Marine Radar Based on Cylindrical Array Antennas with Other Applications

• US 20150323658A1
• Filed: 05/06/2014
• Published: 11/12/2015
• Est. Priority Date: 05/06/2014
• Status: Active Grant

• Current Assignee: Mark Resources, Inc.
• Original Assignee: Mark Resources, Inc.
• Inventors: Mitchell, Richard L.
• Granted Patent: US 9,696,419 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 13/02 Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
• CPC Class Codes: G01S 13/66 Radar-tracking systems; Analogous systems
• CPC Class Codes: G01S 13/91 for traffic control G01S13/93 takes precedence
• CPC Class Codes: G01S 13/937 of marine craft
• CPC Class Codes: G01S 2013/0245 Radar with phased array antenna
• CPC Class Codes: G01S 7/032 Constructional details for solid-state radar subsystems
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26

Abstract

An all-solid-state marine radar technology based on a non-rotating cylindrical array antenna is described. Multiple transmit/receive (T/R) modules are used to form the antenna beam, which allows the beam sequencing, the dwell time in each beam position, the resolution, and the beam shape to be varied in order to make best use of the available energy. Waveforms with a high duty ratio can be used on transmit in order to make efficient use of solid-state power amplifiers. High resolution in both range and Doppler provides high measurement accuracy and superior performance in clutter. Alternate embodiments, including continuous waveform embodiments are disclosed.

Claims

1. A method of providing and operating a radar system for detecting moving targets comprising:

providing a cylindrical array antenna with one layer of array elements equally spaced around a cylinder;

providing a transmit/receive module for each of the array elements;

activating a subset array elements at any given time, which is typically about ⅓

rd of the total;

generating waveforms that are to be common to all active transmit/receive modules;

employing pulsed waveforms with phase or frequency modulation to provide high resolution in range;

digitally controlling the transmit/receive modules to activate a subset of the cylindrical array to transmit the waveforms generated;

controlling the amplitude and phase of the transmit signal in each of the active transmit/receive modules in the subset to form and point the respective transmit beam;

receiving returns of transmit signal in the active transmit/receive modules;

controlling amplitude and phase of the receive signal in the active transmit/receive modules to form the receive beam;

down converting the received the returns in each active transmit/receive module to an intermediate frequency;

combining the received returns from all active transmit/receive modules at an intermediate frequency in a manifold;

digitizing the down converted intermediate frequency return at the output of the manifold;

passing of digitized down converted received returns to a digital signal processor to;

obtain range resolution;

coherently process a sequence of received returns to obtain Doppler resolution, repeated in each beam for each range sample;

envelope detect the range and Doppler samples;

compare the envelope detected range and Doppler samples with at least one threshold for detection of the moving targets;

record the beam positions of detected moving targets;

compare detected moving targets with previously detected targets already in track, check for range ambiguities, and update track files;

display the tracked targets on computer monitor;

display stationary returns in a background mode;

change waveform repetition frequency on alternate scans to resolve range and Doppler ambiguities.

2. The method of claim 1 wherein the overall surveillance range is divided into zones with different waveforms used in each zone to maximize the transmit duty ratio.

3. The method in claim 1 wherein coherent processing is via fast Fourier transforms.

4. The method of claim 1 wherein the cylindrical antenna consists of two layers where each layer has the same number of equally-spaced elements, one layer for transmit and the other for receive, to employ continuous waveforms with phase or frequency modulation to provide high resolution in range.

5. The method of claim 1 wherein the cylindrical antenna consists of two layers where each layer has the same number of equally-spaced elements, one layer for transmit and both for receive, to employ pulse waveforms with phase or frequency modulation to provide a measurement capability of the target elevation angle utilizing the monopulse principle.

6. The method of claim 1 wherein the cylindrical antenna consists of three layers where each layer has the same number of equally-spaced elements, one layer for transmit and the other two for receive, to employ continuous waveforms with phase or frequency modulation to provide a measurement capability of the target elevation angle

7. The method of claim 1 wherein the received returns in each active transmit/receive module are combined at the radar frequency in a manifold.

8. The method of claim 7 wherein the combined received returns at the radar frequency at the output of the manifold are down converted to an intermediate frequency prior to digitizing.

9. The method of claim 7 wherein the combined received returns at the radar frequency manifold are down converted to baseband prior to digitizing.

10. The method of claim 1 wherein the received returns in each active transmit/receive module are down converted to an intermediate frequency and separately digitized, allowing the receive beams to be formed in the digital signal processor.

11. The method of claim 10 wherein a triplet of receive beams is formed in the digital signal processor to allow monopulse processing for the accurate measurement of target bearing.

12. The method of claim 10 wherein multiple antennas are placed on top of the cylindrical array antenna for tracking of targets in the zenith sector via interferometry.

13. The method of claim 1 wherein the cylindrical array antenna is non-rotating and in a shore based location.

14. The method of claim 1 wherein the cylindrical array antenna is located on a moveable platform and is non-rotating with respect to that platform, and further comprising compensation of the phase of the received returns for platform motion.

15. The method of claim 1 wherein N/3 transmit/receive modules are switched among N array elements.

16. The method in claim 1 wherein one active element is added or subtracted from the active elements on alternate scans to shift the antenna beams by a half-step on alternate scans.

17. The method in claim 1 wherein several beam positions are processed on alternating pulses to increase the coherent processing interval for better Doppler resolution.

18. The method of claim 1 wherein the cylindrical array antenna is non-rotating relative to a platform on which it is mounted.

19. The method of claim 18 wherein the platform on which the radar is mounted is a boat or sea-going vessel and used for navigation and locating hazards.

20. The method of claim 19 wherein the radar is also used to assess wave conditions and measure wave height.

21. The method of claim 18 wherein the radar is operated from a shore-based location and used for monitoring ship traffic.

22. The method of claim 18 wherein the radar is used for surveillance of borders, harbors, coastlines, and secure facilities.

23. The method of claim 18 wherein the radar is used for surveillance of airspace.

24. The method of claim 18 wherein isolated stationary returns are monitored for navigation waypoints or potential hazards.