DEVELOPMENT OF A PERIODICALLY FOCUSED LOW-NOISE TRAVELING-WAVE TUBE LIMITER.
Abstract
It was demonstrated that the dips or nulls in output power of traveling-wave tubes are primarily due to variation of helix phase velocity, rather than being basic to the saturation properties of an electron beam. As a result, a design procedure for wide-dynamic-range limiters was evolved which is applicable to higher power tubes as well. As a result of this work, it is possible to design limiter tubes which do not require 'hand tailoring' of external attenuators. However, careful control of helix fabrication is required to obtain reproducible tube performance. Both compensated-ferrite magnets and Alnico VII magnets were used for focusing. The superiority of Alnico VII magnets with respect to operation over a wide temperature range was demonstrated. Three engineering sample tubes were delivered on the contract. The dynamic range (defined as the input power range over which the output power was between +5 and +15 dbm) varied from 42 db to 50 db. While the actual tubes delivered fell somewhat short of the contract objective of operation between -55 dbm and zero dbm, it is believed that the basic design principles required to achieve this performance were demonstrated. The problem remaining consists of the development of helix fabrication techniques which will allow sufficient control of the helix phase velocity over the length of output helix required for gain, and also will permit fabrication of such helices on a reproducible basis. The tubes developed on this contract had noise figures on the order of 15 db. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1961
- Accession Number
- AD0649883