A fully integrated 490-GHz heterodyne imager is reported. The imager adopts a second subharmonic resistive mixer wherein the transmission lines and small capacitors are used to enhance port-to-port isolation and the suppression of undesired local oscillator (LO) leakage and harmonic mixing components. The imager achieves a minimum noise equivalent power of 1.2 pW/Hz(0.5) while dissipating 26 mW from a 1.2-V supply. This work presents the highest frequency implementation among the reported fully integrated heterodyne imagers in silicon technology.