Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/12—Supports; Mounting means
  • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
  • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
  • H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
  • H01Q1/246—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for base stations
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q23/00—Antennas with active circuits or circuit elements integrated within them or attached to them
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
  • H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
  • H01Q3/267—Phased-array testing or checking devices
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
  • H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
  • H01Q3/30—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array
  • H01Q3/34—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array by electrical means
  • H01Q3/40—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array by electrical means with phasing matrix

Definitions

• the invention relates to a fixed beam antenna array and to a base station of a mobile communication network, . in particular a cellular mobile communication network, with beam selection.
• the invention equally relates to a method for transmitting signals via a fixed beam antenna array.
• Two different approaches are employed for increasing the downlink capacity in a base station site where antenna arrays are. sed for sectorised coverage: making the sectors narrower or using beamforming techniques.
• a beam in this sense is a region of high signal strength.
• One beam forming technique known from the state of the art is the fixed beam (or smart antenna) approach, which makes use of passive beamforming means like a Butler matrix. Such a technique is described for example in a product sheet "Smart Antenna Module" by Northern Telecom Europe Limited, 1992.
• Fixed beams have a dedicated direction and mobile stations being allocated in the sector of a directed beam use the available channels of this beam. In case the mobile station moves through a sector and leaves the sector of coverage of one beam, handover procedures ascertain that the mobile station uses the available channels of the next beam.
• the signals generated in the base station are passed on via power amplifiers to a Butler matrix, where the signals to be applied to the antenna elements are adjusted in order to form the selected beam.
• the fixed beam approach has the advantage that no antenna calibration is needed.- It has the disadvantage, however, that beam specific power amplifiers designed for high power levels are required. This means that the power amplifiers do not work linearly, which makes necessary measures of linearisation.
• Another known concept is embodied in active antenna systems, e.g. the Raytheon antenna systems, which comprise ordinary sector antennas with integrated PAs and LNAs.
• a further known beam forming technique is digital beamforming.
• the beamforming means is a digital beamformer, the outputted beams being fully steerable.
• the direction of the beam can therefore be adapted to transmission needs.
• the beam may for example move along with a mobile station through the whole sector of coverage of the antenna array.
• Digital beamforming requires calibration of the power amplifiers but is more flexible and allows more uniform power distribution over linear power ' amplifiers. This approach would be rather expensive to implement with some systems, though.
• WCDMA Wide Band Code Division Multiple Access
• Today's single sector antenna has usually 8-20 antenna elements connected in a form of a vertical column. The more elements in a column the narrower is the beam vertically and the greater is the antenna gain. Vertical beam width is usually 5-10 degrees while the horizontal beam width may be e.g. 65-110 degrees. Thus, if a multibeam antenna array is desired with narrow beamwidth for a macro site the antenna panel may include for example a 4x20 or a 8x12 matrix of antenna elements.
• a fixed beam antenna array with at least one column of antenna elements for transmitting generated signals, each column comprising at least one antenna element, the fixed beam antenna array comprising beamforming means for- adjusting phase angle and/or amplitude of at least one of said generated signals, and at least one active power amplifier respectively assigned to one of said columns of antenna elements and arranged between said beamforming means and said columns for amplifying the signals outputted by said beamforming means and for forwarding the amplified signals to the column of antenna elements to which it is assigned.
• the upper limit is preferably - but not necessarily - one PA for each antenna element, respectively.
• the lower limit is preferably defined by one PA per antenna column. Defining the number of PAs for a particular antenna arrangement is an optimisation problem.
• a base station of a mobile communication network in particular a cellular mobile communication network, comprising a fixed beam antenna array according to one of the preceding claims and a transceiver unit generating signals to be transmitted by the fixed beam antenna array and receiving signals received by the fixed beam antenna array.
• a method for transmitting generated signals via a fixed beam antenna array with at least one column of antenna elements, each column comprising at least one antenna element comprising the following steps: a) adjusting phase angle and/or amplitude of at least one of said generated signals in a beamforming means (BM) for a specific one of the columns of antenna elements in order to form beams; b) amplifying the signal outputted by the beamforming means by a phase calibrated active power amplifier assigned to said specific column of antenna elements; and c) transmitting the amplified signals via the antenna elements of said column of antenna elements.
• BM beamforming means
• the fixed beam antenna array, the base station and the method according to the invention combine the advantages of active and passive smart antennae. More precisely, the solution according to the invention takes advantage of the increased antenna gain of the narrow beams of smart antenna arrays and of significantly lower power levels per PA unit than with active antennas.
• the narrow beams achieved by the passive beamforming means lead to an increased antenna gain, the low powers of each antenna element being coherently combined in the radio path.
• an increased downlink capacity is achieved.
• Narrow beams moreover lead to a decreased total base station power.
• Four beams mean e.g. a four-fold decrease in power.
• the power amplifiers employed are active power amplifiers and situated on the antenna side of the beamforming means.
• the power amplifiers are therefore antenna specific, not beam specific. This way, the decreased total power can be distributed evenly to a large number of small power power amplifiers, which leads to a power balance between the amplifiers and to a significantly smaller power level per amplifier than with smart antenna arrays.
• the .power in each power amplifier depends on how many mobiles are in the beam served by that power amplifier. If the mobiles all cluster in one beam, all the transmission power has to be supplied by one power amplifier.
• the array according to the invention needs eight 2.5 W amplifiers (8x2,5 W) .
• power amplifiers are beam specific. When all mobile stations are in the same beam, a power amplifier with a power of 20 W is needed for this beam. This means, in the worst case eight 20 power amplifiers -(8x20 W) are needed.
• the power level of a single power amplifier can be designed to such a low value, e.g. less than 1 W, that linearisation is not required.
• the resulting low joint temperature moreover leads to a high reliability of the antenna array and a large MTBF (Mean Time Between Failure) .
• the losses in the beamforming means can be avoided, since with the power amplifiers situated on the antenna side,- there is no high power fed into the beamforming means. Because of the number of splitters, phase shifters and combiners in beamforming means like a Butler matrix, the power loss in known fixed beam antenna arrays can be significant.
• a modular solution is obtained, which means a varying number of similar units can be employed, adapted to the needs of the respective base station.
• This allows a simplified construction of antenna arrays.
• the proposed solution allows a simpler and more efficient design of antenna arrays and base stations as well as a simpler and more efficient method, in which the same baseband engine can operate active fixed beams or ordinary diversity branches. If e.g. dual branch diversity is required, then e.g. dual polarized antenna elements AE may be used. In that case also the BM, the U unit and the CC unit have to be provided twice.
• the antenna elements, the beamforming means and the power amplifiers are integrated on the antenna panel.
• the beamforming means is an analogue phasing matrix, in particular a Butler matrix, especially a micro strip phasing network.
• Digital beamforming e.g. a digital Butler matrix
• a digital Butler matrix can also be applied.
• reception branches are comprised for receiving signals via the antenna elements of the antenna columns.
• Each reception branch comprises a low noise amplifier for increasing the reception quality of the received signals.
• each low noise amplifier is connected together with one of the power amplifiers respectively via duplexers to one of the columns of antenna elements on the one hand and the beamforming means on the other hand.
• Low noise amplifiers and duplexers are preferably also integrated on the antenna panel . Since the power amplifiers are positioned on the antenna side of the beamforming means, they have to be calibrated in phase by a calibration circuit. This is essential because the channels of the signals have to be exactly in the same phase at each antenna element of the antenna array. In known fixed beam antenna arrays a calibration is not necessary, since the signals are amplified before entering the beamforming means, the channels being provided to the antenna elements directly by the beamforming means. A calibration may be achieved with a calibration circuit or by accordingly matching the low noise amplifier/power amplifier units.
• a calibration circuit is used, it is preferably integrated in the antenna panel. This leads to a compact calibration structure with small calibration loops and enables an increased integration. In addition, no cables are required for calibration between the base station and the antenna panel .
• the antenna panel is an independent unit which can be connected to any base station being able to handle a certain number of antenna ports. Moreover, by such an integration, i.e. in the case that analog beamforming means are in a mast, the baseband ASIC requirements are reduced in comparison to digital beamforming means at baseband.
• the fixed beam solution according to the invention is particularly suited for WCDMA and GSM (Global System for Mobile Communication) , in particular EDGE (Enhanced Data rates for GSM Evolution) .
• WCDMA and smart antenna arrays for GSM requiring multicarrier power amplifiers both need linearised power amplifiers.
• WCDMA uplink coverage and downlink capacity can be increased with the solutions according to the invention.
• the bandwidth of a single carrier is about 200kHz.
• the production of a multicarrier power amplifier PA for the GSM system is in principle easier than for the WDMA system where a single carrier covers about 5 MHz bandwidth.
• the design difficulty strongly depends on the actually used modulation sheme. Thus, e.g. for GSM modulation and specification the design is difficult.
• Multicarrier power amplifiers can also be designed for WCDMA; the design becomes easier when the power levels are reduced.
• Fig. 1 shows an antenna array according to the invention
• Fig. 2 shows an antenna array according to the invention in more detail.
• Figure 1 depicts a four-beam antenna array of a macro site base station with a two-dimensional matrix of antenna elements AE.
• the matrix is made up of four columns AC1-AC4 of antenna elements AE arranged on an antenna panel AP.
• Each column AC1-AC4 comprises four antenna elements AE.
• Each of the columns AC1-AC4 is connected to a unit ⁇ with low noise amplifiers, active, linear power " amplifiers, duplexers and filters.
• a calibration circuitry CC has access to the inputs and outputs of the unit ⁇ .
• the unit ⁇ is moreover connected to a Butler matrix BM.
• the unit U comprising low noise amplifiers, power amplifiers, duplexers and filters is integrated on the antenna panel AP.
• the calibration unit CU and the Butler matrix BM are integrated on the antenna panel AP.
• the functioning of the antenna array of figure 1 is the following:
• a transceiver unit (not shown) of the base station generates signals that are to be transmitted and processes signals received by the antenna elements AE.
• the transceiver unit forwards the generated signals to the Butler matrix BM.
• the Butler matrix BM adjusts the phase angle and/or the amplitude of the signals to be applied to the antenna elements AE for transmission, thereby enabling a transmission with fixed beams, the narrow beams resulting in an increased antenna gain. Significant losses in the Butler matrix BM are avoided, since no high power is fed into the Butler matrix BM.
• the duplexers of the unit ⁇ comprise separate transmit Tx branches with power amplifiers and receive Rx branches with low noise amplifiers.
• the signals outputted by the Butler Matrix BM are forwarded by the duplexers to the active power amplifiers, where they are amplified.
• the amplified signals are then passed on to the corresponding antenna elements AE for transmission.
• the total base station transmission power is divided evenly between all power amplifiers, therefore the power level of the power amplifiers can be even less than 1 W. Accordingly, linearisation for the power amplifiers is not needed.
• the signals received by the antenna elements AE are forwarded via duplexers of unit U to the filters and the low noise amplifiers.
• the low noise amplifiers increase the reception quality of the signals, before passing them on via the Butler matrix BM to the transceiver unit for further processing.
• Both, the transmit as well as the receive signals are band-pass filtered by the filters in the U unit.
• the calibration circuitry CC is provided for calibrating the whole unit ⁇ comprising low noise amplifiers, power amplifiers, duplexers and filters. More specifically, the unit ⁇ makes sure that the phase angle of each branch from the butler matrix BM to the corresponding antenna column AC 1...4 is within calibration accuracy. Thus, the phase shifts that were set by the BM for each branch remain the same at the antenna columns. Calibration should compensate for the phase shifts not only due to the power amplifiers PAs but also due to the duplexers, the filters and the LNAs .
• Figure 2 shows a fixed beam antenna array according to the invention in more detail, illustrating the modular design of the antenna array. Corresponding elements are designated with the same reference signs as in Figure 1.
• each power amplifier/low noise amplifier unit U1-U4 comprises two duplexers D1,D2.
• One of the duplexers Dl connects the power amplifier PA and the low noise amplifier LNA with the antenna column AC1-AC4 and the other duplexer D2 connects the power amplifier PA and low noise amplifier LNA to a Butler matrix BM made up of a micro strip phasing network.
• the duplexers Dl,D2 ensure that only the signals to be transmitted are amplified by the power amplifier PA and that only the received signals are processed by the low noise amplifier LNA.
• All power amplifier/low noise amplifier units U1-U4 have an identical design, allowing a simplified construction of different antenna arrays. The total transmission power is distributed equally on all four power amplifiers PA and the transmission power in each power amplifier PA is minimised.
• the Butler matrix BM is moreover connected to antenna feeders, by which signals are provided to and received from the Butler matrix BM.
• the power amplifier/low noise amplifier units U1-U4 are calibrated by the calibrating circuitry CC, in order to ensure that the phase angle -of each branch from the butler matrix BM to the corresponding antenna column AC 1...4 is within calibration accuracy.
• the functioning of the fixed beam antenna array of figure 2 is basically the same as the functioning of the antenna array in figure 1.
• each power amplifier serves several antenna elements. However, if each unit would serve only one or two antenna elements, more power amplifiers would be required but the power per power amplifier could be further decreased. This is actually an optimisation problem in which such power amplifiers are to be employed which do not need linearisation and which are to run at a power level which gives good efficiency and reliability.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Mobile Radio Communication Systems (AREA)
• Variable-Direction Aerials And Aerial Arrays (AREA)
• Radio Transmission System (AREA)

Applications Claiming Priority (1)

Publications (2)

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ID=8164083

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• 2000
  • 2000-09-02 WO PCT/EP2000/008583 patent/WO2002019470A1/fr active IP Right Grant
  • 2000-09-02 DE DE60027208T patent/DE60027208T2/de not_active Expired - Lifetime
  • 2000-09-02 AT AT00962430T patent/ATE322750T1/de not_active IP Right Cessation
  • 2000-09-02 ES ES00962430T patent/ES2259611T3/es not_active Expired - Lifetime
  • 2000-09-02 EP EP00962430A patent/EP1314223B1/fr not_active Expired - Lifetime
  • 2000-09-02 AU AU2000274162A patent/AU2000274162A1/en not_active Abandoned
  • 2000-09-02 CN CN00819898.5A patent/CN1454404A/zh active Pending

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