US2086976A

US2086976A - Antenna system

Info

Publication number: US2086976A
Application number: US41349A
Authority: US
Inventors: George H Brown
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1935-09-20
Filing date: 1935-09-20
Publication date: 1937-07-13
Anticipated expiration: 1954-07-13
Also published as: GB481903A

Description

G. H. BROWN ANTENNA SYSTEM .Filed Sept 20, 1935 July 13, 1937.

2 Sheets-Sheet l r I jarawm fi mW l w i Patented July 13, 1937 ANTENNA SYSTEM George H. Brown, Haddonfield, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application September 20; 1935, Serial No. 41,349

11 Claims.

My invention relates to antennas. Specifical- 1y, my invention relates to a short wave transmitting antenna.

I am aware that vertical antenna systems of a height not exceeding a half wave length may be -used for horizontal radiation. Such systems are satisfactory for long wave lengths but are defective for short waves. It has been proposed to reverse phases between alternate half wave sec- I tions and thereby permit a plurality of half wave length sections to be employed. An antenna system of several half wave sections offers practical diificulties in the matter of separately insulating the sections. It has also been proposed to employ horizontal antenna elements with insulated masts and phase adjusting circuits, but such systems offer serious structural and electrical difficulties. The novel arrangement which I propose may be used to overcome these'difllculties and at the same time improve the radiating efficiency.

One of the objects of my invention is found in the design of an eificient transmitting antenna.

Another object is to secure uniform radiation in all directions in a horizontal plane about the antenna.

Anotherobject is to secure uniform radiation in all directions by a novel arrangement of horizontal antennas.

A further object is in a practical antenna de=- sign which permits a plurality of horizontal antenna sections to be conductively supported by a single metallic support.

Additional objects will be found in the accompanying specification and appended claims.

Figure I is a schematic diagram of one embodiment of my invention,

Figure II is a curve showing the approximate voltage distribution in a part of the antenna arrangement,

Figure III is a perspective view of an antenna system embodying my invention,

Figure IV is a curve illustrating the radiational field pattern about an antenna similar to Figure Figure V is a graph showing the' relative power ratio of an antenna embodying my invention and a single vertical half wave antenna, and

Figure VI is a graph showing the relative power ratio of a turnstile antenna and a vertical an-,

a plurality of sections 23 of a length equal to onehalf the length of the transmited wave. The lowermost section 25 2li of each of the vertical transmission lines Ill-2i has shunted across it an adjustable bridging member 24-26. The position of the bridging member, and the relative points at which the pair of transmission lines join the vertical transmission lines, are arranged to avoid reflections by a proper terminating impedance.

Every half wave length section 23 of each of the vertical transmission lines is transposed. When the vertical lines are energized, standing waves will be set up. Potential nodal points separated by a half wave length will be established. Each of the anti-nodal potential points on one side of the vertical transmission line will be of the same phase, becaus of the transposition of the line. Since one o the pair of connecting transmission lines-is one-quarter wave length longer than the other, and since the terminating impedances of the vertical lines may be adjusted, currents in one vertical transmission line 2| may be established in quadraturephase relation with respect to the currents in the other vertical line l9. 4

A series of horizontal antenna elements 29, preferably less than a half wave length long, are connected across points of similar voltage and opposite phase near the potential nodal points of each vertical line. The voltage distribution and the relative position of the horizontal antenna elements is indicated in Figure 11. The heavy dots 3i represent the horizontal antenna elements 29.

In Figure 'I, for convenience of illustration, each vertical transmission line with its connected horizontal antenna elements has been shown as separated. The vertical lines, per se, are separated but the corresponding horizontal elements of each vertical section are actually arranged to intersect at their centers. The intersection distance between the horizontal elements.

fat

should be at right angles if uniform circular radiated fields are desired. Although my invention may be adapted to radiate waves of several patterns, I shall describe an antenna whose radiational characteristic will establish uniform fields at uniform horizontal distances from the antenna. This type of antenna employs. horizontal antenna elements in the form of a symmetrical cross. The arrangement may be characterized as a turnstile antenna.

Since the centers of the plurality of horizontal antenna elements are symmetrical with respect to the four conductors of the vertical transmission lines, they are atneutral voltage points andlrnay be conductively connected to a common supporting member, which may be made of metal or any suitable material. Such an arrangement is illustrated in Figure III. A metallic pipe or mast 4|, preferably self supporting, is erected on a suitable foundation 43. A number of crossed horizontal antenna elements are fastened to the mast by any suitable method, such as threading, clamping or welding. The horizontal elements are spaced from each other by substantially a half wave length; i. e., the horizontal elements are spaced at half wave length intervals on the vertical transmission line but the sections of the transmission lines are slightly longer than the The vertical transposed transmission lines 41 are symmetrically arranged to spiral around the mast and are connected to the horizontal elements at points about one-twentieth of a wave length from the surface of the supporting pole. Stand-oil? in-, sulators 49 maybe used to prevent the conductors of the transmission lines from contacting the" supporting pole or from contacting each other. In Figure III, a single conductor of one of the four transmission conductors has been shown. The other conductors have been omitted to avoid confusion in the illustration.

It may be shown that the field of radiation at a distant point with respect to the antenna varies with the angle with the angle v-which is the angle between the one series horizontal antenna ele ments and a line from the cent r of the antenna to the distant point and is (I) F1=I1 sin!) sin at The corresponding field of radiation at a distant point for the other series of vertical antenna ele- But since the currents I1 and I2 flowing in both series of horizontal antenna elements are equal the Equation (III) may be rewritten as (IV) F1+F2=I1 (sin 0 sin wt+cos 0 as at) The expression within the brackets of Equation IV bears the relationship of The Equation (V) indicates that the field will rotate around the antenna at a speed proportional to the frequency of the source, and that the field will have a uniform strength at all points equally distant from the antenna in-a horizontalplane.

' tion one series of horizontal antenna elements is represented as lying in a plane represented by a line a. The other series of horizontal elements is represented as lying in a plane represented by a line b. The radiation from the elements in the plane a will have a figure 8 characteristic shown as A; while that from b may be shown as B. The fields rotate at a 90 phase relationship which gives a resultant field C which is a circle. The circle C represents uniform field strengths at uniform'horizontal distances from the antenna.

The turnstile antenna of my invention is more efllcient than vertical half wave antennas. In Figure V I have compared the power ratio of an antenna embodying my invention to a single vertical half wave antenna. It will be seen that for turnstile antennas of two or more crossed sets of horizontal elements the power ratio shows that the turnstile antenna is more effective than the vertical half wave antenna. I am aware that a vertical antenna of several half wave lengths may be used by proper phase reversals between the half wave sections. An antenna of several vertical half wave sections offers serious construe-- tional difliculties in matters of insulation and support which are not present in an antenna embodying my invention. Even if the practical difilculties are overcome, the power ratio is very much in favor of the turnstile antenna. The relative power ratios for varying heights of antennas of both types are illustrated by the graphs of 'gureVI.

Although I have shown by way of example, one embodiment'of my invention I do not intend to thereby limit my invention. Various modifications within the scope of my-invention will occur to those skilled in. the art. I only intend to limit my invention as required by the prior art and by the appended claims.

-I claim:

1. In an antenna system of thecha'racter described, a pair of vertical transmission lines, means for creating standing waves on said vertical lines, means for establishing a quadrature phase relation between the currents in said lines,

and a plurality of pairs of crossed horizontal antenna elements each of said pairs having a common conductive junction connected to potential points of similar voltage on each of said pairs of lines.

2. In an antenna system of the character described, a pair of vertical and symmetrically disposed transmission lines, means for creating standing waves'on said vertical lines, means for establishing a quadrature phase relation between the currents in said lines, and a plurality of pairs of crossed horizontal antenna elements each of said pairs having a common junction connected to potential points of similarvoltage on each'of said pairs of lines.

3. In an antenna system of the character described, a pair of vertiealtransmission 1ines,

means for creating standing waves on said vertical lines, means for establishinga quadrature phase relation between the currents in said lines, and a plurality of crossed horizontal antenna elements, each of said elements having a common conductive intersection, connected to potential points of similar voltage on each of said pairs of lines.

4. In an antenna system of the character described, a pair of vertical and symmetrically disposed transmission lines, means for creating I standing waves on said vertical lines, means for establishing a quadrature phase relation between the currents in said lines, and a'plurality of crossed horizontal antenna elements, each of said elements having a common conductive intersection, connected to potential points of similar voltage on each of said pairs of lines.

5. In an antenna, a pair of vertical transmission lines, means for creating standing waves on ing a quadrature phase relation between the currents flowing in said lines, -a plurality of crossed horizontal antenna elements, each of said elements having a common conductive junction, confl nected to similar potential points in one of said lines, and a plurality of similar horizontal elements positioned at right angles to the first mentionedhorizontal elements-and connected to the other of said transmission lines at potential points bearing quadrature phase relation to the first mentioned potential points.

6. In a devige'of the character described, a conductive mast two sets of crossed antenna elements positioned at half wave length intervals on said mast and conductively'connected thereto, 'one transmission line connected to one'of-said sets of elements, another transmission line connected to the other of said sets of elements, means for transposing alternate sections of each of said pair of lines, and means for impressing alternatin'g currents on said pair of lines of equal magni tude and quadrature phase.

for conductively supporting said antenna elements, a first transmission line connected to one series of said elements at points of similar potential and similar phase, a second transmission line connected to the other of said elements atpoints of similar potential and similar phase, and means for impressinglaltemating currents on said transmission lines of equal magnitude and quadrature phase. 1 l

8. In an antenna system of the character described, a pair of vertical transmission lines, means for creating standing waves on said vertical lines, means for establishing a quadrature phase relation between currents in said lines, a plurality of horizontal antenna elements of the order of one-half wave length long connected 7 to potential points of similar voltage on each of said pairs of lines, and a conductive mast for conductively supporting said antenna elements.

9. In a device of the character described, a metallic mast, two series of horizontal antenna elements disposed in vertical planes which intersect at right angles at the centers of said elements, said mast conductively supporting said elements at said centers, a pair of vertical conductor wires connected to points on the horizontal elements equally distant from the surface of the mast and transposed between each of said elements, a'simi- ,lar pair of conductors connected in similar manner to the other set of horizontal elements, and

means for impressing high frequency oscillatory currents diflering by quadrature phase on each of said pairs of conductors.

10. A device of the character described in claim 9 including means for establishing standing waves on each of said pairs of conductors.

11. A device of the character described in claim 9 and including means tor connecting the pairs of conductors on the horizontal elements at a distance of about one-twentieth of a Wave length from the surface of the metallic mast.

GEORGE H. BROWN.