US2567260A - Antenna with dielectric casing - Google Patents

Description

Sept. 11, 1951 c. A. WILEY ANTENNA WITH DIELECTRIC CASING Filed Sept. 12, 1947 INVENTOR. CARL A. WILE'Y ATTORNEY Patented Sept. 11, 1951 UNITED STATES PATENT OFFICE ANTENNA WITH DIELECTRIC CASING Carl A. Wiley, Yellow Springs,- Ohio Application September 12, 1947, Serial No. 773,724 7 Claims. (01. 250-33) (Granted under't'he act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) 1 "The invention described herein may be mani1 factured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

My invention relates to a novel form of antenna in which the radiation is increased over that obtained from antennas of the prior art. In antennas of the prior art pronounced standing waves arise on the antenna due to excessive reflection of current from the outer end of the antenna. This is accompanied by a poor impedance match between the antenna and free space, with apoor radiation resistance for the antenna, and with a very narrow frequency range of radiation in consequence of the sharpness of antenna tuning. My invention provides a remedy forthis condition by surrounding a metallic rod antenna with a cone of dielectric spreading out from the point of current input of the antenna.

Accordingly a purpose of my invention is to provide a rod antenna with improved radiation and reception characteristics secured by incorporating dielectric material in the space about the antenna.

Another purpose of my invention is to provide an antenna with improved broad-band characteristics.

Another purpose of my invention is to provide an antenna with improved radiation pattern.

These and other purposes will appear fulfilled Fig. 1 of the drawing represents in section a quarter-wave antenna embodying my invention.

Fig. 2 of the drawing represents in section a half-wave antenna embodying my invention.

In Fig. 1 there is shown a quarter-wave rod antenna I mounted perpendicular to a conducting ground 2, which may be a metal sheet. Surrounding the rod is a hollow cone of insulating plastic material 3. The narrow end of the cone is at the input end of the rod antenna and the broad end at the outer extremity. The cone is filled with a dielectric such as distilled water, sufficiently purified to be non-conducting. The water is covered by a lid 4. The lower end of the cone fits watertight around the rod antenna. The antenna and ground are connected to a concentric transmission line 5 in usual manner. The line is selected to have an impedance match with the antenna.

It is well-known that the action of a quarterwave antenna is based upon the capacity of the upper end of the antenna to ground. It is the charging of this capacity that enables current to flow in the lower portion of the antenna and produce the radiation. It has been the practice of the prior art to supply the antenna with a flat top to increase the capacity. The structure to accomplish this is bulky and often unwieldy and the resistance of the fiat top to the currents flowing therein may well constitute a material absorber of electrical power. In my invention the flat top is not necessary; the capacity of the upper portion of the antenna is increased by increasing the dielectric constant in the space surrounding the upper portion. As the dielectric constant of distilled water is about "74, the in crease in capacity is very considerable. By mak ing the dielectric fan cut from the input point of the antenna its effect is fen increasingly up to the top of the antenna.

Due to the increase of capacity toward the top the antenna current tends to maintain itself more nearly uniform throughout the length of the antenna. This has three very desirable effects: it increases the radiation from the antenna for a given resistance loss in the antenna; this in turn increases the radiation resistance of the antenna and widens the frequency range of transmission and reception; due to improved linearity of current along the rod the upward radiation is suppressed and all radiation is more nearly horizontal. It is found that the physical length of the rod required to form a quarterwave radiator is reduced by this construction. A model constructed in this manner but less than of a wave length long was found to have a high radiation resistance and formed an excellent radiator.

The device shown in Fig. 2 is a half-wave radiator. The two-wire feed line 6 is terminated by two quarter-wave stubs I, 1 turned at right angles to the line and insulated from each other. Each stub l is surrounded by a mass 8 of anatase (T102) which has the shape of a figure of revolution with the cross section shown. The masses have the forms of solid horns each flaring away from the point of current feed at the center of the antenna. Other dielectrics which have high dielectric constants at radio-frequencies and are therefor suitable for use are rutile, bookite, BaTiOs, and a mixture of BaTiOa with 3 per cent SlTlOa. Common dielectrics available are the glasses and plastics.

The antennas shown are equally useful for reception as for transmission.

Having set forth the embodiments of my in- 3 vention in the above I Wish to describe it precisely in the following claims:

1. An antenna comprising, a radiating conductor having a current input point and an outer current nodal point, a homogeneous mass of nonabsorbing dielectric having a dielectric constant substantially greater than unity surrounding said radiating conductor and with a cross section increasing from said current input point to said current node.

2. An antenna comprising, a vertical conductor having a current input terminal and a current nodal point, a hollow cone of insulatin material surrounding said conductor with the apex of said cone at said current input terminal and the base of said cone at the current nodal point, and a body of non-conducting liquid having a dielectric constant substantially greater than unity filling said cone.

3. An antenna comprising, a plurality of cylindrical conductors having constant diameters and respective current antinodes and current nodes, and homogeneous conical masses of dielectric surrounding said conductors and having their apices adjacent to said current antinodes and their bells adjacent to said current nodes, said masses including solid cones of varying thickness.

4. An antenna comprising a radiating conductor having a current antinodal point and a current nodal point, a mass of non-absorbing dielectric having a dielectric constant substantially greater than unity and surrounding said radiating conductor, said mass of dielectric having a cross-section increasing from that part of said mass adjacent said current antinodal point to that part adjacent said current nodal point.

5. An antenna comprising a radiatin conductor having a current antinodal point and a ourrent nodal point and a mass of dielectric mounted about said radiating conductor and having a thickness increasing from that part of said mass adjacent said current antinodal point to that part adjacent said current nodal point.

6. An antenna comprising a pair of radiating conducting rods each having a current antinodal point and a current nodal point and a mass of dielectric mounted about said radiatin conducting rods and having a thickness increasing from thatpart of said mass adjacent said current antinodal points to that part adjacent said current nodal points.

7. An antenna comprising a pair of radiating conductors each having a current antinodal point and a current nodal point and a mass of dielectric mounted about each of said radiatin conductors and having a substantially uniform inner diameter and an outer diameter increasing from that part of said mass adj acent said current antinodal point to that part adjacent said current nodal point.

CARL A. WILEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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