We have developed a cost-effective, quad-frequency band THz imager for real-time THz imaging applications operating
at 220GHz, 320GHz, 420GHz, and 520GHz frequency bands. The new sensor is based on antimonide-based
heterostructure backward diodes impedance matched and monolithically integrated with high-gain, narrowband planar
antennas. The antennas are dual-linearly polarized to allow direct measurement of beam polarization. This paper details
the fabricated THz detector array and the high-speed, low-noise readout electronic chain. Experimental results on the
performance of the readout chain and simulations of the expected THz detector performance are presented.