Adaptive antenna tuning based on measured antenna impedance

Patent metadata

Field	Value
Publication number	US-9825364-B2
Application number	US-201414303070-A
Country	US
Kind code	B2
Filing date	Jun 12, 2014
Priority date	Jun 12, 2014
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

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;
an impedance measurement circuit having a first terminal, a second terminal, a third terminal, and a fourth terminal, wherein the first terminal and third terminal are electrically connected to the antenna via the first antenna lead, and wherein the second terminal and fourth terminal are electrically connected to the antenna via the second antenna lead;
an impedance tuning circuit electrically connected to the antenna via a connection to the first antenna lead and a connection to the second antenna lead, wherein the impedance tuning circuit includes one or more reactive elements; and
a controller, wherein the controller operates to: (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.

2. The system of claim 1 , further comprising:
a transceiver electrically connected to the antenna through the impedance tuning circuit, wherein the transceiver uses the antenna to send and receive signals, and wherein the transceiver has a predetermined impedance; and
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 obtained measurement; (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.

3. 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, 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.

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, 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.

5. 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 impedance measurement circuit, the impedance tuning circuit, and the controller are disposed on the substrate.

6. The system of claim 5 , wherein the polymeric material has a concave surface and a convex surface.

7. The body-mountable device of claim 1 , wherein the impedance measurement circuit comprises a current source that conveys a test current through the antenna via the first terminal and second terminal.

8. The body-mountable device of claim 7 , wherein the impedance measurement circuit further comprises a current mirror that generates a replica current based on the test current.

9. The system of claim 1 , wherein the impedance measurement circuit comprises an amplifier, wherein the amplifier is electrically connected to the first antenna lead via the third terminal and electrically connected to the second antenna lead via the fourth terminal.

10. A method comprising:
obtaining, by an impedance measurement circuit, a measurement indicative of an impedance of an antenna, wherein the antenna has a first antenna lead and a second antenna lead, wherein the impedance measurement circuit has a first terminal and a third terminal electrically connected to the antenna via the first antenna lead, and wherein the impedance measurement circuit has a second terminal and a fourth terminal electrically connection to the antenna via the second antenna lead;
determining, based on the obtained measurement, an adjustment to an impedance tuning circuit, wherein the impedance tuning circuit is electrically connected to the antenna via a connection to the first antenna lead and a connection to the second antenna lead, and wherein the impedance tuning circuit includes one or more reactive elements; and
causing the impedance tuning circuit to make the determined adjustment.

11. The method of claim 10 , further comprising:
estimating an impedance of the antenna based on the obtained measurement;
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.

12. The method of claim 10 , wherein obtaining the measurement comprises:
conveying a test current through the antenna via the first terminal and second terminal.

13. The method of claim 12 , wherein obtaining the measurement further comprises:
measuring a voltage across the antenna via the third terminal and fourth terminal.

14. 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;
an impedance measurement circuit disposed on the substrate, wherein the impedance measurement circuit has a first terminal, a second terminal, a third terminal, and a fourth terminal, wherein the first terminal and third terminal are electrically connected to the antenna via the first antenna lead, and wherein the second terminal and fourth terminal are electrically connected to the antenna via the second antenna lead;
an impedance tuning circuit disposed on the substrate, wherein the impedance tuning circuit is electrically connected to the antenna via a connection to the first antenna lead and a connection to the second antenna lead, and wherein the impedance tuning circuit includes one or more reactive elements; and
a controller disposed on the substrate, wherein the controller operates to: (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.

15. The body-mountable device of claim 14 , further comprising:
a transceiver disposed on the substrate, wherein the transceiver is electrically connected to the antenna through the impedance tuning circuit, wherein the transceiver uses the antenna to send and receive signals, and wherein the transceiver has a predetermined impedance; and
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 obtained measurement; (ii) determining a target impedance of the impedance tuning circuit based on the predetermi

Assignees

• Verily Life Sciences Llc

Inventors

• O'Driscoll Stephen

Classifications

• H01Q1/273

  Adaptation for carrying or wearing by persons or animals · CPC title

• H01Q7/005 Primary

  with variable reactance for tuning the antenna · CPC title

• H04B2001/3866

  carried on the head · CPC title

• H04B2001/3861

  carried in a hand or on fingers · CPC title

• H04B2001/3855

  carried in a belt or harness · CPC title