Measurements of Selective Near-In Sidelobe Reduction of a Pyramidal, Horn-Reflector Antenna

Measurements of Selective Near-ln Sidelobe Reduction of a Pyramidal, Horn-Reflector Antenna By R. A. SEMPLAK ( M a n u s c r i p t r e c e i v e d J a n u a r y 18, 1 9 8 2 ) This paper describes measurements of a simple but effective means for reducing selective near-in sidelobe levels of a pyramidal hornreflector antenna by using microwave absorber to modify the electric field across the reflector surface of the horn-reflector antenna. Examples of several modifications (made in the transverse plane for transverse polarization) are discussed and compared with data obtained before modification. Good reductions are achieved in the region of 2 to 6 degrees from the main beam. For example, an improvement was obtained on the order of 4 dB in the first sidelobe level with corresponding improvements of 8 and 10 dB in the angular region of the second and third sidelobe levels. One would expect some of the far-out sidelobe regions to increase; however, the reductions obtained in the levels of the near-in sidelobes could warrant a tradeoff. I. INTRODUCTION It is well known that radio interference from adjacent paths limits the number of converging routes of a common carrier microwave radio system, and in recent years demands have been made to improve the sidelobe performance of the pyramidal, horn-reflector antenna. The use of blinders1 (stepped extensions to the side walls of the antenna aperture) provide a degree of far sidelobe reduction, i.e., lobes beyond 595 MATERIAL: Q ECCO-SORB® 1 -INCH-WIDE AN-72, STRIP 1/' (a) Fig.