[Show abstract][Hide abstract] ABSTRACT: We report on the noise of a lumped element Direct Current Superconducting
Quantum Interference Device amplifier. We show that the noise temperature in
the 4 GHz-8 GHz range over ranges of 10's of MHz is below 1 kelvin (three
photons of added noise), characterize the overall behavior of the noise as a
function of bias parameters, and discuss potential mechanisms which determine
the noise performance in this amplifier. We show that this device can provide
more than a factor of 10 improvement in practical system noise over existing
phase-preserving microwave measurement systems in this frequency band.
[Show abstract][Hide abstract] ABSTRACT: We describe the performance of amplifiers in the 4 GHz--8 GHz range using
Direct Current Superconducting Quantum Interference Devices(DC SQUIDs) in a
lumped element configuration. We have used external impedance transformers to
couple power into and out of the DC SQUIDs. By choosing appropriate values for
coupling capacitors, resonator lengths and output component values, we have
demonstrated useful gains in several frequency ranges with different
bandwidths, showing over 27 GHz of power gain-bandwidth product. In this work,
we describe our design for the 4 GHz--8 GHz range and present data
demonstrating gain, bandwidth, dynamic range, and drift characteristics.
Preview · Article · Aug 2009 · Applied Physics Letters
[Show abstract][Hide abstract] ABSTRACT: Due to their superior noise performance, superconducting quantum interference devices (SQUIDs) are an attractive alternative to high electron mobility transistors for constructing ultra-low-noise microwave amplifiers for cryogenic use. We describe the use of a lumped element SQUID inductively coupled to a quarter wave resonator. The resonator acts as an impedance transformer and also makes it possible to accurately measure the input impedance and intrinsic microwave characteristics of the SQUID. We present a model for input impedance and gain, compare it to the measured scattering parameters, and describe how to use the model for the systematic design of low-noise microwave amplifiers with a wide range of performance characteristics.
Preview · Article · Aug 2008 · Applied Physics Letters