US2224898A - Wide band short wave antenna - Google Patents

Description

Dec. 17, s CARTER 2224,898

' WIDE BAND SHORT WAVE ANTENNA Filed Feb. 5, 1958 TRANSMITTER o2 RECEIVER I NV EN TOR.

PH? 5. CARTER BY ATTORNEY.

Patented Dec. 17, 1940 PATENTVOFFICE.

2,224,898 WIDE BAND snorr'r WAVE ANTENNA .PhiliplS. Carter, Port'Jefferson, N. Y.,, assignorto Radio Corporation of America, a corporation of Delaware Application February 5, 1938, Serial No.1'sas21.

11 Claims.

The present invention relates to a short wave antenna system which will-present negligible reactanceand practically constant reactance at its terminals over a wide frequency range, such as may be used in television transmission or reception. More particularly, the invention relates to antennas having, generally, conical surfaces of revolution of the general type described in my copending applications, Serial Nos. 147,817, filed June 12, 1937, now Patent No. 2,175,252, issued October 10, 1939; 190,939, filed February 17, 1938, now Patent No. 2,175,254, issued October 10, 1939, and 187,594, filed January 29, 1938.

As mentioned in my Patent No. 2,175,252, supra, I have found that antennas within a certain range of lengths, having conical surfaces of revolution provide a substantially pure resistance of constant magnitude 'over a wide range of frequencies, in view of which they are especially adaptable for use in the transmission and reception of television signals.

A primary object of my invention is to provide a short wave, non-directive antenna having a wide frequency band characteristic, which radiates a horizontally polarized wave substantially uniformly in the horizontal plane.

' A secondary object of my invention is to provide a wide band, horizontally polarized, short wave, non-directive antenna comprised of a plurality of conical surfaces of revolution angularly disposed with respect to one another.

Other objects, features and advantages will appear from the following description, which is accompanied by a'drawing, wherein:

Fig. 1 illustrates, by way of example only and in diagrammatic manner, one embodiment of the invention; 7

Fig. 1a, illustrates the radiation pattern of Fig. 1 in a horizontal plane;

Figs. 2 and 3 illustrate, diagrammatically, other embodiments of the present invention; and

Fig. 4 illustrates, by way of example only, one type of antenna array for obtaining concentration of energy in the vertical plane.

Referring to Fig. 1 in more detail, there is shown an antenna system comprising two conductive radiating structures- 1 and 2, which are in the form of conical'surfaces of revolution. Cones l and 2 each have a length of the order of 0.36 wavelength at the mid-bandfrequency, as measured along the surface of the cone from apex to base, and may'consist'of a metallic sheet or a plurality of wires regularly distributed around and lying in the conical surface, in the manner described more in detail in my copending applications supra. By the term order of 0.36 wavelength is meant a range of lengths 40% above and below 0.36 wavelength, as described in my copending application Serial No. 187,594, filed January 29, 1938. The conical surfaces are dis- 5 posed with their axes in ahorizontal plane making an. angle of with respect to each other, as shown, and have their apices connected to a suitable transmission line feeder TL extending to transmitting or receiving apparatus 3, here shown conventionally in box form. Since the structures l and 2 are connected to opposite sides of the transmission line TL, these structures will be fed-inphase opposition relative to each other.

The angle of revolution of each of the cones 15 i and 2 is made to beef such value that the impedance of the antenna at the terminals thereof, here the apices, will match the impedance of the transmissionline TL without the need of an auxiliary impedance matching circuit. The angles of revolution of both cones will of course be the same and should follow the laws set forth in my copending application Serial No. 187,594, filed January 29, 1938.

The system of Fig. 1, I have found, will give a substantially circular radiation pattern like that illustrated in'Fig. 1a. An inspection of Fig. 1a shows that the'radiati'on is substantially uniform in the horizontal plane and the field strength does not vary more than substantially 15% plus or 3 minus from the average around the circle.

Although the antenna of Fig. 1 is useful'both for transmitting and receiving purposes, it provides a particularly simple type of antenna which is very useful in receiving systems where a wide frequency band characteristic is desired. This is because, under usual conditions, the receiver itself does not match the transmission line leading to the antenna, Whereas, by means of the present invention, the antenna is made to match the transmissionline without the use of an auxiliary matching circuit, and consequently the multiple images which would otherwise occur, due to reflected impulses between the antenna and the receiver, are hereby eliminated. Tomore fully understand this reasoning, it should be understood that ina receiver, under ordinary circumstances, there is no impedance rnatch between the antenna and the transmission line, and con sequently reflections occur at the junction of the antenna and the transmission line and also at the junction of the transmission line and the receiver; both of which together produce undesirable multiple images. By means of the antenna structure of the present invention, however, the

10 has been shown to be of the open two-wire type,

it should be understood, of course, that if desired each wire may be in the form of a concentric transmission line.

B, in the form of conical surfaces of revolution,

Whose axes are disposed at angles of 120 with respect to one another. All of the cones 4, and 6 are energized in common from a concentric transmission line TL over concentricline conanother. Connections I, 8 and 9 differ from one another in length by'one-third of a wavelength at the mid-band frequency, in order to provide a phase difference of 120 in the energy fed to each cone with respect to the energy in the adjacent cone. Conical surfaces of revolution 4, 5 and 6 have their axes in the same horizontal plane and are preferably located above ground or any conducting planar surface, such as a roof, at a distance of one-half wavelength or multiple thereof at the mid-band frequency, in order to cancel vertical radiation. I

Fig. 3 is a further modification showing two pairs of conical radiating elements II, II and I2, I2 in the horizontal plane disposed at 90 with respect to one another and so energized at their apic es that the energy in one pair of cones leads or lags by 90 the phase of the energy in the other pair of cones. To achieve this result, one 40 pair of cones, for example I2, I2, is fed from transmission line TL over a connection I3, while the other pair of cones II, II' is fed from the same transmission line TL over a connection I4 which differs in length from the connection I3 45 by one-quarter wave-length or an odd multiple thereof at the mid-band frequency. Transmission line TL may be either an ordinary two-wire open line or a concentric conductor line. In Fig. 3

the angle of revolution of each pair of cones'is 0 made to be of such value that the impedance of the cones at the terminals thereof will match the impedance of the connections extending to the transmission line TL. The dimensions of the connections I3 and I 4 are such as to provide a 55 surge impedance equal to twice the value of the surge impedance of the main line TL, in order that the surge impedance of the main line TL may be matched by the two impedances of double its value. Since two connections I3 and I4 are in 60 parallel at the junction with the line TL, the combined impedances of these two connections at their junction present an impedance of one-half the surge impedance of one,and thus match the surge impedance of the line TL.

The conical surfaces of revolution of .Figs. 2 and 3 are, like those of Fig. 1, preferably of a length of the order of 0.36 wavelength at the midband frequency, as measured along the surface of the cone.

Each of the antenna arrangements of Figs. 1, 2 and 3 can have respectively stacked above one another similar arrangements to provide a multiple array in order to increase the directivity or concentration in the vertical plane. In such case, 75 the correspondingly located cones in the array Fig. 2 shows three radiating elements 4, Sand nections I, 8 and 9 which differ inlength from one should be energized cophasally. Any suitable spacing may be employed between the adjacent antennas in the array, it being preferred that a one-half wavelength spacing at the mid-band frequency be employed. One such arrangement is shown in Fig. 4, wherein three horizontal antennas A, B and C, each of the type shown in Fig. 3, are shown stacked one above the. other, in parallel planes to form an array. Adjacent antennas in the array are spaced apart by a distance of half a wavelength at the mid-band frequency, and correspondingly located cones in the array are energized cophasally by means of the vertical interconnections. Connections I3 and I4 differ in length from one another by an odd multiple, including unity, of a quarter wavelength, and serve to energize the two pairs of each antenna A, B, or C in the array at 90 with respect to each other.

It will be understood, of course, that the conical surfaces of revolution of the present invention may take any of the'forms illustrated and described in my copending applications, supra, particularly Serial No. 187,594, filed January 29, 1938, and will preferably have the lengths and angles taught therein.

What is claimed is:

1. A wide-band, non-directive, short wave antenna/for radiating horizontally polarized waves substantially uniformly in the horizontal plane, comprising a plurality of conductive structures having generally the form of conical surfaces of revolution, the longitudinal axes of said structures being in the horizontal plane and located at an angle with respect to one another, and means for energizing said structures at the apices thereof, whereby the energy in one structure differs in phase from the energy in an adjacent structure in the same plane by a predetermined amount the length and diameter of each of said structures being such that their impedance is substantially a pure resistance over a wide range of frequencies.

2. A wide band, non-directive, short wave antenna for radiating horizontally polarized waves substantially uniformly in the horizontal plane, comprising two conductive structures in the form of conical surfaces of revolution, the longitudinal axes of said structures being in the horizontal plane and at right angles to each other, and means for exciting one structure with energy having a phase displacement of 90 with respect to the energy in the other structure the length and diameter of each of said structures being such that their impedance is substantially a pure resistance over a wide range of frequencies.

3. A wide band, non-directive, short wave antenna for radiating horizontally polarized waves substantially uniformly in the horizontal plane. comprising two conductive structures in the form of conical surfaces of revolution, the longitudinal axes of said structures being in the horizontal plane and at right angles to each other, and means for exciting one structure in phase opposition to the other structure the length and diameter of each of said structures being such that their impedance is substantially a pure resistance over a wide range of frequencies.

4. A wide band, non-directive, short wave antenna for radiating horizontally polarized waves substantially uniformly in the horizontal plane, comprising three conductive structures in the form of conical surfaces of revolution, the longitudinal axes of said structures being in the horizontal plane and at angles of 120 with respect to one another, and means for exciting said structures, whereby the phase of the energy in one structure leads the energy in an adjacent structure by 120 and lags the energy in the other adjacent structure also by 120 the length and diameter of each of said structures being such that their impedance is substantially a pure resistance over a wide range of frequencies.

5. A wide band, non-directive, short wave antenna for radiatinghorizontally polarized waves substantially uniformly in the horizontal plane, comprising two conductive structures in the form of conical surfaces of revolution, the longitudinal axes of said structures being in the horizontal plane and at right angles to each other, and means for energizing said structures at the apices thereof, whereby the phase of the energy in one structure differs from the energy in the other structure by 90 the length and diameter of each of said structures being such that their impedance is substantially a pure resistance over a wide range of frequencies.

6. A wide band, non-directive, short wave antenna for radiating horizontally polarized waves substantially uniformly in the horizontal plane, comprising two pairs of conductive structures in the horizontal plane, each of said structures having the form of a conical surface of revolution, the apices of all conical structures facing substantially a central point, the longitudinal axes of the structures of each pair being in the same straight line, the longitudinal axes of said two pairs being at right angles to each other, whereby each conical surface of revolution is at right angles to its adjacent conical surfaces of revolution, and means for energizing the structures of one pair at a 90 phase relation with respect to the structures of the other pair the length and diameter of each of said structures being such that their impedance is substantially a pure re- 40 sistance over a wide range of frequencies.

'7. A wide band, non-directive, short wave antenna for radiating horizontally polarized waves substantially uniformly in the horizontal plane, comprising two pairs of conductive structures in 45 the horizontal plane, each of said structures having the form of a conical surface of revolution, the apices of all conical structures facing substantially a central point, the longitudinal axes of the structures of each pair being in the same 50 straight line, the longitudinal axes of said two pairs being at right angles to each other, whereby each conical surface of revolution is at right angles to its adjacent conical surface of revolution, and means for energizing the structures of 55 one pair at a 90 phase relation with respect to the structures of the other pair, a similar antenna located above said first antenna in a parallel plane and spaced therefrom by half a wavelength at the mid-band frequency to form an array, the

so correspondingly located conical surfaces of revolution in said array being energized cophasally the length and diameter of each of said structures being such that their impedance is substantially a pure resistance over a wide range of frequencies.

8. A wide band, non-directive, short wave antenna for radiating horizontally polarized waves substantially uniformly in the horizontal plane comprising two pairs of conductive structures in the horizontal plane, each of said structures having the form of a conical surface of revolution, the apices of all conical structures facing substantially a central point, the longitudinal axes of the structures of each pair being in the same straight line, the longitudinal axes of said two pairs being at right angles to each other, whereby each conical surface of revolution is at right angles to its adjacent conical surface of revolution, and means for energizing the structures of one pair at a 90 phase relation with respect to the structures of the other pair, similar antennas located above and below said first antenna in parallel planes and spaced from said first antenna by half a wavelength at the mid-band frequency, in order to form an array, correspondingly located structures in said array being energized cophasally the length and diameter of each of said structures being such that their impedance is substantially a pure resistance over a wide range of frequencies.

9. A wide band, non-directive short wave antenna for radiating horizontally polarized waves substantially uniformly in the horizontal plane, comprising a plurality of conductive structures in the form of conical surfaces of revolution having the axes thereof in a common horizontal plane and their apices adjacent, and means for so energizing said structures at their apices that a rotating field is radiated, the length and diameter of each of said structures being such that their impedance is equal to that of said means over a wide band of frequencies.

10. A wide band, short wave antenna for radiating horizontally polarized waves substantially uniformly in the horizontal plane, comprising a plurality of conductive structures in the form of conical surfaces of revolution having the axes thereof in a common horizontal plane and their apices adjacent and means connected to said structures at their apices for so energizing said structures that a rotating field is obtained, the length and diameter of each of said structures being such that their impedance is equal'to that of said means over a. wide band of frequencies.

11. A wide band, short wave antenna comprising a pair of conductive structures in the form of conical surfaces of revolution, the axes thereof being at right angles in the horizontal plane and their apices adjacent, and means connected to the apices of said structures for energizing said structures in phase quadrature whereby a rotating field is obtained, the length and diameter of each of said structures being such that their impedance is a substantially pure resistance of constant value over a wide range of frequencies.

PHH-IIP S. CARTER.

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