Methods and apparatus for controlling tunable antenna systems

• US 9,041,617 B2
• Filed: 12/20/2011
• Issued: 05/26/2015
• Est. Priority Date: 12/20/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Sorensen, Robert S., Li, Qingxiang, Mow, Matthew A., Kim, Jinku
• Primary Examiner(s): Levi, Dameon E
• Assistant Examiner(s): Dawkins, Collin
• Application Number:
  US13/332,193
• Publication Number:
  US 20130154897A1
• Time in Patent Office: 1,253 Days
• Field of Search: 343/850, 343/861, 343/745
• US Class Current: 343/850
• 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;

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;

a voltage regulating circuit in the control circuit;

a comparator circuit in the control circuit; and

a counter circuit in the control circuit that has a control input that is coupled to the comparator circuit and has 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, the second control signal at the output of the counter circuit is proportional to the count associated with the counter circuit, and the antenna tuning element is placed in an operating state to tune the antenna to a selected frequency based on the count as identified by 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 voltage regulating circuit receives the first control signal and generates corresponding first and second voltage signals.

4. The antenna defined in claim 3, wherein the comparator circuit receives the first and second voltage signals, drives its output high when the first voltage signal exceeds the second voltage signal, and drives its output low when the second voltage signal exceeds the first voltage signal.

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

6. The antenna defined in claim 5, wherein the antenna tuning element further comprises a plurality of capacitive structures couple to respective ports of the radio-frequency switching circuitry.

7. The antenna defined in claim 5, wherein the antenna tuning element further comprises a plurality of inductive structures coupled to respective ports of the radio-frequency switching circuitry.

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

9. 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.

10. 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 first and second antenna feed lines, the control circuitry has first and second terminals, the first terminal is coupled directly to the first antenna feed line via a first inductor, the second terminal is coupled directly to the second antenna feed line via a second inductor, and 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 first antenna feed line, wherein the control circuitry toggles the control signal a predetermined number of times and the antenna tuning circuit includes a counter circuit; and

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.

11. The method defined in claim 10, wherein supplying the control signal to the antenna tuning circuit via the first antenna feed line comprises supplying the control signal to the antenna tuning circuit via the first antenna feed line during power-on-reset operations.

12. The method defined in claim 10 further comprising:

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

13. The method defined in claim 10, 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.

14. 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;

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;

a voltage regulating circuit in the control circuit that receives the first control signal and generates corresponding first and second voltage signals and a power supply voltage;

a comparator circuit in the control circuit that is powered by the power supply voltage; and

a counter circuit in the control circuit that is configured to start its count when the power supply voltage is above a predetermined threshold and increment its count in response to detecting a transition at its control input, wherein the antenna tuning element is placed in an operating state to tune the antenna to a selected frequency based on the count of the counter circuit.