Metamaterial-based object-detection system

• US 9,545,923 B2
• Filed: 07/14/2014
• Issued: 01/17/2017
• Est. Priority Date: 07/14/2014
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Casse, Bernard D., Volkel, Armin R., Liu, Victor, Tuganov, Alexander S.
• Primary Examiner(s): Jos, Basil T
• Application Number:
  US14/331,024
• Publication Number:
  US 20160011307A1
• Time in Patent Office: 918 Days
• US Class Current: 1/1
• CPC Class Codes: B60W 30/14 Adaptive cruise control
• CPC Class Codes: G01S 13/426 Scanning radar, e.g. 3D radar G01S13/66 takes precedence
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/0254 Active array antenna
• CPC Class Codes: G01S 2013/93271 in the front of the vehicles
• CPC Class Codes: G01S 2013/93275 in the bumper area
• CPC Class Codes: H01Q 1/3233 particular used as part of a sensor or in a security system, e.g. for automotive radar, navigation systems
• CPC Class Codes: H01Q 1/3283 side-mounted antennas, e.g. bumper-mounted, door-mounted mounted on windscreens H01Q1/1271
• CPC Class Codes: H01Q 15/0086 said selective devices having materials with a synthesized negative refractive index, e.g. metamaterials or left-handed materials
• CPC Class Codes: H01Q 15/148 with means for varying the reflecting properties H01Q15/147 takes precedence
• CPC Class Codes: H01Q 21/0093 Monolithic arrays
• CPC Class Codes: H01Q 3/46 Active lenses or reflecting arrays

Abstract

An object-detection system for, e.g., a vehicle collision avoidance system, utilizes a metamaterial-based phase shifting element array to generate a scan beam by varying the effective capacitance of each metamaterial structure forming the array in order to control the phases of their radio frequency output signals such that the combined electromagnetic wave generated by the output signals is reinforced in the desired direction and suppressed in undesired directions to produce the scan beam. The metamaterial structures are configured to resonate at the same radio wave frequency as an incident input signal (radiation), whereby each metamaterial structure emits an associated output signal by way of controlled scattering the input signal. A variable capacitance is applied on each metamaterial structure, e.g., using varicaps that are adjusted by way of phase control voltages, to produce the desired output phase patterns. The metamaterial structures are constructed using inexpensive metal film or PCB fabrication technology.

Claims

1. An object-detection system comprising:

a signal source configured to generate an input signal having a radio wave frequency in the range of 2.4 GHz to 300 GHz;

a phase shifting element array including a plurality of metamaterial structures, each said metamaterial structure configured to resonate at said radio wave frequency in response to said input signal such that said plurality of metamaterial structures respectively generate electromagnetic radiation output signals having said radio wave frequency by way of retransmitting said input signal; and

a beam control circuit configured to generate a plurality of variable capacitances and to apply each said variable capacitance to an associated said metamaterial structure such that an effective capacitance of said associated metamaterial structure is altered by a corresponding change in each said applied variable capacitance, whereby said plurality of metamaterial structures respectively generate said electromagnetic radiation output signals at corresponding output phases determined by said plurality of variable capacitances, wherein said beam control circuit is further configured to vary said plurality of variable capacitances such that said output signals collectively generate a scan beam that sweeps across a field disposed in front of said phase shifting element array.

2. The object-detection system according to claim 1, wherein the beam control circuit comprises:

a plurality of variable capacitors configured to respectively generate associated variable capacitances, each said variable capacitor being coupled to an associated metamaterial structure of said plurality of metamaterial structures such that an effective capacitance of said associated metamaterial structure is altered by a corresponding change in the variable capacitance generated by said each variable capacitor; and

a phase control circuit configured to generate a plurality of phase control voltages, each phase control voltage being applied to an associated variable capacitor of said plurality of variable capacitors such that said associated variable capacitance of said associated variable capacitor varies in accordance with said each phase control voltage, and each phase control voltage having a respective voltage level that varies over time such that said plurality of metamaterial structures respectively generate said output signals at a plurality of different output phases respectively coordinated to cause said scan beam to sweep across the field.

3. The object-detection system of claim 2, wherein each said variable capacitor is configured such that:

when said phase control voltage applied across said each variable capacitor has a first voltage level, said each variable capacitor generates said variable capacitance at a first capacitance level and said associated metamaterial structure generates said output signal at an associated first output phase, and

when said phase control voltage is increased from said first voltage level to a second voltage level, said each variable capacitor generates said variable capacitance at a second capacitance level such that said associated metamaterial structure generates said output signal at an associated second output phase, said second output phase being greater than said first output phase.

4. The object-detection system of claim 2,

wherein each said variable capacitor includes a first terminal and a second terminal, said first terminal connected to said associated metamaterial structure, and

wherein said second terminal of all of said plurality of variable capacitors is connected to a common voltage source.

5. The object-detection system of claim 2, further comprising a plurality of conductive structures for respectively transmitting said plurality of phase control voltages, each said conductive structure connected between said phase control circuit and one of an associated metamaterial structure and said first terminal of said associated variable capacitor, whereby when one of said phase control voltages is applied by way of said each conductive structure and said second terminal of said associated variable capacitor is connected to a ground potential, said associated variable capacitor generates said associated variable capacitance having a capacitance level that is proportional to said phase control voltage.

6. The object-detection system according to claim 2,

wherein said beam control circuit is further configured to generate beam direction data indicating an instantaneous beam direction of said scan beam,

wherein said object-detection system further comprises:

a receiver configured to detect beam portions of said scan beam that are reflected from objects disposed in said field, and configured to generate beam detection data indicating each detection of an associated reflected said beam portion, and

signal processing circuitry configured to detect the position of an object in said field by combining said beam direction data with said beam detection data generated by reflection of said scan beam from said object.

7. The object-detection system of claim 2, wherein said phase shifting element array further comprises:

an electrically isolated lower metal layer; and

a dielectric layer disposed over the lower metal layer,

wherein each said metamaterial structure includes a metal island structure disposed on the dielectric layer and an associated lower layer portion of said lower metal layer, said associated lower layer portion being disposed directly under said metal island structure, and

wherein said metal island structure and said associated lower layer portion of each said metamaterial structure are cooperatively configured such that said each metamaterial structure resonates at said radio wave frequency and has said fixed capacitance.

8. The object-detection system of claim 7, wherein said dielectric layer comprises a dielectric material.

9. The object-detection system of claim 7,

wherein said phase shifting element array further comprises a base metal structure disposed on said upper dielectric surface and spaced from each said metal island structure of said plurality of metamaterial structures, and

wherein each said variable capacitor of said plurality of variable capacitors includes a first terminal connected to said metal island structure of said associated metamaterial structure and a second terminal connected to said base metal structure.

10. The object-detection system of claim 9,

wherein said base metal structure defines a plurality of openings, each said opening having an inner peripheral edge,

wherein each said metal island structure is disposed inside an associated opening of said plurality of openings such that an outer peripheral edge of said metal island structure is separated from the inner peripheral edge of said base metal structure by a peripheral gap configured such that said metal island structures of each of the plurality of metamaterial structures resonates at said radio wave frequency.

11. The object-detection system of claim 10, wherein said base metal structure and said metal island structures comprise a single metal.

12. The phased array apparatus of claim 7, wherein said phase shifting element array further comprises a plurality of metal via structures, each said metal via structure extending through the dielectric layer and contacting the first terminal of an associated variable capacitor of said plurality of variable capacitors.

13. The object-detection system of claim 7, wherein said metal island structure of each of said plurality of metamaterial structures comprises a square peripheral edge.

14. The phased array apparatus of claim 7, wherein said metal island structure of each of the plurality of metamaterial structures comprises a patterned planar structure defining one or more open regions.

15. The phased array apparatus of claim 7,

wherein said plurality of metamaterial structures are arranged in a one-dimensional array such that said metal island structures are aligned in a row, and

wherein said control circuit is configured to continuously change said plurality of phase control voltages such that said plurality of metamaterial structures respectively generate said output signals at a continuously changing plurality of different output phases such that said scan beam is swept in a two-dimensional pattern across said field.

16. The phased array apparatus of claim 7,

wherein said plurality of metamaterial structures are arranged in a two-dimensional array such that said metal island structures are aligned in a plurality of rows and a plurality of columns, and

wherein said control circuit is configured to continuously change said plurality of phase control voltages such that said plurality of metamaterial structures respectively generate said output signals at a continuously changing plurality of different output phases such that said directed beam is scanned in a three-dimensional region.

17. A vehicle collision avoidance system for avoiding collision of a host vehicle with one or more objects, the vehicle including an adaptive cruise control system capable of assuming automated control of the vehicle, the vehicle collision avoidance system comprising:

a phase shifting element array including a plurality of metamaterial structures disposed to receive a single electromagnetic radiation input signal having a radio wave frequency in the range of 2.4 GHz to 300 GHz, each said metamaterial structure configured to resonate at said radio wave frequency such that said each metamaterial structure generates an associated electromagnetic radiation output signal having said radio wave frequency, wherein said phase shifting element array is mounted on said vehicle such that said output signals generated by said plurality of metamaterial structures are directed into a field located adjacent to said vehicle;

a beam control circuit configured to generate a plurality of variable capacitances and to apply each said variable capacitance to an associated said metamaterial structure such that an effective capacitance of said associated metamaterial structure is altered by a corresponding change in each said applied variable capacitance, whereby said plurality of metamaterial structures respectively generate said electromagnetic radiation output signals at corresponding output phases determined by said plurality of variable capacitances, wherein said beam control circuit is further configured to vary said plurality of variable capacitances such that a combined electromagnetic wave generated by said output signals is reinforced in an angular emission direction, whereby the said output signals collectively generate a scan beam directed in the angular emission direction, and wherein said beam control circuit is further configured to gradually change said plurality of variable capacitances such that the scan beam direction of the scan beam emitted from said phase shifting element array gradually changes, thereby causing the scan beam to sweep across said field;

a receiver configured to detect beam portions of said scan beam that are reflected from one or more objects disposed in said field, and to generate beam detection data indicating detection of said one or more objects in accordance with said detected beam portions, and

a signal processing circuit configured to detect the position of said one or more objects in said field in accordance with said beam detection data, and to transmit collision control avoidance data to said adaptive cruise control system such that said adaptive cruise control system assumes automated control of the vehicle to avoid collision with said one or more objects.

18. The vehicle collision avoidance system of claim 17,

wherein said plurality of metamaterial structures are arranged in a one-dimensional array such that said metal island structures are aligned in a row, and

wherein said control circuit is configured to continuously change said plurality of phase control voltages such that said plurality of metamaterial structures respectively generate said output signals at a continuously changing plurality of different output phases such that said scan beam is swept into a two-dimensional pattern across said field.

19. The vehicle collision avoidance system of claim 17,

wherein said plurality of metamaterial structures are arranged in a two-dimensional array such that said metal island structures are aligned in a plurality of rows and a plurality of columns, and

wherein said control circuit is configured to continuously change said plurality of phase control voltages such that said plurality of metamaterial structures respectively generate said output signals at a continuously changing plurality of different output phases such that said scan beam is swept through a three-dimensional region of said field.

20. A vehicle comprising:

an adaptive cruise control system capable of assuming automated control of the vehicle; and

an object detection system including;

a signal source configured to generate an electromagnetic radiation input signal having a radio wave frequency in the range of 2.4 GHz to 300 GHz;

a phase shifting element array including a plurality of metamaterial structures disposed in proximity to said signal source such that said plurality of metamaterial structures are subjected to said input signal, each said metamaterial structure configured to resonate at said radio wave frequency such that said plurality of metamaterial structures respectively generate electromagnetic radiation output signals having said radio wave frequency, wherein said phase shifting element array is mounted on said vehicle such that said output signals are directed into a field located adjacent to said vehicle;

a beam control circuit configured to generate a plurality of variable capacitances and to apply each said variable capacitance to an associated said metamaterial structure such that an effective capacitance of said associated metamaterial structure is altered by a corresponding change in each said applied variable capacitance, whereby said plurality of metamaterial structures respectively generate output signals at corresponding output phases determined by said plurality of variable capacitances, wherein said beam control circuit is further configured to vary said plurality of variable capacitances such that a combined electromagnetic wave generated by said output signals is reinforced in an angular emission direction, whereby the said output signals collectively generate a scan beam directed in the angular emission direction, and wherein said beam control circuit is further configured to gradually change said plurality of variable capacitances such that the scan beam direction of the scan beam emitted from said phase shifting element array gradually changes, thereby causing the scan beam to sweep across said field;

a receiver configured to detect beam portions of said scan beam that are reflected from one or more objects disposed in said field, and to generate beam detection data indicating detection of said one or more objects in accordance with said detected beam portions, and

a signal processing circuit configured to detect the position of said one or more objects in said field in accordance with said beam detection data, and to transmit collision control avoidance data to said adaptive cruise control system such that said adaptive cruise control system assumes automated control of the vehicle to avoid collision with said one or more objects.