Analysis of discrete-time charge-domain complex bandpass filter with accurately tunable center frequency

This paper proposes a new discrete-time complex bandpass (DT CBP) filter topology in charge domain, only using switches, capacitors, input transconductors and non-overlapping 2-phase clock scheme. The proposed DT filter features better power-efficiency, reduced complexity and easier process-scaling compared to the conventional topologies. It has an inherent anti-aliasing sinc characteristic due to the windowed integration of input voltage to current/charge during each phase. The center frequency is only determined by the capacitors ratio and sampling frequency, insensitive to PVT variations. The practical non-idealities, such as finite output impedance of input gm-stage, output impedance of source follower, non-zero switch resistance, etc. are mainly analyzed in this paper and compared with the simulated results. Simulations demonstrate that the proposed DT topology is quite robust to those non-idealities.