A V-Band 8-Element Phased Array Radiometer Front-End for Passive Millimeter Wave Imaging

An eight-channel phased array (PA) radiometer front-end is developed to serve video-rate passive millimeter wave (PMMW) imaging at V-band. The front-end is implemented by multichip module (MCM), in which all active microwave functions are realized with GaAs monolithic microwave integrated circuits (MMICs) while passive devices and connection lines are designed on printed circuit board (PCB). All receiver channels are linearly arranged and equipped with waveguide-fed dielectric rod antennas (DRAs). By introducing a surface metallized bent structure into the DRA, the phase center of element antenna can be changed, which provides an effective approach to suppress grating lobes without a significant increase in structural complexity of the sparse array. Moreover, chip assembly details are presented together with the methods taken to mitigate the mismatch caused by wire-bond interconnections and MMICs. Single-channel (SC) and overall-module measurements are applied to the front-end, and the results reveal that the front-end achieves 50-dB gain, 5-dB noise figure (NF), ±24° field of view (FoV) and -10-dB side/grating lobes within the frequency band of 52-56 GHz. Finally, a passive imaging system is established using the proposed front-end and the primary imaging results verify the front-end design in system level.