Patent ID: 7227910

Claim:
A communication device with a circuit arrangement for generating an analogue signal from a digital input signal in form of a complex baseband signal, represented by samples of an in-phase and a quadrature-phase component (I′, Q′) comprising a first interpolation filter ( 16 ) for generating up-sampled in-phase samples from said in-phase input samples, each sample having a first bit width (m); a first sigma-delta modulator ( 8 ) to which the up-sampled in-phase samples are input to, generating sigma-delta modulated in-phase output samples of a second bit width (n), whereby the bit width of the sigma-delta modulated samples is lower than the bit width of the up-sampled in-phase samples; a second interpolation filter ( 17 ) for generating up-sampled quadrature-phase samples from the said in-phase input samples, each sample having said first bit width (m); a second sigma-delta modulator ( 8 ) to which the up-sampled quadrature-phase samples are input to, generating sigma-delta modulated quadrature-phase output samples of a second bit width (n), whereby the bit width of the sigma-delta modulated quadrature-phase output samples is lower than the bit width of the up-sampled quadrature-phase samples; an IQ-modulator for generating from said sigma-delta modulated in-phase and quadrature-phase samples a stream of IQ-modulated samples; a digital-to-analogue converter ( 10 ) for generating said analogue signal from that stream of IQ-modulated samples; and, wherein said first and second sigma-delta modulators each include a control circuit arrangement ( 82 , 84 ) for controlling the bit width (n) of the output samples of said sigma-delta modulator ( 8 ).