Configurable load impedance for power amplifier predistortion calibration
An integrated circuit radio transceiver and method therefor includes an integrated circuit radio transceiver operable to provide specified gain levels and transmit path filter responses to correspond with a selected power spectral density mask. Changes in gain may be provided solely digital gain changes or may include analog gain module gain changes. A transmitter selects from one of at least three masks to reduce or eliminate spectral regrowth out of band to satisfy EVM requirements. Circuitry is provided to allow a transceiver to determine in advance what pre-distortion compensation settings are required for the various gain settings.
1. A method for operating a wireless device comprising:
producing an outgoing Radio Frequency (RF) signal;
receiving, via a receive path, a coupled copy of the outgoing RF signal;
determining a plurality of pre-distortion settings based upon the coupled copy of the outgoing RF signal and respective transmit path gain settings;
producing a transmit RF signal by applying a selected pre-distortion setting from the plurality of pre-distortion settings;
receiving a representation of the transmit RF signal via a feedback path that differs from the receive path;
adjusting transmit path gain settings based upon the representation of the transmit RF signal; and
selecting a differing pre-distortion setting from the plurality of pre-distortion settings based upon the adjusted transmit path gain settings.
2. The method of claim 1 , further comprising coupling the transmit RF signal to a lumped circuit element to create the representation of the transmit RF signal.
3. The method of claim 1 , wherein determining a plurality of pre-distortion settings based upon the coupled copy of the outgoing RF signal further comprises considering a plurality of orthogonal frequency division multiplexing (OFDM) tones of the outgoing RF signal.
4. The method of claim 1 , wherein adjusting analog gain path settings comprises adjusting a gain setting of at least one of a filter, a mixer, and a signal amplifier of an RF transmit path.
5. The method of claim 1 :
further comprising forming the RF signal to support orthogonal frequency division multiplexing (OFDM) modulation; and
wherein the pre-distortion settings are determined based upon OFDM modulation parameters.
6. The method of claim 1 :
further comprising forming the RF signal to support MIMO communications; and
wherein the pre-distortion settings are determined based upon multiple in multiple out (MIMO) communication parameters.
7. The method of claim 1 further comprising determining a plurality of power spectral density masks to employ as the plurality of pre-determined pre-distortion settings.
8. The method of claim 1 wherein the transmit path gain settings comprise at least one of digital gain settings and analog gain settings.
9. A wireless device comprising:
a Radio Frequency (RF) transceiver; and
processing circuitry coupled to the RF transceiver, the RF transceiver and processing circuitry configured to:
receive, via a receive path, a coupled copy of an outgoing Radio Frequency (RF) signal produced by the RF transceiver;
determine a plurality of pre-distortion settings based upon the coupled copy of the outgoing RF signal and respective transmit path gain settings;
produce a transmit RF signal by applying a selected pre-distortion setting from the plurality of pre-distortion settings;
receive a representation of the transmit RF signal via a feedback path that differs from the receive path;
adjust transmit path gain settings based upon the representation of the transmit RF signal; and
select a differing pre-distortion setting from the plurality of pre-distortion settings based upon the adjusted transmit path gain path settings.
10. The wireless device of claim 9 , wherein the RF transceiver and processing circuitry are configured to couple the transmit RF signal to a lumped circuit element to create the representation of the transmit RF signal.
11. The wireless device of claim 9 , wherein the RF transceiver and processing circuitry are configured to determine the plurality of pre-distortion settings based upon the coupled copy of the outgoing RF signal and considering a plurality of orthogonal frequency division multiplexing (OFDM) tones of the outgoing RF signal.
12. The wireless device of claim 9 , wherein the RF transceiver and processing circuitry are configured to adjust a gain setting of at least one of a filter, a mixer, and a signal amplifier of an RF transmit path.
13. The wireless device of claim 9 , wherein the RF transceiver and processing circuitry are configured to:
form the RF signal to support orthogonal frequency division multiplexing (OFDM) modulation; and
determine the pre-distortion settings based upon OFDM modulation parameters.
14. The wireless device of claim 9 , wherein the RF transceiver and processing circuitry are configured to:
form the RF signal to support multiple in multiple out (MIMO) communications; and
determine the pre-distortion settings based upon MIMO communication parameters.
15. The wireless device of claim 9 , wherein the RF transceiver and processing circuitry are configured to determine a plurality of power spectral density masks to employ as the plurality of pre-determined pre-distortion settings.
16. The wireless device of claim 9 , wherein the transmit path gain settings comprise at least one of digital gain settings and analog gain settings.
17. A wireless device comprising:
a Radio Frequency (RF) transceiver; and
processing circuitry coupled to the RF transceiver, the RF transceiver and processing circuitry configured to:
receive, via a receive path, a coupled copy of an outgoing Radio Frequency (RF) signal produced by the RF transceiver;
determine a plurality of pre-distortion settings based upon the coupled copy of the outgoing RF signal and a transmit mode of operation;
produce a transmit RF signal by applying a selected pre-distortion setting from the plurality of pre-distortion settings;
receive a representation of the transmit RF signal via a feedback path that differs from the receive path; and
select a differing pre-distortion setting from the plurality of pre-distortion settings based upon the representation of the transmit RF signal and the transmit mode of operation.
18. The wireless device of claim 17 , wherein the plurality of pre-distortion settings comprise a plurality of spectral masks.
19. The wireless device of claim 17 , wherein the transmit mode of operation comprises a number of orthogonal frequency division multiplexing (OFDM) tones of the transmit RF signal.
20. The wireless device of claim 17 , wherein the transmit mode of operation comprises a multiple in multiple out (MIMO) order of the transmit RF signal.