US 2520986 A
Description (OCR text may contain errors)
Sept. 5, 1950 F. B. WILLIAMS ETAL VEHICULAR-ANTENNA SYSTEM Filed 061;. 22, 1947 2 Sheets-Sheet 1 48 mom RECEIVER IIYVENTORS.
ZZ/LZZazma Sept. 5, 1950 F. B. WILLIAMS ETAL VEHICULAR ANTENNA SYSTEM 2 Sheets-Sheet 2 Filed Oct. 22, 1947 I INVENTORS. Bed 5.
RADIO close to the pickup loops.
3 Referring now to Fig. 1 there is disclosed an automobile having a metallic body If.- AI. though an automobile is disclosed by way of example; it is to be pointed out that any otheir body made of conducting material can be used Although a great number of difierent loops are formed by such an automobile body, it has been; found that the loops of maximum signal pickup: which are displaced at a suficiently wide angle: so that the signal therefrom can be combined. to provide a substantially non-directional pat-- tern are the conducting paths shown generally by the dotted lines designated 2 and I3, respec-- tively. The reasons these paths provide maxi mum signal is that the paths indicated provide a loop of a very large area and form a conducting path of relatively low impedance. Although it is possible to make connections to the vehicle body to pick up signals from the loops directly, this system has an inherent disadvantagei'n' that the loops are continuous and the portion of the Vehicle body between any designated pickup points causes a relatively low impedance shortacross the antenna. This difficulty is avoided by picking up the signals from the loop circsiitss formed in the vehicle body inductively, and ductive pickup loops for accomplishing this plEK'-- pose are illustrated in Figs. 2 to 10, inclusive.
Fig2 is a perspective View illustrating the inside of the front portion of the automobile Ill. The top I5 is an integral part of the metal body doors l6 and I? are secured to the body, and windshield portions I3 and I9 and a dashrZU are illustrated. Inductive pickup loops 2|" and 22 are positioned on either side at the front between the.- portions l8 and IQ of the windshield and the adjacent doors IE and I1. The pickup loops are secured to the car body and are positioned at substantially right. angles thereto as shown in Fig. 3. It is apparent that the coils are limited in length to the space between the top of the 22 are adapted to be connected by cables 23 and 24 toa wave signal device such as the receiver 25 whichis illustrated as mounted under the dash 20 of the automobile [0.
In Fig. 4 the physical construction of the pickup loops is' shown. Each of the loops includes a single turn of wire which is mounted on the edge of an insulating form 3| which may be of any suitable material such as paper, wood or plastic. An insulating form 1 inch wide, inch thick and 18 inches long has been found to be a suitable size for installation in an automobile without taking up too much space and obstructing the view unduly and yet to be of sufiicien-t siz to form a relatively efficient pickup coil. The form may have rounded corners as indicated at 29 so that the loop will fit close to the automobile body. In order to provide a neat appearance the insulating form 3| and coil 30 may be covered by upholstery material 32 identical to that used in the vehicle in which the loops are installed. As will be described, transformers for coupling the loops to a lead-in cable are desiraJble in some instances and should be positioned These transformers may be very small and made with the pickup coils as a single unit as indicated at 3! in Fig. 4.
The transformers may also be covered by the upholstery material 32 so that they are relatively inconspicuous. For securing the pickup loops to the car body, brackets 33 may be provided. The brackets may be secured to the vehicle body by screws or other suitable means, it being 1513 151 916 in many automobiles to use screws which secure the molding about the windshield thereby eliminating the need for additional screws or for defacing the vehicle in any manner.
In Fig. 5, there is illustrated a circuit which may be used for coupling the loops 2| and 22 to the input circuit of a radio receiver. This is accomplished by connecting the loops 2| and 22 to primary windings 35 and 36 of transformers- 3'! and 38, respectively. The transformers include secondary windings 39 and 4B which are connected through coaxial cables 23 and 24 to the radio receiver. To eliminate interference in the lead-ins, coaxial cables are used with one side of the transformer being connected to the center conductor and the other side of the transformer and the shield of the coaxial lead-in being grounded. The coaxial lead-ins extend to a radio receiver 4| including a vacuum tube 42 having a :grid 43 to which the input signal is applied. The receiver illustrated includes a tuning inductance 44 and a trimmer condenser 45 in the input circuit to which the antenna 22 is connected in the usual manner. The antenna 2| is connected in series with inductance 46 which is substantially :identical to the tuning inductance 44 and condenser 41 which is substantially identical to the input trimmer condenser 45.- For coupling the antenna 2| to the receiver a condenser 48 is pro-'- wided which forms a common path for the two loop antennas. Circuits for coupling spaced loop antennas to a radio receiver are disclosed in our copending application referred to above and also in application for patent of Fred B. Williams, Fred P. I-Iilt, and William Blinoff on Antenna Coupling Systems, Serial No. 781,282, filed concurrently herewith. As such systems are not specifically a part of the present invention, they will not be described in detail.
Although the pickup loops 2| and 22 are illustrated as mounted on the roof supports between the windshield portions and the adjacent doors, it is apparent that the signal in the effective loop circuits in the vehicle body could be picked up by installing the loops in other positions. The position chosen is believed best because the roof supports are of relatively small cross section and the currents flowing in the paths through the body as indicated by lines 12 and I3 of Fig. l are -concentrated more at these points than at any other points along the path. As the currents through these parts are, therefore, concentrated the pickup of the loops is more eiiective at these points. As previously stated, the pickup loops should be mounted so that one side of the loop is as close to the vehicle body as possible so that magnetic lines linking the loop circuits formed in the car body will also link the pickup loops. For this same reason it is also desirable that the pickup loops have as large a cross-sectional area as possible. This size is, of course, limited as the pickup loops must take up a minimum amount of space and must not obstruct the view of the driver and passengers in the vehicle and must, therefore, extend into the vehicle as small a distance as possible. In tests made, it has been found that pickup loops in which the conductors 'are spaced approximately 1 inch apart provide a very satisfactory signal pickup.
The pickup loops 2| and 22 have been described as being used to pick up signals from the loop circuits in the car body inductively and when positioned as shown in Fig. 3, the pickup loops are effectively shielded by the conducting portion of the car body 50 that they cannot directly pick up signals from outside the car body. The pickup loops may be so positioned to pick up signals directly from the air and the signal thus picked up may add to the signal picked up due to the inductive coupling with the car body to increase the signal strength.
In Figs. 6 and '7, there is illustrated amodified pickup loop which has also been developed for use with automobile radio receivers. The loop is formed by a strip of thin metallic foil 58 which is positioned inside the door support on the automobile body. The conducting foil can be held inplace by a strip of tape 5|. The metallic foil and tape are both very thin thus not interfering with the closing of the car door. The car door is effective to conceal the conducting strip and tape when the door is closed. The paint on the door support insulates the foil from the automobile body but, of course, allows the foil to be very close to the body. A conductor '52 is attached to the foil at the top and extends inside the car body and down along the upholstery between the window portion it and the door Hi. In most automobiles a roll of material is provided about the edge of the door to which the conductor 52 can be secured. Such roll is indicated at 53 in Figs. 6 and 7 and may be used to support theconductor away from the automobile body. The conductor 52 is connected to a transformer 31 as is conductor 5d which is connected to the conducting foil 5d at the bottom end thereof. The metallic foil 58 and conductors 52 and 54 form a closed loop which is completely equivalent to the loop formed by the wire 39, the loop being connected to the transformer 3'3 in exactly the same way as in the modification shown in Figs. 2 to 5. Although a loop is illustrated on only one side of the automobile in Fig. 6, in accordance with the invention, loops may be positioned on both sides of the automobile and connected to a radio receiver in the same manneras illustrated in the previous modifications.
member 66 is wider so that a large number of turns of wire El can be wound thereon. In pickup loops actually constructed, an insulating form approximately 1 inches wide, inch thick and 13 inches long was used with a coil of wire having 12 turns wound thereon. The corners of the form adjacent the body were rounded as indicated at 62 so that the coil could be positioned closely adjacent the vehicle body. Such a coil had an inductance of approximately 50 microhenries and was used in a circuit as illustrated in Fig. 9. In this circuit the coils 63 and 64 are connected to primary windings 65 and 65, respectively, of coupling units which include secondary windings 61 and E8 the inductance of which is variable. The coupling units are so constructed that when using movable cores for varying the inductances of the secondary windings, the inductance of the primary windings is not substantially affected by the position of the cores. The secondary windings are connected in series resonant circuits including trimmer condensers $9 and i0 and a common coupling condenser 'H. The circuits are tuned to the desired frequencies by the variable inductance seoondary windings El and 68. The coupling condenser ll applies the signal from the pickup loop 64 to the resonant circuit for the pickup loop 63 in the proper phase relationship so that the signals are combined to provide an input signal to the receiver having a substantially non-directional characteristic. The circuit for connecting the loops to a radio receiver is described more in detail in the copending application Serial No. 781,282 referred to above.
Inductive pickup coils may also be used for applying a radio frequency signal to a receiver which is tuned by variable condensers. In such a system the pickup loops may have a still larger number of turns to provide a very high inductance. Fig. 10 illustrates an antenna input circuit for use with such higher impedance loops in which the loop i2 forms the inductance of the input circuit which is tuned by a variable condenser lt to cover the desired band of frequencies. The second loop M is connected in series with variable condenser 15 which is similar to tuning condenser '13. The condenser '35 is common to both circuits to couple the antenna Hito the receiver. It is to be noted that coupling transformers are not required at the loops.
It is seen from the foregoing description that we have provided an antenna system for a mobile vehicle which utilizes the signal pickup by the conducting vehicle body. The antenna system is very easily installed and may be entirely enclosed within the vehicle body so that the appearance of the vehicle is in no way altered. It is obvious that the pickup loops may be positioned on the vehicle body in other positions than adjacent the roof supports as described. The pickup loops may also be positioned outside the vehicle but such loops have the same disadvantage as rod antennas that mounting provisions must be made. Also the pickup loop would have to be more rigid for outside mounting and would have to be waterproofed and styled to conform to the particular car body. The antenna disclosed also does not require defacing of the vehiclein any way as the mounting of the small pickup loops can be accomplished Without damaging the vehicle. As the pickup loopsthemselves and the loop circuits formed in the automobile are disposed at an angle of between a degreesand 90 degrees with respect to each other, the signals from the two loops can be combined to provide a substan tially non-directional pickup pattern. This is desirable so that reception is not afiected by the direction in which the vehicle is moving or the position of the vehicle with respect to the wave signal device with which the device in the vehicle is communicating. The antenna system in accordance with the invention is superior to the normal rod-type vehicle antennas in that it is not substantially aifected by shielding caused by viaducts, bridges and the like through which the vehicle may move.
While we have described certain embodiments of our invention which are illustrative thereof, it is obvious that various changes and modifications can be made therein without departing from the intended scope of the invention as defined in the appended claims.
1. An antenna system comprising a body for an automobile having a metal portion and an insulating windshield, said metal portion being of such configuration that a pair of closed loop circuits are formed therein extending on the op- 'posite sides of said windshield, a pair of'loops supported on said body on opposite sides of said windshield, said loops including portions positioned closely adjacent to said metal portion with the planes of said loops being substantially perpendicular to the said metal portion and means for coupling said loops together in such phase relation that a substantially non-directional antenna system is obtained.
2. An antenna system for an automobile having a metal body including roof. supporting portions on either side of a windshield comprising, a pair of loops supported on said roof supporting portions, said loops being so positioned to be in inductive relation with efiective loop circuits formed in said body and. extending through said roof supporting portions, and means for coupling said loops together in such phase relation that a substantially non-directional antenna system is obtained.
3. An antenna system for a mobile vehicle including a body having conducting portions and insulating portions comprising, a pair of loops supported within said body, each of said loops being positioned with respect to said body to be in inductive relation with a closed loop circuit formed in said conducting portions, and means for coupling said loops together in such phase re lation that a substantially non-directional antenna system is obtained. 1
l. An antenna system comprising a conducting body, said body being of such configuration that a pair of effective loop circuits are formed therein which are disposed with respect to each other at a substantial angle, a pair of pickup loops positionecl on said body, each of said pickup loops being in inductive relation with one of said effective loop circuits in said body, and means coupling said pickup loops together in such phase relation that a substantially non-directional antenna system is obtained.
5. An antenna system for a wave signal device which is adapted to be installed in a mobile vehicle having a conducting body comprising, a portion of said body, said portion being of such configuration that a pair of efiective closed loop circuits are defined thereby which are disposed with respect to each other at a substantial angle, a pair of pickup loops positioned on said body portion in inductive relation with said efiective loop circuits, and means coupling said pickup loops together in such phase relation that a substantially non-directional antenna system is obtained.
6. An antenna system comprising a conducting body, said body being of such configuration that a pair of effective closed loop circuits are formed therein the planes of which are disposed with respect to each other at a substantial angle, a pair of elongated pickup loops positioned individually in the planes of said loop circuits with an elongated portion of each pickup loop closely adjacent said conducting body, and means coupling said pickup loops together in such phase relation that a substantially non-directional antenna system is obtained.
7. An antenna system for a wave signal device adapted to be installed in a mobile vehicle hav- 1 ing a conducting body comprising at least a portion of said body which is of such configuration that a pair of effective angularly disposed loop circuits are formed therein, a pair of pickup loops positioned in the planes of said loop circuits with a portion of each pickup loop closely adjacent said body, and means coupling said pickup loops together in such phase relation that a substantially non-directional antenna system isobtained.
8. Anantenna system for a wave signal device adapted to be used in a mobile vehicle having a conducting body comprising, a pair of elongated pick-up loops supported on said body and being individually in inductive relation to closed loop circuits formed in said body, each of said pickup loops having long sides one of which is positioned closely adjacent a portion of said body throughout the length thereof, and means for connecting said pick-up loops to said wave signal device in such phase relation that a substantially non-directional antenna system is obtained. 7
9. An antenna system for a wave signal device adapted to be installed in a mobile vehicle having a conducting body, comprising at least a portion of said body which is of such configuration that a, pair of eiiective spaced loop circuits are formed therein, a pair of pickup loops positioned a on said body in inductive relation with said eiTective loop circuits, and means for connecting said pick-up loops to said wave signal device to provide a non-directional antenna pattern.
10'. An antenna system comprising the metal body for a mobile vehicle having a configuration such that a pair of closed loop circuits are formed therein which are disposed at a substantial angle with respect to each other, a pair of pick-up loops supported on said body and positioned with respect to said body tobe innindividual inductive relation with said closed loop circuits formed in said body, each of said pick up loops including a single turn of wire mounted on an insulating form, and means coupling said pick-up loops together in such phase relation that a substantially non-directional antenna system is obtained.
11. An antenna system comprising a body for an automobile having a conducting portion and an insulating windshield, said conducting portion being of such configuration that a'pair of loop circuits are formed therein extending on the opposite sides of said windshield, a pair of pickup loops each including a single turn, of wire, said loops being supported on said body on opposite sides of said windshield with a part of eachturn positioned closely adjacent a portion of said conducting portion, and means coupling said pickup loops together in suchphase relation that a substantially non-directional antenna system is obtained.
12. An antenna system for an automobile having a conducting body and a plurality of doors hinged to door supports on said body so that a pair of angularly disposed effective loop circuits are formed in said conductive body com prising, a pair of pickup loops supported on said body in inductive relation to said effective lo'op circuits formed in said body, each of said pickup loops including a strip of metal foil secured to one of said door supports and conductors secured to the ends of said strip of foil to form a loop having a single turn. 7
13. The method of providing radio frequency signals for a wave signal receiver installed. in an automobile having a conducting body which comprises, inductively picking upsignals from loop circuits formed in said conducting body at a of points thereon combining said signals picked up to provide a signal for said receiver'which is substantially independent of the direction of the source thereof.
14. The method of providing radio frequency signals for a wave signal receiver. installedin' a vehicle having a body at least a portion of which is conducting which comprises, inductively picking up signals from angularly disposed loop circuits formed in said conducting portion, and combining said signals picked up to \provide a signal for said receiver which is substantially independent of the direction of the source thereof.
15. An antenna system for a wave signal device in a mobile vehicle, such antenna system including in combiantion, a three-dimensional vehicle body having conductive portions which afford a closed loop circuit and also having open insulating portions, at least one of said conductive portions having a restricted cross-section, and means for coupling said closed loop circuit to said Wave signal device including an elongated pickup loop positioned within said vehicle body with one longitudinal side thereof closely adjacent to said restricted conductive portion of said body and the opposite side of said pickup loop spaced from all said conductive portions of said vehicle body by a distance at least as great as the width of said pickup loop, said pickup loop extending lengthwise of said restricted conductive portion and being positioned with respect thereto to be substantially entirely shielded from signals outside said vehicle body, so that signals are picked up by said pickup loop substantially entirely by induction from said closed loop circuit.
16. In a mobile vehicle having an electrically conductive body in which an effective loop circuit is defined, and in which vehicle an electronic receiver is mounted, an antenna system for inductively picking up signals from said loop circuit and applying the same to said receiver ineluding in combination, an elongated insulating coil form of fiat configuration positioned within said body with one longitudinal'edge thereof closely adjacent to a portion of said conducting body defining said loop circuit and the opposite longitudinal edge thereof spaced from said conducting body by a distance at least as great as the width of said coil form, and a pickup loop Wound around the edges of said coil form, said form being narrow so that said pickup loop as a whole is disposed in proximity to said body portion, and is substantially entirely shielded thereby from signals outside said conductive body, whereby signals are picked up :b said loop substantially entirely by induction from the loop circuit in said body.
FRED B. WILLIAMS.
FRED P. HILL.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,158,124 Fessenden Oct. 26, 1915 1,912,234 Willoughby May 30, 1933 2,129,852 Leib Sept. 13, 1938 2,202,368 Berndt May 28, 1940 2,329,634 McDonald Sept. 14, 1943 2,353,111 Davis July 4, 1944 2,404,093 Roberts July 16, 1946 2,481,978 Clough Sept. 13, 1949