Design of Signal Modulator for RF Polar Transmitter

This paper presents new approach to signal modulation for high efficiency polar transmitter. The new modulator is derived by analyzing complex to polar transforming equations. Once spectral behavior of an envelope and phase signals are known, new architecture offering lower complexity in an analog domain and more flexibility for reconfiguration than a conventional modulator is derived. Concept of the modulator is verified in the course of step-by step simulations with a 5MHz BW input signal at a carrier frequency fC = 2.14GHz. Also, a drain efficiency of a Class E PA driven by the modulator is discussed, and optimal solution for sampling rate is proposed. Figure 1. (A) Class S power amplifier (B) Digitized polar power amplifier