DC and RF Measurements of Serial Bi-SQUID Arrays

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/cm 2 fabrication process.Index Terms-noise temperature, broadband, electrically small antenna, low noise amplifier, high sensitivity, high linearity

Signal and noise characteristics of bi-SQUID

“…This relation is truly valid only at l << 1 when the pulse component is negligibly small and, together with one of the "phase" equations (8) or (11), describes voltage response of either dc SQID or bi-SQUID at the limit as explicit and implicit functions, correspondingly.…”

From single SQUID to superconducting quantum arrays

“…One can mention broadband lownoise amplifiers (e.g., see design approaches in [4,5]) as well as broadband active electrically small antennas (ESAs) capable of providing concurrent receiving and amplification of the broadband electromagnetic signals. The SQAs are also beneficial for many applications, in which SQUIDs and SQUID arrays are being used [1,2,36].…”

“…Integrating such a SQA with a broadband input line to apply an input magnetic signal to all array cells (see, for example, the designs proposed in [4,5]), one can design a high-performance broadband amplifier. Moreover, an active electrically small antenna (ESA) can be developed on the basis of SQA to implement simultaneously broadband reception and amplification of electromagnetic signals.…”

Thin‐Film‐Based Integrated High‐Transition‐Temperature Superconductor Devices

“…Thus, the effective bandwidth of the SQUID can have significant improvement by using this bi‐SQUID architecture . Serial arrays of such bi‐SQUID structure can be designed to improve the device characteristics with emphasis on its dynamic range …”