Exploiting the high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO), we have extended chirp-transform processing to instantaneously analyze the spectrum of an incoming signal over greater bandwidth than any competing technology. A compact receiver has been developed that can analyze a 3 GHz bandwidth in 120 ns with 110 MHz resolution. The cryogenic YBCO chirp filter and ambient-temperature semiconductor electronics have been space qualified for flight on the US Navy's High-Temperature Superconductivity Space Experiment, a package to be launched on the US Air Force ARGOS scientific satellite.>
Exploiting the high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO), we have extended chirp-transform processing to instantaneously analyze the spectrum of an incoming signal over greater bandwidth than any competing technology. A compact receiver has been developed that can analyze a 3 GHz bandwidth in 120 ns with 110 MHz resolution. The cryogenic YBCO chirp filter and ambient-temperature semiconductor electronics have been space qualified for flight on the US Navy's High-Temperature Superconductivity Space Experiment, a package to be launched on the US Air Force ARGOS scientific satellite.>
We have constructed a five-bit high temperature superconductive digital instantaneous frequency measurement (DIFM) subsystem capable of determining the frequency of unknown signals over a 500-MHz bandwidth, centered on 4 GHz, with a resolution of 17.8 MHz. The system consists of three parts: a limiting amplifier and filter, a comparator and data processing unit operating at room temperature, and a cryogenic subsystem containing five discriminator modules based on superconductive delay lines, GaAs mixers and power dividers. With a single-tone CW input between -40 dBm and +10 dBm, the frequency quantization boundaries of the subsystem are, on average, 3.1 MHz from their design values. This system was built for the High-Temperature Superconductor Space Experiment, Phase II (HTSSE II). It has passed all required qualification tests for vibration, shock and thermal cycling. The system is currently scheduled for satellite launch in fall 1996. Compared to a conventional system, the superconductive version of the DIFM is considerably smaller and provides enhanced resolution. In addition, the technology employed can be readily extended to a system with additional bits and wider instantaneous bandwidth. The system built demonstrates the potential for system-level applications of high-temperature superconductive electronics in instrumentation, communications, radar, and electronic warfare.
Digital superconductor electronics has been experiencing rapid maturation with the emergence of smaller-scale, lower-cost communications applications which became the major technology drivers. These applications are primarily in the area of wireless communications, radar, and surveillance as well as in imaging and sensor systems. In these areas, the fundamental advantages of superconductivity translate into system benefits through novel Digital-RF architectures with direct digitization of wide band, high frequency radio frequency (RF) signals. At the same time the availability of relatively small 4K cryocoolers has lowered the foremost market barrier for cryogenically-cooled digital electronic systems. Recently, we have achieved a major breakthrough in the development, demonstration, and successful delivery of the cryocooled superconductor digital-RF receivers directly digitizing signals in a broad range from kilohertz to gigahertz. These essentially hybrid-technology systems combine a variety of superconductor and semiconductor technologies packaged with two-stage commercial cryocoolers: cryogenic Nb mixed-signal and digital circuits based on Rapid Single Flux Quantum (RSFQ) technology, room-temperature amplifiers, FPGA processing and control circuitry. The demonstrated cryocooled digital-RF systems are the world's first and fastest directly digitizing receivers operating with live satellite signals in X-band and performing signal acquisition in HF to L-band at ∼30GHz clock frequencies.
A YBa/sub 2/Cu/sub 3/O/sub 7- delta / (YBCO) step-edge microbridge JJ (Josephson junction), two 12-GHz YBCO microstrip bandpass filters, a 1-GHz YBCO filter, and current bias and voltage monitor circuits were successfully combined on a 20-mm*20-mm MgO substrate and integrated into a frequency downconverter for receiving DBS (direct broadcast satellite) signals. The YBCO downconverter and the GaAs low-noise IF (intermediate frequency) amplifier were combined in a microwave cryostat. The dependence of mixing signals on temperature and LO (local oscillator) input power was measured. The conversion gain and the noise figure corresponding to the YBCO downconverter package were -14.5 dB and 12.2 dB, respectively, at 15 K and low LO power (-25 dBm). The first demonstration of the HTS (high-temperature superconductive) subsystem, i.e. the monolithic YBCO downconverter, shows potential for applications in mobile radio communications and satellite broadcasting.>
A wide variety of applications, ranging from radio-frequency (RF) receivers for broadband communications and signal detection, on earth and in space, would benefit from high-performance superconductor analog-to-digital converters (ADCs), based on magnetic flux quantization and fast switching Josephson junctions. Superconductor ADCs are capable of very high sample rates (100 GHz or more), very high linearity, and high sensitivity. Nyquist-rate ADCs use the high sample rate to digitize a wide instantaneous bandwidth (tens of GHz) and are useful for wideband spectrum monitoring as well as high-end scientific instrumentation. Delta and delta-sigma oversampling ADCs use the high linearity to achieve programmable trade-off between dynamic range and instantaneous bandwidth. These lowpass and bandpass ADCs have been used for direct digitization of narrower (tens to hundreds of MHz) RF bands in the 1-20 GHz range for a variety of communications, intelligence, electronic warfare, and radar applications. Another application area of these cryogenic ADCs is for outputs of cryogenic sensor arrays and terahertz mixers. Recent advances in various classes of ADCs for different applications are described.
The channelized receiver being presented demonstrates the use of high temperature superconductor technology in a microwave system setting where superconductor, microwave-monolithic-integrated-circuit and hybrid-integrated-circuit components are united in one package and cooled to liquid-nitrogen temperatures. The receiver consists of a superconducting X-band four-channel demultiplexer with 100-MHz-wide channels, four commercial monolithically integrated mixers, and four custom-designed hybrid-circuit detectors containing heterostructure ramp diodes. The composite receiver unit has been integrated into the payload of the second-phase NRL high temperature superconductor space experiment (HTSSE-II). Prior to payload assembly, the response characteristics of the receiver were measured as functions of frequency, temperature, and drive levels. The article describes the circuitry, discusses the key issues related to design and implementation, and summarizes the experimental results.