Electric lamp and discharge devices: systems – Cathode ray tube circuits – Combined cathode ray tube and circuit element structure
Reexamination Certificate
1994-11-18
2001-10-16
Lee, Bennt T. (Department: 2817)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Combined cathode ray tube and circuit element structure
C315S005330, C313S293000, C313S447000
Reexamination Certificate
active
06304033
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an electron beam tube having input resonator cavity through which a high-frequency control voltage is applied between cathode and grid of the tube, while an annular electrode connected in an electrically conducting manner to the grid of the tube is arranged opposite a metal wall of the input resonator cavity and is connected to a DC power supply lead.
Such an arrangement is described in GB-A 2 259 708. In the arrangement described in this document a ceramic material cylinder enclosing a cathode, an anode and a grid is surrounded by a coating of silicon rubber comprising ferrite particles. Self-oscillations of a resonant circuit present between the anode and the grid are prevented thereby. Such self-oscillations may also occur between the cathode and the grid and then cause interference modulation of the electron beam, and in extreme cases may even lead to destruction of the tube.
It was found that disturbing self-oscillations occur in spite of the measures taken in the known case.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide more effective measures for suppressing interference oscillations in an arrangement of the type described in the opening paragraph.
This is achieved in that high-frequency damping material is associated with the DC power supply lead on a part of the length located proximate to the annular electrode.
The invention is based on the recognition that resonant circuits whose resonance frequencies are in the range up to approximately 100 kHz are also formed by the inductance of the DC power supply lead in connection with capacitances which are inherent in tubes. These interference oscillations are damped by means of known high-frequency damping materials such as particularly ferrite or silicon carbide. The electric energy of the high-frequency field is absorbed by magnetic resonance or by a high dielectric loss factor in the high-frequency damping material.
A very effective damping is achieved in that the high-frequency damping material coaxially surrounds the part of the length of the DC power supply lead.
In a preferred, constructively favourable and effective solution, the high-frequency damping material is provided in a DC connection support of an input resonator arrangement.
Since the high-frequency damping material comprises a plurality of annular elements, the required quantity of damping material or the number of required ferrite rings can easily be adapted to any tube.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
REFERENCES:
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patent: 3622918 (1971-11-01), Ito et al.
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patent: 4119921 (1978-10-01), Warringa et al.
patent: 4146854 (1979-03-01), Ishino et al.
patent: 4527091 (1985-07-01), Preist
patent: 4760312 (1988-07-01), Watanabe et al.
patent: 2259708 (1993-03-01), None
patent: 4073841 (1992-03-01), None
patent: 9424690 (1994-10-01), None
Grote Stefan
Seidel Bernd
Lee Bennt T.
U.S. Philips Corporation
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