DC and RF Measurements of Serial Bi-SQUID Arrays

TL;DR

This paper presents the design, fabrication, and measurement results of serial bi-SQUID arrays for low noise and broadband applications, demonstrating their linearity, gain, and noise performance aligned with mathematical models.

Contribution

It introduces integrated circuit designs of serial bi-SQUID SQIF arrays, providing experimental RF and DC measurement data and analysis, advancing superconducting quantum interference device technology.

Findings

Measured linearity, power gain, and noise temperature of arrays

Experimental results match mathematical modeling

Arrays fabricated on standard niobium process

Abstract

SQUID arrays are promising candidates for low profile antennas and low noise amplifier applications. We present the integrated circuit designs and results of DC and RF measurements of the wideband serial arrays based on integration of linear bi-SQUID cells forming a Superconducting Quantum Interference Filter (bi-SQUID SQIF). Various configurations of serial arrays designs are described. The measured linearity, power gain, and noise temperature are analyzed and compared. The experimental results are matched to results of mathematical modeling. A serial bi-SQUID SQIF arrays are mounted into a coplanar waveguide (CPW) and symmetrically grounded to corresponding sides of CPW. The RF output comes out from the central common line, which is also used for DC biasing and forms a symmetrical balanced output. The signal and DC flux biasing line is designed as coplanar lines passed in parallel over each bi-SQUID cell in a bidirectional fashion concentrating magnetic flux inside of each cell. Serial bi-SQUID SQIF arrays are fabricated on 5 mm x 5 mm chips using standard HYPRES niobium 4.5 kA/cm2 fabrication process.