Superconducting quasi-lumped element filter on R-plane sapphire

Abstract

Recent advancement in superconducting microwave technology has led to commercial deployment of hightemperature superconducting (HTS) subsystems for wireless communication applications. Commercialization of the HTS thin-film devices lies within, among other factors, the quality and consistency of the HTS film, as well as the overall cost and performance of the subsystem. In this paper, we present the design and performance of a quasi-lumped element filter on sapphire substrate. Centered at 1857 MHz with 0.8% fractional bandwidth, the six-pole Chebyshev filter has an insertion loss of less than 0.2 dB at 60 K, which translates into a realized unload Q of 35 000. This is an important step toward the commercialization of superconducting devices using industrial standard wafers. With the continuous improvement of the HTS film quality, YBCO film on sapphire could be an answer to the future.

Planar superconducting lumped element bandpass filter with spiral inductors

“…This type of structures has very effective surface usage. The dimensions of this filter can be about 4 times smaller of the filter with half-loop inductor presented in [8]. Reported filter measurements are in good agreement with theory though a frequency shift about 30 MHz is present.…”

Coupling of Microwave Resonators to Feed Lines

“…Sapphire is well known to be an excellent microwave substrate because of its very low loss tangent of @ 4.2 K. The resonator samples were fabricated on a 300 R-cut sapphire substrate with an anisotropic value belonging to the c-axis orientation ( , ). Nevertheless, a dielectric constant of can be assumed if the planar structures are patterned with a certain angle to the c-axis [13].…”

Narrowband high temperature superconducting filter for mobile communication systems

“…The HTS filters have been attractive for mobile communications applications [1][2][3][4][5][6][7][8][9] since the rapidly increasing demand for mobile communications puts challenges on both technology and system to conserve valuable frequency spectrum and enhance the performance. The system benefits from the HTS filters are mainly due to their high selectivity and low insertion loss.…”

“…More attractively, as compared with MgO and lanthanum aluminate substrates, sapphire substrate can be made to a larger size at a lower cost. Therefore, there is increasing interest in using sapphire substrate for fabrication of the HTS filters [5][6][7][8][9].…”