A Baseband Analog Spectrum Sensing Unit Employing Super Source Follower-Based Channel Selection Filters

The down-converted RF spectrum band is passed on to two chains of five cascaded real low-pass filters and five cascaded complex low-pass filters in parallel to simultaneously scan upper sideband and lower sideband around the local oscillator. In order to detect an energy of multiple narrowband portions simultaneously within the overall wideband detection bandwidth, the cutoff frequencies of five cascaded low-pass filters in each chain are reduced in steps of resolution bandwidth. This greatly reduces the spectrum sensing time owing to the parallel signal processing. In this work, five cascaded super source follower-based real low-pass filters are designed as a part of low power baseband analog spectrum sensing unit with fast spectrum sensing time. In the simulation results using a 65-nm RF mixed-mode CMOS technology, the cutoff frequencies of five cascaded real low-pass filters decreases from 10 MHz to 2 MHz in steps of 2 MHz to detect an energy over 2 MHz resolution bandwidth. The worst noise figure (NF) of the filter chain is about 30.3 dB at the final output, and the total power consumption is 4.4 mW from a 1.2 V supply voltage.