Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3423681 A
Publication typeGrant
Publication dateJan 21, 1969
Filing dateMar 25, 1966
Priority dateMar 25, 1966
Publication numberUS 3423681 A, US 3423681A, US-A-3423681, US3423681 A, US3423681A
InventorsMckenna John R
Original AssigneeDavid A Rawley Jr, Donald E Bilger
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Highway radio communications system
US 3423681 A
Images(3)
Previous page
Next page
Description  (OCR text may contain errors)

Sheet INVENTOR JOHN R McKENNA A'IT RNE'Y Jan. 21, 1969 Filed March 25, 1966 HIGHWAY RADIO COMMUNICATIONS SYSTEM Filed March 25, 1966 Sheet 3 of 5 INVENTOR JOHN R. McKENNA BY 6 I :7; 5 g

Y A'ITO Jan. 21, 1969 Filed March 25, 1966 J. R. MCKENNA HIGHWAY RADIO COMMUNICATIONS SYSTEM Sheet 3 JOHN R. McKENNA ATTORNEY United States Patent 9 Claims ABSTRACT OF THE DISCLOSURE A highway ratio communications system for transmitting a radio signal to vehicles traveling along a roadway having a radiation antenna means or a pair of radiating antennas each in the form of a transmission line running parallel to and on opposite sides of the roadway, and being driven in appropriate phase relation by a radio signal from a common transmitter, with each antenna having a radio signal shield on the side away from the highway wherein each shield includes an electrically grounded portion defining a vertical plane extending from at least the plane of the roadway to a predetermined distance above the respective radiating antenna and acts to attenuate the rearward field of the adjacent respective radiating antenna as well as the forward field of the radiating antenna on the opposite side of the roadway.

This invention relates to radio communications apparatus and more particularly to a highway radio communications system for transmitting radio signals to vehicles traveling along a roadway.

Many systems are known to those skilled in the art for transmitting messages to vehicles moving along a highway for alerting the driver as to various road con ditions, weather, traffic and the like. Most, if not all, of these systems are adapted to make use of the standard broadcast radio receiver normally carried by the vehicles. Further various types of transmission apparatus are known for radiating these messages to the vehicles. Some systems employ an embedded transmission line in the roadway which extends along its length. Other systems utilize telephone and power transmission lines running along the roadway. Still other systems utilize various other types of antenna means such as simple loop antennas selectively positioned along the highway route.

All of these known systems, however, suffer from an inherent limitation insofar as actual use is concerned due to the fact that such systems either transmit too little power or fail to meet the requirements spelled out in the Rules and Regulations of the Federal Communications Commission (F.C.C.). The Rules and Regulations of the F.C.C., as presently written, make no provision for a highway radio service. Consequently, this operation must be in accordance with Part of the Commissioners Rules which concerns unlicensed radiation. The regulations of Part 15 place stringent limitations on the amount of permissible radiation. The maximum amount of radiated energy is expressed by formulae in which the reference distance is 100 feet. While radiation is permitted throughout the spectrum, the region of present interest is the standard broadcast band where the maximum signal strength, at the aforesaid 100 foot distance, is equal to 24,000 (microvolts per meter)/frequency (in kilocycles per second). The permissible level of radiation in the standard broadcast band varies over approximately a 3 to 1 range depending upon the emission frequency. It can be seen that for maximum signal strength, the operating frequency should be as low as possible; however, the present standard broadcast band prohibits frequency allocations lower than 535 kilocycles. Assuming Patented Jan. 21, 1969 operation around 635 kilocycles, the permissible radiation at one hundred feet away from the radiator is 24,000/635=37.8 microvolts per meter. This radiation level increases linearly as the distance decreases, doubling as the spacing is reduced to fifty feet and increasing ten-fold when the interval is reduced to ten feet.

The sensitivity of the poorest quality auto radio receivers and the normal varying ambient noise levels along the route determines the lowest values of signal which will provide acceptable listenable service. It is obviously desirable to provide signal strength in excess of the minimum acceptable level to assure high quality, noisefree reception. To do so will require an unconventional radiation system for a dual lane road bed in which the energy level across each dual lane strip is maximized while the signal on either side of the right of way is suitably attenuated.

It is an object of the present invention, therefore, to provide an improved radio communications system for transmitting messages to vehicles moving along a highway.

It is another object of the present invention to provide a high quality, noisefree highway or turnpike communi cations system for vehicles in which the transmitted signals are confined to the vicinity of the roadway.

It is yet another object of the present invention to provide a restricted radio transmitting system for communicating to vehicles traveling along the roadway in a predetermined direction while attenuating the signal strength to the required level outside of the immediate vicinity of the roadway.

It is still another object of the present invention to provide a highway radio communications system which satisfies the requirements of the Federal Communications Commission.

These and further objects of the invention are accomplished by the use of a pair of radiating antennas, each being in the form of a transmission line running parallel to the roadway on opposite sides thereof, and being driven in appropriate phase relation by a radio signal from a common transmitter, with each antenna having its own shield on the side away from the highway wherein each shield acts to attenuate the rearward field of the adjacent radiating antenna as well as the forward field of the radiating antenna on the opposite side of the highway.

Other objects and advantages of the present invention will be more readily understood when the following detailed description is read in connection with the accompanying drawings, in which:

FIGURE 1 is a plan view of sections of a pair of oppositely conducting dual lane roadways with a median strip including the embodiment of the subject invention;

FIGURE 2 is an enlarged front sectional view of one of the dual lanes of a divided roadway including the subject invention;

FIGURE 3 is an enlarged perspective view of a portion of one of the single wire transmission lines and its adjacent associated radiation shield;

FIGURE 4 is an enlarged vertical sectional view of a portion of the supporting structure upon which each radiating transmission line is mounted;

FIGURE 5 is an enlarged fragmentary side elevational view of an illustrative example of the manner in which the shield wires as shown in FIGURE 3 are attached to the supporting structure;

FIGURE 6 is a perspective view similar to FIGURE 3, but on a reduced scale, showing a modified form of supporting structure for the system of the invention;

FIGURE 7 is an enlarged side elevational -view, part ly in section, of fragmentary portions of the support of FIGURE 6; and

FIGURE 8 is a cross-sectional view, on a reduced scale, similar to FIGURE 2, showing a modified arrangement of the system of the invention on a divided roadway.

Referring now to the drawings, FIGURE 1 illustrates the system embodying the subject invention. A pair of dual lane roadways 10 and 12 is shown comprising a two direction turnpike such that roadway 10 carries vehicle 14 in one direction while the roadway 12 carries the vehicles 15, 16 and 17 in the opposite direction. A median strip 26 is adapted to separate the two roadways. The radio communications system hereinafter disclosed affords communications to vehicles traveling in a predetermined direction, that is, one message can be directed to vehicles traveling in one direction on the highway or turnpike while another message can be simultaneously transmitted to vehicles traveling in the opposite direction. Furthermore, the electromagnetic radiation is substantially confined to the area of the particular roadway to be radiated. It also provides for means whereby a particular message can be transmitted to vehicles along a selected distance such that while a vehicle is traveling along a certain stretch of roadway, one message will be communicated thereto; however, when passing on to another stretch of roadway, a second message individual to that section of roadway can be transmitted thereto. It should be understood, however, that when desired one message can be transmitted to two or more sections ofthe roadway or for the entire length, depending upon the nature of the message desired to be transmitted.

In order that different messages can be transmitted to vehicles passing in opposite directions, each roadway 10 and 12 contains its own communications system. Each roadway, for example roadway 10, includes a transmitter 22 operating in the broadcast band having an input terminal 24, coupled to a two wire transmission line comprising antenna wires 26 and 27 running substantially parallel to the dual lane roadway 10 for a predetermined distance Where a second independently operating transmitter 22' is located. The transmitters 22 and 22' commonly feed the antenna wires 26, 27 and 26' and 27, respectively, such that the current in its pair of antenna wires is in appropriate phase relation with each other, for example, such as substantially out of phase. Terminations, not shown, are coupled to the antenna wires at their extremities.

It is contemplated that the radiating transmission lines comprising the wires 26 and 27 would run along the roadway 10 for approximately ten to twenty miles or other selected distance. It is desirable for radiating antennas of such a length that one or more signal amplifiers 28 be coupled to each line intermediate the ends thereof. It is also desirable to include signal amplifiers of the type shown for impedance matching purposes where the antenna wires 26 and 27 would have to be fed through underground conduits where access roads lead onto the roadway. In addition, relatively short breaks in the antenna and shield system, to be described, are provided at regular intervals along the length of the system to enable maintenance equipment such as grass-cutting apparatus to have easy access to both sides of the radiation shields 30 and 32.

A first radiation shield 30 is located behind the roadway 10 and the antenna wire 26 such that it runs parallel thereto and substantially coextensive with the antenna wire 26. A second radiation shield 32 is located behind the other side of the roadway 10 and the radiation wire 27 such that it also runs parallel to and coextensive therewith. The purpose of the radiation shields 30 and 32 is to attenuate the rearward field of the adjacent radiating antenna 26 and 27, respectively, while at the same time attenuating the forward field of the radiating antenna on the opposite side of the roadway, that is, wires 27 and 26.

The transmitters 22 and 22' are coupled to a source of input signals, not shown, by means of the input terminals 24 and 24, respectively. The input signal source may be,

for example, a telephone line containing programmed material in the form of a message to be communicated to a vehicle traveling along the particular stretch of roadway; however, when desirable, the same input signal could be applied to both input terminals 24 and 24'. It should be pointed out that this is stated by way of example only and is not meant to be interpreted in a limiting sense.

The system thus far has been described with respect to a radio communications system for the roadway 10. With respect to the roadway 12 which carries vehicles in the opposite direction, the apparatus is merely duplicated with transmitters 22 and 22 coupling signals to the antenna wires 26 and 27 which run adjacent to and parallel to the roadway 12 with the radiation shields 30 and 32 situated behind wires 26 and 27 for confining the radiation to the vicinity of the roadway 12 while attenuating this signal rearwardly of the antenna wire 26 and wire 27. However, it is to be understood that the system can also be used on a two lane undivided roadway.

Referring now to FIGURE 2, there is shown a cross sectional view of a typical 20 foot dual lane roadway in one direction including the two antenna wires 26 and 27 and a pair of radiation shields utilized therewith. Shown in cross-sectional view is a two lane roadway, for example roadway ltl, having two vehicles 36 and 38 traveling sideby-side in the same direction along the roadway. The transmitting antenna wires 26 and 27 are shown mounted on electrically conductive supporting structures 40, constructed of metal or the like, comprising the vertical member 42- and two horizontal members 44 and 46. The antenna wires 26 and 27 are attached to but insulated from the horizontal members 44 by means of insulating members 48. The antenna-shield configuration is located on r each side of the roadway 10 such that it is spaced from the respective edges thereof in conformity to terrain and radiation requirements. Both antenna wires 26 and 27 are located substantially the same height above the road level as well as back from the respective edge of the roadway, preferably an equal distance. For example, if each lane of the dual lane roadway 10 is ten feet wide, the antenna wires 26 and 27 are located approximately ten feet from the respective edge where the terrain is relatively flat. However, in certain situations, where terrain or structures such as bridges, un-derp asses, ovenpasses, and the like, do not permit relatively wide and fiat shoulders adjacent the roadway the antenna-shield configuration may be placed substantially closer to the edge and in a somewhat modified configuration for the relatively short distance required, to satisfy the particular problem presented by roadway construction and route.

The radiation shields 30 and 32 shown in FIGURE 1 each comprise a plurality of wires 30a30g and 32a-32g. The vertical member 42 of the support 40, shown in FIGS. 25, is constructed of galvanized pipe or other electrically conductive material, as well as the horizontal members 44 and 46, The shield wires 30a-30g and 32a- 32g are adapted to provide an electrical shield on three sides of the antenna wires 26 and 27. The uppermost shield wires 30b and 32b are raised off the ground toa height preferably of about 10 feet high so that they extend above the tops of the vehicles 36 and 38. The wires 26 and 27 then are mounted approximately five feet above the surface of the ground. The shield wires 30a and 32a are offset from the vertical member 42 while the shield wires 30g and 32g are embedded in the ground. The shield wires 30b30f run substantially parallel to one another through the vertical member 42 and define a substantially vertical plane with respect to the ground. The same may be said with respect to the shield wires 32b-32f. Ground wires 30a and 301) are substantially parallel to one another and define a substantially horizontal plane with respect to the surface of the ground. Also shield wire 30a, antenna wire 26 and shield wire 30g define a second substantially vertical plane with respect to the earth. Considering the shield wire 32a, the antenna wire 27 and the shield wire 32g, they also define a second vertical plane with respect to the vertical plane defined by shield wires 32b-32 Considering now FIGURE 3, there is shown in perspective view one supporting structure 40 for the antenna wire 26 and the shield wires Silo-30b. The vertical member 42 which is an electrical conductor is embedded in a concrete base 50 for support and is further electrically connected to a grounding rod 52 by means of an electrical conductor 54 soldered to the member. The horizontal members 44 and 46 are mechanically and electrically coupled thereto such that the member 44 is located midway while member 46 is located near the upperextremity thereof. The antenna wire 26 is shown mounted to the horizontal member 44 but is insulated therefrom by means of an insulating member 48 which is preferably a piece of fiberglass rod or the like. The shield wires 30a30f are adapted to pass through the members 42 and 46 by means of holes drilled therethrough. These wires are electrically grounded to the members 42 and 46 in a manner to be described in greater detail subsequently.

As has been noted above, the shield wires 30a-30g and 32a32g run substantially parallel with each other and parallel to the respective antenna wires 26 and 27 and coextensively therewith. In certain instances, the shield wires 30g and 32g embedded in the earth can be eliminated, such as for example when the antenna-shield configuration passes over salt water in which case the salt water acts as a shield.

It has been found that a desirable number of shield wires appearing in the vertical plane above the roadway level as defined by shield wires 30b30f and 32b32f should be no less than five for a proper attenuation of the rearward radiation field of the antenna wires 26 and 27 when operating in the standard broadcast band but it is to be understood that a greater number of shield wires may be provided. Also, it has been found that a desired distance between supporting structures 40 should be roughly eighty feet. With an antenna-shield configuration as shown in FIGURES 2 and 3, the system provides a ratio of the desired signal strength at the center of the dual lane to undesired signal at a distance of one hundred feet from the closer radiating wire of approximately 18:1 which means for 37.8 microvolts per meter undesired signal level at one hundred feet a 680 microvolts per meter signal strength appears at the center of the roadway.

FIGURE 4 discloses in greater detail the mechanical features of the vertical member 42 and the horizontal member 44. The vertical member 42 is shown in a sectional view with the horizontal member 44 coupled thereto by means of a threaded coupling into a sleeve 56 which is welded to the member 42. Reference character 58 indicates a weld. A small hole 60 appears in the side of the pipe so that a shield wire, such as 30d or 32d, can pass therethrough. The glass fiber rod 48 fits into the member 44 and is fastened thereto by means of nut-bolt combination 62. A hole 64 appearing near the extremity of the fiberglass rod 48 is adapted to pass and support an antenna wire such as antenna wires 26 or 27 therethrough.

Referring now to FIGURE 5, there is shown the manner in which the shield wires 30b-3Gf and 3217-32 are mechanically and electrically coupled to the vertical supporting structures 40. A shield wire, for example shield wire 30b, is continuous and passes through the vertical member 42 by means of the holes 60. A tension relieving wire 66 is wrapped tightly about the shield wire 30b immediately adjacent the holes 60 and a solder connection 68 is made at each wrap to the member 42 which, as has been said before, is preferably composed of galvanized pipe. A third solder connection 69 is made between the tension relieving wire 66 and the member 42 intermediate the solder joints 68.

\Vhat has been shown and described therefore is a turnpike radio communications system for vehicles traveling in a predetermined direction along a turnpike. The system comprises in combination with each roadway one or more transmitters commonly coupled to a two wire antenna system with one wire each running on opposite sides of the roadway for a predetermined distance. Secondly, and most importantly, each line of said transmission line comprises a radiating antenna wire running substantially parallel to and adjacent the roadway with each antenna line being substantially shielded on three sides by a plurality of shield wires running substantially parallel to and coextensive with the transmission line. Both transmission lines are commonly driven by the transmitter such that the signals traveling on the transmission lines are in ap-.

propriate phase relation, the resulting effect being that the radiation shields attenuate both the rearward field of the adjacent radiating antenna as well as the forward field of the radiating antenna on the opposite side of the roadway.

This invention has been shown and described in connection with the most favorable terrain adjacent the edge of the roadway. However, in instances such as in built-up highways, where a roadway shoulder is only a few feet wide, not sufiicient for a vehicle to pull ofi the roadway, with the terrain then falling off on a steep decline, the vertical members 42 of the supports 40 would be substantially longer since they would be anchored in the ground a substantial distance below the level of the roadway and would still extend the same distance above the roadway surface as shown. In such an instance, additional shield wires comparable to wires 30a30g and 32a-32g would be connected on the supports to form a radiation shield adjacent the roadway extending the vertical dimension of the supports. This means the supports would also provide shield wires at levels below the level of the highway, that is between the highway level and the plane at which the support contacts the ground. The supports would still provide, for example, at least five shield wires above the roadway level.

Other variations in the supporting struture, not shown, may become necessary to form a continuous radiation shield adjacent the roadway in other peculiar terrain, bridges, etc., situations, but the concept of the invention remains the same in all instances.

A modified form of support 40 constructed of electrical insulation material, such as fiber glass, is shown in FIGURES 6-8, with FIGURE 8 also disclosing a modified support 70 for use in the center strip or median of a divided highway where the median is not wide enough to accommodate a pair of radiation shields as shown in FIGURE 1. The supporting structure 40 is similar to the supporting structure 40 and the members connected thereto, as previously described, and similar components are designated by corresponding primed numerals in the drawings. In this form of the invention, vertical member 42' is constructed of insulation material, such as plastic or fiber glass tubing, and is appropriately apertured to receive horizontal rod members 44 and 46' therethrough which are secured thereto by appropriate means, such as epoxy resin, as indicated at 71. Rod members 44' and 46' are also constructed of electrical insulation material, such as fiber glass, and are apertured adjacent the ends to pass and support antenna wires 26" or 27", and shield wire 30a or 32a, respectively. In like manner, vertical member 42 is provided with a plurality of apertures along its length through which shield wires 30b- 30f or 32b'32f pass. The wires 30a-30f or 32a'-32f', forming the radiation shield, are electrically grounded by means of an electrical conductor 54' electrically connected to grounding rod 52 and each of the shield wires at 72, by soldering, clip connectors, or the like. Where necessary, conductor 54 may be secured in position by means of tape 73, or other suitable means. The top of vertical member 42' is provided with a cap 74 connected thereto by suitable means, such as epoxy, to close the end of the tube.

Where circumstances permit, as where the median of a divided highway is relatively small as previously indicated, a single supporting structure 70 may be used for supporting a pair of antenna wires 27" and a pair of upper shield wires 32a as indicated in FIGURE 8. In this arrangement the vertically arranged shield wires 32b'32f serve as the vertical shield wires for the communication systems, of both roadways 10 and 12, but electrically the system remains the same as when a pair of complete radiation shields are provided in the media. The upper and lower horizontal rods are the same as rods 46' and 44 but extend substantially the same distance from opposite sides of the vertical member 42 and respectively support shield wires 32a and antenna wires 27" at each end thereof. The wires are connected into the system as before, except in this instance a pair of shield wires 32a and shield wires 32b'32f are connected to ground by a conductor 54' at each of the support members.

While there has been shown and described what is at present considered to be preferred embodiments of the subject invention, modifications thereto will readily occur to those skilled in the art. It is not desired therefore that the invention be limited to the specific arrangements shown and described but it is to be understood that all equivalents, alterations and modifications within the spirit and scope of the present invention are herein meant to be included.

I claim as my invention:

1. A highway radio communications system for transmitting a radio signal to one or more vehicles traveling along a roadway comprising in combination: a radio communications transmitter having an input signal coupled thereto from a signal source; radiation antenna means, coupled to said radio communications transmitter for radiating a radio signal to said vehicles, and extending a predetermined distance along said roadway and being located substantially parallel to and adjacent thereof; and a pair of radio signal shield means, one on each side of and substantially parallel with said roadway, substantially coextensive and parallel with said radiation antenna means; said radiation antenna means located 'between at least one side of said roadway and one of said radio signal shield means; and each radio signal shield means including an electrically grounded portion extending vertically from at least the plane of said roadway to a predetermined distance above said radiation antenna means for attenuating said radio signal to a predetermined level in directions laterally away from said roadway thereby confining said radio signal to the immediate vicinity of said roadway.

2. A radio communications system as defined in claim 1, wherein said radiation antenna means comprises at least a one wire transmission line located a predetermined height above the surface of the roadway.

3. A radio communications system as defined in claim 1, wherein said radiation antenna means comprises two radiating antenna wires coextensive with each other, commonly fed from said radio communications transmitter so to carry substantially out of phase signal currents and disposed relative to said roadway such that one wire is situated on each side thereof between the roadway and the radio signal shield means.

4. A radio communications system as defined in claim 1, wherein said radiation antenna means comprises a two wire transmission line coextensive with each other, commonly fed from said transmitter and being disposed relative to said roadway such that one wire is located on each side thereof; and additionally including radio signal amplifier means selectively coupled to each line of said two wire transmission line intermediate the ends thereof for boosting the signal strength of said radio signal to a predetermined level.

5. A radio communications system as defined in claim 1, wherein said pair of radio signal shield means each comprises: a plurality of supporting structures having grounding means; a plurality of horizontally extending shield wires substantially parallely disposed and defining a substantially vertical plane extending from at least the plane of said roadway to a predetermined distance above said radiation antenna means and being supported and connected at selected horizontal intervals to one of said plurality of supporting structures and grounding means; and at least one shield wire mounted on and connected to said one supporting structure and positioned away from said plurality of shield wires toward said roadway such that it is substantially coplanar with one shield wire of said plurality of shield wires.

6. A radio communications system as defined in claim 1, wherein said pair of radio signal shield means each comprises: a plurality of supporting structures; a plurality of substantially horizontally extending shield wires defining a substantially vertical plane extending from at least the plane of said roadway to a predetermined distance above said radiation antenna means and being supported at selected horizontal distance intervals along said roadway by one of said plurality of supporting structures; at least one shield wire mounted on said one supporting structure and positioned away in offset relationship from said plurality of shield wires toward said roadway such that it is substantially horizontally coplanar with one shield wire of said plurality of shield wires; and means for electrically grounding all of said shield wires.

'7. A radio communications system as defined in claim 1, wherein said pair of radio signal shield means each comprises a plurality of shield wires mounted on an electrically grounded support, said plurality of shield wires being disposed substantially parallel to the surface of the earth and defining a first substantially vertical plane extending from at least the plane of the roadway to a predetermined distance above said radiation antenna means, means for grounding said plurality of shield wires to said grounded support; said radiation antenna means located a predetermined distance above the surface of the earth; at least one additional shield wire mounted on said grounded support and being offset toward said roadway from said plurality of shield wires and positioned above said antenna means a predetermined distance such that it defines a substantially horizontal plane with one of said plurality of shield wires and a second substantially vertical plane with said antenna means; and still at least another shield wire embedded in the earth a predetermined distance below the ground and intermediate the said first vertical plane and said roadway.

8. A system as defined by claim 1, wherein said pair of radio signal shield means each comprises a plurality of shield wires strung substantially horizontally between supports having grounding means located at selected distance intervals along said roadway, said plurality of shield wires defining a substantially vertical plane extending from at least the surface of the earth to a predetermined distance above said radiation antenna means, means for grounding said plurality of shield wires to said grounding means, at least one other shield wire strung between said supports and adapted to be ofiset therefrom toward said roadway such that one of said plurality of shield wires and said other shield wire defines a substantially horizontal plane above said antenna means with respect to the surface of the roadway, said other shield wire defining yet another substantially vertical plane with respect to the surface of the roadway with said antenna means; and yet another shield wire embedded beneath the surface of the earth running substantially parallel with said other shield wire and said antenna means and lying substantially in said yet another vertical plane as defined by said yet another shield wire and said antenna means.

9. A radio communications system as defined by claim 1, wherein said antenna means comprises a two wire transmission line, forming two radiating wire antennas running on opposite sides of said roadway, commonly driven from said signal source, supports having grounding means positioned at predetermined distances along each side of said roadway, each wire antenna mounted on and insulated from said sup orts on the respective side of said roadway, and wherein said pair of radio signal shield means each comprises a plurality of shield wires mounted on said supports and electrically connected to said grounding means and defining a substantially vertical plane extending from at least the plane of the roadway to a predetermined distance above the respective wire antenna and positioned behind a respective wire antenna in relation to said roadway; at least another shield wire mounted on said supports and electrically connected to said groundmg means, but ofiset threfrom such that it lies in another vertical plane as defined by it and said respective wire antenna; and still another shield wire embedded in the earth running parallel and coextensive with said wire antenna and lying in said another vertical plane, whereby all of said shield wires provide a radio signal shield on three sides of each of said radiating wire antennas.

References Cited UNITED STATES PATENTS 1,985,241 12/1934 Daya 34384l X 2,980,793 4/1961 Daniel 325129 3,105,119 9/1963 Cary et al 32526 ROBERT L. GRIFFIN, Primary Examiner.

BENEDICT V. SAFOUREK, Assistant Examiner.

U.S. c1. X.R.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1985241 *Jun 30, 1932Dec 25, 1934Werner DayaDevice for removing disturbances in wireless transmission
US2980793 *Jun 11, 1956Apr 18, 1961Electronic Safety EngineeringRestricted range radio transmitting system
US3105119 *Apr 7, 1960Sep 24, 1963Gen Motors CorpHighway communication system
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4097808 *Apr 2, 1976Jun 27, 1978Marine Electric CorporationEntertainment system and method
US4983984 *Nov 25, 1987Jan 8, 1991Sumitomo Electric Industries, Ltd.Roadside beacon system with polarized beams
US5983075 *Apr 8, 1997Nov 9, 1999Toyota Jidosha Kabushiki KaishaRadio communication system between a vehicle and a roadside station
US6314272 *Apr 30, 1998Nov 6, 2001Visteon Global Technologies, Inc.Radio frequency broadcast system for enclosed spaces
Classifications
U.S. Classification455/129, 340/901, 455/523, 343/841
International ClassificationG08G1/0962, G08G1/0967, H01Q1/32
Cooperative ClassificationG08G1/096758, G08G1/096716, H01Q1/3225, G08G1/096783
European ClassificationG08G1/0967C2, G08G1/0967A1, G08G1/0967B3, H01Q1/32A4