Demodulator alignment method and apparatus

In a receiver, a demodulator alignment circuit comprising:

• a demodulator, having a voltage controlled delay element, said demodulator responsive to a modulated alignment signal for generating an output signal having distortion components;
• a filter, coupled to the demodulator, for filtering the output signal to isolate the distortion components;
• a detector, coupled to the filter, for detecting the isolated distortion components;
• an error amplifier, coupled to the detector, for providing an error signal proportional to the detected distortion components;
• and
• sampling means, coupled to the error amplifier, for sampling the error signal and applying the sampled error signal to the voltage controlled delay element as a correction voltage in order to minimize distortion at the demodulator output.

In an RF receiver, a demodulator alignment circuit comprising:

• a demodulator having a voltage controlled delay element, for demodulating a modulated alignment signal;
• a base band amplifier, coupled to the demodulator, for amplifying the demodulated output signal;
• a detector, AC coupled to the base band amplifier, for detecting amplitude fluctuations in the AC coupled demodulated output signal;
• a differential amplifier, coupled to the detector, for generating a different signal;
• an error amplifier, coupled to the differential amplifier for generating an error signal as a function of the difference signal;
• and
• sampling means, coupled to the the error amplifier, for sampling the error signal and applying the sampled error signal to the voltage controlled delay element as a correction voltage in order to minimize the amplitude fluctuations of the AC coupled demodulated output signal.

In an RF transceiver having transmit and receive modes of operation, a method for aligning a demodulator having a voltage controlled delay element comprising the steps of:

• during the transmit mode;
• generating a modulated alignment signal in response to a modulation reference signal;
• demodulating the modulated alignment signal to produce a demodulated output signal having distortion components;
• generating an error signal proportional to the distortion components of the demodulated output signal;
• sampling the error signal to generate a sampled error signal;
• and during the receive mode:
• disabling generation of the modulated alignment signal;
• and
• applying the sampled error signal to the voltage controlled delay element as a correction voltage in order to minimize the distortion components at the demodulator output.

In an RF transceiver having transmit and receive modes of operation, a method for aligning a demodulator having a voltage controlled delay element comprising the steps of:

• during the transmit mode;
• generating a modulated alignment signal in response to a modulation reference signal;
• demodulating the modulated alignment signal to produce a demodulated output signal having distortion components;
• comparing the demodulated output signal with a delayed version of the modulation reference signal to form an error signal substantially representative of the distortion components;
• sampling the error signal to provide a sampled error signal;
• and
• during the receive mode:
• disabling generation of the modulated alignment signal;
• and
• applying the sampled error signal to the voltage controlled delay element as a correction voltage in order to minimize distortion components at the demodulator output.