N-Path Phase Shifter and Its Applications

This paper presents an original design for RF phase shifting based on N-path filtering. This approach enables to address various functionalities as I/Q generator, phase shifters for antenna array or baluns that are frequency selective, frequency tunable, and achieve positive voltage gain. As a demonstration, an N-path balun is implemented in the GF 45RFSOI technology node and measured. The circuit operates from 250 MHz to 1.25 GHz, showing a maximum measured gain of 6.9 dB and a minimum noise figure of 2.5 dB at 250 MHz for 1.2 mW power consumption. The maximum amplitude and phase imbalances are 0.4 dB and 0.5°, respectively.