US2664507A - Simplified electrically steerable antenna - Google Patents

Description

Dec. 29, 1953 MURAL 2,664,507

SIMPLIFIED ELECTRICALLY STEERABLE ANTENNA Filed Feb. 1, 1950 ATTO R N EY Patented Dec. 29, 1953 UNTED ST SIIHPLIFIED ELECTRICALLY STEERABLE ANTENNA Frank Mural, Drexel Hill, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application February 1, 1950, Serial No. 141,617

2 Claims.

The invention relates to antennas and it particularly pertains to antennas for TV receivers which can be oriented easily for optimum results and particularly for minimizing ghost images in television reception.

It has been suggested for the latter purpose that antenna arrays of the conventional type be made mechanically rotatable, but such an arrangement is too complicated and expensive for widespread usage. Since a fixed antenna array does not require nearly the mechanical strength of a rotatable array, a means of obtaining a steerable antenna field pattern with fixed antenna elements is extremely desirable, but electrically steerable antennas known to the prior art are in general large complex multi-element arrangements entirely unsuited for use with television receivers used in the average home.

It is an object of the invention to provide an improved electrically steerable antenna of extremely simplified construction, having substantially fixed components, for television receiver installations such asare encountered in the average home.

It is another object of the invention to provide a highly simplified electrically steerable antenna capable of installation within the housing of a receiver or auxiliary cabinet structure and using components readily available for other purposes.

It is a more specific object of the invention to provide a plurality of angularly arranged antenna elements, to provide optimum performance in discreetly fixed directions together with means providing continuous variation of the directivity of the overall antenna pattern.

These and other objects of the invention which will appear as the specification progresses are attained by means of an antenna system comprising a plurality of antenna elements oriented in different directions from each other and interconnected by transmission line means to a variable resistance element, the movable contacts of which are connected in turn to a radio frequency transducer, for example, a television receiver.

Several embodiments of the invention will be described with reference to the accompanying drawing forming a part of the specification and in which:

Fig. l is an arrangement of a steerable wideband antenna according to the invention;

Fig. 2 is an illustration of an alternate embodiment of the antenna system according to the invention; and

Figs. 3 and 4 are illustrations of specially constructed transmission lines suitable for incorpo- 2 ration in arrangements according to the invention.

Referring to Fig. 1, there is shown an antenna arrangement which comprises four conductors, l2-l5, arranged in radial relationship to each other at a central point, and connected in pairs iZ-l3 and I l-l5 to conductors 22-23 and 26-25 respectively, which conductors constitute transmission lines over which radio frequency energy induced in conductors I2-l 5 is translated to a variable resistor device 2'1, having a resistance element 29, and two simultaneously rotatable arms 3I-32 to which transducer apparatus (not shown) may be connected by means of a conventional transmission line 35. The resistance element may consist of a 360 carbon potentiometer with four symmetrically spaced taps to which conductors 22-25 are connected and two insulated opposing arms iii-32, or two ganged center tapped potentiometers connected in equivalent fashion, the former being shown rather schematically for clarity of description. It will be necessary to provide terminal blocks for the transmission lines at both ends to prevent variation in the relative lengths of the transmission line wires on installation.

Alternatively, the antenna portion of the system may consist of crossed dipoles (at or folded dipoles, or, if the desired direction of reception is limited to within 90, dipoles with reflectors. The transmission line should be constructed for the required impedance, low loss and take a form suitable to low-cost manufacture.

An example of alternate construction is shown in Fig. 2, wherein conductors l2-l5 have been replaced with triangular metal sheets 52-55 in order to provide a wider frequency band response. Alternatively, wires arranged to define the edges of each sheet would serve as well or an arrangement such as described in U. S. Patent 2,175,253 issued October 10, 1939 to P. S. Carter would also be suitable. Two ganged centertapped potentiometers 58 and 59 are connected together to effect a resistance ring as in the embodiment shown in Fig. 1. Opposite ends of potentiometers 58 and 59 are connected to leads 22 and 23 and the center taps of potentiometers 58 and '59 are connected to leads 24, 25 respectively. The arms El, 62 are connected to a trans ducer by means of a length of transmission line 35 as before. Thus when the arms 6!, 62 are at the end of travel substantially all of the signal u d in d poles 52-53 is directed to the transducer and when they are at the center of travel substantially all of the signal from dipoles 54-55 arranged to be controlled from thefrorit-panel ot the receiver as will be obvious to anyone familiarwith the art. N In most installations it will be desirableto} use standard 300 ohm transmission lines so that resistor element 21 will preierablyhayea lie-o sistance of 300 ohms between ta e-enepdteritiometer 58 and 59 will have a resistancerof, 699 ohms end-to-end. Two twin-conductor trans- Vmis sion lines can beusedfor conductors 22 23 and 24-25, although a four conductor trans;- mission line of the typer having across section e shown taste aiee severerebv eue eatenm A .qfm qf te li t r ime. 'ri'yt smission; ne arrangement is awn crosssection Fig. In both the arrangements of g g and 4, the maxim m. field between onduetors, 22-23 and 24-25 is substantially in are not dielectric material. The'arrariget. of Fig.4 can be. made as sturdy as that of Fig. 3 by juaieioueaimensiemng of the webbing while at the seme-tiine being much easier to eat rude in'menu ee uring. Thetaperirig of the webbing provides the necessary strength and rigidity without requiring. the use of an excessive em 'unt of insulating material. Thev Xf shapjed crosssectiori of the transmission line arrangereenter Page is much lesssusceptible to delet'rio'us eficts of dust andmoisture'collecting on the surface of the insulation since the exjtr'eiiee matter is not in the region at meni d- 'cdiivehtibii'el tuning and/or impedance matchii 'ef. lii t 35" tween the ante" {and the transmission line.

While the i'n ention has been described in tjet'me of. specific embodiments, it is to be understood. that. other arrangements and modificatioi'iswill be suggested to "one skilled in the art witheytgepa tmg from the spirit and. scope or r the invention. n

invention claimed is: *1. A steerable antenna system having a-pair of colinear energy receiving elements each havof course, be" interposed being two centrally located electric terminals for connecting to a transmission line, a four terminal resistive mesh network, and a transmission line comprising an elongated dielectric member of substantially cruxiform cross sectionand two pairs of conductors en be dded in said dielectric member, each; conductor, being located. in an arm of the cruxiform structure, the con-- ductors of each pair of said conductors being connected individually at one end to said receivirig elements. and at the other end to alternate terminals of said resistive mesh network. 2. A steerable; antenna system comprising two center-fed dipole antennas constituted by pairs of triangular conductive surface elements arranged in cruxiform relationship in a substantiallysingle plane, a pair of potentiometers having fixed end terminals, intermediate fixed taps and variable contacts: ganged to be adjusted simultaneously, means to connect the end terminals of said potentiometers effectively to form a resistancering, means to connect the adjacent ends of a pair of oppositely disposed condiictive surface members individually to the oppositely disposedintercoupled end terminals, means. to connectthe adjacent ends of the remaining pair of said conductive surface elements to said intermediate fixed taps said means comprising a pair of two-conductor transmission 'lines having a common webbing of insulating material of 'c'rn ziffo'rm cross section maintaining the conductors of said line in fixed spaced relationship, and means to connect radio transducer apparatusto said variable contacts of said potentiometer. FRANK MURAL References Cited in the file. of thispatent UNITED STATES 15ATENTS REFERENCES Quadrature. Phasing 'rv Receiving. Antenna, vpage 80 and page. 8,6,v Radio and TelevisiorLRetailing, November 1949..

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