Adaptive antenna tuning based on measured antenna impedance

Patent metadata

Field	Value
Publication number	US-10158174-B2
Application number	US-201715816237-A
Country	US
Kind code	B2
Filing date	Nov 17, 2017
Priority date	Jun 12, 2014
Publication date	Dec 18, 2018
Grant date	Dec 18, 2018

Abstract

A system includes an antenna, an impedance measurement circuit, an impedance tuning circuit, and a controller. The impedance measurement circuit can include a test current source that conveys a test current through the antenna, and a voltage sensor that measure a voltage across the antenna while the test current is conveyed through the antenna. The impedance tuning circuit can be coupled to the antenna leads and can include one or more reactive elements that can be selectively coupled to the antenna, or otherwise adjusted, to effect adjustment of the impedance connected to the antenna. The controller can: (i) use the impedance measurement circuit to obtain a measurement indicative of an impedance of the antenna; (ii) determine an adjustment to the impedance tuning circuit based on the obtained measurement; and (iii) cause the impedance tuning circuit to make the determined adjustment.

First claim

What is claimed is:

1. A system comprising:
an antenna having a first antenna lead and a second antenna lead;
a directional coupler comprising a first port, a second port, and a third port, wherein the first port is electrically connected to the first antenna lead and the second antenna lead, and wherein the directional coupler directs signals received at the first port to the second and third ports, directs signals received at the second port to the first port, and substantially isolates the second and third ports from each other;
an impedance tuning circuit electrically connected to the second port of the directional coupler, wherein the impedance tuning circuit includes one or more reactive elements;
a test signal measurement circuit electrically connected to the second port of the directional coupler;
a reflected signal measurement circuit electrically connected to the third port of the directional coupler; and
a controller, wherein the controller operates to: (i) receive, from the test signal measurement circuit, a test-signal measurement of a test signal applied to the antenna through the directional coupler; (ii) receive from the reflected signal measurement circuit a reflected-signal measurement of a reflected signal reflected from the antenna through the directional coupler in response to the test signal applied to the antenna; (iii) determine an adjustment to the impedance tuning circuit based on the test-signal measurement and the reflected-signal measurement; and (iv) cause the impedance tuning circuit to make the determined adjustment.

2. The system of claim 1 , further comprising:
a transceiver electrically connected to the second port of the directional coupler via the impedance tuning circuit, wherein the transceiver uses the antenna to send and receive signals, and wherein the transceiver has a predetermined impedance.

3. The system of claim 2 , wherein the controller determines the adjustment to the impedance tuning circuit by a process comprising: (i) estimating an impedance of the antenna based on the test-signal measurement, the reflected-signal measurement, and a predetermined impedance of the directional coupler; (ii) determining a target impedance of the impedance tuning circuit based on the predetermined impedance of the transceiver and the estimated impedance of the antenna; and (iii) determining one or more adjustments to the impedance tuning circuit based on the target impedance.

4. The system of claim 1 , wherein the controller makes the determined adjustment via one or more switches that selectively couple the one or more reactive elements to the antenna through the directional coupler, and wherein the one or more reactive elements include at least one of:
a shunt capacitor coupled across the antenna leads via at least one of the one or more switches;
a series capacitor coupled in series with one of the antenna leads via at least one of the one or more switches;
a shunt inductor coupled across the antenna leads via at least one of the one or more switches; or
a series inductor coupled in series with one of the antenna leads via at least one of the one or more switches.

5. The system of claim 1 , wherein the controller makes the determined adjustment via one or more switches that selectively couple the one or more reactive elements to the antenna through the directional coupler, and wherein the one or more reactive elements include multiple shunt capacitors having respective capacitances, wherein each of the multiple capacitors is coupled across leads of the antenna via a respective one of the one or more switches.

6. The system of claim 1 , further comprising:
a polymeric material formed to include a body-mountable surface; and
a substrate at least partially embedded within the polymeric material, wherein the antenna, the directional coupler, the test signal measurement circuit, the reflected signal measurement circuit, the impedance tuning circuit, and the controller are disposed on the substrate.

7. The system of claim 6 , wherein the body-mountable surface is an eye-mountable surface.

8. A method comprising:
measuring, by a test signal measurement circuit, a signal strength of a test signal applied to an antenna, wherein the test signal measurement circuit is electrically coupled between an impedance tuning circuit and a first port of a directional coupler;
measuring, by a reflected signal measurement circuit, a signal strength of a reflected signal from the antenna, wherein the reflected signal from the antenna results from the application of the test signal, wherein the reflected signal measurement circuit is electrically coupled to a second port of the directional coupler;
determining, based on the signal strength of the test signal applied to the antenna and the signal strength of the reflected signal from the antenna, an adjustment to the impedance tuning circuit, wherein the impedance tuning circuit is electrically connected to the antenna via the directional coupler, and wherein the impedance tuning circuit includes one or more reactive elements; and
causing the impedance tuning circuit to make the determined adjustment.

9. The method of claim 8 , wherein determining the adjustment to the impedance tuning circuit comprises:
estimating an impedance of the antenna based on the signal strength of the test signal applied to the antenna, the signal strength of the reflected signal from the antenna, and a predetermined impedance of the directional coupler;
determining a target impedance of the impedance tuning circuit based on the estimated impedance of the antenna and a predetermined impedance of a transceiver coupled to the antenna through the impedance tuning circuit; and
determining one or more adjustments to the impedance tuning circuit based on the target impedance.

10. A body-mountable device comprising:
a polymeric material formed to include a body-mountable surface;
a substrate at least partially embedded within the polymeric material;
an antenna disposed on the substrate, wherein the antenna has a first antenna lead and a second antenna lead;
a directional coupler comprising a first port, a second port, and a third port, wherein the first port is electrically connected to the first antenna lead and the second antenna lead;
an impedance tuning circuit disposed on the substrate, wherein the impedance tuning circuit is electrically connected to the second port of the directional coupler, wherein the impedance tuning circuit includes one or more reactive elements;
a test signal measurement circuit disposed on the substrate, wherein the test signal measurement circuit is electrically connected to the second port of the directional coupler;
a reflected signal measurement circuit disposed on the substrate, wherein the reflected signal measurement circuit is electrically connected to the third port of the directional coupler; and
a controller disposed on the substrate, wherein the controller operates to: (i) receive, from the test signal measurement circuit, a test-signal measurement of a test signal applied to the antenna through the directional coupler; (ii) receive from the reflected signal measurement circuit a reflected-signal measurement of a reflected signal reflected from the antenna through the directional coupler in response to the test signal applied to the antenna; (iii) determine an adjustment to the impedance tuning circuit based on the test-signal measurement and the reflected-signal measurement; and (iv) cause the impedance tuning circuit to make the determined adjustment.

11. The body-mountable device of claim 10 , wherein the body-mountable surface is an eye-mountable surface.

Assignees

• Verily Life Sciences Llc

Inventors

• O'Driscoll Stephen

Classifications

• 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

• H04B2001/3855

  carried in a belt or harness · 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

• G02C7/04

  Contact lenses for the eyes (disinfection or sterilisation of contact lenses A61L12/00) · CPC title

• H01Q7/005 Primary

  with variable reactance for tuning the antenna · CPC title