GLTRS--Glenn
TITLE AND SUBTITLE:
Computer Analysis of Spectrum Anomaly in 32-GHz Traveling-Wave Tube for Cassini Mission

AUTHOR(S):
James A.Dayton, Jr., Jeffrey D. Wilson, and Carol L. Kory

REPORT DATE:
February 1999

FUNDING NUMBERS:
WU-632-50-5D-00

PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135-3191

PERFORMING ORGANIZATION REPORT NUMBER:
E-11346

SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Washington, DC 20546-0001

REPORT TYPE AND DATES COVERED:
Technical Paper

SPONSORING/MONITORING AGENCY REPORT NUMBER:
NASA TP-1999-208691

SUPPLEMENTARY NOTES:
James A. Dayton, Jr. (retired) and Jeffrey D. Wilson, NASA Lewis Research Center; and Carol L. Kory, Analex
Corporation, 3001 Aerospace Parkway, Cleveland, Ohio 44135 (work funded under NAS3-27600). Responsible
person, Jeffrey D. Wilson, organization code 5620, (216) 433-3513.

ABSTRACT:
Computer modeling of the 32-GHz traveling-wave tube (TWT) for the Cassini Mission was conducted to explain the anomaly observed in the spectrum analysis of one of the flight-model tubes. The analysis indicated that the effect, manifested as a weak signal in the neighborhood of 35 GHz, was an intermodulation product of the 32-GHz drive signal with a 66.9-GHz oscillation induced by coupling to the second harmonic signal. The oscillation occurred only at low-radiofrequency (RF) drive power levels that are not expected during the Cassini Mission. The conclusion was that the anomaly was caused by a generic defect inadvertently incorporated in the geometric design of the slow-wave circuit and that it would not change as the TWT aged. The most probable effect of aging on tube performance would be a reduction in the electron beam current. The computer modeling indicated that although not likely to occur within the mission lifetime, a reduction in beam current would reduce or eliminate the anomaly but would do so at the cost of reduced RF output power.

SUBJECT TERMS:
Traveling-wave tube; Cassini; Ka-band; Slow-wave circuit

NUMBER OF PAGES:
12

PDF AVAILABLE FROM URL:
1999/TP-1999-208691.pdf
(131,210 KB)
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