A THz 31×31 pixel, 100 fps image sensor integrated in a 130 nm CMOS process is presented. Taking advantage of the possibility to modulate the active source that lights the scene, a significant improvement in sensitivity and NEP is achieved by shifting the modulated THz radiation, by means of an antenna/MOSFET, then filtering the signal band using an in-pixel 16-paths passive SC-filter combined with a CT Gm-C filter resulting in a high Q factor of 100. This THz imager features a measured NEP of 533 pW at 270 GHz and 732 pW at 600 GHz respectively, and a sensitive readout chain with an input referred noise of 0.2 μVRMS.