Improved Bandpass ADC Technology for Satellite Communication

HYPRES has been developing a family of ultrafast bandpass analog-to-digital converters (ADCs) based on rapid-single-flux-quantum (RSFQ) superconducting technology, for direct digitization of radio-frequency (RF) communication signals. These have important applications to sensitive and flexible satellite communication (SATCOM) systems, and prototype SATCOM receivers directly digitizing RF signals above 20 GHz with impressive performance have recently been demonstrated. Several paths to further performance improvement have already been identified, including fabrication of smaller Josephson junctions and higher-order modulator designs. In the present Phase II project, a novel approach will be investigated that incorporates a multi-threshold quantizer. This is an independent and complementary direction for further enhancement of the ADC dynamic range. Preliminary simulations for a seven-threshold quantizer indicate an increase of 17 dB (almost 3 bits) of dynamic range while maintaining superior device linearity. This multi-bit ADC will require a corresponding multi-bit digital downconverter (DDC) and digital channelizer. The present project will design, fabricate, and test a multi-bit quantizer, with on-chip integration with DDC and channelizer included as Phase II Options. This will result in record-breaking ADC performance that has not been achieved in any device technology.