TABLE OF CONTENTS The antenna is an extremely important part of radar. It must couple the energy from the radar to and from space; it must radiate in the desired direction and discriminate against receiving radiation from other directions. The ELINT-observable antenna parameters are chiefly its polarization characteristics, the shape of its main beam, and its sidelobe levels. This chapter begins by considering aspects of polarization and continues with consideration of beam shape and sidelobe levels.
The polarization of an electromagnetic wave is described by the geometric figure traced by the electric field vector as the wave travels through space. [2.] The polarization of the transmitted radar signal can be determined at an ELINT station by specialized measurement equipment or simply by manually determining which polarization of the ELINT antenna provides the greatest signal strength from the transmitter. For electronic warfare purposes, it is important to determine the polarization because the effectiveness of a jammer having improper polarization is reduced.
[1.] The author is grateful for the help of Mr. Grover M. Boose in preparing the polarization sections.
[2.] This is the convention in electrical engineering. In physics and optics, polarization refers to the magnetic field vector.
The geometric figure traced by the electric field vector is, in general, an ellipse. Under some conditions the ellipse may collapse into a straight line, in which case the polarization is called linear. In the other extreme, the ellipse may become circular. Thus, linear...
