U.S. patent number 3,750,043 [Application Number 05/162,112] was granted by the patent office on 1973-07-31 for high frequency electronic devices.
This patent grant is currently assigned to Thomson-CSF. Invention is credited to Bernard Epsztein.
United States Patent |
3,750,043 |
Epsztein |
July 31, 1973 |
HIGH FREQUENCY ELECTRONIC DEVICES
Abstract
An electronic device wherein an interaction of an electron beam
and a high frequency wave propagating through a delay line is
achieved. The electron beam is made to strike substantially the
whole length of said delay line simultaneously, which line upon
this strike emits secondary electrons which are collected either by
a grid parallel to the delay line or by the surface itself of said
line. Such devices constituting either electronic amplifier or
storage tubes.
Inventors: |
Epsztein; Bernard (Paris,
FR) |
Assignee: |
Thomson-CSF (Paris,
FR)
|
Family
ID: |
9059538 |
Appl.
No.: |
05/162,112 |
Filed: |
July 13, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Jul 30, 1970 [FR] |
|
|
7028232 |
|
Current U.S.
Class: |
330/43; 315/5.12;
330/42; 365/118; 315/41; 330/44; 365/157 |
Current CPC
Class: |
G11C
11/22 (20130101); H01J 25/76 (20130101); H03H
9/423 (20130101) |
Current International
Class: |
H01J
25/76 (20060101); G11C 11/22 (20060101); H01J
25/00 (20060101); H03H 9/00 (20060101); H03H
9/42 (20060101); H03f 003/58 () |
Field of
Search: |
;315/39.3,3,4,5,6,7,41
;330/42,43,44 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kaufman; Nathan
Claims
What is claimed is :
1. Electronic device providing an interaction between a high
frequency wave and an electron beam comprising within an evacuated
envelope, an electron source delivering an adjustable electron
beam, a high frequency source delivering said high frequency wave,
a delay line for propagating said wave, first coupling means for
coupling said delay line to said high frequency source and
constituting the input of said device, second coupling means for
extracting said wave from said delay line and constituting the
output of said device, means for accelerating said electron beam
towards said delay line so that the electrons of said beam strike
simultaneously the whole effective length of said delay line, said
delay line emitting secondary electrons upon said strike of said
electron beam onto its surface, and means for collecting said
secondary electrons.
2. Electronic device according to claim 1 wherein said delay line
is made of an electric conductive material covered on its side
striked by said electron beam with a material emitting secondary
electrons upon said strike.
3. Electronic device according to claim 1 wherein said delay line
is made of a piezoelectric material.
4. Electronic device according to claim 3 wherein said
piezoelectric material emits secondary electrons upon said strike
of said electron beam.
5. Electronic device according to claim 3 wherein said
piezoelectric material is covered on its side striked by said
electron beam with a material emitting secondary electrons upon
said strike.
6. Electronic device according to claim 1 wherein said delay line
comprises several parts each one having its own said first and
second coupling means.
7. Electronic device according to claim 6 wherein means are
provided to deflect said electron beam onto one or the other of
said parts of said delay line.
8. Electronic device according to claim 1 wherein said means for
accelerating said electron beam towards said delay line comprise a
grid located in the vicinity of said surface of said delay line
striked by said electron beam and means for defining the potential
of said grid in a positive way relative to said electron
source.
9. Electronic device according to claim 8 wherein said potential of
said grid is furthermore defined so as said grid constitute said
means for collecting said secondary electrons and wherein said
surface of said delay line is covered with a thin film of an
electric conductive material connected to means for defining its
potential.
10. Electronic device according to claim 8 wherein said means for
collecting said secondary electrons is said surface of said delay
line striked by said electron beam.
11. Electronic tube for amplification of a high frequency signal
comprising an electronic device as claimed in claim 9, said tube
providing amplification of said wave applied to said delay
line.
12. Electronic tube for the storage of high frequency signals
comprising an electronic device as claimed in claim 10, said tube
providing storage of high frequency signals the duration of which
is less than, or equal to, the propagation time of said high
frequency wave to proceed over said delay line.
Description
The present invention relates to microwave electron tubes.
In this art the interaction between the electron beam and the
electric fields generated by the wave in a structure parallel to
the beam along which the wave propagates is utilized when it is
desired to amplify or delay a microwave, for example in a traveling
wave tube.
To provide for the interaction the wave velocity is reduced to a
value comparable to that of the electrons of the beam by suitable
selection of the delaying characteristics of the structure.
However, the microwave amplification of this type of mechanism is
subject to limitations including the difficulties entailed in the
efficient transfer of energy from the beam to the wave since the
said beam and wave are geometrically separate in parallel
planes.
The object of the present invention is to elimimate these
difficulties. For this purpose the relative shifts of the beam and
the wave are controlled in two perpendicular directions so that all
the electromagnetic fields traveling along the delay line interact
simultaneously with the beam. In addition, an increase in the beam
amplification results from the utilization of the secondary
electron emission at the point of impingement of the beam on the
delay line.
More specifically the invention relates to a microwave electron
tube comprising a wave delaying structure, an electron emission
source directing electrons onto the longitudinal surface of the
said structure, means controlling the said emission, and coupling
means injecting and ejecting the waves propagating in the said
structure, the secondary emission ratio of the structure being
greater than one when the structure is exposed to the said electron
emission.
The invention will be better understood from a consideration of the
ensuing description and by reference to the attached figures in
which :
FIG. 1 illustrates the assembly for one embodiment of an electronic
tube in accordance with the invention ;
FIG. 2 illustrates a detail of this tube ;
FIG. 3 illustrates another embodiment of the tube of FIG. 1 ;
FIG. 4 illustrates another electronic tube in accordance with the
invention ; and
FIG. 5 illustrates an electronic tube in accordance with the
invention provided with several inputs and outputs.
Every kind of electronic tube in accordance with the invention and
described hereinafter comprises, as shown on FIG. 1 for example,
within an evacuated envelope schematically represented in E, an
electron gun (1, 2, 3, 4) providing a wide electron beam (not
shown) and a delay line 5, of the interleaved kind for example,
located opposite the electron gun in such a way that said line is
bombarded by said electron beam simultaneously onto the almost
entirety of its length. A grid 10 the potential of which is
positive relative to the cathode 1 accelerates the electron beam
towards the delay line 5. Said delay line 5 is connected at one of
its extremities to a coupling device 6 applying thereto the
microwave to be processed while a second device 7 connected to the
other extremity of said line picks up the processed wave.
The electron gun comprises for example in a classical way an
electron-emisive cathode 1 heated by a winding 2, bunching and
deflection electrodes 3 and a beam current control electrode
constituted by the grid 4. Classical biasing means not represented
are also provided.
Thus, the processing of a microwave injected to the delay line 5 by
the coupling device 6 is provided in accordance with the invention
by an electron beam striking said line simultaneously onto its
whole effective length (except of course onto the coupling devices
6 and 7).
A convenient processing of said microwave, as concerning an
amplification as well as concerning a delay as described
hereinafter, is obtained in devices according to the invention with
delay lines exhibiting the phenomenon of secondary electrons
emission when bombarded by the electron beam emitted by the cathode
1. For this purpose, the delay line 5 is either covered with a
layer 8 of a material which will emit secondary electrons, or
constituted by a material exhibiting itself this phenomenon, this
depending on the embodiment considered.
In the embodiment illustrated by FIGS. 1 and 2, the delay line 5 is
constituted by an electric conductive material covered by a layer 8
of an electric insulating material which is able of emitting
secondary electrons when striked by the electron beam of the
electron gun.
Furthermore, in the tube here represented where the processing of
the microwave injected by the coupling device 6 is an
amplification, said layer 8 is covered with a thin film 9 of an
electric conductive material.
This film 9 is provided to permit electrical charges to circulate
through the delay line in such a way that the distribution of said
charges being continuously leveled out onto the surface of the
layer 8, the microwave to be processed may travel through the delay
line. The grid 10 has very high positive potential in relation to
the line 5 and collects secondary electrons produced by layer 8
when said layer is striked by the electron beam emitted by the
electron gun of the device. The thickness of the film 9 is choosen
to not disturb the passage of secondary electrons such
produced.
The high frequency energy to be amplified is introduced at the
input 6 of the delay line and is propagated along same, creating
between the elements thereof a system of moving electric and
magnetic fields which induce in the conductive elements of said
line an electric current whose value at any point is determined by
that of the said fields at said same point.
Under these conditions, permanent electron bombardment of the delay
line is carried out. For this purpose, from its cathode 1 the
electron-gun emits a beam of electrons which are focussed and
guided by the electrode 3, the intensity of the beam being
regulated by the grid 4 and its velocity by the grid 10 ; the
electrons strike the surface of the delay line after passing the
grid 10. Under the impact of the incident electrons, the layer of
material 8 emits secondary electrons which are immediately
attracted to and absorbed by the said grid. Potentials of the
various electrodes of the tube and layers 8 and 9 (thickness and
kind of material) are chosen so that the secondary emission
operates with a coefficient advantageoussly higher than unity and
that secondary electrons thus emitted by layer 8 have energy enough
to cross over the film 9, being afterwards catched by grid 10.
The distribution of the incident electrons is not uniform at the
surface of the delay line ; in other words, because of the presence
of the electric fields propagating through the line, the incident
electrons are attracted by zones corresponding to positive peaks in
the travelling wave. Under the impact of said incident electrons
said zones of layer 8 emit secondary electrons absorbed by grid 10.
Departure of said secondary electrons raises the corresponding
zones of the delay line (it has already been explained that these
zones coincide with the positive peaks in the travelling wave), to
a still higher positive potential.
The amplitude of the positive peaks due to the microwave alone, is
considerably increased by this mechanism of local augmenting of the
positive charges ; thus, the travelling microwave is amplified.
FIG. 3 illustrates another embodiment of an electronic tube in
accordance with the invention, differing from that of FIG. 1 solely
in terms of the type of delay line used.
Whereas the delay line 5 of FIG. 1 is of the electrical delay type,
that of FIG. 3 is of the mechanical type. In accordance with a
known embodiment, it is constituted by a plate 11 of a
piezoelectric material provided at its ends with two high frequency
coupling devices.
On this figure is only represented the beginning of the device
enclosed in an envelope (not shown) for constituting a tube . So,
one can see only the input coupling device (an equivalent output
coupling device being disposed identically at the end of said
device). Said input coupling device comprises for example an input
line 20 connected to the high frequency source (not shown) and
passing through the plate 11 by a hole 21 and connected to a piece
of an interleaved metallic line 12 laid on the surface of the plate
11 facing the electron gun (1, 2, 3, 4) in such a way that said
coupling device (20, 12) causes excitation of said plate 11. In the
embodiment here described said piece of line 11 is set on the plate
11 itself (it's the reason why it is represented by dashed lines) ;
this piece of line 11 might be set on layer 9 (not shown) providing
that an electric isolation is realised between said piece 11 and
said layer 9.
In this embodiment, the delay is of mechanical origin and
corresponds to the reduced velocity at which an acoustic wave
propagates through the piezoelectric material, said wave being
associated with the mechanical stresses produced by the propagation
of the electromagnetic wave ejected through the input coupler (20,
12).
In accordance with the invention, said delay line is covered, as in
the case of FIGS. 1 and 2, with a layer 8 of a material which
exhibits the secondary emission phenomenon, and a thin film 9 of a
conductive material. In some cases, the material of the plate 11
itself may exhibit the secondary emission phenomenon ; the layer 8
is then superfluous and the device is devoid of such a layer.
The operation of the device thus constituted is the same as that of
the one already described in relation to FIGS. 1 and 2.
FIG. 4 illustrates a variant embodiment of the electronic tube in
accordance with the invention, in which the processing operated
onto the high frequency signal injected to the delay line consists
in stocking for an arbitrary period of time an information which is
a very short portion of said high frequency signal.
This variant embodiment of a tube in accordance with the invention
is here described with a mechanical delay line constituted by a
plate 11 of a piezoelectric material as in FIG. 3. It is quite
clear that such a variant which consists in a storage tube for
stocking informations may also be realised with an electrical delay
line as that one of FIG. 1 for example.
Such storage tubes according to the invention are equivalent with
regard to their general conception to the amplifier tubes described
with reference to FIGS. 1 to 3. They only differ from said
amplifier tubes by the suppression of the conductive film 9 which
was laid on layer 8 in said tubes (FIGS. 2, 3) and by a different
setting of the potential of the grid 10.
This absence of film 9 enables static charges to accumulate thus
allowing the high frequency signal to be blocked in the manner
described hereinafter in the context of a piezoelectric delay
line.
A very short high frequency signal is ejected in the form of a
pulse through the input coupler of the delay line, electron
emission from the gun being inhibited by the grid 4. When the
pulse, in the form of a wave train of both electrical and
mechanical nature is fully contained on the surface of the line,
the grid 4 is used to unblock the electron-gun 1 for a very short
time, for example in the order of magnitude of, or less than, one
quarter of the periodicity of the high frequency signal.
The potential of the second grid 10 is so adjusted relative to that
one of the delay line that the impact of the electrons emitted by
said electron gun onto the surface of layer 8 liberates secondary
electrons the energy of which is such that they fall back onto the
insulating surface of the piezoelectric material, concentrating at
the regions of positive potential, that is to say where the wave
peaks occur , and remaining "trapped" there to thus form a
permanent electrostatic image of the wave at the instant of
bombardment ; these charge deposits create associated permanent
mechanical stresses inside the crystal.
An unblocking of the signal thus blocked onto the line may be
achieved by unblocking the electron-gun under the control of the
grid 4. The electron beam thus emitted gives rise to secondary
electrons which redistribute themselves onto the delay line at the
locations which have been precedently depopulated of electrons,
this having the effect of erasing the electrostatic and mechanical
record obtained during the afore-described blocking period. This
erasing cancels the electric charges thus releasing the internal
mechanical stresses and triggering two surface waves which
propagate in opposite directions. The one which propagates in the
same direction as the initially injected wave in a faithful
reconstitution of that wave and is picked up at the output coupler
(not shown).
The tube in accordance with this embodiment of the invention thus
makes it possible to arbitrarily delay a high frequency signal.
By way of example, the blocking or stocking time depends
essentially upon the insulation of the structures utilised to
conserve the electrostatic charges and can range from some few
microseconds to several months. The high frequency signal ranges
between some few megacycles per second and some few gigacycles per
second ; the duration of the pulse can be as much as 50
microseconds and the input power is less than some watts.
FIG. 5 illustrates a variant embodiment of the invention, where the
provision of several input couplers 12, 13 and 14, and several
output couplers (not shown), makes it possible to process several
different signals onto several parts of the delay line.
FIG. 5 illustrates a tube where the processing realised is an
amplification (see the presence of conductive film 9).
Such a variant embodiment may also concern storage tubes without
film 9.
The electron beam 15 can then be selectively applied to one of the
corresponding parts of the delay line, this by the application of
suitable potentials to the deflecting electrode 3 of the
electron-gun, when a separate processing of said parts is wanted,
or applied to the whole delay line for a simultaneous processing of
said parts.
This variant embodiment is described here with a mechanical delay
line ; it may also be realised with an electrical one.
* * * * *