Closed loop aperture tunable antenna

1. An apparatus comprising:

a radio frequency (RF) antenna circuit;

an antenna aperture tuning circuit;

an antenna impedance measurement circuit; and

a processor circuit electrically coupled to the tunable antenna aperture circuit and the impedance measurement circuit, wherein the processor circuit is configured to execute computer instructions stored in memory to:

set the antenna aperture tuning circuit to an antenna aperture tuning state according to one or more parameters of an RF communication network, wherein the one or more parameters of the RF communication network include a radio access technology (RAT) of the RF communication network, a channel of the RF communication network, or bandwidth of the RF communication network;

recurrently initiate the measurement of antenna impedance according to a specified schedule to obtain an antenna impedance; and

change the antenna aperture tuning state according to the determined antenna impedance.

2. The apparatus of claim 1 , wherein the antenna aperture tuning circuit includes one or more of:

an inductor coupled to the RF antenna circuit by an RF switch, a capacitor coupled to the RF antenna circuit by an RF switch, at least a first antenna radiating element coupled to a second antenna radiating element by an RF switch, an antenna radiating element coupled to a circuit ground by an RF switch; and

wherein the processor circuit is configured to set the antenna aperture tuning state by configuring one or more RF switches of the antenna aperture tuning circuit.

3. The apparatus of claim 1 , wherein the antenna aperture tuning circuit includes one or more of:

at least a first antenna radiating element coupled to a second antenna radiating element by a tunable capacitor; and

an antenna radiating element coupled to a circuit ground by a tunable capacitor; and

wherein the processor circuit is configured to set the antenna aperture tuning state by setting the capacitance value of one or more tunable capacitors.

4. The apparatus of claim 1 , including an impedance matching circuit electrically coupled to the RF antenna circuit, wherein the processor circuit is configured to change impedance of the impedance matching circuit to change transducer gain of the RF antenna circuit when the antenna aperture tuning state is set to the antenna aperture tuning state indicated by the antenna impedance.

5. The apparatus of claim 1 , including a memory circuit configured to store a lookup table that includes antenna aperture tuning states indexed according to antenna impedance, wherein the processor circuit is configured to set the antenna aperture tuning state using the lookup table.

6. The apparatus of claim 1 , including an adjustable capacitor electrically coupled between one of a radiating element and circuit ground, or a first radiating element and a second radiating element, wherein the processor circuit is configured to set the antenna aperture tuning state by changing a capacitance value of the adjustable capacitor.

7. The apparatus of claim 1 , including a transmit power measurement circuit configured to determine a measure of transmit power, and wherein the processor circuit is configured to initiate a measurement of transmit power, and initiate the antenna impedance measurement conditional upon the measurement of transmit power satisfying a specified measurement transmit power threshold.

8. The apparatus of claim 1 , wherein the antenna impedance measurement circuit is configured to determine magnitude and phase of a forward signal and a reverse signal of a transmit signal, and wherein the processor circuit is configured to determine the antenna impedance measurement using a difference in phase between the forward signal and the reverse signal, and a ratio including the magnitudes of the forward signal and the reverse signals.

9. The apparatus of claim 1 , wherein the processor circuit is configured to set the aperture tuning circuit to an antenna aperture tuning state and initiate the measurement of antenna impedance when detecting a change in the one or more parameters of the RF communication network.

10. The apparatus of claim 1 , wherein the antenna tuning circuit includes a first tuning port coupled to the RF antenna circuit at a first RF coupling location and a second tuning port coupled to the RF antenna circuit at a second RF coupling location, the tuning ports each including an RF switch, and wherein the processor circuit is configured to set the antenna aperture tuning state by configuring the RF switches of the first tuning port and second tuning port.

11. A computer readable storage medium including instructions, that when performed by processing circuitry of an RF communication device, cause the RF communication device to perform acts comprising:

setting an antenna aperture tuning state according to one or more parameters of the RF communication network, wherein the one or more parameters of the RF communication network include a radio access technology (RAT) of the RF communication network, a channel of the RF communication network, or bandwidth of the RF communication network:

determining antenna impedance; and

changing the antenna aperture tuning state according to the determined antenna impedance by one or more of:

changing an RF coupling state of a first antenna radiating element to a second radiating element, changing an RF coupling state of an antenna radiating element to ground, changing an RF coupling state of an antenna radiating element to an inductor of an antenna circuit of the RF circuitry, changing an RF coupling state of an antenna radiating element to a capacitor of the antenna circuit, and changing an RF coupling location of a ground leg of an RF antenna circuit of the RF circuitry.

12. The computer readable storage medium of claim 11 , including instructions that cause the RF communication device to perform acts comprising tuning an impedance matching circuit to change transducer gain of an RF antenna circuit of the RF circuitry in addition to changing the antenna aperture tuning state.

13. The computer readable storage medium of claim 11 , including instructions that cause the RF communication device to perform acts comprising changing the antenna aperture tuning state by identifying an antenna aperture tuning state using a lookup table that includes specified antenna aperture tuning states indexed according to antenna impedance, and setting the antenna aperture tuning state to a specified antenna aperture tuning state identified using the lookup table.

14. The computer readable storage medium of claim 11 , including instructions that cause the RF communication device to perform acts comprising setting the antenna aperture tuning state by adjusting a capacitance value of a capacitor, wherein the capacitor is electrically coupled between one of a radiating element and circuit ground, or a first radiating element and a second radiating element.

15. The computer readable storage medium of claim 11 , including instructions that cause the RF communication device to perform acts comprising determining magnitude of transmit power, wherein the determining antenna impedance is conditional upon the determined magnitude of transmit power satisfying a specified threshold magnitude value.

16. The computer readable storage medium of claim 11 , including instructions that cause the RF communication device to perform acts comprising determining magnitude and phase of a transmit signal from a forward direction and a reverse direction, and determining the antenna impedance using a difference in phase between the transmit signal in the forward direction and the reverse direction, and a ratio including the magnitudes of the transmit signal in the forward direction and the reverse direction.

17. A method of operating radio frequency (RF) circuitry to communicate via an RF communication network, the method comprising:

setting an antenna aperture tuning state according to parameters of the RF communication network,

determining antenna impedance:

selecting an antenna aperture tuning state using a lookup table that includes antenna aperture tuning states indexed according to antenna impedance; and

measuring the antenna impedance and setting the aperture tuning circuit to the selected antenna aperture tuning state when detecting a change in one or more parameters of the RF communication network.