The port-to-port isolation of the micromixer is studied using three different p-type downconversion micromixers in 0.35-μm CMOS technology. Both the body effect and the well isolation influence the port-to-port isolation significantly. The body effect degrades the LO-to-IF isolation and also deteriorates the LO-to-RF isolation. Without the well isolation, the LO-to-RF isolation drops. However, the RF-to-IF isolation is independent of the body effect and well isolation. The p-type micromixer with a separate N-well and without body effect has the best port-to-port isolation properties; its LO-to-IF, LO-to-RF. and RF-to-IF isolations are -59 dB. -58 dB, and -30 dB, respectively.