U.S. patent number 3,735,293 [Application Number 05/142,574] was granted by the patent office on 1973-05-22 for high frequency cable.
This patent grant is currently assigned to Kabel-und Metallwerke Gutehoffnungshutte Aktiengesellschaft. Invention is credited to Otto Breitenbach.
United States Patent |
3,735,293 |
Breitenbach |
May 22, 1973 |
HIGH FREQUENCY CABLE
Abstract
A high frequency conductor systems for development of a partial
external field with one or two inner conductors extending along a
center line and surrounded by a dielectric substance; a tubular
outer conductor or shield, physically encloses the inner conductor
and the substance completely, and is constructed from serially
interconnected, axially juxtaposed conductor loops providing a
closed tube as well as a helical conduction path around said center
line.
Inventors: |
Breitenbach; Otto (Nurnberg,
DT) |
Assignee: |
Kabel-und Metallwerke
Gutehoffnungshutte Aktiengesellschaft (Hannover,
DT)
|
Family
ID: |
5770799 |
Appl.
No.: |
05/142,574 |
Filed: |
May 12, 1971 |
Foreign Application Priority Data
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|
|
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May 12, 1970 [DT] |
|
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P 20 22 990.7 |
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Current U.S.
Class: |
333/237;
343/771 |
Current CPC
Class: |
H01B
11/10 (20130101); H01P 3/00 (20130101); H01B
11/1808 (20130101) |
Current International
Class: |
H01B
11/18 (20060101); H01B 11/02 (20060101); H01B
11/10 (20060101); H01P 3/00 (20060101); H01p
001/00 (); H01q 013/22 () |
Field of
Search: |
;333/95,95A,95S,31C
;29/600 ;246/30 ;174/36,106,109,124 ;343/895 ;325/51,305,369
;179/82 ;191/10 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rolinec; Rudolph V.
Assistant Examiner: Nussbaum; Marvin
Claims
I claim:
1. A radiating, high frequency, coaxial conductor system having
inner and coaxial outer conductors provided for development of a
partial external field for utilization outside and along the outer
conductor, the improvement comprising:
the inner conductor as extending along a center line constructed
for current flow in axial direction along the center line;
a dielectric substance around the inner conductor and physically
enveloping the inner conductor; and
the outer conductor being tubular conductor, physically enclosing
the inner conductor and the substance completely and constructed
for establishing a helical path as exclusive flow path for electric
current flow around the said center line, there being no shield or
conductor around the outer conductor.
2. Conductor system as in claim 1
said outer, tubular conductor or shield constructed from serially
interconnected,axially juxtaposed conductor loops providing a
closed tube as well as a helical conduction path around said center
line.
3. Conductor system as in claim 1, the tubular outer conductor
constructed as a lay of wire or wires helically wound around the
center line, adjacent loops engage each other, the wire or wires
insulated at least to the extent that current flows essentially
only along the wires and not axially between adjacent loops.
4. Conductor system as in claim 1, the tubular outer conductor
constructed from helical wound metal strip.
5. Conductor system as in claim 1, the tubular outer conductor
constructed from a sheet with oblique slots, tubularly bent around
the center line.
6. The method of transmitting energy from a stationary transmitter
to a mobile receiver comprising the steps of placing a radiating
coaxial cable along the path of the receiver;
using in the cable an inner conductor as extending along a center
line and constructed for current flow in axial direction along the
center line, a dielectric substance around the inner conductor and
physically enveloping the inner conductor; and
using a tubular outer conductor in the cable, physically enclosing
the inner conductor and the substance completely and constructed
for establishing a helical path as exclusive flow path for electric
current flow around the said center line, there being no shield or
conductor around the outer conductor, so that a partial external
field develops along the cable for pick up by the mobile
receiver.
7. The method as in claim 6, using helically wound metal strip in
electrical insulation as to sequential loops as outer conductor of
the cable.
8. The method as in claim 6, using helically wound insulated wire
as outer conductor of the cable.
Description
The present invention relates to a high frequency cable and
conductor system of the type in which a partial field is developed
external to the cable and wherein a conductor or the conductors are
enveloped by dielectric material which, in turn, is enveloped by a
metallic shield.
High frequency signals are sometimes to be transmitted from a
stationary transmitter to a mobile receiver, or vice versa, and
often under special operating conditions. For example, rail
vehicles are to remain in contact with a station ahead, even while
passing through a tunnel, wherein regular h-f transmission would be
interrupted. For purposes of providing continued transmission, a
conductive system is required which, on one hand, permits
propagation of h-f energy at low losses, but, on the other hand,
the conductive system is to radiate such h-f energy at a particular
intensity along its extension. Such a conductive system, e.g., a
radiating cable, will be installed along the track and the vehicle
receiver may pick up signals anywhere along the cable.
For purposes of this transmission it is known to provide
symmetrical but unshielded h-f conductors; however, it was found
that the transmission characteristics of such conductor system
depends to a considerable extent on the condition of the
environment; weather, climate, etc., provide controlling parameters
for the intensity of radiation, as the overall impedance of the
cable varies accordingly. This is particularly true if the cable is
attached to ground.
Another type of radiating conductor is known which, to some extent,
can be regarded as approximation of a coaxial conductor system. The
system has inner and outer conductors, but the outer conductor has
an axial slot along the entire extension of the cable. The cable
radiates through that slot. The known radiating cables of that type
have the disadvantage that the electric field and signal strength
drops rapidly with (radial) distance from the cable. This is
particular due to the following. The field itself has a significant
stray component so that there are high dielectric losses and the
overall signal attenuation in such a system is therefore high.
Moreover, these dielectric losses are significantly dependent on
atmospheric conditions which is the essential contributing factor
for a change of the radiation characteristics with weather.
In order to attain a sufficiently strong input for the receiver
under these conditions, the power input for the cable has to be
rather high. However, the dimensions of the cable limit the amount
of energy that can be transmitted. Of course, the dimensions of the
cable could be increased up to a point where sufficient signal
strength is available under all conditions. However, the cable
itself becomes more expensive and heavier, i.e., cumbersome, and is
therefore, more difficult to install.
It is an object of the present invention to provide a radiating h-f
cable in which the losses are by themselves low and independent
from weather or climate. In accordance with the present invention,
it was discovered, that the conductor system should include a
particularly constructed outer conductor, serving either as shield
or as return conductor. This outer conductor is to be, on one hand,
a physically, closed tube, but of such configuration that current
can develop and propagate therein in and along a helical path only,
extending around a center line of the conductor system. In
particular, the outer conductor is constructed from electrically
serially interconnected, axially juxtaposed conductor loops
providing a closed tube as well as helical conduction path around
the center axis of the system.
An h-f cable constructed in accordance with the invention has the
advantage that the electric field cannot emanate from this
physically closed return conductor or screen. On the other hand,
the helical, coil-like contour of the current path causes
development of an inductive field external to the cable that is
useful for signal extraction and low loss pick-up by a receiver. As
the electric field component does not contribute to the radiation,
dielectric losses are eliminated, and the weather dependency of the
radiating characteristics of the h-f cable is eliminated
accordingly.
While the specification concludes with claims particularly pointing
out and distinctly claiming the subject matter which is regarded as
the invention, it is believed that the invention, the objects and
features of the invention and further objects, features and
advantages thereof will be better understood from the following
description taken in connection with the accompanying drawings in
which:
FIG. 1 illustrates a cross section through a radiating cable and
serving as transmitting antenna and signal propagation medium in
accordance with the first example of the preferred embodiment of
the present invention;
FIG. 2 illustrates a two-conductor cable in a cross section
likewise improved in accordance with the preferred embodiments of
the invention;
FIG. 3 is a side view of the cable of FIG. 1, partially broken open
for showing the several layers within the cable construction;
however, the figure is also subject to interpretation as side view
of the conductor system of FIG. 2;
FIG. 4 is a section view of a modified construction for the outer
conductor of a radiating conductor system, as another example of
the preferred embodiment of the invention;
FIG. 5 shows in plan view a sheet from which a still different
outer conductor can be constructed; and
FIG. 6 is a section of an almost completed outer conductor, as made
from the sheet of FIG. 5.
Proceeding now to the detailed description of the drawings, in
FIGS. 1 and 3 thereof is illustrated a first cable construction
having an inner conductor or core 1 which is coaxially enveloped by
a return conductor 2 of tubular configuration. There is no slot in
this tube. The two conductors 1 and 2 are separated from each other
and maintained in concentrical and coaxial position by dielectric
material 3. The center line of this conductor system is the center
axis of core 1. The tubular, outer conductor 2 is additionally
enveloped by a jacket 4 of insulating and dielectric material.
The particular construction of the outer conductor tube 2 can be
seen best from FIG. 3. In particular, it can be seen that a
completely physically closed (radially) tube has been constructed
by winding and looping wire onto the tubular dielectric layer 3.
The wire or wires 8 are wound on the dielectric tube 3 so that
neighboring loops actually engage, without leaving any axial gap of
helical contour. The wire should be insulated at least to the
extent that upon closely winding the wire in loops, there will be
little or no current flow axially from loop to loop. Through the
gapless winding of one or several wires a physically closed tube is
constructed which serves, in this case, as return conductor as well
as radiator. Jacket 4 may be extruded or otherwise deposited on
tube 2 and may serve to maintain the loops, establishing tube 2, in
position.
Turning now to FIG. 2, two conductors 5 and 6 are disposed in
parallel relation to each other along a center line 10 and embedded
in that position in a somewhat ovally contoured dielectric layer
3'. That configuration is enveloped by a tube with corresponding
cross section, 7. In this case, tube 7 serves only as shield. The
tubular configuration of shield 7 is again obtained through the
winding of wire or wires in helical configuration around the
dielectric body 3. A dielectric jacket 9 is disposed on tube 7. The
contour and construction described is analogous to the one before,
and it is readily apparent, that in such view the cable of FIG. 2
will appear as shown in FIG. 3. It was found that by using a closed
tube made from closely positioned looping wires as shield or as
return conductor, the inductive field component as between inner
and outer conductors can, in fact, be coupled out of the cable at
sufficient signal strength.
Either kind of conductor system, FIG. 1 or FIG. 2, may have its
outer conductor tube constructed differently, as will be explained
now with reference to FIG. 4. Strip or tape 11 comprised of a metal
layer or strip 12 with insulative, dielectric backing or substrate
13 is wound on the dielectric tube 3 (or 3') with the metal tape 12
facing the body 3 (or 3') and the dielectric backing facing
outwardly. The tape is wound so that adjacent loops overlap, to
make sure there is no gap in between adjacent loops, but the metal
layer in one loop engages only the insulative backing of adjacent
loop. The overlap is not essential in principle but a convenient
measure to avoid gaps between adjacent loops. The insulative
backing serves as outer insulators; however, this does not preclude
the possibility of providing an additional jacket. It should be
noted, that the avoidance of gaps between adjacent loops is not a
principle requirement of operativeness, but any gap introduces
lossiness into the cable and should be avoided for that reason.
The invention can be practiced somewhat differently but the
difference relates in principle only to the manufacturing of the
cable to obviate the need for helical winding of tape or wire. The
basic construction of core 1 with dielectric cover, 3 or 3', as the
case may be, remains the same; but the shield or return conductor
is made somewhat differently. The construction begins with a metal
strip 15 having oblique, parallel slots 16. The stripping is held
together along both edges, as the slots do not traverse the strip
completely. That tape, or strip 16, is now longitudinally bent and
wrapped around the core 3 or 3'. However, the strip is wider than
the circumference of the tube to be made, so that the strip will
abut along the lines 161 and 162. The edge portions are then bent
up, with lines 161 and 162 serving as fold lines, to form a tap as
shown in FIG. 6. The abutting edge portions are then tap-welded to
obtain a closed tube. The tape is then cut off, e.g., along the
dash-dot lines so that no straight, axially continuous conductor
path remains. As for example, portion 163 is welded to 164, a
continuous helix has been formed, so that current flows in this
conductor only along a helical path.
The invention is not limited to the embodiments described above but
all changes and modifications thereof not constituting departures
from the spirit and scope of the invention are intended to be
included.
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