NbN circuits and packaging for 10 Kelvin IR focal plane array sensor signal processing

Infrared (IR) focal plane array (FPA) imaging signal processing circuits, built in NbN and operating at 10 Kelvin, are presented. An ADC chip and digital signal processing chip are mounted on a 1.25 inch multi-chip module (MCM) with high bandwidth, low impedance interconnect. The populated MCM is designed to be installed into a module housing for operation with the cryogenic IR FPA. The 12-bit NbN SFQ counting ADC, previously used in a single chip version of the IR focal plane array sensor test system, is now implemented in an improved NbN process which includes a ground plane. Considerable attention has been focused on reducing parasitic inductance to compensate for the high characteristic inductance of the NbN films. These design improvements increase operating margins and circuit yield and make the ADC more robust in the presence of external system noise. Data from a bit-serial subtraction circuit to be used for pixel-by-pixel background subtraction is also presented. Finally, the design and electrical qualification of the physical package is described.