Reconfigurable N-path RF front-end filter with improved blocker rejection

In this paper an RF channel select filter with improved blocker rejection is presented. The proposed filter consists of three parallel resonant tanks and two series resonant tanks all implemented with N-path switched-cap filters. Due to the inclusion of notch filters between the bandpass filters, the rejection of the filter in the vicinity of the passband is higher compared with any existing filters. Out-of-band blockers are suppressed due to high filter rejection. The filter is tunable from 0.2 GHz to 1.8 GHz. The proposed tunable filter has 48.3 dB rejection at 20 MHz offset and has 58.8 dB rejection at 45 MHz offset from the center frequency. The high stop-band rejection of 71.2 dB has been achieved by creating notches outside the bandwidth of the filter.