Switch-R-C passive N-path mixers and ﬁlters enable interference-robust radio receivers with a ﬂexibly pro-grammable center frequency deﬁned by a digital multi-phase clock. The radio frequency (RF) range of these circuits is limited by parasitic shunt capacitances, which introduce signal loss and degrade noise ﬁgure. Moreover, the linear periodically time varying (LPTV) nature of switch-R-C circuits results in unwanted signal folding which needs to be suppressed by linear time- invariant (LTI) pre-ﬁltering by passive LC ﬁlters. This paper analyzes the interaction between capacitive or inductive LTI pre-ﬁltering and an N-path mixer or ﬁlter, leveraging an analysis technique based on the impulse response of the adjoint network. Previously reported results for an inductive source impedance are derived in a simpler fashion, while providing circuit intuition. Moreover, new results for N-path receivers with a shunt capacitor, and a combination of a series inductor and shunt capacitor are derived, as well as design criteria to minimize loss and frequency shifting in the peak response of these circuits.
|Number of pages||12|
|Journal||IEEE transactions on circuits and systems I: regular papers|
|Publication status||Published - 1 May 2018|