Cooperative band-stop filters

Shaoxiong Li, Jan B. Kycia

We have designed a superconducting quarter wavelength band stop filter which provides a high attenuation at approximately 7 GHz. Such filters were used as dc bias lines applied to whole wavelength and half wavelength superconducting resonators at two different extremes: voltage node and voltage antinode. The results obtained indicate that this filter can apply dc bias to arbitrary length superconducting coplanar waveguide resonators while maintaining high quality factor, Q∼15 000−18 000.

J. N. Hodgson

Alexandre Paquette, J. Griesmar, Gabriel Lavoie +5 more

We present an efficient fabrication method for absorptive microwave filters based on Eccosorb CR-124. Filters are fabricated from readily available parts, and their cutoff frequency can be set by their length. They exhibit desirable properties such as a very large and deep stop band with rejection beyond 120 dB at least up to 40 GHz, more than 10 dB return loss in both the pass and the stop band, and an error-function shaped step response without overshoot. Measurements at very low temperatures show that the filters thermalize on a time scale of approximately 100 s, and that they can absorb power as high as 100 nW with their noise temperature staying remarkably low, below 100 mK. These properties make the filters ideal for cryogenic filtering and filtering of intermediate frequency port signals of mixers.

Jerry A. Gelbwachs, Y. C. Chan

M. I. Salkola

Superconducting filter technology enables highly selective and sensitive base-station receivers for wireless communications. The performance analysis of a superconducting receiver, which is inherently a nonlinear system, is simplified by introducing the concept of an effective frequency response. With this approach, superconducting filters are shown to be ideal for applications that require steep rejection at the edges of a communication band. In contrast, filter nonlinearities decrease the order of the effective frequency response of a cascaded bandpass filter, thus reducing its stop-band rejection.

Li‐Wei Chou, Rose, Conway +1 more