Impedance and Radiation Characteristics of a Ferrite Obstacle in the Aperture of a Rectangular Waveguide

摘要

A theoretical and experimental investigation is made of a magnetized ferrite obstacle in a rectangular waveguide having an additional discontinuity. The analysis is performed on right cylindrical obstacles (not necessarily circular) together with discontinuities that excite little or no field variations along the cylinder axis. The axis of the obstacle is parallel to the electric field corresponding to the TE sub 10 mode of the rectangular waveguide. The main application of the study is to the case where the discontinuity is an aperture (i.e., the waveguide radiates into free space) and the ferrite obstacle is placed directly in the aperture. This composite antenna structure is shown to be capable of being electronically scanned. The direction of the radiated beam is controlled by the magnitude of the applied magnetic bias field. Scanning over a total range of 60 degrees with good efficiency and reflection characteristics is obtained experimentally at frequencies around 10 Gc/sec. The applied magnetizing fields are less than 300 oersteds for this range of scanning. The antenna has the novel property of being nonreciprocal, the receiving and transmitting beam patterns are mirror images of each other. This is a new antenna and is one of only a few existing types of single element, electronic scanning devices. The small size and weight make it suitable for airborne and mobile equipment. (Author)