Architectural techniques for envelope and phase signal alignment in RF polar transmitters using power amplifier feedback

An RF transmitter, comprising:

• digital processor for producing an outgoing digital IF signal comprising an envelope component and a phase component wherein the envelope component is produced onto an envelope signal path and wherein the phase component is produced on a phase signal path;
• first envelope detector for producing an envelope signal based on the envelope component;
• delay block that delays the envelope signal based on a delay error signal to produce a delayed envelope signal;
• translational loop for up-converting the outgoing digital IF signal to an RF signal;
• wherein the RF transmitter detects a zero crossing of the outgoing digital signal and a zero crossing of a feedback signal and produces the delay error signal based upon a difference between the detected zero crossings;
• translational loop for producing an RF signal based on the outgoing digital signal;
• wherein the RF transmitter substantially aligns the zero crossing of the feedback signal with the zero crossing of the outgoing digital signal to produce the delayed envelope signal that is substantially aligned with the RF signal;
• power amplifier that produces an outgoing modulated RF signal based upon the RF signal and the delayed envelope signal;
• down-converter operably coupled to produce a down-converted feedback signal based on a local oscillation and the outgoing modulated RF signal;
• filtering block to produce a filtered feedback signal based on the down-converted feedback signal;
• analog-to-digital converter (ADC) to convert the filtered feedback signal from an analog domain to a digital domain to produce a digital feedback signal;
• second envelope detector for producing a feedback envelope signal from the digital feedback signal;
• and
• summing node for producing the delay error signal based on the difference between the envelope signal and the feedback envelope signal.

An RF transmitter, comprising:

• digital processor for producing an outgoing digital signal comprising an envelope component and a phase component wherein the envelope component is produced onto an envelope signal path and wherein the phase component is produced on a phase signal path;
• envelope detector for producing an envelope signal based on the envelope component;
• delay block to delay the envelope signal based on a delay signal to produce a delayed envelope signal;
• translational loop for up-converting the outgoing digital signal to an RF signal;
• power amplifier that produces an outgoing modulated RF signal based upon the RF signal and the delayed envelope signal;
• down-converter for producing a feedback signal based on the outgoing modulated RF signal;
• and
• a delay calibrator for producing the delay signal based on an envelope component error signal and a phase component error signal wherein the delay calibrator further includes:
• first and second phase detectors for detecting a zero crossing of the outgoing digital signal and for detecting a zero crossing of the feedback signal, respectively;
• first summing node for producing the phase component error signal based on the difference between a zero crossing of the feedback signal and a zero crossing of the outgoing digital signal;
• phase delay block for delaying the zero crossing of the feedback signal wherein delaying the zero crossing of the feedback signal substantially aligns the zero crossing of the feedback signal with the zero crossing of the outgoing digital signal;
• delay envelope detector for producing a feedback signal based on the delayed feedback signal;
• and
• second summing node for producing the delay signal based on a difference between the delayed signal and the envelope signal.

An RF transmitter, comprising:

• digital processor for producing an outgoing digital IF signal comprising an envelope component and a phase component wherein the envelope component is produced onto an envelope signal path and wherein the phase component is produced on a phase signal path;
• envelope detector for producing an envelope signal based on the envelope component;
• delay block to delay the envelope signal based on a delay signal;
• translational loop for up-converting the outgoing digital IF signal to an RF signal;
• power amplifier that produces an outgoing modulated RF signal based upon the RF signal and the delayed envelope signal;
• at least one down-converter for producing a feedback signal based on the outgoing modulated RF signal, wherein the at least one down-converter produces a baseband signal at a frequency offset substantially equal to a desired adjacent channel;
• filtering block for producing a filtered feedback signal;
• and
• circuitry for producing the delay signal, wherein the circuitry includes:
• first and second phase detectors for detecting a zero crossing of the outgoing digital signal and for detecting a zero crossing of the feedback signal, respectively;
• first summing node for producing the phase component error signal based on the difference between a zero crossing of the feedback signal and a zero crossing of the outgoing digital signal;
• phase delay block for delaying the zero crossing of the feedback signal wherein the zero crossing of the feedback signal substantially aligns the zero crossing of the filtered feedback signal with the zero crossing of the outgoing digital signal;
• delay envelope detector for producing a feedback signal based on the delayed feedback signal;
• and
• second summing node for producing the delay signal based on a difference between the feedback signal and the envelope signal.

A method in a delay calibrator for reducing delay mismatch in a polar transmitter, the method comprising:

• receiving a feedback signal, wherein the feedback signal is a down-converted representation of a polar transmitter output signal;
• receiving a baseband signal having a known power level;
• converting the feedback signal from an analog domain to a digital domain to produce a digital feedback signal;
• adjusting a power level of the feedback signal;
• coupling the digital feedback signal to a first delay block to produce a delayed feedback signal;
• coupling the delayed feedback signal to a first phase detector;
• coupling the baseband signal to a second phase detector;
• comparing an output of the first and second phase detectors to produce a phase error signal;
• adjusting a delay of the first delay block based on the phase error signal;
• coupling the delayed feedback signal to a first envelope detector to produce a first envelope signal;
• comparing the first envelope signal with a second envelope signal to produce an envelope error signal by:
• coupling the delayed feedback signal to the first phase detector to produce a first zero crossing signal;
• coupling the baseband signal to the second phase detector to produce a second zero crossing signal;
• and
• subtracting the first zero crossing signal from the second zero crossing signal to produce the phase error signal;
• and
• adjusting a delay in a second delay block in an envelope signal path based on the envelope error signal to substantially reduce delay mismatch in the polar transmitter.

An RF transmitter, comprising:

• digital processor for producing an outgoing digital signal comprising an envelope component on a first signal path and a phase component on a second signal path;
• envelope detector for producing an envelope signal based on the envelope component;
• delay block for producing a delayed envelope signal based on a delay signal;
• translational loop for producing an RF signal based on the phase component;
• power amplifier that produces an outgoing modulated RF signal based upon the RF signal and the delayed envelope signal;
• feedback path for producing a feedback signal based on the outgoing modulated RF signal;
• first and second phase detectors for detecting a zero crossing of the outgoing digital signal and for detecting a zero crossing of the feedback signal, respectively;
• a phase delay block for delaying the zero crossing of the feedback signal wherein delaying the zero crossing of the feedback signal substantially aligns the zero crossing of the feedback signal with the zero crossing of the outgoing digital signal to generate a delayed feedback signal;
• and
• a summing node for producing the delay signal based on a difference between the delayed feedback signal and the envelope signal;
• and
• wherein the RF transmitter produces the delayed envelope signal substantially aligned with the RF signal based on a difference between the zero crossing of the feedback signal and the zero crossing of the outgoing digital signal.

A method in an RF transmitter, comprising:

• producing an outgoing digital signal comprising an envelope component on a first signal path and a phase component on a second signal path;
• producing an envelope signal based on the envelope component;
• producing a delayed envelope signal based on a delay signal;
• producing an RF signal based on the phase component;
• modulating the RF signal based upon the RF signal and the delayed envelope signal;
• producing a feedback signal based on the outgoing modulated RF signal;
• detecting a zero crossing of the outgoing digital signal and detecting a zero crossing of the feedback signal;
• delaying the zero crossing of the feedback signal to substantially align the zero crossing of the feedback signal with the zero crossing of the outgoing digital signal to generate a delayed feedback signal;
• a summing node for producing the delay signal based on a phase difference between the delayed feedback signal and the envelope signal;
• and
• generating the delay signal based on a difference between the zero crossing of the outgoing digital signal and the zero crossing of the feedback signal wherein the delayed envelope signal is substantially aligned with the RF signal.