Standard radio transmitter designs generally include digital processing and waveshaping followed by a multi-bit nyquist rate D/A converter. The output of this converter is then filtered by continuous time low pass filters in the analog domain, removing images of the baseband signal in order to comply with transmit spectral mask requirements. The signal is then mixed to an intermediate frequency for further analog processing. While this technique is widely used, it generally requires complex off chip analog filters following the D/A converter.
In my research I am studying implementation tradoffs in the baseband to IF transmit chain for relatively wideband channels. The digital nature of an oversampled delta-sigma D/A converter allows a great deal of flexibility in choice of converter topology as well as noise transfer function. This flexibility is being used in order to design converters with noise transfer functions suitable for 8-10 bits resolution at signal bandwidths greater than 1MHz.
Center for Integrated Systems, #072
Stanford University
Stanford, CA 94305-4070
(650) 725-4542
Integrated Circuits Lab
Last modified: Mon Nov 1 11:29:36 PDT 1999