Graduate School in Nonlinear Science

Sponsored by the Danish Research Academy

S-Band DC SQUID Amplifier

by Ph.D. Student Georgy Prokopenko
Institute of Radio Engineering and Electronics
Russian Academy of Sciences
Mokhovaya 11, 103907
Phone: (007) 095 203 2784
Fax: (007) 095 203 8414

MIDIT-seminar No. 403

Thursday, April 02, 14:00 h
at MIDIT, IMM Building 305, room 027

Abstract: The dc SQUID based RF amplifier (SQA) is advantageous for integration with a SIS mixer and a flux-flow oscillator (FFO) in a fully superconducting submm wave receiver due to its low noise, low power consumption and excellent compatibility with both the SIS mixer and the FFO. A 6 mm X 6 mm chip comprising two identical SQAs has been designed, fabricated and tested in the frequency range 3.5-4.0 GHz as a two-stage RF amplifier. Each SQA consists of a double washer type dc SQUID with two ~1 mm 2 area Nb-AlOx-Nb junctions shunted by Ti film resistor. The integrated input resonant circuit consists of a coil and two tuning capacitors. The reflection coefficient of both the input and the output of the SQA has been measured in the two-stage configuration using a directional coupler and a synthesized signal generator. A tuneable 40 MHz band-pass YIG-filter is used at the input of SQA to avoid its saturation. The following characteristics of the two-stage SQA have been measured at 3.7 GHz using a test noise input signal: gain 17±1 dB, noise temperature 5.5±1 K and 3 dB - bandwidth of 220 MHz. The gain of 19±1 dB and a noise temperature as low as 3±1 K could be estimated if the measured RF mismatch between the input of SQA and source signal is taken into account.