Efficiency of quasi-optical couplers |
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| Authors: | S. E. Schwarz |
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| Affiliation: | (1) Department of Electronic and Electrical Engineering, King's College London, Strand, WC2R 2LS London, England;(2) Present address: Department of Electrical Engineering & Computer Sciences, University of California, 94720 Berkeley, CA |
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| Abstract: | Millimeter-wave devices are often coupled to radiation by means of a feed antenna placed at the focus of a primary lens or mirror, a technique known as  quasioptical coupling . A general expression for the efficiency of such a coupler is derived.The efficiency of such a coupler depends on the relationship of the feed antenna pattern to the numerical aperture of the primary lens. An approximate general rule for coupler design is obtained. This rule is as follows. Let  o be the angle between the direction in which the feed pattern is maximum and the direction in which the pattern intensity has one-half its maximum value. Then the optimum numerical aperture of the primary lens is approximately sin (1.67 o). The effects of focussing errors and lens aberrations can also be calculated by this technique. |
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| Keywords: | millimeter waves antennas |
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