Patent ID: 7667551
Filing Date: 2010-02-23
Classification: H04L

Abstract:
1. A frequency shift keying modulator (FSK modulator) having sigma-delta modulated phase rotator, comprising: a phase-locked loop for generating a voltage-controlled signal; a multi-phase generator coupled to the phase-locked loop for receiving the voltage-controlled signal and generating N phase-shift signals having same frequency according to the voltage-controlled signal, the N phase-shift signals having a same phase shift between the phase-shift signals adjacent to each other; a sigma-delta modulator for receiving transmission data and randomly outputting a modulation bit at a modulation clock according to the transmission data; and a phase rotator coupled to the multi-phase generator and the sigma-delta modulator for receiving the N phase-shift signals and selectively outputting one of the N phase-shift signals and a frequency-divided signal according to the modulation bit, wherein the frequency of the frequency-divided signal is  of the frequency of any one of the N phase-shift signals, n is an integer in the range of 1 to (N-1).