Power amplifier with VSWR detection and correction feature
View Patent ↗A radio frequency (“RF”) power amplifier circuit as described herein is configured to detect and measure an output load mismatch and to adjust the operating characteristics of the RF power amplifier to reduce output signal distortion. The circuit includes a directional RF signal coupler that obtains a coupled reflected RF signal that is indicative of the output load mismatch. The coupled reflected RF signal is processed to generate one or more bias control signals for the RF power amplifier. In operation, a mismatch condition will result in a measurable coupled reflected RF signal and a corresponding reduction in output power from the RF power amplifier. Ultimately, the output power control mechanism strives to maintain the RF power amplifier within a linear operating range.
1. A radio frequency (“RF”) electronic device comprising:
a power amplifier configured to generate an RF output signal;
an RF coupler configured to obtain a coupled incident signal based upon said RF output signal and a coupled reflected signal based upon a reflected component of said RF output signal; and
an output power control architecture coupled to said power amplifier and to said RF coupler, said output power control architecture being configured to adjust operating characteristics of said power amplifier in response to said coupled reflected signal, wherein said output power control architecture generates a first adjustment signal from said coupled incident signal, said output power control architecture generates a second adjustment signal from said coupled reflected signal, and adjusts the operating characteristics of said power amplifier with a control signal obtained by subtracting said first adjustment signal and said second adjustment signal from a constituent component of an RF input to said power amplifier.
2. An RF electronic device according to claim 1 , said output power control architecture being configured to adjust output power of said power amplifier in response to said control signal.
3. An RF electronic device according to claim 2 , said output power control architecture being configured to adjust output power of said power amplifier to reduce amplitude of said reflected component.
4. An RF electronic device according to claim 1 , said output power control architecture being configured to adjust biasing of said power amplifier in response to said control signal.
5. An RF electronic device according to claim 1 , said output power control architecture being configured to adjust gain of said power amplifier in response to said control signal.
6. An RF electronic device according to claim 1 ,said output power control architecture being configured to adjust linearity of said power amplifier in response to said control signal.
7. An RF electronic device according to claim 1 , said power amplifier being a closed loop polar feedback amplifier, said constituent component of said RF input being an amplitude constituent of said RF input, and said power amplifier being configured to process a phase constituent of said RF input.
8. An RF electronic device according to claim 1 , said output power control architecture comprising an adjustable RF attenuator/gain element configured to adjust magnitude of said coupled reflected signal.
9. An RF electronic device according to claim 1 , said output power control architecture being configured to generate at least one control signal for said power amplifier, said at least one control signal having characteristics influenced by said coupled reflected signal.
10. A method of adjusting output power of a radio frequency (“RF”) power amplifier configured to generate an RF output signal, said method comprising:
obtaining a coupled incident signal based upon an incident component of said RF output signal;
obtaining a coupled reflected signal based upon a reflected component of the RF output signal;
generating a first adjustment signal from said coupled incident signal;
generating a second adjustment signal from said coupled reflected signal;
subtracting said first adjustment signal and said second adjustment signal from an amplitude constituent of an RF input signal, resulting in an adjusted amplitude constituent signal; and
adjusting operating characteristics of the RF power amplifier in response to said adjusted amplitude constituent signal.
11. A method according to claim 10 , wherein adjusting operating characteristics of the RF power amplifier comprises adjusting biasing of the RF power amplifier.
12. A method according to claim 10 , wherein adjusting operating characteristics of the RF power amplifier comprises adjusting gain of the RF power amplifier.
13. A method according to claim 10 , further comprising adjusting the magnitude of said coupled reflected signal.
14. A method according to claim 10 , further comprising generating at least one control signal for the RF power amplifier, said at least one control signal having characteristics influenced by said adjusted amplitude constituent signal.
15. A radio frequency (“RF”) electronic device comprising:
a power amplifier configured to generate an RF output signal from a phase constituent of an RF input signal;
an RF coupler configured to obtain a coupled incident signal based upon an incident component of said RF output signal, and a coupled reflected signal based upon a reflected component of said RF output signal;
a first amplitude detector coupled to said RF coupler, said first amplitude detector being configured to generate a first adjustment signal from said coupled reflected signal, said first adjustment signal being indicative of an output load mismatch;
a second amplitude detector coupled to said RF coupler, said second amplitude detector being configured to generate a second adjustment signal from said coupled incident signal;
a summer coupled to said first amplitude detector and to said second amplitude detector, said summer being configured to subtract said first adjustment signal and said second adjustment signal from an amplitude constituent of said RF input signal, resulting in an adjusted amplitude constituent signal; and
a bias signal generator coupled to said summer, said bias signal generator being configured to generate, in response to said adjusted amplitude signal, at least one bias control signal for said power amplifier.
16. An RF electronic device according to claim 15 , further comprising an RF antenna coupled to said power amplifier, said RF antenna representing a potentially variable output load for said power amplifier.
17. An RF electronic device according to claim 15 , said at least one bias control signal influencing output power of said power amplifier.