Tunable N-path RF front-end filter with an adaptive integrated notch for FDD/co-existence

In this paper an RF front-end filter with an adaptive integrated notch is presented. The proposed filter consists of a N-path bandpass filter and a notch filter. The outputs of the bandpass filter and the notch filter are subtracted to create the integrated notch. The third and fifth harmonics are also suppressed due to the subtraction. The filter can handle strong transmitter frequency in the receive band by creating a notch at that particular frequency. The notch frequency can also be adjusted in a certain frequency range and as a result, the proposed filter can block strong out-of-band blockers close to the transmitting frequency. The passband of the filter is tunable from 0.6 GHz to 1.8 GHz. The gain of the filter is 20.3 dB. The NF is 3 dB, which only degrades to 3.68 dB in presence of a 0-dBm blocker at 50 MHz offset. The channel bandwidth is 8.7 MHz and the out-of-band IIP3 (Î"f = 50 MHz) is 18.97 dBm.