Presentation Information
[ED5-01-INV]Toward Large-Format Planar-Integrated Multi-Pixel SIS Heterodyne Receivers for Radio Astronomy
*Wenlei Shan1, Shohei Ezaki1 (1. National Astronomical Observatory, Japan (Japan))
Keywords:
SIS mixer,radio astronomy,MMIC
We are developing an innovative integration approach to realize compact focal-plane heterodyne detector arrays employing Superconductor-Insulator-Superconductor (SIS) mixers for wide field-of-view astronomical observations at millimeter and sub-millimeter wavelengths [1,2]. The core concepts include: (1) leveraging millimeter-wave monolithic integrated circuits (MMICs) to enable the use of compact planar orthomode transducers and hybrid bridges essential for balanced or sideband-separating mixer configurations; (2) adopting a semi-two-dimensional, buried-in metal waveguide network for local oscillator (LO) distribution; and (3) implementing LO coupling via membrane-supported waveguide probes integrated into the MMICs.
This approach goes beyond simply integrating known components on a chip. It introduces a range of new technical challenges arising from unconventional circuit designs and novel materials not typically used in traditional SIS mixers. Notably, we are investigating the impact of significantly longer superconducting transmission lines in MMICs [3], which differ fundamentally from those in conventional designs. In addition, a new thin-film resistor process is being developed to provide on-chip terminations for unused transmission line ports [4]. We also observe more pronounced self-heating effects in the SIS junctions, and we are actively studying the underlying mechanisms and their implications for mixer performance. These challenges present unique opportunities to deepen our understanding of SIS mixer physics and to explore the root causes of the persistent excess noise—often several times the quantum limit—seen in practical SIS mixer systems.
This approach goes beyond simply integrating known components on a chip. It introduces a range of new technical challenges arising from unconventional circuit designs and novel materials not typically used in traditional SIS mixers. Notably, we are investigating the impact of significantly longer superconducting transmission lines in MMICs [3], which differ fundamentally from those in conventional designs. In addition, a new thin-film resistor process is being developed to provide on-chip terminations for unused transmission line ports [4]. We also observe more pronounced self-heating effects in the SIS junctions, and we are actively studying the underlying mechanisms and their implications for mixer performance. These challenges present unique opportunities to deepen our understanding of SIS mixer physics and to explore the root causes of the persistent excess noise—often several times the quantum limit—seen in practical SIS mixer systems.