A 0.5–2 GHz high frequency selectivity RF front-end with series N-path filter

This paper presents a 0.5-2GHz RF front-end with Series N-path Filter. With series 8-path filter applied, an ultimate rejection larger than 46 dB with 30 dB out-of-band rejection at 50 MHz offset is achieved. Dynamic power consumption is saved due to small filter switch size compared with parallel structures. Utilizing a tunable narrow band LNA in front of series N-path filter, 3^rd harmonic rejection exceeding 54 dB with robust to process variation is realized. These techniques improve the front-end´s adjacent and far-end frequency selectivity in RF domain, relaxing mixer´s linearity design pressure. Implemented in 65 nm CMOS process, the frontend achieves a NF of 2.6-5.7 dB and maximum gain of 46-60 dB at 0.5-2 GHz, consuming 18-26 mW from 1.2 V voltage supply and occupies an area of 0.56 mm².