Improved Out-of-Band Rejection in Reflection-Mode N-Path Filters Using Tunable Transmission Zeros

Recent topologies for widely tunable and digitally reconfigurable filters, which can replace banks of fixed-frequency filters, have relied on N-path passive mixers. Such circuits are able to provide flexibility in filter center frequency while achieving programmable bandwidths. To address future communication needs, a wideband reflection-mode N-path filter (RMNF) is presented that tunes across 6-31 GHz but operates more optimally across 6-18 GHz. Prior RMNF work suffered from limited out-of-band rejection (OOBR) of unwanted signals. In this work, a technique to improve the OOBR and achieve a tunable out-of-band (OOB) transmission zero is demonstrated. The RMNF is fabricated in the GlobalFoundaries 45-nm RF-SOI process, and across its 6-18-GHz performance range, it achieves 152-220 mW of power consumption, 7.3-12-dB noise figure, and −6.9 to −5.7-dBm input-referred compression point.