  We developed a novel magnetic coupling module formed of a monolayer
superconducting flux concentrator, which is integrated with a coplanar
resonator strongly coupled to HTS rf-SQUID. Three types of resonators,
including a long stripline resonator between input loop and pick-up loop of the
flux concentrator, a complementary split ring resonator (CSRR), and also a
spiral shape inside the input loop are explored. The resonance quality factors
as well as the coupling to the SQUID of different patterns of these three types
of the resonators is evaluated using Finite Element Method (FEM) simulations.
Several readout methods to couple the electronic system to the resonators are
tested, including inductive (coil) and capacitive (transmission line)
couplings, and the optimum readout is reported for each of the resonators.
Among the evaluated resonator types, a spiral shape resonator with optimal
design showing the highest quality factor (5900) together with the strongest
coupling to the SQUID (-0.5 dB) at resonance frequency of 836 MHz, is
fabricated using 200 nm thick superconducting YBCO on a 1 mm thick crystalline
LaAlO3 substrate. The flux concentrator of the module is optimized by the
variation of its linewidths and also its input loop radius to obtain maximum
flux transformation efficiency.
