Morten Damgaard

A triple-band 900/1800/1900 MHz low-power image-reject front-end for GSM

Conventional cellular handset receiver designs place receive-band filters, usually surface acoustic wave (SAW) filters, prior to and after the low-noise amplifier (LNA). In a triple-band receiver, this amounts to six SAW filters. The device presented here also eliminates the post-LNA SAW filters, but without the excess current required by image-reject mixers. It does so through the use of passive on-chip LC image filters. This makes possible higher dynamic range with low supply current, and low noise figure while providing a greater amount of image-rejection in comparison with image-reject mixer-based solutions.

Polar loop transmitter for GSM/GPRS/EDGE

An EDGE transmitter using a nonlinear GSM type PA is presented. It is based on a polar loop architecture that employs separate feedback control of the amplitude and the phase of the output signal. With this approach, the problems with AM-to-PM as well as AM-to-AM of the nonlinear PA are essentially eliminated. There is no mode change between GMSK and EDGE, and the transmitter operates seamlessly in multi-slot EGPRS. The polar modulation transmitter meets all the GSM type approval requirements for both EDGE and GMSK in the quad band (850/900/1800/1900 MHz). It is part of an RF subsystem which is in production.