Adaptive beam forming antenna system using a tunable impedance surface

• US 20040263408A1
• Filed: 05/11/2004
• Published: 12/30/2004
• Est. Priority Date: 05/12/2003
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Sievenpiper, Daniel F., Schaffner, James H., Tangonan, Gregory L.
• Granted Patent: US 7,245,269 B2
• Time in Patent Office: Days
• US Class Current: 343/757
• CPC Class Codes: H01Q 19/104 using a substantially flat reflector for deflecting the radiated beam, e.g. periscopic antennas periscopic fed Cassegrain antennas H01Q19/191; passive relays H04B7/145
• CPC Class Codes: H01Q 3/46 Active lenses or reflecting arrays

Abstract

A method of and apparatus for beam steering. A feed horn is arranged so that the feed horn illuminates a tunable impedance surface comprising a plurality of individually tunable resonator cells, each resonator element having a reactance tunable by a tuning element associated therewith. The tuning elements associated with the tunable impedance surface are adjusted so that the resonances of the individually tunable resonator cells are varied in a sequence and the resonances of the individually tunable resonator cells are set to values which improve transmission of information via the tunable impedance surface and the feed horn.

Claims

1. A method of beam steering comprising:

a. arranging an antenna so that the antenna radiates a tunable impedance surface with RF radiation, the tunable impedance surface having a plurality of tunable resonator cells, each resonator element being tunable by at least one tuning element associated therewith;

b. applying an initial set of control signals to the tuning elements associated with the tunable impedance surface group by group;

c. adjusting the control signal up and down by an incremental amount v for a selected group;

d. transmitting and/or receiving an RF signal which is reflected from the tunable impedance surface and measuring a parameter associated with power of the transmitted and/or received RF signal for three cases of −

v, 0, and +v adjustments of the control signal for said selected group;

e. noting a best value of the control signal for the three cases and setting the control signal accordingly for said selected group and adjusting the control signal up and down by said incremental amount v for another selected group;

f. repeating steps d and e to adjust each of said tunable resonator cells associated with the tunable impedance surface; and

g. repeating steps c-f to adjust the plurality of tuning elements associated with the tunable impedance surface for a period of time.

2. The method of claim 1 wherein in step g the absolute value of v is decreased during said period of time.

3. The method of claim 1 wherein adjusting the control signal up and down by said incremental amount v for the selected one of the resonator cells causes the resonance of the selected one of the resonator cells to vary step-wise.

4. The method of claim 3 wherein adjusting the control signal up and down by said incremental amount v for the another selected one of the resonator cells causes the resonance of the another selected one of the resonator cells to vary step-wise.

5. The method of claim 1 wherein said antenna is a horn type antenna.

6. The method of claim 1 wherein the tuning elements associated with the plurality of individually tunable resonator cells comprise variable impedance devices.

7. The method of claim 6 wherein the variable impedance devices comprise varactor diodes and the control signals comprise control voltages.

8. A method of beam steering comprising:

a. arranging an antenna so that the antenna radiates a tunable impedance surface with RF radiation, the tunable impedance surface having a plurality of tunable resonator cells, each resonator element having a reactance tunable by at least one tuning element associated therewith;

b. sequentially adjusting the tuning elements associated with the tunable impedance surface so that resonances of the tunable resonator cells are varied in a sequence and setting the resonances of the tunable resonator cells to values which improve transmission of information via said tunable impedance surface and said antenna.

9. The method of claim 8 wherein the resonances of the tunable resonator cells are varied step-wise in said sequence.

10. The method of claim 9 wherein the step-wise variance of the resonances of the tunable resonator cells decreases over a period of time.

11. The method of claim 8 wherein the tuning elements are voltage controlled capacitors.

12. The method of claim 11 wherein the adjusting of tuning elements associated with the tunable impedance surface is performed by adjusting a control voltage supplied to said voltage controlled capacitors.

13. The method of claim 12 wherein the adjusting of the voltages supplied to said voltage controlled capacitors is performed step-wise.

14. The method of claim 13 wherein the step-wise variance of the voltages supplied to said voltage controlled capacitors decreases over a period of time.

15. The method of claim 14 wherein the information whose transmission is improved is desired information and wherein reception of undesired information is diminished.

16. A communication system comprising:

a. an antenna;

b. a tunable impedance surface disposed to reflect RF radiation between at least one communications link and said antenna, the tunable impedance surface having a plurality of tunable resonator cells arranged in a two dimensional array, each resonator element having a reactance that is tunable by at least one tuning element associated therewith;

c. a receiver and controller coupled to said antenna, the receiver and controller including a signal discriminator for measuring one or more parameters associated with communication quality of service over said at least one communications link, the receiver and controller sequentially adjusting the tuning elements associated with the tunable resonator cells in said tunable impedance surface in order to improve the communication quality of service over said at least one communications link.

17. The communication system of claim 16 wherein the antenna is a feed horn.

18. The communication system of claim 16 wherein the tuning elements associated with the tunable resonator cells are variable impedance devices.

19. The communication system of claim 16 wherein the receiver and controller:

a. apply an initial set of control signals to the tuning elements associated with the tunable impedance surface, the tuning elements being arranged in groups having one or more tuning elements for each group;

b. adjust the control signal up and down by an incremental amount v for a selected group of one or more tuning elements;

c. receive an RF signal which is reflected from the tunable impedance surface and measure a parameter associated with power of the transmitted and/or received RF signal for three cases of −

v, 0, and +v adjustments of the control signal for the selected group of one or more tuning elements;

d. note a best value of the control signal for the three cases and set the control signal accordingly for said selected one of the groups of one or more tuning elements and adjusting the control signal up and down by said incremental amount v for another selected one of the tuning elements;

e. repeat items c and d to adjust each of the groups tunable tuning elements associated with the tunable impedance surface; and

f. repeat items b-e to adjust all tuning elements associated with the tunable impedance surface in a continuous pattern for a period of time.

20. A method of beam steering comprising:

a. arranging an antenna so that the antenna radiates a tunable impedance surface with RF radiation, the tunable impedance surface having tuning elements associated with the tunable impedance surface, the tuning elements being arranged in groups having one or more tuning elements for each group;

b. applying an initial set of control signals to the groups of one or more tuning elements associated with the tunable impedance surface;

c. adjusting the control signal by an incremental amount v for a selected group of one or more tuning elements;

d. receiving and/or transmitting an RF signal which is reflected from the tunable impedance surface and measuring a parameter associated with power of the transmitted and/or received RF signal for three cases of −

v, 0, and +v adjustments of the control signal for the selected group of one or more tuning elements;

e. noting a best value of the control signal for the three cases and setting the control signal accordingly for said selected one of the groups of one or more tuning elements and adjusting the control signal by said incremental amount v for another selected one of the tuning elements;

f. repeating subparagraphs d and e to adjust each of the groups tunable tuning elements associated with the tunable impedance surface; and

g. repeating subparagraphs b-e to adjust all tuning elements associated with the tunable impedance surface in a continuous pattern for a period of time.

21. The method of claim 20 wherein the tunable elements comprise an array of resonator cells, the array of resonator cells being defined by an array of plates (i) disposed on a dielectric surface and (ii) spaced from a ground plane by a distance which is less than one quarter wavelength of a frequency of the RF radiation.