US 3731314 A
This invention consists of a waveguide of substantially trapezoidal cross section, having at its smaller end a closed base portion, surrounding a conductor spaced therefrom, and exteding therefrom a gradually widening top portion open at its outer end to permit the wave propagated along the wave guide to emerge therefrom into a space adjoining said top portion.
Description (OCR text may contain errors)
Unite States Hafner 1 May 1,1973
 VEHICULAR COMMUNICATIONS SYSTEMS  Inventor: Theodore Hefner, 1501 Broadway,
New York, N.Y. 10036 22 Filed: Mai-.24, 1971 211 Appl.No.: 127,588
 US. Cl ..343/717, 343/786, 333/84 R  Int. Cl. ..H0lq 1/32  Field of Search .L ..343/71 1, 712, 713,
 References Cited UNITED STATES PATENTS 10/1970 l-lafner ..333/95 S 6/1971 Nakahara et a1. ..343/713 3,609,675 9/1971 Abele ..343/7l3 FOREIGN PATENTS OR APPLICATlONS 1,163,386 9/1969 Great Britain ..333/84 L Primary Examiner Eli Lieberman Att0rney-Theodore Hafner  ABSTRACT This invention consists of a waveguide of substantially trapezoidal cross section, having at its smaller end a closed base portion, surrounding a conductor spaced therefrom, and exteding therefrom a gradually widening top portion open at its outer end to permit the wave propagated along the wave guide to emerge therefrom into a space adjoining said top portion.
8 Claims, 6 Drawing Figures Patented May 1, 1973 FIG. 2.
INVENTOR THEODORE HAFNER VEHICULAR COMMUNICATIONS SYSTEMS One of the objects of this invention is to permit the coupling of a vehicular communications system with a stationary transmission line, with a minimum of loss and a minimum of radiation.
Another object ofthe invention is to provide a transmission line of low loss and broad bandwidth, and yet of minimum dimensions so as to be supportable in relatively restricted areas such as provided in the space between train and ground or side walls.
Still another object of the invention is to provide an efficient coupling between transmission line andvehicle, or the pickup mounted thereon, for minimum radiation, and if possible, for operation without requiring F.C.C. frequency allocations.
These and other objects of the invention will be more apparent from the drawings annexed herein, in which FIG. 1 represents in cross section a transmission line embodying certain principles of the invention;
FIG. 2 gives an example of the mounting of a transmission line, underneath the guide way of train or another type of vehicle, in a cross section perpendicular to the longitudinal extension of such guide way.
FIG. 3 illustrates a method of assembly in the field.
FIG. 4 illustrates an arrangement for measurement the electrical properties of a transmission line such as illustrated in FIG. I or FIG. 2.
FIG. 5 shows schematically another type of testing arrangement.
FIG. 6 shows the arrangement of FIG. 4 in cross sec tion.
As indicated in FIG. 1, the transmission line according to the invention, may consist of an aluminum or other type of conducting trough 1, shown in FIG. 1 in a cross section perpendicular to its longitudinal extension, comprising a square to preferably quadratic portion 2 closed at one end, open at the other end, from which extends, preferably of one piece with each other, an expanding trapezoidal portion open at its outer end, and schematically indicated at 3.
The dimensions of the transmission line are wave length depending, preferably of the order of not more than 20 percent of the operating wave length for its length dimensions, and, not more than percent for its width dimensions In the present example, the lower square portion of the cross section is of the order of 10x10 cm, while the trapezoidal portion extendion at an angle of about 30 to a length of about em; all these dimensions being provided for'an operating wave length of the order of 1.5 m. The square portion 2 of the cross section of the transmission line supports a conductor 4, preferably in a central position with respect to the sides of portion 1, and also coated with a dielectric as schematically indicated at 5. Conductor 4 may consist of copper tubing, and coating 5 of preferably pure polyethylene. The diameter of the conductor 4 is of the order of 10 percent of the crosssectional dimensions of square portion 2, while its coating 5 has a thickness of the order of 50 percent of the radius of copper conductor 4, which is of the order of l /2 inch in this specific example of the invention.
Coated conductor 4 should be as light as possible so as to permit a safe and accurate support in the center of portion 1. In the particular example of FIG. I, the coated conductor 4 is supported on styrofoam with which the square portion 2 of the cross section of the line is filled out, and which is schematically indicated at 6, and serves apart from supporting conductor 4, to define losses of the line to a minimum value.
As illustrated in FIG. 2, and for a particular application of the invention, also shown in cross section, the transmission line schematically indicated at 7, appears mounted beneath a concrete slab schematically indicated at 8, and attached to such slab by hangers (not shown) or in any other way as required by the mechanical specifications of the entire structure. In the particular example shown, the length of cross section of line 7 (ie its extension in the direction of longest dimension of the crosssection) corresponds approximately to the width of the overlaying slab 8 which will permit the field emerging from the inside of the wave guide to expand freely with a minimum of loss, and also to be picked up unimpeded by a dipole or any other pickup suitable for this purpose as schematically indicated in FIG. 2 at 9, and extending substantially in a plane sub stantially perpendicular to the plane formed by the outer opening 10' of the trapezoidal portion 10.
Slab 8 is shown supported on a steel girder 11, forming on its upper surface the guide way for the rubber wheels 12 of a vehicle (not shown) carrying on its understructure, in a manner also not shown, the pickup or coupling 9.
Exact dimensions of rails and other parts of this structure, also of any brackets for the tracks which may be required at curves, must be such as to permit safely maximum movements of the vehicle in horizontal and vertical directions, even in the case one or both of the rubber wheels should become deflated thus causing rather considerable deviations from normal movement tolerances.
The installation of the wave guide can be effected in a rather simple manner, by starting from a flat aluminum sheet, provided if necessary with longitudinal indentations corresponding to the various corners shown in the cross section of FIG. 1. In this case, during transportation, the waveguide will be carried wound up on a large reel schematically indicated in FIG. 3 at 13 from which the flat, but identured strip 14 is rolled off, over or close to the part of the track to which it is to be attached. During the rolling-off operation, strip 14 is being shaped, by being guided for example, over three shaping rollers, one arranged on top of sheet at 15, the other two underneath, at l6, 16', from which, along indentures l3, emerges 17, the trapezoidal form indicated in FIG. I in cross section.
Thereafter, the trapezoidally shaped strip 17 is attached to the guideway as for example indicated in FIG. 2. In a subsequent operation, the preformed poystyrene foam shape 18 which has been provided during manufacture with a slot 19 to permit insertion of the coated conductor is inserted into installed aluminum trough as indicated at 20, and thereafter the conductor is inserted through slot 19 which is so shaped that it does permit insertion, but also positioning of the conductor inside the foam 18.
In order further assure the rigidity of the structure, the top surface of foam shape 18 may be covered with a weather resistant coating or cover as schematically indicated at 21 which should also be designed to have as little effect as possible on the characteristic or loss of the wave emerging from the line; thus while it may contain weather resistant carbon or any other weather resisting component, it should be made as thin as possible to reduce loss to a minimum.
A preferred method and arrangement for testing: the new waveguide under laboratory conditions is apparent from FIG. 4, wherein for an operating wave length of 1.50 in, two guide sections each of 1.50 m length, are arranged at 22, 22' respectively each section between two conducting end plates schematically indicated in FIG. 4 at 23, 24, and 25, 26, respectively. In one of these sections, for example 22, the conductor is provided with a dielectric sheet, while in the other, for example 22', such dielectric sheet is omitted to evaluate the best conditions for a predetermined frequency range. Another change is to replace or remove the dielectric 6 supporting the conductor; the latter may then be supported on V-shaped loops.
Now the two structures as shown in FIG. 4 are investigated for loss and any other proerties, at a number of reasonable frequencies, such approximately 100 Mhz, 200 Mhz, 300 Mhz, and 500 Mhz.
More specifically, the resonant curves i.e., the Q of the resonator allows determination of the transmission loss under more or less ideal conditions.
In a subsequent phase of measurement, concrete blocks are approached to the guide, and the effect on the Q is being determined. This should yield a fair estimate of the actual guide when it is installed in the field.
If results indicate that the dimensions could be reduced, the measurements as above are to be repeated with a modified cross section.
In a second test series, provided the first outlined above, is considered successful, or acceptable, for the specifications to be met, in a particular field installation, a 100 in wave guide is constructed and installed in the manner schematically indicated in FIG. 5.
In this case, a number cement blocks of 4 X 8 X 16 inches schematically indicated in FIG. at 27 is arranged on a pair of 2 X 4 inch construction lumber pieces which in turn are supported on a number of stakes 30 inserted into the ground and supporting pieces 28, 29 attached in otherwise well known manner by nails or screws (not shown). The guide is now positioned on concrete slabs 27, as schematically indicated in FlG.5,at 31.
Simultaneously, guide terminations for connecting the guide to a 50 Ohm coaxial cable are established, and also various coupling methods are investigated.
In a final test series, the transmission characteristics for various positions of the guide are measured.
Finally a carriage is provided which can be moved along the guide and provided with a pickup as indicated in FIG. 6, in order to demonstrate the operation of the system.
FIG. 6 illustrates such as system, in which concrete slabs, wooden supports and stakes are again indicated at 27, 28, 29 and 30, respectively. In this modification,
dipole attached at 39, serving as pickup or coupling for the wave emerging from the waveguide which is arranged, supported on slabs 27, as schematically indicated at 40.
In this way, and as a result of the inherently simple construction of the waveguide, practical tests effectively simulating actual field conditions, can beperformed, as an additional feature of the invention.
While the invention has been shown and described, with specific mechanical and electrical parts and connections, it is not limited thereto but may be applied in any other appropriate mariner, within the skill of the expert in this field, without departing from the scope and the spirit of this disclosure.
1. In a vehicle signal system wherein a stationary transmission line is deployed adjacent the path of the vehicular travel, said transmission line comprising a substantially square waveguide open at one end and closed at the other end to define a cavity, a longitudinal conductor centrally arranged in said cavity, said conductor being coated with a dielectric coating substantially smaller than its diameter and a pair of flared sections extending at an angle from said open end of the cavity to permit the field formed in the waveguide to emerge from the flared end to the outside path of the vehicular travel.
2. System according to claim 1, wherein said angle is about 30.
3. System according to claim 1, wherein the space between said flared sections has height dimensions of the order of a fraction of operating wave length, and dimensions perpendicular thereto of the order of half of said height dimensions.
4. System according to claim 1, wherein the space between conductor and cavity is filled with a dielectric foam supporting said conductor in a central position with respect thereto, and extending to the space between said flared sections; said dielectric at said flared sections being coated with a weather resisting but wave transmissive coating.
5. System according to claim 1, wherein the height dimensions of the space between said flared sections correspond to the order of about 20 percent of operat ing wave length, and the dimensions perpendicular thereto correspond to the order of about 10 percent of operating wave length; and wherein the diameter of said longitudinal conductor corresponds to about 2 percent of operating wave length; said conductor being coated with a dielectric to a total diameter of about 3 percent of operating wave length.
6. System according to claim 1, comprising a pickup arranged outside of said waveguide near its open end, in the form of a dipole extending into a plane substantially perpendicular to the longitudinal axis of the space between said flared sections.
7. System according to claim 1, wherein the maximum width of the space between said flared sections at its open end is about twice of that at its closed end.
8. System according to claim 1, wherein the height of the space between said flared sections is larger than that of the cavity.