Amalia E. Barrios

A terrain parabolic equation model for propagation in the troposphere

A method to model tropospheric radiowave propagation over land in the presence of range-dependent refractivity is presented. The terrain parabolic equation model (TPEM), is based on the split-step Fourier algorithm to solve the parabolic wave equation, which has been shown to be numerically efficient. Comparisons between TPEM, other terrain models (SEKE, GTD, FDPEM), and experimental data show predominantly excellent agreement. TPEM is also compared to results from an experiment in the Arizona desert in which range-dependent refractive conditions were measured. Although horizontal polarization is used in the implementation of the model, vertical polarization is also discussed. >

Parabolic equation modeling in horizontally inhomogeneous environments

A parabolic equation model has been developed for use in tropospheric radiowave propagation. A simple technique to model range-dependent environments has been implemented. Results from the model are compared with experimental data at 170, 520, 3240, 3300, and 9875 MHz in measured range-dependent environments. The experimental data are taken from two separate experiments performed during 1947 and 1948. Measurements were made on overwater paths from Guadalupe Island to San Diego, CA, in one experiment, and the other was located in the South Island of New Zealand, also known as the Canterbury Project. The results are presented as one-way propagation factor in decibels versus height. The technique used to model range-dependent environments is shown to give a reasonably good estimate of the environment between measurements, leading to excellent agreement between the predicted fields and observed radio data. >

Low Altitude Propagation Effects — A Validation Study of the Advanced Propagation Model (APM) for Mobile Radio Applications

VHF signal strength data from two NOAA weather radio transmitters, located in southern California and southwestern Arizona, were collected over a wide range of topography ranging from relatively flat to mountainous terrain. Signal strength data were collected using a mobile receiver traveling from 20 km to over 100 km, with the receiving antenna at a constant height of 2.2 meters above the ground. Meteorological information was obtained from local radiosonde measurement stations at Miramar (NKX) and Yuma Proving Ground (1Y7). This data is used as the basis for a validation study of the Advanced Propagation Model (APM) to determine its applicability for low altitude mobile radio communications applications over terrain

Multiple Grazing Angle Sea Clutter Modeling

Radar clutter in a non-standard atmosphere usually is modeled based on a single grazing angle at each range. Instead, the angular distribution of incident power can be used to obtain a more accurate model of the clutter. Angular spectral estimation provides the grazing angle distribution of propagating power. However, a large gradient in the refractivity profile, e.g., an evaporation duct, distorts plane wave propagation which in turn violates assumptions of plane wave spectral estimation. Ray tracing is used in these situations, but has its own limitations (e.g., shadow zones). We suggest using curved wave spectral estimation (CWS) that yields reliable results for any refractivity profile, in contrast to plane wave spectral estimation. CWS is used to derive multiple grazing angle clutter, a model for ocean surface clutter in the microwave region that depends on all incident angles at each range and their corresponding powers.