Patent Application
20120194385
None
The field of the invention relates to an antenna array and a method for operating such an antenna array.
The use of mobile communications networks has increased over the last decade. Operators of the mobile communications networks have increased the number of base transceiver stations in order to meet an increased demand for service by users of the mobile communications networks. The operators of the mobile communications network wish to reduce the running costs of the base transceiver station.
Nowadays active antenna arrays are used in the field of mobile communications systems in order to reduce power transmitted to a handset of a customer and thereby increase the efficiency of the base transceiver station, i.e. the radio station. The radio station typically comprises a plurality of antenna elements, i.e. an antenna array adapted for transceiving a payload signal. Typically the radio station comprises a plurality of transmit paths and receive paths. Each of the transmit paths and receive paths are terminated by one of the antenna elements. The plurality of the antenna elements used in the radio station typically allows steering of a beam transmitted by the antenna array. The steering of the beam includes but is not limited to at least one of: detection of direction of arrival (DOA), beam forming, down tilting and beam diversity. These techniques of beam steering are well-known in the art.
The active antenna arrays typically used in the mobile communications network are uniform linear arrays comprising a vertical column of pairs of antenna array elements. The active antenna array or active antenna system is typically mounted on a mast or tower. The active antenna array is coupled to the base transceiver station (BTS) by means of a fibre optics cable and a power cable. The base transceiver station is coupled to a fixed line telecommunications network operated by one or more operators.
Equipment at the base of the mast as well as the active antenna array mounted on the mast is configured to transmit and receive radio signal within limits set by communication standards.
The code sharing and time division strategies as well as the beam steering rely on the radio station and the active antenna array to transmit and receive within limits set by communication standards. The communications standards typically provide a plurality of channels or frequency bands useable for an uplink communication from the handset to the radio station as well as for a downlink communication from the radio station to the subscriber device.
For example, the communication standard “Global System for Mobile Communications (GSM)” for mobile communications uses different frequencies in different regions. In North America, GSM operates on the primary mobile communication bands 850 MHz and 1900 MHz. In Europe, Middle East and Asia most of the providers use 900 MHz and 1800 MHz bands. Other examples are the UMTS standard or long term evolution (LTE) at 700 MHz (US) or 800 MHz (EU).
As technology evolves, the operators have expressed a desire for an active antenna array which is as cost-effective as possible. The side lobe suppression should be maximized without significant increase of antenna size and cost, and without significantly sacrificing the tilt range of the antenna.
A partitioned aperture array antenna is known from US Patent Application Publication No. 2010/0060517 A1 (Nichols et al.). The antenna array described therein includes a first passively combined sub-array having a first number of antenna elements equipped with transmit functionality and a second passively combined sub-array having a second number of antenna elements equipped with receive functionality, wherein the first number of antenna elements and the second number of antenna elements are not equal to each and the first sub-array and the second sub-array have at least one common antenna element.
It is, however, not desired to have different passively combined sub-arrays with separate transmit functionality and receive functionality. For most communications standards, such as LTE MIMO communications for instance, it is desired to use the same configuration and therefore the same antenna elements for both transmission and reception of radio signals. The antenna array should be able to radiate the radio signals from different carriers with different beam patterns, which may be dynamically modified during operation of the antenna array.
According to one aspect of the present disclosure, an active antenna array having a plurality of antenna elements is disclosed. The active antenna array comprises at least one first subset of the plurality of antenna elements, the at least one first subset relaying a first radio signal having a first antenna beam pattern, and at least one second subset of the plurality of antenna elements, the at least one second subset relaying a second radio signal having a second antenna beam pattern. At least one of the plurality of antenna elements is a common antenna element belonging to both the first subset and the second subset.
It will be appreciated that there may be more than one first subset of the plurality of antenna elements and more than one second subset of the plurality of antenna elements. In other words, there may be a plurality of subsets of the plurality of antenna elements. There will be at least one common antenna element that is common to two of the plurality of subsets. There may be more than one common antenna element, but each one of plurality of subsets will generally have only a single common antenna element. In other words, there will generally not be two common antenna elements in any one subset of the plurality of antenna elements. Not all of the subsets need include one of the common antenna elements. The skilled person will appreciate further that it would be possible to include two common antenna elements in one subset, but this would lead to a loss of flexibility.
According to another aspect of the present disclosure, a method for operating an active antenna array having a plurality of antenna elements is disclosed. The method comprises relaying a first radio signal having a first antenna beam pattern through a first subset of the plurality of antenna elements, and relaying a second radio signal having a second antenna beam pattern through at least one second subset of the plurality of antenna elements, At least one of the plurality of antenna elements is used as a common antenna element belonging to both the first subset and the second subset.
The term “relaying” as described herein shall be construed as comprising a transmitting by the antenna element or a receiving by the antenna element, or both. The term “relayed power” as described herein shall be construed as comprising a transmitted power or a received power, or both.
a shows an overall antenna pattern of an eight elements active antenna array with two disjoint subsets of four active antenna elements each;
b shows an overall antenna pattern of the eight elements active antenna array of
The invention will now be described on the basis of the drawings. It will be understood that the embodiments and aspects of the invention described herein are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalents. It will be understood that features of one aspect or embodiment of the invention can be combined with a feature of a different aspect or aspects and/or embodiments of the invention.
The term “base transceiver station (BTS)” in the context of this disclosure includes, but is not limited to, base stations, as known from GSM networks, as well as a node B (known from UMTS/3G networks) or enhanced node B, and similar units used in other mobile communication network.
In the aspect shown in
The active antenna array 3000 shown in
The central antenna element 3001-5 is therefore a common antenna element belonging to both the upper first subset 3005-1 and the lower second subset 3005-1. As indicated by the encircled power fractions in
In order to achieve a symmetric tapering effect resulting in an enhanced side lobe suppression for both the first and the second antenna beam pattern, some of the antenna elements 3001-1 to 3001-9 of the active antenna array 4000 may be configured to relay radio signals with different radio signal power. To achieve this, the associated transceiver modules 3003-1 to 3003-9 may be configured to change their total output power, as will be discussed below.
It will be understood that it is not just the outermost antenna elements 3001-1 to 3001-9 of the active antenna array 30004000 which are involved in tapering, but also the centre antenna element 3001-5. The common antenna element 3001-53005 is in both the upper first subset 3005-1 and the lower second subset 3005-2. The common antenna element 3001-5 is supplied with the same amount of power as the outermost antenna element 3001-1 from the first subset 3005-1 to which is added the same amount of radio signal power supplied to the outermost antenna element 3001-9 from the second subset 3005-1.
At the first glance, it may appear as a significant drawback for beam forming, that the phase of the outermost antenna elements 4001-1 and 8 can only be modified together through the beam forming parameter w1 for the common transceiver module 4003-1. However, since beam forming only relies on phase differences between the antenna elements of the respective subset and not on absolute phases, the example presented in
In the example shown in
The active antenna array 5000 shown in
The central antenna elements 5001-4 and -5 are therefore common antenna elements belonging to both the upper first subset 5005-1 and the lower second subset 5005-1. As indicated by the encircled power fractions in
The antenna element 5001-3 relays the first signal with a total radio signal power, with which the antenna element 5001-3 is configured to relay radio signals. Analogously, the antenna elements 5001-6 relays the second signal with a total radio signal power, with which the antenna element 3001-6 is configured to relay radio signals. The two antenna elements 5001-3 and 6 constitute the central antenna elements of the upper first subset 5005-1 and the lower second subset 5005-2, respectively.
In order to achieve a symmetric tapering effect resulting in an enhanced side lobe suppression for both the first antenna beam pattern and the second antenna beam pattern, the outermost antenna elements 5001-1,2 and 5001-7,8 of the active antenna array 5000 may be configured to relay with reduced radio signal power. For the upper first subset 5001-1, the outermost antenna element 5001-1 may be configured to relay the first radio signal with only one third of its total radio signal power. The second outermost antenna element 5001-2 of the upper first subset 5005-1 may be configured to relay the first radio signal with only two thirds of its total radio signal power. Thereby, a symmetric tapering effect is achieved for the first antenna beam pattern. Analogously, for the lower second subset 5001-2, the outermost antenna element 5001-8 may be configured to relay the second radio signal with only one third of its total radio signal power. The second outermost antenna element 5001-7 of the lower second subset 5005-2 may be configured to relay the second radio signal with only two thirds of its total radio signal power. Thereby, a symmetric tapering effect is achieved for the second antenna beam pattern. If each of the outermost antenna elements 5001-1,2 and 5001-7,8 was connected to its own associated transceiver module, the associated transceiver modules could be configured to reduce their total output power accordingly (analogous to
However, similarly to the active antenna array 4000 shown in
The fourthforth transceiver module 5003-4 is connected to the fourthforth common element 5001-4 and supplies one third of the radio power for radio signals transmitted from the first subset 5005-1 as well as one third of the power for radio signals transmitted from the second subset 5005-2. The fifth transceiver module 5003-5 is connected to the fifth common antenna element 5001-5 which transmits one third of the power of the radio signals from the first subsets 5005-1 and two thirds of the power of the radio signals from the second subset 5005-2.
In the example in
Again, at the first glance, it may appear as a significant drawback for beam forming, that the phase of the antenna elements 5001-1,7 and 5001-2,8 can only be modified together through the beam forming parameters w1 and w2 for the common transceiver modules 4003-1,2. However, since beam forming only relies on phase differences between the antenna elements of the respective subset and not on absolute phases, the example presented in
a shows an overall beam pattern of an eight elements antenna array which comprises two disjoint subsets, e.g. an upper first subset comprising the upper four elements and a lower second subset comprising the lower four elements. Here, all eight antenna elements relay with their full total radio signal power. In comparison,
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant arts that various changes in form and detail can be made therein without departing from the scope of the invention. In addition to using hardware (e.g., within or coupled to a central processing unit (“CPU”), micro processor, micro controller, digital signal processor, processor core, system on chip (“SOC”) or any other device), implementations may also be embodied in software (e.g. computer readable code, program code, and/or instructions disposed in any form, such as source, object or machine language) disposed for example in a computer useable (e.g. readable) medium configured to store the software. Such software can enable, for example, the function, fabrication, modelling, simulation, description and/or testing of the apparatus and methods describe herein. For example, this can be accomplished through the use of general program languages (e.g., C, C++), hardware description languages (HDL) including Verilog HDL, VHDL, and so on, or other available programs. Such software can be disposed in any known computer useable medium such as semiconductor, magnetic disc, or optical disc (e.g., CD-ROM, DVD-ROM, etc.). The software can also be disposed as a computer data signal embodied in a computer useable (e.g. readable) transmission medium (e.g., carrier wave or any other medium including digital, optical, analogue-based medium). Embodiments of the present invention may include methods of providing the apparatus described herein by providing software describing the apparatus and subsequently transmitting the software as a computer data signal over a communication network including the internet and intranets.
It is understood that the apparatus and method describe herein may be included in a semiconductor intellectual property core, such as a micro processor core (e.g., embodied in HDL) and transformed to hardware in the production of integrated circuits. Additionally, the apparatus and methods described herein may be embodied as a combination of hardware and software. Thus, the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
