said ranging system to a point source target;

and gating means responsively coupled to said signal shaping means for coupling said signal utilization means to said system only during a preselected change in sense of the amplitude rate of response of said signal means corresponding to a maximum correlation of said system response with said point source target.

13. A correlation technique for improving the indicated directional resolution of a data pattern sampling system having output utilization means and comprising the steps of subjecting a range-gated output of said system to signal shaping means having an impulse responsive corresponding to an analog of a normalized replica of the response of said sampling system to a scanned point source data element;

and responsively coupling said signal utilization means to said system only during a preselected change in sense of the amplitude rate of the response of said signal shaping means corresponding to a maximum correlation of said system response with said data element.

14. A correlation technique for improving the indicated directional resolution a data pattern sampling system having output utilization means of and comprising the steps of subjecting a range-gated output of said system to signal shaping means having an impulse response corresponding to an analog of a normalized replica of the response of said sampling system to a directionally scanned point source data element;

and responsively coupling said signal utilization means to said signal shaping means only during a preselected change in sense of the amplitude rate of the response of said signal shaping means corresponding to a maximum correlation of said system response with said data element.

15. In a range-gated directionally scanned directionally ranging system having received signal utilization means, means for improving the indicated directional resolution of said system and comprising range-time gated sample-and-hold means adapted to be responsive to an electrical output of said system indicative of a preselected target range;

a filter circuit responsive to said sample-and-hold means and having a preselected impulse function;

rate-signalling means responsive to an output of said filter means for providing a signal indicative of the rate of change of said output of said filter means;

gate control means coupled to an output of said rate-signalling means and responsive to a preselected change of sense of said rate of change signal for generating a gate control signal; and

signal gate means coupled to said output of said filter and having a gate control input responsive to said gate control signal.