Mobile wireless communications device with separate in-phase (I) and quadrature (Q) phase power amplification and power amplifier pre-distortion and IQ balance compensation
View Patent ↗A communications device, in one aspect as a portable wireless communications device, includes an in-phase modulator and power amplifier that receives a baseband I signal and modulates and amplifies the I signal. A quadrature modulator and power amplifier receives a baseband Q signal and modulates and amplifies the Q signal. A power combiner sums and outputs the I and Q signals. An I demodulator circuit receives a signal fed back from the I power amplifier and demodulates the fed back signal to produce demodulated I signals. A Q demodulator circuit receives a signal fed back from the Q power amplifier and demodulates the fed back signal to produce demodulated Q signals. A processor compares the digital, baseband I and Q signals with a demodulated I and Q signals to compensate for amplitude, frequency and phase modulation errors.
1. A communications device comprising:
an In-phase (I) circuit comprising an I power amplifier circuit and said I circuit configured to modulate and amplify a digital, baseband I signal;
a Quadrature (Q) circuit comprising a Q power amplifier circuit and said Q circuit configured to modulate and amplify a digital, baseband Q signal;
a power combiner configured to receive the separately modulated and amplified I and Q signals and output a combined I and Q signal;
an I demodulator circuit that directly receives a feedback signal from the I power amplifier circuit and configured to demodulate the feedback signal from the I power amplifier circuit and produce a demodulated I signal;
a Q demodulator circuit that receives a feedback signal from the Q power amplifier circuit and configured to demodulate the feedback signal from the Q power amplifier circuit and produce a demodulated Q signal; and
a processor configured to compare the digital, baseband I and Q signals with the demodulated I and Q signals to compensate for at least one of an amplitude error, a frequency error, and a phase modulation error.
2. The communications device according to claim 1 , wherein the processor is configured to predistort the digital baseband I and Q signals fed to the I and Q circuits.
3. The communications device according to claim 1 , wherein the I circuit comprises an I modulator and mixer circuit and an I power amplifier circuit coupled thereto; and wherein the Q circuit comprises a Q modulator and mixer circuit and a Q power amplifier circuit coupled thereto.
4. The communications device according to claim 3 , wherein the I modulator and mixer circuit receives I_I and I_Q input signals to produce an I signal to the I power amplifier; and wherein the Q modulator and mixer circuit receives Q_I and Q_Q input signals to produce a Q signal to the Q power amplifier.
5. The communications device according to claim 4 , wherein the I modulator and mixer circuit comprises an I_I mixer and I_Q mixer configured to receive respective I_I and I_Q signals and a frequency divider circuit associated therewith configured to impart a ninety degree phase shift, and an I summer configured to receive signals from the mixers and produce an I signal.
6. The communications device according to claim 4 , wherein the Q modulator and mixer circuit comprises a Q_I mixer and Q_Q mixer configured to receive respective Q_I and Q_Q signals and a frequency divider circuit associated therewith configured to impart a ninety degree phase shift, and a Q summer configured to receive signals from the mixers and produce a Q signal.
7. The communications device according to claim 3 , wherein the processor is configured to output control signals for controlling each of the power amplifier circuits, and control respective biasing in each power amplifier circuit.
8. The communications device according to claim 3 , wherein each of the I and Q demodulator circuits comprise mixers and a frequency divider associated therewith configured to impart a ninety degree phase shift.
9. The communications device according to claim 1 , further comprising an I/Q demodulator circuit connected to the processor and configured to receive a signal from the output of the power combiner.
10. The communications device according to claim 1 , further comprising a power detector connected to the processor and configured to receive a signal from the output of the power combiner and output a signal that is compared with an original power.
11. The communications device according to claim 1 , wherein the power combiner comprises about a 3 dB power combiner.
12. The communications device according to claim 1 , wherein the power combiner comprises a quadrature hybrid power combiner.
13. A mobile wireless communications device comprising:
a housing;
an antenna carried by the housing;
at least one circuit board carried by the housing and including radio frequency (RF) circuitry carried by the at least one circuit board and comprising
an In-phase (I) circuit comprising an I power amplifier circuit and said I circuit configured to modulate and amplify a digital, baseband I signal,
a Quadrature (Q) circuit comprising a Q power amplifier circuit and said Q circuit configured to modulate and amplify a digital, baseband Q signal,
a power combiner configured to receive the separately modulated and amplified I and Q signals and output a combined I and Q signal,
an I demodulator circuit that directly receives a feedback signal from the I power amplifier circuit and configured to demodulate the feedback signal from the I power amplifier circuit and produce a demodulated I signal,
a Q demodulator circuit that receives a feedback signal from the Q power amplifier circuit and configured to demodulate the feedback signal from the Q power amplifier circuit and produce a demodulated Q signal, and
a processor configured to compare the digital, baseband I and Q signals with the demodulated I and Q signals to compensate for at least one of an amplitude error, a frequency error, and a phase modulation error.
14. The mobile wireless communications device according to claim 13 , wherein the processor predistorts the digital baseband I and Q signals fed to the I and Q circuits.
15. The mobile wireless communications device according to claim 13 , wherein the I circuit comprises an I modulator and mixer circuit and an I power amplifier circuit coupled thereto; and wherein the Q circuit comprises a Q modulator and mixer circuit and a Q power amplifier circuit coupled thereto.
16. The mobile wireless communications device according to claim 15 , wherein the I modulator and mixer circuit is configured to receive I_I and I_Q input signals to produce an I signal to the I power amplifier; and wherein the Q modulator and mixer circuit is configured to receive Q_I and Q_Q input signals to produce a Q signal to the Q power amplifier.
17. The mobile wireless communications device according to claim 16 , wherein the I modulator and mixer circuit comprises an I_I mixer and I_Q mixer configured to receive respective I_I and I_Q signals and a frequency divider circuit associated therewith configured to impart a ninety degree phase shift, and an I summer configured to receive signals from the mixers and produce an I signal.
18. The mobile wireless communications device according to claim 16 , wherein the Q modulator and mixer circuit comprises a Q_I mixer and Q_Q mixer configured to receive respective Q_I and Q_Q signals and a frequency divider circuit associated therewith configured to impart a ninety degree phase shift, and a Q summer configured to receive signals from the mixers and producing a Q signal.
19. The mobile wireless communications device according to claim 15 , wherein the processor is configured to output control signals for controlling each of the power amplifier circuits, and control respective biasing in each power amplifier circuit.
20. The mobile wireless communications device according to claim 15 , wherein each of the I and Q demodulator circuits comprise mixers and a frequency divider associated therewith configured to impart a ninety degree phase shift.
21. The mobile wireless communications device according to claim 13 , further comprising an I/Q demodulator circuit connected to the processor and configured to receive a signal from the output of the power combiner.
22. The mobile wireless communications device according to claim 13 , further comprising a power detector connected to the processor and configured to receive a signal from the output of the power combiner and output a signal that is compared with an original power.
23. The mobile wireless communications device according to claim 13 , wherein the power combiner comprises about a 3 dB power combiner.
24. The mobile wireless communications device according to claim 13 , wherein the power combiner comprises a quadrature hybrid power combiner.
25. The mobile wireless communications device according to claim 13 , wherein the RF circuitry is configured to generate Global Systems for Mobile (GSM) packet bursts.
26. A method of operating a communications device comprising:
modulating and amplifying within an I power amplifier circuit a digital, baseband In-phase (I) signal using an I circuit;
modulating and amplifying with a Q power amplifier circuit a digital, baseband Quadrature (Q) signal using a Q circuit
outputting a combined I and Q signal using a power combiner receiving the separately modulated and amplified I and Q signals;
receiving a feedback signal directly from the I power amplifier circuit and demodulating the feedback signal from the I circuit using an I demodulator to produce a demodulated I signal;
receiving a feedback signal from the Q power amplifier circuit and demodulating the feedback signal from the Q circuit using a Q demodulator to produce a demodulated Q signal; and
comparing the digital, baseband I and Q signals with the demodulated I and Q signals using a processor to compensate for at least one of an amplitude error, a frequency error, and a phase modulation error.
27. The method according to claim 26 , further comprising using the processor to predistort the digital baseband I and Q signals fed to the I and Q circuits.