This paper presents a wideband THz sideband separation receiver (SSR) in 0.13 µm BiCMOS technology. The receiver employs a modified Weaver architecture with a subharmonic first stage mixer for downconversion. The second stage mixer is fed with quadrature signals to separate the up sideband (USB) and low sideband (LSB) in two differential channels. The second stage mixer employs a r/c polyphase filter design to generate the required quadrature signals in its LO. The design presented achieves an image rejection ratio (IRR) that exceeds 20 dB in the H band from 220-320 GHz with no calibration required. The receiver, measuring 1.2 mm2 and consuming only 19 mW plus the power for the local oscillators, is ideal for application in focal plane array (FPA), multiple-pixels, for space-borne observation.