US3147480A - Broadband plate antenna - Google Patents

Description

Sept. 1,1964 5.4. LAMBERTY 3,147,480

' BROA AND PLATE ANTENNA v Original Filed July 9, 1959 INVENTOR BERNARD J. LAMBERTY BY) flw f/fw k ATTORNEY United States Patent Office 3,147,480 Patented Sept. 1, 1964 3,147,480 BROADBAND PLATE ANTENNA Bernard J. Larnherty, Santa (liar-a, Caiif., assignor to Syivania Electric Products, Inc, a corporation of Delaware Original application July 9, 1959, Ser. No. 825,996, new Patent No. 3,050,750, dated Aug. 21, 1962. Divided and this application May 17, 1962, Ser. No. 197,225 1 Claim. (Cl. 343848) This invention relates to antennas, and more particularly to a class of physically small, broadband, mediumgain antennas. This application is a division of application S.N. 825,996, filed July 9, 1959, assigned to the assignee of this application, now Patent No. 3,050,730.

A difficulty commonly experienced in antenna design is achieving broadband operation while holding the physical size to a minimum. For a better understanding of terms, broadband operation as used herein means the antenna requires no tuning to match its impedance to some relative impedance having a voltage standing wave ratio (VSWR) of less than 4.0 to 1 over a frequency band at least three times the lowest operating frequency. Efforts in the past to build broadband small size antennas resulted in antenna configurations which are a function of angle only and not of length, that is, the antenna is impliedly infinite in extent. Spirals and modifications of spirals are examples of such antenna configurations. The difiiculty with this type of antenna is that the size of the antenna must be at least a wavelength at the lowest operating frequency. Furthermore, these antennas do not have a large bandwidth when operated over a ground plane and usually are complex and difiicult to construct. Other types of antennas in this class are conical dipoles which must be at least a quarter wavelength high and have rather limited bandwidth.

The class of antennas to which this invention relates operates over an extremely broad frequency band, in the order of 20 to 1, has a medium-gain characteristic, and is small in physical dimension-in the order of a sixth of a wavelength or less at the lowest operating frequency. The fundamental antenna design on which this class of antennas is based is a folded loaded unipole antenna characterized by several folds between the input end and the opposite end, the latter end being shorted to the ground plane over which the antenna is operated. The fingers comprising the folds are spaced apart and are made of conducting material, the entire antenna generally resembling an end-fed glove. One embodiment comprises center-fed crossed rectangular plate and is one of a variety of different kinds of antennas which result from optimization of the desirable features of the basic structures. The advantages of small physical size relative to a wavelength, and uniform patterns and impedance response are achievable in varying degrees with this antenna.

An object of the invention is to provide a broadband antenna having a small physical size with respect to a wavelength. Another object is the provision of a broadband antenna having medium-gain characteristics and relatively uniform radiation patterns, and whose largest physical dimension is in the order of a sixth of a wavelength or less at the lowest operating design frequency. A further object is the provision of a physically small antenna having relatively constant radiation pattern and impedance characteristics over frequency bands in the order of 20 to 1 or greater. Still another object is the provision of a broadband plate-type antenna which can operate above a ground plane. A more specific object is the provision of an antenna having a radiating element made of a solid or continuous rectangular conducting plate.

These and other objects of my invention will become apparent from the following description of the various embodiments thereof, reference being bad to the accompanying drawings showing a perspective view of an antenna structure comprising two center-fed crossed rectangular plates.

Referring now to the drawing, antenna 10 comprises two center-fed rectangular plates 11 and 12 crossed at right angles to each other along the feed point and over ground plane 13. The center conductor 14 of the coaxial feed line is joined to the lower edges of the plates at their points of intersection. The effect of this configuration is that the radiation pattern minima of one plate are largely filled by the radiation pattern maxima of the other, since the plates are orthogonal to each other, as are the radiation pattern maxima and minima of a single plate structure. Orthogonal placement of two such plates also results in elimination of the undesirable lobes.

The VSWR of the cross-plate antenna 10 averages at about 3.0 to 1 over a frequency range of 20 to 1. H- plane patterns are omnidirectional to within 3-db variation over the 20 to 1 frequency band. E-plane patterns are essentially the same as those of a single center-fed continuous rectangular plate antenna. The height of the crossed plate antenna 30 is approximately one-eighth of a wavelength at the lowest operating frequency f Modifications, changes and improvements in the above described embodiment of my invention may be made by those skilled in the art without departing from the precepts of my invention. The scope of the invention, therefore, is defined in the appended claim.

I claim:

A high frequency antenna comprising a pair of continuous generally rectangular plates of conducting material, said plates being mounted close to and normal to a ground plane and intersecting each other along the axis of symmetry of each, and a transmission line connected to the edges of said plates at the point of intersection.

France Apr. 30, 1927 Switzerland Feb. 16, 1948

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