High Performance, All Digital RF Receiver Tested at 7.5 GigaHertz

Wireless applications would be less expensive, more flexible, and more robust if they had more digital and less analog circuitry. The problem is implementing digital signal processing at radio frequencies. Conventional data converters (ADCs and DACs) and digital circuits are simply not fast enough, especially at SATCOM frequencies. However, superconductors can provide ultra fast mixed signal and digital circuits with the linearity and dynamic range required for true direct, digital-RF processing. These superconducting circuits are digital ICs based on Josephson junctions and "rapid-single-flux-quantum" logic (RSFQ), where simple circuit switching speeds up to 750 GHz have been demonstrated. This permits direct conversion between analog RF and digital baseband signals, replacing frequency and protocol-specific analog hardware with flexible digital processors. HYPRES recently developed and delivered an X-band All Digital RF Receiver (XADR) prototype system for the US Army CERDEC and PM DCATS. The concept of this ADR is to replace the entire analog RF receive chain between the antenna and the baseband demodulator with a high performance digital RF equivalent. The first XADR prototype system has been successfully demonstrated at the Joint SATCOM engineering Center (JSEC). End to end link testing, over the satellite has been successfully completed using an existing AN/GSC-39 X-band earth terminal, an XTAR satellite, the X-band ADR and a SATCOM modem.