Analysis of spectral spreading in a phase-modulated system for 1.75-GHz GSM RF transmitter design

An efficient and accurate analysis method to calculate the spectral spreading of a phase-modulated signal is presented. It accounts for two major non-idealities in a phase modulated system; (1) the phase error caused by circuit nonlinearity, (2) the additive spreading caused by LO spurious operation. The proposed method requires only a single-tone intermodulation simulation to fully characterize the spectral spreading in a phase-modulated system. Its accuracy is verified by comparing with the measurement results of a 1.75 GHz GSM RF transmitter.