US2094168A - Antenna system - Google Patents

Description

7 Sept. 28, 1937. c. FQRBES 2, 8

ANTENNA SYSTEM Filed Aug. 4, 1934 2 Sheets-Sheet 1 INVENTOR HENRY C. FORBES Mp 5, M14

ATTORNEY Sept. 28; 1937. H. c. FORQBES 2,094,168

ANTENNA SYSTEM Filed Aug. 4, 1934 2 Sheets-Sheet 2 INVENTOR hgE NRY c. amass.

ATTOR EY Patented Sept. 28, 1937 UNITED STATES PATENT OFFICE,

ANTENNA SYSTEM poration of Delaware Application August 4,

3 Claims.

This invention pertains to radio antenna installation and particularly to antenna installations that are adapted to be used for automotive vehicles.

One of the objects is to provide an antenna installation that will reduce power wire and trolley wire pick-up by a radio antenna, without proportionately reducing the signal pick-up.

Another object is to provide an antenna installation in balanced relation to ground, such as the car frame.

These objects are accomplished by variously installing on a vehicle antenna parts of proper characteristics, and connecting them in series and with a transmission system to the receiver.

A further object, is to provide a unitary struc ture for the transmission system in the form of a harness for coupling the antenna to a receiver, so that the signal pick-up may be impressed upon the receiver without an attendant impression of power wire and trolley wire pick-up, or ignition noises.

These and other objects are accomplished by providing a coupling unit for the antenna and receiver that includes a pair of matching transformers each having a coil connected by leads with a coil of the other, and the transformers, and lead wires incased in a shielding braid, or the like, adapted for grounding to the frame of the vehicle.

One of the objects is to provide an antenna system that increases the ratio of signal strength to noise.

This is accomplished by providing an antenna that takes advantage of the difference in directions of the approaching wave fronts that generally exists between the signal and noise w'aves.

Another object is to provide an antenna system that increases the ratio of signal strength to noise and efficiently transmits the signal to a radio receiver.

This is accomplished by providing an antenna that takes advantage of the difference in directions of approaching wave fronts that generally exists between the signal and noise waves, and by providing a proper transmission systemfor impressing the signal thus isolated upon the receiving circuit.

Further objects and advantages of the present invention will be apparent'from the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a perspective View ofa vehicle illus- 1934, Serial No. 738,447

trating in diagrammatic form the instant invention as applied thereto.

Figs. 2, 3, and 4 each illustrate modifications of the installation.

Fig. 5 is a longitudinal sectional view, with certain parts broken away, illustrating structural details of a harness unit or transmission line forming part of the instant invention.

Fig. 6 is a transverse sectional view, substantially as indicated by the line and arrows 66 of Fig. 5, and

Fig. '7 is a transverse sectional view substantially as illustrated by the line and arrows 1-1' of Fig. 5.

One of the chief objections to automotive radio in a city is the large amount of noise pick-up with a sensitive receiver when driving under a trolley wire, power line, or in fact, any wires carrying electric current, having switching transients or commutation disturbances.

A like objection is found in radio installations in dwellings and the like where the receiver is located in close proximity to power wires or conductors. While the instant invention ofiers a solution for all such problems, it will be described principally as an installation for vehicles, but it is to be understood that the disclosure pertains to and proposes to include an installation on'immovable structures where like problems are to be solved.

It is well known that radio waves are polarized, that is, have a component largelyin a single plane. In the broadcast band, the waves are largely plane polarized, and are substantially vertically polarized, particularly in the vicinity of the broadcast station. At greater distances, the wave front may be inclined to the vertical, but the polarization remains largely plane, and largely vertical.

The common sources of noise disturbances are,

however, such that the field components often exist in other planes, particularly when the source is a nearby trolley wire or power wire. This difference in the plane of polarization of the noise disturbances and the desired signals makes possible the use of a type of antenna for an automobile that will permit the desired signal pick-up, but which will not pick up the noise disturbances, so that an improvement in the signal to noise ratio, over the usual car antenna will be possible.

This may be illustrated by assuming that a vehicle equipped with the proposed antenna installation is situated somewhat remote from the broadcast station, and moving along a street with an overhead trolly wire. It is well known that energized conductors, which include both the transmitting antenna and the trolly wire, are attended by radiation fields, which are the carrier, so to speak, of the signal and noise impulses. Energized conductors are also attended by induction fields that are relatively strong in the near proximity of the conductors but rapidly diminish at increasing distances from the conductor. The principle of operation that is believed to obtain comprehends the relation of the radiation and induction fields of both the power wire and the transmitting antenna.

These various fields are conceivable as each comprising more or less concentric waves emanating in substantially perpendicular planes from the respective conductors. As is well known to those skilled in the art, at the above assumed position of the vehicle, the induction field of the power wire is much the stronger, since that line being of low frequency is attended with only a negligible radiation field. The transmitting antenna being at a relatively great distance, and of high frequency, is manifest at the assumed location of the vehicle, by the radiation field only; the induction field having diminished so much as to be negligible. Therefore, the receiving antenna of the vehicle in the assumed location, will be subjected only to the induction field of the power wire and the radiation field of the transmitting antenna. The wave fronts of the radiation field from the transmitting antenna, due to the greater distance, and therefore large radius of curvature, are substantially vertical by the time they reach the receiving antenna, and create a potential in the receiving antenna that is greater than the ground potential, so that a signal voltage is applied to the receiver from the antenna. The wave front of the induction field from the trolly wire, the noise source, due to the lesser distance, and relative position of the receiving antenna system, will be practically parallel to the earth surface, and it creates two and opposite currents in the antenna sections that cancel out in the winding of the transformer. Thus the signal from the broadcast station will be effectively picked up without the attendant noise component.

As a practical solution of this problem, a plane or position is found for an antenna on an auto mobile, that will permit efficient signal pick-up and yet will have little or no pick-up for noises from nearby power lines. Such a desirable location for an antenna on an automobile, and one answering the requirements is in the top, where antenna parts such as a piece or pieces of screen, approximately the equivalent of 3 feet x 5 feet or an equivalent area may be used as suggested in the drawings. But other types and forms of antenna-elements may be used as an alternative, as will appear from the pages that follow. A leadin is brought down one of the posts to the receiver and in order to prevent spark noise pick-up by the lead-in, it is shielded, at least for a part of its length. If the lead-in is shielded, then it may be run close to other conduits or tubing, and yet be effectively shielded from disturbing noises. The capacity of the antenna itself is comparatively low, certainly less than 200 micro-micro-farads, and probably less than 125 micro-micro-farads, and this resulting mis-match of impedances, when such a low capacity antenna is connected to a high capacity lead-in, would effect considerable losses in efficiency.

It is proposed therefore to provide a coupling means at the junction of the antenna and leadin, so as to properly match the impedance of a shielded lead-in to the antenna, thus permitting the use of a totally shielded lead-in, which to gether will give improved antenna efiiciency, due to proper matching. A coupling device at the receiver, is so designed as to match the input impedance of the receiver to that of the line. This may be accomplished by a device separate from the regular antenna coil, if necessary, and where so done both coupling devices may be enclosed within the shield as a unit of construction and installation.

With particular reference to the drawings, Fig. 1 illustrates in diagrammatic form an installation of radio receiver and antenna, with a transmission line therefor, and depicting all of the features of the instant invention. In this particular instance, the plane desirable for disposition of the antenna exists in the top or roof 2% of a vehicle generally indicated by reference numeral 22. Two antenna parts 24 and 26, which may be embodied in appropriate sections of copper screening, are embodied in the top or roof construction, and are serially connected to a winding 28 of a coupling unit or impedance matching device 29. Inductively coupled with the winding 28, there is a second winding 33 whose terminals are joined to a pair of leads or conductors 32 and 34. The conductors are of sufiicient length to make a convenient mounting of a radio receiver 36, in some available space about the vehicle body, which is diagrammatically illustrated in the drawings as back of the motor-board and in front of the instrument panel, or that space usually recognized as the cowl of an automobile.

While the leads 32 and 3 1 are illustrated as being twisted it is not necessary that they be twisted but they may be parallel if closely spaced. A second coupling unit or impedance matching device 48, has a winding 62 whose terminals are also connected with the conductors 32 and 34, and the winding 42 is inductively coupled to a second winding 44 whose leads 43 and 45 are adapted for connection into the hereinbefore mentioned receiver 36.

That part of the transmission line between the antenna parts and the receiver has been previously designated as a harness, and it is constructed as a subassembly unit according to the disclosure set out in Figs. 5, 6 and 7. In addition to the elements just set out, the harness includes shielding means 45 which substantially encloses both of the coupling units 29, 49, as well as the conductors or leads joining the windings of one with the windings of the other.

As disclosed in Fig. 1, the antenna parts 24 and 2B, are mounted on opposite sides and similarly placed as respects the medial line of the vehicle, In Fig. 2 the installation is varied somewhat, in that the antenna parts 2G and 26 are arranged in a fore and aft position and substantially similarly located along the medial line of the vehicle. With respect to Fig. 3, the antenna parts comprise loops and branches of a more or less continuous conducting element as indicated at 24a, 24b, 24c and 26a, 26b and 260. According to the disclosure in Fig. 4, the antenna elements comprise metal bands 24d and 26d forming the tire covers in the popularly known sport model vehicle. In each instance of the disclosures of Figs. 1 to 4, inclusive, the antenna parts are connected in series through the coupler winding 28 included in the transmission line which eventually leads to the receiver 36. In each instance the shielding means at some point adjacent the ends thereof, or near the couplers 29 and 40 is provided with grounding connections to the frame of the vehicle as generally indicated at 48 and 50. The antenna parts of course are provided with properly insulated supports.

For details of construction of the harness,reference is now made to Figs. 5, 6 and 7, which disclose the coupler units 29 and 40 as mere enlargements situated at each end of the transmission line. Inasmuch as the construction of both the coupler units may be substantially identical, a detail illustration has been made of but one, and it may be assumed that the internal construction of the unit 40 answers the details illustrated in Fig. 5, as regards the construction of the unit 30. One detailed form of construction, is that in which a nonconducting or insulating tube 52 is provided, and within which is mounted the winding 28 of the coupling unit. The tube 52 also provides adequate support for the second winding 30 of the unit and from which the end turns may be united with the leads 32 and 34 and extended substantially along the axis of the tube toward the other coupler unit, where connection may be made with the winding 42 thereof. In this instance, which illustrates a convenient and a desirable construction, the winding 28 has its end turns terminating in the leads or conductors 56 and 58, but are adapted to connect with the antenna parts as designated thereon by the legend.

The shielding 46, comprises a plurality of metallic strands 60 that are braided into substantially tubular form, to provide a metallic sheath extending throughout the length of the conductors 32 and 34, and extend over the coupler units 29 and 40 where the ends of the braided strands may be compressed about the leads joining the antenna parts and/or the receiver with the respective coupling units 29 and 40. A convenient means for compressing the sheath about the leads resides in the metal band or ring 62 which incidentally may provide the leads 48 or 50 through which the grounding connection is made, the ring being bonded to the metallic strands by solder or the like. Overlying the metallic shield, there is a sheath 64 of insulating fabric which may be braided, woven or otherwise secured, and which may be tinted or colored so as to blend in with the upholstery or interior finish of the vehicle.

A wiring harness constructed in accordance with the disclosure satisfactorily embodies the improvements set out, and provides a construction that is readily adaptable for installation in a vehicle that is in service, and makes such an installation possible without disfiguring the interior of the vehicle finish, and without disorganizing the general appearance thereof. When the antenna and transmission line are so installed, the receiving instrument is then adapted to pick up and sort out signal waves, and efficiently transmit them to the radio receiver even though the vehicle or other construction embodying the installation may be in the very near vicinity of a high powered transmission line, trolley wire or the like. In installations of the character disclosed the antenna parts being situated in spaced relation and in a plane substantially perpendicular to the noise wave front, apparently cancels out noise impulses received from the disturbing source Whether or not there is any cancellation of the noise impulses, the unit effectively impresses the signal wave received through the radiation field upon the transmission line in such manner that there will be an improvement in the ratio of signal to noise, and the ultimate result is one in which the signal wave is impressed upon the receiver unimpaired by the noise component.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a radio installation having antenna parts remotely situated with respect to a receiver, a harness adapted for coupling the antenna parts to the receiver, comprising in combination, a pair of insulating tubes, transformer windings disposed within each tube, the windings of one tube having conductors adapted for connecting with the antenna parts, and the windings of the other tube having conductors adapted for connecting to the receiver, other transformer windings disposed about the tubes and inductively coupled with the inner windings, a pair of leads joining the outer windings of one tube with the outer windings of the other tube, a fabricated sheath of metallic strands overlying the leads and the transformer windings, and means compressing the fabricated sheath about the conductors between the winding and the antenna parts and receiver respectively.

2. In a radio installation having antenna parts remotely situated with respect to a receiver, a harness adapted for coupling the antenna parts to the receiver, comprising in combination, a pair of insulating tubes, a Winding supported within each tube and having a pair of short leads for connecting a winding each with the antenna parts and the receiver, a second winding secured outside of each tube, a pair of conductors extending between and connecting the second windings into a closed conductive path, a shield element of woven metallic strands extending throughout the conductors and beyond each tube and its supported windings, a metallic ring compressing the ends of the metallic strands about the leads of each inner winding and a jacket of insulating material substantially covering the shield element.

3. An antenna installation, comprising in combination, antenna means comprising parts of l which lie in a plane substantially parallel to the wave front of the noise field, and substantially perpendicular to the Wave front of the signal field, means connecting the antenna parts in series and including a transformer winding, a second transformer winding inductively coupled to that first mentioned, and a transmission line extending between the second winding and the receiver, said transformer windings and transmission line operating to impress the signal Wave received upon the receiver unimpaired by the noise component.

HENRY C. FORBES.

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