A circular-polarization duplexer for millimeter waves

This paper describes a circular-polarization duplexer for use in the millimeter (mm) wavelength range. Such a duplexer finds its field of application in any system which utilizes the same antenna for simultaneous transmission and reception, for example, a continuous-wave radar. The mm wavelengths are here defined as covering the range from 1 to 10 mm (frequency range 30,000 to 300,000 megacycles).1 Much interest has been shown in these frequencies because of the possibility of directive high-gain antennas of small size and because of atmospheric properties peculiar to the mm range such as absorption by oxygen and water vapor.2??4