U.S. patent number 3,603,904 [Application Number 04/830,932] was granted by the patent office on 1971-09-07 for temperature controlled surface wave feeder lines.
Invention is credited to Theodore Hafner.
United States Patent |
3,603,904 |
Hafner |
September 7, 1971 |
TEMPERATURE CONTROLLED SURFACE WAVE FEEDER LINES
Abstract
The invention consists of a surface wave antenna feeder in the
form of a conductive tubing coated with a dielectric to produce on
the outside of the coated conductor a field carrying substantially
the entire electromagnetic wave energy from the transmitter to the
antenna, and providing inside the tubing a circulating fluid so
controlled as to maintain the line at a constant temperature
substantially to exclude longitudinal expansion, regardless of the
power level of the surface wave and the temperatures surrounding
the line.
Inventors: |
Hafner; Theodore (New York,
NY) |
Family
ID: |
25257950 |
Appl.
No.: |
04/830,932 |
Filed: |
June 4, 1969 |
Current U.S.
Class: |
333/240; 343/850;
174/15.6 |
Current CPC
Class: |
H01P
3/10 (20130101) |
Current International
Class: |
H01P
3/10 (20060101); H01P 3/00 (20060101); H01p
003/08 (); H01p 001/30 (); H01b 007/34 () |
Field of
Search: |
;333/95S,95
;343/785,704,704.5 ;174/15C,47,83 ;138/155 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,115,097 |
|
Apr 1956 |
|
FR |
|
717,128 |
|
Oct 1954 |
|
GB |
|
Other References
Kimbark, E. W., "Electrical Transmission of Power & Signals,"
John Wiley & Sons, 1949 pp. 58-60.
|
Primary Examiner: Saalbach; Herman Karl
Assistant Examiner: Punter; Wm. H.
Claims
I claim:
1. In a long-distance high-power antenna feeder system, a
continuous tubing which at least at its outer surface is
conducting, a dielectric coating surrounding said conducting
surface and adapted to maintain a surface wave of predetermined
radius in the space surrounding said coating, and means including a
circulating fluid connected to the inside of said tubing, and
temperature control means adapted to maintain said fluid at such a
constant temperature as to substantially exclude longitudinal
expansions, in a manner substantially independent of the power
level of the surface wave and the temperature surrounding said
tubing.
2. System according to claim 1, comprising a tower, an antenna
attached to its top and a transmitter arranged near its base;
wherein said tubing at least partially connects said transmitter
and said antenna, and comprises a series of tubes attached to each
other at their ends through an intermediate tubing adapted to
connect adjacent tubes by means of threads permitting assembly of
the line at the antenna site; each of said tubes having a
conducting insert extending from said tube and having a thread
permitting connection to the thread of said intermediate
tubing.
3. System according to claim 2, wherein said tubes consist of
copper plated stainless steel.
4. System according to claim 1, wherein said dielectric coating
consists of polyethylene having a dielectric loss figure of the
order of 0.0005 in the UHF range.
5. System according to claim 1, wherein said dielectric coating
consists of Teflon (trademarked by Dupont) having a dielectric loss
figure of the order of 0.0002 in the UHF range.
6. System according to claim 1, wherein said dielectric coating
consists of heat-shrunk material.
7. System according to claim 1, comprising surface wave launcher
means including a transducer and a horn flexibly connected to said
transducer and supported at least on part of said tubing, and a
transmitter rigidly connected to said transducer; said transducer
including a coaxial line having an inner conductor extending
therefrom and flexibly connected to said tubing so as to permit
lateral movements of said tubing only, while maintaining said
tubing a substantially constant length.
Description
The invention consists of an antenna feeder line in the form of a
conductive tubing coated with a dielectric and forming a surface
wave transmission line, with means being applied to the tubing
either in the form of a coolant fluid or in the form of electric
current so as to control the temperature of the line to make it
substantially independent from atmospheric conditions while
carrying high R.F. power, especially in the VHF and UHF frequency
ranges.
One of the objects of the invention is to dispense with large
coaxial cables and waveguides as antenna feeder lines to carry the
high power required for present day VHF and UHF television
transmitters. Such cables and waveguides are not only expensive in
manufacture but they also involve very high cost of installation
and maintenance. At the same time of course, power must be carried
over the feeder line with a very low loss and an equally low VSWR;
for example, at 50 kw. and 800 MHz., a 500 ft. feeder line is
expected to have a total loss of the order 0.7 db. and VSWR over a
bandwidth of 10 MHz. of only 1.05.
In accordance with one aspect of the invention, an antenna feeder
line in the form of a conductive tubing consisting for example of
copper or copperplate stainless steel, and coated with a dielectric
of low loss for example a loss figure of 0.0005 at UHF and forming
a surface wave transmission line, and capable of being arranged at
a slant depending from the antenna tower, is provided with a
coolant system in which a fluid is passed through the tubing
maintaining its temperature constant and thereby reducing
atmospheric influences to a minimum. At the same time while
providing loss and VSWR values equivalent to those of coaxial
cable, for example of the rigid 61/8-inch type, or of corresponding
waveguides, cost of manufacture and especially cost of installation
of the feeder line are reduced to a fraction of those prevailing in
the past.
In a modification of the invention, instead of a fluid, electrical
heating is applied to the tubing, to prevent icing, under control
of temperature difference prevailing between the temperature due to
the power carried by the line, or the absence of such power, and
the temperature caused by the weather.
These and other features of the invention will be more fully
apparent from the drawings annexed herein to which:
FIG. 1 illustrates schematically an antenna feeder line in
accordance with the invention supported on an antenna tower; FIG. 2
a modification thereof.
FIG. 3 shows an example of a tubular feeder line, in part only and
in a cross-sectional side view; FIG. 4 a modification thereof.
FIG. 5 shows an example of the launcher arrangement for the feeder
line, embodying certain principles of the invention, and
FIGS. 6 and 7 show parts of FIG. 5, for a UHF transmitter, in
greater detail, also embodying certain aspects of the
invention.
As apparent from FIG. 1, a tubular surface wave transmission line
as will be described in greater detail further below, and
schematically indicated by line 1, is shown suspended from a tower
part of which is indicated at 2, and which is 500 ft. high. Line 1
extends at a slant to a transmitter station 3 disposed about 100
ft. away from the foot of tower 2. Preferably the slant is so
disposed as to permit line 1 depending from tower 2 with minimum
tension, say of the order of 2000 lbs. for a 50 kw. 800 MHz. TV
transmitter feeder line. Such a slant does not only reduce strain
on the tower to a minimum but it also permits to reduce to a
minimum any interference between the structure of tower 2 and the
field radius of surface wave transmission line 1, which is
generally of the order of about 1 wavelength of the operative
frequency range of the system.
Tubular line 1 is connected in a manner, at least in principle
known per se, and as will be explained more specifically further
below, to its terminal equipment, at one end over a receiver horn 4
to an antenna schematically shown at 5; at its other end, line 1 is
rigidly connected over a similar launcher horn 6 and a coaxial
cable 7 to the transmitter station 3. Tubular transmission line 1
after having passed through the launcher 6, is anchored to ground
and also electrically grounded as indicated at 8, as need not to be
explained in detail, and as may be considered well known per se for
example, from U.S. Pat. Specification No. 3,440,576.
At ground platform 8, another tube 9 is connected which leads a
coolant fluid derived from a pump system schematically indicated at
10 but otherwise well known per se, into, and up to the tubular
transmission line 1, on the top of which it is passed in a manner
similar to that described above, through receiver horn 4 a tube
portion 11 to a pipe 12 attached to tower 2 for recirculation, and
if necessary after recooling or reheating as the case may be, in
accordance with the temperature requirements of the system, or any
other conditions of control.
In the specific embodiment of the invention shown in FIG. 1,
recirculation pipe 12, is connected to another pump system
schematically indicated at 13 and which is adapted to act as a
heating system while pump system 10 is adapted to act as a cooling
system. Each of systems 10 and 13 is controlled by the average
temperature along tubular line 1 as indicated in FIG. 1 by control
lines 14, 15 connected respectively to thermoelements (not shown)
attached to the end portions 8, 11 of line 1, respectively which
represent ground and top platform planes, respectively. Under
control of these temperatures, or an average thereof, the
corresponding signal voltages, after amplification if necessary,
well known in the art of telecontrol and telemetering, may be used
to operate, depending on the temperatures involved, either pump
system 10 which cools the fluid passing therethrough, or pump
system which heats the fluid passing therethrough. In this way,
tubular line 1 may be maintained, regardless of its mode of
operation or atmospheric or weather conditions, on a substantially
constant temperature, which may be relatively low or so determined
as to produce optimum transmission conditions and a minimum of
mechanical stress such as extensions of length due to varying
temperature arising out of changes in the transmitted power,
atmospheric variations or other varying conditions.
Since fluid coolant or heating systems are well known per se, there
is no need to describe such systems in greater detail; any type of
such system may be applied therefore, without departing from the
scope of this disclosure.
In this particular application, the intention has the advantage
that it will not be necessary in the mechanical support of tubular
line 1, to provide means to compensate or tolerate longitudinal
changes of line 1. All that will be necessary, is to provide the
angular or rotary movement of the line under wind pressure, as will
be explained further below in connection with the attachment or
guidance of the tubular line through the launching horn.
In the modification shown in FIG. 2, tubular line 1--which is
otherwise suspended in a manner similar to that shown in FIG. 1
except certain changes as conditioned by this modification--at an
outer lower portion 16 is electrically connected over line 17 to an
AC or DC power source schematically indicated at 18, and over line
17' to an upper cable portion (not shown). Temperature sensor lines
schematically indicated in FIG. 2 at 19, 19', after comparing
temperatures prevailing on line 1, or averaged from its ends, with
atmospheric temperatures, control power source 18 which applies low
frequency or DC current to tubular line 1, thereby increasing its
temperature to an amount preventing the formation of ice or
providing other conditions maintaining maximum efficiency.
Since such heating systems and their control under varying
temperatures, are well known per se, they will not be described in
detail, and they may be applied in any form or manner whatsoever
without limiting the scope of this invention.
FIG. 3 shows a portion of the tubular line, and more specifically a
joint where a number of tubes forming such a line, are attached to
each other.
In accordance with this invention, it has been found practical to
provide a line consisting of a cascade of tubes which can be
connected during the installation of the line, but otherwise may be
constructed of tubes of such length that can be easily handled
during transportation, coating and further assembly.
In a particular realization, a 500 ft. tubular line has been
constructed of 25 tubes of 20 ft. length each, consisting of hard
drawn copper which after having been coated with an appropriate
dielectric such as polyethylene or Teflon (reg. TM), the latter
having a loss figure of 0.0002; are attached to each other in the
field and prior to the mounting on the antenna tower. While
polyethylene is used as coating, generally, where relatively low
operating temperatures are permissible, as for example provided for
in the fluid system application illustrated in FIG. 1, the
application of an electric heating system such as provided in FIG.
2 would require relatively high temperature resistant material as a
coating such as Teflon.
It has further been found practical, to apply the dielectric
coating not by extrusion but by means of heat shrinking of tubular
material on the tubes. The tubular material may then consist either
of homogenous plastic material such as polyethylene or Teflon of
appropriate dielectric constant and low-loss properties as required
for surface wave maintenance.
Alternatively, the heat shrinkable tubing may have a sandwich type
of structure, and especially in the case of polyethylene, consist
of a bottom layer of relatively low-loss but weather-sensitive
plastic material, and a top layer of relatively high-loss but
weather insensitive plastic material, whereby the top layer is
relatively thin compared to the bottom layer so as to reduce losses
to a minimum while maintaining a high degree of weather
resistivity.
The invention, however, is not limited to any particular dielectric
material or coating structure, nor to a particular way of its
production or application.
Nor is the invention limited to any particular way controlling or
affecting the temperature of the tubular line or its dielectrical
coating. In effect, if necessary such systems can be combined, as
for example the fluid system such as exemplified in FIG. 2, with an
electrical heating system such as indicated in FIG. 1, without
departing from the scope of this disclosure.
Furthermore, since the fluid systems shown in FIG. 1, make the line
virtually independent from the power transmitted therethrough, or
the heat produced by such power--which is the case of the
above-mentioned example of a 500 ft. 50 kw., 800 MHz. tubular
surface wave transmission line, may amount to 5 kw.--the same line
could be used to transmit much higher powers as for example in the
above-mentioned case, a power of the order of 100 kw.--thereby
reducing cost of the design for different power lines to a
minimum.
In FIG. 3 a portion of tubular transmission line is shown in
cross-sectional view, and more particularly a portion showing a
joint between two adjacent tubes forming sections of the line and
attached to each other during the installation of the line.
In FIG. 3 the end portions of two line sections consisting for
example of copper tubes of 20 ft. length, are schematically
indicated at 20, 21, respectively, each coated with a dielectric
layer in the manner as previously indicated, and schematically
shown at 22, 23, respectively. Each of copper tubes 20, 21 at each
of its ends, is provided with an insert 24, 25 which may also be of
copper or of stainless steel or any other suitable material.
Inserts 24, 25 are provided with outer threads to permit attachment
of tubes 20, 21 to each other with the aid of intermediate piece 26
which through an inner thread schematically indicated at 26',
assures electrical and surface contact between tubes 20, 21 and,
being also coated with a dielectric coating of the type shown at
22, 23, and indicated for piece 26 at 27, will assure the required
continuity for maintaining a surface wave along the tubular
line.
Inserts 24, 25, are attached to the ends of tubes 20, 21 by means
of a number of setscrews schematically indicated in FIG. 3 at 28
which may also serve, if necessary, to fix the threads of
intermediate pieces 26 in their position.
However, inserts 24, 25 may be attached to tubes 20, 21 in any
desired manner for example by brazing or welding. Alternatively,
also without departing from the scope of this disclosure, the
inserts of the type shown at 24, 25 may be omitted and threads or
other attachment elements directly be provided inside and outside,
respectively of the adjacent ends of tubes 20, 21 in the forms of
threads or the like so as to permit assembly in the field to the
desired length of transmission line.
If required, further, more intermediate pieces of the type shown at
26 may also be omitted and the ends of tubes 20, 21 directly
attached to each other by welding or screwing or in any other way,
also without departing from the scope of this disclosure.
FIG. 3 also shows the attachment of the tubular line, or at least a
predetermined portion thereof, to a fluid line to control the
maintaining of temperature along the line, in accordance with one
of the aspects of the invention, as schematically at 29.
In the modification shown in FIG. 4, designated for applying
electrical heating current to an end portion of tubular line 1,
such an end portion as indicated in FIG. 4 at 30 is shown connected
over a conductor 31 to a temperature controlled source of electric
power, not shown but otherwise well known in the art. In this case,
of course, the recirculation pipe shown in FIG. 1 at 12 may be
omitted and replaced by a return cable for the electric heating
current, or the tower 2 itself used as an electric return
medium.
FIG. 5 illustrates a surface wave launcher especially designed to
cooperate with a tubular line in accordance with the invention. The
launcher consists of a transducer schematically indicated at 32
including a coaxial line the inner conductor of which is also of
tubular shape and dimensions similar to those of tubular line 1, as
schematically indicated at 33, and also in FIG. 6 in greater
detail.
In accordance with one embodiment of the invention, especially
where by the maintaining of constant temperature of operation,
which excludes longitudinal variations of the line, the connection
between conductor 33 and line 1 is made so as to permit angular
deviations, without impairing electrical contact, fluid
transmission and wave propagation. This is achieved by replacing at
the exit of transducer 32, the tubular structure of relative rigid
configuration by a flexible phosphore bronze sleeve schematically
indicated in FIG. 6 at 34 and attached to inner conductor 33 and
line 1, respectively, by screws, rivets or welds. Sleeve 34 can be
made flexible by being shaped in the form of a bellow, in the form
of phosphore bronze fingers similar to the flexible fingers 36
shown in the flexible attachment between transducer 32 and horn 35
described further below.
Transducer 32 is connected to a horn which serves in otherwise
well-known manner, to transform the coaxial wave emerging from
transducer 32 into a surface wave, as indicated in FIG. 5 at 35.
Horn 35 is also attached flexibly to transducer 32 by means of a
number of phosphore bronze fingers 36, arranged peripherally around
the ends of horn 35, as shown in greater detail in FIG. 7, where
the figures 36 are shown attached to the ends of horn 35 and
transducer 32, respectively, in such a way as to permit the horn 35
to be supported on the tubular line 1 only--or its extension inside
horn 35--supported thereon if necessary by a dielectric cover disc
schematically indicated in FIG. 5 at 37. In this way, horn 35 is
permitted to follow the deviations of tubular line 1 without
transferring any strain to transducer 32, and any equipment
connected thereto such as the heavy rigid and mechanically
sensitive coaxial cable connected to the output flange 37 of
transducer 32.
* * * * *