GSM mobile receiver

A baseband receiver arrangement for a GSM phone includes two channels for the in-phase Iin and quadrature Qin components of the receiver signal. Each channel includes a sigma-delta modulator G1,G2 providing a high frequency single bit output data stream. There is a two stage decimation filter with the first stage H1,H2 providing a multi-bit output at a multiple of the symbol rate and the second stage M1,M2 further processing the output of the first stage to provide a multi-bit output at the symbol rate. Between the two filter stages, various other processing, such as digital frequency shifting, may be effected and dc offset correction and gain control may also be carried out on the basis of the output of the first stage filter. The Sigma-delta modulators and the two digital filter sections form a two channel ADC.