Digital Implementation of Bandpass Pulse-Width Modulator

A review of bandpass pulse-width modulation (BP-PWM) is presented. Thereafter, a digital implementation of bandpass pulse-width modulator is discussed using W-CDMA transmitter as an example. It is shown that a BP-PWM transmitter that fulfills W-CDMA adjacent channel leakage ratio (ACLR) requirement in a mobile station can be implemented without using any explicit digital-to-analog converters. A drawback is that very high speed digital logic is required. Moreover, in order to reduce wide bandwidth noise, good filtering after the modulator is required. The implementation of the possible logic circuits is also discussed. The results are verified using reduced speed macro measurements