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Summary
| Description |
English: Prototype metallic lens antenna for 6 GHz microwaves, developed at Bell Labs in 1946 by Winston E. Kock, shown standing next to it. It consists of a 10 ft × 10 ft vertical lattice of parallel metal strips in the form of a Fresnel lens. Microwaves from a feed horn behind the antenna pass through the lattice, which focuses them into a parallel beam. The spaces between the strips act as waveguides. It functions similarly to a convex optical lens, slowing the velocity of the waves passing through the center, while increasing the velocity of the waves through the periphery. However in a converging optical lens the glass slows the speed of the waves, so the lens is made thicker in the center than the edges. In the microwave lens the waveguides actually increase the speed (phase velocity) of the microwaves, and thus have an index of refraction less than one, so to make a converging lens it must have a concave shape, thicker in the peripheral regions and thinner in the center. This antenna was used in the first microwave relay stations built by AT&T's Long Lines division in the 1950s. Lens antennas were also used in military radar. |
| Date | |
| Source | Retrieved October 17, 2015 from Jordan McQuay, "Antenna Principles Part 8 - Metallic Lens and Electromagnetic Horn Antennas" in Radio Craft magazine, Radcraft Publications, Springfield, MA, Vol. 18, No. 10, July 1947, p. 39, fig. A archived on http://www.americanradiohistory.com |
| Author | Unknown author |
| Permission (Reusing this file) |
This 1947 issue of Radio-Craft magazine would have the copyright renewed in 1975. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. Search of the Renewals for Periodicals for 1974, 1975, and 1976 show no renewal entries for Radio-Craft. Therefore the copyright was not renewed and it is in the public domain. |
Licensing
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This work is in the public domain because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs. Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 13:07, 17 October 2015 | | 708 × 695 (138 KB) | Chetvorno | User created page with UploadWizard |
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