March 1975 | NTIA Technical Memo OT TM 75 195

Modeling propagation effects for an advanced phased-array radar system

Evan J. Dutton; Charles J. Chilton

Abstract: A theoretical expression for the received signal by a radar is reduced to a utilitarian form by the introduction of feasible first order approximations, and specifying where other common assumptions are made, with concern expressed for the need for evaluation of errors caused by these approximations and assumptions. The resultant expression is Fourier­transformed 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 4-12 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 and turbulence, and precipitation. An example is presented of the potential impact of errors on the analysis of propagation medium effects. A discussion of interfacing the developed off-line modeling procedures with the rest of the proposed radar system is discussed and recommendations for needed further work in test and evaluation to statistically assess error impact, as well as recommendations for the on-line modeling needs are made.

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