Spatially light modulated reconfigurable photoconductive antenna

• US 6,177,909 B1
• Filed: 11/04/1999
• Issued: 01/23/2001
• Est. Priority Date: 11/04/1999
• Status: Expired due to Fees

• Current Assignee: United States Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Derov, John S., Reid, James R., Carr, Paul H.
• Primary Examiner(s): LE, HOANGANH T
• Application Number:
  US09/433,762
• Time in Patent Office: 446 Days
• Field of Search: H01/Q.138, 343/700.MS, 343/793, 343/795, 343/810, 343/792.5
• US Class Current: 343/700.0MS
• 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 19/062 for focusing

Abstract

A reconfigurable photoconducting antenna is created on a semiconductor substrate. At equilibrium, the semiconductor is semi-insulating, and therefore appears as a dielectric. Illuminating a region of the substrate results in the generation of free carriers in the substrate and allows the creation of a conductive region (semi-metallic) in the substrate. This conductive region functions as the radiating element of the antenna. Controlling the pattern of the illuminated region directly controls the pattern of the radiating antenna. By using a digital micromirror device (DMD™) to control the pattern of the light, a desired antenna design may be placed on the semiconductor substrate. The pattern can be dynamically adjusted simply by changing the position of the individual mirrors in the DMD™ array. The device operates through a standardized digital interface and can be switched between patterns in a period of approximately 20 microseconds. The pattern of the DMD™ can therefore be readily and easily controlled through the use of a digital control system.

Claims

1. A reconfigurable antenna system, said reconfigurable antenna system comprising:

means for inputting collimated light;

a spatial light modulator, said spatial light modulator receiving light from said means for inputting;

an electronic digital interface, said interface connected to said spatial light modulator; and

a electronic digital control system, said control system connected to said interface, said control system having therein means for determining an antenna pattern and directing signals to said spatial light modulator;

means for focusing light from said spatial light modulator to form said antenna pattern;

a semiconductor antenna substrate, light from said means for focusing selectively directed to said antenna substrate whereby said antenna pattern is created upon said substrate to produce said antenna;

a feed circuit for said antenna substrate, said feed circuit placed upon said substrate and connected to said antenna;

a reflector means for controlling the directivity of said antenna; and

a transceiver means connected to said feed circuit for processing signals to and/or from said antenna.

2. A reconfigurable antenna system as defined in claim 1 wherein said means for inputting light is a laser.

3. A reconfigurable antenna system as defined in claim 1 wherein said spatial light modulator is a digital micromirror device having a plurality of mirrors for directing the collimated light to said antenna substrate.

4. A reconfigurable antenna system as defined in claim 1 wherein said means for controlling the directivity of said antenna is a Fabry-Perot plate or a photonic band gap crystal.

5. A reconfigurable antenna system as defined in claim 1 wherein said antenna is planar.

6. A reconfigurable antenna system as defined in claim 5 wherein said antenna pattern is selected from the group consisting of a log periodic, a bow-tie, and a phased array antenna.

7. A reconfigurable antenna system as defined in claim 1 wherein said antenna is essentially nonexistant when not in use and thus minimizes RF reflections.

8. A reconfigurable antenna system as defined in claim 1 wherein different antenna patterns may be selected in a period of about 20 microseconds or less.

9. A reconfigurable antenna system as defined in claim 1 wherein a plurality of feed circuits are positioned on said substrate and are connected to the appropriate antenna pattern.

10. A process for creating a reconfigurable antenna, said process consisting of the steps of:

selecting an antenna pattern within a control system;

inputting said antenna pattern to a spatial light modulator through an electronic interface from said control system;

focusing light from said spatial light modulator onto a semiconductor substrate;

forming said antenna pattern on said semiconductor substrate to form an antenna;

connecting said antenna to a feed line;

controlling the directivity of said antenna; and

processing output and/or input signals from said antenna.

11. A process for creating a reconfigurable antenna as defined in claim 10 wherein said inputting antenna pattern comes from a laser.

12. A process for creating a reconfigurable antenna as defined in claim 10 wherein illuminating a digital micromirror device having a plurality of mirrors for directing the collimated light image to said antenna substrate.

13. A process for creating a reconfigurable antenna as defined in claim 10 wherein said antenna is planar.

14. A process for creating a reconfigurable antenna as defined in claim 10 wherein said planar antenna pattern is selected from the group consisting of a log periodic, a bow-tie, and a phased array antenna.

15. A process for creating a reconfigurable antenna as defined in claim 10 wherein said antenna is essentially non-existent when not in use and thus minimizes RF reflections.

16. A process for creating a reconfigurable antenna as defined in claim 10 wherein different antenna patterns may be selected in a period of about 20 microseconds or less.