Omni-directional antenna arrays and methods of making the same

Details Omni-directional antenna arrays and methods of making the same Omni-directional antenna arrays and methods of making the same

2003-01-15

2004-08-10

Nguyen, Hoang V. (Department: 2821)

Communications: radio wave antennas

Antennas

Microstrip

C343S790000

Reexamination Certificate

active

06774855

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to antenna arrays and, more particularly, to omni-directional antenna arrays.
BACKGROUND OF THE INVENTION
Radio frequency antennas are often designed as arrays to provide sufficient gain. The power feed network associated with antenna arrays, however, is often complex. The power feed network is complex because antenna pattern and gain depend on physical and network parameters. Some physical parameters include the number of elements and their spacing. Some feed network parameters include the phase and amplitude of the power signal at each of the antenna feeds as well as the impedance of the feed network delivering the power.
One omni-directional antenna array that has a relatively non-complex feed network is a co-linear coaxial antenna array.
FIG. 1
shows a conventional co-linear coaxial (COCO) antenna array
100
. COCO antenna
100
comprises a feed coax cable section
102
, a plurality of coax cable sections
104
, and a termination coax cable section
106
. Connecting each section of coax
102
,
104
, and
106
is a wire pair
108
. Wire pair
108
includes a center wire to shield wire
108
a
and a shield wire to center wire
108
b
. A power feed
110
is connected between feed coax cable section
102
and the first of the plurality of coax cable sections
104
. Power feed
110
has a connection
110
a
to the shield of feed coax cable section
102
and a connection
110
b
to the shield of the first of the plurality of coax cable sections
104
. Connection
110
a
runs to a short connection
112
internal to feed coax cable section
102
, which also connects power to the center wire
114
of feed coax cable section
102
. Termination coax cable section
106
similarly has a center wire
116
connected to a short
118
. Other than the power feed
110
connection, feed coax cable section
102
and termination coax cable section
106
are images of each other. (Notice, determining lengths of the coaxial cable and other dimensions of the COCO antenna
100
are well known in the art and will not be explained further herein.)
The coax cable can be any conventional coax cable such as 50 ohm or 75 ohm coax cable. The coax cable can be flexible or in a semi-rigid sheath. Using 50 ohm cable, a ¼ wave transformer may be needed in the power feed coax cable section
110
. The cable sections
102
,
104
, and
106
are stripped and soldered to wire pairs
108
to make the connections. Moreover, the shorts
112
and
118
are located and soldered. The above example, and the description of the present invention, below, relate to conventional 50 ohm coax cable, but one of skill in the art would recognize other cable or radiating elements are possible.
The COCO antenna
100
provides an omni-directional RF antenna with a good power gain for lower frequency operation. However, the conventional COCO antenna
100
, explained above, has several problems. The problems include: the construct is fragile, the electrical connections have defects, the solder placement lacks consistency, and the coax stripping is inconsistent. In general, the conventional COCO antenna
100
has a minimum error associated with its construction and handling the assembly is difficult. While these manufacturing and assembly errors can be tolerated at lower operating frequencies, at higher frequencies, such as the 5 GHz range, the errors become prohibitive. The prohibitive nature of the errors is due, in part, to the smaller lengths of coax and wires used. As the frequency increases, the wavelength, and the lengths of each section decrease. The smaller lengths of wire make the errors relatively higher, causing unacceptable degradation of the antenna pattern and gain. Also, the fragile nature of the conventional COCO antenna (coax cable sections soldered together) makes handling and assembly of the construct difficult if not prohibitive.
Thus, it would be desirous to provide a COCO antenna that had lower errors and was less fragile.
SUMMARY OF THE INVENTION
To attain the advantages of and in accordance with the purpose of the present invention, a support for an omni-directional antenna is provided. The support comprises a substrate with pre-placed transition pads and a feed pad. Coaxial cable could be soldered to the transition pads to form a co-linear coaxial antenna array.
The present invention further provides methods for designing the support including arrangement of transition pads on a substrate. A feed transition pad is also arranged on the substrate. Coaxial cable attached to the substrate at the transition pads would form a co-linear coaxial antenna array.
The foregoing and other features, utilities and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings.


REFERENCES:
patent: 3031668 (1962-04-01), Bryson
patent: 5285211 (1994-02-01), Herper et al.
patent: 5926149 (1999-07-01), Rummeli et al.
patent: 5963168 (1999-10-01), Brennan

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