FIELDS OF A HORIZONTAL LOOP ANTENNA OVER A LAYERED HALF-SPACE

We obtain an exact solution for a circular wire loop, carrying a non-u niform current, located above a layered half-space The method, while s traight-forward, allows for both T.E. and T.M. electromagnetic fields. The T.M. fields would not be present if the current distribution was uniform. As a consequence of the nonuniformity, vertically polarized r adio ground waves may be excited and such could be a source of unwante d interference. Such loop sources are employed in geophysical probing schemes and it is suggested that the most desirable configuration woul d be if the vertical magnetic held is measured at the center of the ho rizontal loop. The contributions of the higher spatial harmonics of th e current in the loop vanishes in this case. On the other hand one may wish to employ such a source loop, lying on the earth's surface, to p rovide a useable radio ground wave for point-to-point communication ov er poorly conducting terrain such as in polar regions.