Patent Grant
9912079
The present invention relates generally to antenna systems utilized in Wi-Fi devices, and more particularly, to a distributed omni-directional dual-band antenna system for use in smaller Wi-Fi devices.
The use of wireless communication devices for data networking is growing at a rapid pace. Data networks that use “Wi-Fi” (“Wireless Fidelity”) are relatively easy to install, convenient to use, and supported by the IEEE 802.11 standard. Wi-Fi data networks also provide performance that makes Wi-Fi a suitable alternative to a wired data network for many business and home users.
Wi-Fi networks operate by employing wireless access points that provide users, having wireless (or “client”) devices in proximity to the access point, with access to varying types of data networks such as, for example, an Ethernet network or the Internet. The wireless access points may include one or more radios that operate according to one of three standards specified in different sections of the IEEE 802.11 specification. Generally, radios in the access points communicate with client devices by utilizing omni-directional antennas that allow the radios to communicate with client devices in any direction. The access points are then connected (by hardwired connections) to a data network system that completes the access of the client device to the data network.
The three standards that define the radio configurations are:
1. IEEE 802.11a, which operates on the 5 GHz frequency band with data rates of up to 54 Mbs;
2. IEEE 802.11b, which operates on the 2.4 GHz frequency band with data rates of up to 11 Mbs; and
3. IEEE 802.11g, which operates on the 2.4 GHz frequency band with data rates of up to 54 Mbs.
The 802.11b and 802.11g standards provide for some degree of interoperability. Devices that conform to the 802.11b standard may communicate with 802.11g access points. This interoperability comes at a cost as access points will switch to the lower data rate of 802.11b if any 802.11b devices are connected. Devices that conform to the 802.11a standard may not communicate with either 802.11b or 802.11g access points. In addition, while the 802.11a standard provides for higher overall performance, 802.11a access points have a more limited range of approximately 60 feet compared with the approximate 300 feet range offered by 802.11b or 802.11g access points.
Each standard defines ‘channels’ that wireless devices, or clients, use when communicating with an access point. The 802.11b and 802.11g standards each allow for 14 channels. The 802.11a standard allows for 23 channels. The 14 channels provided by the 802.11b and 802.11g standards include only 3 channels that are not overlapping. The 12 channels provided by the 802.11a standard are non-overlapping channels.
Access points provide service to a limited number of users. Access points are assigned a channel on which to communicate. Each channel allows a recommended maximum of 64 clients to communicate with the access point. In addition, access points must be spaced apart strategically to reduce the chance of interference, either between access points tuned to the same channel, or to overlapping channels. In addition, channels are shared. Only one user may occupy the channel at any given time. As users are added to a channel, each user must wait longer for access to the channel thereby degrading throughput.
Another degradation of throughput as the number of clients grows is the result of the use of omni-directional antennas. Unfortunately, current access point technology employs typically one or two radios in close proximity that results in interference, which reduces throughput. In an example of a two radio access point, both radios may be utilized as access points (i.e., each radio communicates with a different client device) or one radio may function as the access point while the other radio functions as a backhaul, i.e., a communication channel from the access point to a network backbone, central site, and/or other access point. Typically, the interference resulting from the different antennas utilized with these radios limits the total throughput available and, as a result, reduces traffic efficiency at the access point.
In existing Wi-Fi technologies, there is a need to deploy mesh-like networks of access points to increase the coverage area of a Wi-Fi communication system. As the number of access points increases so does the complexity of implementing the communication system. Therefore, there is a need for a radio and antenna architecture capable of operating in mesh-like networks of access points without causing radio interference that reduces the throughput of the network.
Unfortunately, because of the compact size of access points in Wi-Fi communication systems, it may be difficult to design antennas that are capable of providing the coverage needed by these types of systems, especially when omni-directional coverage is needed. As an example, when deploying an access point with omni-directional coverage using omni-directional antennas, the azimuth coverage is distorted due to the presence of the antennas and their overlapping radiation patterns. Due to the fact that there are two radios that could be operating in a 2×2, 3×3, or 4×4 architecture, there may be 4, 6, or 8 antennas, respectively, used in a small volume. The close proximity of these antennas will affect the isolation between the antennas and the radios, preventing them from coexisting while operating at, for example, a 5 GHz band. Therefore, there is a need for a distributed omni-directional dual-band antenna system with improved isolation between antennas for use in a Wi-Fi access point.
In view of the above, a distributed broadband omni-directional dual-band antenna system for use in a Wi-Fi access point (AP) is described. The distributed broadband omni-directional dual-band antenna system may include an antenna array that includes 4, 6, or 8 antennas arranged in a circular array fashion along the perimeter of the Wi-Fi AP. Each antenna may be associated with a single Wi-Fi radio of the AP, and each of the antennas for the different radios are interleaved in order to provide omni-directional coverage with minimal distortion; that is, each antenna of the AP is alternated with antennas for different radios. Each antenna element in the array may be a broadband (3.5 to 7 GHz) dual-band (2.4 and 5-6 GHz) antenna and may also be semi-directional.
The elevation coverage of this monopole antenna is forward looking, that is, its main beam is more energy-focused along its main axis. This forward looking feature increases the isolation between the antennas and thus indirectly the isolation between the radios. The antenna gain in the 2.4 and 5 GHz bands may be 2-5 dB. The isolation between any antenna element in the array is high, reaching, for example, approximately 40 dB at the 5 GHz band. This high isolation between the antennas enables the two radios in the AP to coexist with each other.
Having the antennas interleaved creates an effect of distributed omni-directional coverage, where the two or three antennas connected to a specific radio form an omni-directional coverage for the AP. The antenna element may be a dual-band monopole antenna mounted on a ground plane. The ground plane may deflect the pattern down by about 10 degrees maximizing coverage below the antenna. The monopole element may also have a reflector behind it to enhance its directivity. The reflector may be a continuous metallic wall or a single wire reflector. The AP may be an integrated assembly and by properly designing its printed circuit board (PCB), antenna performance will not be affected by the presence of other components of the AP.
An improved design of a compact broadband microstrip-fed printed monopole antenna for use in the distributed omni-directional dual-band antenna system is also disclosed. The shape of the radiating elements of the microstrip-fed printed monopole antenna may be described as “a flared notch with folded stub.” This monopole antenna generates a directional beam where the peak of the gain is along the main axis of the antenna where the peak gain may be 5.0 dBi and 2.8 dBi at 2.45 and 5 GHz, respectively.
Other systems, methods and features of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.
The examples of the invention described below can be better understood with reference to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views.
In the following description of example embodiments, reference is made to the accompanying drawings that form a part of the description, and which show, by way of illustration, specific example embodiments in which the invention may be practiced. Other embodiments may be utilized and structural changes may be made without departing from the scope of the invention.
In general, a distributed omni-directional dual-band antenna system for use in a Wi-Fi access point is described. The distributed omni-directional dual-band antenna system includes an antenna array that may include 4, 6, or 8 antennas arranged in a circular array fashion along the Wi-Fi access point. Each antenna may be associated with a different Wi-Fi radio. The antennas for the different radios are interleaved (see
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The monopole elements may also have a reflector behind it to enhance its directivity. The reflector could be a continuous metallic wall or a single wire reflector (see
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The antenna gain may be in the 2.4 and 5 GHz bands may 2-5 dB. The isolation between any antenna in the array of antennas is high, reaching, for example, approximately 40 dB at the 5 GHz band. The high isolation between these antennas enables the two radios in the AP to coexist with each other. By having the antennas interleaved, it creates an effect of distributed omni-coverage, where the two or three antennas connected to a specific radio forms an omni-directional coverage.
It will be understood that the foregoing description of numerous implementations has been presented for purposes of illustration and description. It is not exhaustive and does not limit the claimed inventions to the precise forms disclosed. For example, the above examples have been described as implemented according to IEEE 802.11a and 802.11bg. Other implementations may use other standards. In addition, examples of the wireless access points described above may use housings of different shapes, not just a round housing. The number of radios in the sectors and the number of sectors defined for any given implementation may also be different. Modifications and variations are possible in light of the above description or may be acquired from practicing the invention. The claims and their equivalents define the scope of the invention.
This application claims priority of United States (“U.S.”) Provisional Patent Application Ser. No. 62/020,856, entitled “Distributed Omni-Dual Band Antenna System for a Wi-Fi Access Point,” filed on Jul. 3, 2014, to inventor Abraham Hartenstein, the disclosure of which is incorporated by reference herein in its entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20040027309 | Swarup | Feb 2004 | A1 |
| 20060109067 | Shtrom | May 2006 | A1 |
| 20100119002 | Hartenstein | May 2010 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20160043478 A1 | Feb 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62020856 | Jul 2014 | US |
