Patent ID: 8036611

Claim:
A phase modulator, adaptable for a polar transmitter to generate a phase varying radio frequency (RF) signal based on a phase sample, comprising: a loop control unit, designating a target frequency based on a reference frequency, the phase sample and the RF signal; a logic control unit, generating an oscillator control word based on the target frequency; a digital oscillator, having a capability to modulate from a first phase to a second phase, for synthesizing a preliminary RF signal based on the oscillator control word; wherein the first phase and the second phase are separated by 180 degrees; a phase switch, coupled to the digital oscillator and the logic control unit, selectively shifting the preliminary RF signal by 180 degrees based on a switch signal; wherein, when the target frequency exceeds the modulation capability of the digital oscillator, the logic control unit generates the oscillator control word based on the target frequency minus 180 degrees, and sends a switch signal to direct the phase switch to shift the preliminary RF signal by 180 degrees, such that the RF signal is synthesized to have the target frequency, and when the target frequency does not exceed the modulation capability of the digital oscillator, the logic control unit generates the oscillator control word solely based on the target frequency, and the phase switch directly outputs the preliminary RF signal to be the RF signal having the target frequency.