Defence, automotive and electronics conglomerate TRW Inc has produced what it believes to be the most advanced working circuit using high-temperature superconductors. The breakthrough came as TRW’s Space & Technology Group was developing reproducible superfast switches, known as Josephson junctions, for the circuit. Containing four active devices, TRW’s circuit is a four-bit, analogue-to-digital converter made from the rare earth compound yttrium barium copper oxide, which apparently, is often referred to as the 1-2-3 compound. Such circuits transform ordinary analogue signals into the bits and bytes used by digital signal processing circuits found in computers and other modern electronic devices. The circuit incorporates superconductors which operate between 40 degrees and 77 degrees Kelvin (-420 to -360 degrees Fahrenheit). Superconductors made from easier-to-process metals typically operate between four and eight degrees Kelvin (-495 degrees Fahrenheit). TRW used Josephson junctions to produce the superfast switches in high-quality superconductor films. IBM used to have a Josephson Junction project which it abandoned several years ago. However, the Japanese have managed to develop the technology to the point where the Electrotechnical Laboratory of Japan’s Agency of Industrial Science & Technology says it has a complete Josephson computer (CI No 1,337), while Fujitsu has an 8-bit Josephson signal processor (CI No 1,381). TRW says that it will apply the process it has developed to many different electronic circuits from magnetic sen-sors and analogue-to-digital converters to microwave receivers and antennae. The cool temperatures at which the junctions operate make them ideal for use in spacecraft and satellites. TRW’s work is funded by the Defense Advanced Research Project Agency and is monitored by the Office of Naval Research as part of its high-temperature superconductivity development programme which is researching digital electronic systems for spacecraft.
