Design and Analysis of a W-band 9-Element Imaging Array Receiver Using Spatial-Overlapping Super-Pixels in Silicon

A W-band direct-detection-based receiver array is presented using a new concept of spatial-overlapping super-pixels for millimeter-wave imaging applications in an advanced 0.18 µm BiCMOS process. The use of spatial-overlapping super-pixels results in 1) improved SNR at the pixel level through a reduction of spillover losses, 2) partially correlated adjacent super-pixels, 3) a 2×2 window averaging function in the RF domain, 4) the ability to compensate for the systematic phase delay and amplitude variations due to the off-focal-point effect for antennas away from the focal point, and 5) the ability to compensate for mutual coupling effects among the array elements. The receiver chip achieves a measured peak coherent responsivity of 1,150 MV/W, an incoherent responsivity of 1,000 MV/W, a minimum NEP of 0.28 fW/Hz $^{1/2}$ and a front-end 3-dB bandwidth from 87–108 GHz, while consuming 225 mW per receiver element. The measured NETD of the SiGe receiver chip is 0.45 K with a 20 ms integration time.