A low noise, high efficiency two stage envelope modulator structure for EDGE polar modulation

This paper presents a transistor level design of a novel envelope modulator structure using a high efficiency voltage doubler followed with a buck DC-DC converter for polar modulation. In order to let the output voltage of the buck converter follows the fast changing EDGE (Enhancement Data-rate for GSM Evolution) reference signal, current mode control and 10 MHz switching frequency are implemented, and ripple cancellation circuits are added in order to further improve the spectral performance. The simulation results show that the output spectrum of the proposed two stage structure complies with the EDGE transmission standard and the spurious noise is greatly reduced by 50 dB compared to 4 switch buck boost converter (4SBBC). This two stage solution also maintains more than 75% average energy efficiency and is a good candidate for EDGE polar modulation.