File:Varactor parametric amplifier 1958.jpg
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本预览的尺寸：632 × 600像素。 其他分辨率：253 × 240像素 | 506 × 480像素 | 809 × 768像素 | 1,064 × 1,010像素。
原始文件 （1,064 × 1,010像素，文件大小：178 KB，MIME类型：image/jpeg）
摘要
| 描述 |
English: The first varactor parametric amplifier, invented at Bell Labs in the late 1950s. Using 4 varactor diodes, it achieved 10 dB gain at 400 MHz. Parametric amplifiers are used as extremely low noise microwave amplifier stages in radio telescopes, spacecraft communication antennas, and military communications. The input microwave signal is amplified in a semiconductor varactor diode by applying a "pump" microwave signal at another frequency from a local oscillator. |
| 日期 | |
| 来源 | Retrieved October 19, 2014 from Radio-Electronic Engineering magazine, Ziff-Davis Publishing Co., New York, Vol. 29, No. 11, November 1958 , p. 24 on http://www.americanradiohistory.com |
| 作者 | 未知 |
| 授权 (二次使用本文件) |
This image is from an advertisement for American Telephone and Telegraph Co. without a copyright notice published in a 1958 magazine. In the United States, advertisements published in collective works (magazines and newspapers) are not covered by the copyright notice for the entire collective work. (See U.S. Copyright Office Circular 3, "Copyright Notice", page 3, "Contributions to Collective Works".) Since the advertisement was published before 1978 without a copyright notice, it falls into the public domain. |
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| 日期/时间 | 缩略图 | 大小 | 用户 | 备注 | |
|---|---|---|---|---|---|
| 当前 | 2015年2月16日 (一) 22:26 | | 1,064 × 1,010（178 KB） | wikimediacommons>Chetvorno | User created page with UploadWizard |
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