US2258406A

US2258406A - Wide band antenna

Info

Publication number: US2258406A
Application number: US202460A
Authority: US
Inventors: Philip S Carter
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1938-04-16
Filing date: 1938-04-16
Publication date: 1941-10-07
Anticipated expiration: 1958-10-07
Also published as: GB527926A

Description

Oct. 7, 1941. p. s. CARTER 2,258,406

WIDE BAND ANTENNA Filed Apiil 16, 1938 2 Sheets-Sheet 1 INVENTORQ P/-/ IP 5. CARTER 06f. 7 1941. I s CARTER 2,258,406

WIDE BAND ANTENNA Filed April 16, 1938 2 Sheets-Sheet 2 I NV EN TOR.

v 5%IP 6. CARtER BY may TORNEY Patented Oct. 7, 1941 Philip s. Carter; Port Jefferson, N. Y., assignor t 7 Radio Corporation of America; a corporation of V Delaware A plication Aprilll G, 1938, Serial No. 202,460

Claims. (01; 2511- -33) t The present inventionrelates to antennas and, more particularly, to, antennas for: use with Wide band television reception and transmission.

The primary object of the present invention is to provideI an efiicient television antenna for transmission or reception of horizontally polarized waves which may be easily and simply erected. t t Another object is to provide a television antenna for transmission or reception of horizontally polarized waves which is substantially nondirectional. V t

s till another object of the present invention is to provide a simple broad band antenna which may be directly connected to a transmission line. The most commontype of antenna used for transmission and reception of horizontally polarized waves is a horizontal half wave dipole. The radiation pattern for this typ of antenna is a figure of 8 in the horizontal plane, the radia-' tion being zero in directions corresponding to the axis of theantenna, This type oiantenna requires the use of an auxiliary circuit when its impedance is matched to a transmission line.

The present invention overcomes the above mentioned objectionable radiation and frequency band characteristics while still maintaining the simplicity of the commonly used half wave dipole.

Brieflyymy invention consists of an antenna comprising two conductorarms forming an angle oi SQdegrees with each other, having a transmission line connected to theirapex, and supported at their non-adjacent ends by means of insulators connected :to any suitable supports. The conductors may be either a quarter or a half wave in length and they may each be a single wire or each comprise. a plurality of parallel wires connected in series. If a plurality of wires are used the wires are very closely spaced. perhaps a one-hundredth of a wavelength apart. The radiation pattern of such an antenna in the plane, of the conductors does not appreciably depart from a circle, in the case, of an antenna having quarter wave length arms the minimum field strength being about 71 percent of that of themaximum so thati for practical purposes it should be useful for reception in any direction, In the case of an antenna having half. wave length arms the minimum is somewhat smaller. On th other hand, the impedance of such an antenna is somewhat higher reducing difficulties in matching the antenna to a transmission line.

A better understanding of the invention is to; be had by referring to the following detailed deprises, as shown in this figure, two conductors A andB, lying in a substantially horizontal plane, each a quarter of a Wave in length and forming an angle of 90 degrees with each other. At their apex a transmission line TL is connected. The non-adjacent ends of conductors A and B are supported by means of insulators I which are connected to any convenient supporting struc-' ture (not shown). If it is desired to connect the antenna to a two wire transmission line having a somewhat higher impedance than that usable with the embodiment shown in Figurel, the modification shown in Figure 2 may be used. By the scheme shown in this figure the impedance of the antenna may be transformed to a valuefour times that of a simple two-Wired V. In this modificationconductors A, A and B, B are very closely spaced from one another, perhaps a distance of one one-hundredth of a'wave length and are electrically connected at. their ends. The currentsfiowing in the two 6011-. ductorsfwill be in the same direction in space, although in opposite directions withinthe antenna circuit due tophase reversal at the ends. Consequently, the arrangement will be almost identical in its radiation characteristic with that of the single wire antenna shown in Figure 1. However, as previously pointed out, the re sistance will be four times that of the simple two wire v.

,In the. modification shown in Figure 2 it has been assumed that the conductors are of the same diameter. This does not have to be the case, however, andif desired the conductors may have different diameters, particularly in cases where it is desired to depart from an even transformation ratio. By making the. diameters of the 'two. wires A, A, B, B unequal, as shown in Figure. 3, almost any desired. transformation ratio may be obtained.

. When conductors of different diameters are employed in the antenna system it will be found that. the. conductor of larger diameter will carry the larger current. i The difference in the amount of current carried by the conductors of difierent diameters results in a different transformation ratio from the case where theconductors are of the same diameter. The reason the larger diameter conductor carries a greater current than the smaller diameter conductor in the antenna system is due to the fact that the larger diameter conductor has less series reactance for unit of length than the smaller diameter conductor. Obviously, if desired, conductors A and Blmay be made larger in diameter than conductors A, B. The eifect of this change is to make the transformation ratio less than that of a similar antenna system where the conductors are of the same diameter.

Figure 4 illustrate approximately the radiation pattern obtained with the embodiments of my invention shown in Figures 1, 2 and 3 wherein the arms are each a quarter wave in length.

Figure 5 illustrates a further modification of my invention wherein the conductors A and B are each a half wave in length. Otherwise, this figure is exactly the same as in Figure 1.

With the antenna constructed in this manner there is more variation in field strength with direction than with the first type but this modification has a higher radiation resistance which is an advantage in matching the antenna to the usual type of transmission line.

As shown in Figure 6, it is also possible to obtain different input impedances with the antenna having half wave length arms by adding a second pairof conductors ,A, B to the system. These conductors are arranged inthe same way as de-' scribed for Figure 2. However, in this embodimerit the conductors A, B' must not be connected inthe center, for if this'were done the currents in the two conductors-would be equal and opp site and the radiation resistance of the system would be negligibly small. p

Figure '7 shows the approximate radiation patinto effect, my invention'is by no means limited 3. In an antenna system comprising a pair of separated conductors having a length equal to a quarter of the length of the operating wave and forming an angle of 90 degrees with each other and a, transmission line directly connected to the adjacent ends of said pair of conductors for energizing said conductors in phase opposition, means for multiplying the impedance of said antenna to a valu equal to that of said transmislength as said first pair arranged parallel to said first pair of conductors and closely spaced therefrom, the adjacent ends of said second pair of tern obtained using the antennas shown in Figto'the particular arrangements shown and described and modificationsmay bemade' without departing from the scope and spirit of the invention. v 1 I claim:

' 1;In an antenna system comprising a pairof separated onductors forming an angle of 90 degrees with each other and means for energizing said conductors in an opposing phase relationship comprising a transmission'line' directly connected to the adjacent ends of said pair of conductors, means for matching the impedance-0f said an-" tenna to said transmission line over a wide band of frequencies comprising a second pairofcone ductors of the sam length as said first pair arranged parallel to said first pair of conductors and closely spaced therefrom; said second pair of conductors being connected to said first pair atpoints removed from said adjacent ends, whereby there is minimized the existence of refiected waves on said transmission line which might disturb the radiation antenna conductors. Y 7

I 2. In an antenna system comprising a pair of separated conductors having a length equal to characteristics of said a multiple, including unity, of a quarter of *the length'of the operating wave'and forming' a-horizontal angle of 90 degrees with each other, and atransmission line directly connected to the adjacent ends of said pair of conductors for energiz ing lsaid conductors in phase opposition, means for matching the impedance of said antenna to said'transmissionlline over 'a wide band of ire-'- quencies comprising a second pair of conductors arranged parallel to said first pair of conductors and closely spaced therefrom, said second pair of conductors being connected tosaid first, pair at, points removed from said adjacent ends, whereby there is minimized the existence of refiected waves on said transmission line which might disturb the radiation characteristicsof said antenna conductors. v

conductors being connected together, said second pair of conductors being connected to said first pair at points removed from said adjacent ends and said second pair of conductors havinga different diameter than said first pair whereby said impedance multiplication is an odd value, whereby there is minimized the existence of -re'- fiected waves on said transmission line which might disturb the radiation characteristics of said antenna conductors. J

4-. ;In an antenna system comprising a pair of separated;conductors having a length equal to a quarter of the length of the operating wave and forming a horizontal angle of 90 degrees with each otheran'd a transmission line directly conn'ectedto the'adjacent'ends of said pair of conductdrs for energizing said conductors in phase opposition; means for multiplying theim-pedance of said antenna to a valueequal to that of said transmission-line whereby reflection of energy into said transmission line is prevented compris inga second pair ofconductors of the same length as said first pair arranged parallel to-said first pairof conductors and-spaced therefrom adis= tance of the order of 1/100 of the operating wave length,"the adjacent ends of said second pair of conductors being-connected together, said second pa'ino-fconductors being connected to said first pairat points removed from said adjacent ends and said second pairof conductors being ofthe same diameter as said first pair of conductors;

i1 "5;"In an antenna system comprising-a pair of separated conductors having alength equal to half the'length of the operatingwave and forming 'a horizontal angle of 90"degrees with each other; and atransmission line directly connected to the adjacent ends of saidpair of conductors for energizing said conductors in phase opposition, means for matching the impedance of said antenna to the-impedance of said transmission line. over a wide band-of frequencies whereby reflection is preverte'd comprising a second pair of conductors of the same length as said first pair arranged parallel to said first pair of conductors andclosely spaced therefrom, said second pairof conductors being connected'to said first pairflat points removed from said adjacent ends, said second pair of conductors having a different diameter than said first pairlwhereby the impedance change due to saidsecond pair is an odd multiple, whereby there is minimized the a existence of reflected waves onsaid transmission line which might disturbthe radiation charac-.

PHILIP s. CARTER.