US2640931A - Directional antenna - Google Patents

Description

June 2, 1953 J, 1 ROOT 2,640,931

DIRECTIONAL ANTENNA 'Filed May 5, 1950 z5 Z6-1"; ci. E.

Z5 Z? Z3 Patented June 2, 1953 UNITED STATES PATENT OFFICE DIRECTIONAL ANTENNA John J. Root, New York, N. Y.

Application May 5, 1950, Serial No. 160,349

3 Claims.

This invention relates to high frequency antennas for use in television and frequency modulation receivers.

To insure maximum efliciency of reception, it is essential that television receivers be equipped with a directive antenna which is of a size adapted to resonate approximately within the frequency range of reception. When a television receiver is located at some distance from the transmitter, it is usually necessary to employ an elaborate antenna having elements of adequate size to resonate at desired frequencies. At locations closer to the transmitter, simplified antennas may be used and it is seldom that an antenna can be dispensed with entirely.

In large cities, Where television transmitters are located, the correspondingly large number of television receivers in a substantial number of instances are not adapted to be provided with `the elaborate types of antenna heretofore known in the art. The location of large numbers of recelvers in apartment houses makes it diflicult to install outdoor antennas of the complicated type necessary to insure adequate reception. Furthermore, such antennas involve substantial costs, both in their manufacture and in their installation.

Antennas have been installed Within the cabinet of the television receiver, but such antennas have been found to be inadequate in most instances. While it would be desirable to orient such antennas in order to improve reception, the movement of the cabinet to effect such orientation of the antenna is not feasible since the screen might be moved out of its normal viewing position.

Accordingly, an object of this invention is to provide an improved antenna for television reception which does not have to be mechanically rotated in order to obtain proper orientation,

4such orientation being obtained electrically by improved condenser means interconnecting the antenna elements.

Another object of this invention is to provide an antenna including crossed dipoles which are bridged by means of a slidable type variable condenser for effecting electrical orientation of the antenna in accordance with selected positions of a slidable element of the condenser.

Still another object of this invention is to provide a television antenna of the crossed dipole type in combination with a variable condenser for eectively rotating the antenna in space, the condenser forming direct mounting means for the dipoles.

(Cl. Z50-33.51)

A further object of this invention is to provide for use as a bridging means in an antenna of the crossed -dipole type, a simple form of capacitor, which is inexpensive to manufacture, is easily operated and is eiiicient to a high degree in use.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

In the accompanying drawing, in which is shown an illustrative embodiment of the invention,

Fig. l is a perspective View of the upper portion of a television receiver cabinet, indicated in dotdash lines and equipped with a built-in antenna embodying the invention.

Fig. 2 is a top plan View of the antenna.

Fig. 3 is an enlarged top plan view showing details of the condenser portion of the antenna, with parts thereof removed.

Fig. 4 is a sectional view taken on the line 4--4 0f Fig. 3.

Fig. 5 is a sectional View taken on the line 5-5 of Fig. 3, and

Fig. 6 is a perspective view of the slidable member of the condenser, with a part thereof broken away.

The top of the television receiver cabinet is generally indicated at A, the antenna embodying the invention being generally indicated at I0, and illustrated as suitably mounted on the underside thereof.

The antenna lil comprises dipole sections II and I2 forming one dipole and dipole sections I3 and lil forming another dipole. As shown in Fig. 2, the dipoles are located in crossed relationship so that they are substantially in perpendicular relation to each other. The dipole sections II and I3 are bridged or interconnected at their outer ends by a member I5 which may be integral with sections II and I3. It has been found that such bridging increases the impedance match between the antenna and receiver input and further increases gain at low frequencies. The inner ends of sections II and I3 include angular terminal portions I6 and I1, respectively which are in alignment with each other, the opposite ends thereof being slightly spaced from each other. The dipole sections I2 and I4 are interconnected at their outer ends by a conductive member I8 which is substantially parallel to member I5. The inner ends of sections I2 and I4 are interconnected by a conductive member I9 which may be integral therewith and is substantially parallel to mem-ber I8. A conductive member 20 extends from the midpoint of member I8 -to the midpoint of member I9, interconnecting members la and I9. The member 2li has been found to be effective in substantially increasing the antenna gain. The dipole sections and their interconnecting members may take the form of wire conductors of circular cross section and of suitable stiiness.

Means is provided for suitably arranging the dipoles relative to each other and to maintain the same .in the desired relationship, Such means further serves to bridge the dipoles and to allow for adjusted electrical orientation of the antenna. constituted by the dipoles. To this end,

a variable condenser, generally designated as C, l

is provided. The same comprises a pair of simil-ar rectangularly-shaped sheets 2| and 22 ofY suitable stiffness, such as vulcanized fiber or the'- like, which are disposed in overlying relation to each other. Mounted on the upper face' of the sheet 22 are a pair of similar stator plates 23 and 24 'of conductive material arranged lin side-by- Sicle, spaced relation to each other and which form the fixed conductor elements of the condenser C. T'he terminal portions I6 and Il of dipole sections and I3 are arranged in contacting 'relation with plates 23 and 24, respectively, as Shown in Fig. 3.

v The member I9 of dipole sections I2 and I4 is also arranged on sheet 22, being located in spaced relation to plates 23 and 24. A thin sheet of 'dielectric material such as fish paper or the like 'isdisposed over the upper faces of stator plates -2'3 'and '24. A 'conductive plate 2G isv slidably arranged for capacitive relation to stator plates 23 and 24 to form the movable element of condenser C. The plate 23 arranged on the underside of anelongated slider strip .27 of suitable stiiness. such as cardboard. The plate 25 includes a ter- 'minal lug 28 struck up from the body of the plate and projecting upwardly through an opening in .slider strip 27. The supporting sheet 2| is formed with an elongated, rectangular slot 25 to accommodate terminal 22, upon slidablemovement of slider 21. The movement of strip 21 is guided by a. pair of spacer strips and 3| located over the dipole end portions IB and Il and dipole .member I9, respectively and .having their upper faces vcontacting the inner surface of sheet 2|.

The strips 30 and 3| define therebetween. a track for movement of slider 21, the limits of movementin opposite directions being established by contact of lug 28 asit contacts the opposite ends of slot 2.9.

Thesheets 2| `and 22, aswell as the plates 23, 2-4 and 26, and the vdipole sections are retained in their relative position by means of staples 32 passing through the superposed sheets as indicated. It understood that fastening means other than staples may be used for securing the sheets and associated condenser elements in their `desired relationship.

'The strip "21, which is of such length that it 'may project beyond sheets 2| and 22, is formed on-itsfout'er end'with an opening 33 for receiving 'thevinturned end '34 atthe inner end of manually operablelrod 35. vend a reversely turned portion 36 which is Therod includes at its outer 28 on plate 26 while wire 39 is soldered to member 20.

As sho-wn in Fig. 5, the plate 26 on slider strip 21 is of such dimension as to substantially overlie and cover stator plate 24, when the strip is in its retracted position. Similarly, when strip is moved by means of knob 3l to its extreme forward position, plate 26 will substantially cover and overlie stator plate 23. Thus, in one extreme position of slider 27, the dipole sections: and I2 are bridged capacitatively by plate 26 and plate 23, while in the: other and opposite extreme position, dipole sections I3 and 4 are bridged capacitatively by plate 2S and plate 24. Accordingly, the antenna I0 may be electrically oriented without mechanical movement to opposite direc--Y tions.

Upon movement of the slider 2l to positions intermediate of the extreme positions thereof, plate 26 will be placed in overlapping relationship to stator plates 23 and 24, thus electrically orienting theantenna .to adjusted directions intermediate the extreme opposite directions previously referred to.

Such condenser C, while extremely simple in construction, is effective in providing for electrical orientation of the antenna, -since the directional dipoles as arranged accommodate signals received from any direction. The signals are then selected through slidable movement of the variable condenser C so as to effectively orient the antenna in space. The conductor members |5 and i8 which connect the free ends of the dipole sections appear to have an inductive effect which compensates for the shortness of the dipoles.

While the condenser C eiectively functions as means for electrically rotating or crienting the dipoles, the condenser in addition .probably acts' to properly phase incoming signals, although such incoming 'signals may reach the antenna out of phase. In addition, the condenser appears to provide a tuning action which` increase gain.

It is understood that the condenser elements 23, 24 and 26 may take the form of electrically conductive coatingsapplied directly tothe appropriate dielectric members.

The invention disclosed herein is of the .type shown in applicants co-pending application Serial No. 123,022, led October 2,2, 1949, Patent No. 2,552,816, granted May 15, 1951, and .constitutes an improvement thereover.

It is apparent that the dipoles! herein disclosed vare eiectively'mounted in their desiredrelationship by being directly secured to the variable condenser C wh'ich is eiective to rotate the vdipoles in space electrically, thus providingan integral structure which may be mounted as a unit onthe cabinet of the television receiver.

The natureI and construction of the condenser C, as well as themanner of its. association `with the dipoles, provides a highlyeconomical antenna.- system which is effective in yattaining-the objects 0f the invention as hereinabove described.

1. A television vantenna system vcomprising a pair of dipoles crossed so as to be effective in substantially mutually perpendicular directions, variable condenser means comprisingtwostator plates respectively connected to a pairof inner ends of said dipoles and a slidable plate inscapacitative relationship Vto said stator plates Afor electrically rotating the directionalcharacteristics of said dipoles, 4a first bridging -elementbetween the two adjacent outer ends of said'fdipoles, a second bridging element between the other pair of inner ends of said dipoles and a connecting element between said iirst and second bridging elements and substantially perpendicular thereto.

2, A variable condenser for use with television antennas comprising a pair of superposed supporting sheets, a pair of conductive condenser elements disposed in end-to-end, spaced relation between said sheets, a dielectric member disposed over said condenser elements, a slidable supporting member disposed between said sheets, a conductive condenser element mounted on said slidable member for capacitative relation to said pair of condenser elements, a lug on saidslidable member, one of said sheets being formed with a longitudinal slot within which said lug rides for `guiding the movement of said slidable member,

substantially mutually perpendicular directions,

6 tact with one of the terminal ends of said iirst mentioned dipole sections, a slidable condenser element arranged for movement with respect to said pair of condenser elements and in capacitive relation thereto, the inner ends of said second mentioned dipole sections being connected and received between said supporting members and in spaced relation to said condenser elements, means for securing said supporting sheets together whereby to retain said condenser elements and said dipoles in proper relation to each other, an output terminal on said slidable condenser element and an output terminal on said second mentioned dipole section, the dipoles being adapted to be effectively rotated in space by movement of said slidable condenser elementV relative to said pair of condenser elements.

JOHN J. ROOT.

454,845 Great Britain Oct. 5, 1936

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