Direct Digitization at RF

"Analog components in RF receivers can add noise and distortion, thereby degrading system performance. Mismatching of analog components can contribute to spurious signals in I&Q receivers and beamforming arrays. Elimination of amplifiers and analogdownconversion mixers can be accomplished by moving the analog-to-digital converter (ADC) up to the antenna. In such "digital-RF" systems, sampling is performed at higher rates than the carrier frequency, and downconversion is accomplished with digitalmixers. HYPRES is pursuing digital-RF applications using high-resolution ADCs fabricated with Niobium superconducting chips operating with a conventional semiconductor interface. Our goal is to achieve a wideband digital receiver with a center frequency of~2 GHz for application to commercial communications as well as military multifunction requirements. For Phase I, HYPRES will collaborate with V-Corp to develop a conceptual design for a digital-RF receiver with a 400-MHz input bandwidth. We willinvestigate how HYPRES' strengths in high-oversampling ADCs can be applied to V-Corp's methods of digital signal processing (DSP) to combine the output of multiple ADCs. Our goal in Phase II will be to apply the Phase I design to exceed MDA's 85-dB SFDRand 75-dB SNR specifications. Superconducting technology has already exceeded SFDR levels of -85 dBc at 10-MHz input bandwidth. The inherent linearity of superconducting front ends and the high-speed capa