RADAR SYSTEM

• US 3,870,992 A
• Filed: 04/26/1972
• Issued: 03/11/1975
• Est. Priority Date: 04/26/1972
• Status: Expired due to Term

• Current Assignee: Drexel W. Hanna Jr
• Original Assignee: Drexel W. Hanna Jr
• Inventors: Hanna, Drexel W. Jr.
• Primary Examiner(s): Hubler, Malcolm F.
• Application Number:
  US05/247,568
• Time in Patent Office: 1,049 Days
• Field of Search: 343/5DP
• US Class Current: 342/58
• CPC Class Codes: G01S 7/28 Details of pulse systems
• CPC Class Codes: G01S 7/2925 by using shape of radiation pattern

Abstract

In a radar system especially suitable for collision avoidance of ships at sea, the azimuth reporting resolution is improved by transmitting the radar signals so as to occur a plurality of times during the angle of beamwidth of a rotating radar antenna, and comparing the resulting echoes of successive radar signals that occur at time periods corresponding to various ranges and identifying as target signals only those of the echoes in the respective range periods occurring for a certain plurality of scan cycles within the antenna beamwidth angle. The bandwidth requirements of the system for communication from a plurality of such mobile stations to a central station are reduced by digitizing at the ships the range and azimuth data corresponding to said identified target signals and by treating as valid target signals those echoes that are repeated over successive frame cycles, and by reporting to the central station only such target information. Those echoes that are not repeated over successive sweep cycles are treated as non-target information or false alarms. A noise threshold for the detection of echo signals at the input is adjusted depending upon the number of false alarms (non-repeated target signals) in a frame. Only a limited number of targets at any azimuth location are reported. If at some point the number of valid target signals in an antenna frame matches some predetermined value, then the target data for only that first portion of the frame are reported to the central station. During the succeeding frame, the report to the central station starts at the azimuth limit where the previous frame report left off.

Claims

1. In a radar system, a plurality of moving radar stations and a central data processing station, in which each moving station develops target information and transmits the target information to the central data processing station over a time-shared communications channel, and in which each radar station includes a memory device for retaining target data to be transmitted to the central station;

the method of developing target data in high density target areas for each of said moving stations, comprising the steps of;

a. developing said target data during each target frame in moderate density areas and transmitting the developed data to the central station;

b. during each target frame in high density areas, detecting when the target storage device is full of target data, and registering the azimuth at which the memory device becomes full and transmitting the target data from an initial azimuth until the memory-full azimuth;

c. and following thereupon during the next frame, storing target data starting with the memory-full azimuth and continuing on therefrom and storing the target data for transmission to the central station until the memory device becomes full or the frame is completed;

whereby in high density areas target data is fully developed in surrounding regions over a plurality of frames.

2. In a radar system, a plurality of moving radar stations and a central data processing station, in which each moving station develops target information and transmits the target information to the central data processing station over a time-shared communications channel, and in which each radar station includes a memory device for retaining target data to be transmitted to the central station;

the method of developing target data in high density target areas for each of said moving stations, comprising the steps of;

a. developing said target data during each target frame in moderate density areas and transmitting the developed data to the central station;

b. during each target frame in high density areas, detecting when the target storage device is full of target data, and registering the azimuth at which the memory device becomes full and transmitting the target data from an initial azimuth until the memory-full azimuth;

c. and following thereupon during a succeeding frame, storing target data for azimuths after the memory-full azimuth for transmission to the central station until the memory device becomes full or the frame is completed;

whereby in high density areas target data is fully developed in surrounding regions over a plurality of frames.