N-path and pseudo-N-path cells for switched-current signalprocessing

摘要

Novel switched-current N-path and pseudo-N-path cells arenproposed, which allow the transformation of a z-domain low-passnreference filter into a bandpass one. The three types of cells, anforward Euler, backward Euler, and bilinear integrator, perform thenz→-z and z→-zN transformations, which avoidnclock-feedthrough noise in the realized filter passband. Thenpseudo-N-path cells operate on the circulating-delay principle, whichnavoids mirror-frequency noise due to path mismatches and require onlynstandard biphase clocks to operate. The effects of circuit nonidealitiesnare studied and performance comparisons are made with a conventionalnnarrow-band bandpass filter. The robust frequency stabilityncharacteristic makes the cells suitable for narrow-band bandpassnapplications. Results of an HSPICE simulation example is given for ansixth-order pseudo-N-path filter