The present invention relates generally to wireless communications systems and more particularly to a hooked stub collinear antenna and a method for making the same.
For a wireless communications system, an omni-directional antenna is often desirable such that the coverage area, i.e., transmission and/or reception, is generally uniform in all azimuth directions relative to the location of the antenna. As a particular example, for wireless network access points and bridges, an antenna having an omni-directional pattern with vertical polarization characteristics, a uniform horizontal plane pattern, low cross-polarization characteristics, and moderate gain, e.g., 5 to 10 decibels referenced to an isotropic radiator (5 to 10 dBi), and with greater than five percent bandwidth is desirable.
A number of approaches are commonly used to implement omni-directional antennas. More specifically, these approaches often use collinear aperture fed arrays, periodic loaded structures, or periodic sleeve dipoles. Generally, omni-directional antennas implemented using any one of these approaches include many parts, and are often fragile and difficult to manufacture. These antennas also typically have narrow bandwidths. For example, wire helix sections typically include many parts and are fragile and difficult to construct, having bandwidths less than five percent. Furthermore, wire stub sections generally have asymmetrical horizontal plane symmetry and narrow bandwidths. Approaches including a variety of periodic aperture fed or loaded structures printed on circuit board materials are easy to fabricate and are rugged. However, an omni-directional antenna using periodic aperture fed or loaded structures printed on one or more circuit boards typically lacks horizontal plane symmetry.
Thus, there exists a need for an omni-directional antenna with vertical polarization characteristics, a uniform horizontal plane pattern, low cross-polarization characteristics, and moderate gain, with greater than five percent bandwidth. Moreover, such an omni-directional antenna should be easy to manufacture.
The present invention provides an omni-directional antenna with vertical polarization characteristics, a uniform horizontal plane pattern, low cross-polarization characteristics, and moderate gain, with greater than five percent bandwidth. Moreover, the omni-directional antenna of the present invention is easy to manufacture.
In accordance with the present invention there is disclosed herein a hooked stub collinear array antenna formed from a single conductor. The antenna operates at a design frequency having an associated wavelength. The antenna includes a plurality of radiating elements that are substantially one half the wavelength. The radiating elements are aligned with a longitudinal axis of the antenna. The antenna further includes a delay element connected between each of the plurality of radiating elements. The delay element is aligned with a transverse axis approximately ninety degrees from the longitudinal axis. The delay element extends approximately one quarter of the wavelength from the longitudinal axis. The total length of the delay element is approximately one half the wavelength.
In accordance with yet another aspect of the present invention, the proximal ends of the delay elements extend along a transverse axis and are serially rotated ninety degrees in ether a clockwise or counter clockwise direction.
In accordance with yet another aspect of the present invention, the delay elements are substantially similar. Furthermore, the delay elements are symmetric about and substantially perpendicular to the longitudinal axis.
Further in accordance with the present invention there is disclosed herein another hooked stub collinear array antenna formed from a single conductor and configured to operate at a design frequency having a wavelength. The antenna includes a plurality of radiating elements that are substantially one half the wavelength in length and aligned with a vertical axis and a delay element connected between each of the plurality of radiating elements. The delay elements are aligned with a horizontal axis approximately ninety degrees from the vertical axis extending approximately one quarter of the wavelength. The total length of the delay element is approximately one half the wavelength.
In accordance with yet another aspect of the present invention, the delay elements are symmetric about and substantially perpendicular to the vertical axis.
By virtue of the foregoing, there is thus provided an omni-directional antenna with vertical polarization characteristics, a uniform horizontal plane pattern, low cross-polarization characteristics, and moderate gain, with greater than five percent bandwidth that is easy to manufacture.
The advantages of this configuration lie in the construction. In a preferred embodiment, a single conductor is used. Thus, there is one part. The plethora of pieces normally associated with a collinear array is reduced to a single wire with multiple bends. The resultant antenna has excellent horizontal plane symmetry, is compact in its “diameter”, is low loss, and has no connections other than at a single feed point, resulting in high reliability. Furthermore, the array is scalable to the extent that more elements provide more gain, with each added set adding incremental gain, up to a limit on the order of twenty elements, which is a general characteristic of collinear arrays.
These and other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the best modes suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modifications in various obvious aspects all without departing from the spirit of the present invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the present invention.
With reference to
f=c/λ,
where f is the center frequency, λ is the wavelength, and c is the speed of light. Antenna 10 is comprised of a plurality of radiating elements 14a–d. The radiating elements 14a–d are substantially one half wavelength in length, and are aligned with a longitudinal axis, generally indicated by the centerline found at reference numeral 16. A delay element 18a–d is connected between each of the plurality of radiating elements 14a–d. The delay elements 18a–d are aligned with a transverse axis, an exemplary one of which is indicated at reference numeral 20a, approximately ninety degrees from the longitudinal axis 16. The delay elements 18a–d extend approximately one quarter of the wavelength (λ/4), as best shown in shown in
As shown in
Ideally, and as will be shown hereinafter, the delay elements are square. That is to say that the delay elements have no curvature or radius (r). However, because the antenna 10 and the delay elements 18a–d are formed from a single conductor 12, this is physically impractical. Thus, some radius (r) results from the formation of the delay elements 18a–d in the single conductor 12. In accordance with one aspect of the present invention, the antenna 10 is very forgiving of the shape of the delay elements 18a–d. Thus, the exact shape of the bends of delay elements 18a–d is not critical; however, each delay element 18a–d is similarly shaped to cancel out, for example, asymmetrical radiation exhibited by the antenna 10. Those of ordinary skill in the art will appreciated that the pattern function of the antenna 10 would be likewise effected.
Also ideally, the height (h) of each delay element 18a–d is near zero. However, this is physically impossible. Thus, the height (h), like the radius (r), is much less than the wavelength (λ), h<<λ.
Thus, referring to
With reference to
Again, the total length of each delay element 108a–n is approximately equal to the wavelength (λ) divided by two, or λ/2. The exact shape of the delay elements 108a–n is not critical. However, each delay element 108a–n is similarly configured and serially rotated ninety degrees. As will be shown in
In the embodiment 100 shown in
More specifically, for delay element 108b, segment 112a extends at a right angle from radiating element 106b. Segment 112b continues from segment 112a, and is also at a right angle to radiating element 106b and segment 112a. Segment 112c continues at a right angle from segment 112b, and is likewise at a right angle to radiating element 106b. Segment 112d continues in-line or linearly from segment 112c, at a right angle to radiating element 106b. Segment 112e continues at a right angle from segment 112d in parallel with radiating element 106b. Segment 112f continues at a right angle from segment 112e, and is also aright angle to radiating element 106b. Segment 112g continues linearly from segment 112f, at a right angle to radiating element 106b. Segment 112h continues at a right angle from segment 112g, and is at a right angle to radiating element 106b. Segment 112i continues at a right angle from segment 112h, and is a right angle to radiating element 106b. Radiating element 106c continues on from segment 112i, at a right angle, and is in-line with radiating element 106b. Thus, segments 112a–i comprise a delay element 108a that is substantially rectangular in shape. Moreover, segments 112a–i form a delay element 108b that doubles back on itself to widen the bandwidth of the antenna 100.
As also shown in
Still referring to
It should also be appreciated that a feed (not shown) is attached to the bottom or end 116 of wire 114. For example, a feed is suitably a wire, such as a coaxial cable, or a connector, such as a bayonet or threaded connection type.
A novel aspect of the present invention is the construction or method of making a hooked stub collinear array antenna. For example, an antenna 110 is formed from a single wire 114. Referring also to
In addition, the array 102 is scalable to the extent that more radiating elements 106a–n provides more gain, with each added set of four radiating and delay elements 106a–n, 108a–n adding incremental gain, up to a limit on the order of twenty elements, a general characteristic of collinear arrays. The following table shows the typical relationship between peak gain and the number of elements (n), using an antenna with eight elements, e.g., n=8, as a reference.
For example, as shown in the first row of data, the antenna including eight elements has a peak gain of 10.47 decibels (dB) at a frequency of 5,450 Megahertz (MHz) and a length of 0.2860 meters. As shown in the left and right most columns, little additional gain is afforded by increasing the number of elements beyond twenty.
By virtue of the foregoing, there is thus provided an omni-directional antenna with vertical polarization characteristics, a uniform horizontal plane pattern, low cross-polarization characteristics, and moderate gain, with greater than five percent bandwidth. Moreover, such an omni-directional antenna is easy to manufacture.
While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. It will be understood that the present invention is applicable to any elongated electrically conductive structure. Moreover, such an antenna is not limited to uses in any particular frequency band; but rather, may be designed for and operate at any frequency as desired. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicants' general inventive concept.
Number | Name | Date | Kind |
---|---|---|---|
2380333 | Scheldorf | Jul 1945 | A |
3680147 | Redlich | Jul 1972 | A |
4031537 | Alford | Jun 1977 | A |
4160978 | DuHamel | Jul 1979 | A |
4250509 | Collins | Feb 1981 | A |
4872021 | Tabakov et al. | Oct 1989 | A |
6005530 | Jovanovich et al. | Dec 1999 | A |
6529171 | Le Balier et al. | Mar 2003 | B1 |
6717555 | Teillet et al. | Apr 2004 | B1 |
6919859 | McCarthy et al. | Jul 2005 | B1 |
Number | Date | Country | |
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20060139229 A1 | Jun 2006 | US |