Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
  • H01Q13/20—Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave
  • H01Q13/206—Microstrip transmission line antennas
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
  • H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
• • 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
  • H01Q3/28—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 amplitude

Definitions

• the present invention relates to an antenna for use in a base station in a cellular communication system, and more particularly to a microstrip antenna array which improves a base station's performance by increasing antenna gain and by reducing interference problems.
• Figure 1 illustrates ten cells C1-C10 in a typical cellular mobile radio communication system. Normally, a cellular mobile radio system would be implemented with more than ten cells. However, for the purposes of simplicity, the present invention can be explained using the simplified representation illustrated in Figure 1. For each cell, C1-C10, there is a base station B1-B10 with the same reference number as the corresponding cell. Figure 1 illustrates the base stations as situated in the vicinity of the cell center and having omnidirectional antennas.
• Figure 1 also illustrates nine mobile stations M1-M9 which are movable within a cell and from one cell to another. In a typical cellular radio system, there would normally be more than nine cellular mobile stations. In fact, there are typically many times the number of mobile stations as there are base stations. However, for the purpose of explaining the present invention, the reduced number of mobile stations is sufficient. Also illustrated in Figure 1 is a mobile switching center MSC.
• the mobile switching center MSC illustrated in Figure 1 is connected to all ten base stations Bl- B10 by cables.
• the mobile switching center MSC is also connected by cables to a fixed switching telephone network or similar fixed network. All cables from the mobile switching center MSC to the base stations B1-B10 and cables to the fixed network are not illustrated.
• the mobile switching center MSC there may be another mobile switching center connected by cables to base stations other than those illustrated in Figure 1.
• cables other means, for example, fixed radio links may also be used to connect base stations to the mobile switching center.
• the mobile switching center MSC, the base stations and the mobile stations are all computer controlled.
• each base station has an omnidirectional or directional antenna for broadcasting signals throughout the area covered by the base station.
• signals for particular mobile stations are broadcast throughout the entire coverage area regardless of the relative positions of the mobile stations.
• the transmitter may have one power amplifier per carrier frequency.
• the amplified signals are combined and connected to a common antenna which has a wide azimuth beam with for example 120 or 360 degrees coverage. Due to the wide beamwidth of the common antenna, the antenna gain is low and there is no spatial selectivity which results in interference problems.
• the microstrip antenna which is illustrated in Figure 2.
• the microstrip antenna consists of a conductive patch 10 formed on a dielectric substrate 12, and a ground plane 14 at a distance from the patch 10.
• the ground plane can be formed on the opposite side of the substrate 12, or the spacing between the patch and the ground plane can be completely or partially filled with air, foam, or some other dielectric material.
• the antenna elements can be etched onto a ⁇ per-laminated board. A number of elements can then be located on the same laminate. The elements are fed in series, in parallel or both by a feed network of connecting lines 16, in the same layer as the elements or in an other layer.
• Frequency and impedance characteristics of the microstrip antenna are a function of the antenna size, the input feed location, and the permitivity of the substrate.
• the polarization sensitivity of the antenna can be either vertical or horizontal or both depending upon the layout of the conductive patches 10.
• microstrip antennas have been limited because of their inherently narrow operating bandwidth.
• Microstrip antenna elements have a relatively narrow bandwidth, typically 2-5 percent. Coverage of a wider frequency band can be achieved through the use of stacked elements or slot-coupled elements.
• today's base stations use spatial diversity wherein two receiving antennas are typically separated by 20 or 30 wavelengths.
• the receiver diversity used today is less attractive with narrow beam, high gain antennas since they are more expensive and larger, giving both visual problems and mounting problems.
• an antenna for a base station in a mobile radio communication system with at least one base station and at least one mobile station comprises a microstrip antenna array with a matrix of microstrip patches with at least two columns and two rows.
• a plurality of amplifiers is provided wherein each power amplifier is connected to a different column of microstrip patches.
• beamforming means are connected to each power amplifier for dete ⁇ nining a direction and shape of narrow antenna lobes generated by the columns of microstrip patches.
• an antenna for a base station and a mobile radio communication system comprises a microstrip antenna array comprising a matrix of microstrip patches with at least two columns and two rows.
• a plurality of low noise amplifiers are used for filtering and amplifying the signals received by the microstrip antenna array, wherein each low noise amplifier is connected to a different column of microstrip patches.
• Beamforming means are connected to each low noise amplifier for dete ⁇ riining a direction and shape of narrow antenna lobes generated by the columns of microstrip patches.
• Figure 1 illustrates a portion of a cellular mobile communication system having cells, a mobile switching center, base stations, and mobile stations.
• Figure 2 illustrates a microstrip antenna
• Figure 3 illustrates a microstrip antenna array according to one embodiment of the present invention.
• FIG. 4 illustrates another microstrip antenna array according to another embodiment of the present invention.
• Figure 5 illustrates another microstrip antenna array according to another embodiment of the present invention.
• Figure 6 illustrates another microstrip antenna array according to another embodiment of the present invention.
• a microstrip antenna array as illustrated in Figure 3, can be used to increase the gain of the signals from the base station while lowering interference throughout the system.
• the antenna array 30 consists of a matrix of microstrip patches 32 which are formed above a common ground plane 34. The elements in each column are connected either in parallel, series, or both, by connecting lines 40. While Figure 3 illustrates six columns and four rows of patches, it will be understood by one skilled in the art that the antenna array can consist of any plurality of columns and rows.
• Each column of patches is connected to a different power amplifier 36 in the transmit direction and a different low noise amplifier 42 in the receive direction as illustrated in Figure 4.
• each column of patches can also be connected to a plurality of power amplifiers in the transmit direction and a plurality of low noise amplifiers in the reverse direction.
• the columns of patches can also be connected to linear power amplifiers.
• the power amplifiers and the low noise amplifiers are connected to a beamforming apparatus 38 which creates antenna beams with desired shapes in desired directions.
• the antenna array can generate a plurality of narrow azimuth beams or lobes, where the direction and shape of the antenna beams are determined in the beamforming apparatus 38 by signal amplitude and phase relations between different columns.
• the base station can use the narrow beams, which have a higher gain, to broadcast and receive signals from the mobile stations in the base station's coverage area.
• the beamforming can be implemented in a variety of ways such as digital beamforming, analog beamforming, or by a beamforming matrix, such as a Butler matrix.
• Analog beamformers steer the beam by introducing a frequency-independent time delay, while digital Deamforming usually involves a phase delay that is equivalent to the time delay at an operating frequency.
• a digital beamfo ⁇ ning system usually has a relatively simple receiver for each element, which down-converts the frequency into I and Q (in-phase and quadrature) channels for an A/D converter.
• Real-time beamforming takes place by multiplying these complex pairs of samples by appropriate weights in multiply/accumulate integrated circuits.
• the array output is formed from
• V n complex signal from n* channel
• W n weighting coefficient
• e ⁇ 2 n( / ⁇ ) ⁇ ⁇ _ steerm g phaseshift
• C B correction factor Corrections may be necessary for several reasons. These reasons include errors in the position of the element, temperature effects and the difference in behavior between those elements embedded in the array and those near the edge.
• a plurality of narrow beams can be used to simultaneously cover a large sector using the same antenna array.
• the present invention can use an adaptive algorithm for selecting the most feasible weight functions for the antenna.
• One such adaptive algorithm is disclosed in U.S. Patent Application No. 08/95,224 filed February 10, 1994 which is incorporated herein by reference.
• the patches in each column are polarized.
• the polarization can be either vertical or horizontal, or have dual polarization with two orthogonal polarization components.
• the two orthogonal components can for example be vertical and horizontal or diagonal polarization components.
• the simultaneous dual polarization the two orthogonal polarized signals are combined separately for each column, and connected to separated channels in the radio unit.
• the step of combining the signals can use any of the known combining schemes, for example, selection diversity, maximum ratio combining, etc.
• the arbitrary elliptical polarization state can then be obtained in both the transmit and receive directions.
• polarization diversity can be used to embrace the possibility to further suppress interferers and reduce the fading variations. This will remove the necessity to use space diversity.
• the present invention reduces the operate power level from each power amplifier, thus easing the requirements on the linear power amplifier technology.
• the system can also have the amplifiers and the beamforming apparatus permutated as illustrated in Figures 5 and 6.
• the amplifiers amplify the signals in the channels that correspond to specific antenna beams wherein the shape and directions of the beams are determined by the beamforming apparatus weights at that instance.
• the permutated system has the advantage that the independent channels do not require coherent amplifiers.
• fault detection of an amplifier is easy since each amplifier is associated with a specific channel.
• the system loss in the beamforming apparatus is reduced, the output power levels are reduced due to the distributed power amplification and the possibility for graceful degradation of system performance when amplifier faults occur.

Landscapes

• Variable-Direction Aerials And Aerial Arrays (AREA)
• Details Of Aerials (AREA)
• Mobile Radio Communication Systems (AREA)

Applications Claiming Priority (3)

Publications (1)

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Family Applications (1)

Country Status (7)

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Family Cites Families (3)

• 1995
  • 1995-05-31 EP EP95920361A patent/EP0763264A1/de not_active Withdrawn
  • 1995-05-31 WO PCT/SE1995/000623 patent/WO1995034102A1/en not_active Ceased
  • 1995-05-31 JP JP8500750A patent/JPH10501661A/ja active Pending
  • 1995-05-31 CN CN95193420.1A patent/CN1150498A/zh active Pending
  • 1995-05-31 FI FI964562A patent/FI964562L/fi unknown
  • 1995-05-31 CA CA002191956A patent/CA2191956A1/en not_active Abandoned
  • 1995-05-31 AU AU25835/95A patent/AU686388B2/en not_active Ceased

Non-Patent Citations (1)

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