Superconducting, 10 GHz, Two-Bit Digitizer for Radio Astronomy

Hypres proposes to develop an ultra-sensitive 10GS/s Analog to Digital Convertor (ADC) for direct conversion of the SIS (Superconductor-Insulator-Superconductor) mixer output signals to digital data for use in radio astronomy. The observation of broadband emitters, such as cosmic dust clouds and proto-planetary objects, requires a large instantaneous bandwidth for analysis of multiple spectral lines. For these observations a sample rate of 10GS/s is desired. The 10GS/s ADC is constructed from three comparators and digital logic. HYPRES proposes to design, fabricate, and test an innovative comparator design based on Superconducting Quantum Interference Devices (SQUIDs). SQUIDS have demonstrated the energy resolution required for 2K noise thresholds at 5GHz bandwidths. The complete ADC will be fabricated using niobium which operates at 4K, is compact (1mm x 1mm), and low power ( < 1mW) making it suitable for space-based imaging arrays requiring an ADC per pixel. HYPRES has developed superconducting digital logic which can be used to crosscorrelate the ADC data at 10GS/s. The design would the follow the ADC with a 1 to N demultiplexor, this will produce N output ports at l/N of the sample rate, each port is connected to a semiconductor correlator. A second approach would implement a superconducting correlator operating at 10GS/s.