Method and apparatus for applying phase shift to digital phase-locked loop circuit to adjust frequency of local oscillator signal used by down-conversion

A wireless communication device comprising:

• a receiver circuit, comprising:
• a down-converter circuit, arranged to apply down-conversion to an input signal according to a local oscillator (LO) signal;
• a phase shift control circuit, arranged to generate a phase shift signal;
• a digital phase-locked loop (DPLL) circuit, arranged to generate the LO signal locked to an initial frequency under a frequency-lock state, wherein in response to the phase shift signal, the DPLL circuit is further arranged to make the LO signal have a different frequency without leaving the frequency-lock state;
• and
• a transmitter circuit;
• wherein the DPLL circuit is a part of the transmitter circuit;
• and the DPLL circuit is used by the transmitter circuit for receiving a phase modulation signal and generating a digitally controlled oscillator (DCO) output that contains phase information when the wireless communication device operates under a transmit (TX) mode, and is re-used by the receiver circuit when the wireless communication device operates under a receive (RX) mode.