CA1276041C - Multi-frequency vehicular antenna system - Google Patents
Multi-frequency vehicular antenna systemInfo
- Publication number
- CA1276041C CA1276041C CA000533880A CA533880A CA1276041C CA 1276041 C CA1276041 C CA 1276041C CA 000533880 A CA000533880 A CA 000533880A CA 533880 A CA533880 A CA 533880A CA 1276041 C CA1276041 C CA 1276041C
- Authority
- CA
- Canada
- Prior art keywords
- antenna
- vehicle
- length
- transmission line
- conductive wire
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/27—Adaptation for use in or on movable bodies
- H01Q1/32—Adaptation for use in or on road or rail vehicles
Abstract
MULTI-FREQUENCY VEHICULAR ANTENNA SYSTEM
ABSTRACT OF THE DISCLOSURE
An antenna system which operates over a wide spectrum or radio frequencies by utilizing a body of a vehicle as an antenna.
The antenna system comprises a tuned impedance-matching coupler and a uniquely-configured floating, low-capacitance coaxial transmission line. In this arrangement, the outer conductor of the transmission line connecting the coupler to the vehicular body is severed at both ends. Thus, electrical connection between the coupler and the vehicle body is provided only by the transmission line's center conductor and the line's capacitive coupling. Antenna performance with the instant configuration exhibits improved voltage standing wave ratios and field strength as compared to conventional radio antennas.
ABSTRACT OF THE DISCLOSURE
An antenna system which operates over a wide spectrum or radio frequencies by utilizing a body of a vehicle as an antenna.
The antenna system comprises a tuned impedance-matching coupler and a uniquely-configured floating, low-capacitance coaxial transmission line. In this arrangement, the outer conductor of the transmission line connecting the coupler to the vehicular body is severed at both ends. Thus, electrical connection between the coupler and the vehicle body is provided only by the transmission line's center conductor and the line's capacitive coupling. Antenna performance with the instant configuration exhibits improved voltage standing wave ratios and field strength as compared to conventional radio antennas.
Description
4~
Field of_Sb~-luv~i~Inn The present lnvention relates to an antenna system, and more partlcularly~ to a multi-frequency vehicular antenna.
5 Backaro~
Previous attempts to incorporate the body or a vehicle as an antenna have proven ineffective. Because o~ tne unusual characteristics and difficult problems encountered in extracting usable radio frequency ~RF) signals from such conductive 1U structures, the state o~ the art has developed slowly.
A number o~ patents have ~een issued in this ~ield, but nolle of the technlques taught in the prior art are s1milar to those disclosed in the present invention, nor have the earlier inventlons worked well in practice.
15UoS~ Patent No. 3,717,876 to Volkers, "~errite Antenna Couplea to Radio Frequency Currents in Vehicle Boay," describes a cascade arrangement wherein a Faraday cage acts as t~e primary antenna, which intercepts the electromagnetic waves ana ,~ reradiates them to a secondary antenna wlth in the Faraday cage.
In one o~ such arrangements, the body of an automobile is used as the Faraday cage while a ~errite antenna is used as the secondary antenna.
U.S. Patent No. 3,916,413 to Davis, "Remotely Tuned Conductive-Boay Antenna System," discloses a voltage and impedance transformer applied to increase the inductive reactance of coupling to the vehicle body. Such coupling is achieved by ,, . ~: . . .
`` ~6Q41 using the magnetic signal from the fine wire antenna in t~e windshield/w~ndow or a wnip antenna on most automobiles.
V.S. Patent No. 3t9~1,330 to Davis, "Antenna System Utllizing Currents in Conductive Body," an lmprovement over the a~orementioned antenna system to the sanle inventor, includes coupllng at locations such as a vertical column o~ the vehicle where the conductive body has reduced cross section.
U.S~ Patent No. 4,100,546 to Campbelll "Airborne ~nten~a System Employlng the Airframe A6 ~n ~ntenna," teaches a phase front homing ~ystem airborne antenna array employlng portions OL
the vertical landing gear struts as antenna elements. This system obtains the desired homing direction by measuring t~le phase difference between slgnals plcked up by t~le two antenna elements.
Finally, U.S. Patent No. 4,117,490 to ~rnold e~
"Inconspicuous Antenna System Employing ~he Airfrarne ~s An Antenna/" also disc1Oses a phase front homing system airborne antenna array application, wnich is improved by inclusion o~
discrete coaxial coupling sleeves in the landing struts.
The inventor is unaware o~ appllcations utilizlng the novel arrangements more fully describea below, nor appllcations wnerein the above-describea prior art has been successfully implemented.
Inventor's empirical data~ on the other hand, demonstrate tt~e e~ficacy o~ the instant invention~
..
.
~mmary of the Inv~n~l~n It i~ an object o~ the present inve~tion to provide a vehicular antenna system whose elements are concealecl or inconspicuous~
Another o~ject ~ ~he instant invention is to provide a vehic~lar antenna system that is relatively simple in construction and coniguration, thus minimizing manufacturillg, installation and maintenance costs.
A further o~ject o~ this lnvention is ~o provide a multl-frequency system that e~ficiently and op~imally operates over a broad spectrum o~ radio ~requencies.
~ leretofore approaches utilizing the bocly o~ a vehicle as a radiatlng element have ~ocused on the application o~ center-fec~
loading o~ various ki.nds. These appllcations have not been successful because such conductive ~odies have a low radiation resistance and high inductive reactance.
Although operating a vehicle as an end-fed dipo~e would be preferrable in theory because such a system's RF radiation resistance would be materially raised by a ~actor o~ at least fifty as compared to a center-fed configuration, the inventor has determined that a center-fecl loading point provides optimal performance. That is, connecting the telecommunication device such as a ~ransmitter, receiver or a transceiver to the vehicle at a central location minimizes the inductive reactance and high capacitance to ground. This arrangement, however, is compllcated by the distributed capacitance o~ any transmission line installec~
~6~
on th~ vehicle wnich causes RF losses by capaci~a~ce coupl1ng.
The a~ove-describea problem is resolved by utilizlng a heretofore unused property of the transmission line--its capaci~ance.
5In sum, the instant vehicular antenna system uniquely creates an impedance match tO the body o~ tne vehicle~ The impedance match lS achieved by a novel configuration utilizlng a low-capacitance coaxial transmission lineO He~e, the outer conductor or the transmission line is floated; tnerefore, only its capacitive e~ect and the center conductor are electrically connected in the antenna system. The aavantages or this arrangement are exhibited by low voltage standing wave ratios (VSWRs) and high field strength measurements over a broad range o~ radio Erequencies, which are superior to those attained by conventlonal antenna~.
The present invention has been reduced to practlce over a w1de range o~ ~requencies--the mobile band~ 26.175 - 2/.5U0 Ml~z, more popularly known as the citizens' band (CB): the FM
commercial broadcast band, 88-1~8 MHz; and the amateur radio 20band, 220-224 MHz. In general terms, these frequency ranges encompass the radio ~requencies commonly known as the lower V~IF
band, the upper V~F band, and the ~HF band.
The features o~ the invention believed to be novel are set ~orth Wlth particularity ln the appended claims. The invention itself, however, both as to organization and method o~ operation, together wlth further o~jects and aavantages thereof, may be DeSt 4~
understood by reference to the followlng aescription taken in conjunct~on wlth ~he accompanylng arawlngsO
- otner o~je~ts and advantages o~ the invention wlll be apparent from the followlng ~escription and the accompanylng drawlngs wnich are for the purpose o~ lllustratlon only.
Figure lA iB a block diageam o~ one embodiment or a vehicular antenna system according to the present invention which operates in che lower VHF band ~1~ L~ i8 an enlargement showlng the aetails or Figure Ei~LQ_~ is a DloGk diagram or a second embo~imènt or t~le vehicular antenna system according to the present invention wnich l$ operates ln che upper VHF and UHF bands;
Ei~9L~ is an enlargement snvwlng the details o~ Figure 2A;
Eig9L~ 1 iS a slde elevation view o~ the vehicular antenna coupler;
~iaure 4 is a schematic aiagram or the vehicular antenna coupler ahowlng a combination Pi and Gamma impedance-matchirlg network; and Figure 5 i9 a aetailed elevation view or a ~yplcal coaxial transmiasion line showing the floating outer conductor configuration.
~2~76~4~
4~Ql_Q~_Ibe ~*f~L ~mbodiments ~f the Ipyention The present invention eelates to a uniquely-configured multl-frequecy vehicular antenna system which u~ es the sur~ace or outer metallic skin o~ a vehicle as an antennaO
secause the principles ~ the present in~ention are equ~ly advantageous over a wide range o~ ~requencies and a variety Ot vehicles, it lS not the inventor's intent to limit the princiE~les of ~i-.e present invention to the specific embodiments illustrated below .
lo The instant antenna system has numerous appllcations. A
partlcular applicatlon in the C~ band concerns vehicular security alarm systems. Such systems ~ave proverl quite popular in recent years due to increased concern by the general publlc for crime preventlon. The ~ollowlng des~ription o~ the claimed invention concerns this particular application.
An au~omo~ile is approximately ~ifteen feet long. Thus, at 2/ M~lz, a commonly used CB frequency, the automobile's length is about one-half wavelenqth. A9 a radiating element such a vehicle lS lneffective, however, because it operates as a dipole very low to the ground, having small ratio o~ wavelength to diameter and an inductive load. Its ~adiàtion resistance is about ten ohms (real component) wlth a nigh reactive component which must be tuned out to achieve optimum radiation performance.
Figure lA is a block diagram or a ~irst embodiment o~ the instAnt vehicular antenna system for CB appllcations (2/ MHz).
This drawing ShOWS a typical arrangement ok the antenna system ~2~76~
while ~igure lB i~ a detailed enlargement s~owlng the inaividual elements. The antenna ~ystem is compri~ed or an impedànce-matching coupler 1, represented ~chematically in Figure 4, wnich is connected at i~s input connector 2 to a telecommunication device 3 via a transmission line 4. The coupler 1 is enclosed in an electrically conductive housing 5. The antenna system also includes a second coaxial transmission line 6, basically comprised o~ an outer conductor 7 and a c~nter conductor 8.
Further describing Figures lA and lB, transmission line 6 lo connecting coupler 1 to tne vehicle is attached to coupler 1 at an ou~put connector 9. The other end or transmission line 6 is attached to bocy 10 of the vehicle at a central location 11.
When connecting ~he transmission line 6 to the vehicle body lU it i~ preferrable to attach the line to the outer surface or skin or the vehicle 1nstead or i~s chassis. Although connection can be made to the chas~is or other parts o~ the vehicle frame/ for example wnen the outer skin o~ the vehicle is nos~-conductive, this is not recommended because rusting commonly occurs along these areas and wlll cause the vehicle's electrical resistance, 2U and hence the antenna's radiation performance, ~o change. The coupler 1 is grounded at the rear o~ the vehicle at a location 12 along the bo~y 10 which is as ~ar away as pract1cable from the vehicle'q center 11.
The arorementioned individual elements are slmple, but the manner in wnich these elements are configured makes the instant system unique. The claimed arrangement minimizes the ~2'7~
distributive capacitance due to tran6mission line 6 over i~s entir~ length trom output connector 9 to the central point 11 on the vehic1e. This novel configuration is achieve~ by floating the transmission line 6, which has a lOw capacitance per unit length.
A typical low-capacitance transmission line 6 is illu~trated in Figure 5. The cable includes an outer conductor or braide~ shield 7 (the "braid"3, a center conductor 8, a polyurethane or other dielectric core 13, and a jack2t 14.
1()As detailed in Figures lB and 5, th~ transmission ]ine's outer conductor 7 at each end or the line 6 is intentionally severea and is le~t mechanically unconnected to the rest o~ tne antenna system~ This is accomplished by cutting out a sec~ion o~
the braid 7 from a low-capacitance RG-6~ coaxial cable approximately a quarter inch at each end ~hereof; tnus, leaving a ; gap, L, at both ends o~ the transmission line 6. One gap is located at the rear o~ the vehicle wnere transmission line 6 connects to the coupler's output connector 9 via a mating connector 15, and a second gap i8 positioned near the central point 11 on the surface 10 of the vehicle.
In practlce, one method or connecting transmission line 6 to the central point 11 on the vehicle is by placing conductor 8 in a hole drilled under the door or the vehicle and securir-g conductor 8 to the surface with a sneet metal screw or other suitable ~astener. Thus, metal~to-metal contact provides Eirm electrical contac~ ~etween the transmission line and the vehicle.
~;~761~
The llne 6 is then placed under the ~loor mat and laid to a rearward location 12, typically the trunk o~ the vehicle, wnere the coupler 1 is connected to the vehicle body 10.
Thus, the coaxial transmission line 6 simply acts electrically as a capacitor and e~fectively appears to tne coupler 1 as an addi~io~al element o~ series capacitance. That is, such series capacitance lS comprised o~ a ~:irst capacitance from braid 7 to the vehiele at the central point 11, and a secol3d capacitance from braid 7 to the center conductor 8. If tne instant arrangement i8 not utilize~, on ~he other hand, the Shunt capacitance o~ CranSmiOESiOn line 6 wlll dissipate RF energy ~rom the radiation resistance and suboptimal antenna radiation perforn)ance will be o~tained.
Figure 3 shows a aetailed slde elevation view or one embo~iment or the vehieular antenna eoupler 1. lhe housing 5 encloses the impedance-matehing network, Figure 4, wlth input connector 2 and ou~put connector 9 situated on opposite sldes or the housing 5. Both connectors 2, 9 utilize a conventional coaxial arrangement with a center feed eonductor (not snown) and an outer ground eonductor (not snown).
Further describing Figure 3, a rear wall (not snown) of housing 5 is attaehed to a plate 16. The plate 16 provides a slotted eage 17 to faeilitate eonnection o~ the housing 5 to the surface 10.
Turning now to the sehematie diagram o~ Figure 4, the inventor has determined that the vehiele's low impedance can be ~Z76~
matched by utilizlng a turled coupler equipped wlth a combincltion of conventlonal lmpedance-rnatching networks.
While either a Pi or Gamma-type network, alolle, results in VSWRs o~ a~out 1.30, the combination o~ such networks represented in ~he schematic aiagram achieves near-perfect coupling.
As shown ln Figure 4, capacitor C provides an aadi~ional divislon to the Pi network comprised o~ inductor L and capacitors C and C r allowlng C to match very low RF radiation resistances, such a~ that provided by the vehicle. The Pi network meanwnile e~fectively tune~ out the vehicle's inductance and thus provides a proper match to tne antenna system.
Capacitor C is equal to the sum o~ the capacitances from the center conductor 8 to the braid 7 and that from the braid 7 to the vehicle rrame at the connection point 11. ~his arrangement, therefore, matches the respective capacitive elementS, the low radiation resistance, and the high lnductance OL the vehicle.
The capacitors are adjusted for minimum VS~R by using a conventlonal VSWR bridge in line with the circuit. When the coupler 1 is installed wlth the housing 5 connected at tne rearward location 12 of the vehicle, and the coaxial cable is dressed to the outer skin o~ the vehicle, a VSWR OL 1.10 iS
readily achievea.
The above-described embodiment, as expected, operates slmilarly to a dipole operat~ng very close to gro~nd. Its performance characteristic~ in the CB band, however, are superior to those oDtained by conventional 36-inch wnip antennas commonly ~:7~
in use, either wlth or without loading coils.
The radiat1On generated from the instant antenna system is horizontal in polarity with some vertlcal components. Co~pared to the operation o~ the 36-inch Whip antenna, t~le fie]d strength of such arranyement is lncreased several times and has a very high angle or radiation. In ~act, it is nearly isotropic.
This is advantageous for alarm systems in that the antenna's radiation can penetrate many more floors ln an apartment buildi~lg than the Whip antenna, wni~h has a null at the vertical elevation of its radiation pattern. Full penetXation in rein~orced concrete buildings up to l~ floors high has been o~served Wlth a vehicle parke~ irl the basement. This is more than three tlmes the number or rloors penetrated ~y t~e 36-inch whip antenna.
Tests have also been conducted using an alarm system at 15 21.045 M~lz and data lndicate that suitable antenna performance lS
achieved at distances o~ 2-3 miles in rolling terrain and 3-4 miles ~n rlat terrain~
Finallyt convent~onal vehicular security alarm systems currently marketed typically u~ilize a vehicle's external radio antenna or an auxiliary e~uivalent which allows the alarm system to operate with retractable antennas. The instant invention, however, utilizes the entire vehicle as the antenna and ~eeps all of i~s components concealed. Therefore, the instant invention prevents a would-be thie~ ~rom conveniently removing the antenna and rendering ~he alarm ~ystem lnoperable.
A second embodiment o~ the present invention wnich operates in the ~pper VHF an~ UHF bands 1~ ~nown ln Figures 2A and 2s.
More particularly, the followlng discussion describes an Application at broadcast FM frequencies. At the midpoint o~ the FM band, 98 MHz, a vehicle is about 1.5 wavelengt~ls long. The vehicle's telecommunication device 3 is typically in a f ixe~
location approximately five ~eet behind the front o~ the vehicle.
In this configuration, the coupler 1 is positioned aajacent to the device 3 and connec~ed to it via transmission line 4. Here, in~uctor L is modified to resonate in the FM band and requires five turns as compared to the 18-turn inductor for CB
applications. AB in the CB application, the transmission line's outer conductor 7 is ~loating and the center conductor 8 is connected at a rearward point 18 on the vehicle surface 10.
In tnis arrangement, the inventor has also achieved 1~ excellent antenna performance. Since it is desirable to cover the entire FM band from 88 to 108 MHz, tuning the coupler 1 to the frequency 95 MHz achieves optimum performance. Therefore, at ; any frequency across the F~ band a maximum VSWR o~ 2.20 is achieved. Such operation is aaequate for reception purposes.
Utllizlng t~2e vehicle as an antenna in this frequency band has major advantages over conventional antènnas~ First, the entire sur~ace o~ ~he vehicle e~fectively integrates ~M signals received uirectly by line-of-sight ~rom the FM radio station, by reflectlons ~rom buildings, and by reflections ~rom the inversion layer in the atmosphere. Thus, little if any multipath distortlon and plcket-fencing commonly ~ound wlth FM reception in ~%~6~
vehicle~ using conventional vertical antennas has ~een oDserved in ~he lnstant case7 Second, radiation performance o~ the instant antenna system operating at FM is superior to that o~ conventional systems.
Although FM signals are vertically polarize~ in the near electrical ~ield and better reception is provided wlth a 36 inch whip in this range as compared to the horizontal or elliptical polarization in che present invention, empirical data indicate that antenna performance with the claimed invention in the far lo electrical ~ield regions, wnere re1ections occur, is superior.
Such improved performance in the far field is attributable to its elliptical and integrating features.
In Figure 2B, transmission line 6 is dimensi~ned to be rive feet or preferably ten feet in length. At ten feet, the transmission line 6 represents about one wavelength in tlle F~
band. Again, low-capacitance RG-62 coaxial cable can be utllizea.
The present invention has also operated successfully at broadcast frequencies higher than the two embo~iments just describea. Tests have been conducted by using t~e vehicular antenna system ln the two-meter amateur band (144-148 M~z) with satis~actory performance. Again, the integrat1ng ~eatures or this novel system provided slgnificant advantage~ over tne performance or a conventional vertical wtlip ln ttle ~ar Eield.
Further, test ~ata indicate that satis~actory performance lS
achieved in ~he amateur ~and ~220-224 MHz~. The instant antenna ~7~
system, therefore, can he operated at 150-160 Mllz for police work wnere excellent communication long distances from tne statlon can be oDtained wlthout tne use o~ an external conventlonal antennaO
While the embodiments o~ this inven~ion operate in the CB, ~M and amateur radio bandsr the instant antenna system employlng the general principles discussed can similarly operate in other radlo rrequency bands throughout the V~F and UHF range.
Thus, moaification to the preferred embodiments or the inventlon can be made and other embodiments may be ~evised wlth in the spirit o~ the invention and the scope o~ the appended claims.
Field of_Sb~-luv~i~Inn The present lnvention relates to an antenna system, and more partlcularly~ to a multi-frequency vehicular antenna.
5 Backaro~
Previous attempts to incorporate the body or a vehicle as an antenna have proven ineffective. Because o~ tne unusual characteristics and difficult problems encountered in extracting usable radio frequency ~RF) signals from such conductive 1U structures, the state o~ the art has developed slowly.
A number o~ patents have ~een issued in this ~ield, but nolle of the technlques taught in the prior art are s1milar to those disclosed in the present invention, nor have the earlier inventlons worked well in practice.
15UoS~ Patent No. 3,717,876 to Volkers, "~errite Antenna Couplea to Radio Frequency Currents in Vehicle Boay," describes a cascade arrangement wherein a Faraday cage acts as t~e primary antenna, which intercepts the electromagnetic waves ana ,~ reradiates them to a secondary antenna wlth in the Faraday cage.
In one o~ such arrangements, the body of an automobile is used as the Faraday cage while a ~errite antenna is used as the secondary antenna.
U.S. Patent No. 3,916,413 to Davis, "Remotely Tuned Conductive-Boay Antenna System," discloses a voltage and impedance transformer applied to increase the inductive reactance of coupling to the vehicle body. Such coupling is achieved by ,, . ~: . . .
`` ~6Q41 using the magnetic signal from the fine wire antenna in t~e windshield/w~ndow or a wnip antenna on most automobiles.
V.S. Patent No. 3t9~1,330 to Davis, "Antenna System Utllizing Currents in Conductive Body," an lmprovement over the a~orementioned antenna system to the sanle inventor, includes coupllng at locations such as a vertical column o~ the vehicle where the conductive body has reduced cross section.
U.S~ Patent No. 4,100,546 to Campbelll "Airborne ~nten~a System Employlng the Airframe A6 ~n ~ntenna," teaches a phase front homing ~ystem airborne antenna array employlng portions OL
the vertical landing gear struts as antenna elements. This system obtains the desired homing direction by measuring t~le phase difference between slgnals plcked up by t~le two antenna elements.
Finally, U.S. Patent No. 4,117,490 to ~rnold e~
"Inconspicuous Antenna System Employing ~he Airfrarne ~s An Antenna/" also disc1Oses a phase front homing system airborne antenna array application, wnich is improved by inclusion o~
discrete coaxial coupling sleeves in the landing struts.
The inventor is unaware o~ appllcations utilizlng the novel arrangements more fully describea below, nor appllcations wnerein the above-describea prior art has been successfully implemented.
Inventor's empirical data~ on the other hand, demonstrate tt~e e~ficacy o~ the instant invention~
..
.
~mmary of the Inv~n~l~n It i~ an object o~ the present inve~tion to provide a vehicular antenna system whose elements are concealecl or inconspicuous~
Another o~ject ~ ~he instant invention is to provide a vehic~lar antenna system that is relatively simple in construction and coniguration, thus minimizing manufacturillg, installation and maintenance costs.
A further o~ject o~ this lnvention is ~o provide a multl-frequency system that e~ficiently and op~imally operates over a broad spectrum o~ radio ~requencies.
~ leretofore approaches utilizing the bocly o~ a vehicle as a radiatlng element have ~ocused on the application o~ center-fec~
loading o~ various ki.nds. These appllcations have not been successful because such conductive ~odies have a low radiation resistance and high inductive reactance.
Although operating a vehicle as an end-fed dipo~e would be preferrable in theory because such a system's RF radiation resistance would be materially raised by a ~actor o~ at least fifty as compared to a center-fed configuration, the inventor has determined that a center-fecl loading point provides optimal performance. That is, connecting the telecommunication device such as a ~ransmitter, receiver or a transceiver to the vehicle at a central location minimizes the inductive reactance and high capacitance to ground. This arrangement, however, is compllcated by the distributed capacitance o~ any transmission line installec~
~6~
on th~ vehicle wnich causes RF losses by capaci~a~ce coupl1ng.
The a~ove-describea problem is resolved by utilizlng a heretofore unused property of the transmission line--its capaci~ance.
5In sum, the instant vehicular antenna system uniquely creates an impedance match tO the body o~ tne vehicle~ The impedance match lS achieved by a novel configuration utilizlng a low-capacitance coaxial transmission lineO He~e, the outer conductor or the transmission line is floated; tnerefore, only its capacitive e~ect and the center conductor are electrically connected in the antenna system. The aavantages or this arrangement are exhibited by low voltage standing wave ratios (VSWRs) and high field strength measurements over a broad range o~ radio Erequencies, which are superior to those attained by conventlonal antenna~.
The present invention has been reduced to practlce over a w1de range o~ ~requencies--the mobile band~ 26.175 - 2/.5U0 Ml~z, more popularly known as the citizens' band (CB): the FM
commercial broadcast band, 88-1~8 MHz; and the amateur radio 20band, 220-224 MHz. In general terms, these frequency ranges encompass the radio ~requencies commonly known as the lower V~IF
band, the upper V~F band, and the ~HF band.
The features o~ the invention believed to be novel are set ~orth Wlth particularity ln the appended claims. The invention itself, however, both as to organization and method o~ operation, together wlth further o~jects and aavantages thereof, may be DeSt 4~
understood by reference to the followlng aescription taken in conjunct~on wlth ~he accompanylng arawlngsO
- otner o~je~ts and advantages o~ the invention wlll be apparent from the followlng ~escription and the accompanylng drawlngs wnich are for the purpose o~ lllustratlon only.
Figure lA iB a block diageam o~ one embodiment or a vehicular antenna system according to the present invention which operates in che lower VHF band ~1~ L~ i8 an enlargement showlng the aetails or Figure Ei~LQ_~ is a DloGk diagram or a second embo~imènt or t~le vehicular antenna system according to the present invention wnich l$ operates ln che upper VHF and UHF bands;
Ei~9L~ is an enlargement snvwlng the details o~ Figure 2A;
Eig9L~ 1 iS a slde elevation view o~ the vehicular antenna coupler;
~iaure 4 is a schematic aiagram or the vehicular antenna coupler ahowlng a combination Pi and Gamma impedance-matchirlg network; and Figure 5 i9 a aetailed elevation view or a ~yplcal coaxial transmiasion line showing the floating outer conductor configuration.
~2~76~4~
4~Ql_Q~_Ibe ~*f~L ~mbodiments ~f the Ipyention The present invention eelates to a uniquely-configured multl-frequecy vehicular antenna system which u~ es the sur~ace or outer metallic skin o~ a vehicle as an antennaO
secause the principles ~ the present in~ention are equ~ly advantageous over a wide range o~ ~requencies and a variety Ot vehicles, it lS not the inventor's intent to limit the princiE~les of ~i-.e present invention to the specific embodiments illustrated below .
lo The instant antenna system has numerous appllcations. A
partlcular applicatlon in the C~ band concerns vehicular security alarm systems. Such systems ~ave proverl quite popular in recent years due to increased concern by the general publlc for crime preventlon. The ~ollowlng des~ription o~ the claimed invention concerns this particular application.
An au~omo~ile is approximately ~ifteen feet long. Thus, at 2/ M~lz, a commonly used CB frequency, the automobile's length is about one-half wavelenqth. A9 a radiating element such a vehicle lS lneffective, however, because it operates as a dipole very low to the ground, having small ratio o~ wavelength to diameter and an inductive load. Its ~adiàtion resistance is about ten ohms (real component) wlth a nigh reactive component which must be tuned out to achieve optimum radiation performance.
Figure lA is a block diagram or a ~irst embodiment o~ the instAnt vehicular antenna system for CB appllcations (2/ MHz).
This drawing ShOWS a typical arrangement ok the antenna system ~2~76~
while ~igure lB i~ a detailed enlargement s~owlng the inaividual elements. The antenna ~ystem is compri~ed or an impedànce-matching coupler 1, represented ~chematically in Figure 4, wnich is connected at i~s input connector 2 to a telecommunication device 3 via a transmission line 4. The coupler 1 is enclosed in an electrically conductive housing 5. The antenna system also includes a second coaxial transmission line 6, basically comprised o~ an outer conductor 7 and a c~nter conductor 8.
Further describing Figures lA and lB, transmission line 6 lo connecting coupler 1 to tne vehicle is attached to coupler 1 at an ou~put connector 9. The other end or transmission line 6 is attached to bocy 10 of the vehicle at a central location 11.
When connecting ~he transmission line 6 to the vehicle body lU it i~ preferrable to attach the line to the outer surface or skin or the vehicle 1nstead or i~s chassis. Although connection can be made to the chas~is or other parts o~ the vehicle frame/ for example wnen the outer skin o~ the vehicle is nos~-conductive, this is not recommended because rusting commonly occurs along these areas and wlll cause the vehicle's electrical resistance, 2U and hence the antenna's radiation performance, ~o change. The coupler 1 is grounded at the rear o~ the vehicle at a location 12 along the bo~y 10 which is as ~ar away as pract1cable from the vehicle'q center 11.
The arorementioned individual elements are slmple, but the manner in wnich these elements are configured makes the instant system unique. The claimed arrangement minimizes the ~2'7~
distributive capacitance due to tran6mission line 6 over i~s entir~ length trom output connector 9 to the central point 11 on the vehic1e. This novel configuration is achieve~ by floating the transmission line 6, which has a lOw capacitance per unit length.
A typical low-capacitance transmission line 6 is illu~trated in Figure 5. The cable includes an outer conductor or braide~ shield 7 (the "braid"3, a center conductor 8, a polyurethane or other dielectric core 13, and a jack2t 14.
1()As detailed in Figures lB and 5, th~ transmission ]ine's outer conductor 7 at each end or the line 6 is intentionally severea and is le~t mechanically unconnected to the rest o~ tne antenna system~ This is accomplished by cutting out a sec~ion o~
the braid 7 from a low-capacitance RG-6~ coaxial cable approximately a quarter inch at each end ~hereof; tnus, leaving a ; gap, L, at both ends o~ the transmission line 6. One gap is located at the rear o~ the vehicle wnere transmission line 6 connects to the coupler's output connector 9 via a mating connector 15, and a second gap i8 positioned near the central point 11 on the surface 10 of the vehicle.
In practlce, one method or connecting transmission line 6 to the central point 11 on the vehicle is by placing conductor 8 in a hole drilled under the door or the vehicle and securir-g conductor 8 to the surface with a sneet metal screw or other suitable ~astener. Thus, metal~to-metal contact provides Eirm electrical contac~ ~etween the transmission line and the vehicle.
~;~761~
The llne 6 is then placed under the ~loor mat and laid to a rearward location 12, typically the trunk o~ the vehicle, wnere the coupler 1 is connected to the vehicle body 10.
Thus, the coaxial transmission line 6 simply acts electrically as a capacitor and e~fectively appears to tne coupler 1 as an addi~io~al element o~ series capacitance. That is, such series capacitance lS comprised o~ a ~:irst capacitance from braid 7 to the vehiele at the central point 11, and a secol3d capacitance from braid 7 to the center conductor 8. If tne instant arrangement i8 not utilize~, on ~he other hand, the Shunt capacitance o~ CranSmiOESiOn line 6 wlll dissipate RF energy ~rom the radiation resistance and suboptimal antenna radiation perforn)ance will be o~tained.
Figure 3 shows a aetailed slde elevation view or one embo~iment or the vehieular antenna eoupler 1. lhe housing 5 encloses the impedance-matehing network, Figure 4, wlth input connector 2 and ou~put connector 9 situated on opposite sldes or the housing 5. Both connectors 2, 9 utilize a conventional coaxial arrangement with a center feed eonductor (not snown) and an outer ground eonductor (not snown).
Further describing Figure 3, a rear wall (not snown) of housing 5 is attaehed to a plate 16. The plate 16 provides a slotted eage 17 to faeilitate eonnection o~ the housing 5 to the surface 10.
Turning now to the sehematie diagram o~ Figure 4, the inventor has determined that the vehiele's low impedance can be ~Z76~
matched by utilizlng a turled coupler equipped wlth a combincltion of conventlonal lmpedance-rnatching networks.
While either a Pi or Gamma-type network, alolle, results in VSWRs o~ a~out 1.30, the combination o~ such networks represented in ~he schematic aiagram achieves near-perfect coupling.
As shown ln Figure 4, capacitor C provides an aadi~ional divislon to the Pi network comprised o~ inductor L and capacitors C and C r allowlng C to match very low RF radiation resistances, such a~ that provided by the vehicle. The Pi network meanwnile e~fectively tune~ out the vehicle's inductance and thus provides a proper match to tne antenna system.
Capacitor C is equal to the sum o~ the capacitances from the center conductor 8 to the braid 7 and that from the braid 7 to the vehicle rrame at the connection point 11. ~his arrangement, therefore, matches the respective capacitive elementS, the low radiation resistance, and the high lnductance OL the vehicle.
The capacitors are adjusted for minimum VS~R by using a conventlonal VSWR bridge in line with the circuit. When the coupler 1 is installed wlth the housing 5 connected at tne rearward location 12 of the vehicle, and the coaxial cable is dressed to the outer skin o~ the vehicle, a VSWR OL 1.10 iS
readily achievea.
The above-described embodiment, as expected, operates slmilarly to a dipole operat~ng very close to gro~nd. Its performance characteristic~ in the CB band, however, are superior to those oDtained by conventional 36-inch wnip antennas commonly ~:7~
in use, either wlth or without loading coils.
The radiat1On generated from the instant antenna system is horizontal in polarity with some vertlcal components. Co~pared to the operation o~ the 36-inch Whip antenna, t~le fie]d strength of such arranyement is lncreased several times and has a very high angle or radiation. In ~act, it is nearly isotropic.
This is advantageous for alarm systems in that the antenna's radiation can penetrate many more floors ln an apartment buildi~lg than the Whip antenna, wni~h has a null at the vertical elevation of its radiation pattern. Full penetXation in rein~orced concrete buildings up to l~ floors high has been o~served Wlth a vehicle parke~ irl the basement. This is more than three tlmes the number or rloors penetrated ~y t~e 36-inch whip antenna.
Tests have also been conducted using an alarm system at 15 21.045 M~lz and data lndicate that suitable antenna performance lS
achieved at distances o~ 2-3 miles in rolling terrain and 3-4 miles ~n rlat terrain~
Finallyt convent~onal vehicular security alarm systems currently marketed typically u~ilize a vehicle's external radio antenna or an auxiliary e~uivalent which allows the alarm system to operate with retractable antennas. The instant invention, however, utilizes the entire vehicle as the antenna and ~eeps all of i~s components concealed. Therefore, the instant invention prevents a would-be thie~ ~rom conveniently removing the antenna and rendering ~he alarm ~ystem lnoperable.
A second embodiment o~ the present invention wnich operates in the ~pper VHF an~ UHF bands 1~ ~nown ln Figures 2A and 2s.
More particularly, the followlng discussion describes an Application at broadcast FM frequencies. At the midpoint o~ the FM band, 98 MHz, a vehicle is about 1.5 wavelengt~ls long. The vehicle's telecommunication device 3 is typically in a f ixe~
location approximately five ~eet behind the front o~ the vehicle.
In this configuration, the coupler 1 is positioned aajacent to the device 3 and connec~ed to it via transmission line 4. Here, in~uctor L is modified to resonate in the FM band and requires five turns as compared to the 18-turn inductor for CB
applications. AB in the CB application, the transmission line's outer conductor 7 is ~loating and the center conductor 8 is connected at a rearward point 18 on the vehicle surface 10.
In tnis arrangement, the inventor has also achieved 1~ excellent antenna performance. Since it is desirable to cover the entire FM band from 88 to 108 MHz, tuning the coupler 1 to the frequency 95 MHz achieves optimum performance. Therefore, at ; any frequency across the F~ band a maximum VSWR o~ 2.20 is achieved. Such operation is aaequate for reception purposes.
Utllizlng t~2e vehicle as an antenna in this frequency band has major advantages over conventional antènnas~ First, the entire sur~ace o~ ~he vehicle e~fectively integrates ~M signals received uirectly by line-of-sight ~rom the FM radio station, by reflectlons ~rom buildings, and by reflections ~rom the inversion layer in the atmosphere. Thus, little if any multipath distortlon and plcket-fencing commonly ~ound wlth FM reception in ~%~6~
vehicle~ using conventional vertical antennas has ~een oDserved in ~he lnstant case7 Second, radiation performance o~ the instant antenna system operating at FM is superior to that o~ conventional systems.
Although FM signals are vertically polarize~ in the near electrical ~ield and better reception is provided wlth a 36 inch whip in this range as compared to the horizontal or elliptical polarization in che present invention, empirical data indicate that antenna performance with the claimed invention in the far lo electrical ~ield regions, wnere re1ections occur, is superior.
Such improved performance in the far field is attributable to its elliptical and integrating features.
In Figure 2B, transmission line 6 is dimensi~ned to be rive feet or preferably ten feet in length. At ten feet, the transmission line 6 represents about one wavelength in tlle F~
band. Again, low-capacitance RG-62 coaxial cable can be utllizea.
The present invention has also operated successfully at broadcast frequencies higher than the two embo~iments just describea. Tests have been conducted by using t~e vehicular antenna system ln the two-meter amateur band (144-148 M~z) with satis~actory performance. Again, the integrat1ng ~eatures or this novel system provided slgnificant advantage~ over tne performance or a conventional vertical wtlip ln ttle ~ar Eield.
Further, test ~ata indicate that satis~actory performance lS
achieved in ~he amateur ~and ~220-224 MHz~. The instant antenna ~7~
system, therefore, can he operated at 150-160 Mllz for police work wnere excellent communication long distances from tne statlon can be oDtained wlthout tne use o~ an external conventlonal antennaO
While the embodiments o~ this inven~ion operate in the CB, ~M and amateur radio bandsr the instant antenna system employlng the general principles discussed can similarly operate in other radlo rrequency bands throughout the V~F and UHF range.
Thus, moaification to the preferred embodiments or the inventlon can be made and other embodiments may be ~evised wlth in the spirit o~ the invention and the scope o~ the appended claims.
Claims (15)
1. In combination with a vehicle having an electrically conductive body, an antenna for a telecommunication device which comprises:
a length of conductive wire having one end electrically connected to said body, said length being determined by the frequency range of the telecommunication device;
a floating electromagnetic field insulated from said body and surrounding said length of wire;
an impedance coupling means having a bipolar input terminal and a single output terminal, said output terminal being connected to the other end or said length or wire;
cover means in electrical contact with said body for electromagnetically shielding said coupling means; and conductor means for connecting said bipolar input terminal to the antenna terminal of the telecommunication device.
a length of conductive wire having one end electrically connected to said body, said length being determined by the frequency range of the telecommunication device;
a floating electromagnetic field insulated from said body and surrounding said length of wire;
an impedance coupling means having a bipolar input terminal and a single output terminal, said output terminal being connected to the other end or said length or wire;
cover means in electrical contact with said body for electromagnetically shielding said coupling means; and conductor means for connecting said bipolar input terminal to the antenna terminal of the telecommunication device.
2. The antenna or claim 1 wherein said conductive wire and said floating electromagnetic shield are dialectrically insulated from each other to maintain a low capacitance between them at the operating frequency of said telecommunication device.
3. The antenna of claim 2 operating in the lower VHF band wherein said one end of conductive wire is connected to a substantially central point on said vehicle body.
4. The antenna of claim 2 operating in the upper VHF and UHF
bands wherein said length of the conductive wire is dimensioned electrically to be a substantial portion of one wavelength at the frequency being utilized.
bands wherein said length of the conductive wire is dimensioned electrically to be a substantial portion of one wavelength at the frequency being utilized.
5. The antenna or claim 4 wherein said one end or conductive wire is connected to a point laterally spaced apart from the substantially central point on said vehicle body.
6. The antenna of claim 3 wherein said impedance coupling means comprises a combination Pi and Gamma network.
7. The antenna of claim 3 wherein said conductive wire and said floating electromagnetic shield are made from a length of coaxial transmission line.
8. The antenna or claim 3 wherein said electrically conductive body is the metallic outer skin of the vehicle.
9. The antenna of claim 3 wherein said electrically conductive body is the chassis of the vehicle.
10. The antenna of claim 6 wherein said impedance coupling means includes means for adjustably tuning the combination Pi and Gamma network.
11. The antenna of claim 5 wherein said impedance coupling means comprises a combination Pi and Gamma network.
12. The antenna of claim 5 wherein said conductive wire and said floating electromagnetic shield are made from a length of coaxial transmission line.
13. The antenna of claim 5 wherein said electrically conductive body is the metallic outer skin of the vehicle.
14. The antenna of claim 5 wherein said electrically conductive body is the chassis of the vehicle.
15. The antenna of claim 11 wherein said impedance coupling means includes means for adjustably tuning the combination Pi and Gamma network.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/848,519 US4751514A (en) | 1986-04-07 | 1986-04-07 | Multi-frequency vehicular antenna system |
| US848,519 | 1986-04-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1276041C true CA1276041C (en) | 1990-11-06 |
Family
ID=25303510
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000533880A Expired - Lifetime CA1276041C (en) | 1986-04-07 | 1987-04-06 | Multi-frequency vehicular antenna system |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4751514A (en) |
| CA (1) | CA1276041C (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4134415A1 (en) * | 1991-10-17 | 1993-04-22 | Hirschmann Richard Gmbh Co | AERIAL RECEPTION PROCEDURE |
| DE9116931U1 (en) * | 1991-12-04 | 1994-11-03 | Rohde & Schwarz | Radio frequency direction finder for motor vehicles |
| US5918183A (en) * | 1992-09-01 | 1999-06-29 | Trimble Navigation Limited | Concealed mobile communications system |
| US5629693A (en) * | 1993-11-24 | 1997-05-13 | Trimble Navigation Limited | Clandestine location reporting by a missing vehicle |
| KR0170493B1 (en) * | 1995-12-08 | 1999-03-30 | 양승택 | Non-blocking fault tolerance gamma network for multi-processor system |
| US5793336A (en) * | 1996-06-10 | 1998-08-11 | Antennas America, Inc. | Conformal antenna assemblies |
| FR2785094A1 (en) * | 1998-10-27 | 2000-04-28 | Thomson Csf | HF skywave land vehicle radio antenna, has curved whip aerial one end with variable capacitance earth connected and other end transformer primary earth connecting and secondary inputting regulating voltage. |
| BRPI0416625A (en) * | 2003-11-17 | 2007-01-16 | Sst Wireless Inc | bodywork antenna |
| US7804029B1 (en) * | 2008-12-05 | 2010-09-28 | The United States Of America As Represented By The United States Department Of Energy | Electromagnetic wrap |
| FR2946803B1 (en) * | 2009-06-12 | 2011-06-24 | Peugeot Citroen Automobiles Sa | DEVICE FOR COUPLING A TRANSMITTER AND / OR ELECTROMAGNETIC WAVE RECEIVER TO A METALLIC STRUCTURE USED AS ANTENNA. |
| FR2952490B1 (en) * | 2009-11-09 | 2012-07-06 | Peugeot Citroen Automobiles Sa | EMITTING AND / OR ELECTROMAGNETIC WAVE RECEIVER SYSTEM COMPRISING A METAL STRUCTURE AS A MULTI-DIAGRAM ANTENNA |
| US20130342326A1 (en) * | 2012-06-22 | 2013-12-26 | United States Of America As Represented By The Administrator Of The National Aeronautics And Spac | Systems, apparatuses, and methods for transparent and ubiquitous sensing technology |
| US10147291B2 (en) * | 2014-05-15 | 2018-12-04 | Melo Tarcisio Caddah | System and method for protecting restricted-access areas against intrusions by pedestrians and/or non-cab vehicles in general, with access permitted for vehicles with a cab, including convertible vehicles with closed top |
| US11362409B2 (en) | 2018-06-14 | 2022-06-14 | Wicked Technology Corporation | Antenna assembly with universal whip mount and method of tuning the same |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1792193A (en) * | 1927-06-06 | 1931-02-10 | Howard D Colman | Transmitting antenna |
| US3646561A (en) * | 1971-01-19 | 1972-02-29 | Edwin B Clarke | Adhesively secured automobile windshield antenna |
| US3717876A (en) * | 1971-04-23 | 1973-02-20 | Volkers Res Corp | Ferrite antenna coupled to radio frequency currents in vehicle body |
| US3961330A (en) * | 1973-12-21 | 1976-06-01 | Ross Alan Davis | Antenna system utilizing currents in conductive body |
| US3916413A (en) * | 1973-12-21 | 1975-10-28 | Ross Alan Davis | Remotely tuned conductive-body antenna system |
| US4117490A (en) * | 1977-08-15 | 1978-09-26 | The United States Of America As Represented By The Secretary Of The Army | Inconspicuous antenna system employing the airframe as an antenna |
| US4160977A (en) * | 1978-02-23 | 1979-07-10 | Davis Ross A | Automobile antenna |
| US4317121A (en) * | 1980-02-15 | 1982-02-23 | Lockheed Corporation | Conformal HF loop antenna |
| US4331961A (en) * | 1980-04-08 | 1982-05-25 | Davis Ross A | Windshield antenna |
-
1986
- 1986-04-07 US US06/848,519 patent/US4751514A/en not_active Expired - Fee Related
-
1987
- 1987-04-06 CA CA000533880A patent/CA1276041C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| US4751514A (en) | 1988-06-14 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1276041C (en) | Multi-frequency vehicular antenna system | |
| US6999032B2 (en) | Antenna system employing floating ground plane | |
| US6018324A (en) | Omni-directional dipole antenna with a self balancing feed arrangement | |
| CA1313408C (en) | Wide band antenna for mobile communications | |
| US6298243B1 (en) | Combined GPS and cellular band mobile antenna | |
| US4658259A (en) | On-glass antenna | |
| CA1287916C (en) | Near-isotropic low-profile microstrip radiator especially suited for use as a mobile vehicle antenna | |
| US5406295A (en) | Window antenna for a motor vehicle body | |
| US5880695A (en) | Antenna system for wireless comunication systems | |
| EP0590955A2 (en) | Multiple band antenna | |
| US6069589A (en) | Low profile dual frequency magnetic radiator for little low earth orbit satellite communication system | |
| WO1997041619A1 (en) | Composite antenna for cellular and gps communications | |
| CA2495265A1 (en) | Combination satellite and terrestrial antenna | |
| US5311201A (en) | Multi-band antenna | |
| US6496152B2 (en) | Dual polarized antenna | |
| US5926149A (en) | Coaxial antenna | |
| JPH0374846B2 (en) | ||
| GB2272575A (en) | Dual band antenna | |
| US5945950A (en) | Stacked microstrip antenna for wireless communication | |
| JP2002530909A (en) | Patch antenna device | |
| US5298907A (en) | Balanced polarization diversified cellular antenna | |
| USRE33743E (en) | On-glass antenna | |
| US5497167A (en) | Antenna for mounting on a vehicle window | |
| EP0824766A1 (en) | Antenna unit | |
| US6384696B1 (en) | Multiplexer for sorting multiple signals from an antenna |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |