Suppression of spurious harmonic responses in superconducting microstrip spiral filters using gold overlay and stagger tuning
Journal
IET MICROWAVES, ANTENNAS & PROPAGATION
Date Issued
2020
Author(s)
Huang, F
•
BOLLI, Pietro
•
MARIOTTI, SERGIO
Abstract
The higher order resonances of microwave superconducting filters with spiral resonators were suppressed, giving a very wide stop-band. In one filter spirals were modified to have equal fundamental resonances, but different higher order resonances, by adding stubs and using non-uniform line width. The higher resonances were reduced to −39 dB, in a stop band up to 4.3 times the pass band centre. In another filter, parasitic resistive resonators were added, suppressing the responses to −57 dB. The resistance is provided by patterning the 200 nm gold overlay already required for the external contacts. The increase in pass band loss is not measurable. Measurements of a single spiral resonator with a gold-YBCO bi-layer (200 and 600 nm respectively) suggest that the resistivity of the gold layer at 15 K is the order of 22 times that of bulk gold, a slight advantage for the present application. At 100 K, it is about double.
Volume
14
Issue
15
Start page
2123
Issn Identifier
1751-8725
Rights
open.access
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