VIRTUAL SOURCE LUNEBERG LENSES
NAVAL RESEARCH LAB WASHINGTON DC
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An investigation was made of the utility of a portion of a spherical Luneberg lens between 2 plane reflectors as a lens of reduced size and weight. If the reflectors pass through the center of the sphere, the resulting system produces several perfectly focused radiation beams, each appearing to originate from a virtual source on the surface of the full sphere. The virtual source positions and the position, beamwidth, and gain of the beams are accurately predicted from the spherical wedge angle and the source position. When the wedge angle is pip, where p is an integer, rays with p reflections form the beam having the greatest gain and a displacement from the wedge bisector equal to the source displacement. For applications in which only this principal beam is desired, the gain of the unwanted beams can be reduced by absorption, reflection, or illumination taper. Scanning is achieved by moving the feed along the surface of the spherical wedge if p is an odd integer, scanning can be obtained by moving the wedge past a fixed feed. Experimental data were taken on a 2-dimensional X-band model having a value of p 1. Satisfactory agreement existed with the predicted performance regarding beam position, beamwidth, and gain. The single, undesired beam was minimized by the use of absorbing material.
- Radiofrequency Wave Propagation