WO2000076030A1

WO2000076030A1 - Multimode sectored antenna systems

Info

Publication number: WO2000076030A1
Application number: PCT/US2000/015627
Authority: WO
Inventors: Naftali Herscovici; Robert F. Williamson; Thomas Peragine
Original assignee: Spike Broadband Systems, Inc.
Priority date: 1999-06-07
Filing date: 2000-06-07
Publication date: 2000-12-14
Also published as: WO2000076028A1; AU5869300A; AU5468700A; WO2000076027A1; AU5468600A

Abstract

Multimode sectored antenna systems for use in wireless communication systems. In one example, the sectored antenna systems provide the capability of flexibly allocating a number of data carriers having different data transporting capacities, to simultaneously accommodate a variety of user demands in both point-to-point and point-to-multipoint configurations. In another example, various sectored antenna systems provide the capability of radiating a number of data carriers each having a variety of spatial profiles in azimuth and elevation, and at a variety of elevation angles, to accommodate a number of possible user topological distributions throughout a coverage area.

Description

MULTIMODE SECTORED ANTENNA SYSTEMS

Field of the Invention

The present invention relates to wireless communications, and particularly, to multimode sectored antenna systems that are capable of accommodating a variety of capacity demands and topological distributions of wireless communication system end- users dispersed throughout a coverage area.

Description of the Related Art Wireless communication systems are recognized as an effective method of interconnecting users of a communication network or service. For purposes of the present disclosure, such users are also referred to as "subscribers" to the communication service.

In wireless communication systems, information typically is transported on data carriers that are radiated by one or more antennas, or antenna systems, in open space throughout a coverage area. In general, the transported information may be in the form of analog or digital signals which are used to encode or "modulate" the data carriers. A variety of encoding / decoding (or modulation / demodulation) techniques may be employed to impart information to, and extract information from, the data carriers. In wireless communication systems, typically one or more data carriers directed to some space within a coverage area constitute a wireless communication link. The geographic extent, or "range," of a given communication link in a wireless system generally may be defined by a spatial profile of the radiated data carriers which interconnect various users. One consideration in the design of a wireless communication system is the

"topological distribution" of users; namely, the location, density, and overall distribution of users to which the system provides communication services. Throughout a given coverage area around an antenna or antenna system of a wireless communication system, a number of users may be dispersed in a variety of topological distributions. For example, in one portion of the coverage area several users may be located in close proximity, while in another portion of the coverage area other users may be more sparsely dispersed. Additionally, different users may be situated at different altitudes with respect to the antenna or antenna system, and at different radial distances from the antenna or antenna system.

Another consideration in the design of a wireless communication system is the demand each user may place on the information transporting capabilities of the system. For example, different users may place different demands on the information transporting "capacity" of available data carriers which form various communication links within the wireless system. In particular, different users may have data capacity requirements that change with time (i.e., "dynamic" capacity requirements).

The "capacity" of a communication link generally refers to the amount of data that can be reliably transported over the link per unit time, and is typically measured in terms of data bits per second (bps). In some wireless communication systems, information is transported on "channels" formed by radiated carriers having a predetermined bandwidth and carrier frequency within a designated frequency spectrum, and a corresponding capacity. In such systems, generally, wider bandwidth frequency channels have a higher capacity to transport information.

A variety of configurations have been employed in conventional wireless communication systems to provide communication services to users, depending in part on the geographic location, the topological distribution, and the capacity requirements of the users. For example, some conventional wireless communication systems radiate one or more dedicated data carriers to transport information only to and from a specific user, or between two specific users. Such wireless communication systems are typically referred to as "point-to-point" systems.

Other conventional wireless communication systems may radiate one or more data carriers to one or more groups of users, to transport information to and from each respective group. Within any one group, the users may be located together in close proximity, or may be sparsely scattered throughout a portion of the coverage area. The groups themselves may be located proximate to (e.g. adjacent to) each other or may be separated by some distance within the coverage area. Such wireless communication systems generally are referred to as "point-to-multipoint" systems, in which the available capacity of any frequency channel constituting a communication link to a particular group typically is shared amongst the users of the group.

In sum, while point-to-point configurations for conventional wireless communication systems generally provide communication links between a small number of specific users, point-to-multipoint configurations generally involve a number of users that share the resources, or capacity, of a communication link.

To increase the capacity of a particular frequency channel within a coverage area, wireless communication systems may employ a sectored antenna system, which permits the reuse of a frequency spectrum amongst multiple sectors within a coverage area. By dividing a coverage area into a number of sectors and reusing one or more frequency channels in some of the sectors, the data carrying capacity of the system is essentially multiplied by the number of sectors in which the channels are used. A sectored antenna system may be used in either a point-to-point or a point-to-multipoint configuration.

Summary of the Invention

One embodiment of the invention is directed to a multimode sectored antenna system comprising a first antenna arrangement to radiate a first radiation pattern into a coverage area and a second antenna arrangement coupled to the first antenna arrangement to radiate a second radiation pattern into the coverage area. The second radiation pattern has a different spatial profile than the first radiation pattern.

Another embodiment of the invention is directed to a wireless communication method, comprising steps of radiating a first radiation pattern into a coverage area, and radiating a second radiation pattern into the coverage area, wherein the second radiation pattern has a different spatial profile than the first radiation pattern.

Another embodiment of the invention is directed to a wireless communication antenna system, comprising at least one Luneberg-type lens, and at least one first antenna feed device coupled to the at least one Luneberg-type lens. The first antenna feed device transmits first radiation through the Luneberg-type lens into a coverage area. The antenna system also includes at least one second antenna feed device coupled to the at least one Luneberg-type lens. The second antenna feed device is positioned with respect to the at least one Luneberg-type lens so as to transmit second radiation into the coverage area, such that the second radiation does not propagate through the at least one Luneberg-type lens. Another embodiment of the invention is directed to a wireless communication antenna system, comprising a first antenna arrangement including a Luneberg-type lens and a plurality of antenna feed devices coupled to the Luneberg-type lens, wherein each feed device transmits respective first radiation through the Luneberg-type lens into a respective portion of a coverage area. The system also includes a second antenna arrangement coupled to the first antenna arrangement, wherein the second antenna arrangement includes at least one planar array of antenna feed devices. The planar array transmits second radiation into at least a portion of the coverage area.

Brief Description of the Drawings

The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like reference character or numeral. For purposes of clarity, not every component may be labeled in every drawing.

Fig. 1 is diagram illustrating a basic multibeam sectored antenna system concept using a Luneberg-type lens;

Fig. 2 is a diagram of a sectored antenna system similar to that shown in Fig. 1 for transmitting and/or receiving information in a 360 degree coverage area around the antenna system;

Fig. 3 A is a plot showing a relationship between a beamwidth of a radiation pattern as a function of a diameter of a lens employed in the antenna system according to one embodiment of the invention;

Fig. 3B is a diagram showing an example of radiation patterns throughout the coverage area of a multibeam omnidirectional antenna system, according to one embodiment of the invention;

Fig. 4 is a diagram showing radiation patterns in one sector of a coverage area of a multimode sectored antenna system, according to one embodiment of the invention; Fig. 5 is a diagram of a multimode sectored antenna system that is capable of producing the radiation patterns shown in Fig. 4 according to one embodiment of the invention;

Fig. 6 is a diagram similar to that of Fig. 5, showing a multimode antenna system according to another embodiment of the invention;

Fig. 7A and 7B are diagrams showing side and top views, respectively, of a hemispherical multibeam multimode omnidirectional antenna system, according to one embodiment of the invention;

Fig. 8 is a diagram showing a side view of a hemispherical multibeam omnidirectional antenna system, according to one embodiment of the invention; Fig. 9 is a diagram of an enlarged view of a portion of Fig. 8, showing possible shapes of a conductive enclosure of the antenna system of Fig. 8, according to various embodiments of the invention; and

Fig. 10 is a diagram showing an example of a multimode sectored antenna system employing a spheroidal-shaped dielectric lens, according to one embodiment of the invention.

Detailed Description

The present invention is directed to various multi-beam and multimode sectored antenna systems for wireless communication systems. The sectored antenna systems according to various embodiments of the present invention provide several desirable features for wireless communication systems.

For example, according to some embodiments, wireless communication systems employing sectored antenna systems of the invention have the capability to flexibly allocate a number of data carriers having different information transporting capacities, to simultaneously accommodate a variety of user demands using both point-to-point and point-to-multipoint configurations .

Additionally, according to some embodiments, wireless communication systems employing various sectored antenna systems according to the invention have the capability to radiate data carriers having a variety of spatial profiles in a cross-section orthogonal to the direction of propagation of the radiation, to accommodate a number of possible user topological distributions throughout a coverage area.

Examples of frequency ranges suitable for the data carriers radiated by sectored antenna systems according to the invention include, but are not limited to, the Multi- point Distribution Services (MDS) spectrum from 2.15 GHz to 2.156 GHz, the Multichannel Multi-point Distribution Services (MMDS) spectrum from 2.5 GHz to 2.686 GHz, the Wireless Communication Services (WCS) spectrum, which is a 30 MHz band at approximately 2.3 GHz, the National Information Infrastructure (Nil) spectrum from 5 GHz to 6 GHz, and the Local Multi-Point Distribution Services (LMDS) spectrum, near 28 GHz and 31 GHz.

For point-to-point communication using narrow beams, the LMDS spectrum at approximately 28-31 GHz may be particularly suitable, as this spectrum can support frequency channels having wide and flexible bandwidths, which may be custom allocated depending on a particular application and/or user demand. Accordingly, in some embodiments, the LMDS spectrum may provide several high capacity frequency channels for respective individual users, without the need of frequency reuse schemes in the coverage area. In other embodiments, frequency reuse may be employed nonetheless, if appropriate for a given application.

Similarly, the MMDS spectrum from approximately 2.5 GHz to 2.7 GHz may be particularly useful for point-to-multipoint communication using wider beams. While MMDS frequency channels generally have a bandwidth of 6 MHz, and accordingly may have a more limited capacity with respect to LMDS channels, the MMDS spectrum has the desirable quality of being fairly robust against rain and other potentially adverse environmental conditions, and is generally effective over wide ranges and long distances (up to 30 miles).

In general, antenna systems according to the invention may radiate a variety of data carriers within a frequency range of approximately 1 GHz to 40 GHz, as well as other frequency ranges, including spectrum which may or may not be presently developed or licensed by the Federal Communications Commission (FCC). In some embodiments, antenna systems according to the invention may simultaneously radiate data carriers in a variety of different frequency ranges whose radiation spatial profiles either partially or fully overlap, within a single portion or sector or throughout multiple portions or sectors of a coverage area. For example, according to some embodiments, the communication systems described herein can be used to connect users in the same sector or portion of a coverage area simultaneously in a point-to-point and point-to- multipoint fashion.

Following below are more detailed descriptions of various concepts related to, and embodiments of, multimode sectored antenna systems according to the present invention. It should be appreciated that various aspects of the invention as discussed above and further below may be implemented in any of numerous ways, as the invention is not limited to any particular manner of implementation. Examples of specific implementations are provided for illustrative purposes only. Two-way communication in a wireless communication system implies that any antennas or antenna systems used for communication typically are used for both transmission and reception of electromagnetic radiation. In the discussion below it should be understood that the various concepts presented with respect to antennas and antenna systems according to the invention apply similarly for both the transmission and the reception of radiation. Accordingly, for the sake of brevity, such antennas and antenna systems are discussed herein primarily in terms of radiation transmission. However, it should be appreciated that the invention is not limited merely to transmission of radiation, as the antennas and antenna systems disclosed herein can function bi-directionally (i.e., both transmit and receive radiation) according to various embodiments of the invention.

In one aspect, sectored antenna systems according to various embodiments of the present invention advance the concept of a sectored coverage area by employing antenna arrangements having large apertures, alone or in combination with other antenna arrangements having different-sized apertures typical of more conventional systems. The aperture of an antenna or an antenna arrangement generally refers to the physical size of an antenna feed device or an array of antenna feed devices, and/or the size of any lens or lenses through which radiation radiated by the feed device (or devices) passes. For purposes of the present discussion, an "antenna arrangement" refers to one or more feed devices (e.g., a single feed device, or a linear or planar array of feed devices), taken alone or in combination with one or more lenses (e.g., a Luneberg-type lens), to transmit and/or receive radiation having a particular cross-sectional spatial profile throughout all or a portion of a coverage area around the antenna arrangement. A maximum number of sectors into which a coverage area may be divided depends at least in part on the physical size of any components contributing to the aperture of the antenna arrangement (e.g., the antenna feed devices and any lens or lenses used with the feed devices). In general, larger lenses accommodate a greater possible number of antenna feed devices, and provide for narrower beams from each antenna feed device. Typically, because a lens coupled to one or more devices may be appreciably larger than any one feed device coupled thereto, the larger dimensions of the lens determine the aperture of the antenna arrangement. Accordingly, relatively small feed devices transmitting and/or receiving radiation through a larger lens serving as a large aperture for the feed devices may provide for an antenna arrangement capable of transmitting and/or receiving radiation having relatively narrow cross-sectional beamwidths. In this manner, a greater number of narrow radiation beams may be transmitted and/or received in respective sectors of a coverage area surrounding the antenna arrangement. As discussed above, by increasing the number of distinct sectors into which a coverage area is divided, a greater information carrying capacity may be achieved in a wireless communication system. A general relationship between antenna aperture and a corresponding radiation spatial profile (e.g., beamwidth) is discussed further below in connection with Fig. 3 A. One example of a sectored antenna arrangement design which serves as a foundation for antenna systems according to various embodiments of the present invention is shown in Fig. 1. The antenna arrangement of Fig. 1 includes a Luneberg- type lens (15), which is a collimating device similar to an optical lens. However, unlike an optical lens (which typically has a single point as a focus), a distinguishing property of a Luneberg-type lens is that the entire surface of the lens may serve as a focus. This characteristic implies that anywhere on the Luneberg-type lens surface, one may place as many antenna feed devices (20, 25, 30) as physically possible to obtain a corresponding number of radiation beams (21, 26, 31) directed in diametrically-opposed directions, as shown in Fig. 2. Luneberg-type lenses are discussed in detail, for example, in the textbook "Mathematical Theory of Optics," R.K. Luneberg, University of California Press, Berkeley and Los Angeles, 1964, Library of Congress Catalog #64-19010.

According to one embodiment, the antenna arrangement shown in Fig. 1 may include one or more antenna feed devices (20, 25, 30) located at various points around the Luneberg-type lens 15. Radiation from each antenna feed device is collimated on the diametrically opposing side of the lens at infinity. Assuming that each beam (e.g., 21) is sufficiently isolated from other beams (e.g., 26. 31) radiated by the antenna arrangement, parameters such as data carrier frequency and/or information encoding or modulation techniques may be reused for two or more of the radiated beams emanating from the lens. For example, in some applications, to provide an acceptable level of beam isolation, a particular data carrier frequency may be reused by non adjacent (e.g., alternate) radiation beams around the lens. Alternatively, various cross-polarization techniques may be used to increase isolation between potentially interfering beams, so as to permit various reuse strategies. As discussed above, the potential for frequency and/or modulation technique reuse allowed by an antenna arrangement utilizing a Luneberg- type lens as shown in Figs. 1 and 2 significantly enhances the information carrying capacity of a wireless communication system employing such an antenna system. Similar to reflectors, Luneberg-type lenses typically are effective over an extremely wide spectrum of radiation frequencies, allowing for the design of sectored antenna arrangements which are accordingly effective over a wide range of frequencies and at a variety of different frequency bands. The limit of operation for lower frequency bands generally is constrained mainly by the physical size of the lens. For sub- millimeter and millimeter bands such as 23 GHz, 24 GHz, 28 GHz and 38 GHz, for example, a Luneberg-type lens provides an efficient sectored antenna arrangement solution for multi-beam wireless communication systems in general, and multi-beam multimode omnidirectional wireless communications in particular, as discussed further below.

A typical relationship between antenna aperture size and radiation spatial profile, or "beamwidth" is given by the equation λ _B = k — , (Eq. 1)

A where W_B is the beamwidth of the radiation pattern in a given plane of interest, A is the size of the antenna aperture in a direction parallel to the plane of interest, and λ is the radiation wavelength (given by the speed of light c divided by the data carrier frequency of the radiation). For purposes of the present discussion, the beamwidth of a radiation beam refers to the angular width (e.g., in degrees) of a beam between approximately the - 3dB points of the spatial profile of a main lobe of the beam in a plane of interest. The factor k in Eq. (1) is a constant associated with the radiation pattern. From the above relationship, it may be appreciated that increasing the aperture size A results in a smaller (or "narrower") beamwidth W_B in a given plane. If, for example, the plane of interest is an azimuth (horizontal) plane essentially parallel to the ground of a coverage area, increasing an azimuth dimension of the aperture A corresponds to reducing azimuth beamwidth. In this manner, a large azimuth aperture may provide for an antenna arrangement that permits a high degree of sectorization of a coverage area in the azimuth plane, by allowing for narrow azimuth beamwidths.

With reference to Eq. (1), in one aspect, for example, the constant k related to the radiation beam spatial profile may be taken as approximately 65, which corresponds to a cosine aperture field distribution. Using this exemplary value for k, the graph shown in Fig. 3 A describes the azimuth and elevation beamwidth (in degrees) of a single radiation beam as a function of a diameter (in wavelengths) of a Luneberg-type lens. The appropriate size of a lens may be determined from the graph of Fig. 3 A based on the required angular resolution of a radiation beam within the coverage area. For example, from Fig. 3 A it can be determined that a radiation beam having a beamwidth of approximately 3° in both azimuth and elevation requires a lens diameter of approximately 22 wavelengths. Using a carrier frequency of 28 GHz, for example, the required wavelength is accordingly 0.42 inches, and the required lens diameter is approximately 9.5 inches.

As shown in Fig. 3B. using Eq. (1) and the plot of Fig. 3 A, in one example of a multi-beam omnidirectional sectored antenna arrangement according to the invention, a spherical Luneberg-type lens having a diameter of 12" is capable of generating a radiation pattern including a plurality of radiation beams each having an approximately 3° beamwidth in at least an azimuth plane of the coverage area, at a data carrier frequency of 28 GHz. Accordingly, 120 radiation beams may be employed in this embodiment to span a coverage area of 360° around the antenna system in the azimuth plane.

In one embodiment of a multimode sectored antenna system according to the invention, an antenna arrangement radiating a plurality of narrow radiation beams, such as shown in Fig. 3B, may be used simultaneously with one or more other antenna arrangements each radiating one or more wider radiation beams that at least partially overlap the narrow beams shown in Fig. 3B.

As discussed above, the topological distribution of users throughout a coverage area receiving radiation from an antenna arrangement or system may not be uniform. For example, in one portion of the coverage area, a large number of users may be grouped in close proximity, while in other portions of the coverage area fewer users may be more sparsely distributed. Additionally, the respective capacity demands of users may be different, and may vary with time.

For sectored antenna arrangements and systems according to various embodiments of the present invention, the coverage area may be defined in terms of an azimuth (horizontal) plane and an elevation plane orthogonal to the azimuth plane at each angular position around the antenna arrangement or system. In general, both the azimuth plane and each elevation plane pass through the sectored antenna system, although not all embodiments may require this. In particular, according to one embodiment, a three-dimensional coordinate system may be defined for the antenna arrangement or system, in which various spatial positions in the coverage area may be described in terms of the coordinate system by three spherical coordinates; namely, an azimuth angle, an elevation angle, and a radius from an origin of the coordinate system (e.g., a distance from the antenna arrangement or system). Fig 5 illustrates one example of such a coordinate system, in which an x, y, and z axis each passes through an origin approximately centered in the antenna system shown. An azimuth plane is defined by the x-y plane, and a number of elevation planes are given by any plane that is orthogonal to the x-y plane and that passes through the coordinate system origin (e.g., the x-z plane, the y-z plane). As shown in Fig. 5, the point P in the coverage area around the antenna system may be designated with reference to the coordinate system by an azimuth angle θ in the x-y plane, a radial distance r from the origin, and an elevation angle φ between the z-axis and a vector connecting the point P and the origin.

From the foregoing, it should be appreciated that the coverage area may span up to 360° around the antenna system in the azimuth plane, and up to ±90° in an elevation plane, referenced to the azimuth plane. For example, elevation angles of 0° through +90° would indicate positions throughout "top hemispherical" portions of the coverage area, while elevation angles from 0° through -90° would indicate positions throughout "bottom hemispherical" portions of the coverage area. Based on the foregoing concepts, it should be appreciated that, according to one embodiment of the invention, a coverage area may be divided into a number of azimuth sectors in the azimuth plane, as well as a number of elevation sectors in an elevation plane at particular azimuth angles, to form a coverage volume "matrix." Accordingly, radiation beams from various sectored antenna arrangements and systems according to the invention may be radiated at a number of different elevation angles referenced to the azimuth plane, so as to arrive at predetermined coverage volume "cells" within the matrix. As discussed above, each cell of the coverage area matrix may be identified, for example, by the three-dimensional spherical coordinates of azimuth angle, elevation angle, and radial distance from the antenna arrangement or system. In particular, based on a particular user's radial distance from the antenna system and the height of the user's antenna, an appropriate elevation angle may be determined, using trigonometric relations, for a radiation beam to reach the coverage volume cell in which the user's antenna is located. In one embodiment, a multimode sectored antenna system according to the invention includes a first antenna arrangement to radiate a first radiation pattern into a coverage area, and a second antenna arrangement to radiate a second radiation pattern into the coverage area. The second radiation pattern has a different spatial profile than the first radiation pattern. In one aspect of this embodiment, at least two users in the sector may receive the second radiation pattern, such that the antenna system is capable of simultaneous point-to-multipoint communication with a group of users in the sector, including the at least two users. Additionally, in one aspect, the first radiation pattern is received by respective users in the sector, such that the antenna system is capable of simultaneous point-to-point communication with each respective user in the sector.

According to other aspects, the antenna system of this embodiment may also radiate the first radiation pattern and the second radiation pattern at a variety of different elevation angles with respect to the azimuth plane.

For example, in one aspect of this embodiment, as shown in Fig. 4 (which depicts radiation spatial profiles in an azimuth plane), the first radiation pattern 33 includes a plurality of first radiation beams 133, wherein each first radiation beam 133 has a respective first beamwidth 233 in the azimuth plane. The second radiation pattern includes at least one second radiation beam 143, having a second beamwidth 243 in the azimuth plane. As shown in Fig. 4, the second radiation beam 143 may overlap at least some of the plurality of first radiation beams 133 in an azimuth plane of the coverage area.

Fig. 5 illustrates an example of a multimode sectored antenna system according to one embodiment of the invention which is capable of producing the radiation patterns shown in Fig. 4. The system of Fig. 5 includes a first antenna arrangement 300 having a Luneberg-type lens 45 and three antenna feed devices (40). Each feed device 40 radiates a radiation beam (e.g., a beam 133 in Fig. 4) having a relatively narrow beamwidth 233 in the azimuth plane of the coverage area. For example, in one aspect of this embodiment, each beam 133 in Fig. 4 has a beamwidth 233 of from approximately 3 degrees to approximately 15 degrees. It should be appreciated that while three feed devices 40 are shown in Fig. 5, the invention is not limited in this respect, as any number of feed devices may be included in the first antenna arrangement 300.

The multimode sectored antenna system of Fig. 5 also includes a second antenna arrangement 320 which includes one or more planar radiating elements (50), each radiating element 50 including one or more antenna feed devices. Each radiating element 50 directs one or more radiation beams into the azimuth plane, wherein each beam has a larger beamwidth than the beams of the first antenna arrangement 300. For example, in one aspect, a radiation beam of the second arrangement 320 has a beamwidth of approximately 90° in the azimuth plane.

Additionally, Fig. 5 shows that a multimode sectored antenna system according to one embodiment of the invention may include a third antenna arrangement 340 having at least one radiating element 60 (e.g. a planar array of antenna feed devices). The third antenna arrangement 340 may direct one or more respective radiation beams into the azimuth plane, wherein the beams have respective beamwidths different than those of the first and second antenna arrangements. For example, in one aspect, the radiation beams of the third arrangement have respective beamwidths of approximately 25° in the azimuth plane.

While Fig. 5 shows that the radiation beams associated with the first, second, and third antenna arrangements essentially are directed into the same portion or sector of a coverage area, it should be appreciated that the first, second, and third antenna arrangements, respectively, may be positioned so as to arbitrarily direct their respective radiation beams to different portions or sectors of the coverage area in the azimuth plane. In particular, the first, second and third antenna arrangements each may be constructed and positioned so as to provide essentially 360 degree coverage in the azimuth plane. For example, with reference again to Fig. 5, according to one embodiment, each of the second and third antenna arrangements may include four or more planar arrays positioned with respect to each other (e.g., at right angles to form a square shape), so as to each provide radiation to a particular portion (e.g., a 90 degree quadrant) of the coverage area.

With reference again to Fig. 4, according to one embodiment of the invention, the radiation patterns associated with two or more antenna arrangements constituting a multimode sectored antenna system according to the invention (e.g., as shown in Fig. 5) may partially or entirely overlap within one or more sectors of a coverage area. For example, as shown in Fig. 4, while a first antenna arrangement radiates a plurality of first radiation beams 133 each having a relatively narrow bandwidth 233 throughout an approximately 30° sector of the coverage area in the azimuth plane, a second antenna arrangement radiates one radiation beam 143 having a relatively wider beamwidth 243 (e.g., approximately 30° as shown in Fig. 4) in the azimuth plane. As shown in Fig. 4, the beam 143 overlaps the plurality of radiation beams 133 radiated by the first antenna arrangement.

In Fig. 4, a number of users may be dispersed throughout the approximately 30° sector of the coverage area shown. At least some or all of the users in the 30° sector will receive the single 30° beamwidth radiation beam 143 radiated by the second antenna arrangement. In this manner, the multimode antenna system is capable of simultaneous point-to-multipoint communication with a group of some or all of the users in the approximately 30° sector. Additionally, according to one embodiment, each narrow beamwidth radiation beam 133 shown in Fig. 4 may be received by only one respective user in the approximately 30° sector shown in Fig. 4. In this manner, the multimode antenna system is capable of simultaneous point-to-point communication with each respective user in the sector. Accordingly, while some or all of the users in the approximately 30° sector may share and exchange information by virtue of the wider beamwidth radiation pattern 43 from the second antenna arrangement, each user in the approximately 30° sector may also obtain information by virtue of the narrow multi- beam radiation pattern 33 of the first antenna arrangement.

As a result, the multimode sectored antenna system described above is capable of providing both point-to-multipoint and point-to-point communication services within the same wireless system. Furthermore, as shown in Fig. 4, multimode sectored antenna systems according to one embodiment of the invention are capable of providing both point-to-multipoint and point-to-point communication within a same sector of a coverage area, and simultaneously to a single user or different users.

From the foregoing, it should be appreciated that a wide variety of point-to-point and point-to-multipoint configurations are possible and considered within the scope of various sectored antenna systems according to the present invention. For example, in a system of the invention which provides the radiation patterns shown in Fig. 4, the narrow beams 133 and the wider beam 143, respectively, may use the same or different frequency ranges. Additionally, similar configurations of overlapping wide and narrow beams in a single sector may be used in other sectors of the coverage area, and may or may not employ any number of frequency reuse schemes. Furthermore, the bandwidths of the frequency channels respectively associated with the wide and narrow beams may be different, providing for a variety of information capacities for the multiple beam configurations.

Fig. 6 shows another embodiment of the present invention similar to that of Fig. 5, in which one or more of the radiation beams associated with a particular antenna arrangement may be directed at an elevation angle to the azimuth plane. In particular. Fig. 6 shows a first antenna arrangement employing a Luneberg-type lens 45 and having two feed devices 40 at different elevation angles (i.e., φi, φ ₂ ) proximate to the lens for generating radiation beams directed at respectively different elevation angles with respect to the azimuth plane. Additionally, Fig. 6 shows a second antenna arrangement including a planar array

80 of antenna feed devices that radiate one or more second asymmetrical radiation beams (i.e., different azimuth and elevation spatial profiles) having a beamwidth of approximately 90° in the azimuth plane and approximately 30° in the elevation plane. In one aspect, the second antenna arrangement 320 of Fig. 6 may be oriented so as to direct one or more second radiation beams at some elevation angle with respect to the azimuth plane. Finally, Fig. 6 shows a third antenna arrangement 340 including a planar array 90 of antenna feed devices constructed and arranged to radiate one or more third symmetrical radiation beams having a beamwidth of approximately 25° in both the azimuth and elevation planes. As with the second antenna arrangement 320, the third antenna arrangement 340 may be oriented so as to direct one or more third radiation beams at some elevation angle with respect to the azimuth plane.

In sum, as shown in Figs. 5 and 6, a multimode sectored antenna system according to one embodiment of the invention may include a first antenna arrangement (e.g., an antenna arrangement using a Luneberg-type lens), as well as one or more other antenna arrangements (e.g., one or more discrete antenna feed devices or planar arrays of such devices). In such a multimode antenna system according to one embodiment of the invention, the radiation patterns radiated by the first antenna arrangement and at least one additional antenna arrangement have respectively different spatial profiles in at least one plane of interest. In particular, from the sectored antenna systems of Figs. 5 and 6, a wide variety of radiation patterns may be provided, in both the azimuth and elevation planes, and at various elevation angles, to facilitate both point-to-multipoint and point-to- point wireless communication for a number of arbitrary topological distributions of users. The present invention also provides for specific embodiments of a sectored antenna system that includes a Luneberg-type lens having other than a spherical shape. Figs. 7A and 7B are diagrams showing side and top views, respectively, of an antenna system according to another embodiment of the invention. In the one embodiment of Figs. 7A and 7B a sectored antenna system according to the invention includes a first antenna arrangement 300 having a Luneberg-type lens 105 with a hemispherical shape. In one aspect of this embodiment, hemispherically shaped Luneberg-type lens 105 may be mounted on a conductive ground plane (110), which, by reflection, produces an image of "source" radiation radiated from the hemispherically-shaped Luneberg-type lens, which image is superimposed on the source radiation.

In particular, the first antenna arrangement 300 of the antenna system shown in Figs. 7A and 7B radiates a radiation pattern associated with the one or more antenna feed devices 40 into a coverage area having an azimuth plane and a number of elevation planes. In one aspect, the azimuth plane is parallel to the conductive ground plane, and the elevation planes are orthogonal to the azimuth plane and pass through the dielectric lens. The conductive ground plane (1 10) reflects an image of the radiation pattern, such that for a top hemispherical solid angle in the elevation plane, referenced to the azimuth plane, a spatial profile of the radiation pattern approximates that of a reference spatial profile associated with one or more similar antenna feed devices radiating through a fully spherical Luneberg-type lens.

According to imaging principles of electromagnetic theory, source radiation emanated by an antenna or antenna system, and impinging upon a theoretically infinite ground plane made of conductive material and located below the antenna system, produces reflections from the ground plane. These reflections superimpose with the originally emanated source radiation. As a result of the superposition of source and image radiation, a spatial profile of the "composite" radiation, in an upper hemisphere of a coverage area around the hemispherically shaped Luneberg-type lens, is substantially similar to the spatial profile that would be associated with radiation emanated by an antenna system using a fully spherical Luneberg-type lens. In other words, the reflected radiation from the infinite ground plane below the hemispherically shaped lens virtually "substitutes" for that portion of the source radiation that would have been emanated from the bottom hemisphere of a fully spherical lens. It should be appreciated, however, that while in the top hemisphere of the coverage area above the infinite ground plane the spatial profile of radiation from the hemispherically shaped lens would appear to be substantially identical to that associated with a fully spherical lens, in contrast, below the ground plane (in a bottom hemisphere of the coverage area) the radiation pattern would be null. In practice, since an infinite ground plane is not possible, the elevational spatial profile of the radiation emanated from the hemispherically shaped lens above a finite conductive ground plane does not exactly replicate that of radiation emanated from a fully spherical lens, but rather is a close approximation thereof. In one aspect of the system shown in Figs. 7A and 7B, radiation fields from the hemispherically shaped lens that may be present below the conductive ground plane 110 typically are very small. Accordingly, the ground plane 1 10 may provide for reduced interference between the radiation patterns of the first antenna arrangement 300 employing the hemispherical Luneberg-type lens 105, and other antenna arrangements (e.g., a second antenna arrangement 320, and perhaps additional antenna arrangements, utilizing planar type antenna arrangements as shown in Figs. 5 and 6), which may be located on a side of the ground plane 110 opposite that of the lens 105.

In Figs. 7A and 7B, the hemispherically-shaped Luneberg-type lens 105 is shown mounted above and to the ground plane 1 10. As discussed above, because a finite ground plane is used in practice as opposed to a theoretically infinite ground plane, the spatial profile of radiation associated with the hemispherically-shaped Luneberg-type lens approximates that of a fully spherical Luneberg-type lens, but may include slight differences, particularly in an elevation plane of the spatial profile.

In one embodiment of a sectored antenna system according to the invention including a hemispherically-shaped lens, one or more antenna feed devices 40 may be distributed about an "equator" of the lens, proximate to the finite ground plane. In particular, the hemispherically shaped lens may be coupled to the finite ground plane at the equator of the lens, and the antenna feed devices may also be coupled to the finite ground plane to improve the mechanical stability of the feed devices. To compensate for differences in the spatial profile of the radiation pattern in the elevation plane due to a finite ground plane, according to one embodiment of the invention as shown in Fig. 8, the ground plane 110 may be extended to form a conductive enclosure 125 below the hemispherically-shaped lens 105. Generally, the shape of the conductive enclosure and, in particular, the shape of a "director line" 130 along a perimeter of the conductive enclosure, at least partially determines the ultimate spatial profile of the radiation pattern in the elevation plane due to a superposition of source and reflected radiation from the contour of the conductive enclosure. Accordingly, as shown in Fig. 9, different shapes for the conductive enclosure 125, or different director lines 130 along the contour of the enclosure, may be chosen to compensate for any differences or aberrations in the spatial profile of the radiation field in the elevation plane resulting from a finite ground plane. Additionally, according to one aspect of this embodiment, the conductive enclosure 125 provides isolation of any cables supplying signals to any of the antenna feed devices 40 coupled to the lens 105. In embodiments of the invention discussed above, the inherent symmetry of a spherically or hemispherically shaped Luneberg-type lens of the first antenna arrangement generally results in an almost symmetrical radiation pattern in azimuth and elevation for the beams of the first radiation pattern. However, some applications may require a spatial profile of the radiation pattern in elevation that is different from the spatial profile of the radiation pattern in the azimuth plane. Accordingly, it should be appreciated that lens shapes other than the hemispherical shape shown in the embodiments of Figs. 7A, 7B, and 8. used in conjunction with a conductive ground plane, may be suitable for purposes of other embodiments of the invention. In particular, according to one embodiment of the invention, the shape of the

Luneberg-type lens of the first antenna arrangement, with or without a ground plane, may be modified to allow radiant energy to be dispersed in a larger angular sector in elevation than in azimuth, or vice versa, to provide for asymmetrical cross-sectional radiation patterns from the first antenna arrangement. Fig. 10 is a diagram of an antenna system according to one embodiment of the invention employing such a first antenna arrangement. In the embodiment of Fig. 10, the first antenna arrangement 300 includes a generally non-spherically-shaped volumetric dielectric lens 310, and one or more antenna feed devices 40 coupled to the lens 310. While Fig. 10 illustrates the lens 310 essentially as an ellipsoid, it should be appreciated that the invention is not limited in this respect, as a variety of different lens shapes other than spherical are suitable for purposes of the invention in this embodiment. By employing a non spherically-shaped lens, a cross-sectional spatial profile of a radiation pattern radiated by the first antenna arrangement 300 may be asymmetrical in azimuth and elevation. Examples of some shapes suitable for purposes of the lens 310 in Fig. 10 include, but are not limited to, oblate spheroid, prolate spheroid, or a hybrid oblate-prolate spheroid geometry as required to obtain the desired spatial radiation patterns in the coverage volume. As in other embodiments, the first antenna arrangement 300 having the lens 310 may be coupled to one or more other antenna arrangements (e.g., the second antenna arrangement 320) to realize a multimode sectored antenna system according to one embodiment of the invention.

Having thus described at least one illustrative embodiment of the invention, various alterations, modifications and improvements will readily occur to those skilled in the art. Such alterations, modifications and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting. What is claimed is:

Claims

1. A multimode sectored antenna system, comprising: a first antenna arrangement to radiate a first radiation pattern into a coverage area; and a second antenna arrangement coupled to the first antenna arrangement to radiate a second radiation pattern into the coverage area, the second radiation pattern having a different spatial profile than the first radiation pattern.

2. The antenna system of claim 1, further including at least one additional antenna arrangement to radiate a third radiation pattern into the coverage area.

3. The antenna system of claim 1, wherein the first and second antenna arrangements are constructed and arranged so as to radiate the first and second radiation patterns simultaneously.

4. The antenna system of claim 1, wherein: the first antenna arrangement is constructed and arranged so as to radiate the first radiation pattern into a first portion of the coverage area; and the second antenna arrangement is constructed and arranged so as to radiate the second radiation pattern into a second portion of the coverage area.

5. The antenna system of claim 4, wherein the first and second portions of the coverage area at least partially overlap.

6. The antenna system of claim 4, wherein the first and second portions of the coverage area substantially overlap.

7. The antenna system of claim 1, wherein: the coverage area includes an azimuth plane; the coverage area spans up to 360 degrees around the antenna system in the azimuth plane; and the first antenna arrangement is constructed and arranged so as to radiate the first radiation pattern throughout at least a portion of the azimuth plane.

8. The antenna system of claim 7, wherein the first arrangement is constructed and arranged so as to radiate the first radiation pattern throughout substantially all of the azimuth plane.

9. The antenna system of claim 7, wherein the second antenna arrangement is constructed and arranged so as to radiate the second radiation pattern throughout substantially all of the azimuth plane.

10. The antenna system of claim 7, wherein: the coverage area is divided into a plurality of azimuth sectors in the azimuth plane; and the first antenna arrangement is constructed and arranged so as to radiate the first radiation pattern in at least some of the azimuth sectors in the azimuth plane.

11. The antenna system of claim 7, wherein: the first antenna arrangement is constructed and arranged so as to radiate the first radiation pattern at a first elevation angle relative to the azimuth plane; and the second antenna arrangement is constructed and arranged so as to radiate the second radiation pattern at a second elevation angle relative to the azimuth plane.

12. The antenna system of claim 11 , wherein the first and second elevation angles are the same.

13. The antenna system of claim 11 , wherein the first and second elevation angles are different.

14. The antenna system of claim 1 1, wherein the antenna system is constructed and arranged such that: the first radiation pattern has a first beamwidth in the azimuth plane; the second radiation pattern has a second beamwidth in the azimuth plane; and the first beamwidth and the second beamwidth are different.

15. The antenna system of claim 14, wherein the antenna system is constructed and arranged such that the first and second radiation patterns at least partially overlap in the azimuth plane.

16. The antenna system of claim 1 1 , wherein the antenna system is constructed and arranged such that a spatial profile of at least one of the first radiation pattern and the second radiation pattern is symmetrical in a first direction parallel to the azimuth plane and a second direction orthogonal to the azimuth plane.

17. The antenna system of claim 11 , wherein the antenna system is constructed and arranged such that a spatial profile of at least one of the first radiation pattern and the second radiation pattern is asymmetrical in a first direction parallel to the azimuth plane and a second direction orthogonal to the azimuth plane.

18. The antenna system of claim 11 , wherein the antenna system is constructed and arranged such that: the first radiation pattern includes a plurality of first radiation beams, each first radiation beam having a respective first beamwidth; and the second radiation pattern includes at least one second radiation beam having a second beamwidth.

19. The antenna system of claim 18, wherein the at least one second radiation beam includes a plurality of second radiation beams, the plurality of second radiation beams being less than the plurality of first radiation beams, each second radiation beam of the plurality of second radiation beams having a respective second beamwidth.

20. The antenna system of claim 19, wherein: the first antenna arrangement is constructed and arranged so as to radiate each first radiation beam at the first elevation angle relative to the azimuth plane; and the second antenna arrangement is constructed and arranged so as to radiate each second radiation beam at a second elevation angle relative to the azimuth plane.

21. The antenna system of claim 20, wherein the first and second elevation angles are the same.

22. The antenna system of claim 20, wherein the first and second elevation angles are different.

23. The antenna system of claim 20, wherein at least some of the second radiation beams overlap at least some of the first radiation beams in the azimuth plane.

24. The antenna system of claim 18, wherein the at least one second radiation beam overlaps at least some of the plurality of first radiation beams in the azimuth plane.

25. The antenna system of claim 24, wherein: a plurality of users are dispersed throughout a sector of the coverage area; at least two of the users in the sector receive the at least one second radiation beam; and each first radiation beam is received by only one respective user of the plurality of users in the sector.

26. The antenna system of claim 25. wherein at least two of the first radiation beams have a same first carrier frequency.

27. The antenna system of claim 26, wherein the at least one second radiation beam has a second carrier frequency different from the first carrier frequency.

28. The antenna system of claim 25, wherein each first radiation beam has a carrier frequency in a range of from approximately 28 GHz to approximately 31 GHz.

29. The antenna system of claim 25, wherein the at least one second radiation beam is received by all of the plurality of users in the sector.

30. The antenna system of claim 25, wherein: the sector of the coverage area spans 90 degrees in the azimuth plane; and the second beamwidth of the at least one second radiation beam spans up to 90 degrees in the azimuth plane.

31. The antenna system of claim 30, wherein the respective first beamwidth of each first radiation beam is less than the second beamwidth.

32. The antenna system of claim 30. wherein the respective first beamwidth of each first radiation beam is less than 45 degrees in the azimuth plane.

33. The antenna system of claim 30, wherein the respective first beamwidth of each first radiation beam is from approximately 3 degrees to approximately 15 degrees in the azimuth plane.

34. The antenna system of claim 1, wherein at least one of the first antenna arrangement and the second antenna arrangement includes at least one essentially planar array of antenna feed devices.

35. The antenna system of claim 1, wherein each of the first antenna arrangement and the second antenna arrangement includes at least one essentially planar array of antenna feed devices.

36. The antenna system of claim 1, wherein the first antenna arrangement includes a Luneberg-type lens having an essentially spherical shape.

37. The antenna system of claim 1, wherein the first antenna arrangement includes a Luneberg-type lens having an essentially hemispherical shape.

38. The antenna system of claim 37, further including a conductive ground plane coupled to the hemispherically shaped Luneberg-type lens.

39. The antenna system of claim 38, wherein: the conductive ground plane has a first side and a second side; the hemispherically shaped Luneberg-type lens is coupled to the first side of the conductive ground plane; and the second antenna arrangement is disposed proximate to the second side of the conductive ground plane opposite the lens.

40. The antenna system of claim 1, wherein the first antenna arrangement includes a Luneberg-type lens having an essentially non-spherical shape.

41. The antenna system of claim 40, wherein a spatial profile of the first radiation pattern is asymmetrical in two orthogonal planes passing through the first radiation pattern.

42. A wireless communication method, comprising steps of: radiating a first radiation pattern into a coverage area; and radiating a second radiation pattern into the coverage area, the second radiation pattern having a different spatial profile than the first radiation pattern.

43. The communication method of claim 42, further including a step of radiating a third radiation pattern into the coverage area.

44. The communication method of claim 42, wherein the step of radiating a second radiation pattern includes a step of simultaneously radiating a second radiation pattern into the coverage area.

45. The communication method of claim 42, wherein: the step of radiating a first radiation pattern includes a step of radiating a first radiation pattern into a first portion of the coverage area; and the step of radiating a second radiation pattern includes a step of radiating a second radiation pattern into a second portion of the coverage area.

46. The communication method of claim 45, wherein the first and second portions at least partially overlap.

47. The communication method of claim 45, wherein the first and second portions substantially overlap.

48. The communication method of claim 42, wherein: the coverage area includes an azimuth plane; the step of radiating a first radiation pattern includes a step of radiating a first radiation pattern at a first elevation angle relative to the azimuth plane; and the step of radiating a second radiation pattern includes a step of radiating a second radiation pattern at a second elevation angle relative to the azimuth plane.

49. A wireless communication antenna system, comprising: at least one Luneberg-type lens; at least one first antenna feed device coupled to the at least one Luneberg-type lens, the at least one first antenna feed device transmitting first radiation through the at least one Luneberg-type lens into a coverage area; and at least one second antenna feed device coupled to the at least one Luneberg-type lens, the at least one second antenna feed device positioned with respect to the at least one Luneberg-type lens so as to transmit second radiation into the coverage area, such that the second radiation does not propagate through the at least one Luneberg-type lens.

50. The system of claim 49, wherein the at least one second antenna feed device includes an array of antenna feed devices.

51. A wireless communication antenna system, comprising: a first antenna arrangement including: a Luneberg-type lens; and a plurality of antenna feed devices coupled to the at least one Luneberg- type lens, each feed device of the plurality of antenna feed devices transmitting respective first radiation through the Luneberg-type lens into a respective portion of a coverage area; and a second antenna arrangement coupled to the first antenna arrangement, the second antenna arrangement including at least one planar array of antenna feed devices, the at least one planar array transmitting second radiation into at least a portion of the coverage area.

52. The system of claim 51, wherein the second antenna arrangement includes at least four planar arrays of antenna feed devices.

53. The system of claim 52, wherein the at least four planar arrays are disposed with respect to each other so as to radiate the second radiation substantially throughout a 360 degree azimuth plane surrounding the antenna system.

54. The system of claim 53, wherein the plurality of feed devices coupled to the Luneberg-type lens are disposed with respect to each other so as to radiate the respective first radiation substantially throughout the 360 degree azimuth plane surrounding the antenna system.