Courses - GPS 490
GPS 490 GNSS Receiver Antennas
(currently offered as non-credit (NC) only): Basics of
electromagnetic waves, polarization, antenna angular response
pattern and gain, polarization properties of GNSS user antennas,
phase pattern, phase center variations and antenna calibrations,
carrier phase multipath, reflections from the underlying terrain,
antenna down/up ratio, basics of transmission lines, antenna
mismatch and frequency response, cable losses, noise propagation
and signal-to-noise ratio.
GNSS receiver antennas are
treated from the user's point of view. The basics of
electromagnetic field theory are discussed at the level necessary
for understanding antenna performance parameters. Complex
notations and dB scale are introduced as basic tools for treating
performance. The antenna angular response pattern are presented
for transmitting and receiving modes with reciprocity theorem
serving to connect these two modes of operation.
We introduce the antenna
effective square. The topic of polarization properties are
addressed by using polarization transformations of type linear,
circular and elliptical. Polarization losses for the receiver
antenna are estimated.
The antenna phase center for GNSS
applications is rigorously defined as the reference point for
positioning for the limiting case when the satellite paths cover
the whole top the semi sphere in a continuous and homogeneous
manner. The elevation mask is taken into account. This approach
serves as a base for the treatment of antenna calibration
procedures. Phase center variations are discussed as phase pattern
residuals when the pattern is being transformed to the thus
defined phase center.
The plane reflective surface
model is used for estimating multipath from underplaying terrain.
The antenna down-up ratio is introduced and the multipath error is
being discussed for typical cases.
A detailed discussion of wave
propagation and reflections in transmission lines leads to the
treatment of antenna mismatch and frequency response. Typical
sources of noise for GNSS applications are analyzed, the
propagation of signal and noise through the electronic circuits is
discussed in detail; the role of the low noise amplifier (LNA) is
stressed.
This course concludes with a
section on estimating the signal to noise ratio at the receiver
input.
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