Offset feed antennas

• US 9,733,353 B1
• Filed: 01/16/2015
• Issued: 08/15/2017
• Est. Priority Date: 01/16/2014
• Status: Active Grant

• Current Assignee: L3harris Fuzing and Ordnance Systems Incorporated (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Security & Detection Systems, Inc. (Leidos Holdings, Inc.)
• Inventors: Sentelle, Christopher Gary, Carlson, Douglas O., Duvoisin, III, Herbert
• Primary Examiner(s): Bythrow, Peter
• Application Number:
  US14/598,428
• Time in Patent Office: 942 Days
• Field of Search: 342 22
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 13/88 Radar or analogous systems specially adapted for specific applications electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 13/888 through wall detection
• CPC Class Codes: G01V 3/105 forming directly coupled primary and secondary coils or loops
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 11/083 Tapered helical aerials, e.g. conical spiral aerials
• CPC Class Codes: H01Q 9/27 Spiral antennas

Abstract

An apparatus for detecting objects includes a transceiver configured to generate a radar signal, a radar having a transmit antenna configured to transmit the radar signal, and a receive antenna configured to sense a return signal in response to a transmission of the radar signal. The apparatus also includes a processor configured to detect an object based on the return signal. One or more of the transmit antenna or the receive antenna include offset spiral feed antennas.

Claims

1. An apparatus comprising:

a transceiver configured to generate a radar signal;

a radar configured to transmit the radar signal, the radar comprising a first offset spiral feed (OSF) antenna that includes substantially spiral shaped feed arms with a central point of the feed arms being offset from a center axis of the first OSF antenna that is substantially orthogonal to a plane of the first OSF antenna;

a receive antenna configured to sense a return signal in response to a transmission of the radar signal, the receive antenna being a second OSF antenna that includes substantially spiral shaped feed arms with a central point of the feed arms being offset from a center axis of the second OSF antenna that is substantially orthogonal to a plane of the second OSF antenna; and

a processor configured to detect an object based on the return signal,

wherein the first and the second OSF antennas are arranged such that the central point of the feed arms of the first OSF antenna is offset from the center axis of first OSF antenna in a direction away from the second OSF antenna.

2. The apparatus of claim 1, wherein the apparatus comprises a second receive antenna that comprises a third OSF antenna.

3. The apparatus of claim 2, wherein the first, second and third OSF antennas are configured to have respective squinted beams that substantially intersect with each other at a common point.

4. The apparatus of claim 1, wherein the processor is configured to:

calibrate the return signal based on amounts of the offsets; and

detect an object based on the calibrated return signal.

5. The apparatus of claim 1, wherein the spiral shaped feed arms of at least one of the first or the second OSF antenna comprise a logarithmic spiral shape.

6. The apparatus of claim 1, wherein the spiral shaped feed arms of at least one of the first or the second OSF antenna comprise an Archimedean spiral shape.

7. The apparatus of claim 1, wherein the spiral shaped feed arms of at least one of the first or the second OSF antenna comprise a spiral having a first portion with a logarithmic spiral shape and a second portion with an Archimedean spiral shape.

8. The apparatus of claim 1, wherein at least one of the first or the second OSF antenna is configured such that signals at higher frequencies are more squinted than signals at lower frequencies.

9. The apparatus of claim 1, comprising:

a continuous wave metal detector.

10. The apparatus of claim 9, wherein the continuous wave metal detector comprises:

a transmission coil around the antennas configured to transmit a set of signals; and

a receive coil that overlaps the antennas configured to sense return signals in response to a transmission of the set of signals.

11. The apparatus of claim 10, wherein the processor is configured to detect the object based on the return signal sensed by the receive antenna and the return signals received by the receive coil of the continuous wave metal detector.

12. The apparatus of claim 1, wherein the object comprises a metallic object located beneath a ground surface.

13. A method comprising:

generating, by a transceiver, a radar signal;

emitting the radar signal towards an object using first offset spiral feed (OSF) antenna;

in response to emitting the radar signal towards the object, sensing a return signal using a second OSF antenna; and

in response to sensing a return signal, detecting the object, wherein the first and second OSF antennas each comprise substantially spiral shaped feed arms with a central point of the feed arms being offset from a center axis of the OSF antenna that is substantially orthogonal to a plane of the OSF antenna, and wherein the first and the second OSF antennas are arranged such that the central point of the feed arms of the first OSF antenna is offset from the center axis of first OSF antenna in a direction away from the second OSF antenna.

14. The method of claim 13, wherein detecting the object comprises:

calibrating the return signal based on amounts of the offsets; and

detecting the object based on the calibrated return signal.

15. The method of claim 13, wherein the feed arms of the first OSF antenna comprises

a logarithmic spiral shape.

16. An antenna array comprising:

a first offset spiral feed (OSF) antenna that includes substantially spiral shaped feed arms with a central point of the feed arms being offset from a center axis of the first OSF antenna that is substantially orthogonal to a plane of the first OSF antenna;

a second OSF antenna that includes substantially spiral shaped feed arms with a central point of the feed arms being offset from a center axis of the second OSF antenna that is substantially orthogonal to a plane of the second OSF antenna, and

wherein the first and the second OSF antennas are arranged such that the central point of the feed arms of the first OSF antenna is offset from the center axis of first OSF antenna in a direction away from the second OSF antenna.

17. The antenna array of claim 16, wherein the spiral shaped feed arms of at least one of the first or the second OSF antenna comprise a logarithmic spiral shape.

18. The antenna array of claim 16, wherein the spiral shaped feed arms of at least one of the first or the second OSF antenna comprise an Archimedean logarithmic spiral shape.

19. The antenna array of claim 16, wherein the spiral shaped feed arms of at least one of the first or the second OSF antenna comprise a spiral having a first portion with a logarithmic spiral shape and a second portion with an Archimedean spiral shape.

20. The antenna array of claim 16, further comprising a third OSF antenna that includes substantially spiral shaped feed arms with a central point of the feed arms being offset from a center axis of the third OSF antenna that is substantially orthogonal to a plane of the third OSF antenna, and

wherein the first, second, and third OSF antennas are arranged such that the respective central points of the feed arms of each of the first, second, and third OSF antennas are offset in directions away from respective others of the first, second, and third OSF antennas.