Unitary cellular antenna system

The unitary cellular telephone antenna includes a junction box to which is mounted both the antenna element, preferably a 5/8 wavelength antenna, and two 1/4 wavelength downwardly oriented radials to establish the antenna's ground plane. Electrical elements are included within the junction box to match the impedance of the antenna system to the cellular telephone transceiver and to maximize the radiated signal.

BACKGROUND OF THE INVENTION 
The present invention relates to a cellular telephone antenna, particularly 
one incorporating both antenna and ground plane elements. 
As cellular telephone systems have grown in popularity, the telephone 
themselves have become smaller and smaller in size and more and more 
convenient to use. Presently a number of cellular telephones are 
completely contained within a hand held unit, and easily portable. 
Typically these portable cellular telephones incorporate a small antenna, 
one which while adequate in many applications is inadequate in 
applications requiring a low loss, high efficiency antenna especially for 
distant communications. 
Various designs of cellular telephone antenna systems have been built and 
are in use today. One example of such an antenna is described in U.S. Pat. 
No. 4,794,319 to Shimazaki. In general, this type of cellular telephone 
antenna is designed for a permanent, fixed mount such as on the rear glass 
window of an automobile. It is not portable. 
An objective of the present invention is to provide an antenna system for 
portable cellular telephones that offer high gain, and that is also 
portable. Another objective of the present invention is to provide a 
portable cellular telephone antenna system that incorporates both an 
antenna element and ground plane elements. These and other objects of the 
invention will appear from the following description of the preferred 
embodiment. 
BRIEF SUMMARY OF THE INVENTION 
The present invention provides a unitary cellular antenna assembly that 
mounts, on a junction box, a fractional wavelength antenna and a plurality 
of ground plane radial elements, the antenna and the elements being 
mounted on the junction box such that when the box is oriented to direct 
the antenna generally vertically upward the radial elements are angled 
downwardly relative to the horizontal plane established by the antenna. 
In a preferred embodiment, the antenna and ground plane elements lie 
generally in the same plane, and the junction box includes means for 
removably attaching it to a surface. In addition, the preferred unitary 
cellular antenna assembly incorporates impedance matching elements to 
substantially match the output impedance of the cellular telephone 
transceiver to the input impedance of the antenna assembly. Further, the 
preferred assembly incorporates a 5/8 wavelength antenna and at least two 
1/4 wavelength radial elements, which elements are downwardly directed at 
an angle of from 120 degrees to 150 degrees relative to the antenna.

DETAILED DESCRIPTION 
The preferred unitary cellular telephone antenna is designed to be mounted 
on vehicle window or other supporting surface, and to be connected to a 
portable cellular telephone to replace its normal, relatively inefficient, 
antenna. 
While it incorporates a suction cup permitting it to be easily mounted on 
any appropriate surface, and to be carried from location to location by 
the user, it may also be permanently mounted on a surface for use, for 
example, with other than hand-held cellular telephones. 
As shown in FIG. 1, the unitary cellular telephone antenna 2 of the present 
invention may be mounted on a any window of a vehicle, and easily 
connected by a coax cable (not shown) to a portable cellular telephone to 
improve the range and reception of that telephone. It may, of course, be 
attached to any other appropriate surface. Its advantage is that it is as 
portable as a cellular telephone, yet when used significantly improves the 
range and reception of that portable telephone. A preferred construction 
of the unitary portable cellular telephone is shown in FIGS. 2 and 4. It 
includes a junction box 10 that is generally square on overall shape, with 
a removable flat base 12 that is approximately 13/4" along each edge. An 
outer face 14 is spaced a short distance from the base. Between the base 
and the outer face of the junction box are rectangular side faces 15, 
preferably eight in number, to provide three facets or planar surfaces at 
an angle of 120 degrees to one another. 
An antenna element 16 is mounted to the top facet or planar surface of the 
junction box, and includes a threaded cylindrical shaft 17 that extends 
through an opening in the junction box and is received by a nut 18 which 
clamps the antenna to the junction box. Preferably the antenna is a 5/8 
wavelength element which, for typical cellular telephone systems in use in 
the United States, is approximately 81/4" long. 
Two 1/4 wavelength radial elements 22 are similarly mounted to side planar 
surfaces, or facets 15, of the junction box to project downwardly at an 
angle of approximately 120 degrees to the antenna element, the antenna 
element and radial elements preferably lying in the same plane. Underlying 
the nuts 23 which receive the threaded bases of the radial elements and 
clamp the radials to the junction box, are tabs of a conductive brass 
plate 24 that completely covers the inside face of the junction box, the 
tabs electrically connecting the radial elements to the plate 24. 
A threaded female coax connector 30 is also mounted to a side facet of the 
junction box, as shown in FIG. 2, by a nut 32 received on the threaded 
interior end of the connector. An inductor 42 and the center terminal of 
the adjustable capacitor 36, electrically attaches the center conductor of 
connector 30 to antenna element 16, and serves as a loading coil. A 
capacitor 36 is received in a central opening in the brass plate 24 and is 
mounted on the face of the junction box. A slotted element 37 of the 
capacitor extends through the face of the junction box, and may be turned 
by a screwdriver to adjust the capacitance of the element. 
By adjusting capacitor 36, the reactance of the loading coil 42 for the 
antenna may be balanced out and the antenna system matched to the 50 Ohm 
output impedance typically designed into cellular telephone transceiver 
systems to minimize the VSWR on the coax line. As a result, an antenna at 
maximum efficiency may be achieved. In the preferred construction, the 
present unitary telephone antenna offers substantially a 3 DB gain, as 
opposed to what usually is at best a 1 DB (or unitary) gain of most of the 
whip antennas mounted on portable cellular telephones. 
As best shown in FIG. 4, preferably a suction cup 50 is mounted to the base 
of the junction box to attach the unitary antenna to an appropriate 
surface such as the side window of an automobile as shown in FIG. 1. In 
the preferred construction, a small metallized area 51 is provided on the 
interior surface of the base plate 12 of the junction box, and a nut 52 is 
soldered to this metallized interior surface to receive a threaded stud 54 
extending from the suction cup through an appropriate opening in the base 
of the junction box. The base plate 12 is removably attached to the 
junction box by screws, for example. 
The junction box may be more permanently attached to a surface, if desired, 
by simply removing the suction cup and using a double sided adhesive tape 
as the mounting means. 
While the preferred embodiment of the present invention has been 
illustrated and described, variations in the construction of the unitary 
telephone antenna will be apparent to those skilled in the field. For that 
reason, the scope of the invention is not defined by the preferred 
embodiment, but instead is as set forth in the following claims.