US3324476A

US3324476A - Broad band antenna

Info

Publication number: US3324476A
Application number: US428332A
Authority: US
Inventors: Jr Valor C Smith; John O Watson
Original assignee: LAN JEN CHU
Current assignee: LAN JEN CHU
Priority date: 1965-01-27
Filing date: 1965-01-27
Publication date: 1967-06-06
Anticipated expiration: 1984-06-06
Also published as: GB1076233A; SE315640B; DE1491925B1; NO117430B

Description

June a, ww-

V. (3.- SMITH, JR. ETAL BROAD BAND ANTENNA Filed Jan. 2'7, 1965 INVENTORS VALOR C-SMITH ,J'R. JOHNQWATSON Q M W m ATTORNEYS Mass.

Filed .l'an. 27, 1965, Ser. No. 428,332 7 Claims. (Cl. 343830) The present invention relates to broad band antennas and, more specifically, to monopole antennas of the very broad band type.

Numerous configurations of monopole structures have been evolved and used for broad band reception and transmission including conical segment monopole structures and disc cage antennas, as two of the more common. While such structures can be employed over broad frequency bands, they require, particularly at the lower frequencies, sizable and costly constructions and they do not lend themselves, in several particulars, to substantially direct scaling techniques, especially in the higher frequencies, including the microwave range. It is, accordingly, to the purpose of providing a new and improved broad band monopole antenna that shall not be subject to the above-mentioned disadvantages that the present invention is primarily directed; it being an object of the invention to provide a novel, simplified, less costly and less sizable broad band antenna of this character.

A further object is to provide a novel antenna of more general use, as well.

Other and further objects will be made apparent hereafter and will be more particularly delineated in the appended claims. In summary, however, the antenna of the invention contemplates a closed loop of critically oriented sections from which substantially parallel arrays or conductors of radically different dimensions extend in opposite directions. Preferred constructional details are hereinafter set forth.

The invention will now be described in connection with the accompanying drawing, the single figure of which is an isometric of a preferred embodiment thereof.

A closed loop L is shown comprising a first horizontally oriented central straight section 1 bounded by upper and lower substantially parallel spaced segments 1' and 1", fed near their centers by the inner conductor 2 and the outer conductor 2' of a coaxial feed line, so as to effect a shunt-type of feed for transmission or reception. At the ends of the central straight section 1 similar diverging acute-angle sections are provided at 3 and 3, terminating, in turn, in similar horizontal straight sections 5 and 5'. Upper and lower arrays 4 and 4' of substantially parallel conductors or radiators extend in opposite directions from the upper and lower segments of the loop L, and substantially coplanar therewith, and with the conductors 7 of the array 4 being of much greater length than the conductors 7 of the array 4 for purposes later explained. The lower ends of conductors 7 of the array 4 and the upper ends of conductors 7 of the array 4 are connected together by a rectangular conductive frame 9 that also closes off the left and right hand ends of the loop sections 5 and 5'. The conductors 7 and 7' preferably are horizontally spaced a distance similar to the width of the loop L, but in all cases a distance very small compared to the smallest wave length to be used with the antenna so as, in effect, to present the appearance of a relatively continuous conductive surface.

It has been found that remarkably good matching can I 3,324,476 Patented June 6, 1967 be attained over frequency bands of as much as five-toone frequency ratio, consistent with, for example, omnidirectional radiation pattern of vertically polarized radiation, provided the closed loop L has substantially the geometry above described and is provided with a section 1 of horizontal length less than A; of the maximum wave length of the band, with the transition or matching loop segments 33' diverging at angles of the order of substantially degrees, and with the horizontal length of the terminal extensions 5 and 5' being considerably shorter than the length of the section 1, say of the order of A: as long. Such, broad band and omni-directional results have been obtained, moreover, with the overall vertical length of the frame 9 approximately of the maximum wave length of the band, a horizontal length of frame 9 approximately 0.085 of such wave length, and a horizontal length of the section 1 approximately 0.01 of the maximum wave length. To attain the broad band matching results consistent with omni-directional pattern, furthermore, it has been found that the conductors of the upper array 4 should be much longer than those of the lower array 4; say, in the ratio of about 9 to 1, more or less. In the case of the vertical polarization, the

conductors

7 and 7 of the arrays 4 and 4 should be substantially vertical and thus substantially orthogonal to the straight section '1.

When the planar antenna of the present invention is employed on aircraft or in other areas where streamlining is essential, it may be imbedded in a plastic tear-shaped housing 11.

It has been found that this type of slab or planar vertically polarized monopole gives substantially the same electrical performance as the much more costly, spaceconsuming conical monopoles and disc cage antennas of the prior art, and provides, also, the advantage of less obstruction to ancillary radiation equipment, such as,

radars and the like. Variation from the rectangular frame shape and the sharp angular configuration of the loop L may, of course, be effected without departing from the spirit and scope of the invention, provided the'critical relative dimensions and orientation of the parts are substantially maintained as above-described.

What is claimed is:

1. A broad band substantially planar antenna having, in combination, a closed loop of substantially parallel spaced segments comprising a central straight section terminating at its ends in similar diverging sections that terminate, in turn, in similar straight sections substantially parallel to the central section but of shorter length, feed means connected to opposite spaced segments of the central loop section, and a pair of arrays of substantially parallel conductors extending in opposite directions from the loop sections, one array being of much shorter length than the other.

2. An antenna as claimed in claim 1 and in which the spacing between the said parallel conductors is small compared to the minimum wavelength to be used with the antenna.

3. An antenna as claimed in claim 2 and in which the said conductors extend substantially orthogonally from the said straight sections of the loop.

4. An antenna as claimed in claim 1 and in which the angles of divergence of the diverging sections of the loop are substantially 1-60 degrees with respect to the'central straight section.

5. An antenna as claimed in claim 1 and in which the overall length of the arrays is of the order of 0.2 A/max,

7. An antenna as claimed in claim 6 and in which the planar antenna is imbedded in a streamlined plastic housing.

No references cited.

HERMAN KARL SAALBACH, Primary Examiner.

R. D. COHN, Assistant Examiner.

Claims

1. A BROAD BAND SUBSTANTIALLY PLANAR ANTENNA HAVING, IN COMBINATION, A CLOSED LOOP OF SUBSTANTIALLY PARALLEL SPACED SEGMENTS COMPRISING A CENTRAL STRAIGHT SECTION TERMINATING AT ITS ENDS IN SIMILAR DIVERGING SECTIONS THAT TERMINATE, IN TURN, IN SIMILAR STRAIGHT SECTIONS SUBSTANTIALLY PARALLEL TO THE CENTRAL SECTION BUT OF SHORTER LENGTH, FEED MEANS CONNECTED TO OPPOSITE SPACED SEGMENTS OF THE CENTRAL LOOP SECTION, AND A PAIR OF ARRAYS OF SUBSTANTIALLY