Analysis and design of a notch filter for the rejection of interference in UWB systems and its application to a 0.13-um CMOS receiver front-end.

This work reports the analysis and the design of a 0.13-um CMOS fourth-order notch filter for the rejection of the 5-6 GHz interference in UWB front-ends. The filter is integrated into an analog front-end for Mode #1 UWB systems, i.e. operating in the 3.1-4.8 GHz frequency range. A thorough analysis based on a simplified model of the filter is carried out. An algorithm for the automatic tuning and calibration of the filter is also discussed and demonstrated. Two versions of the circuit are designed and fabricated: the first comprises a low-noise amplifier (LNA) and the filter, the second expands it to a complete front-end. In the latter version the filter was also redesigned. The filter provides more than 35 dB of attenuation and has a tuning range of 900 MHz, adding less than 30% power consumption to the LNA. The out-of-band IIP3 takes a 9-dB advantage from the filter and the compression of the gain due to the out-of-band blocker is reduced by at least 6 dB in the complete front-end.