The physics mechanisms of detection of microwave electromagnetic radiation
of X- and Ka-band by superconducting nonlinear elements were considered. As
the nonlinear elements the high-temperature superconducting (HTS) YBCO
bicrystal Josephson junctions were chosen. The array of Josephson junctions
was embedded in the surface wave resonator (SWR). This resonator consists of
HTS YBCO film with array of junctions on a dielectric substrate with
bicrystal grain boundary (yttrium-stabilized zirconium substrate). The
junctions were shunted by thin layer of gold in order to achieve a
non-hysteresis current-voltage characteristic of the array and to decrease
the scattering of junction parameters.
In known similar systems the Josephson junctions are series dc and series ac
coupled, so excitation conditions for junctions are unequal. In proposed
excitation system on the base of the SWR the junctions are series dc but
parallel ac coupled, so the excitation is the same for each junction in the
Josephson junction array. Using this excitation method a new class of
microwave devices with lower utilized power and greater sensitivity can be
designed.
Detecting of a microwave signal by a Josephson junction array embedded in
the SWR was experimentally studied. Measurements were carried out starting
from critical temperature of the HTS film and down to the hydrogen level
using the Gifford-McMohon closed-cycle cryo-cooler. The sensitivity of such
type of detectors was measured. It was approximately 10⁴ V/W.
So the excitation method by the surface wave resonator allows using the
systems with parallel ac biased synchronized HTS Josephson junctions. Such
microwave detectors on the basis of Josephson junction arrays embedded in
the SWR has higher sensitivity and increased dynamic range.

Key Words: Josephson junction, surface wave resonator, microwave detector.

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