Superconductivity is
a phenomenon occurring in certain materials generally at very low temperatures,
characterized by exactly zero electrical resistance and the exclusion of the
interior magnetic field (the Meissner effect). It was discovered by Heike
Kamerlingh Onnes in 1911.
Applying the
principle of Superconductivity in microwave and millimeter-wave (mm-wave)
regions, components with superior performance can be fabricated. Major problem
during the earlier days was the that the cryogenic burden has been perceived as
too great compared to the performance advantage that could be realized. There
were very specialized applications, such as low-noise microwave and mm-wave
mixers and detectors, for the highly demanding radio astronomy applications
where the performance gained was worth the effort and complexity. With the
discovery of high temperature superconductors like copper oxide, rapid progress
was made in the field of microwave superconductivity.
This topic describes the properties of
superconductivity that can be exploited in microwave and mm-wave technologies
to yield components with appreciable performance enhancement over conventional
systems. Superconducting signal transmission lines can yield low attenuation,
zero-dispersion signal transmission behavior for signals with frequency
components less than about one tenth the superconducting energy gap. No other
known microwave device technology can provide a similar behavior.
Superconductors have also been used to make high speed digital circuits,
josephsons junction and RF and microwave filters for mobile phone base
stations.
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