The field of the invention relates to an active antenna array and a method for synthesizing antenna patterns of an active 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 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 station.
Nowadays active antenna arrays are used in the field of mobile communications networks in order to reduce power transmitted to a handset of a customer and thereby increase the efficiency of the base transceiver station. The base transceiver station has an antenna array connected to it by means of a fibre optics cable and a power cable. The antenna array typically comprises a plurality of antenna elements, which transceive a radio signal. The base transceiver station is coupled to a fixed line telecommunications network operated by one or more operators.
Typically the base transceiver 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 typically allows steering of a radio 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 mobile communications network are uniform linear arrays comprising a vertical column of antenna array elements. The active antenna array 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.
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 signals using protocols which are defined by communication standards. The communications standards typically define a plurality of channels or frequency bands useable for an uplink communication from the handset to the antenna array and base transceiver station as well as for a downlink communication from the base transceiver station to the subscriber device.
For example, the communication standards “Global System for Mobile Communications (GSM)” for mobile communications use 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 of communications standards include 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 product which is as small and cost-effective as possible. The antenna gain should be maximized without significant increase of antenna size and cost, and without significantly sacrificing the tilt range of the antenna.
According to one aspect of the present disclosure, an active antenna array is disclosed, which comprises a plurality of transceiver modules and an active antenna element subset of the plurality of antenna elements, wherein the active antenna element subset comprises at least one active antenna element being actively coupled to an associated transceiver module of the plurality of transceiver modules. The active antenna array further comprises at least one passively combined sub-array of at least two antenna elements of the plurality of antenna elements.
According to another aspect of the present disclosure, a method for generating antenna patterns with an antenna array having a plurality of antenna elements is disclosed, the method comprising: determining static phase relations for the antenna elements of at least one passively combined sub-array of at least two antenna elements of the plurality of antenna elements of the antenna array; determining dynamic beam forming parameters for an active antenna element subset of the plurality of antenna elements and for said at least one passively combined sub-array; and relaying a radio signal with an antenna pattern through the plurality of antenna elements based on the static phase relations and the dynamic beam forming parameters.
The term “active” or “actively” as used herein shall refer to comprising dynamically adaptable beam forming parameters. Analogously, “passive” or “passively” as used herein shall refer to comprising static phase relations.
a shows an antenna pattern of a lower passively combined sub-array of the active antenna array depicted in
b shows an antenna pattern of an upper passively combined sub-array of the active antenna array depicted in
a shows an overall antenna pattern of the active antenna array depicted in
b shows an overall antenna pattern of the active antenna array depicted in
c shows an overall antenna pattern of the active antenna array depicted in
d shows an overall antenna pattern of the active antenna array depicted in
e shows an overall antenna pattern of the active antenna array depicted in
f shows an overall antenna pattern of the active antenna array depicted in
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 active antenna array 3000 of
The first passive feed network 3006-1 connecting the upper sub-array 3005-1 with the common transceiver module 3003-1 associated to the upper sub-array 3005-1 may be adjusted by determining static phase relations v11, v21 for the antenna elements 3001-1,2 of the upper sub-array 3005-1. Such an adjustment of the upper sub-array 3005-1 may be performed by means of either mechanical tilting (e.g. using a stepper-motor or servo-motor based system for remotely moving the passive antenna's system tilt angle, by physically moving theof the upper sub-array 3005-1) or by means of a ‘remote electrical tilt’ (RET) system. The RET system typically utilizes motor-controlled phase shift elements to achieve a tilt of the beam formed from the radio signals. The phases and/or amplitudes of the antenna elements 3001-1,2 can thereby be progressively shifted in relation to each other in order to shape the beam of the antenna array 3000.
Analogously, the second passive feed network 3006-2 connecting the lower sub-array 3005-2 with the common transceiver module 3003-2 associated to the lower sub-array 3005-2 may be adjusted by determining static phase relations v12, v22 for the antenna elements 3001-7,8 of the lower sub-array 3005-2. Such an adjustment of the lower sub-array 3005-2 may be performed by means of either mechanical tilting or by means of a RET system, as described in the previous paragraph. The phases and/or amplitudes of the antenna elements 3001-7,8 can thereby be progressively shifted in relation to each other in order to shape the beam of the antenna array 3000.
The phases and/or amplitudes of the active antenna element subset 3001-3 through 3001-6 may be dynamically determined by beam forming parameters w3 through w6. The phases and/or amplitudes of the sub-arrays 3005-1,2 in relation to the active antenna element subset 3001-3 through 3001-6 may be dynamically determined by beam forming parameters w1 and w2, respectively.
In the example shown in
The active antenna array 4000 of
It should be noted that the active antenna array 4000 may alternatively comprise one or any other number K sub-arrays of N antenna elements 4001-1 through 4001-N, where K≦N/2. The sub-arrays 4005-1 through 4005-4 may be arranged such that there is one sub-array for each polarization located at the upper end and the lower end of the vertical column of antenna elements 4001-1 through 4001-16. The central active antenna element subset 4001-5 through 4001-12 is located between the sub-arrays 4005-1,2 and 4005-3,4. This allows for a so-called “tapered” antenna array as will be described below. However, the at least one central sub-array may be located at any suitable place in the active antenna array 4000. The active antenna array 4000 further comprises two pairs of common transceiver modules 4003-1,2, 11,12, which are associated to the upper sub-arrays 4005-1,2 and the lower sub-arrays 4005-3,4, respectively. The antenna elements 4001-1,3 of the first upper sub-array 4005,1 are coupled to the common transceiver module 4003,1 associated to the first upper sub-array 4005,1, the antenna elements 4001-2,4 of the second upper sub-array 4005,2 are coupled to the common transceiver module 4003,2 associated to the second upper sub-array 4005,2, the antenna elements 4001-13,15 of the first lower sub-array 4005,3 are coupled to the common transceiver module 4003,11 associated to the first lower sub-array 4005,3, and the antenna elements 4001-14,16 of the second lower sub-array 4005,4 are coupled to the common transceiver module 4003,12 associated to the second lower sub-array 4005,4. The number of common transceiver modules 4003-1 through 4003-K associated to the sub-arrays 4005-1 through 4005-K corresponds to the number K of sub-arrays 4005-1 through 4005-K of N antenna elements 4001-1 through 4001-N, where 1≦K≦N/2. In total, the number of transceiver modules 4003-1 through 3003-12, i.e. twelve in the example of
The pairs of the active antenna element subset 4001-5 through 4001-12 have a non-limiting spacing A of about 250 mm. The same distance A of about 250 mm is chosen for the spacing between the active antenna element subset 4001-5 through 4001-12 and the sub-arrays 4005-1,2. However, the pairs of the antenna elements 4001-1 through 4001-4 of the upper first and second sub-array 4005-1,2 have a smaller non-limiting spacing B of about 140 mm. In a symmetric way, the pairs of the antenna elements 4001-13 through 4001-16 of the lower third and fourth sub-array 4005-3,4 have also a non-limiting spacing B of about 140 mm. Strictly speaking, the antenna array 4000 of
In comparison to a six pair linear antenna array, the eight pair non-linear antenna array 4000 shown in
a illustrates the antenna pattern of the lower sub-array 4005-3, 4005-4 over the elevation angle in degrees. Within the tilt range of the overall active antenna array 4000 (typically below 20°), the antenna pattern is relatively flat. This provides flexibility in beam tilting. A similarly flat antenna pattern of the upper sub-array 4005-1,2 is shown in
while the complex static phase relations v11, v21 for a top sub-array 4005-1,2 have been determined to be
whereby φ1 and φ2 represent the phase.
As can be understood from the formulae, for the top sub-array and the bottom sub-array 4005-1 through 4005-4, the amplitudes of the complex static phase relations v11, v21 and v12, v22, respectively, are not distributed equally between the two passively combined antenna elements. This allows the realization of a tapered antenna array pattern, which significantly provides a better side lobe suppression without significant compromises in performance. In contrast to that, with a six pair linear antenna array, tapering of the antenna array possible would only be possible by reducing signal power of the antenna elements situated at the ends of the linear antenna array. The reducing of the signal power, however, decreases the overall output power and therefore reduces overall power efficiency of the antenna array.
The present disclosure provides a solution for providing a tapered antenna array pattern without the need for different ones of the antenna elements having different output powers (which would increase system complexity, reduces total output power and reduces system efficiency), because static phase relations v11, v21 and v12, v22 between the antenna elements 4001-1 through 4001-4 and 4001-13 through 4001-16 of the passively combined sub-arrays 4005-1 through 4005-4 at the ends of the antenna array 4000 may be determined appropriately. It should be understood that a similarly tapered antenna array pattern can also be achieved with the antenna array 3000 shown in
Once the static phase relations v11, v21 and v12, v22 for the sub-arrays have been determined, an overall pattern synthesis is possible by determining the complex beam forming weights w1 through w12 for each one of the transceiver modules 4003-1 to 4003-12 by applying suitable optimization techniques under the condition of the requirements regarding beam pattern shape and tilt angle. The complex beam forming weights w1 through w12 for the twelve transceiver modules 4003-1 to 4003-12 have to be chosen such that the superposition of the beam patterns of the sub-arrays 4005-1 through 4005-4 and active antenna elements 4001-5 through 4001-12 yields a desired overall beam pattern. The complex beam forming weights w1 through w12 can generally not simply be obtained by phase progression as it is commonly done for classical linear arrays, but the complex beam forming weights w1 through w12 have to be designed taking into account the beam patterns of the static sub-arrays 4005-1 through 4005-4, which cannot be modified dynamically during operation.
To obtain the static sub-array weights v1i, v2i for each sub-array i as well as the adjustable beam forming weights wj for each the active transceiver modules j, synthesis techniques can be used, which are based on suitable optimization techniques. Generally, such optimization techniques may require non-linear objective functions or constrains. It turned out that optimization algorithms based on swarm optimization techniques and/or genetic algorithms (e.g. described in D. W. Boeringer, D. H. Werner, “Particle Swarm Optimization Versus Genetic Algorithms for Phased Array Synthesis”, IEEE Transactions on Antennas And Propagation, Vol. 52, No. 3, March 2004) are well suited for such purposes.
Using optimization algorithms based on swarm optimization and genetic algorithms, the overall antenna patterns depicted in
and M≦N/2. A second determining step 7002 comprises determining a dynamic beam forming parameter w1 through wj for each j of a subset of n active antenna elements of the plurality of N antenna elements and for each i of said M sub-arrays, where n+M=J≦N−1. A third determining step 7003 comprises relaying a radio signal with an antenna pattern through the plurality of N antenna elements based on the static phase relations v1i through viK
The static phase relations v1i through viK
The determining steps 7001 and/or 7002 may use optimization algorithms based on swarm optimization techniques and/or genetic algorithms, which may be performed under the condition that the variety of beam forming parameters that do not significantly restrict the flexibility in antenna patterns, in particular beam forming or tilt range, is maximized. The determining steps 7001 and/or 7002 may be alternatively or additionally performed under the condition that the variety of beam forming parameters that do not significantly restrict the flexibility in beam forming or tilt range is maximized.
To achieve an antenna pattern that comes closest to a desired antenna pattern, the determining steps 7001 and/or 7002 may be iteratively repeated. However, the second determining step 7002 may be performed dynamically at any time during operation of the antenna array or at an idle state of the antenna array, whereas the first determining step 7001 may only performed during an idle state of the antenna array.
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.
This application is a continuation of U.S. patent application Ser. No. 13/016,417, filed Jan. 28, 2011. The entire disclosure of the foregoing application is hereby incorporated herein by reference.
Number | Date | Country | |
---|---|---|---|
Parent | 13016417 | Jan 2011 | US |
Child | 14486300 | US |