Electric lamp and discharge devices: systems – Cathode ray tube circuits – Combined cathode ray tube and circuit element structure
Reexamination Certificate
2001-05-07
2003-12-30
Lee, Benny T. (Department: 2817)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Combined cathode ray tube and circuit element structure
Reexamination Certificate
active
06670760
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a collector of a traveling wave tube.
BACKGROUND OF THE INVENTION
FIGS. 4
,
5
(
a
),
5
(
b
) and
6
are longitudinal cross-sectional views of a conventional traveling wave tube. Specifically,
FIG. 4
shows a conduction cooling type,
FIG. 5
a forced air-cooling type and
FIG. 6
shows a water-cooling type.
FIG. 7
shows a longitudinal cross-sectional view of a conventional collector, while
FIG. 8
a
is a transverse cross-sectional view of another illustrative structure of a conventional collector and
FIG. 8
b
is a longitudinal cross-sectional view of
FIG. 8
a
.
FIG. 9
shows a two-stage version of the collector shown in FIG.
8
. Specifically,
FIGS. 9
a
and
9
b
are a transverse cross-sectional view and a longitudinal cross-sectional view of the collector, respectively.
Among the devices which effect amplification of the micro-wave, using an electron beam, there is a traveling wave tube used as a relay station for micro-waves and for satellite communication.
Referring to
FIGS. 4
,
5
(
a
),
5
(
b
) and
6
, a traveling wave tube includes an electron gun
23
for radiating an electron beam
24
, a delay wave circuit
25
for producing interaction between the electron beam
24
and the input micro-wave, a collector
26
for collecting the electron beam
24
and a beam converging device
27
for converging the electron beam
24
.
For increasing the efficiency of the traveling wave tube, a method known as a collector potential lowering method is used. This method consists in progressively lowering the potential applied across the collector electrode
28
(see
FIG. 4
) relative to the delay wave circuit
25
to lower the speed of the electron beam
24
colliding against the collector to decrease the energy generated in the collector electrode
28
. To this end, there is provided a collector-insulating ceramic element
36
for maintaining insulation between the collector
26
and the delay wave circuit
25
against high voltage.
The electron beam
24
emitted by the electron gun
23
traverses the delay wave circuit
25
to amplify a signal and is collected by the collector
26
. At this time, the electron beam
24
captured by the collector
26
has its kinetic energy converted into thermal energy to raise the temperature of a collector electrode
28
(see FIG.
4
).
For this reason, the heat generated in the collector electrode
28
(see
FIG. 4
) needs to be externally released. Among the methods for releasing the heat, there are a conduction cooling type collector
31
for releasing the heat from a base plate
30
to a heat sink
29
, as shown in
FIG. 4
, a forced air-cooling type collector
33
by providing a fin
32
on the outer periphery of the collector for flowing air thereon to release the heat with assistance from base plate
30
, as shown in
FIG. 5
, and a water-cooling type collector
35
by providing a water-cooled pipe
34
passed through by water to release the collector heat with assistance from base plate
30
, as shown in FIG.
6
.
Referring to
FIG. 7
, the collector structure of a conventional traveling wave tube includes an insulating enclosure
37
of ceramics etc. for insulating the collector electrode
28
, formed of copper, molybdenum or graphite etc., for maintaining vacuum and air-tightness, a base plate
30
for supporting the collector electrode
28
and passing heat generated in the collector electrode
28
through the insulating member to release heat to the outside and a collector-insulating ceramic element
36
for maintaining insulation against the delay wave circuit. These component parts are usually connected together by brazing or welding etc. This structure is termed an external insulation type collector
38
.
In the above-described collector, there are occasions where the collector electrode is displaced in the axial direction due to mechanical vibrations or impact. This positional deviation occasionally leads to changes in the colliding position of the electron beam leading to emission of gases or leading to an increased amount of retrogressive electrons to increase the helical current of the traveling wave tube, occasionally leading to destruction of the tube bulb.
Also, in such a collector structure, a problem arises in that RE components (TEM mode) of the electron beam incident on the collector are subjected to RE leakage through a collector lead line or collector-insulating ceramic element.
In JP Patent Kokai JP-A-2-101454 (1990), there is shown a structure in which the collector electrode
28
is supported by plural heat-conductive columnar ceramic elements
40
arranged between the collector electrode
28
and the external enclosure
41
to improve vibration-resistance and resistance against impact, while maintaining voltage withstand characteristics, as shown in
FIGS. 8
a
and
8
b
. This structure is termed an internal insulation type collector
39
.
In this type of collector, the outer enclosure
41
, collector electrode
28
and the highly heat-conductive columnar ceramic elements
40
are secured in position by deforming the outer enclosure
41
such as by press-working. If, in this structure, plural collector electrodes
28
, specifically a first collector electrode
42
and a second collector electrode
43
, are used and arranged in this order from the upstream to the downstream side of the electron beam, it is possible to lower the potential of the second collector electrode
43
relative to the first collector electrode
42
to improve the overall efficiency of the traveling wave tube.
A two-stage collector
44
is illustrated in FIGS.
9
(
a
) and
9
(
b
). An electron beam emitted by the electron gun is passed through the delay wave circuit to amplify the signal and is captured by the first collector electrode
42
and the second collector electrode
43
which are supported by heat-conductive columnar ceramic elements
40
.
For improving the efficiency of the traveling wave tube, there is usually employed a method of lowering the potential of the first collector electrode
42
to approximately 50% of that of the delay wave circuit and of lowering the potential of the second collector electrode
43
to approximately one-half that of the first collector electrode
42
. This method consists in sequentially lowering the collector potential with respect to the potential of the delay wave circuit to lower the speed of the electron beam impinging against the collector in order to lower the energy produced in each collector electrode while improving the overall efficiency of the traveling wave tube.
Referring to FIG.
9
(
b
), in the case of a two-stage internal insulation type collector
44
, it is necessary to take out a first collector lead wire
45
of the first collector electrode
42
to a position forwardly or rearwardly of the outer enclosure
41
. In the present case, the collector lead wire is taken out to a position rearward of the outer enclosure
41
and is passed through the inside of an insulator tube
46
for maintaining insulation of the first collector lead wire
45
to reduce the size of the collector as shown in FIG.
9
(
b
). This insulator tube
46
is led rearwardly of the collector via a groove
47
(see FIG.
9
(
a
)) formed in a portion of the outer periphery of the second collector electrode
43
so as to be led to outside vacuum in an insulated state from a second collector lead line
48
(see FIG.
9
(
b
)).
In this structure, the electrical field is unavoidably concentrated in an edge portion of the insulator tube
46
. Since there is a corner portion of the groove
47
in this edge portion, a problem arises in that the withstand voltage is deteriorated between the first collector lead line and the ground potential.
In addition to this structure, a demand is raised in recent years for providing a small-sized lightweight structure easy to manufacture for communication or loading on a satellite to lower the cost.
SUMMARY OF THE INVENTION
The above-described collector structure of the conventional traveling wave tube is vulnerable to RF l
Nobe Takeshi
Suzuki Wako
Lee Benny T.
NEC Microwave Tube, Ltd.
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