US2624001A

US2624001A - Television antenna

Info

Publication number: US2624001A
Application number: US72974A
Authority: US
Inventors: Jr Oakley Mcdonald Woodward
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1949-01-26
Filing date: 1949-01-26
Publication date: 1952-12-30
Anticipated expiration: 1969-12-30

Description

Dec. 30, 1952 TELEVISION O. M D. WOODWARD, JR

ANTENNA Filed Jan. 26, 1949 INVENTOR bakleyzlg Woad wardfi ALL Milk A ORNEY Patented Dec. 30, 1952 S PATENT "OFFICE TELEVISION ANTENNA Oakley McDonald Woodward, J r., Princeton, N. J assignor to Radio Corporation of America, a

corporation of Delaware Application January 26, 1949, Serial No. 72,974

12 Claims.

' evision channels.

The presently assigned television channels are spread over two bands, the lower band comprising channels 2-6 lying between 54 and 88 mc. s., and the higher band comprising channels 7-13 lying between 174 and 216 mc./s. It has been found that really satisfactory reception over both bands with known antenna systems is accomplished only by employing two separate receiving antennas and complementary transmission lines. Alternately, the antenna for the higher band is connected to the transmission line for the lower band antenna for fairly satisfactory reception in some installations, though the efficiency of the system is lowered to some considerable extent because of interaction.

It is an object of the invention to provide a simple antenna system operable over a. wide frequency range.

A more specific object of the invention is to .provide'an antenna system comprising a lower band antenna and a higher band antenna to be coupled to a receiver by a'feed system and providing uniform, highly efficient results over all twelve of the presently assigned television fre 1 quency channels.

It is another object of the invention to provide an antenna system for home installations that is mechanically strong but light in weight and pleasing in appearance.

It is a further object of the invention to provide an antenna system affording optimum results over the entire band of twelve channels without any adjustment after installation is completed,

It is still another object of the invention to provide an antenna array having a bi-directional characteristic over all twelve channels.

These and other objects of the invention which will appear as the specification progresses are achieved by means of a pair of antennas arranged to prevent interaction between each other and adapted to be coupled to a receiver by means of a feed system which effectively isolates the antennas from each other and nullify the effect of one when receiving on the other.

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

Fig. 1 is an illustration of an antenna system according to the invention; and

Fig. 2 is a schematic diagram of the electrical connections of the antenna system shown in Fig. 1.

Referring to Fig. 1 there is shown a support II on which is mounted a block member I2 having rod members I3 and I4 affixed thereto normally to the axis of support I I and a further insulating mounting member l5 afiixed. to One side satisfactory results.

2 of block member I2. The members thus. .far described need not be formed exactly as shownin the figure but may be constructed in any manner suggested to one working in the art as the.configurations of these members are not: important to the invention. At the outer. ends of members I3 and I4, folded dipole elements 2| arearranged. Further details of construction and operation -of these folded dipole elements may be had by referenoe to U. S. Patent 2,283,914 issued May 26, 1942, to Philip S. Carter and assigned to the Radio Corporation of America. The

high impedance terminals

22 and 23 are electrically insulated and mechanically fixed by means of low loss dielectric insulation 24. As explained in the above mentioned U. S. patent, little or no loss will be effected at the portion of the folded diploe element opposite the terminals if it is electrically connected to a metallic support, hence rod members I3 and I 4 may be made of any conducting material desired, and preferably are in most installations. Preferably, folded dipole elements H are adjustable by means of trombone endsecti'ons 25 although a fixed construction resonant to a frequency near the center of the higher television band may be used with entirely Midway between folded dipole 2| a double V"

element comprising arms

3I, 32, 33, and 34"is fastened to mounting member I5 by means of metal plates 35-and 36. Arms 3I and 32 arranged at an angle of approximately and electrically connected to plate 35 and

arms

33 and 34, are arranged at the same angle and connected to plate 36, which plates form the terminals for the double-V element. In the preferred embodiment,

plates

35 and 35 are mechanically fastened to insulating member I5, which is in turn fastened to a metallic block IZ-in order to obtain maximum mechanical strength; however, if block I2 is made of low loss dielectric material,

plates

35 and 36 may be fastened thereto directly, eliminating any need for an additional member I5.

By means of insulating rings 49 mounted on support I I by means of clamps 4|, a transmission line 42 leading to a receiver or other transducer (not shown) is brought to the antenna system. At a suitable point along support I I transmission line 42 is electrically connected in parallel to further transmission lines 44, 48, and 49. Transmission lines 48 and 49 are equal in length and terminate at folded dipoles 2 I, while transmission line 44 terminates at

terminal plates

35 and 33 of the double-V element for a purpose later to be described. This line is folded and fastened in place on rod members 4 by any convenient means, such as rubber tape or suitable metal clamps, to prevent it from whipping in the wind. Preferably some means of protection against lightning should be provided in any antenna in stallation and the arrangement according to the invention readily lends itself to this purposeas shown in Fig. 1 wherein a lightning rod 5| is clamped to a metal support H by means of clamps .52.

Further details of the construction of the antenna system according to the invention will most conveniently appear as the operation of the system is described with reference to Fig. 2,

schematically showing the electrical connections tween" the. two; arraysis; prevented because. of the I factathatrthe folded: dipole" elements 21 are. connectedxoutofphase with each other by means of transmissionlines lt and.49.-as;can be seen more clearly in Fig. 2, where folded. dipole elements 21'- are connected by, lines at. and 49 in transposed relationship,.and the..doublev array lies in a neutral plane midway between the folded dipole array, thus. preventing extraneous side lobes from appearing at the higher frequencies.

It should-be understood that the antenna systemas expressly'described merely constitutes an example of an arrangement'according, to the in- 1;

ventionand: other arrangements will be immediately suggested to-theartisan. For example,

the-ordinary dipole may be substituted for the.

doublew dipole, aoonicaldipole antenna may be. equally well employed; or in other words any broadside antenna capable of being confined to a. neutral. zone midway between the elements of the end-fire array, but not necessarily inv line withrtheend fire elements, will serve to effectan arrangement according to the basic. principle of the. invention. Accordingly any end. fire array whichwillprovidezsuch aneutral zone will fulfill therequirements. of an arrangement according to. the invention; In addition, it should be obvious that the endfire. array may be used in the lower band and the broadside antenna on the higher-band also without departing from the invention; It should be understood that the term broadside array must be construed in this specification to include single elements such as the ordinary dipole as wellas-multi-element arrayssince the invention uniquely lends itself. to the use of both. Preferably, all. of. the transmission line seeticnshave the samecharacteristic. impedance, though it. is entirely possible touse. sections of different characteristicimpedance together with suitable transformer sections and remain within the scope of the invention. Since most commercially produced television receivers are designed. for 300 ohminput transmissionlineawhioh are. readily obtainable in quantity, it is preferable to employ 300 ohm lines throughout and thusavoiddiffioultiesin matching linesof varying characteristic impedances;

Transmission line 48 is a quarterwave long at the-center of the high frequency band (195 mc./s.

for: the presently allotted channel) and thus short circuits the terminals of the double-V arrayv at. the higher frequencies. Transmission line 44 is also a quarterwavelong atv the. higher frequencies and. thus presents an infinite impedance. (or open circuit). to the junction point C oftransmissionlines 42, 44, 48, and 4% Hence when signals on. the. higher frequency channels arereceived, only the-foldeddipole array is effective.

At the lower frequencies, however, folded dipole 2i functions as two short circuited stubs, B and B, connected in series. Transmission lines 43 and 59 are of such length as to present a high reactance at point'C. Transmission line it will have little effect on the double-V array when signals at the lower frequencies are received. Hence, when lower band signals are received, only the double-V array is effective.

The antenna system as described provides substantially figure-eight-field patterns in the same direction in. the azimuthalplane for the twelve presently allotted. televisionohannela It is also possible to. provide-a somewhat. different-directivity for the low frequency band. withrespectto the high, frequency band by varying the azimuthal position. of. one of. theantennas with respect to the other, carev being, taken thatthe broadside array is sci arranged. with. respect to the endfire array that equal and opposite voltages are induced in one by the-other.

While the invention has been described in terms of. express embodiments, it is to be understood. that obvious modifications thereof will be suggested to. thoseskilledin. the art without departing-fromthe spirit-andscope of the invention.

I claim 1. A. lei-directional antenna. system including an-element-resonant to a firstfrequency, and other elements resonant to. a. second. frequency arranged equidistantly on either. side of the. first said element, said other elementsbeing coupled to each other in phase opposition, the first said element and said other elements being electrically independent of each other, and means to connect transducer apparatus to the first said element and said other elements and maintain said electrical independence. therebetween.

2. An. antenna systemincluding an antenna resonant to a first frequency and comprising two elements intercoupled by a pair of conductors to provide an end-fire array, an antenna resonant to a second frequency and electrically equidistant from each of the elements of said first antenna whereby interaction between said antennas is prevented, a length of transmission line, a multiple, including unity, of a half wave length long at said first frequency coupled at one end to the pair of conductors of said first antenna and coupled at the midpoint thereof to said second antenna, and; means to couple transducer apparatus to the system at said one. end of said length of transmission line.

3. A bi-directibnal antenna system? including an antenna resonant to a first frequency and comprising'two elements intercoupled by transmission line means to provide an end-fire array, an antenna resonant to a second frequency and located electrically equidistant from the elements of saidfirst' antenna whereby interaction between said antennas is prevented, a length of transmission line, a multiple, including unity, of a half wave length long at said first frequency at one end to said transmission line, means of said first antenna and coupled at the midpoint thereof to said second antenna, and means to coupletransducer apparatus tothe system atsaid'one end of said-length of transmission line, said transmission line means intercoupling said two elements having a length at which a high reactan'ce is presented at said one end of said length of transmission line.

4. An.- antemia system including an antenna resonant to a first frequency, said antenna comprising two elements and a transmission line intercoupled to provide an end-fire array, an antenna resonant to a second frequency and located between the elements of said first antenna at a point electrically equidistant from each of said elements whereby interaction between said antennas is prevented, a further transmission line a half wave length long at said first frequency coupled at one end to the midpoint of said first transmission line and coupled at the midpoint thereof to said second antenna, and means to couple transducer apparatus to the system at said one end of said further transmission line, said first transmission line having a high reactance at the midpoint thereof at said first frequency.

5. An antenna system including dipole elements resonant to a first frequency, other dipole elements resonant to a second frequency arranged equidistantly on either side of the first said dipole elements, said other dipole elements being coupled to each other in phase opposition and coupled to the first said dipole elements in phase opposition at said second fre uency, and means effectively to short circuit the first said dipole elements at said second frequency.

6. An antenna system including dipole elements resonant to a first frequency, other dipole elements resonant to a second frequency arranged equidistantly on either side of the first said dipole elements, transmission line elements coupled at one end to said other dipole elements and coupled to each other at the other ends to couple said other dipole elements in phase opposition, and transmission line sections coupled to the first said di ole elements, one of said transmission line sections being coupled to the junction of said transmission line elements, said transmission line elements having lengths at which a high reactance at said second frequency is presented at said function and said transmission line sections having lengths at which the first said dipole elements are short circuited at said second frequency.

7. An antenna system including a pair of folded dipoles resonant to a first frequency and arranged parallel to each other and spaced apart, a dipole antenna resonant to a second frequency and havin two arms each comprising conductor elements diverging from the center thereof, said elements being arranged parallel to said folded dipoles and located at a point intermediate said folded dipoles. a length of transmission line coupling said folded dipoles out of phase with each other, a transmission line having a length of onequarter wave length at said first frequency coupling said dipole antenna to the midpoint of the first said transmission line, and means to couple said midpoint to transducer apparatus.

8. An antenna system including a pair of folded dipoles resonant to a given frequency and arranged parallel to each other and spaced apart, a dipole antenna resonant to a frequency lower than said given frequency and having two arms each comprising V-shaped conductor elements, said elements being arranged parallel to and located at a point intermediate said folded dipoles, a length of transmission line coupling said folded dipoles out of phase with each other, a transmission line having a length of one-half wave length at said given frequency coupled to the midpoint of said length of transmission line, said dipole antenna being connected to the midpoint of said halfwave line, and means to couple transducer apparatus to said system at the junction of said length of transmission line and said halfwave line.

9. An antenna system including a pair of folded dipoles resonant to a given frequency and arranged parallel to each other and spaced apart, a dipole antenna resonant to a frequency different from said given frequency and having two arms each comprising V-shaped conductor elements, said elements being arranged parallel to and located at a point intermediate said folded dipoles, a length of transmission line coupling said folded dipoles out of phase with each other, a transmission line having a length of one-half wave length at said given frequency coupled to the midpoint of said length of transmission line, said dipole antenna being connected to the midpoint of said halfwave line, and means to couple transducer apparatus to said system at the junction of said length of transmission line and said halfwave line.

10. An antenna system including two separate antennas, one of said antennas being resonant to a given frequency and comprising two dipole elements arranged substantially parallel to each other and coupled in phase opposition, and the other antenna being resonant to a different frequency and being arranged substantially in between said dipole elements and electrically equidistant from each of said two dipole elements thereby effectively to neutralize electrical coupling between said antennas, and means to couple a transducer to both of said antennas while maintaining said antennas operable individually at each of said frequencies.

11. An antenna system including an end-fire array comprising an even number of elements and resonant at a given frequency and a dipole antenna array resonant to a different frequency and arranged substantially in between and electrically equidistant from the outer most elements of said end-fire array, and means to couple a transducer to both of said arrays while maintaining said arrays operable independently of each other.

12. An antenna system including two separate antennas, one of said antennas comprising two folded dipoles resonant at a given frequency and arranged substantially parallel to each other and coupled in phase opposition, and the other antenna comprising a dipole element resonant to a different frequency and located substantially in between and electrically equidistantly between said two folded dipoles, thereby effectively to neutralize electrical coupling between said antennas, and means to couple a transducer to both of said antennas while effectively electrically isolating one antenna from the other OAKLEY MCDONALD WOODWARD, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,064,774 Wheeler Dec. 15, 1936 2,413,951 Carter Jan. 7, 1947 2,425,887 Lindenblad Aug. 19, 1947 FOREIGN PATENTS Number Country Date 532,955 Great Britain Feb. 4, 1941 OTHER REFERENCES Radios Master, 12th ed., page 40, May 9, 1947.