Research Projects

The trend in wireless receiver architectures is to move the analog-to-digital converter(ADC) towards the antenna, thus relaxing the requirements placed on analog circuits atthe expense of a more complex digital circuitry. This also allows more digital integration ofanalog functions on a single chip resulting in a cheaper system. In these architectures,currently, surface acoustic wave (SAW)-less receiver schemes are preferred due to theircompatibility with multiple standards and programmability. However, these architecturesare prone to performance degradation caused by interference signals like out of bandblockers. Indeed, to suppress those interference signals, conventional solutions use abulky, off-chip, high Q, SAW filter which increases system cost, area and complexity. Stateof the art SAW-less receiver architectures mitigate the interference problems in the RFfront-end like Low Noise Amplifier and Mixers. However in presence strong interferencesreceiver system requires additional stringent filter before ADC. Interferences can also berejected in baseband using built-in low-pass filter for a base band receiver architecture.However zero-IF architecture suffers from DC offset and 1/f noise. These issues canmitigates by using low-IF architectures, which requires band-pass Sigma DeltaModulators to digitize the signal at IF. Sigma delta converters have many advantages thatmake it the best candidate for receiver applications. They give rise to high performancewithout requiring to use precision components; moreover, since the processing isdominated by the digital part, the entire architecture consumes relatively lower power.Sigma-Delta modulator achieves better performance due to noise shaping andoversampling. Significant efforts were made in the last few years to obtain low power,higher bandwidth ADC. The architecture requires an additional band-pass filter to removeinterference and digital conversion can be implemented by band-pass modulators.However interference is a concern in the state of art modulators, hence embedded filterbased modulator is need of the time. The Proposed topology in this project eliminatesneed of the stringent Filter, which can embedded into the band-pass Sigma DeltaModulator with negligible additional power dissipation and improved performance.