Directional Filter Design and Simulation for Superconducting On-Chip Filter-Banks

Journal of Low Temperature Physics, vol. 216, pp. 144–153

Abstract

Many superconducting on-chip filter-banks suffer from poor coupling to the detectors behind each filter. This is a problem intrinsic to the commonly used half-wavelength filter, which has a maximum theoretical coupling of 50 %. In this paper, we introduce a phase-coherent filter, called a directional filter, which has a theoretical coupling of 100 %. In order to study and compare different types of filter-banks, we first analyze the measured filter frequency scatter, losses, and spectral resolution of a DESHIMA 2.0 filter-bank chip. Based on measured fabrication tolerances and losses, we adapt the input parameters for our circuit simulations, quantitatively reproducing the measurements. We find that the frequency scatter is caused by nanometer-scale line width variations and that variances in the spectral resolution is caused by losses in the dielectric only. Finally, we include these realistic parameters in a full filter-bank model and simulate a wide range of spectral resolutions and oversampling values. For all cases, the directional filter-bank has significantly higher coupling to the detectors than the half-wave resonator filter-bank. The directional filter eliminates the need to use oversampling as a method to improve the total efficiency, instead capturing nearly all the power remaining after dielectric losses.

Authors 5

1. Louis H. Marting corresponding Aachen SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands · Delft University of Technology

   Affiliation as printed

   Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, Mekelweg 4, 2628 CD Delft, Zuid-Holland The Netherlands

   SRON-Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, Zuid-Holland The Netherlands

2. K. Karatsu Aachen SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON-Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, Zuid-Holland The Netherlands

3. Akira Endo

   Delft University of Technology

   Affiliation as printed

   Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, Mekelweg 4, 2628 CD Delft, Zuid-Holland The Netherlands

4. J. J. A. Baselmans Aachen SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands · Delft University of Technology

   Affiliation as printed

   Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, Mekelweg 4, 2628 CD Delft, Zuid-Holland The Netherlands

   SRON-Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, Zuid-Holland The Netherlands

5. Alejandro Pascual Laguna Aachen SRON Netherlands Institute for Space Research

   Consejo Superior de Investigaciones Científicas · Centro de Astrobiología · Space Research Organisation Netherlands · Delft University of Technology

   Affiliation as printed

   Centro de Astrobiología, CSIC-INTA, 28850 Torrejón de Ardoz, Madrid, Spain

   Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, Mekelweg 4, 2628 CD Delft, Zuid-Holland The Netherlands

   SRON-Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, Zuid-Holland The Netherlands