October 1975 | NTIA Technical Memo OT TM 75-209
Computation of Propagation Effects for an Advanced Phased-Array Radar System, Volume I and II
Evan J. Dutton; Charles J. Chilton; R. F. Martin Jr.
A theoretical expression for the received signal by a radar is reduced to a utilitarian form by the introduction of feasible approximations and assumptions, with concern expressed for the need for evaluation of errors caused by these approximations and assumptions. The resultant expression is Fourier-transformed in order to evaluate the propagation medium transfer function.
It is determined that three propagation parameters influence the resultant transfer function -- medium attenuation, medium phase delay, and mechanism reflectivity. These parameters are then derived in terms of fairly simple expressions that are suitable for a first-order off-line propagation model in the 5.25 to 5.75 GHz range for the SAM-D radar. The parameters are derived for the various propagation media expected to be encountered; namely, terrain, clear air, atmospheric layering, turbulence, and precipitation.
An example is presented of the potential impact of errors on the analysis of propagation medium effects. A methodology for interfacing the developed off-line modeling procedures with the rest of the proposed radar system is discussed and recommendations are made for needed further work.
Consideration is given to the reception impact on the phased-array radar of interference caused by transmission from known sources that cannot be excluded by "1/d2 filtering." In addition the similar impact of jammers, irrespective of the type of jammer, is considered.
The results of computer simulation for some sample situations are then presented (not including interferers or jammers) in an attempt to demonstrate the impact of the various propagation mechanisms that are considered.
Volume l: Text
Volume II: Appendices
Keywords: terrain effects; atmospheric errors; phase-coherent C- and X-band radar; propagation effects