Method for simplified closed-loop antenna tuning

Patent metadata

Field	Value
Publication number	US-9401738-B2
Application number	US-201514799413-A
Country	US
Kind code	B2
Filing date	Jul 14, 2015
Priority date	Jul 15, 2014
Publication date	Jul 26, 2016
Grant date	Jul 26, 2016

Abstract

A method of closed-loop antenna tuning (CLAT) search strategy based on maximum Relative Transducer Gain (RTG) is proposed. A search region that account for TX input mismatch and forward voltage gain is pre-computed. The search region that is independent of antenna load can be pre-computed to reduce the computation complexity. The Maximum RTG is searched by estimating antenna S-parameters corresponding to a good load match. The search is conducted between the peak forward voltage gain and the best load match. Global optimal with reasonable RTG can be found with limited number of iterations. The transmitter search region can further be constrained by the receiver path mismatching.

First claim

What is claimed is:

1. A method comprising:
(a) constructing a Smith chart by a wireless device for an antenna with an antenna tuner having S-parameters;
(b) determining a search region based on an S-parameter on the Smith chart that satisfies a condition, wherein the search region is pre-calculated independent from a load condition of the antenna tuner;
(c) estimating a load reflection coefficient (Γ L ) of the antenna tuner; and
(d) searching a set of S-parameters that corresponds to a maximum relative transducer gain (RTG) of the antenna within the search region, wherein the search is conducted along a pre-defined search path located inside a final search region that is formed between a peak |S21| and Γ L * on the Smith chart.

2. The method of claim 1 , wherein an RTG value is defined as a ratio between an incident power to the antenna with the antenna tuner and an incident power to the antenna without the antenna tuner.

3. The method of claim 1 , wherein the S-parameter is S22.

4. The method of claim 1 , wherein the condition indicates an input reflection coefficient (Γin) of the antenna tuner is smaller than a threshold value.

5. The method of claim 1 , wherein the antenna tuner comprises a plurality of capacitors and a plurality of inductors, and wherein the S-parameters are functions of codewords representing settings of the capacitors and the inductors.

6. The method of claim 5 , wherein a reduced size lookup table (LUT) between the S-parameters and the codewords is constructed within the search region based on a pre-determined method.

7. The method of claim 6 , wherein the LUT size is further reduced by selecting points on or closest to the constant |S21| contours and equal S22 angles on the Smith chart.

8. The method of claim 1 , wherein the Γ L * is estimated based on measurements of an input reflection coefficient (Γin) of the antenna tuner.

9. The method of claim 8 , wherein a coupler and a detector are used to sample a forward path and a reverse path of radio signals for determining the input reflection coefficient (Γin) of the antenna tuner.

10. The method of claim 1 , wherein the search stops at the border of the search region if the Γ L * is located outside of the search region.

11. The method of claim 1 , wherein another simple gradient type search is used to refine the search after the pre-defined search path is completed.

12. The method of claim 1 , wherein the search region is further constrained by a receiver source mismatch condition and a receiver load mismatch condition.

13. The method of claim 1 , wherein a first search region is defined for a first carrier frequency, and wherein a second search region is defined for a second carrier frequency.

14. A wireless device, comprising:
a processor;
an antenna;
an antenna tuner having S-parameters, wherein the antenna tuner load is coupled to the antenna, and wherein the antenna tuner source is coupled to an RF transceiver;
a coupler and a detector that samples a forward path and a reverse path of radio signals to determine an input reflection coefficient; and
a control interface that controls settings of the antenna tuner by the processor via a digital baseband general purpose IO (DBB GPIO), wherein a pre-determined search region of an S-parameter on the Smith chart that satisfies a condition is stored in the processor, the said processor estimates a load reflection coefficient (Γ L ) of the antenna tuner, searches a set of S-parameters that corresponds to a maximum relative transducer gain (RTG) of the antenna within the search region, wherein the search region is pre-calculated independent from a load condition of the antenna tuner, and wherein the search is conducted along a search path located inside a final search region that is formed between a peak |S21| and Γ L * on the Smith chart.

15. The device of claim 14 , wherein an RTG value is defined as a ratio between an incident power to the antenna with the antenna tuner and an incident power to the antenna without the antenna tuner.

16. The device of claim 14 , wherein the condition indicates an input reflection coefficient (Γin) of the antenna tuner is smaller than a threshold value.

17. The device of claim 14 , wherein the antenna tuner comprises a plurality of capacitors and a plurality of inductors, and wherein the S-parameters are functions of codewords representing settings of the capacitors and the inductors.

18. The device of claim 17 , wherein a reduced size lookup table (LUT) between the S-parameters and the codewords is constructed within the search region.

19. The device of claim 18 , wherein the LUT size is further reduced by selecting points on or closest to constant |S21| contours and equal S22 angles on the Smith chart.

20. The device of claim 14 , wherein the Γ L * is estimated based on measurements of an input reflection coefficient (Γin) of the antenna tuner.

21. The device of claim 14 , wherein the search stops at the border of the search region if the IV is located outside of the search region.

22. The device of claim 14 , wherein the search region is further constrained by a receiver source mismatch condition and a receiver load mismatch condition.

23. The device of claim 14 , wherein a first search region is defined for a first carrier frequency, and wherein a second search region is defined for a second carrier frequency.

Assignees

• Mediatek Singapore Pte Ltd

Inventors

• Wang James June-Ming
• Zhou Qiang
• Hsu Yungping
• Tenbroek Bernard Mark

Classifications

• H01Q5/335

  at the feed, e.g. for impedance matching · CPC title

• H04B1/40 Primary

  Circuits · CPC title

• H03H7/38 Primary

  Impedance-matching networks · CPC title

• H04B1/0458

  Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages (matching circuits in general H03H) · CPC title

• H04B1/18

  Input circuits, e.g. for coupling to an antenna or a transmission line (coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H) · CPC title