A bi-directional antenna array is disclosed having at least two vertical loop antennas arranged mutually perpendicular individually operable to produce bi-directional scanning patterns shifted ninety degrees to achieve significant side rejection so that a user can better utilize the congested frequency spectrum.

BACKGROUND OF THE INVENTION 
A previous loop antenna is disclosed in U.S. Pat. No. 2,256,619 which 
discloses an antenna having one loop in the vertical plane and one loop in 
the horizontal plane and a dipole antenna arranged vertically through the 
center area. However, this arrangement is directed mainly to providing a 
directional system which can find either vertically or horizontally 
polarize waves and does not provide significant side rejection for use in 
congested areas. Another prior loop antenna is disclosed in British Pat. 
No. 362,530 which is directed to the provision of a non-directional or 
omini antenna by utilizing shortened loops turned by an electrical circuit 
to compensate for the impedance mismatch caused by the shortened loops and 
does not provide significant side rejection in either plane. 
SUMMARY OF THE INVENTION 
It has been found according to the invention that a highly versatile 
antenna can be had by providing a pair of large circular loop elements 
carried vertically on a base axis with the planes of the respective loops 
being mutually perpendicular to one another whereby the antenna can be 
operated to produce a bi-directional scanning pattern by selectively 
driving either loop either vertically or horizontally providing a high 
degree of side rejection of unwanted signals to better utilize the 
congested frequency spectrum. 
Accordingly, an important object of the present invention is the provision 
of a versatile antenna system with which a radio operator may better 
utilize a congested frequency spectrum. 
Another important object of the present invention is the provision of an 
antenna array which produces a bi-directional pattern moving out from the 
antenna element equally in opposite directions wherein the bi-directional 
pattern may be shifted in direction to provide a scanning antenna. 
Another important object of the present invention is the provision of a 
large loop antenna wherein the loop element is formed by a unique and 
improved construction. 
Another important object of the present invention is the provision of an 
antenna array having particular advantages for citizens band radio usage 
having a pair of mutually perpendicular large vertical loops which may be 
individually driven and manually switched to provide bi-directional 
scanning patterns either vertically or horizontally polarized affording 
significant side rejection of unwanted signals.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring to the drawing, a bi-directional antenna array is illustrated 
which, in its basic design, includes at least two vertical large loops 10 
and 12 arranged mutually perpendicular to one another and supported by a 
base axis 14. The base axis lies generally in the vertical plane of both 
loops. In the preferred form, the loops are circular in shape. As 
illustrated, each circular loop element is constructed from a plurality of 
individual flexible radiating sections 16. 
Each section 16 includes a center conductor core 18 which may be made of 
any suitable electrical conductor such as aluminum or copper and the like. 
The center core 18 is encapsulated by an outer layer 20 made from a 
suitable dielectric material which is preferably reinforced such as a 
reinforced fiberglass composite giving the section structural rigidity and 
allowing it to bend to form the circular or other closed-curve loop 
configuration. The ends of the individual radiating sections 16 may be 
joined by any suitable means such as a pressure-fit ferrule connection 22 
having a socket 22a and a plug 22b. The socket and plug of the ferrule 
connection are conductive and are connected to the conductive center core 
18 of the radiating section so that a continuous conductive path may be 
established around the loop when joined together. 
Not only does the construction of the individual radiating sections 16 
provide advantageous structural characteristics to the antenna, but such a 
construction mutually insulates the loops against one another in their 
contact area adjacent the top and bottom of the antenna array and enables 
the antenna to be assembled with conventional mechanical hardware. Thus, 
insulating hardware such as at cross arms 24 and 26 as well as at the 
other various connection points which has been required in previous large 
loop antennas is eliminated. The base axis 14 may be joined to the loop 
elements 10 and 12 and the cross arms 24 and 26 by any conventional 
hardware as shown. 
The individual elements may be four or five feet in length for convenience 
in shipping and assembly and are approximately 1/4 of an inch in diameter. 
Shortened sections, approximately two feet, may be supplied to adjust the 
loop size and characteristic as desired. In one embodiment, loop elements 
twelve feet in diameter are utilized at a frequency of 30 megacycles 
whereby the loops correspond in circumference to a one-wave length loop 
element. 
Electrical terminal connections to the loop elements 10 and 12 at switching 
terminals 10a and 12a may be made by any suitable means such as by the 
terminal connectors shown generally at 28. Two of the radiating sections 
16a and 16b are specially adapted for making connection to a power source 
30 such as a radio. For this purpose, the terminal end of these sections 
are provided with a threaded electrical connector 32 and 34, respectively, 
affixed to the ends of each section which may be threaded into a 
dielectric block member 36. Coaxial cable lead 38, connected between 
switch terminal 10a and connector 28 is received within female connector 
portion 40 of the connector means 28. The center conductor of the coaxial 
makes electrical connection with section 16a through the conductive 
connector 42 and connector 32. The outside conductor of coaxial cable 38 
makes electrical connection with element 16b through conductive connectors 
44 and 34. Members 36 and 46 are insulating members. A similar connection 
is made between switching terminal 12a and connector means 28 of loop 
element 12 by means of coaxial cable lead 48. It is to be understood, of 
course, that other suitable hardware may also be utilized from making the 
aforesaid electrical and mechanical connections. 
The vertical loop antenna elements 10 and 12 so arranged provide the 
respective bi-directional patterns A and B, respectively, as shown in FIG. 
2. The antenna array may be oriented such that pattern A is a typical 
North-South pattern and pattern B is an East-West pattern. As illustrated, 
the terminals of the loop elements are at the bottom and the radiation is 
horizontally polarized. When the terminals are moved to the quadrants on 
the side of the loops, such as at 50, the radiation will be vertically 
polarized. It is contemplated that the basic antenna array as illustrated 
may also be operated wherein one loop is driven horizontally and the other 
perpendicular loop is driven vertically. However, in such instance, a 
light rotor may be required to provide the desired performance. Since one 
of the objects of the present invention is to provide a simple antenna 
arrangement which does not require a rotor for good performance and side 
rejection, the following operation and explanation of the invention will 
be with reference to both loops being either horizontally or vertically 
polarized. 
Operation of the antenna array as a manually scanning bi-directional 
antenna will now be explained. It will be seen that if a manual switch S 
is provided, the antenna loop elements 10 and 12 may be selectively 
connected to the radio 30 and operated to produce either bi-directional 
scanning pattern A or B. Bi-directional pattern A produced by antenna 
element 10 has a major signal load extending equally in opposite 
directions, North and South, from the base axis and a minor signal load in 
an East-West direction generally perpendicular to the major signal load 
direction. The second bi-directional pattern B produced by the antenna 
element 12 has a major signal load in the East-West direction extending 
generally equally in opposite directions from the base station and a minor 
signal in the North-South direction generally perpendicular to the major 
signal load. The radiation is maximum perpendicular to the plane of the 
loop and is minimum in any direction in the plane containing the loop. 
It will be seen that with the loop antenna elements arranged on the base 
axis mutually perpendicular to one another the antenna element may be 
selectively operated to produce either of the bi-directional scanning 
patterns A or B to the exclusion of a significant portion of the 
nonselected pattern affording a high degree of side rejection of unwanted 
signals and better utilization of a congested frequency spectrum such as 
citizen band operation. For example, if a radio operator using the antenna 
array at a base unit wishes to communicate with another party at X, the 
operator may select pattern A while another party utilizing the same 
frequency at Y will manage to do so without interfering with the use of 
the same frequency by the base operator. This simultaneous usage of the 
frequency spectrum is achieved because of the significant side rejection 
of the pattern B achieved by utilizing pattern A. Thus, in this manner, 
the antenna may be used as a manual scanning antenna by shifting between 
the bi-directional patterns A and B. Side rejection of 25 db may be 
achieved in accordance with the invention. Any suitable coaxial switch may 
be utilized at S such as Model 442 coaxial switch manufactured by the 
Winn-Tenna Corporation of Anderson, S.C. 
The antenna so described has the advantages of a directional antenna but is 
essentially a bi-directional antenna in that an equal signal is produced 
in the pattern in the opposite directions eliminating the need for a 
rotor. 
It can be seen that an advantageous construction for a large closed loop 
antenna can be had according to the invention wherein a pair of 
perpendicular loop elements are arranged and adapted for shifting between 
a pair of bi-directional scanning patterns with significant side rejection 
achieved to better utilize a congested frequency spectrum. 
While a preferred embodiment of the invention has been described using 
specific terms, such description is for illustrative purposes only, and it 
is to be understood that changes and variations may be made without 
departing from the spirit or scope of the following claims.