A wide-band linear amplitude modulator for polar transmitters based on the concept of interleaving delta modulation

Polar transmission techniques offer the capability of multimode wireless transmission and the potential for significant efficiency gains over solutions based on I/Q. However, polar transmitters are difficult to implement because of the wide bandwidths associated with the phase and envelope signals. Moreover, accurate synchronization between envelope and phase components is essential in minimizing distortion. A concept named Interleaving Delta Modulation (iDM) is proposed to overcome some of the issues associated with polar transmission. IDM minimizes distortion and improves efficiency by replacing a stream of fast drive pulses to the amplitude modulator with a parallel stream of slower pulses. Circuitry to implement iDM has been designed, fabricated, and measured in 0.35-μm CMOS technology.