Low-noise amplifier design and optimization

Abstract: Low-Noise Amplifiers are key components in the receiving end of nearly
every communications system. The wanted input signal of these systems is
usually very weak and the primary purpose of the LNA is consequently to
amplify the signal while at the same time adding as little additional noise
as possible. Its performance is measured in a number of figures of merit
among which gain and noise figure are most notable while dynamic range,
return loss and stability are examples of others.
In May 2005 a four year design study entitled EISCAT_3D was initialized.
Its purpose was to investigate the feasibility of a next-generation
incoherent scatter radar system. One of the responsibilities of EISLAB at
Luleå University of Technology is to design a receiver front-end, which
include an LNA with extremely high performance requirements. For that
reason a MATLAB Particle Swarm Optimization implementation was developed to
iteratively find a solution to optimal component values for a user
definable LNA topology.
In this master's thesis, the radio frequency concepts essential to
traditional LNA design as well as the design procedure itself are
explained. A description to the optimizer is then given, including a
chapter on 2-port noise calculations.
With the objective to find an LNA design with even higher performance than
the previously designed EISCAT_3D LNA, four topologies are evaluated using
the optimizer while consistently targeting the EISCAT_3D specifications.
These topologies include the original reference design and one that employs
the inductive source degeneration design technique. The latter showed
significantly improved performance with an approximate 2 dB gain increase
and 0.1 dB noise figure reduction while still maintaining the return loss
and stability requirements.