2 research outputs found
Scattering Parameter Measurements of the Long Wavelength Array Antenna and Front End Electronics
We present recent 2-port vector network analyzer (VNA) measurements of the
complete set of scattering parameters for the antenna used within the Long
Wavelength Array (LWA) and the associated front end electronics (FEEs). Full
scattering parameter measurements of the antenna yield not only the reflection
coefficient for each polarization, S11 and S22, but also the coupling between
polarizations, S12 and S21. These had been previously modeled using
simulations, but direct measurements had not been obtained until now. The
measurements are used to derive a frequency dependent impedance mismatch factor
(IMF) which represents the fraction of power that is passed through the
antenna-FEE interface and not reflected due to a mismatch between the impedance
of the antenna and the impedance of the FEE. We also present results from a two
antenna experiment where each antenna is hooked up to a separate port on the
VNA. This allows for cross-antenna coupling to be measured for all four
possible polarization combinations. Finally, we apply the newly measured IMF
and FEE forward gain corrections to LWA data to investigate how well they
remove instrumental effects.Comment: 16 pages, 12 figures, Accepted for publication in Publications of the
Astronomical Society of the Pacifi