Analysis of imperfections in N-phase high-Q band-pass filters

The effect of clock skew and duty-cycle on the performance of high-Q N-phase band-pass filters (BPFs) have been examined in this paper. Following a mathematical approach and using the analytical derivations carried out, the effects of such non-idealities as clock skew and duty-cycle error are determined in an N-path filter. It is analytically proved that image signals from all integer multiples of the clock signal, rather than just those at (1 ± kN) multiples of the clock signal, land atop the wanted RF spectrum. In a real world clock generator, with non-idealities in effect, filtering property and proper behavior of the filter is adversely affected. Finally, system level simulation along with circuit simulation using TSMC 0.18μm process have been performed which corroborate the proposed analytical derivations.