Example embodiments generally relate to wireless communications and, more particularly, relate to an antenna element that provides increased gain toward the horizon.
High speed data communications and the devices that enable such communications have become ubiquitous in modern society. These devices make many users capable of maintaining nearly continuous connectivity to the Internet and other communication networks. Although these high speed data connections are available through telephone lines, cable modems or other such devices that have a physical wired connection, wireless connections have revolutionized our ability to stay connected without sacrificing mobility.
However, in spite of the familiarity that people have with remaining continuously connected to networks while on the ground, people generally understand that easy and/or cheap connectivity will tend to stop once an aircraft is boarded. Aviation platforms have still not become easily and cheaply connected to communication networks, at least for the passengers onboard. Attempts to stay connected in the air are typically costly and have bandwidth limitations or high latency problems. Moreover, passengers willing to deal with the expense and issues presented by aircraft communication capabilities are often limited to very specific communication modes that are supported by the rigid communication architecture provided on the aircraft.
Conventional ground based communication systems have been developed and matured over the past couple of decades. While advances continue to be made in relation to ground based communication, and one might expect that some of those advances may also be applicable to communication with aviation platforms, the fact that conventional ground based communication involves a two dimensional coverage paradigm and that air-to-ground (ATG) communication is a three dimensional problem means that there is not a direct correlation between the two environments. Instead, many additional factors must be considered in the context of ATG relative to those considered in relation to ground based communication.
One such area in which further consideration may be required relates to the antennas employed for ATG network communications. A typical aerial antenna includes a flush-mounted (e.g. cavity, patch, and slot) element or an above-surface (e.g. monopole and dipole) configuration. In order to reduce or minimize aerial resistance (drag), a low mechanical form factor is also generally desirable. Accordingly, above-surface antennas are typically designed to provide a relatively broad area of coverage with a relatively low-gain. Thus, above-surface antennas are frequently constructed using ¼-wave, vertically-polarized monopole antennas or elevated horizontally-polarized dipoles. However, as wireless communications become a commercial necessity that demands that better and more cost effective service be provided to airborne passengers, the costs and performance capabilities of networks supported by such antennas may render such networks incapable of meeting consumer demands.
Some example embodiments may therefore be provided to provide antenna configurations that provide improved characteristics which, when translated into network usage, may improve network performance so that ATG networks can perform at expected levels within reasonable cost structures. In some embodiments, an omni-directional antenna configuration may be provided that can increase gain toward the horizon. Some embodiments may also improve bandwidth via modification of antenna elements. Accordingly, for example, signal coverage may be improved with relatively low cost equipment since fewer base stations may be needed to accommodate antennas that have omni-directional performance with a relatively high gain.
In one example embodiment, an air-to-ground network communication device is provided. The device may include a conductive groundplane and an antenna element. The conductive groundplane may be disposed to be substantially parallel to a surface of the earth. The antenna element may extend substantially perpendicularly away from the groundplane and may have an effective length between about 1λ to about 1.5λ. The antenna element may be disposed at a distance of about 0.5λ to about 1λ from the groundplane.
In another example embodiment, a mobile platform is provided. The mobile platform includes a conductive groundplane and an antenna element. The conductive groundplane may be disposed to be substantially parallel to a surface of the earth while the mobile platform is in motion. The antenna element may extend substantially perpendicularly away from the groundplane and may have an effective length between about 1λ to about 1.5λ. The antenna element may be disposed at a distance of about 0.5λ to about 1λ from the groundplane.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
Some example embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all example embodiments are shown. Indeed, the examples described and pictured herein should not be construed as being limiting as to the scope, applicability or configuration of the present disclosure. Rather, these example embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout. Furthermore, as used herein, the term “or” is to be interpreted as a logical operator that results in true whenever one or more of its operands are true.
Some example embodiments described herein provide architectures for improved antenna design. In this regard, some example embodiments may provide for an antenna design that may provide improved gain toward the horizon in an omni-directional structure. The improved gain toward the horizon may enable aircraft to engage in communications with potentially distant base stations on the ground. Accordingly, an ATG network may potentially be built with base stations that are much farther apart than the typical distance between base stations in a terrestrial network.
Conventional antennas are formed by embedding conductors of structured shapes within a surrounding medium. The surrounding medium can be air or other non-conducting (insulating) media. The resulting local fields and currents in response to the differently shaped material properties and alternating currents applied to the antenna input ports determine the direction and polarization of radiated fields as well as the observed frequency dependent impedance at the antenna port. A class of antennas that is used often is that of linear antennas such as straight monopole or dipole elements. These elements are often sized such that their length is approximately ½ of the wavelength (½λ) of the resonant frequency of the antenna, and as such they become resonant. At this resonance the input impedance is purely real and the reactive component vanishes. This is convenient as the antenna can be directly connected to a transmission line and the transmission line would not carry losses due to additional reactive fields or currents.
The geometry of vertically oriented linear antenna elements, and as such their radiating currents and fields, are generally independent of the azimuth angle of observation. Furthermore, the radiated or received field intensity (or directivity) of such elements is also independent of the azimuth angle. In other words, the radiation pattern is omni-directional (in azimuth) and has a characteristic radiation pattern in the elevation angle.
It should be understood that the directivity pattern shown in
The fuselage or wings of an aerial vehicle may be made of a conductive material (e.g., aluminum, conductive composite materials, etc.). Alternatively, for composite materials that are not conductive, a mesh or substrate of conductive material may be provided over or within the composite material forming the skin of the aerial vehicle. The conductive material may form a relatively large (e.g., approximately infinite) conductive groundplane. In cases in which the groundplane is very large compared to the wavelength of operation, a single monopole element may be considered to be equivalent to a single dipole element.
Further focusing of transmitted power or received sensitivity towards the horizon (antenna gain) can be achieved by stacking multiple elements in a broadside radiating antenna array. In the case of a dipole element 140 mounted at a distance h above (or below) the groundplane 110 as shown in
In the context of an ATG network, the directivity of a single element of ½-wavelength that is typically used may not be optimal. Instead, further broadside directivity and focusing towards the horizon may vastly improve the antenna performance so that favorable network characteristics can be achieved in terms of cost and bandwidth. Accordingly, some example embodiments may employ the use of longer antenna elements.
Accordingly, as can be appreciated from the combination of the content of
Longer element lengths, as provided in example embodiments, may be applied to any of the stacked element array schemes as illustrated in
It should also be appreciated that some alternative embodiments may employ other than end or center feed options relative to feeding the antenna 300 in order to minimize reactive components without the use of an impedance matcher 310. Moreover, some embodiments may employ a number of antenna elements that may be electrically connected or disconnected based on operator control or based on control decisions made by an antenna controller 330. The antenna controller 330 may include at least a processor and memory storing instructions for execution by the processor. The antenna controller 330 may be configured (e.g., via the instructions) to electrically connect or disconnect antenna elements in a desired arrangement within the antenna 300 based on operator control, current conditions or other predetermined criteria. The antenna controller 330 may also employ any needed internal portions or components of the impedance matcher 310 in order to provide cancellation of the reactive components associated with any particular selected antenna element configuration that is to be employed in the antenna 300.
Although any of the antenna element designs of
As shown in Table 1, the highest horizon gain (e.g., 11.1 dBi) is achieved by placing a dipole antenna having about a 1.2 lambda length above the groundplane by about 0.68 lambda. This corresponds to the example of
A radiation pattern 500 associated with the example antenna element 400 of
In describing example embodiments, relatively linear antenna elements (e.g., monopoles and dipoles) have been employed for illustrative purposes thus far. However, it should be appreciated that alternative embodiments may also employ other antenna element shapes and configurations. For example, conical, spherical and/or elliptical shaped curved surfaces may also be employed as antenna elements in some embodiments.
Embodiments that employ Vivaldi-antenna elements and/or the shapes described above may have improved impedance matching characteristics and broader operational bandwidth characteristics as compared to the monopole and dipole configurations. However, the element length parameters discussed above may still be effectively employed in order to improve directivity toward the horizon.
Accordingly, an example embodiment may provide an aircraft employing an antenna element with an effective length between about 1 to 1.5λ, at a distance of about 0.5 to about 1λ from a groundplane formed at or by the skin of the aircraft. In an example embodiment, the effective length may be about 1.2λ and the distance from the groundplane formed at or by the skin of the aircraft may be about 0.68%. As an example, for a 1 GHz signal, λ may be about 30 cm. The antenna element may be selected to have a length of L=36 cm (1.2λ). However, example embodiments may be practiced in connection with any number of different frequencies as well, and the lengths of antenna elements would be adjusted accordingly. For example, some embodiments may be practiced in connection with unlicensed communication bands (e.g., 2.4 GHz and 5.8 GHz), but any suitable frequencies may be employed. Antenna elements of example embodiments may enable superior directivity to be provided toward the horizon, and may also be duplicated at a ground transmission station either alone or in combination with other antenna elements that may provide coverage for vertical orientations.
In an example embodiment, an air-to-ground network communication device is provided. The device may include a conductive groundplane and an antenna element. The conductive groundplane may be disposed to be substantially parallel to a surface of the earth. The antenna element may extend substantially perpendicularly away from the groundplane and may have an effective length between about 1λ to about 1.5λ. The antenna element may be disposed at a distance of about 0.5λ to about 1λ from the groundplane.
In an example embodiment, the device may include additional, optional features, and/or the features described above may be modified or augmented. Each of the numbered modifications or augmentations below may be implemented independently or in combination with each other respective one of such modifications or augmentations, except where such combinations are mutually exclusive. Some examples of modifications, optional features and augmentations are described below. In this regard, for example, in some cases, (1) the effective length of the antenna element may be about 1.2λ and the distance from the groundplane is about 0.68λ. In some embodiments, (2) the groundplane may be formed at a skin of an aircraft. Alternatively, (3) the groundplane may be formed at a platform of a ground transmission station. In an example embodiment, (4) the antenna element may be a dipole element. The groundplane of some embodiments may extend at least 3 feet in every direction away from the antenna element. In some embodiments, (5) the antenna element comprises a Vivaldi-antenna. In an example embodiment, (6) the antenna element may include non-linear shaped elements such as conical, spherical or elliptical shaped elements. In some cases, (7) the device may further include an impedance matcher operably coupled to the antenna element to cancel reactive components of impedance of the antenna element. The impedance matcher may be operably coupled to an antenna controller that may be configured to enable modification of the impedance matcher to cancel different reactive component values associated with different switchable antenna element configurations of the antenna element. In an example embodiment, (8) the antenna element may include switchable components that are configured to be arranged in at least two different configurations that each have the effective length between about 1λ to about 1.5λ.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe exemplary embodiments in the context of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. In cases where advantages, benefits or solutions to problems are described herein, it should be appreciated that such advantages, benefits and/or solutions may be applicable to some example embodiments, but not necessarily all example embodiments. Thus, any advantages, benefits or solutions described herein should not be thought of as being critical, required or essential to all embodiments or to that which is claimed herein. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Number | Name | Date | Kind |
---|---|---|---|
5067172 | Schloemer | Nov 1991 | A |
7113780 | McKenna | Sep 2006 | B2 |
7920860 | Chari et al. | Apr 2011 | B2 |
8676192 | Jalali | Mar 2014 | B2 |
20140327577 | Ozaki | Nov 2014 | A1 |
Number | Date | Country | |
---|---|---|---|
20140266932 A1 | Sep 2014 | US |
Number | Date | Country | |
---|---|---|---|
61779100 | Mar 2013 | US |