Low-Noise Cryogenic Amplifier built using Hybrid MMIC-like / TRL Technique
Conference contribution, 2008
HEMT cryogenic low-noise amplifiers are an important part of instrumentation: the amplifiers
use as a front-end for different measurements and as IF amplifiers in heterodyne receivers.
During last few years the low-noise limit has reached as low level as approximately 0.5 K/GHz
for GaAs  and 0.25 K/GHz for InP HEMT . However, besides electrical performance
improvement there were not many improvements on mass and dimension side of such
amplifiers as they were built based on standard TRL technology with discrete active and
passive components. Mass and dimensions are also very important for real applications. When
ultimate low-noise performance is placed in focus, pure MMIC technology seems to loose
against design using discrete components. With this in view, pioneered work by E. F. Lauria,
et. al.  have successfully demonstrated a design employing MMIC approach while using
discrete components and based on a microstrip on Cuflon with lumped bias network.
Encouraged by this work, we propose a compact design of a 4-8 GHz cryogenic low noise
amplifier using a combination of standard TRL and lumped element technology to achieve
both ultimate noise performance over the specified band and a very compact size. In our
design, the size reduction of the amplifier is realized by selecting an alumina substrate with a
high dielectric constant, (εr = 9.9), but also by taking advantage of the lumped networks in the
matching and bias circuitries. Avoiding quarter wave transformers and instead use a lumped
element design approach opens up for the possibilities to reach greater bandwidths and
simultaneously obtain a more compact design. In order to make optimum design, we have
performed extensive simulations. Each amplifier stage has been simulated in Agilent EMDS,
3D electromagnetic field simulation package, including the single layer capacitors, and then
implemented in the ADS circuit simulations as an S-parameter file. Over the 4-8 GHz band, the
simulations predict noise temperature, Taverage < 4.3 K, S11 < -12 dB, S22 < -15 dB, and a gain,
S21 > 35 dB. The transistors selected for the design are commercial InP HEMT (HRL) chosen
due to their excellent noise performance , but also for the very low power consumption,
which is of great importance at cryogenic temperatures. All the components used in the RFsignal
path and in the bias circuits are mounted with conductive epoxy. Apart from the RFsignal
path, all components are interconnected via bond-wires. Fine tuning is done by adjusting
the length and loop heights of the bond-wires. At the conference we plan to report results of
measurement and characterization of the prototype amplifier.
 C Risacher, et. al., “Low Noise and Low Power Consumption Cryogenic Amplifiers for
Onsala and Apex Telescopes”, Proceedings of Gaas 2004, October 2004, Amsterdam.
 N. Wadefalk, et. al., “Cryogenic Wide-Band Ultra-Low Noise IF Amplifier Operating at
Ultra-Low DC-Power”, IEEE Transactions on Microwave Theory and Techniques, vol. MTT-
51, no. 6 June 2003.
 E. F. Lauria, et. al., “A 200-300 GHz SIS Mixer-Preamplifier with 8 GHz IF Bandwidth”,
2001 IEEE International Microwave Symposium, Phoenix, AZ, May 2001.
Low-noise cryogenic amplifier