Methods for reconfiguring directional couplers in an RF transceiver
Provided herein are methods of reconfiguring directional couplers in an RF transceiver. The methods can include designing and reconfiguring the directional couplers to provide high directivity and a desired coupling factor using configurable capacitors to effect a mutual coupling and using lumped components or delay lines to effect a phase shift. The reconfigurable directional couplers can be designed for multi-band operation with an adjustable coupling factor conducive to semiconductor process integration. The reconfigurable directional couplers can have variable phase shifters to achieve a desired level of directivity in the coupler. In various examples, the methods include monitoring the frequency of power signals received by the reconfigurable directional couplers, and adjusting the configurable capacitors and/or variable phase shifters to maintain desired directivity and coupling factors over multi-band operation of the reconfigurable directional couplers.
1. A method of configuring a reconfigurable directional coupler, the method comprising:
selecting a desired coupling factor for the reconfigurable directional coupler;
configuring, under control of a processor, first and second adjustable capacitor arrays electrically connected between a power input port and a coupled port of the reconfigurable directional coupler and between a power output port and an isolation port of the reconfigurable directional coupler, respectively, to provide the desired coupling factor;
selecting, based on a frequency band of operation, a first phase shift value of a first adjustable phase shifter electrically connected between the power input port and the power output port and configuring, with the processor, the first adjustable phase shifter to have the first phase shift value; and
selecting a second phase shift value of a second adjustable phase shifter electrically connected between the coupled port and the isolation port and configuring, with the processor, the second adjustable phase shifter to have the second phase shift value such that, in response to an input signal received at the input port in the frequency band of operation, a combined signal present at the isolation port includes two signals having phases that are offset from one another.
2. The method of claim 1 wherein selecting the first and second phase shift values includes selecting the first and second phase shift values such that the phases of the two signals are complementary.
3. The method of claim 1 wherein the selecting the first and second phase shift values includes selecting the first and second phase shift values such that a difference between the phases of the two signals is approximately 180 degrees.
4. The method of claim 1 wherein selecting the first phase shift value and configuring the first adjustable phase shifter includes adjusting at least one frequency-dependent component of the first adjustable phase shifter such that, for the frequency band of operation, the first adjustable phase shifter has the first phase shift value.
5. The method of claim 4 wherein adjusting the at least one frequency-dependent component of the first adjustable phase shifter includes selectively connecting at least one switchable capacitor or inductor from the first adjustable phase shifter.
6. The method of claim 4 wherein selecting the second phase shift value and configuring the second adjustable phase shifter includes adjusting at least one frequency-dependent component of the second adjustable phase shifter such that, for the frequency band of operation, the second adjustable phase shifter has the second phase shift value.
7. The method of claim 6 wherein adjusting the at least one frequency-dependent component of the second adjustable phase shifter includes selectively connecting at least one switchable capacitor or inductor from the second adjustable phase shifter.
8. The method of claim 1 wherein selecting the desired coupling factor includes selecting a first mutual coupling level between the power input port and the coupled port of the reconfigurable directional coupler and selecting a second mutual coupling level between the power output port and the isolation port of the reconfigurable directional coupler.
9. The method of claim 8 wherein configuring first and second adjustable capacitor arrays includes adjusting a first capacitance value of the first adjustable capacitor array to provide the first mutual coupling level and adjusting a second capacitance value of the second adjustable capacitor array to provide the second mutual coupling level.
10. The method of claim 9 wherein adjusting the first capacitance value includes selectively connecting at least one of a first plurality of switchable capacitors between the power input port and the coupled port using a first pair of switches.
11. The method of claim 10 wherein adjusting the second capacitance value includes selectively connecting at least one of a second plurality of switchable capacitors between the power output port and the isolation port using a second pair of switches.
12. The method of claim 6 further comprising determining whether the frequency band of operation has changed.
13. The method of claim 12 further comprising maintaining a state of the reconfigurable directional coupler responsive to a determination that the frequency band of operation has not changed.
14. The method of claim 12 wherein responsive to a determination that the frequency band of operation has changed to an updated frequency band of operation, the method further comprises:
re-adjusting the least one frequency-dependent component of the first adjustable phase shifter such that, for the updated frequency band of operation, the first adjustable phase shifter has the first phase shift value; and
re-adjusting the least one frequency-dependent component of the second adjustable phase shifter such that, for the updated frequency band of operation, the second adjustable phase shifter has the second phase shift value.
15. The method of claim 12 wherein responsive to a determination that the frequency band of operation has changed to an updated frequency band of operation, the method further comprises:
re-adjusting the least one frequency-dependent component of the first adjustable phase shifter such that, for the updated frequency band of operation, the first adjustable phase shifter has a third phase shift value; and
re-adjusting the least one frequency-dependent component of the second adjustable phase shifter such that, for the updated frequency band of operation, the second adjustable phase shifter has a fourth phase shift value, the third and fourth phase shift values being selected such that the combined signal present at the isolation port responsive to the input signal in the updated frequency band of operation being received at the power input port includes the two signals having phases that are offset from one another.
16. The method of claim 12 wherein determining whether the frequency band of operation has changed includes monitoring a frequency of a coupled signal present at the coupled port responsive to the input signal being received at the power input port.
17. A method of operating a wireless device, the method comprising:
selecting a desired coupling factor for a reconfigurable directional coupler of the wireless device;
configuring, under control of a processor, first and second adjustable capacitor arrays electrically connected between a power input port and a coupled port of the reconfigurable directional coupler and between a power output port and an isolation port of the reconfigurable directional coupler, respectively, to provide the desired coupling factor;
receiving an input signal at a power input port of the reconfigurable directional coupler;
capacitively coupling a portion of the input signal via the first and second adjustable capacitor arrays to provide a coupled signal at the coupled port;
monitoring, with a sensor connected to the coupled port, the coupled signal to determine a frequency band of the input signal;
adjusting, based on the frequency band of the input signal and under control of the processor, a first phase shift value of a first adjustable phase shifter connected between the power input port and the power output port of the reconfigurable directional coupler; and
adjusting, under control of the processor, a second phase shift value of a second adjustable phase shifter connected between the coupled port and the isolation port of the reconfigurable directional coupler such that, in response to the input signal received at the power input port, a combined signal present at the isolation port includes two signals having phases that are offset from one another by approximately 180 degrees.
18. The method of claim 17 further comprising generating a transmit signal and amplifying the transmit signal using a power amplifier to provide the input signal to the power input port.
19. The method of claim 17 wherein adjusting the first phase shift value of the first adjustable phase shifter includes selectively connecting at least one first switchable capacitor between the power input port and the power output port of the reconfigurable directional coupler, and adjusting the second phase shift value of the second adjustable phase shifter includes selectively connecting at least one second switchable capacitor between the coupled port and the isolation port of the reconfigurable directional coupler.
20. A method of configuring a reconfigurable directional coupler, the method comprising:
selecting a desired coupling factor for the reconfigurable directional coupler;
configuring, under control of a processor, first and second adjustable capacitor arrays electrically connected between a power input port and a coupled port of the reconfigurable directional coupler and between a power output port and an isolation port of the reconfigurable directional coupler, respectively, to provide the desired coupling factor;
receiving an input signal at a power input port of the reconfigurable directional coupler;
capacitively coupling a portion of the input signal via the first and second adjustable capacitor arrays to provide a coupled signal at the coupled port;
monitoring, with a sensor connected to the coupled port, the coupled signal to determine a frequency band of the input signal;
adjusting, based on the frequency band of the input signal and under control of the processor, a first phase shift value of a first adjustable phase shifter connected between the power input port and the power output port of the reconfigurable directional coupler; and
adjusting, under control of the processor, a second phase shift value of a second adjustable phase shifter connected between the coupled port and the isolation port of the reconfigurable directional coupler such that, in response to the input signal being received at the power input port, a combined signal present at the isolation port includes two signals having phases that are offset from one another by approximately 180 degrees.