Sectorizations

Technical Field

Base station antenna for mobile communications. Background Art

A common wireless communication network plan involves a base station serving three hexagonal shaped cells or sectors. This is often known as a three sector configuration. In a three sector configuration, a given base station antenna serves a 120° sector. Typically, a 60° Half Power Beam- width

(HPBW) antenna provides coverage for a 120° sector. Three of these 120° sectors provide 360° coverage. Other sectorization schemes may also be employed. For example, six, nine, and twelve sector sites have been proposed. Six sector sites may involve six directional base station antennas, each having a 30° HPBW antenna serving a 60° sector. Increasing the number of sectors increases system capacity because each antenna can service a smaller area. It is an ideal solution for high traffic sectors and events. It also provides the opportunity to switch beams in order to provide the best signal for the user (smart antenna). Furthermore, it offers the chance for coverage sculpting.

Moreover, it allows massive MIMO configurations. In order to further boost the capacity of multi-beam base station antennas, it may be desirable to simultaneously have both horizontal and vertical sectorizations. However, dividing a coverage area into smaller sectors has drawbacks because antennas covering narrow sectors generally have more radiating elements that are spaced wider than antennas covering wider sectors. For example, a typical 30° HPBW antenna is generally two times wider than a common 60° HPBW antenna. Thus, costs and space requirements increase as a cell is divided into a greater number of sectors. In some proposed solutions, a single multi-column array may be driven by a feed network to produce two or more beams from a single aperture [1], Very complicated antennas have been developed using multi-beam forming networks driving planar arrays of radiating elements, such as the Butler matrix. However, they have several potential disadvantages, such as significant beam width and beam position variations, high side lobes level. To overcome this, efforts have been made to make amplitude

distribution in antenna array depending on frequency either by using filters (which add complexity and about three times more components), or frequency dependent power dividers (which significantly reduces the bandwidth). Other classes of multi-beam antennas based on a classic Luneburg cylindrical lens have been tried. The Luneburg lenses [3]-[4] are composed of layered structures of dielectric concentric shells, each of a different refractive index. The cost of the classic Luneburg lens is high and the process of production is extremely complicated. Additionally, these antenna systems still suffer from the narrow frequency band- width. Some of the major disadvantages of the current multi-beam base station antennas are summarized as follows:

Disadvantages of the Current Multi-Beam Base Station Antennas:

• The currently used multi-beam technologies use several frequency dependent components and, therefore, they have low frequency bandwidths. None of them can cover the whole frequency band of 4G (LTE). The maximum covered bandwidth in the currently available multi-beam base station antennas is either (0.7-0.96 GHz) or (1.7-2.7 GHz).

• None of the currently available multi-beam base station antennas can

simultaneously combine horizontal and vertical sectorizations, which could double the number of beams, and in turn double the overall system capacity.

• The currently used multi-beam technologies are very complicated and they utilize many components. Hence, the currently available multi-beam base station antennas are not easy to manufacture and they have very high costs.

• The currently available multi-beam base station antennas are too heavy in

weight and, thus, they require very complicated heavy towers. They are also very difficult to install.

• In the currently available multi-beam base station antennas, all beams have to be tilted in the vertical plane by the same vertical tilt angle. In some of the available multi-beam antennas, the vertical tilt angle is even fixed such that all beams are either not tilted in the vertical plane or they are all tilted by a fixed specific tilt angle. • None of the currently available multi-beam base station antennas covers 180 degrees. They only cover 120 degrees or even less. Therefore, the whole azimuth (360 degrees) can be covered by at least three antennas or more (instead of two).

• In the currently used multi-beam base station antenna technology, it is almost impossible to simultaneously generate a single wide-beam that covers the whole sector (120 or 180 degrees) and multiple narrow beams. Hence, no unified version of the current base station antennas can be produced. Either a single wide beam antenna or multiple narrow beams antenna can be used. So, for any future new network needs and requirements, the whole base station has to be changed and replaced by another one. This may also require changing the tower.

• In the currently available technology, increasing the beamwidth causes the gain to be significantly reduced.

• In the currently used multi-beam base station antenna technology, there is no good opportunity for co-sitting.

• The currently used multi-beam base station antenna technology, does not provide a clear way of adding massive MIMO configurations.

• The currently available multi-beam base station antennas are only single task antennas (either a single wide beam or multi-narrow beams), regardless of the situation, the nature and the capacity of the covered sector, which may be different from week days to weekends or from day hours to night hours, etc. Thus, all the base station receiving/transmitting components and equipment have to keep working together all the time. This reduces their lifetime and does not allow any required maintenance and/or routine checkup. It also wastes power.

• In the currently available multi-beam base station antennas, the beams cannot be shaped in the vertical plane in order to increase the coverage efficiency and eliminate the ducting and the interference from the surrounding base station antennas. Disclosure of Invention

A Novel Multi-Beam Base Station Antenna Technology:

In order to overcome all the problems of the current multi- beam base station antennas, a novel base station antenna with arbitrary number of beams having arbitrary beam widths has been developed. It consists of two parabolic cylindrical reflectors and a set of novel small size broadband resonant feeds. An unlimited number of such novel feeds operating at different frequency bands can be used with the same base station antenna. Thus, the new base station antenna can be easily upgraded to any new generation of wireless technology by replacing the feeds instead of replacing the whole antenna which is the case with the current base station antennas [5]. Multi beam technology can be easily applied to the new antenna by adding multi feeds and slightly modifying the geometry of the sub reflector and the main reflector. This process is simple, and adds much less weight and size than the

conventional antenna technology would do. For the first time, the new multi- beam base station antenna can simultaneously cover an unlimited number of wireless applications, regardless of their frequency bands. The new multi- beam base station antenna can simultaneously cover all, current and future, wireless technology generations such as 2G, 3G, 4G (LTE),— etc. Some of the key unique features of the new multi-beam base station antenna

technology are summarized as follows:

A novel low-cost light-weight multi-beam base station antenna with arbitrary number of beams and with arbitrary beam widths.

The new multi-beam base station antenna can generate a single wide-beam or multiple narrow-beams without adding any significant complexity.

The new multi-beam base station antenna can, simultaneously, provide both horizontal and vertical sectorizations, which doubles the number of beams. Increasing the number of beams increases system capacity because each beam can serve a smaller area.

Two different techniques can be used for arbitrary vertical electric beam tilting. Both techniques can be used together or only one of them can be used. One of these techniques can tilt all beams by the same vertical tilt angle while the other technique can tilt different beams by either equal or different vertical tilt angles.

All beams can be shaped in the vertical plane in order to increase the coverage efficiency and eliminate the ducting and the interference from the surrounding base station antennas.

The new multi-beam base station antenna can cover 180 degrees instead of 120 degrees. Thus, the whole azimuth can be covered by only two antennas instead of three.

The new multi-beam base station antenna, simultaneously, covers the whole frequency bands of 2G, 3G and 4G (LTE). It covers the bands (450- 470 MHz), (690-960 MHz), (1.4-2.7 GHz) and (3.3-3.8 GHz) with at least 2 ports for each of these bands in each beam (2 perpendicular polarizations, +45 and - 45 degrees).

The new base station antenna can, simultaneously, generate a single wide-beam that covers the whole sector (either 120 or 1 80 degrees) and multiple narrow-beams that cover the same sector. Hence, only one unified version of the new base station antenna will be produced. It can be used to generate either a single wide beam, multiple narrow beams or both of them together according to the current and future network needs and requirements, which keep changing. The unified version of the new base station antenna covers the whole frequency band from 450 MHz to 3.8 GHz.

The capability of the new base station antenna to, simultaneously, cover each sector by a single wide beam and multiple narrow beams provides a good opportunity for co-sitting. Two different operators can, simultaneously, use the same base station antenna where one of them uses the single wide beam while the other operator utilizes the multiple narrow beams according to the capacity of the customers of each operator in any specific sector.

The ability of the new base station antenna to, simultaneously, generate a single wide-beam and multiple narrow-beams that cover the same sector can be utilized in adding massive MIMO configurations.

The new base station antenna can generate only a single wide beam, multiple narrow beams or both, depending on the situation, the nature and the capacity of the covered sector, which may be different from week days to weekends or from day hours to night hours, etc. Of course, only the base station receiving/transmitting components and equipment of the generated beams have to be operating. Thus, not all the base station

receiving/transmitting components and equipment have to work together all the time. This increases their lifetime and allows any required maintenance and/or routine checkup. It also saves power.

• In the new base station antenna, increasing the beamwidth does not necessarily cause a significant drop in the gain.

• The new multi-beam base station antenna can include up to 80

ports or even more, which could facilitate any further needed capacity expansions in the future.

• The new multi-beam base station antenna could simultaneously cover all, current and future, wireless technology generations such as 2G, 3G, 4G (LTE),— etc. All mobile operators could share the same network of base station antennas (co-sitting) by adding a separate feed for each operator.

In conclusion, the new-multi-beam base station antenna has too many design parameters with too many degrees of freedom that can be optimized together in order to yield any desirable performance and any special requirements

Brief Description of Drawings

Fig.l A dual parabolic cylindrical reflector antenna to generate Multi-Beams Fig.2 Azimuth Radiation Pattern

Fig.3 Elevation Radiation Pattern

References

1- hftps://www.googcom/patents/US201 10205119

2- http://www.wseas.us/e- librarv/conferences/2005athens/ee/papers/507- 176.pdf

3-http://waset.org/publications/3392/design-and-simulation-o f-a- concentratedluneb 888 erg-antenna

4- https ://www. oogle.com/patents/US20150091767

5- http://amantantennas.com/am/library/pdfs/2012/paper N.PDF