Wireless communication device and beam control method

Abstract

To provide a wireless communication device capable of reliably obtaining an optimum weight value for reducing sidelobe output in a specific direction.SOLUTION: A wireless communication device obtains a weight vector corresponding to a maximum eigenvalue of the matrix obtained by subtracting a matrix obtained by multiplying the reduction ratio for reducing the output of a sidelobe of a first beam that interferes with the main lobe of a second beam by a second matrix representing the output of the sidelobe of the first beam from a first matrix that represents the output of the main lobe of the first beam and a plurality of antenna elements that output the first beam and the second beam on the basis of a weight vector that represents weighting for the gain and the phase; determines whether the ratio of the output of the main lobe of the first beam obtained by multiplying the first matrix by the weight vector and the complex conjugate transpose for the output of the side lobe of the first beam obtained by multiplying the second matrix by the weight vector and the complex conjugate transpose is greater than the maximum SIRmax; and extracts the weight vector when it is determined that the ratio is not greater than the maximum SIRmax.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a wireless communication device and a beam control method. [Background technology]

[0002] Conventionally, when outputting a beam from an array antenna in which multiple antennas are arranged in an array, there has been a method of determining weights to be assigned to the gain and / or phase of signals output from the multiple antennas based on the BAT algorithm (BAT algorithm) in order to reduce the output of side lobes in a specific direction (see, for example, non-patent document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Xiao XIAO, et. al. "Data Based Model for Wide Nulling Problem in Adaptive Digital Beamforming Antenna Array," IEEE Antennas and Wireless Propagation Letters, vol. 18, No.11, 2019. Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional methods that use iterative calculations such as the BAT algorithm, it is difficult to avoid falling into a local minimum, and there is a problem that it is not always possible to find the optimal weighting value for reducing the side lobe output in a specific direction.

[0005] It is therefore an object of the present invention to provide a wireless communication device and a beam control method that can reliably find the optimum weighting value for reducing the output of a side lobe in a specific direction. [Means for solving the problem]

[0006] A wireless communication device according to an embodiment of the present invention includes a plurality of antenna elements that output a first beam and a second beam based on a weight vector that represents weighting for gain and / or phase; a weight vector derivation unit that obtains a weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting from a first matrix that represents the output power of a main lobe of the first beam a matrix obtained by multiplying a reduction rate for reducing the output power of a side lobe of the first beam that interferes with the main lobe of the second beam by a second matrix that represents the output power of the side lobe of the first beam; a determination unit that determines whether a power ratio of the output power of the main lobe of the first beam, obtained by multiplying the first matrix by the weight vector and the complex conjugate transpose of the weight vector, to the output power of the side lobe of the first beam, obtained by multiplying the second matrix by the weight vector and the complex conjugate transpose of the weight vector, is greater than a maximum SIRmax; and a weight extraction unit that extracts the weight vector when the determination unit determines that the power ratio is not greater than the maximum SIRmax. Effect of the Invention

[0007] It is possible to provide a wireless communication device and a beam control method that can reliably find the optimum weighting value for reducing the output of a side lobe in a specific direction. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 shows two beams 50A and 50B. [Diagram 2] 1 is a diagram illustrating a base station 10 and a wireless communication device 100 according to an embodiment. [Diagram 3] FIG. 13 is a diagram showing an array antenna 110D of a beam output device 100D. [Figure 4] FIG. 1 is a diagram illustrating Chebyshev weighting. [Diagram 5] FIG. 1 illustrates a beam output device 100D. [Figure 6]FIG. 13 is a diagram for explaining the range reached by the main lobe of the beam output from array antenna 110D. [Figure 7] FIG. 13 is a diagram showing data associating beam ID, distance, and main lobe power constraints. [Figure 8] 13A and 13B are diagrams illustrating the radiation pattern and phase difference in the array antenna 110D. [Figure 9] FIG. 2 is a diagram showing a configuration of a control device 100C. [Figure 10] 13 is a flowchart showing a process executed by a control device 100C. [Figure 11] FIG. 1 is a diagram showing a beam distribution. [Figure 12] FIG. 4 is a diagram showing the output and phase of each antenna element. [Figure 13] FIG. 13 is a diagram showing the frequency distribution of SIR. [Figure 14] 13 is a flowchart showing a process executed by a control device 100C according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a wireless communication device and a beam control method according to an embodiment of the present invention will be described.

[0010] <Embodiment> FIG. 1 is a diagram showing two beams 50A and 50B. The beams 50A and 50B will be described as being output from one array antenna in which a plurality of antenna elements are arranged in an array. Here, the beam 50A is shown by a solid line, and the beam 50B is shown by a dashed line. Also, in FIG. 1, for ease of understanding, the magnitude of SIR (Signal to Interference Ratio) is shown by the length of the double-headed arrow. Also, the terminals 30A and 30B are smartphones, etc.

[0011] Beam 50A has one main lobe 51A and multiple side lobes 52A, and beam 50B has one main lobe 51B and multiple side lobes 52B. Main lobe 51A is output from the array antenna toward terminal 30A, and main lobe 51B is output from the array antenna toward terminal 30B.

[0012] A phase shifter and an amplifier that adjust the phase and gain of the signal output from each antenna element are connected to each antenna element, and the output and angle (radiation direction) of beams 50A and 50B can be controlled by weighting the phase and / or gain. In addition, the output of a specific one or more side lobes among multiple side lobes 52A and 52B can be suppressed (reduced) by adjusting the weighting.

[0013] For comparison, FIG. 1(A) shows a state in which the output of side lobes 52A, 52B is not suppressed, and FIG. 1(B) shows a state in which the output of a specific one of side lobes 52A, 52B is suppressed.

[0014] In FIG. 1A, the main lobe 51A of the beam 50A and the side lobe 52B of the beam 50B overlap, and the output of the side lobe 52B is somewhat large. Similarly, the main lobe 51B of the beam 50B and the side lobe 52A of the beam 50A overlap, and the output of the side lobe 52A is somewhat large. In this state, the interference between the main lobe 51A and the side lobe 52B is large, and the SIR between the main lobe 51A and the side lobe 52B is small. Similarly, the interference between the main lobe 51B and the side lobe 52A is large, and the SIR between the main lobe 51B of the beam 50B and the side lobe 52A of the beam 50A is small. If the SIR is small, the throughput in communication decreases, and the communication state is not good.

[0015] 1B, the output of one side lobe 52A, 52B overlapping with main lobe 51A, 51B is reduced as shown by the dashed-dotted circle compared to FIG. 1A, so that the interference between main lobe 51A and side lobe 52B is small and the SIR between main lobe 51A and side lobe 52B is large. Similarly, the interference between main lobe 51B and side lobe 52A is small and the SIR between main lobe 51B and side lobe 52A is large. A large SIR improves communication throughput, and therefore the communication state is good.

[0016] As shown in FIG. 1(B), the output of side lobes 52A, 52B overlapping with main lobes 51A, 51B can be reduced by adjusting the weighting applied to the gain when amplifying the signal by an amplifier, thereby individually adjusting the gain of the signal output by each antenna element.

[0017] 2 is a diagram showing a base station 10 and a wireless communication device 100 of an embodiment. The base station 10 is realized by a DU (Distributed Unit) and a CU (Central Unit), and has an ID output unit 11 and signal output units 12 and 13. The base station 10 also includes components other than the ID output unit 11 and the signal output units 12 and 13, but these will not be described here.

[0018] The ID output unit 11 outputs an ID (Identifier) ​​number to the decoder 100A of the RU 20. There are multiple types of ID numbers output by the ID output unit 11, and each ID number is assigned to information relating to the direction of a beam output from the array antenna of the beam output device 100D of the wireless communication device 100. The signal output unit 12 outputs a transmission signal to the beam output device 100D of the wireless communication device 100. The signal output unit 13 outputs a local signal to the beam output device 100D of the wireless communication device 100.

[0019] The wireless communication device 100 is a radio unit (RU). The wireless communication device 100 includes a decoder 100A, a memory 100B, a control device 100C, and a beam output device 100D. The decoder 100A decodes an ID number input from the ID output unit 11 to obtain an address, and transfers the address to the memory 100B. The memory 100B includes a memory controller, and reads out control data based on the address input from the decoder 100A, and transfers the control data to the control device 100C. The control data includes weight data used to weight the gain when amplifying a transmission signal in the beam output device 100D, and weight data used to weight the phase when shifting the phase of the transmission signal.

[0020] The control device 100C uses the weighting data for gain and the weighting data for phase input from the memory 100B to control the amplification and phase shift of the transmission signal input to the beam output device 100D. The control device 100C is realized by an IC (Integrated Circuit), for example.

[0021] The base station 10 and the RU 20 are, for example, devices for 5G (Fifth Generation) data communication. The beam output device 100D of the wireless communication device 100 can simultaneously output multiple beams such as the beams 50A and 50B shown in FIG. 1 by beamforming. The number of beams may be three or more. Any one of the three or more beams is an example of a first beam, and one of the three or more beams having a main lobe that interferes with the side lobe of the first beam is an example of a second beam.

[0022] 3 is a diagram showing an array antenna 110D of a beam output device 100D. In the following, the XYZ coordinate system is defined and explained. In addition, in the following, a planar view means an XY plane view, and for convenience of explanation, the -Z direction side is referred to as the lower side or bottom, and the +Z direction side is referred to as the upper side or top, but this does not represent a universal up-down relationship.

[0023] The array antenna 110D includes a substrate 111D, an antenna element 112D, and a ground layer 113D. The communication frequency of the array antenna 110D is, for example, the 3.7 GHz band, the 4.5 GHz band, or the 28 GHz band.

[0024] The substrate 111D is, for example, a wiring substrate conforming to the FR4 (Flame Retardant type 4) standard, and has an antenna element 112D provided on its upper surface and a ground layer 113D provided on its lower surface. The antenna elements 112D are arranged in an array on the upper surface of the substrate 111D, and, for example, 64 antenna elements 112D arranged in an 8×8 pattern are arranged at equal pitches in the X and Y directions. The arrangement of the antenna elements 112D can also be regarded as being in a matrix. The antenna element 112D is square in plan view, and the length of one side is set to approximately 1 / 2 the electrical length of the wavelength at the communication frequency. The substrate 111D on whose upper surface the antenna elements 112D are arranged has a ground layer 113D on its lower surface, and all the antenna elements 112D and the ground layer 113D overlap in plan view, so that the antenna elements 112D and the ground layer 113D form a patch antenna.

[0025] Power is fed to each of the antenna elements 112D via through holes and wiring on the substrate 111D. The gain and phase of the radio waves radiated from the multiple antenna elements 112D are adjusted to form one beam.

[0026] It should be noted that the array antenna 110D is not limited to the configuration shown in Fig. 3, and may have a configuration different from that shown in Fig. 3 as long as a plurality of antenna elements 112D are arranged. The arrangement of the plurality of antenna elements 112D may be in a straight line rather than in an array.

[0027] Next, side lobe reduction by Chebyshev weighting will be explained using Fig. 4. Fig. 4 is a diagram for explaining Chebyshev weighting. For ease of explanation, eight antenna elements are arranged in a straight line as shown in Fig. 4(A), and antenna element numbers 1 to 8 are assigned from left to right. Eight variable amplifiers are respectively connected to the eight antenna elements, so that weighting can be applied to the gain when amplifying the power radiated from the eight antenna elements.

[0028] In Figure 4(B), the horizontal axis shows the antenna element number, and the vertical axis shows the weighted gain. The gains given to the power radiated from the eight antenna elements are weighted in stages so that the gain given to the power radiated from antenna elements 1 and 8 is the smallest, and the gain given to the power radiated from antenna elements 4 and 5, located in the center, is the largest. This type of weighting is Chebyshev weighting, and the difference in weight between adjacent antenna elements is small.

[0029] In Fig. 4(C), the dashed lines show the main lobe and side lobe output (radiated power) when power is radiated from the eight antenna elements in Fig. 4(A) without weighting, and the solid lines show the main lobe and side lobe output (radiated power) when power is radiated from the eight antenna elements in Fig. 4(A) with weighting as described above. In both the cases where weighting is not performed and where weighting is performed, the single waveform located in the center with the largest output represents the main lobe output, and the three waveforms on each side of the main lobe represent the side lobe output.

[0030] When the weighting is decreased from the center to the edge, as shown by the solid line in Figure 4(C), the output of the main lobe in the center is almost the same as the main lobe shown by the dashed line without weighting, but the output of the side lobes is reduced. In this way, by using Chebyshev weighting, it is possible to selectively reduce the output of the side lobes while maintaining the output of the main lobe.

[0031] Fig. 5 is a diagram showing a beam output device 100D. The beam output device 100D includes a signal terminal 101D, an array antenna 110D, a phase shifter 120D, an amplifier 130D, a mixer 140D, and a PA (Power Amplifier) ​​150D. The signal terminal 101D is connected to the signal output unit 12 shown in Fig. 2, and is an input terminal to which a transmission signal is input.

[0032] Fig. 5 shows antenna elements 112D of the array antenna 110D. There are 64 antenna elements 112D as shown in Fig. 3, and Fig. 5 shows the configuration of four of them.

[0033] As an example, four phase shifters 120D, four amplifiers 130D, four mixers 140D, and four PAs 150D are connected to the four antenna elements 112D. Since the beam output device 100D includes 64 antenna elements 112D, the beam output device 100D includes 64 phase shifters 120D, 64 amplifiers 130D, 64 mixers 140D, and 64 PAs 150D.

[0034] The phase shifter 120D has an input terminal 121D, an output terminal 122D, and a control terminal 123D. The output terminal 122D is connected to an input terminal 131D of the amplifier 130D. The control terminal 123D is connected to the control device 100C (see FIG. 2), and receives phase weighting data as input. The phase shifter 120D shifts the phase of the transmission signal input to the input terminal 121D in accordance with the phase weighting data input to the control terminal 123D, and outputs the shifted signal from the output terminal 122D.

[0035] The amplifier 130D has an input terminal 131D connected to the output terminal 122D, an output terminal 132D, and a control terminal 133D connected to the control device 100C (see FIG. 2). A phase-adjusted transmission signal is input from the output terminal 122D to the input terminal 131D, an input terminal 141D of the mixer 140D is connected to the output terminal 132D, and a weight for weighting the gain is input from the control device 100C to the control terminal 133D.

[0036] The gain of amplifier 130D is variably controlled according to a weight that is assigned to the gain when amplifying a transmission signal, and the transmission signal input to input terminal 131D is amplified and output from output terminal 132D. The weight is controlled by control device 100C. The weight is included in weight data for gain input from memory 100B to control device 100C. The gain of amplifier 130D weighted by the weight can be controlled in 1 dB steps (gain change width) in the range of -20 dB to 0 dB, for example.

[0037] The mixer 140D has input terminals 141D and 142D and an output terminal 143D. The input terminal 141D is connected to the output terminal 132D of the amplifier 130D, and receives the transmission signal amplified by the amplifier 130D. The input terminal 142D is connected to the signal output unit 13 of the base station 10, and receives the local signal. The output terminal 143D is connected to the input terminal 151D of the PA 150D. The mixer 140D multiplies the transmission signal input to the input terminal 141D by the local signal input to the input terminal 142D, and outputs the result from the output terminal 143D.

[0038] The PA 150D is a power amplifier having an input terminal 151D and an output terminal 152D. The input terminal 151D is connected to an output terminal 143D of the mixer 140D, and the output terminal 152D is connected to the antenna element 112D. The PA 150D amplifies the signal input from the mixer 140D and outputs the amplified signal to the antenna element 112D. The amplification factor of the PA 150D is a constant value.

[0039] The beam output device 100D as described above outputs a plurality of beams from the array antenna 110D, for example. Each beam has a main lobe and a side lobe, and also has a unique beam ID, so it is necessary to suppress interference between the main lobe and the side lobes of other beams. In order to suppress interference between beams in this way, it is necessary to adjust the gain of the signal radiated from each antenna element 112D. The gain of the signal radiated from each antenna element 112D is adjusted by the amplifier 130D.

[0040] 6 is a diagram for explaining the range reached by the main lobe of the beam output from the array antenna 110D. The range reached by the main lobe of the beam is the range in which the terminals 30A and 30B shown in FIG. 1 can receive power equal to or greater than a predetermined power level for data communication.

[0041] Here, as an example, it is assumed that array antenna 110D outputs four beams. The four beams are assigned beam IDs (Identifiers) 0 to I3. As an example, array antenna 110D is located at a height of 10 m above the ground.

[0042] The ranges reached by the main lobes of the four beams are different from one another. The beam with beam ID0 reaches within a range of distance r0 from the array antenna 110D, the beam with beam ID1 reaches within a range of distances r0 to r1 from the array antenna 110D, the beam with beam ID2 reaches within a range of distances r1 to r2 from the array antenna 110D, and the beam with beam ID3 reaches within a range of distances r2 to r3 from the array antenna 110D. Also, the distance r3 is determined by the maximum power P that the beam output by the array antenna 110D through beamforming can output. A This is the maximum distance that the beam can reach.

[0043] 7 is a diagram showing data associating beam IDs, distances, and constraints on the power of the main lobe. The distances are the longest distances that each beam can reach. The constraints on the power of the main lobe are the maximum power P A The beam output of each beam ID is expressed using

[0044] As shown in FIG. 7, the distance for beam ID0 is r0, and the constraint is the ratio of the square of r0 to the square of r3 as the maximum power P A The distance for beam ID1 is r1, and the constraint is that the ratio of the square of r1 to the square of r3 is the maximum power PA The distance for beam ID2 is r2, and the constraint is that the ratio of the square of r2 to the square of r3 is the maximum power P A The distance for beam ID3 is r3, and the constraint is the maximum power P A Although the constraint condition is expressed by the ratio of the squares of the distances in the following description, the constraint condition may be expressed by the ratio of the cubes of the distances.

[0045] Fig. 8 is a diagram for explaining the radiation pattern and phase difference in the array antenna 110D. Fig. 8 shows eight of the 64 antenna elements 112 shown in Fig. 3 as an example. The eight antenna elements 112 shown in Fig. 8 are included in one of eight rows in the Y direction, and are eight antenna elements 112 arranged in the X direction. Fig. 8 also shows the phase shifter 120D and the amplifier 130D together, and will be described assuming that weighting coefficients w0 to w7 of weighting data are input to each of them.

[0046] As shown in antenna element 112 at the end on the -X direction side, the radiation pattern of the power output (radiated) by antenna element 112 is denoted as g(θ). As shown in antenna element 112 that is the second antenna element from the end on the +X direction side, angle θ is the angle with respect to a line parallel to the Z axis that passes through the center of antenna element 112 in a plan view (a normal line that passes through the center of antenna element 112).

[0047] Furthermore, if the distance in the X direction between adjacent antenna elements 112 in the X direction is d (mm), the phase difference between the radio waves radiated in the direction of angle θ by adjacent antenna elements 112 in the X direction is 2π(d / λ) sin θ, where λ is the wavelength in free space of the radio waves output by each antenna element 112.

[0048] Next, a method for generating weight data of phase and gain that the control device 100C assigns to the beam output by the array antenna 110D will be described. Here, a form in which the array antenna 110D outputs three beams will be described. The first beam of the three beams is beam 50A shown in FIG. 1, which is an example of the first beam. The second and third beams have a main lobe that interferes with at least one of the multiple side lobes 52A of beam 50A, like beam 50B shown in FIG. 1. Here, the three beams will be described by distinguishing them as the first (#1), second (#2), and third (#3) beams.

[0049] Here, the weighting data representing the phase and gain input to the phase shifters 120D and amplifiers 130D corresponding to the 64 antenna elements 112 is represented by a weighting vector w. The weighting vector w is represented by the following equation (1), and has 64 weighting coefficients w0 to w N-1 N is an integer equal to or greater than 2 and represents the number of antenna elements 112, and is 64 in this example.

number

[0050] Moreover, let A be a matrix representing the output power of the main lobe of the first beam (#1). Matrix A is an example of a first matrix. Let B be a matrix representing the output power of a side lobe that interferes with the main lobes of the second (#2) and third (#3) beams, among the multiple side lobes of the first beam (#1). Matrix B is an example of a second matrix.

[0051] The power of the main lobe of the first (#1) beam, P S can be expressed by the following formula (2). In formula (2), N represents the number of pairs of phase shifters 120D and amplifiers 130D. When there are 64 phase shifters 120D and 64 amplifiers 130D, N is 64. n represents the number of pairs of phase shifters 120D and amplifiers 130D. n represents a number from 0 to N-1, and the total number is N.

number

[0052] Among the multiple side lobes of the first beam (#1), the power P of the side lobe that interferes with the main lobe of the second beam (#2) and the third beam (#3) I can be expressed by the following equation (3).

number

[0053] Here, the vector w shown in bold H is the complex conjugate transpose of the weight vector w. Also, as shown in the following equation (4), the weight coefficients w0 to w N-1 The sum of squares of is the constant C. Equation (4) is a constraint on the weight vector w. Weight coefficients w0 to w N-1 The sum of squares of the weight vector w and the vector w H It is obtained by multiplying the weighting coefficients w0 to w N-1 Since the sum of the squares of is equal to the total power radiated in all directions, in order to make the power radiated in all directions constant, the weighting coefficients w0 to w N-1 The sum of squares of is set to a constant C.

number

[0054] Here, the eigenvector corresponding to the maximum eigenvalue of matrix A is the weight vector w A Then, the maximum power P A is expressed by the following equation (5).

number

[0055] Furthermore, if the weight vector w is the eigenvector corresponding to the maximum eigenvalue of the matrix (A-βB) obtained by subtracting the matrix βB obtained by multiplying the matrix B by the reduction rate β from the matrix A, then for the first beam (#1) having a side lobe that interferes with the main lobes of the second (#2) and third (#3) beams, SIRmax, which represents the ratio of the output power of the main lobe to the output power of the side lobe that interferes with the main lobes of the second (#2) and third (#3) beams, is expressed by the following equation (6).

number

[0056] Using Lagrange's undetermined coefficient method, the weight vector w is calculated as shown in the following equation (7). β is the reduction ratio for reducing the output power B of the side lobe of the first beam (#1) that interferes with the main lobe of the second (#2) and third (#3) beams.

number

[0057] Using equation (7) as an evaluation function, by partially differentiating equation (7) with respect to the weight vector w, we obtain the following equation (8).

number

[0058] From equation (8), ξ is the maximum eigenvalue of the matrix (A-βB) obtained by multiplying matrix B by the reduction rate β from matrix A, and the eigenvector corresponding to the maximum eigenvalue ξ is the weight vector w. Therefore, the following equation (9) is a constraint condition for the weight vector w. The weight vector w, which is the eigenvector corresponding to the maximum eigenvalue ξ of the matrix (A-βB) obtained by equation (9), is the weight vector ultimately to be obtained by the wireless communication device 100 and beam control method of the embodiment.

number

[0059] 9 is a diagram showing the configuration of the control device 100C. The control device 100C includes a main control unit 111C, a condition derivation unit 112C, a weight vector generation unit 113C, a weight vector assignment unit 114C, a reduction rate derivation unit 115C, an allowable rate derivation unit 116C, an SIR derivation unit 117C, a judgment unit 118C, an SIR update unit 119C, a weight extraction unit 120C, and a memory 121C. The control device 100C is realized by a computer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), an input / output interface, an internal bus, and the like.

[0060] The main control unit 111C, the condition derivation unit 112C, the weight vector generation unit 113C, the weight vector assignment unit 114C, the reduction rate derivation unit 115C, the allowable rate derivation unit 116C, the SIR derivation unit 117C, the judgment unit 118C, the SIR update unit 119C, and the weight extraction unit 120C are functional blocks showing the functions of the programs executed by the control device 100C. Also, the memory 121C is a functional representation of the memory of the control device 100C.

[0061] The main control unit 111C is a processing unit that oversees the control processing of the control device 100C, and performs processing other than the processing performed by the condition derivation unit 112C, the weight vector generation unit 113C, the weight vector assignment unit 114C, the reduction rate derivation unit 115C, the allowable rate derivation unit 116C, the SIR derivation unit 117C, the judgment unit 118C, the SIR update unit 119C, and the weight extraction unit 120C.

[0062] The condition derivation unit 112C is an example of a maximum power calculation unit, and calculates the maximum power P A In addition, the condition derivation unit 112C calculates the maximum power P A Using the distance, the constraint condition for the beam of each beam ID is derived, and the data shown in FIG. 7 is created. AFor the above, a preset power value can be obtained from memory 121C, and for the distance, a distance associated with data indicating the radio wave receivable area that is pre-allocated to each beam ID can be obtained from memory 121C.

[0063] The weight vector generation unit 113C is an example of a weight vector derivation unit, and determines a weight vector w corresponding to the maximum eigenvalue of the matrix (A-βB) obtained by subtracting from matrix A representing the output power of main lobe 51A of beam 50A a matrix (βB) obtained by multiplying a reduction rate β that reduces the output power of side lobe 52B of beam 50A that interferes with main lobe 51B of beam 50B by matrix B representing the output power of side lobe 52A of beam 50A.

[0064] More specifically, weight vector generation unit 113C obtains an initial value of weight vector w corresponding to the maximum eigenvalue of a matrix (A-βB) obtained by subtracting from matrix A a matrix obtained by multiplying the initial value of reduction rate β by matrix B.

[0065] In addition, the weight vector generation unit 113C calculates a weight vector w corresponding to the maximum eigenvalue of the matrix (A-βB) obtained by subtracting the matrix obtained by multiplying the reduction ratio β, which has been increased by a predetermined ratio by the reduction ratio derivation unit 115C, by the matrix B from the matrix A representing the output power of the main lobe of the first (#1) beam. w The second process is performed to obtain

[0066] In addition, the weight vector generation unit 113C generates the weight vector w w The weight vector w before calculation is weight vector w c and stores it in the memory 121C.

[0067] The weighting vector assigning unit 114C outputs weighting data for phase to the phase shifter 120D (see FIG. 5) and outputs weighting data for gain to the amplifier 130D. In this way, the weighting vector assigning unit 114C assigns phase and gain weights to the beams 50A and 50B output from the array antenna 110D. The weighting vector assigning unit 114C outputs the weighting vector extracted by the weight extracting unit 120C. The weighting vector w is weighting data and represents the phase and gain.

[0068] The reduction percentage derivation unit 115C derives an initial value of the reduction percentage β and a reduction percentage β obtained by increasing the reduction percentage β by a predetermined percentage. The process of deriving the reduction percentage β obtained by increasing the reduction percentage β by a predetermined percentage is an example of a first process executed by the reduction percentage derivation unit 115C. The reduction percentage derivation unit 115C may repeatedly perform the process of increasing the reduction percentage β by a predetermined percentage in a flowchart described later.

[0069] The allowable ratio derivation unit 116C determines the maximum power P A When reducing the maximum power P, an allowable ratio α is derived, which represents the allowable ratio of reduction. A When the power P is reduced, the output of the side lobe is reduced, and the SIR tends to increase. Therefore, in the process of maximizing the SIR, the allowable ratio derivation unit 116C determines the maximum power P A The allowable rate α, which is the rate at which the reduction in the power output from the main lobe is allowed, is reduced. However, as the allowable rate α decreases, the output power of the main lobe decreases, and the receivable area of ​​the beam ID with a long radio wave radiation distance becomes smaller, so a lower limit is set. The allowable rate α is a value greater than 0 and less than 1.

[0070] The SIR derivation unit 117C uses the weight vector w generated by the weight vector generation unit 113C to calculate the initial value of the weight vector w and the complex conjugate transpose w of the initial value of the weight vector w in the matrix B based on the equation (6). H The initial value of the weight vector w and the complex conjugate transpose w of the initial value of the weight vector for the initial value of the side lobe output power of the first (#1) beam obtained by multiplying HThe power ratio of the initial value of the output power of the main lobe of the first (#1) beam obtained by multiplying and is calculated as the maximum SIRmax. SIR represents the power ratio between the signal power and the interference power.

[0071] The determination unit 118C determines the maximum power P A Power αP multiplied by the allowable rate α A In matrix A, we have weight vector w and the complex conjugate transpose of weight vector w. H The output power (w H Aw) is larger than the power αP A The output power (w H If it is determined that Aw) is larger, the following determination is further performed. w and the weight vector w w The complex conjugate transpose of w w H The weight vector w is added to the matrix A for the output power of the side lobe of the first beam (#1) obtained by multiplying w and the weight vector w w The complex conjugate transpose of w w H It is judged whether the SIR, which is the ratio of the output power of the main lobe of the first (#1) beam obtained by multiplying and is greater than the maximum SIRmax. Here, the weight vector w w is a weight vector obtained by using the reduction rate β after being increased by a predetermined rate by reduction rate derivation unit 115C.

[0072] The SIR update unit 119C adds the weight vector w w and the weight vector w w The complex conjugate transpose of w w H The weight vector w is added to the matrix A for the output power of the side lobe of the first beam (#1) obtained by multiplying w and the weight vector w w The complex conjugate transpose of w w HWhen it is determined that the SIR, which is the ratio of the output power of the main lobe of the first (#1) beam obtained by multiplying SIR by SIR, is greater than the maximum SIRmax, the maximum SIRmax is updated to the SIR determined to be greater.

[0073] The weight extraction unit 120C extracts the weight vector w w and the weight vector w w The complex conjugate transpose of w w H The weight vector w is added to the matrix A for the output power of the side lobe of the first beam (#1) obtained by multiplying w and the weight vector w w The complex conjugate transpose of w w H If it is determined that the SIR, which is the ratio of the output power of the main lobe of the first (#1) beam obtained by multiplying and is not greater than the maximum SIRmax, the weight vector w c The weight vector w extracted by the weight extraction unit 120C is c is the final weight vector.

[0074] The memory 121C stores the programs and data necessary for the above-mentioned processing.

[0075] 10 is a flowchart showing the process executed by the control device 100C. When the control device 100C starts the process, the condition derivation unit 112C calculates the maximum power P A is calculated (step S1).

[0076] The reduction rate derivation unit 115C derives an initial value of the reduction rate β (step S2). The initial value of the reduction rate β may be stored in the memory 121C and read out by the reduction rate derivation unit 115C. The initial value of the reduction rate β may be an appropriate value that is previously obtained by, for example, an experiment.

[0077] The weight vector generation unit 113C determines a weight vector w corresponding to the maximum eigenvalue of matrix A-βB obtained by subtracting a matrix (βB) obtained by multiplying the initial value of reduction rate β by matrix B representing the output power of side lobe 52A of beam 50A from matrix A representing the output power of main lobe 51A of beam 50A (step S3).

[0078] The SIR derivation unit 117C uses the weight vector w generated by the weight vector generation unit 113C in step S3 to calculate the initial value of the weight vector w and the complex conjugate transpose w of the initial value of the weight vector w in the matrix B based on the equation (6). H The initial value of the weight vector w and the complex conjugate transpose w of the initial value of the weight vector for the initial value of the side lobe output power of the first (#1) beam obtained by multiplying H The power ratio of the initial value of the output power of the main lobe of the first beam (#1) obtained by multiplying these values ​​is calculated as the maximum SIRmax (step S4).

[0079] The reduction rate derivation unit 115C derives a reduction rate β by increasing the reduction rate β by a predetermined rate (step S5). The process of step S5 is a first process performed by the reduction rate derivation unit 115C. The increase in the predetermined rate may be performed, for example, by adding a predetermined value to the reduction rate β, or by multiplying the reduction rate β by a constant.

[0080] The weight vector generation unit 113C converts the weight vector w at this time into a weight vector w c In other words, the weight vector generation unit 113C stores the weight vector w w The weight vector w before calculation is weight vector w c and stores it in the memory 121C.

[0081] The weight vector generation unit 113C calculates a weight vector w corresponding to the maximum eigenvalue of the matrix (A-βB) obtained by subtracting the matrix obtained by multiplying the reduction ratio β, which has been increased by a predetermined ratio by the reduction ratio derivation unit 115C, by the matrix B from the matrix A representing the output power of the main lobe of the first (#1) beam. w(Step S7) The process of step S7 is a second process executed by weight vector generation section 113C.

[0082] In step S8, the determination unit 118C performs the following two determinations (step S8). A Power αP multiplied by the allowable rate α A than matrix A with weight vector w w and the weight vector w w The complex conjugate transpose of w w H The output power (w w H Aw w ) is greater than the power αP A The output power (w w H Aw w ) is larger, the second step is to add weight vector w w and the weight vector w w The complex conjugate transpose of w w H The weight vector w is added to the matrix A for the output power of the side lobe of the first beam (#1) obtained by multiplying w and the weight vector w w The complex conjugate transpose of w w H It is determined whether the SIR, which is the power ratio of the output power of the main lobe of the first (#1) beam obtained by multiplying and, is greater than the maximum SIRmax.

[0083] If the determination unit 118C determines that the two determinations in step S8 are satisfied (S8: YES), the SIR update unit 119C updates the maximum SIRmax to that power ratio (step S9). After completing the process of step S9, the flow returns to step S5.

[0084] Also, the process proceeds from step S5 to step S8, and the determination unit 118C determines whether the power α A Output power ww H Aw w is larger but is not larger than the maximum SIRmax (S8: NO), the weight extraction unit 120C extracts the weight vector w c is extracted as the final weight vector (step S10). Although it is possible that the process of steps S5 to S8 is performed once each and the result of the determination in step S8 is NO, the process of steps S5 to S8 is repeated and the maximum SIRmax value is updated in step S9, so that the final weight vector w c is optimized. That is, the weight vector w c The optimal value of is found.

[0085] In step S8, the determination unit 118C determines the power αP A Output power w w H Aw w is larger, the weight extraction unit 120C still uses the weight vector w stored in the memory 121C c is extracted as the final weight vector (step S10). A <w w H Aw w ) does not hold true, it means that the main lobe is too small. In that case, the weight vector w c The optimized weight vector w c Increasing the reduction rate β increases the effect of suppressing interference, so the SIR increases and the main lobe tends to become smaller. A <w w H Aw w ) does not hold, it means that the reduction rate β has been set too large, and the weight vector w c becomes the optimal value.

[0086] FIG. 11 is a diagram showing beam distribution. Here, a simulation result when beamforming is performed by arranging 16 antenna elements 112 in a straight line will be described. In FIG. 11, the horizontal axis indicates direction, and the vertical axis indicates relative power (dB). In addition to the solid line of the embodiment, the characteristics of maximum signal and maximum SIR are shown. The maximum signal is the distribution of a beam obtained when the reduction rate β is set to zero (β=0), and the maximum SIR is the distribution of a beam when the output of the beam is reduced to obtain the maximum SIR. The distribution of the beam of the embodiment is the distribution of a beam obtained when the reduction rate β is optimized while the allowable rate α is made as large as possible according to the flowchart shown in FIG. 10. Note that the dashed lines indicating 0 dB from -90 degrees (deg.) to -40 degrees, -70 dB from -40 degrees to -30 degrees, 0 dB from -30 degrees to -20 degrees, 30 dB from -20 degrees to -5 degrees, 0 dB from -5 degrees to 0 degrees, -70 dB from 0 degrees to 40 degrees, and 0 dB from 40 degrees to 90 degrees represent the areas where unwanted side lobe radiation is suppressed (-40 degrees to -30 degrees and 0 degrees to 40 degrees) and the main lobe area (-20 degrees to -5 degrees).

[0087] In the embodiment shown in Figure 11, in both the beam distributions with maximum signal and maximum SIR, the main lobe exists in the direction range from approximately -20 [deg.] to approximately 0 [deg.], and multiple side lobes exist in other directions.

[0088] As shown in Fig. 11, the relative power of the main lobe in the embodiment is slightly lower than that of the main lobe with the maximum signal, but is almost the same level, about 20 dB. The relative power of the main lobe with the maximum SIR is significantly lower than that of the main lobe in the embodiment and that of the main lobe with the maximum signal, about 2 dB.

[0089] Furthermore, the relative power of the side lobe in the embodiment was significantly lower than the maximum signal side lobe relative power (approximately -10 to 0 dB), being approximately -20 dB to approximately -15 dB. The maximum SIR side lobe relative power was approximately -63 to approximately -55 dB, but the relative power of the side lobe in the embodiment was at a sufficiently low level.

[0090] Fig. 12 is a diagram showing the output and phase of each antenna element. Fig. 12(A) shows the output amplitude (dB), and Fig. 12(B) shows the output phase [deg.]. Here, as in Fig. 11, a simulation result will be described for the case where beamforming is performed with 16 antenna elements 112 arranged in a straight line. The element numbers of the antenna elements 112 are numbered 0 to 15 from the end.

[0091] 12(A), it was found that when the SIR is maximum, the outputs of the 16 antenna elements 112 located at both ends with element numbers 0 to 4 or 11 to 15 are extremely lower than the outputs of the central antenna elements 112 with element numbers 5 to 10. It was also found that the outputs of the 16 antenna elements 112 in the embodiment show a similar tendency to the outputs when the signal is maximum, and the outputs of the antenna elements 112 located at both ends with element numbers 0 to 4 or 11 to 15 are lower, but the decrease is not as extreme as when the SIR is maximum.

[0092] Also, as shown in FIG. 12(B), the phase of the output of the 16 antenna elements 112 in the embodiment showed the same tendency as the output when the signal was maximum, and changed periodically. Also, when the SIR was maximum, the phase changed significantly between adjacent antenna elements 112. From the results of FIG. 12(A) and FIG. 12(B), it was found that in the embodiment, the output in the direction of the side lobe where the output is to be reduced is reduced. In order to increase the main lobe in the embodiment, the amplitude and phase are adjusted so as to reduce the output of the side lobe where the output is to be reduced, under the constraint condition of maintaining the phase similar to that in the case of the signal maximum. On the other hand, when the SIR is maximum, the amplitude and phase are adjusted so as to reduce the side lobe where the output is to be reduced, without the constraint condition of the phase that increases the main lobe. For this reason, the result shown in FIG. 12(B) was obtained.

[0093] Fig. 13 is a diagram showing the frequency distribution of SIR. The frequency distribution of SIR shown in Fig. 13 was obtained when the base station was communicating with four terminals at the same time. The frequency distribution represents the number of times the SIR is the same. Since SIR is related to throughput, if the SIR is large, the throughput is high, and for example, in the case of 5G, communication is possible at 1 Gbps. If the SIR is small, the throughput is low, and communication is only possible at a few Mbps, for example.

[0094] In Fig. 13, a simulation result in the case where beamforming is performed by arranging eight antenna elements 112 in a straight line will be described. In Fig. 13, the SIR obtained in the case of the embodiment, the SIR obtained by Chebyshev weighting, and the SIR in the case where no weighting is performed (no weighting) are compared.

[0095] In the case of the embodiment, it was found that the SIR value was larger overall than in the Chebyshev and non-weighted cases, which shows that the interference between the side lobe of one beam and the main lobe of another beam is reduced.

[0096] As described above, the weight vector w corresponding to the maximum eigenvalue of the matrix A-βB is obtained, SIRmax is derived using the weight vector w, and the value of the reduction ratio β is determined so that SIRmax is maximized. By using this method, the reduction ratio β that maximizes SIRmax obtained from the matrix A-βB is obtained, and the weight vector w that maximizes SIRmax is obtained. c It is possible to reliably find the optimum value of

[0097] Therefore, it is possible to provide radio communication device 100 that can reliably find the optimum weighting value for reducing the output of a side lobe in a specific direction.

[0098] In addition, a permissible ratio α is set, and the power αP A The output power (w w H Aw w) is larger, SIRmax is updated, so that weighting that reduces the power of the main lobe and side lobe, as in the case of the SIR maximum shown in Figures 11 and 12, can be avoided, and high output power of the main lobe can be obtained.

[0099] In the above, the beam output device 100D includes 64 antenna elements 112D arranged in an 8 x 8 pattern, but the number and arrangement of the antenna elements 112D are not limited to this. As described in Fig. 11 and Fig. 12, a configuration in which a plurality of antenna elements 112 are arranged in a straight line may also be used.

[0100] In addition, as shown in equation (4), the weighting coefficients w0 to w N-1 As explained above, the sum of squares of the weight coefficients w0 to w N-1 Each of the weighting coefficients w0 to w1 may be set to be equal to or smaller than the constant C. When the same amplifier 130D is connected to each antenna element 112, the maximum power that can be transmitted by each antenna element 112 is constant. N-1 To set each of these to a certain value or less, equation (10) should be followed.

number

[0101] Fig. 14 is a flowchart showing the process executed by the control device 100C of the modified embodiment. The flow shown in Fig. 14 is obtained by inserting steps S10A and S10B between steps S8 and S10 of the flow shown in Fig. 10. Here, the differences will be described.

[0102] In step S8, the determination unit 118C determines whether the power α A Output power w w H Aw wis larger, but if it is determined that the power ratio is not larger than the maximum SIRmax (S8: NO), it is determined whether the maximum SIRmax is smaller than a predetermined SIR0 (step S10A). The predetermined SIR0 is a lower limit value required for SIR. That is, such step S10A is provided when it is required to guarantee that the SIR is equal to or larger than the predetermined SIR0, which is the lower limit value.

[0103] When the determination unit 118C determines that the maximum SIRmax is smaller than the predetermined SIR0 (S10A: YES), the allowable ratio derivation unit 116C decreases the allowable ratio α by a predetermined value (step S10B). After completing the process of step S10B, the flow returns to step S5.

[0104] After steps S5 to S8, if the determination unit 118C determines in step S10A that the maximum SIRmax is not smaller than the predetermined SIR0 (S10A: NO), the weight extraction unit 120C extracts the weight vector w c is extracted as the final weight vector (step S10C). The process of step S10C is the same as the process of step S10 in FIG.

[0105] According to the flow shown in FIG. 14, it is possible to ensure that the SIR is equal to or greater than the lower limit SIR0.

[0106] The above describes an exemplary embodiment of a wireless communication device and a beam control method of the present invention. However, the present invention is not limited to the specifically disclosed embodiment, and various modifications and changes are possible without departing from the scope of the claims. Regarding the above embodiment, the following supplementary notes are further disclosed. (Appendix 1) a plurality of antenna elements for outputting a first beam and a second beam based on a weight vector representing weighting for gain and / or phase; a weight vector derivation unit that determines a weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting, from a first matrix that represents an output power of a main lobe of the first beam, a matrix that is obtained by multiplying a reduction rate for reducing the output power of a side lobe of the first beam that interferes with the main lobe of the second beam by a second matrix that represents the output power of the side lobe of the first beam; a determination unit that determines whether a power ratio of an output power of a main lobe of the first beam, obtained by multiplying the first matrix by the weight vector and the complex conjugate transpose of the weight vector, to an output power of a side lobe of the first beam, obtained by multiplying the second matrix by the weight vector and the complex conjugate transpose of the weight vector, is greater than a maximum SIRmax; a weight extraction unit that extracts the weight vector when the determination unit determines that the power ratio is not greater than the maximum SIRmax; 23. A wireless communication device comprising: (Appendix 2) the weight vector derivation unit determines an initial value of a weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting from the first matrix a matrix obtained by multiplying the initial value of the reduction rate by the second matrix; an SIR derivation unit that derives as the maximum SIRmax a power ratio of an initial value of an output power of a main lobe of the first beam, which is obtained by multiplying the first matrix by the initial value of the weight vector and the complex conjugate transpose of the initial value of the weight vector, to an initial value of an output power of a side lobe of the first beam, which is obtained by multiplying the second matrix by the initial value of the weight vector and the complex conjugate transpose of the initial value of the weight vector; a reduction rate derivation unit that performs a first process to derive a reduction rate obtained by increasing the reduction rate by a predetermined rate; Further comprising: the weight vector derivation unit performs a second process of obtaining a weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting from a first matrix representing an output power of a main lobe of the first beam a matrix obtained by multiplying the reduction rate, which has been increased by the predetermined rate by the reduction rate derivation unit, by the second matrix; The wireless communication device described in Appendix 1, wherein the determination unit performs a third process of determining whether a power ratio of the output power of the main lobe of the first beam obtained by multiplying the first matrix with the weight vector obtained using a reduction rate increased by the specified rate and the complex conjugate transpose of the weight vector to the output power of the side lobe of the first beam obtained by multiplying the second matrix with the weight vector obtained using a reduction rate increased by the specified rate and the complex conjugate transpose of the weight vector is greater than the maximum SIRmax. (Appendix 3) an update unit that updates the maximum SIRmax to the power ratio when the determination unit determines that the power ratio is greater than the maximum SIRmax; When the maximum SIRmax is updated to the power ratio by the update unit, the reduction rate derivation unit the first processing by the weight vector derivation unit, and the third processing by the determination unit. (Appendix 4) a maximum power calculation unit that calculates a maximum power that the first beam can output under a predetermined condition; an allowable ratio derivation unit that derives an allowable ratio of a decrease in the output power of the main lobe of the first beam with respect to the maximum power; Further comprising: the determination unit determines whether an output power of a main lobe of the first beam obtained by multiplying the first matrix by the weight vector obtained by using a reduction rate increased by the predetermined rate and a complex conjugate transpose of the weight vector is greater than a power obtained by multiplying the maximum power by the allowable rate, and performs the third process; The wireless communication device described in Appendix 3, wherein the update unit updates the maximum SIRmax when the determination unit determines that the output power of the main lobe of the first beam obtained by multiplying the first matrix by the weight vector obtained using a reduction rate increased by the predetermined rate and the complex conjugate transpose of the weight vector is greater than the power obtained by multiplying the maximum power by the allowable rate, and when the third processing determines that the power ratio is greater than the maximum SIRmax. (Appendix 5) The wireless communication device described in Appendix 4, wherein the specified condition when the maximum power calculation unit calculates the maximum power is the maximum distance that the main lobe of the first beam can reach. (Appendix 6) The wireless communication device according to any one of claims 1 to 5, wherein the weight vector derivation unit determines the weight vector under a condition that a sum of squares of the weight vector is constant. (Appendix 7) The wireless communication device according to any one of claims 1 to 5, wherein the weight vector derivation unit determines the weight vector under a condition that each weight coefficient of the weight vector is equal to or smaller than a certain value. (Appendix 8) 1. A beam control method in a wireless communication device including a plurality of antenna elements that outputs a first beam and a second beam based on a weight vector representing weighting for gain and / or phase, comprising: determining a weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting a matrix obtained by multiplying a reduction ratio for reducing the output power of a side lobe of the first beam interfering with the main lobe of the second beam by a second matrix representing the output power of the side lobe of the first beam from a first matrix representing the output power of the main lobe of the first beam; determining whether a power ratio of an output power of a main lobe of the first beam obtained by multiplying the first matrix by the weight vector and the complex conjugate transpose of the weight vector to an output power of a side lobe of the first beam obtained by multiplying the second matrix by the weight vector and the complex conjugate transpose of the weight vector is greater than a maximum SIRmax; extracting the weight vector if it is determined that the power ratio is not greater than the maximum SIRmax; A beam control method, in which a computer executes processes including the steps of: [Explanation of symbols]

[0107] 10 base station 50A, 50B Beam 51A, 51B main lobe 52A, 52B Side lobes 100 Wireless communication device 100C Control Unit 111C Main control unit 112C Condition derivation part 113C Weight vector generation unit 114C Weight vector assignment unit 115C Reduction ratio derivation part 116C Tolerance ratio derivation part 117C SIR derivation part 118C Judgment section 119C SIR update section 120C Weight extraction part 121C Memory 100D Beam Output Device 110D Array Antenna 112D Antenna Element 120D Phase Shifter 130D Amplifier

Claims

1. a plurality of antenna elements for outputting a first beam and a second beam based on a weight vector representing weighting for gain and / or phase; a weight vector derivation unit that determines a weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting from a first matrix representing an output power of a main lobe of the first beam a matrix obtained by multiplying a reduction rate for reducing the output power of a side lobe of the first beam interfering with the main lobe of the second beam by a second matrix representing the output power of the side lobe of the first beam, the weight vector derivation unit determining an initial value of a weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting from the first matrix a matrix obtained by multiplying an initial value of the reduction rate by the second matrix; an SIR derivation unit that derives a power ratio of an initial value of an output power of a main lobe of the first beam, which is obtained by multiplying the first matrix by an initial value of the weight vector and a complex conjugate transpose of the initial value of the weight vector, to an initial value of an output power of a side lobe of the first beam, which is obtained by multiplying the second matrix by an initial value of the weight vector and a complex conjugate transpose of the initial value of the weight vector, as a maximum SIRmax that is a maximum value of an SIR (Signal to Interference Ratio); a memory in which an initial value of the weight vector is stored by the weight vector derivation unit; a reduction rate derivation unit that performs a first process to derive a reduction rate that is a predetermined rate increase from the reduction rate; A determination unit that performs a third process; a weight extraction unit that extracts an initial value of the weight vector stored in the memory in a predetermined case; Including, the weight vector derivation unit performs a second process of obtaining a weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting from a first matrix representing an output power of a main lobe of the first beam a matrix obtained by multiplying the reduction rate, which has been increased by the predetermined rate by the reduction rate derivation unit, by the second matrix; the third process is a process of determining whether a power ratio of an output power of a side lobe of the first beam obtained by multiplying the weight vector obtained by using the reduction rate increased by the predetermined rate and a complex conjugate transpose of the weight vector by the second matrix to an output power of a main lobe of the first beam obtained by multiplying the weight vector obtained by using the reduction rate increased by the predetermined rate and a complex conjugate transpose of the weight vector by the first matrix is ​​greater than the maximum SIRmax, The weight extraction unit extracts an initial value of the weight vector stored in the memory when the determination unit determines that the power ratio is not greater than the maximum SIRmax.

2. an update unit that updates the maximum SIRmax to the power ratio when the determination unit determines that the power ratio is greater than the maximum SIRmax; 2. The wireless communication device according to claim 1, wherein when the maximum SIRmax is updated to the power ratio by the update unit, the first process by the reduction rate derivation unit, the second process by the weight vector derivation unit, and the third process by the determination unit are repeatedly executed.

3. a maximum power calculation unit that calculates a maximum power that the first beam can output under a predetermined condition; an allowable ratio derivation unit that derives an allowable ratio of a decrease in the output power of the main lobe of the first beam with respect to the maximum power; Further comprising: the determination unit determines whether an output power of a main lobe of the first beam obtained by multiplying the first matrix by the weight vector obtained by using a reduction rate increased by the predetermined rate and a complex conjugate transpose of the weight vector is greater than a power obtained by multiplying the maximum power by the allowable rate, and performs the third process; 3. The wireless communication device according to claim 2, wherein the update unit updates the maximum SIRmax when the determination unit determines that the output power of the main lobe of the first beam obtained by multiplying the first matrix by the weight vector obtained using a reduction rate increased by the predetermined rate and the complex conjugate transpose of the weight vector is greater than the power obtained by multiplying the maximum power by the allowable rate, and when the third processing determines that the power ratio is greater than the maximum SIRmax.

4. The wireless communication device according to claim 3 , wherein the predetermined condition when the maximum power calculation unit calculates the maximum power is a maximum distance that a main lobe of the first beam can reach.

5. The wireless communication device according to claim 1 , wherein the weight vector derivation unit determines the weight vector under a condition that a sum of squares of the weight vector is constant.

6. The wireless communication device according to claim 1 , wherein the weight vector derivation unit determines the weight vector under a condition that each weight coefficient of the weight vector is equal to or smaller than a certain value.

7. 1. A beam control method in a wireless communication device including a plurality of antenna elements that outputs a first beam and a second beam based on a weight vector representing weighting for gain and / or phase, comprising: determining a weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting from a first matrix representing an output power of a main lobe of the first beam a matrix obtained by multiplying a reduction rate for reducing the output power of a side lobe of the first beam interfering with the main lobe of the second beam by a second matrix representing the output power of the side lobe of the first beam, and determining an initial value of the weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting from the first matrix a matrix obtained by multiplying an initial value of the reduction rate by the second matrix; deriving a power ratio of an initial value of an output power of a main lobe of the first beam, which is obtained by multiplying the first matrix by the initial value of the weight vector and the complex conjugate transpose of the initial value of the weight vector, to an initial value of an output power of a side lobe of the first beam, which is obtained by multiplying the second matrix by the initial value of the weight vector and the complex conjugate transpose of the initial value of the weight vector, as a maximum SIRmax, which is a maximum value of SIR (Signal to Interference Ratio); storing an initial value of the weight vector in a memory; performing a first process of deriving a reduction rate by increasing the reduction rate by a predetermined rate; performing a third process; Extracting an initial value of the weight vector stored in the memory in a predetermined case; A computer executes a process including obtaining the weight vector includes performing a second process to obtain a weight vector corresponding to a maximum eigenvalue of a matrix obtained by subtracting from a first matrix representing an output power of a main lobe of the first beam a matrix obtained by multiplying the reduction rate, which has been increased by the predetermined rate by performing the first process, by the second matrix; the third process is a process of determining whether a power ratio of an output power of a side lobe of the first beam obtained by multiplying the weight vector obtained by using the reduction rate increased by the predetermined rate and a complex conjugate transpose of the weight vector by the second matrix to an output power of a main lobe of the first beam obtained by multiplying the weight vector obtained by using the reduction rate increased by the predetermined rate and a complex conjugate transpose of the weight vector by the first matrix is ​​greater than the maximum SIRmax, Extracting the initial value of the weight vector stored in the memory in a predetermined case includes extracting the initial value of the weight vector stored in the memory when it is determined that the power ratio is not greater than the maximum SIRmax. A beam control method, in which a computer executes processes including the steps of:

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