Planar radiation antenna elements and omni directional antenna using such antenna elements

An antenna of the long frame-type wherein the ratio between the long side and the short side is between 1:4 and 1:8 and the length of the long side is equivalent to one wavelength of the central frequency. One pair of short bars are deployed so that they are located at a distance corresponding to 1/4th to 1/40th of the distance from both end parts of the entire long side length of each long side element. The two end portions of the long side of the antenna is symmetrically bent with respect to a central portion such that the two end portions form an angle of 45 to 90 degrees with respect to the central portion and are parallel to each other.

This application claims priority under Japanese Application No. H9-340853 
filed Nov. 27, 1997. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to antenna elements and an antenna using such 
elements for receiving high-frequency, or radio waves to enable reception 
of relay or repeater signals, broadcast and communication signals, etc. 
2. Description of Related Art Including Information Disclosed Under 37 CFR 
1.97 and 1.98 
It is well known that radio waves are transmitted for use by relays or 
repeaters, by broadcasting and radio communication, and are received by 
radio antennas where they may be used to provide instructions or even for 
controlling traffic systems. Antennas for such use may be vertically 
mounted to a ground pole or may be a vertically mounted dipole, etc. 
However, since these antennas are usually set to a mode for receiving 
vertically polarized waves, it is usually not possible to achieve 
sufficient gain where antennas with such directional characteristics are 
used. In addition, super-gain antennas and similar antennas which are 
non-directional (omnidirectional) can also be used as a means for 
transmitting information such as TV broadcasts via radio waves. 
Unfortunately, these antennas have a complicated construction. 
Planar radiation antennas, commonly called "modified antennas", are often 
used for amateur radio. The advantage of these antennas is that they have 
a high gain and they also make it possible to select any polarized wave 
mode. A disadvantage of these antennas is that it is difficult to obtain 
omnidirectional characteristics. 
In view of the above-described problem, the inventor of this invention 
provides an antenna which not only makes it possible to freely select the 
polarized wave mode with a high gain, but which also has omnidirectional 
characteristics and which is suitable for a wide range of applications. 
The antennas and elements of this invention are suitable for broadcast to 
wide areas, for relaying, for communication, for traffic control system, 
and for mobile communications. The antennas can also be used for a wide 
range of frequencies including HF, VHF, and UHF. 
SUMMARY OF THE INVENTION 
In order to solve the above-mentioned problems in accordance with my 
invention, an omnidirectional antenna construction is provided which uses 
a planar radiation element equivalent to one wavelength of the central 
frequency being broadcast or transmitted. The antennas according to this 
invention are of a rectangular or frame construction and are provided with 
a short side and a long side element and the antenna has a feed point 
mounted at the long side. The ratio of the short side to the long side is 
between 1:4 and 1:8, and the length of the long side is identical to one 
wavelength of the central frequency of the radio wave being transmitted or 
received. A feeding means is located at about the central point of the 
long side and a short bar or conductor is mounted at a specific distance 
from both end points of the pair of long sides. The short sides are 
mounted on the left and right end points of the long sides and are 
symmetrical with respect to the central portion of the long side. The ends 
of the long side are bent at an angle of between 45 degrees to 90 degrees 
such that the end portion of the long side on the right-hand side (as 
shown in FIG. 1.) runs parallel to the end portion of the long side on the 
left. The bend on the left side at point A is at a specified distance from 
the central point and is identical to a distance at the bend at point B on 
the right side of the central point. In accordance with one antenna 
embodiment, the planar radiation element described above may be used with 
the horizontal or vertical wave polarization method. A first planar 
element of the type described above is located at the upper part of an 
upright insulation support column. A second planar element is spaced from 
the first planar element so as to correspond to a wavelength, or no less 
than one-half of a wavelength. The two spaced elements are also positioned 
so as to cross at an angle of 90 degrees with respect to each other and 
thereby resulting in an omnidirectional antenna. Such an omnidirectional 
antenna which uses a high-frequency distributor and such planar radiation 
elements enables simultaneous excitation either with the same phase for 
each element or with a phase difference of 90 degrees. 
In accordance with another embodiment, the long side frame planar radiation 
element is again equivalent to one wavelength of a central frequency of 
radio waves. The ratio of the length of the long side with that of the 
short side of the antenna element is between 1:4 and 1:8, and the long 
side is formed in the shape of a regular polygon with an odd number of 
angles. One part of the long side is bent at a central point "C" in the 
center of the long side to create the center of the regular polygon. A 
constant gap is provided via an insulation member deployed between both 
ends of said pair of long sides opposite the central point of the long 
side. A feed means is formed in the region of the C-point which is bent to 
a specific distance toward the inner side of the regular polygon of the 
central part of the long side. 
In accordance with another embodiment, the long side of the planar 
radiation element is equivalent to one-half wavelength rather than one 
wavelength, and has a regular polygon shape as discussed above. The ratio 
of the length of the long side to that of the short side of the element 
according to this embodiment is again between 1:4 and 1:8. 
In accordance with still another embodiment having a regular polygon-type 
construction, the long side is equal to one-fourth of the central 
wavelength and the short side is equal to one-twelfth. The end of the 
outer side of a spider coil is located one-third of the wavelength from 
the feed point.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
Referring now to FIGS. 1A and 1B, there are shown diagrams for explaining 
the basic elements of the construction of the omnidirectional antenna 
elements of this invention. FIGS. 1A and 1B show the construction of the 
antenna of this invention in accordance with one embodiment. The design is 
characterized by omnidirectionality with horizontal surface directionality 
which is approximately a circular shape. This results in a sufficiently 
decreased standing-wave ratio (hereinafter referred to as "SWR") so as to 
provide a very efficient antenna. FIG. 1A shows a front view and FIG. 1B 
shows a top view according to one embodiment of this invention. As shown 
in FIGS. 1A and 1B, the reference numeral 1 indicates the long side of the 
antenna element, and reference numeral 2 is the short side of the antenna 
element. The reference number 3 is a short or shorting bar, 4 is a 
refraction separation electro-conductive path (reflecting conductor), and 
reference numeral 5 is the feed point. Since the basic construction of the 
omnidirectional antenna of this invention as shown in FIG. 1 is two 
antenna elements, commonly called modified antenna elements, these two 
elements will be excited at the same time. Each end of the long side of 
the antenna receives one-half of the wavelength, while the short side of 
the antenna receives one-half to one-third of the wavelength received by 
the long side. The end of the long side element 1 closest to the short 
side antenna element 2 is provided with the short bar 3. This design of 
combining two modified antennas in this manner makes it possible to adjust 
the impedance to receive one wavelength at the selected frequency. The 
design also prevents reflected waves from being generated due to the close 
relationship between the feed point in the center of the radiating waves. 
In order to reduce SWR, the central part is bent at an angle of 45 degrees 
to 90 degrees with respect to the outer end of the flat frame as shown in 
FIG. 1B. The construction comprising short side 1 and long side 2 is 
further provided with refraction separation electro-conductive path 
(reflecting conductor) 4 and is 1/10th to 1/30th of the long side. Because 
feed point 5 is located in the geometrical center, a design is achieved 
which makes it possible to utilize centrally structured elements of 
multiple planar radiation elements equivalent to one wavelength and which 
are formed to enable excitation of two antenna elements located at a 
symmetrical distance as viewed from the feed point. 
Since the composite one-wavelength-element of the antenna of this invention 
consists of two parts which are linked in the center as shown in FIGS. 1A 
and 1B, the antenna has horizontal omnidirectional radiation 
characteristics which are almost circular. FIG. 2 shows the almost 
circular results from actual measurements or observations of the 
horizontal plane pattern of the one wavelength planar radiation element 
according to the teachings of this invention. In the example of FIG. 2, 
axes X and Y indicate the respective gains and the horizontal plane 
directional characteristics. Further, FIG. 3 is a diagram showing the 
changes of the SWR between 1500 MHz and 2500 MHz for an antenna element 
having a long side equivalent to one wavelength at 1900 MHz. Axis X 
indicates a frequency and axis Y indicates SWR. As shown, the SWR was 
significantly reduced when the frequency was 1900 MHz. 
The antenna construction shown in FIGS. 4A and 4B and FIGS. 5A and 5B 
discussed below has almost complete omnidirectional characteristics in the 
vertical polarized wave mode and in the horizontally polarized wave mode, 
respectively, thereby providing a very efficient antenna. 
FIGS. 4A and 4B show an embodiment of the vertical polarization mode of an 
omnidirectional antenna in accordance with the present invention. FIG. 4A 
shows a front view, while FIG. 4B shows a top view. As shown in FIGS. 4A 
and 4B, reference number 6 represents an insulation support column, 
reference number 7 is a first feed cable, reference number 8 is an 
integrated feed circuit or a distributor, reference number 9 is a second 
feed cable, reference number 10 (two places) is a one-wavelength planar 
radiation element according to the teachings of this invention, and 
reference number 11 is the base part to support insulation column 6. 
When a one-wavelength planar radiation element 10 is used with 
omnidirectional characteristics in the vertical polarization mode as shown 
in FIGS. 4A and 4B, one element 10 is mounted in the upper part of the 
insulation support column 6 and a second element 10 is deployed at a 90 
degree angle with respect to the first element 10 and is also spaced 
approximately one wavelength from the first element 10. These two elements 
are connected with a cable 7 to integration feed or distribution circuit 8 
with a feed or primary cable length equal to an odd numbered of 
1/4-wavelengths. The cable 7 will be a 75 ohm cable. A secondary 50-ohm or 
standard feed cable 9 having a length of even numbers of 1/2-wavelengths 
is connected to a transmitter-receiver (not shown). 
FIGS. 5A and 5B show side and top views, respectively, of an embodiment of 
the omnidirectional antenna of this invention in the horizontally 
polarized mode. As shown in FIG. 5A, 6 is an insulation support column, 7 
is a primary feed cable, 8 is an integration feed cable (distributor), 9 
is a secondary feed cable, 10 is a one-wavelength planar radiation element 
according to the teachings of this invention, and 11 is a base part for 
insulation support column 6. When the one-wavelength planar radiation 
element 10 is used with omnidirectional characteristics in the horizontal 
deflection mode as shown in FIG. 5, one element 10 is mounted in the upper 
part of insulation support column 6 and an identical element is at a 
crossing angle of 90 degrees to the first element 10 and with a spacing 
therebetween equivalent to one wavelength. These two elements are 
connected respectively to integration feed circuit 8 (distributor), the 
primary feed cable 7, and with the secondary cable 9 to a 
receiver-transmitter with the cable linking as described with respect to 
FIGS. 4A and 4B. When two elements spaced at different vertical locations 
are excited at the same time, it is possible to obtain almost completely 
non-directional characteristics having a horizontal plane pattern. 
In the embodiments of FIGS. 5A and 5B, the set interval between the upper 
and lower one-wavelength planar radiation element must be at least equal 
to 1/2wavelength with the same polarization, the same frequency, and the 
same polarity (phase). 
FIG. 6 shows an embodiment wherein three 1-wavelength planar radiation 
elements are deployed with sequential one-wavelength intervals for band A, 
band B, and band C in the vertical direction. The embodiment is designed 
for multiple station broadcasting at different high frequencies. Examples 
of such broadcasting include retransmission (with a repeater equipment) or 
relay use, or for multi-band use. In this case, antennas 12, 13, and 14 
are one-wavelength planar radiation elements corresponding to the central 
frequencies of bands A, B, and C. It is also possible to utilize the same 
method with a super-gain design for broadcasting the same signal at the 
same frequency with multiple stages. 
Although the deflection mode of waves will correspond to the input 
direction of a high-frequency current in the feed point, this standard 
antenna arrangement also makes it possible to add a small amount of 
polarized diversity characteristics through the changes of the 
vertical-horizontal ratio of the antenna elements. For example, with a 
vertical-horizontal ratio of each individual element of 1:3, it is about 
20 percent. With a ratio of 1:2, proper polarization diversity 
characteristics will be created. 
A further embodiment of this invention as shown in FIGS. 7A and 7B 
indicates an embodiment wherein reflecting plate 15 is deployed with an 
element in the horizontal polarization mode. The reflecting plate 15 has 
an angle of 90 degrees behind the element. The element may vary between 90 
degrees (as shown) up to 120 degrees (not shown). It will be appreciated 
that it is desirable to provide this reflecting plate with a grid-like or 
perforated construction in order to reduce wind pressure. If the element 
is properly located and the angle of the reflection plate is correct, it 
is possible to achieve precise control over the covered area. Thus, it 
will be appreciated that this method is also effective for reception for 
use with mobile units. FIG. 8A shows a front view, while FIG. 8B shows a 
top view of still another embodiment of this invention. In addition, FIG. 
8C shows a perspective view. As shown in FIGS. 8A, 8B, and 8C, reference 
number 16 represents the long side of the antenna element, reference 
number 17 provides a conductive path, reference number 18 is the feed 
point or box, reference number 19 is the short side of the antenna element 
reference number 20 is a spacer or gap-fixing member, reference number 21 
is an insulation support column, reference number 22 is a cross-mount 
insulation member, reference number 23 is an insulation-type feed point, 
and reference number 24 is a short bar. Further, the design completely 
prevents problems related to directional characteristics and changes in 
the position of the two parties in communication with each other. 
According to this embodiment, the long side of the antenna element is in 
the shape of a regular pentagon, wherein the total length of the entire 
periphery of the long side of the antenna element equals the length of one 
wavelength of the central frequency being received or transmitted. On one 
end, a part 19 is folded toward the outer side and is the short side of 
the antenna. This end part is fixed in place by insulation member 20. Feed 
point 23 is deployed in an extended part of conductive path 17, which is 
folded toward the inner side. This creates a construction in which 
reflection waves are eliminated. The short bars 24 are located near the 
ends of long side 16 and are of a slidable design. This enables movement 
of the elements in the vertical direction and adjustment to the left and 
right to enable tuning. The gain of this antenna can reach 5.5 db and its 
SWR can be adjusted to almost 1.1. The direction characteristics of this 
design are substantially circular such that changes of the position of the 
two communication parties does not create problems. Since the short bar is 
mounted at a location in the vicinity of about 30 percent of the 
peripheral length of the long side, the antenna element is adjustable and 
energizing is enabled in the vertical direction while an adjustment can 
also be performed to the left and to the right. The gain of this antenna 
can reach 3.5 db, and thanks to its right circular construction, its 
directional characteristics are such that changes of the respective 
positions of the communication parties create no problems whatsoever. In 
addition, because the SWR is reduced, the antenna achieves high gain even 
with a somewhat broad frequency width. 
According to the embodiment in FIG. 9, reference numeral 1 represents the 
long side of the antenna element, reference numeral 2 represents the short 
side of the antenna element, reference numeral 3 is a short bar, reference 
numeral 4 is a feed path, reference numeral 25 is a spider coil, and 
reference numeral 5 is a feed point. According to this embodiment, long 
side 1 corresponds to one-fourth of a wavelength, and antenna element 
short side 2 corresponds to one-twelfth of a wavelength. Short bar 3 is 
provided on the side that is close to the short side of the antenna 
element and in order to enable an adjustment of the impedance by relative 
movement of the two long sides, coil 25 is wound along its length which 
corresponds to one-third of a wavelength. A compact-type planar radiation 
antenna element connected to such a coil and having the same construction 
as the basis construction shown in FIG. 8 makes it possible to attain an 
even more compact design of an omnidirectional antenna. 
Thus, as has been explained above, this invention makes it possible to 
solve the problems of conventional radio antennas for transmission of 
radio waves which can be used for relay, broadcasting, communication, and 
other purposes. The antenna of this invention makes it possible to select 
at will any directional characteristics of horizontally polarized waves, 
vertically polarized waves, or a suitable polarized wave composition. 
These directional characteristics realize non-directional characteristics 
of an antenna with a nearly completely horizontal plane. In addition, 
since the terminal of this antenna is an open type of terminal, it offers 
little resistance to wind pressure thereby resulting in strong resistance 
to wind damage. 
This antenna is further characterized by the fact that it can operate at a 
relatively lower height than an antenna mounted on a dipole or a ground 
pole, and the reflection angle of the wave is much lower than that of a 
ground pole or dipole. Further, because the antenna can be set up with one 
mast, use of the antenna can be sequentially changed while the antenna is 
operated. Another characteristic of this antenna is that it can be used 
for multi-bands or multi-stations. Since grounding is not required 
regardless of the wave band which is used, no grounding rod is necessary. 
This makes the antenna easy to use and carry (via ship, a plane, a rocket, 
etc.). 
Another extremely effective feature of this invention is the fact that all 
of the above-described advantages and characteristics can easily be 
realized in the UHF band with a compact antenna. Moreover, when this 
antenna is used in the horizontal polarized mode, errors are greatly 
reduced during transmission of digital information while also enabling a 
complete control over the covered area. 
The corresponding structures, materials, acts, and equivalents of all means 
or step plus function elements in the claims below are intended to include 
any structure, material, or act for performing the function in combination 
with other claimed elements as specifically claimed.