10 K NbN DSP module for IR sensor applications

The authors report significant progress on infrared (IR) focal plane array (FPA) imaging signal processing circuits, built in NbN and operating at 10 K. The improvements to our NbN process are highlighted by the introduction of directly grounded junctions (DGJ). These DGJs substantially reduce parasitic inductance thereby compensating for the high sheet inductance of NbN films. The circuits being developed include a 16-bit SFQ counting ADC and several digital signal processing (DSP) units. We report test results of greatly improved ADC performance, which is the result of both improved designs and fabrication techniques. Signal processing units on individual chips have been designed, fabricated, and tested. They perform functions such as background subtraction, gain and responsivity correction, and data reduction. We report test results of the DSP chips performing these functions. Ultimately, these chips will be integrated on a multi-chip-module (MCM) with high bandwidth, low impedance interconnects and integrated with an IR focal plane array sensor.