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We present a tunable LNA for software defined radio based on a compact, tunable transmission line (CTTL) element. The CTTL acts as a passive, widely tunable LC resonance in a cascoded, common source LNA to implement an instantaneously narrowband, multi-octave tunable LNA. The resulting circuit, fabricated in 65nm CMOS, is tunable from 3.5-20GHz, and consumes 12 mW with gain >12dB, ≥ -9.6dBV in-band OP1dB, and OOB B1dB up to 31dB higher than the in-band B1dB due to the CTTL-tuned LC filtering. The CTTL-tuned LNA represents a more blocker-tolerant approach to achieving high frequency, software-defined LNAs without significant compromises in other LNA performance metrics.more » « less
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Cognitive radio aims at identifying unused radio-frequency (RF) bands with the goal of re-using them opportunistically for other services. While compressive sensing (CS) has been used to identify strong signals (or interferers) in the RF spectrum from sub-Nyquist measurements, identifying unused frequencies from CS measurements appears to be uncharted territory. In this paper, we propose a novel method for identifying unused RF bands using an algorithm we call least matching pursuit (LMP). We present a sufficient condition for which LMP is guaranteed to identify unused frequency bands and develop an improved algorithm that is inspired by our theoretical result. We perform simulations for a CS-based RF whitespace detection task in order to demonstrate that LMP is able to outperform black-box approaches that build on deep neural networks.more » « less
