A Multilevel N-Path Filter Topology for Low-Power Sinusoidal Clocking with Non-Overlapping Phases

This paper presents a multilevel passive mixer topology that allows N-path filters to operate at millimeter-wave frequencies from sinusoidal clocks without suffering from on-time overlapping between the adjacent phases. For differential N-phase passive mixing, the topology consists of N/2+1 series-connected out-of-phase switch pairs that operate from N/2 evenly-phase-shifted 50%-duty clock waveforms. Through the proposed topology, tunable differential LO buffers with LC loads can be used to resonate the gate capacitance of the filter switches and hence lower the mixer dominant gate-drive power loss without degrading the filter noise figure, linearity, or stopband attenuation. Simulation results using 0.18μ m CMOS demonstrate that the proposed multilevel topology provides 7 dB, 9 dB, and 2.4 dB improvements in the achievable selectivity, in-band IIP
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, and noise figure, respectively, over conventional 4-path architectures at high frequencies.