Marine Radar Based on Cylindrical Array Antennas with Other Applications

• US 20150323659A1
• Filed: 04/20/2015
• 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 9,599,704 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 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/66 Radar-tracking systems; Analogous systems
• CPC Class Codes: G01S 13/93 for anti-collision purposes
• CPC Class Codes: G01S 13/937 of marine craft
• CPC Class Codes: G01S 2013/0245 Radar with phased array antenna
• CPC Class Codes: G01S 7/04 Display arrangements
• CPC Class Codes: G01S 7/28 Details of pulse systems
• CPC Class Codes: G01S 7/2883 using FFT processing
• CPC Class Codes: H01Q 1/34 Adaptation for use in or on ships, submarines, buoys or torpedoes for subaqueous use H01Q1/04
• CPC Class Codes: H01Q 21/20 the units being spaced along or adjacent to a curvilinear path slotted waveguide arrays H01Q21/005; circularly or helically slotted waveguides H01Q21/0062
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence

Abstract

An all-solid-state marine radar technology based on a non-rotating cylindrical array antenna is described. Multiple transmit and receive 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 objects comprising:

providing a cylindrical array antenna with one or more layers of array elements equally spaced around a cylinder;

providing transmit and receive functions for the array elements;

activating a subset of the array elements at any given time;

generating waveforms that are common to all active transmit array elements, the waveforms having phase or frequency modulation to provide high resolution in range;

digitally controlling the transmit and receive array elements to activate a subset of the array elements for the waveforms generated;

controlling amplitude and phase of the generated waveforms in each active transmit array element in the subset to collectively form and point the respective transmit beam;

receiving returns from scatterers illuminated by the transmit beam at each active receive array element;

controlling amplitude and phase of the received returns at the respective active receive array elements, and summing the results to form a receive beam;

digitizing the summed results to form a digital representation of the radar return in the receive beam;

processing the digitized radar returns to

obtain range resolution represented by a sequence of range samples;

coherently process a sequence of received returns to obtain Doppler resolution represented by a sequence of Doppler samples, repeated in each receive 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 receive 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 detected moving targets on a computer monitor;

display received returns from stationary objects in a background mode;

repeat the above operations for a sequence of beam positions to scan a designated sector; and

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

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

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

4. The method of claim 1 wherein the cylindrical array antenna consists of two layers, one layer for the transmit function and the other layer for the receive function, to simplify hardware of the radar system, to allow more room for components, and/or to facilitate dissipation of heat.

5. The method of claim 1 wherein the cylindrical array antenna consists of two layers, one layer for the transmit function and the other layer for the receive function, and wherein the generated waveforms are continuous waveforms with phase or frequency modulation to provide high resolution in range.

6. The method of claim 1 wherein the cylindrical array antenna consists of two layers, one layer for the transmit function and both layers for the receive function, and wherein the generated waveforms are pulse waveforms with phase or frequency modulation to provide a measurement capability of a target elevation angle utilizing a monopulse principle.

7. The method of claim 1 wherein the cylindrical array antenna consists of three layers, one layer for the transmit function and the other two layers for the receive function, and wherein the generated waveforms are continuous waveforms with phase or frequency modulation to provide a measurement capability of a target elevation angle.

8. The method of claim 1 wherein separate antenna layers are used for the transmit and receive functions, and wherein the number of array elements in each layer, and the diameter of the cylinders are the same.

9. The method of claim 1 wherein separate antenna layers are used for the transmit and receive functions, and wherein the number of array elements in each layer, and/or the diameter of the cylinders, are not the same.

10. The method of claim 1 wherein the received returns of each active receive array element are digitized directly and combined in the digital signal processor to produce the receive beam.

11. The method of claim 1 wherein amplitude and phase adjustments are applied to the received returns of each active receive array element and combined in a manifold and down converted to baseband, then digitized and passed to the digital signal processor.

12. The method of claim 1 wherein amplitude and phase adjustments are applied to the received returns of each active receive array element, down converted to an intermediate frequency and combined in a manifold, then digitized and passed to the digital signal processor.

13. The method of claim 1 wherein the received returns of each active receive array element are down converted to an intermediate frequency, amplitude and phase adjustments are applied and combined in a manifold, digitized and passed to the digital signal processor.

14. The method of claim 1 wherein received returns of each active receive array element are down converted to an intermediate frequency, digitized, and then combined in the digital signal processor to produce the receive beam.

15. The method of claim 1 wherein received returns of each active receive array element are down converted to baseband, digitized, and then combined in the digital signal processor to produce the receive beam.

16. The method of claim 1 wherein a doublet or triplet of receive beams is formed in the digital signal processor to allow monopulse processing for accurate measurement of target bearing.

17. The method of claim 1 wherein multiple additional antennas are placed on top of the cylindrical array antenna for tracking of targets in a zenith sector via interferometry.

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

19. 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.

20. The method of claim 1 wherein a subset of transmit/receive modules are switched among the array elements.

21. The method in claim 1 wherein one active array element is added or subtracted from the active transmit and receive array elements on alternate scans to shift the beams by a half-increment.

22. The method in claim 1 wherein the waveforms are pulse waveforms, and wherein several positions of the transmit and receive beams are processed on alternating pulse waveforms to increase the coherent processing interval for better Doppler resolution.

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

24. The method of claim 23 wherein the platform on which the radar system is mounted is a boat or sea-going vessel and used for navigation and locating hazards.

25. The method of claim 24 wherein the radar system is also used to assess wave conditions and measure wave height.

26. The method of claim 23 wherein the radar system is operated from a shore-based location and used for monitoring ship traffic.

27. The method of claim 23 wherein the radar system is used for surveillance of borders, harbors, coastlines, and secure facilities.

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

29. The method of claim 23 wherein stationary received returns are monitored for navigation waypoints or potential hazards.