MEMS based tunable antena for wireless reception and transmission

• US 20050057399A1
• Filed: 06/25/2004
• Published: 03/17/2005
• Est. Priority Date: 09/11/2003
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Rao, Valluri, Kipnis, Issy, Srinivasan, Balakrishnan, Hayden, Joe III
• Granted Patent: US 7,167,135 B2
• Time in Patent Office: Days
• US Class Current: 343/700.MS
• 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 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40
• CPC Class Codes: H01Q 9/0442 with particular tuning means

Abstract

An antenna for a wireless device may be kept dynamically tuned to a desired center frequency to compensate for detuning which may be caused by environmental influences. A sensor provides a feedback signal to a controller to select an appropriate capacitance value from a variable capacitor to tune the antenna for the wireless device. The variable capacitor may comprise a plurality of fixed capacitors and MEMS switches arranged in parallel or may comprise a variable MEMS capacitor having a fixed lower plate and a flexible upper plate.

Claims

1. An apparatus, comprising:

an antenna;

a variable capacitor module operatively connected to the antenna;

a sensor in proximity to the antenna to detect antenna radiated power; and

a controller to receive a signal from the sensor to vary a capacitance of the variable capacitor module to tune the antenna to a desired center frequency.

2. The apparatus as recited in claim 1 wherein the antenna comprises a patch antenna.

3. The apparatus as recited in claim 2 wherein the sensor comprises one of a coil and a directional coupler arranged in a feed-back loop.

4. The apparatus as recited in claim 1 wherein the variable capacitor module comprises:

a plurality of fixed capacitors arranged in parallel; and

a plurality of micro-electromechanical system (MEMS) switches for selecting ones of the plurality of fixed capacitors.

5. The apparatus as recited in claim 1 wherein the variable capacitor module comprises:

a fixed plate and flexible plate separated a distance from the fixed plate, wherein the distance may be varied in response to a control voltage applied between the fixed plate and the flexible plate.

6. The apparatus as recited in claim 3 further comprising a look-up table to determine the capacitance of the variable capacitor module for the desired center frequency.

7. A method, comprising:

tuning an antenna to a desired frequency by varying a capacitance of a variable capacitor module;

positioning a sensor in proximity to the antenna to produce a feed-back signal to indicate a drift from the desired frequency; and

varying a capacitance value of the variable capacitor module to maintain the antenna tuned to the desired frequency.

8. The method as recited in claim 7, wherein dynamically varying the capacitance value, comprises:

arranging a plurality fixed capacitors in parallel; and

actuating selected micro-electromechanical system (MEMS) switches connected to the plurality of fixed capacitors.

9. The method as recited in claim 7, wherein dynamically varying the capacitance value, comprises:

supplying an actuation voltage to a micro-electromechanical system (MEMS) capacitor causing an upper plate to flex towards a lower plate.

10. The method as recited in claim 7 further comprising:

converting a near field signal from the feed-back loop to a far field signal with a Fourier transform.

11. The method as recited in claim 10, further comprising:

using the far field signal to determine an actuation voltage to change the capacitor value of a micro-electromechanical system (MEMS) capacitor.

12. The method as recited in claim 10, further comprising:

using the far field signal to determine ones of a plurality of micro-electromechanical system (MEMS) switches to active to change the capacitor value of a bank of parallel connected fixed capacitors.

13. A wireless system, comprising:

a power amplifier to supply a transmit (Tx) signal to a patch antenna;

an antenna switch filter (ASF) connected to switch the patch antenna between the power amplifier and a low noise amplifier;

a variable capacitor means for tuning the patch antenna to a desired center frequency;

a sensor to produce a feedback signal indicative of an actual center frequency of the patch antenna; and

a controller to select a capacitance value of the variable capacitor means based on the feedback signal to maintain the patch antenna tuned to the desired center frequency.

14. The wireless system as recited in claim 13 wherein the variable capacitor means comprises:

a plurality of fixed capacitors arranged in parallel; and

a plurality of micro-electromechanical system (MEMS) switches associated with each of the plurality of fixed capacitors.

15. The wireless system as recited in claim 13 wherein the variable capacitor means comprises:

a micro-electromechanical system (MEMS) capacitor comprising a fixed lower plate and a flexible upper plate.

16. The wireless system as recited in claim 13 wherein the sensor comprises one of a pick-up coil and a directional coupler.

17. The wireless system as recited in claim 13 further comprising a look-up table associated with the controller to select a capacitance value of the variable capacitor means.

18. The wireless system of claim 13 wherein said wireless system comprises a cell phone.

19. An apparatus comprising:

an antenna,

a variable micro-electromechanical capacitor means to tune the antenna frequency;

a controller to operatively connected to the variable micro-electromechanical capacitor means to select a capacitance value to tune the antenna to a desired center frequency.

20. The apparatus of claim 19, wherein the variable micro-electromechanical capacitor means comprises a micro-electromechanical system (MEMS) capacitor comprising a fixed lower plate and a flexible upper plate.

21. The apparatus as recited in claim 19, wherein the variable micro-electromechanical capacitor means comprises:

a plurality of fixed capacitors arranged in parallel; and

a plurality of micro-electromechanical system (MEMS) switches associated with each of the plurality of fixed capacitors.

22. The apparatus as recited in claim 19 further comprising:

means for determining a power level radiated from the antenna operatively connected to the controller to determine the real-time center frequency of the antenna.

23. The apparatus as recited in claim 22, wherein the means for determining power level comprises a sensor in proximity of the antenna arranged in a feed-back loop to the controller.

24. The apparatus as recited in claim 22, wherein the means for determining power level comprises a power amplifier delivering power to the antenna and a signal to the controller proportional to delivered power.