A Blocker Tolerant N-path Filter with Tunable Notches for Software-Defined Radio Applications

Abstract

In this paper, a blocker-tolerant N-path filter (BTNPF) with tunable notches is proposed for software-defined radio utilization. Two notches are created by the cancellation of the transmitted signals from two parallel paths. The notch frequency and attenuation can be adjusted by tuning the gain and bandwidth of the two paths. The tunable notch provides a good tolerance to close-in blockers. The proposed BT-NPF can achieve an 18. 5~26.6dB gain with a bandwidth of 8. 4~14.8MHz, a frequency tuning range of 0. 1~1.5GHz, and a noise Figure of 4. 4~5.9dB. The out-of-band IIP3 is 20. 5dBm and blocker P1dB is 0dBm. The noise Figure degrades only 0. 8dB in the presence of a 0dBm blocker with an offset frequency of 80MHz.