Simple automatic antenna tuning system and method

• US 9,002,278 B2
• Filed: 02/29/2012
• Issued: 04/07/2015
• Est. Priority Date: 02/29/2012
• Status: Active Grant

• Current Assignee: HTC Corporation
• Original Assignee: HTC Corporation
• Inventors: Anderson, William David
• Primary Examiner(s): Milord, Marceau
• Application Number:
  US13/408,719
• Publication Number:
  US 20130225088A1
• Time in Patent Office: 1,133 Days
• Field of Search: 455/62, 455/73, 455/82, 455/553.1, 455/276.1, 455/80, 455/88, 455/575.5, 455/550.1, 455/77, 455/192.2, 455/83, 343/700.MS, 343/767, 343/372, 343/860
• US Class Current: 455/62
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H
• CPC Class Codes: H04B 1/163 Special arrangements for the reduction of the damping of resonant circuits of receivers amplifiers H03F; negative impedance networks for line transmission systems H04B3/16
• CPC Class Codes: H04B 17/12 of transmit antennas, e.g. of the amplitude or phase
• CPC Class Codes: H04B 17/30 of propagation channels

Abstract

Embodiments of a method for tuning the resonant frequency of an antenna in a wireless communication device are disclosed, along with embodiments of a wireless communication device using such a method. Embodiments sense the out-of-band impedance of the antenna, which comprises an antenna element and selectively adjustable impedance disposed between the antenna element and a ground plane of the wireless device, and adjust the selectively adjustable impedance to achieve a desired resonant frequency of the antenna. Embodiments separate an antenna signal into an in-band signal and out-of-band impedance, generate an error signal related to the out-of-band impedance, apply the error signal to a controller circuit configurable to generate an impedance error signal representing the change in antenna impedance, and apply the impedance error signal to the selectively adjustable impedance. Embodiments of a method and electronic circuit for determining the change in impedance of an antenna are also disclosed.

Claims

1. A method for tuning the resonant frequency of an antenna in a wireless communication device, comprising the steps of:

sensing the out-of-band impedance of the antenna, the antenna comprising an antenna element and a selectively adjustable impedance disposed between the antenna element and a ground plane of the wireless device; and

adjusting the selectively adjustable impedance to achieve a desired resonant frequency of the antenna, wherein the sensing step further comprises;

separating an antenna signal into an in-band antenna signal and the out-of-band antenna impedance;

generating an error signal related to the out-of-band impedance; and

applying the error signal to a controller circuit configurable to generate an impedance error signal.

2. The method of claim 1 wherein the antenna signal comprises a signal originating from a source outside of the wireless device that is received by the antenna.

3. The method of claim 1 wherein the antenna signal comprises a portion of a signal applied to the antenna by a transmitter of the wireless device.

4. The method of claim 1 wherein:

the generating step further comprises applying the out-of-band antenna impedance to an oscillator; and

the error signal is a frequency error signal.

5. The method of claim 1 wherein the applying step further comprises applying the impedance error signal to the selectively adjustable impedance.

6. The method of claim 1 wherein the out-of-band impedance comprises the combination of the actual load impedance of the antenna and the selectively adjustable impedance.

7. The method of claim 1 wherein the selectively adjustable impedance is a variable reactance.

8. The method of claim 1 wherein the selectively adjustable impedance is disposed substantially away from the feed point of the antenna.

9. The method of claim 1 wherein the desired resonant frequency is a frequency on which Global Positioning System (GPS) signals are transmitted.

10. The method of claim 1 wherein the desired resonant frequency is a frequency used during two-way wireless communications.

11. A method for determining the change in impedance of an antenna in a wireless communication device, comprising the steps of:

separating an antenna signal into an in-band antenna signal and an out-of-band antenna impedance;

generating an error signal related to the out-of-band antenna impedance; and

applying the error signal to a controller circuit configurable to generate a signal representing the change in impedance of the antenna.

12. The method of claim 11 wherein the antenna signal comprises a signal originating from a source outside of the wireless communication device that is received by the antenna.

13. The method of claim 11 wherein the antenna signal comprises a portion of a signal applied to the antenna by a transmitter of the wireless communication device.

14. The method of claim 11 wherein:

the generating step further comprises applying the out-of-band antenna impedance to an oscillator; and

the error signal is a frequency error signal.

15. An electronic circuit for determining the change in impedance of an antenna in a wireless communication device, comprising:

a filter operably connected to the antenna, wherein the filter comprises a diplexer that separates an antenna signal into an in-band antenna signal and an out-of-band antenna impedance;

an oscillator operably connected to the filter, said oscillator capable of generating a frequency error signal related to the out-of-band antenna impedance; and

a controller operably connected to the oscillator, said controller configurable to generate a signal related to the change in impedance of the antenna in proportion to the frequency error signal.

16. The electronic circuit of claim 15 wherein the out-of-band antenna impedance comprises the combination of the actual antenna load impedance and a selectively adjustable impedance.

17. The electronic circuit of claim 15 wherein the oscillator comprises a radio frequency (RF) crystal oscillator.

18. The electronic circuit of claim 15 wherein the oscillator comprises a radio frequency (RF) tank oscillator.

19. A wireless communication device comprising:

an antenna; and

an antenna tuning circuit, comprising;

a selectively adjustable impedance disposed between an element of the antenna and a ground plane of the wireless communication device;

a filter operably connected to the antenna, wherein the filter comprises a diplexer that separates an antenna signal into an in-band antenna signal and an out-of-band antenna impedance;

an oscillator operably connected to the filter, said oscillator capable of generating a frequency error signal related to the out-of-band antenna impedance; and

a controller operably connected to the oscillator, said controller configurable to generate an impedance error signal in proportion to the frequency error signal and to adjust the resonant frequency of the antenna to a desired resonant frequency by applying the impedance error signal to the selectively adjustable impedance.

20. The wireless communication device of claim 19 wherein the antenna signal comprises a signal originating from a source outside of the wireless device that is received by the antenna.

21. The wireless communication device of claim 19 further comprising a wireless communication transmitter, wherein the antenna signal comprises a portion of a signal applied to the antenna by the wireless communication transmitter.

22. The wireless communication device of claim 19 wherein the selectively adjustable impedance is a variable reactance.

23. The wireless communication device of claim 19 wherein the selectively adjustable impedance is disposed substantially away from the feed point of the antenna.

24. The wireless communication device of claim 19, further comprising a Global Positioning System (GPS) receiver, and wherein the desired resonant frequency is a frequency on which Global Positioning System (GPS) signals are transmitted.

25. The wireless communication device of claim 19, further comprising a wireless transceiver, and wherein the desired resonant frequency is a frequency used during two-way wireless communications.

26. The wireless communication device of claim 19, wherein the out-of-band antenna impedance comprises the combination of the actual antenna load impedance and a selectively adjustable impedance.