Methods and Apparatus for Controlling Tunable Antenna Systems

• US 20130154897A1
• Filed: 12/20/2011
• Published: 06/20/2013
• Est. Priority Date: 12/20/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Li, Qingxiang, Sorensen, Robert S., Mow, Matthew A., Kim, Jinku
• Granted Patent: US 9,041,617 B2
• Time in Patent Office: Days
• US Class Current: 343/861
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them
• CPC Class Codes: H01Q 5/314 using frequency dependent circuits or components, e.g. trap circuits or capacitors
• CPC Class Codes: H01Q 5/328 between a radiating element and ground
• CPC Class Codes: H01Q 5/335 at the feed, e.g. for impedance matching
• CPC Class Codes: H01Q 7/005 with variable reactance for tuning the antenna
• CPC Class Codes: H03J 2200/11 Cellular receiver, e.g. GSM, combined with a GPS receiver
• CPC Class Codes: H03J 3/20 of single resonant circuit by varying inductance only or capacitance only
• CPC Class Codes: H04B 1/40 Circuits

Abstract

An electronic device may include an adjustable power supply, at least one antenna, and associated antenna tuning circuitry. The antenna tuning circuitry may be an integral part of the antenna and may include a control circuit and at least one tunable element. The tunable element may include radio-frequency switches, continuously/semi-continuously adjustable components such as tunable resistors, inductors, and capacitors, and other load circuits that provide desired impedance characteristics. The power supply may provide power supply voltage signals to the antenna tuning circuitry via inductive coupling. The power supply voltage signals may be modulated according to a predetermined lookup table during device startup so that the control circuit is configured to generate desired control signals. These control signals adjust the tunable element so that the antenna can support wireless operation in desired frequency bands.

Claims

1. An antenna in an electronic device comprising:

an antenna feed that includes first and second antenna feed terminals;

a control circuit configured to receive a first control signal from the antenna feed and configured to generate a second control signal; and

an antenna tuning element having a first terminal coupled to the first antenna feed terminal, a second terminal coupled to the second antenna feed terminal, and a third terminal configured to receive the second control signal.

2. The antenna defined in claim 1 further comprising:

antenna resonating structures coupled to the antenna feed via at least a capacitor, wherein the first and second terminals of the antenna tuning element is coupled to the first and second antenna feed terminals via respective inductors.

3. The antenna defined in claim 1, wherein the control circuit includes a voltage regulating circuit configured to receive the first control signal and to generate corresponding first and second voltage signals.

4. The antenna defined in claim 3, wherein the control circuit further includes a comparator circuit configured to receive the first and second voltage signals, and wherein the comparator circuit is operable to drive its output high when the first voltage signal exceeds the second voltage signal and is operable to drive its output low when the second voltage signal exceeds the first voltage signal.

5. The antenna defined in claim 4, wherein the control circuit further includes a counter circuit having a control input that is coupled to the output of the comparator circuit and having an output on which the second control signal is provided, wherein the counter circuit is configured to increment its count in response to detecting a transition at its control input, and wherein the second control signal at the output of the comparator circuit is proportional to the count associated with the counter circuit.

6. The antenna defined in claim 1, wherein the antenna tuning element comprises radio-frequency switching circuitry.

7. The antenna defined in claim 6, wherein the antenna tuning element further comprises a plurality of capacitive structures couple to respective ports of the radio-frequency switching circuitry.

8. The antenna defined in claim 6, wherein the antenna tuning element further comprises a plurality of inductive structures coupled to respective ports of the radio-frequency switching circuitry.

9. The antenna defined in claim 1, wherein the antenna tuning element comprises a variable capacitor.

10. The antenna defined in claim 1 wherein the antenna comprises an antenna selected from the group consisting of:

a loop antenna, an inverted-F antenna, a patch antenna, a slot antenna, a planar inverted-F antenna, and a helical antenna.

11. A method for using an electronic device having control circuitry, transceiver circuitry, and an antenna, wherein the antenna is coupled to the transceiver circuitry via an antenna feed, wherein the control circuitry is coupled to the antenna feed, and wherein the antenna includes at least one antenna tuning circuit, the method comprising:

with the control circuitry, tuning the antenna to operate in a desired frequency band by supplying a control signal to the antenna tuning circuit via the antenna feed.

12. The method defined in claim 11, wherein supplying the control signal to the antenna tuning circuit via the antenna feed comprises supplying the control signal to the antenna tuning circuit via the antenna feed during power-on-reset operations.

13. The method defined in claim 11 further comprising:

with the control circuitry, supplying a power supply signal to the antenna tuning circuit via the antenna feed during normal operation.

14. The method defined in claim 11, wherein the control circuitry toggles the control signal a predetermined number of times and wherein the antenna tuning circuit includes a counter circuit, the method further comprising:

with the counter circuit, determining an amount by which the antenna is to be tuned by counting the number of times the control signal toggles.

15. The method defined in claim, wherein the antenna tuning circuit includes a control circuit and a tunable element, and wherein supplying the control signal to the antenna tuning circuit comprises configuring the control circuit to generate an additional control signal that adjusts the tunable element.

16. A method for using an electronic device having control circuitry that supplies a direct current (DC) control signal, transceiver circuitry, and an antenna, wherein the antenna is coupled to the transceiver circuitry via an antenna feed, wherein the control circuitry is coupled to the antenna feed, and wherein the antenna includes at least one antenna tuning circuit, the method comprising:

tuning the antenna by modulating the DC control signal to adjust the antenna tuning circuit.

17. The method defined in claim 16, wherein modulating the DC control signal comprises varying the DC control signal between first and second voltage levels with the control circuitry.

18. The method defined in claim 17, wherein varying the DC control signal between the first and second voltage levels comprises generating a DC control signal having a predetermined number of pulses with the control circuitry.

19. The method defined in claim 18, wherein the antenna tuning circuit includes a counter circuit, the method further comprising:

with the counter circuit, determining an amount by which the antenna is to be tuned by counting the number of pulses in the DC control signal.

20. The method defined in claim 16, wherein the electronic device is configured to operate in a given radio-frequency band, the method further comprising:

selecting a modulation scheme for modulating the DC control signal based on the given radio-frequency band by referring to a predetermined lookup table that is stored in the control circuitry.