Signal Folding Improvement in N-Path Filters by Programmable Switched-LC Band-Stop Pre-Filtering

In this paper, a method for signal folding improvement in N-path filters is presented. By applying a new technique based on pre-filtering to a former structure, the difference in gain between the desired signal and folded harmonics increases. The proposed N-path filter also performs single-ended to differential conversion to reject harmonic selectivity around even harmonics. The new structure, which is simulated using 90nm technology, has a frequency tuning range of 800MHz that varies from 1.3GHz to 2.1GHz. The input impedance matching and NF are, respectively, less than −10dB and 4.6dB in the entire frequency range. The in-band IIP3 is better than 5dBm, and the power consumption of the non-ideal clock generator varies from 2.9mW to 4.8mW depending on the filter center frequency.