An Empirical Estimate of the Contribution of Terrain Reflections to Interfering Signal Distributions

This paper is a report on a problem which is thought to have rather general interest in the field of radar and communications systems. This is the problem of interference caused by the reflection of pulsed radar signals from the terrain in the transmitter-receiver environs. This problem has proved to be rather intractable to handle analytically and therefore the empirical approach presented in this paper might be of special interest to those who have tried some analytic approach. Basically, the problem to which this paper addresses itself is as follows: Suppose it is desired to predict the number of pulses and their power levels, arriving at an unintended receiver from a radar transmitter. The task of predicting the direct pulses is difficult, but can be approached analytically; however, what can be done about predicting those pulses reflected from the terrain (or other objects) in the vicinity, especially when no detailed terrain information is available? during the study from which this paper arose, measured data was obtained at several selected sites in the San Diego area by tuning a test receiver to one of the identified, operating radar transmitters at a time. The number of pulses and their power levels were measured by the test equipment and recorded. This procedure was reported for several different transmitters at three test sites. At the same time, a computer program (called MSS-1) has been developed to predict the number of direct pulses and their power levels.