Receiving device and receiving method

Abstract

Receiving device (1, 2, 3) for receiving incoming waves, which are radio waves, arriving at a group antenna which contains several antenna elements (10_1, ..., 10_N), which receiving device (1, 2, 3) has: several radio receiving units (11_1, ..., 11_N) that generate several digital signals corresponding to multiple signals based on the multiple signals received via the multiple antenna elements (10_1, ..., 10_N); an estimation unit (20_1, ..., 10_N) for a first delay profile for electrical energy, which estimates several first delay profiles for electrical energy corresponding to the several digital signals on a basis of the several digital signals; a synthesis unit (16) that generates a synthesized delay profile for electrical energy by synthesizing the several first delay profiles for electrical energy; a group control unit (13) that changes the direction of a zero point of the group antenna; a group processing unit (12) that generates a group processing signal by performing group processing for the multiple digital signals by directing the zero point in the direction changed by the group control unit (13); an estimation unit (20_N+1) for a second delay profile, which estimates a second delay profile for electrical energy based on the group processing signal; a difference unit (17) that generates a difference delay profile for electrical energy, which is obtained by subtracting the second delay profile for electrical energy from the synthesized delay profile for electrical energy; a two-dimensional map unit (18) that forms a two-dimensional map showing a relationship between delay times and arrival angles of the incoming waves, based on the differential delay profile for electrical energy and the direction of the zero point, which was modified by the group control unit (13); and an arrival angle estimation unit (19) that outputs an arrival angle of a component with a shortest delay time and a largest electrical energy from the incoming waves on the two-dimensional map.

Description

TECHNICAL FIELD

[0001] The present invention relates to a receiving apparatus and a receiving method for receiving radio waves transmitted from a transmitter, and more particularly relates to a technology for identifying a direction in which the transmitter is located based on a received signal. STATE OF THE ART

[0002] A receiving device (receiver) for receiving radio waves from a mobile phone, wireless LAN (local area network), terrestrial digital broadcast, and so on receives not only a direct wave, which is an incoming wave arriving directly from a transmitter, but also a delayed wave, which is an incoming wave arriving after being reflected and scattered by an obstacle such as a building or structure. A communication environment in which the radio waves transmitted from the transmitter arrive at the receiver via various routes as described above is called a multipath environment.

[0003] Directional characteristic control of an array antenna including a plurality of antenna elements is known as one of the technologies for suppressing reception performance deterioration in a multipath environment. In the array antenna, a directivity can be given to the array antenna by controlling a plurality of weighting coefficients used when combining a plurality of signals received by the plurality of antenna elements. In a multipath environment, the deterioration of reception performance due to the influence of the delay wave can be suppressed by controlling the directivity of the array antenna such that a main lobe of the array antenna is directed in an arrival direction of the direct wave (the direction toward the transmitter). It is necessary to accurately estimate an arrival angle of the direct wave in order to improve reception performance by directivity control of the array antenna.

[0004] In a case where the receiver is fixed and the direction to the transmitter is already known, the directivity of the array antenna can be manually adjusted so that the main lobe of the array antenna is directed toward the transmitter. However, in a case where the radio waves are received by the receiver in a moving object such as an automobile, the direction to the transmitter changes as seen from the receiver, and thus, it is necessary to estimate the arrival angle of the direct wave from a received signal in which the direct wave and the delay wave are superimposed. The radio wave environment in radio communication is classified into LOS (line of sight), in which the transmitter exists within the field of view of the receiver, and NLOS (none line of sight), in which the transmitter exists outside the field of view of the receiver.The present application estimates the arrival angle of the direct wave assuming the LOS environment.

[0005] In general, a MUSIC (Multiple Signal Classification) method and an ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) method, which use an eigenvalue and an eigenvalue vector of a correlation matrix of a signal received by the array antenna including N (N is an integer equal to or greater than 2) antenna elements, are known as methods for measuring the arrival angle of the radio wave.

[0006] However, the number of incoming waves that can be measured by the MUSIC method or ESPRIT method is limited to N waves at most. In a case where the MUSIC method or ESPRIT method is used in a multipath environment where a large number of delay waves arrive at the receiver by being reflected by surrounding obstacles in addition to the direct wave arriving directly from the transmitter, the array antenna is required to include the antenna elements in the same number as the maximum number of assumed incoming waves (direct wave and delay waves), and there is a disadvantage that the array antenna becomes too large.

[0007] Patent Document 1 describes a method for estimating the arrival waves of three or more waves through two antenna elements. In this method, the waves arriving with different delay times are separated using complex delay profiles calculated from signals received by respective antenna elements, and the arrival angles of the incoming waves are estimated based on the phase difference between the antenna elements of each separated incoming wave.

[0008] Patent Document 2 and Patent Document 3 describe a method for estimating the angle of arrival using a beam of rays from an array antenna. This method can estimate the angle of arrival of incoming waves whose number is greater than the number of antenna elements. In this method, incoming waves with different arrival angles are first separated using multiple beamforms with different main lobe directions. Then, delay times are estimated based on delay profiles calculated from the results of each beamform. A rough angle of arrival can be estimated from the main lobe direction of the beamform with the largest electric energy.Furthermore, the arrival angle estimation accuracy can be further improved by performing an arrival angle estimation based on the electrical energy difference between the beamforms whose main lobe directions are adjacent. PRIOR ART DOCUMENTS PATENT DOCUMENTS PATENT DOCUMENT 1: Japanese Patent No. 4833144 (pages 14 - 15, Fig. 6) PATENT DOCUMENT 2: Japanese Patent Application Publication No. 2009-206889 (page 5, page 7, Fig. 2) PATENT DOCUMENT 3: Japanese Patent Application Publication No. 2003-8483 (page 6, page 7, Fig. 1) SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0009] When a vehicle, a building, or the like exists near the receiver, there is no large difference in the length of a radio wave propagation path from the transmitter to the receiver between the direct wave and the delay wave, and thus the delay time becomes very short. If this delay time becomes shorter than the delay time resolution of the complex delay profile estimated in Patent Document 1, the delay wave overlaps the direct wave in the estimated complex delay profile, and the two cannot be separated. As a result, the arrival angle is estimated for the signal in which the direct wave and the delay wave have been combined, and there is a problem that the estimation accuracy of the arrival angle of the direct wave deteriorates considerably.For example, the delay time resolution of the complex delay profile estimated by receiving a signal with a bandwidth of 10 MHz is approximately 100 ns, the inverse of the bandwidth. On the other hand, if an obstacle, such as a vehicle, exists at a position 3 m from the receiver on the opposite side of the transmitter, the delay time relative to the direct wave is τ = (3 / c) × 2 = 20 ns. Here, c is the speed of light and is 3 × 10. 8m / s. In this case, the delay time is 10 ns, compared to the delay time resolution of 100 ns of the estimated complex delay profile. The delay wave overlaps the direct wave in the estimated delay profile, making it appear as if a single incoming wave is received. In the technology described in Patent Document 1, the arrival angle is estimated for the signal in which the direct wave and the delay wave, between which the arrival angles differ by 180°, are combined, and the estimation accuracy of the arrival angle of the direct wave deteriorates.

[0010] Furthermore, in Patent Document 2 and Patent Document 3, when the number of antenna elements is large, the width of the main lobe can be narrowed, and thus the multiple incoming waves with different arrival angles can be separated by the beam. However, as the number of antenna elements decreases, the width of the main lobe becomes larger, and thus it becomes difficult to separate the multiple incoming waves with different arrival angles. Furthermore, the electrical energy difference between the beamforms whose main lobe directions are adjacent becomes smaller, thus causing a problem that the estimation accuracy of the arrival angle of the direct wave deteriorates.

[0011] Therefore, it is an object of the present invention to provide a receiving apparatus and a receiving method capable of accurately estimating the arrival angle of the direct wave by a small number of antenna elements in an environment in which the delay wave whose delay time is shorter than the resolution of a delay profile exists. MEANS TO SOLVE THE PROBLEM

[0012] A receiving device according to the present invention is a receiving device that receives incoming waves that are incoming radio waves at an array antenna including a plurality of antenna elements, the receiving device including: radio receiver units that generate a plurality of digital signals corresponding to a plurality of signals based on the plurality of signals received via the plurality of antenna elements; a first electric power delay profile estimation unit that estimates a plurality of first electric power delay profiles corresponding to the plurality of digital signals based on the plurality of digital signals; a synthesis unit that generates a composite electric power delay profile by synthesizing the plurality of first electric power delay profiles; an array control unit that changes a direction of a null point of the array antenna;a group processing unit that generates a group processing signal by performing a group process on the plurality of digital signals by directing the zero point in the direction changed by the group control unit; a second delay profile estimation unit that estimates a second electric energy delay profile from the group processing signal; a difference unit that generates an electric energy difference delay profile obtained by subtracting the second electric energy delay profile from the synthesized electric energy delay profile; a two-dimensional map unit that creates a two-dimensional map indicating a relationship between delay times and arrival angles of the incoming waves based on the electric energy difference delay profile and the direction of the zero point changed by the group control units;and an arrival angle estimation unit that outputs an arrival angle of a component with a shortest delay time and a largest electric energy from the incoming waves on the two-dimensional map.;

[0013] A receiving method according to the present invention is a receiving method for receiving incoming waves that are radio waves arriving at an array antenna including a plurality of antenna elements, the receiving method including: a receiving step of generating a plurality of digital signals corresponding to a plurality of signals based on the plurality of signals received via the plurality of antenna elements; a first estimation step of estimating a plurality of first electric power delay profiles corresponding to the plurality of digital signals based on the plurality of digital signals; a synthesis step of generating a synthesized electric power delay profile by synthesizing the plurality of first electric power delay profiles;an array processing step of changing a direction of a null point of the array antenna and generating an array processing signal by performing array processing on the plurality of digital signals by directing the null point in the changed direction; a second estimation step of estimating a second electric power delay profile from the array processing signal; a difference step of generating an electric power difference delay profile obtained by subtracting the second electric power delay profile from the synthesized electric power delay profile; a two-dimensional map step of creating a two-dimensional map indicating a relationship between delay times and arrival angles of the incoming waves based on the electric power difference delay profile and the changed direction of the null point;a step of changing the direction of the origin and performing the receiving step, the first estimation step, the synthesis step, the group processing step, the second estimation step, the difference step, and the two-dimensional map step; and an arrival angle estimation step of outputting an arrival angle of a component with a shortest delay time and a largest electric energy from the incoming waves on the two-dimensional map. EFFECTS OF THE INVENTION

[0014] According to the present invention, by calculating an electric power delay profile of the incoming wave arriving from a direction of a zero point while scanning the zero point of the array antenna, it is possible to separate the delay wave whose delay time is shorter than the resolution of the electric power delay profile and accurately estimate the arrival angle of the direct wave even if the number of antenna elements is small. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram schematically illustrating a configuration of a receiving apparatus according to a first embodiment of the present invention. Fig. 2 is a block diagram schematically illustrating a configuration of a delay profile estimation unit in an OFDM transmission method. Fig. 3 is a block diagram schematically illustrating a configuration of a delay profile estimation unit in a DSSS transmission method. Fig. 4(a) and Fig. 4(b) are diagrams illustrating an angle profile and a delay profile in a case where a delay time is long. Fig. 5 is a diagram illustrating situations of separating arrival angles in the case where a delay time is long. Fig. 6 is a diagram illustrating a two-dimensional map indicating a relationship between a delay time and an arrival angle in the case where a delay time is long. Fig. 7(a) and Fig. 7(b) are diagrams illustrating an angle profile and a delay profile in a case where a delay time is short. Fig. 8 is a diagram illustrating situations of separating arrival angles in the case where a delay time is short. Fig. 9 is a diagram illustrating a two-dimensional map indicating a relationship between a delay time and an arrival angle in the case where a delay time is short. Fig. 10 is a block diagram schematically illustrating a configuration of a receiving apparatus according to a second embodiment of the present invention. Fig. 11(a) and Fig. 11(b) are diagrams illustrating a two-dimensional map in the case where a delay time is long according to the second embodiment. Fig. 12(a) and Fig. 12(b) are diagrams illustrating a two-dimensional map showing a relationship between a delay time and an arrival angle in the case where a delay time is short according to the second embodiment. Fig. 13 is a block diagram schematically showing a configuration of a correction unit according to Fig. 10 illustrated. Fig. 14 is a block diagram schematically illustrating a configuration of a receiving apparatus according to a third embodiment of the present invention. Fig. 15 is a flowchart illustrating a receiving method according to a fourth embodiment of the present invention. Fig. 16 is a flowchart illustrating a delay profile estimation process in the OFDM transmission method. Fig. 17 is a flowchart illustrating a delay profile estimation process in the DSSS transmission method. Fig. 18 is a hardware configuration diagram illustrating a receiving device as a variant of the first to third embodiments. MODE FOR CARRYING OUT THE INVENTION <1> First Embodiment<1-1> Configuration of the first embodiment

[0015] Fig. Figure 1 is a block diagram schematically illustrating a configuration of a receiving device 1 according to a first embodiment of the present invention. The receiving device 1 receives a radio wave (incoming wave) emitted from a transmitter. As shown in Fig. 1, the receiving apparatus 1 according to the first embodiment includes N radio receiving units 11_1, ..., 11_N connected to N (N is an integer equal to or greater than 2) antenna elements 10_1, ..., 10_N constituting an array antenna, an array processing unit 12, an array control unit 13, (N+1) delay profile estimation units 14_1, ..., 14_N+1, (N+1) electric energy calculation units 15_1, ..., 15_N+1, a synthesis unit 16, a difference unit 17, a two-dimensional map unit 18, and an arrival angle estimation unit 19. The delay profile estimation unit 14_n and the electric energy calculation unit 15_n constitute an electric energy delay profile estimation unit 20_n. The electrical energy delay profile estimation units 20_1, ..., 20_N are also called first electrical energy delay profile estimation units.The electric power delay profile estimation unit 20_N+1 is also referred to as a second electric power delay profile estimation unit. Furthermore, the receiving device 1 may include a control unit that controls the radio receiving units 11_1, ..., 11_N, the group processing unit 12, the group control unit 13, the delay profile estimation units 14_1, ..., 14_N+1, the electric power calculation units 15_1, ..., 15_N+1, the synthesis unit 16, the difference unit 17, the two-dimensional map unit 18, and the arrival angle estimation unit 19.

[0016] The N radio receiving units 11_1, ..., 11_N generate N digital signals r1(k), ..., r N(k) corresponding to N received signals based on the N received signals received via the N antenna elements 10_1, ..., 10_N. The N first electrical energy delay profile estimation units 20_1, ..., 20_N estimate N delay profiles p1(m, 1), ..., p N (m, l) for electrical energy (first delay profiles for electrical energy) corresponding to the N digital signals based on the N digital signals r1(k), ..., r N (k). The synthesis unit 16 generates a synthesized delay profile q(m, 1) for electrical energy by synthesizing the N first delay profiles p1(m, 1), ..., p N(m, 1) for electrical energy. The array control unit 13 is a directivity control unit that designates (changes) a direction of a null point of the array antenna. The array control unit 13 causes the array antenna to have a directional characteristic by controlling a plurality of weight coefficients used when synthesizing the plurality of signals received by the plurality of antenna elements. The array processing unit 12 performs array processing by directing the null point in the direction designated (changed) by the array control unit 13 for the N digital signals r1(k), ..., r N (k) to generate a group processing signal y(k). The second electrical energy delay profile estimation unit 20_N+1 estimates a second delay profile p N+1(m, l) based on the group processing signal y(k). The difference unit 17 generates a differential delay profile d(m, l) for electrical energy by subtracting the second delay profile p N+1(m, l) for electric power from the synthesized delay profile q(m, l). The two-dimensional map unit 18 creates a two-dimensional map indicating a relationship between delay times and arrival angles of the incoming waves based on the difference delay profile d(m, l) for electric power and the direction of the zero point of the array antenna designated (changed) by the array control unit 13. The arrival angle estimation unit 19 estimates and outputs an arrival angle θ1 of the direct wave from the incoming waves based on the two-dimensional map indicating the relationship between the delay times and the arrival angles of the incoming waves created by the two-dimensional map unit 18.While the zero point of the array antenna is scanned (changed) in all directions by the array control unit 13, the two-dimensional map unit 18 creates the two-dimensional map indicating the relationship between the delay times and the arrival angles of the incoming waves, and the arrival angle estimation unit 19 estimates the arrival angle θ1 of the direct wave by determining a component with the shortest delay time and the largest electric energy on the two-dimensional map as a direct wave component. <1-2> Operation of the first embodiment

[0017] The radio receiving units 11_1, ..., 11_N perform frequency conversion processes for the N reception signals received via the antenna elements 10_1, ..., 10_N, respectively, to generate N baseband signals. The radio receiving units 11_1, ..., 11_N output the N digital signals obtained by performing analog-to-digital (AD) conversion of the N baseband signals. The N digital signals are supplied to the delay profile estimation units 14_1, ..., 14_N, respectively. Furthermore, the N digital signals are supplied to the group processing unit 12.

[0018] The group processing unit 12 performs group processing on the N digital signals output from the radio receiving units 11_1, ..., 11_N. The signal y(k) output by the group processing unit 12 through the group processing is expressed by the following expression (1). y(k)=∑n=1Nwnrn(k)

[0019] Here is rn (k) a signal output from the radio receiving unit 11_n (n = 1, 2, ... , N); k is a sampling number (positive integer) after AD conversion in the radio receiving unit 11_n; and w n is a complex weight coefficient for the signal r n (k).

[0020] The directional characteristic of the group antenna composed of the N antenna elements 10_1, ..., 10_N is changed depending on the complex weight coefficients w1, ..., w N of expression (1), and the origin can be directed in any direction. The group processing unit 12 performs group processing so that the origin is directed in the direction designated (changed) by the group control unit 13. The operation of the group control unit 13 will be described later.

[0021] The delay profile estimation units 14_1, ..., 14_N estimate (calculate) delay profiles from the signals r1(k), ..., r output by the radio receiver units 11_1, ..., 11_N, respectively. N (k). The delay profile estimation unit 14_N+1 estimates (calculates) a delay profile from the signal y(k) output from the group processing unit 12. The delay profile estimation method depends on a transmission method used by a communication system. The apparatus and method according to the present invention are applicable to any transmission method. Here, the estimation of the delay profile in an OFDM (Orthogonal Frequency Division Multiplex) transmission method and the estimation of the delay profile in a DSSS (Direct Sequence Spectrum Spread) transmission method, which are adopted by many communication systems, are described as examples.

[0022] First, the estimation of the delay profile in the OFDM transmission method will be described. The OFDM transmission method is a transmission method in which one symbol containing a plurality of multiplexed orthogonal subcarriers is a transmission unit. In many communication systems that use the OFDM transmission method, a portion of the subcarriers is used as a known pilot subcarrier during transmission and reception to compensate for transmission path distortion on the receiving device side. In the first embodiment, the delay profile is estimated using this pilot subcarrier.

[0023] Fig. 2 is a block diagram schematically illustrating a configuration of the delay profile estimation unit 14_n (n = 1, ..., N+1) in the OFDM transmission method. As shown in Fig. 2, the delay profile estimation unit 14_n in the OFDM transmission method includes an FFT (Fast Fourier Transform) unit 141_n, a pilot extraction unit 142_n, a pilot generation unit 143_n, a division unit 144_n, an interpolation unit 145_n, and an IFFT (Inverse Fast Fourier Transform) unit 146_n. When n = 1, ..., N, the FFT unit 141_n outputs each subcarrier by converting the signal from the radio receiving unit 11_n into Fig. 1 output signal r n(k) from a time axis to a frequency axis with respect to each symbol. When n = N + 1, the FFT unit 141_n outputs subcarriers by converting the signal y(k) output from the group processing unit 12 from the time axis to the frequency axis with respect to each symbol. The pilot extraction unit 142_n extracts pilot carriers from the signal output from the FFT unit 141_n. The pilot generation unit 143_n generates a known pilot carrier. The dividing unit 144_n generates a transfer function of a transmission path acting on the pilot carriers included in the received signal by dividing the pilot carrier extracted by the pilot extraction unit 142_n by the known pilot carrier generated by the pilot generation unit 143_n.The interpolation unit 145_n generates a transmission path transfer function for all subcarriers by performing interpolation on the transmission path transfer function acting on the pilot carriers in a symbol direction and a subcarrier direction. Finally, the IFFT unit 146_n generates the delay profile by converting the transmission path transfer function into the time axis transfer function and outputs this delay profile for each symbol.

[0024] Next, the delay profile estimation unit for the DSSS transmission method is described. The DSSS transmission method is a method that transmits signal dispersion by using a pseudo-noise sequence with respect to each symbol and eliminates the signal dispersion on the receiving device side. Fig. 3 is a block diagram schematically illustrating a configuration of the delay profile estimation unit 14_n (n = 1, ..., N+1) in the DSSS transmission method. As shown in Fig. As illustrated in Figure 3, the delay profile estimation unit 14_n of the DSSS transmission method includes a pseudo-noise sequence generation unit 148_n and a scattering removal unit 149_n. The pseudo-noise sequence generation unit 148_n generates a pseudo-noise sequence used at the time of scattering on the transmitter side. The scattering removal unit 149_n calculates a sliding correlation with the signal received from the radio receiving unit 11_n or the group processing unit 12 in Fig. 1 output signal y(k) with respect to each symbol and outputs it. This output of the scatter removal unit 149_n is the delay profile.

[0025] In the Fig. 2 and Fig. 3, the delay profile estimation unit 14_n outputs the delay profile for each symbol. The estimation result of the delay profile of the m-th symbol in the delay profile estimation unit 14_n is denoted by h n (m, l). Here, I is an index of the delay time.

[0026] In the case of the OFDM transmission method, the delay time resolution Δτ (s) is given by Δτ = 1 / W OFDM where W OFDM (Hz) denotes a bandwidth.

[0027] Furthermore, in the case of the DSSS transmission method, the delay time resolution Δτ (s) is given by Δτ = 1 / W DSSS where W DSSS (Hz) denotes a chip rate.

[0028] Furthermore, a length L of the delay profile is set such that L × Δτ becomes longer than a maximum delay time conceivable in the communication system.

[0029] The calculation units 15_1, ..., 15_N+1 for electrical energy from Fig. 1 calculate the electrical energies p n (m, l), indicated by the following expression, with respect to each delay time of the delay profiles h1(m, l), ..., h N+1 (m, l) output by the delay profile estimation units 14_1, ..., 14_N+1 and output them. pn(m,l)=|hn(m,l)|2

[0030] In addition, the electrical energy calculation units 15_1, ..., 15_N+1 can output amplitudes of the delay profiles instead of the electrical energies of the delay profiles. In the following, the electrical energies p n (m, l) of the delay profiles output by the electrical energy calculation units 15_1, ..., 15_N+1 are also called the electrical energy delay profiles.

[0031] The synthesis unit 16 in Fig. 1 synthesizes the delay profiles p1(m, 1), ..., p N (m, 1) for electrical energy output from the electrical energy calculation units 15_1, ..., 15_N, as in the following expression (2). Hereinafter, the output q(m, 1) of the synthesis unit 16 is referred to as the synthesized electrical energy delay profile. q(m,l)=∑n=1Ncnpn(m,l)

[0032] In the expression (2) c n (n = 1, ..., N) is a synthesis coefficient and is any value that satisfies the condition of the following expression (3). ∑n=1Ncn=1

[0033] If c n = 1 / N, the synthesis unit 16 synthesizes the N delay profiles p1(m, 1), ..., p N (m, 1) for electrical energy and outputs the synthesized delay profile q(m, 1) for electrical energy. In addition, if c1 = 1 and c j= 0 (j = 2, ..., N), the synthesis unit 16 outputs the electrical energy delay profile p1(m, 1) of the signal received by the antenna element 10_1 as the synthesized electrical energy delay profile q(m, 1).

[0034] The difference unit 17 in Fig. 1 gives the differential delay profile d(m, 1) for electrical energy, which is obtained by subtracting the delay profile p N+1 (m, l) for electric energy, which is the output of the electric energy calculation unit 15_N+1, is obtained from the synthesized electric energy delay profile q(m, 1) which is the output of the synthesis unit 16. That is, the differential electric energy delay profile d(m, 1) is expressed by the following expression. d(m,1)=q(m,1)−pN+1(m,1)

[0035] The Fig. 4(a) and Fig. 4(b) are diagrams illustrating an angle profile and a delay profile in a case where the delay time is long. Columns A, B, C in Fig. 5 are diagrams illustrating situations of separation of the arrival angles in the case where the delay time is long.

[0036] Here we consider a case in which a direct wave and a delay wave, as in the Fig. 4(a) and Fig. 4(b). The arrival angles of the direct wave and the delay wave are θ1 and -θ2, respectively, and the difference between the delay times of the direct wave and the delay wave is τ. If the direction θ NULL of the zero point of the group processing unit 12 under this environment is equal to θ1, the synthesized delay profile q(m, 1) for electrical energy output by the synthesis unit 16 is the delay profile p N+1(m, l) for electric energy after group processing, which is output from the electric energy calculation unit 15_N+1, and the differential delay profile d(m, l) for electric energy, which is output from the difference unit 17, as shown in column A of Fig. 5. In column A of Fig. 5, the output signal q(m, 1) of the synthesis unit 16 contains components of all incoming waves; the output signal p N+1 (m, 1) of the electrical energy calculation unit 15_N+1 contains only the delayed wave component; thus, the output signal (electrical energy differential delay profile) d(m, 1) of the differential unit 17 contains the direct wave component. That is, the electrical energy differential delay profile d(m, 1) contains the incoming wave component arriving from the direction of the zero point.

[0037] In the same way, column B and column C in Fig. 5 a case in which the direction θ NULL of the origin is equal to θ2, and a case in which the direction θ NULL of the zero point is different from both θ1 and θ2. In column B in Fig. 5, the zero point is directed in an arrival direction of the delay wave, and thus the delay wave component is included in the differential delay profile d(m, 1) for electrical energy. In column C in Fig. 5, the zero point is directed in a direction where the incoming wave does not exist, and thus the incoming wave component is not included in the differential delay profile d(m, 1) for electrical energy.

[0038] Here, it is assumed that the antenna gain of the group processing unit 12 drops steeply at the zero point.

[0039] The group control unit 13 from Fig. 1 scans (changes) the direction in which the zero point is directed by the group processing unit 12. More specifically, an initial direction of the zero point is set to θ NULL = -π, and the sampling is carried out sequentially as in θNULL=−π+a×Δθ (a=0,1,...,2π / Δθ−1). Although the scanning of all directions from -π to π is completed with respect to 0≤ a < 2π / Δθ, the scanning can be continued continuously. The index a is incremented for every M symbols. This scanning direction θ NULL of the zero point is also used in the two-dimensional map unit 18 and in the group processing unit 12.

[0040] The two-dimensional map unit 18 from Fig. 1 creates the two-dimensional map in a coordinate system in which the delay time and the arrival direction (arrival angle) are coordinate axes, by using the delay profile (output of the difference unit 17) d(m, 1) for the electric energy of the incoming wave arriving from the direction of the origin and the scanning direction (output of the group control unit 13) of the origin. Specifically, first, the two-dimensional map unit 18 calculates an average d according to the following expression (4). a (l) of differential delay profiles for electrical energy for M symbols output during a period in which the zero point is directed to θNULL=−π+a×Δθ (a=0,1,...,2π / Δθ−1). The average d a (l) of the differential delay profiles for electrical energy is also called an average differential delay profile for electrical energy. da(l)=∑m=1Md(m,l)

[0041] Next, the two-dimensional map unit 18 stores the average differential delay profile d a (l) for electric energy (l = 0, 1, ..., 1), which is expressed by the expression (4), in the a-th row in a two-dimensional array (2π / Δθ rows, L columns) prepared previously.

[0042] Fig. Figure 6 is a diagram illustrating the two-dimensional map showing the relationship between the delay time and the arrival angle in the case where the difference τ between the delay times is long. For example, the two-dimensional map shows the relationship between the delay time and the arrival angle as shown in Fig. 6 in the case of the Fig. 4(a) and Fig. 4(b). As shown in Fig. As illustrated in Figure 6, the direct wave component exists at a position of arrival angle θ1; the delay wave component exists at a position of arrival angle -θ2; and the difference between the delay times of the respective components is τ.

[0043] The arrival angle estimation unit 19 from Fig. 1 estimates the arrival angle θ1 of the direct wave by using the two-dimensional map indicating the relationship between the delay time and the arrival angle. Specifically, a certain threshold is set; components exceeding the threshold are searched in the two-dimensional map; and the component with the shortest delay time is selected from among them. This selected component is determined as the direct wave. In a case where multiple components are selected, the component with the largest electric energy is determined as the direct wave. Finally, the arrival angle estimation unit 19 outputs the arrival angle θ1 determined as the direct wave component in the two-dimensional map.

[0044] The aforementioned threshold value may be a predetermined value and may be a value obtained by attenuating the maximum value in the two-dimensional map by a certain predetermined amount.

[0045] The cases of the radio wave environment according to the Fig. 4(a) and Fig. 4(b) indicate that the direct wave and the delay wave are selected as the components larger than the threshold in Fig. 6; the direct wave is correctly identified as the component with the shortest delay time among them; and the arrival angle θ1 is output.

[0046] A fact that the first embodiment can accurately estimate the arrival angle θ1 of the direct wave even in an environment where the delay wave whose delay time is shorter than the resolution Δτ of the delay profile exists is demonstrated by using the Fig. 7(a) and Fig. 7(b), the Fig. 8 and the Fig. 9 described.

[0047] The Fig. 7(a) and Fig. 7(b) are diagrams illustrating the angle profile and the delay profile in a case where the delay time is short. Fig. 7(a) and Fig. 7(b) illustrate a radio wave environment in which a delay wave whose delay time difference τ is shorter than the resolution Δτ of the delay profile (τ ≤ Δτ) exists. The arrival angles of Fig. 7(a) are the same as those in Fig. 4(a), and the delay times of Fig. 7(b) are different from those of Fig. 4(b).

[0048] Fig. 8 is a diagram showing the synthesized delay profile (output of the synthesis unit 16) q(m, 1) for electrical energy, the delay profile (output of the calculation unit 15_N+1 for electrical energy) p N+1(m, l) for electrical energy when the zero point is directed in a certain direction, and the differential delay profile (output signal of the difference unit 17) d(m, l) for electrical energy calculated in this environment. Fig. Figure 8 is a schematic diagram in which the direct wave and the delay wave are indicated by a black circle and a white rhombus, respectively, and are therefore distinguishable. In fact, the delay time of the delay wave is shorter than the delay time resolution of the delay profile, and thus the direct wave and delay wave components overlap each other in the synthesized delay profile q(m, 1) of the electrical energy. That is, it appears as if there is only one incoming wave.

[0049] Columns A, B, C in Fig. 8 are diagrams illustrating situations of separation of the arrival angles in the case where the delay time is short. In the first embodiment, the respectively described direct wave and delay wave can be separated by scanning (changing) the origin in the group processing. For example, when the direction θ NULL of the zero point of the group processing unit 12 is equal to θ1, the direct wave is suppressed by the group processing unit 12, and thus the direct wave component is not included in the output signal of the electric energy calculation unit 15_N+1, as shown in column A in Fig. 8. Thus, the output signal of the differential unit 17 contains the direct wave component, and the delay wave component is not included. That is, the incoming wave arriving from the direction of the zero point is included in the differential delay profile d(m, 1) for electrical energy, in the same way as in the case of the radio wave environment of the Fig. 4(a) and Fig. 4(b), regardless of the delay time of the delay wave.

[0050] In the same way, a case where the direction θ NULL of the origin is equal to θ2, and a case in which the direction θ NULL of the zero point differs from θ1 and θ2, respectively, in column B and column C from Fig. 8. In column B of Fig. 8, the zero point is directed in the arrival direction of the delay wave, and thus the delay wave component is included in the differential delay profile d(m, 1) for electrical energy. In column C of Fig. 8, the zero point is directed in a direction where the incoming wave does not exist, and thus the incoming wave components are not included in the differential delay profile d(m, 1) for electrical energy.

[0051] Fig. Figure 9 is a diagram illustrating the two-dimensional map showing the relationship between the delay time and the arrival angle in the case where the delay time is short. The two-dimensional map obtained by scanning the origin in all directions is shown in Fig. 9. Although the direct wave and the delay wave are shown as larger components than the threshold in the two-dimensional map of Fig. 9 are selected, the delay time is shorter than the resolution of the delay profile, and thus both components exist at the index of the same delay time. In a case where multiple components exist at the same delay time, the component with the largest electrical energy can be determined as the direct wave, since the delay wave loses electrical energy when reflected by an obstacle and thus becomes smaller in electrical energy than the direct wave. Based on Fig. 9, it is realized that the one with the larger electric energy among the direct wave and the delay wave existing at the index of the same delay time is determined as the direct wave, and the arrival angle θ1 is output from the arrival angle estimation unit 19. <1-3> Effect of the first embodiment

[0052] The device described in Patent Document 1 is unable to separate the direct wave and the delay wave in the environment where the delay wave exists whose delay time is shorter than the delay time resolution of the delay profile, and the estimation accuracy of the arrival angle of the direct wave is deteriorated. In contrast, according to the receiving device 1 and the receiving method of the first embodiment, the effect is obtained that the direct wave and the delay wave can be separated by using the zero point of the array antenna, and that the arrival angle θ1 of the direct wave can be accurately estimated according to the Fig. 5 and Fig. 8 illustrated principle.

[0053] Furthermore, it is generally known that the null point of the array antenna has a sharper directivity than the main lobe. Therefore, the receiving device according to the first embodiment can separate multiple incoming waves even with a smaller number of antenna elements compared to the method described in Patent Document 2 and the device described in Patent Document 3 that separate the incoming waves by using the main lobe, and the estimation accuracy of the arrival angle θ1 of the direct wave can be improved. <2> Second Embodiment<2-1> Configuration of the Second Embodiment

[0054] The receiving device 1 according to the first embodiment utilizes the fact that the antenna gain of the group processing unit 12 in Fig. 1 drops steeply at the zero point. However, in fact, as the number of antenna elements constituting the array antenna decreases, the attenuation of the antenna gain around the zero point becomes more gradual, and as a result, a width of the zero point becomes larger. The width of the zero point is narrower than the main lobe, and thus, when the number of antenna elements is the same, the receiving apparatus according to the first embodiment estimates the arrival angle of the direct wave more accurately than the apparatus and method described in Patent Documents 2 and 3. However, as the number of antenna elements constituting the array antenna decreases, the width of the zero point spreads, and the estimation accuracy of the arrival angle θ1 of the direct wave is deteriorated by this width spread.Therefore, a receiving device 2 according to a second embodiment corrects the scattering of the width of the zero point in the two-dimensional map and suppresses the deterioration of the estimation accuracy of the arrival angle θ1 of the direct wave.

[0055] Fig. 10 is a block diagram schematically illustrating a configuration of the receiving device 2 according to the second embodiment of the present invention. In Fig. 10 are the components that are the same as those in Fig. 1 illustrated components or correspond to them, with the same reference numerals as those shown in the Fig. 1. The receiving device 2 according to the second embodiment differs from the receiving device 1 according to the first embodiment in that it includes a correction unit 40 between the two-dimensional map unit 18 and the arrival angle estimation unit 19. Except for this point, the second embodiment is the same as the first embodiment.

[0056] The correction unit 40 from Fig. 10 corrects the scattering of the width of the zero point by performing a filtering process in the direction of the arrival angle in the two-dimensional map, which displays the relationship between the delay time and the arrival angle of the incoming wave. <2-2> Operation of the second embodiment

[0057] The Fig. 11(a) and Fig. 11(b) are diagrams illustrating the two-dimensional map indicating the relationship between the delay time and the arrival angle in the case where the delay time is long in the second embodiment. Here, the Fig. 4. When the number of antenna elements is small and the width of the zero point is large, the two-dimensional map showing the relationship between the delay time and the arrival angle is as shown in Fig. 11(a), and f a (θ), which is obtained by cutting out the component of the direct wave in the direction of the angle of arrival, is in Fig. 11(b). A form of scattering in the direction of the angle of arrival of Fig. 11(b) is uniquely determined from a shape of the array antenna's directional characteristic and is thus known. If this known dispersion of the arrival angle is equal to g(θ), Fig. 11(b) is expressed by the following expression. fa(θ)=g(θ−θ1)=g(θ)⊗δ(θ−θ1)(⊗ is a convolution operation)

[0058] In expression (5), δ(θ) is a delta function which is 1 when θ = 0.

[0059] The Fig. 12(a) and Fig. 12(b) are diagrams illustrating the two-dimensional map indicating the relationship between the delay time and the arrival angle in the case where the delay time is short in the second embodiment. In addition, the Fig. 7(a) and Fig. 7(b) is considered. When the number of antenna elements is small and the zero point has a width, the two-dimensional map showing the relationship between the delay time and the arrival angle is as shown in Fig. 12(a). The delay time is shorter than the delay time resolution of the delay profile, and thus the direct wave and the delay wave exist on the same delay time index. In this case, f b (θ), which is obtained by cutting out the components of the direct wave and the delay wave in the direction of the arrival angle, in Fig. 12(b). This f b (θ) can be expressed by the following expression. fb(θ)=g(θ−θ1)+g(θ+θ2)=g(θ)⊗(δ(θ−θ1)+δ(θ+θ2))

[0060] Using expression (5) and expression (6), the signal (hereinafter referred to as f a (θ) and f b(θ) expressed by f(θ)), which is obtained by cutting out the two-dimensional map in which the width of the zero point is large at a certain delay time, a convolution of g(θ) calculated from the shape of the directional characteristic of the array antenna, and an ideal signal with a very narrow zero point width (the term expressed by the delta function).The convolution operation is converted to multiplication by a Fourier transform, and thus it is understood that in order to correct the dispersion of the width of the zero point, it is sufficient to calculate F(ξ) by applying the Fourier transform to f(θ) obtained by clipping the two-dimensional map at the specific delay time, calculate F'(ξ) = F(ξ) / G(ξ) by dividing this F(ξ) by G(ξ) obtained by applying the Fourier transform to g(θ), and then calculate a result f'(θ) obtained by applying an inverse Fourier transform to F'(ξ).

[0061] Fig. 13 is a block diagram schematically showing a configuration of the correction unit 40 of Fig. 10. A Fourier transform (FFT) unit 401 calculates F l (ξ) (l = 0, 1, ..., L-1) by applying the Fourier transform to f l(θ), which was obtained by cutting out the two-dimensional map at the delay time index 1 (1 = 0, 1, ..., L- 1). A correction coefficient generation unit 402 outputs G(ξ) prepared in advance. A division unit 403 calculates F l (ξ) / G(ξ) (l = 0, 1, ..., L -1) by dividing the signal output from the Fourier transform unit 401 by the signal output from the correction coefficient generation unit 402. Finally, an inverse Fourier transform (IFFT) unit 404 outputs a result obtained by applying the inverse Fourier transform to the output signal of the division unit.

[0062] The aforementioned θ and ξ are discrete signals, and a discrete Fourier transform and an inverse discrete Fourier transform are performed as the Fourier transform and the inverse Fourier transform. Furthermore, when the sample number 2π / Δθ is a power of 2, FFT and IFFT can achieve this. <2-3> Effect of the second embodiment

[0063] As described above, in the receiving device 2 and the receiving method according to the second embodiment, when the number N of antenna elements is comparatively small, the drop in the array antenna gain around the zero point is gradual, and the width of the zero point is large. Therefore, the two-dimensional map is corrected by using the dispersion shape of the zero point, which is uniquely determined from the shape of the directivity of the array antenna. Therefore, there is an effect of improving the estimation accuracy of the arrival angle θ1 of the direct wave. <3> Third Embodiment<3-1> Configuration of the third embodiment

[0064] The receiving devices 1 and 2 according to the first and second embodiments estimate the arrival angle θ1 of the direct wave while sequentially changing the direction of the zero point with respect to the signals received by the array antenna. This operation is effective in a case where the transmitter continuously transmits the radio wave. However, in a case where the transmitter transmits a signal with a predetermined frame length, it is possible that the sampling of the zero point (i.e., the process of estimating the arrival angle θ1 of the direct wave while sequentially changing the direction of the zero point) is not completed during the frame period of the signal.

[0065] Thus, a third embodiment provides a receiving apparatus 3 and a receiving method that can also handle the case where the frame length of a frame constituting a signal transmitted from the transmitter is limited.

[0066] Fig. 14 is a block diagram schematically illustrating a configuration of the receiving device 3 according to the third embodiment of the present invention. In Fig. 14 are the components that are the same as those in Fig. 1 illustrated components or correspond to them, with the same reference numerals as those in Fig. 1. The Fig. The receiving device 3 illustrated in Figure 14 differs from the receiving device 1 according to the first embodiment in that it includes signal storage units 60_1, ..., 60_N and a profile storage unit 61. Regarding the other points, the receiving device 3 according to the third embodiment is the same as the receiving device 1 according to the first embodiment. <3-2> Operation of the third embodiment

[0067] In the third embodiment, a reception signal with a predetermined period of T seconds is used. Here, T is a time equal to or shorter than the frame length of the transmission signal.

[0068] The signal storage units 60_1, ..., 60_N from Fig. 14 temporarily store the output signals of the radio receiving units 11_1, ..., 11_N of T seconds. In addition, the profile storage unit 61 temporarily stores the synthesized delay profile q(m, 1) for electrical energy calculated from the received signals of T seconds. During the T seconds in which the radio receiving units 11_1, ..., 11_N receive the signal via the antenna elements, the radio receiving units 11_1, ..., 11_N, the delay profile estimation units 14_1, ..., 14_N, the electrical energy calculation units 15_1, ..., 15_N, and the synthesis unit 16 are composed of Fig. 14 in operation, but the remaining functions are not in operation.

[0069] At a time point when the storage of the signals of T seconds in the signal storage units 60_1, ..., 60_N and the profile storage unit 61 has been completed, the group processing unit 12, the group control unit 13, the delay profile estimation unit 14_N+1, the electric energy calculation unit 15_N+1, the difference unit 17, the two-dimensional map unit 18, and the arrival angle estimation unit 19 start their operations.

[0070] The group control unit 13 changes the direction of the zero point every M symbols. Only the signals of T seconds exist in the signal storage units 60_1, ..., 60_N, and thus the group processing unit 12 samples the zero point in all directions by repeatedly reading the signals of T seconds. The operations of the delay profile estimation unit 14_N+1 and the electrical energy calculation unit 15_N+1 are the same as in the first embodiment.

[0071] The difference unit 17 reads the synthesized delay profile q(m, 1) of the electrical energy from the profile storage unit 61 and calculates the difference delay profile d(m, 1) for electrical energy with respect to the delay profile p N+1(m, 1) for electric power, which is output every M symbols from the electric power calculation unit 15_N+1. The operations of the two-dimensional map unit 18 and the arrival angle estimation unit 19 are the same as in the case of the first embodiment.

[0072] In addition, the correction unit 40 described in the second embodiment can be added to the receiving device 3 according to the third embodiment, <3-3> Effect of the third embodiment

[0073] As described above, the receiving device 3 according to the third embodiment stores the signals corresponding to the reception signals of the predetermined period of T seconds and creates the two-dimensional map while repeatedly reading out the signals, and thereby obtains the effect that the arrival angle θ1 of the direct wave can be accurately estimated even in a case where the frame length is limited. <4> Fourth Embodiment<4-1> Process according to the fourth embodiment

[0074] A receiving method according to a fourth embodiment is the same as the process by the receiving device 1 according to the first embodiment. Thus, Fig. 1 is also included in the description of the fourth embodiment.

[0075] The receiving method according to the fourth embodiment includes a step (S1) of initializing (setting in a predetermined direction) the zero direction by the group control unit 13, a receiving step (S2) of receiving a radio signal by the radio receiving units 11_1, ..., 11_N, and a first estimation step (S3, S4) of estimating N first delay profiles p1 (k), ..., p N (k) for electrical energy. Furthermore, the receiving method according to the fourth embodiment includes a synthesis step (step S5) of generating the synthesized delay profile q(m, 1) for electrical energy, a group processing step (S6) of generating the group processing signal y(k), and a second estimation step (S7, S8) of estimating the second delay profile p N+1(m, l) for electrical energy from the group processing signal y(k). Furthermore, the receiving method according to the fourth embodiment includes a differential step (S9) of generating the differential delay profile d(m, l) for electrical energy by subtracting the second delay profile p N+1(m, l) for electric energy from the synthesized delay profile q(m, 1) of the electric energy and a two-dimensional map step (S10) for creating the two-dimensional map indicating the relationship between the delay time and the arrival angle of the incoming wave, based on the difference delay profile d(m, 1) for electric energy and the direction of the zero point designated (changed) by the group control unit 13.Furthermore, the receiving method according to the fourth embodiment includes a step (S11, S12) of changing the direction of the zero point by scanning the zero point by the group control unit 13 to repeatedly perform the receiving step (S2), the first estimation step (S3, S4), the synthesis step (S5), the group processing step (S6), the second estimation step (S7, S8), the difference step (S9), and the two-dimensional map step (S10), and an arrival angle estimation step (S13) of estimating and outputting the arrival angle θ1 of the direct wave from the incoming waves when the zero point scanning with respect to all directions is completed. In the arrival angle estimation step (S13), a component with the shortest delay time and the largest electric energy in the carrier wave on the two-dimensional map is determined as the direct wave, and the arrival angle θ1 of the direct wave is estimated.

[0076] Next, the receiving method according to the fourth embodiment will be described in more detail based on Fig. 15. In the step (S1) for initializing the zero direction from Fig. 15, the group control unit 13 performs initialization, which is a process of setting the null direction of the group antenna to, for example, -π.

[0077] In the receiving step (S2), with respect to the signals received by the N antenna elements 10_1, ..., 10_N, the radio receiving units 11_1, ..., 11_N each convert the received signal into the baseband signal by performing the frequency conversion and generate the digital signals r1(k), ..., r N (k) by performing AD conversion of this baseband signal. The process of the receiving step (S2) is the same as the process by the radio receiving units 11_1, ..., 11_N in the first embodiment.

[0078] In the first estimation step (S3, S4) the delay profiles h n (m, l), corresponding to the N antenna elements 10_1, ..., 10_N, based on the digital signals r1(k), ..., r N (k) generated in the receiving step S2. The calculation method for the delay profiles depends on the transmission method used by the communication system.

[0079] Fig. 16 is a flowchart illustrating the step (S3) of estimating the first delay profiles in the OFDM transmission method. The process of Fig. 16 is the same process as the process of Fig. 2 in the first embodiment. As in Fig. 16, the step (S3) of estimating the first delay profiles includes, for example, an FFT step (S21), a pilot extraction step (S22), a pilot generation step (S23), a division step (S24), an interpolation step (S25), and an IFFT step (S26). In the FFT step (S21), the digital signals r1 (k), ..., r N (k) which in the receiving step (S2) of Fig. 15 are converted from the time axis to the frequency axis with respect to each symbol, and thereby the subcarriers are generated. The pilot carriers generated in the FFT step (S21) are extracted in the pilot extraction step (S22), and the known pilot carrier is generated in the pilot generation step (S23). In the dividing step (S24), the pilot carrier extracted in the pilot extraction step (S22) is divided by the known pilot carrier generated in the pilot generation step (S23), and thereby the transfer function of the transmission path acting on the pilot carriers included in the received signal is generated. In the interpolation step (S25), the transfer function of the transmission path is generated for all subcarriers by performing interpolation on the transfer function of the transmission path acting on the pilot carriers in the symbol direction and the subcarrier direction.In the IFFT step (S26), the delay profile is generated by converting the transfer function of the transmission path into the transfer function of the time axis. The delay profile shown in . Fig. 16 is the same as the process by the delay profile estimation units 14_1, ..., 14_N+1 in the first embodiment ( Fig. 1 and Fig. 2).

[0080] Fig. Figure 17 is a flowchart illustrating the step (S3) of estimating the first delay profiles in the DSSS transmission method. The process in Fig. 17 is the same process as the process in Fig. 3 according to the first embodiment. As in Fig. 17, the step (S3) of estimating the first delay profiles includes, for example, a step (S31) of generating the pseudo-noise sequence and a step (S32) of performing a scattering removal process. The pseudo-noise sequence used at the time of scattering on the transmitter side is generated in the pseudo-noise sequence generation step (S31), and the sliding correlation with the signal obtained in the receiving step (S2) of Fig. 15 is calculated and output for each symbol in the scatter removal step (S32). This output signal in the scatter removal step is the delay profile. The Fig. 17 is the same as the process by the delay profile estimation units 14_1, ..., 14_N+1 in the first embodiment ( Fig. 1 and Fig. 3).

[0081] As in the Fig. 16 and Fig. 17, the delay profile is output for each symbol. In the following, the delay profile estimation result of the m-th symbol for the n-th antenna element is denoted by h n (m, l). Here, 1 is the delay time index. The delay time resolution Δτ has already been described in the first embodiment.

[0082] In the step (S4) of calculating the electrical energy of the first delay profiles of Fig. 15 the electrical energy p n (m, l) (n = 1, ..., N) is calculated and output for each delay time of the delay profile generated in the first delay profile estimation step (S3). The process of step (S4) is the same as the process by the electric energy calculation units 15_1, ..., 15_N in the first embodiment.

[0083] In the synthesis step (S5) of Fig. 15, the first electrical energy delay profiles generated in step (S4) are synthesized to generate the synthesized electrical energy delay profile q(m, 1). The process of step (S5) is the same as the process by the synthesis unit 16 in the first embodiment.

[0084] The group processing step (S6) of Fig. 15 carries out the group processing for the signals r1 (k), ..., r generated in the receiving step (S2) N (k). The process of step (S6) is the same as the process of the group processing unit 12 in the first embodiment.

[0085] In the estimation step (S7) of the second delay profile of Fig. 15, the delay profile is estimated based on the signal y(k) generated by the group processing. The estimation method for the delay profile is the same as the estimation step (S3) for the first delay profile. Furthermore, the process of the estimation step (S7) is the same as the process by the delay profile estimation unit 14_N+1 in the first embodiment.

[0086] The second calculation step (S8) for electrical energy of Fig. 15 calculates and outputs the electric energy for each delay time of the delay profile generated in the second delay profile estimation step (S7). The electric energy calculation method is the same as the first delay profile estimation step (S4). Furthermore, the process of step (S8) is the same as the process by the electric energy calculation unit 15_N+1 in the first embodiment.

[0087] The difference step (S9) of Fig. 15 outputs the differential delay profile d(m, 1) for electrical energy, which is obtained by subtracting the second delay profile p n+1 The electrical energy delay profile q(m, l) generated in the second electrical energy calculation step (S8) is obtained from the synthesized electrical energy delay profile q(m, l) generated in the synthesis step (S6). The process of the difference step (S9) is the same as the process by the difference unit 17 in the first embodiment.

[0088] The two-dimensional map step (S10) of Fig. 15 creates the two-dimensional map of the delay time (arrival time) and arrival direction (arrival angle) of the incoming wave by using the delay profile (output of the differential step) for the electric energy of the incoming wave arriving from the zero-point direction and the zero-point direction. The process of the two-dimensional map step (S10) is the same as the process by the two-dimensional map unit 18 in the first embodiment.

[0089] The zero direction update step (S11) of Fig. 15 sequentially samples the zero direction at Δθ intervals as in θNULL=−π+ a+Δθ (a=0,1,...,2π / Δθ−1) During a period of 0 ≤ a < 2π / Δθ, the receiving step (S2) is repeatedly performed up to the zero direction update step (S11). When a = 2π / Δθ, the scanning of the zero direction in all directions from -π to π is completed, and thus the process proceeds to the next step. The scanning direction θ NULL of the origin is also used in the two-dimensional map step (S10).

[0090] The arrival angle estimation step (S13) of Fig. 15 estimates the arrival angle θ1 of the direct wave by using the two-dimensional map indicating the relationship between the delay time and the arrival angle of the incoming wave. Specifically, a certain threshold is set; components exceeding the threshold are searched in the two-dimensional map; and the component with the shortest delay time is selected from among them. The selected component is determined as the direct wave. If multiple components are selected, the component with the largest electric energy is determined as the direct wave. Finally, in the arrival angle estimation step (S13), the arrival angle determined as the direct wave component in the two-dimensional map is output.The aforementioned threshold value may be determined in advance and may be a value attenuated by a certain predetermined amount from the maximum value on the two-dimensional map. The process of the arrival angle estimation step (S13) is the same as the process by the arrival angle estimation unit 19 in the first embodiment.

[0091] The flowchart of Fig. The process illustrated in Fig. 15 is the same as the operation of the receiving device 1 according to the first embodiment. In addition, a process step by the correction unit 40 ( Fig. 10, Fig. 13) from the second embodiment before the arrival angle estimation step (S13) from Fig. 15 should be inserted. <4-2> Effect of the fourth embodiment

[0092] In Patent Document 1, in the environment where the delay wave exists whose delay time is shorter than the delay time resolution of the delay profile, the direct wave and the delay wave cannot be separated, and the estimation accuracy of the arrival angle of the direct wave deteriorates; whereas, in the fourth embodiment, the direct wave and the delay wave can be separated by using the zero point of the array antenna in the same manner as in the first embodiment, and the effect that the arrival angle of the direct wave can be accurately estimated is obtained.

[0093] Furthermore, it is generally known that the null point of the array antenna has a sharper directivity than the main lobe. Therefore, in the same way as the first embodiment, the fourth embodiment achieves the effect that it can separate multiple incoming waves even with a smaller number of antenna elements, compared to the technology described in Patent Document 2 and Patent Document 3 that separates incoming waves by using the main lobe, and that the estimation accuracy of the arrival angle θ1 of the direct wave can be improved. <5> Example variant

[0094] Fig. Fig. 18 is a hardware configuration diagram illustrating a configuration example of the receiving devices according to the above-described first to third embodiments. Fig. The receiving device 1 illustrated in Fig. 18 includes a memory 91 as a storage device for storing a program as software and a processor 92 as an information processing unit for executing the program stored in the memory 91. The Fig. 18 illustrates a specific example of the structures of the receiving devices according to the first to third embodiments. The operation of the receiving devices shown in Fig. The operation of the receiving device 1 illustrated in Figure 18 is the same as the operation of the receiving devices according to the first to third embodiments or the receiving method according to the fourth embodiment. The program stored in the memory 91 is a program that can be executed in a computer including the processor 92, and it can cause the computer to perform the process illustrated in the fourth embodiment ( Fig. 15) can carry out

[0095] If the Fig. 18, the receiving device 1 performs the processes in the receiving devices according to the first to third embodiments, each component of the Fig. 1, Fig. 10 and Fig. 14 is implemented by the processor 92, which executes the program stored in the memory 91. Although a case in which the processor 92 and the memory 91 are used to control each component of the Fig. 1, Fig. 10 and Fig. 14 illustrated receiving device, as an example, a part of the components may be selected from the components of the Fig. 1, Fig. 10 and Fig. 14 may be configured by the processor 92 and the memory 91, and other parts may be configured by a hardware circuit. The receiving operation described in the first to third embodiments may be implemented by the Fig. 18 illustrated receiving device can be realized. DESCRIPTION OF REFERENCE SYMBOLS 1, 2, 3 receiving device, 10_1, ..., 10_N antenna element, 11_1, ..., 11_N radio receiving unit, 12 group processing unit, 13 group control unit, 14_1, ..., 14_N+1 delay profile estimation unit, 15_1, ..., 15_N+1 calculation unit for electrical energy, 16 synthesis unit, 17 Differential unit, 18 Two-dimensional map unit, 19 Arrival angle estimation unit, 20_1, ..., 20_N Delay profile estimation unit for electrical energy (first delay profile estimation unit for electrical energy), 20_N+1 delay profile estimation unit for electrical energy (second delay profile estimation unit for electrical energy), 40 correction units, 60_1, ..., 60_N signal storage unit, 61 profile storage unit, 141_n FFT unit, 142_n pilot extraction unit, 143_n pilot generation unit, 144_n division unit, 145_n interpolation unit, 146_n IFFT unit, 148_n Pseudo noise sequence generation unit, 149_n Scattering removal unit, 401 Fourier transform unit 402 Correction coefficient generation unit 403 division unit 404 Inverse Fourier transform unit.

Claims

[1] Receiving device (1, 2, 3) for receiving incoming waves which are radio waves arriving at an array antenna containing a plurality of antenna elements (10_1, ..., 10_N), which receiving device (1, 2, 3) comprises: a plurality of radio receiving units (11_1, ..., 11_N) that generate a plurality of digital signals corresponding to a plurality of signals based on the plurality of signals received via the plurality of antenna elements (10_1, ..., 10_N); a first electric power delay profile estimation unit (20_1, ..., 10_N) that estimates a plurality of first electric power delay profiles corresponding to the plurality of digital signals based on the plurality of digital signals; a synthesis unit (16) that generates a synthesized electrical energy delay profile by synthesizing the plurality of first electrical energy delay profiles; a group control unit (13) that changes a direction of a zero point of the group antenna; a group processing unit (12) that generates a group processing signal by performing group processing for the plurality of digital signals by directing the zero point in the direction changed by the group control unit (13); a second delay profile estimation unit (20_N+1) that estimates a second electrical energy delay profile from the group processing signal; a difference unit (17) that generates a differential electrical energy delay profile obtained by subtracting the second electrical energy delay profile from the synthesized electrical energy delay profile; a two-dimensional map unit (18) that forms a two-dimensional map indicating a relationship between delay times and arrival angles of the incoming waves on the basis of the differential delay profile for electric energy and the direction of the zero point changed by the group control unit (13); and an arrival angle estimation unit (19) that outputs an arrival angle of a component having a shortest delay time and a largest electric energy from the incoming waves on the two-dimensional map. [2] Receiving device (2) according to claim 1, further comprising: a correction unit (40) which corrects the two-dimensional map formed by the two-dimensional map unit (18) and supplies the corrected two-dimensional map to the arrival angle estimation unit (19), wherein the correction unit (40) contains: a Fourier transform unit (401) that applies a Fourier transform to a component of an arrival angle direction at each delay time on the two-dimensional map formed by the two-dimensional map unit (18); a division unit (403) which divides a signal output from the Fourier transform unit (401) by a correction coefficient; and an inverse Fourier transform unit (404) that applies an inverse Fourier transform to a signal output from the dividing unit (403), wherein the correction coefficient is calculated on the basis of a shape of a directional characteristic of the array antenna. [3] Receiving device (3) according to claim 1 or 2, further comprising: a signal storage unit (60_1, ..., 60_N) that stores the plurality of digital signals generated by the plurality of radio receiving units (11_1, ..., 11_N); and a profile storage unit (61) which stores the synthesized delay profile of the electrical energy generated by the synthesis unit (16), wherein the two-dimensional map unit (18) forms the two-dimensional map on a basis of the plurality of digital signals stored in the signal storage unit (60_1, ..., 60_N) and the synthesized electric energy delay profile stored in the profile storage unit (61). [4] Receiving device (1, 2, 3) according to one of claims 1 to 3, further comprising the group antenna. [5] Receiving device (1, 2, 3) according to one of claims 1 to 4, wherein the change of the zero point by the group control unit (13) is carried out within a range of -π to +π of the arrival angles of the incoming waves. [6] A receiving method for receiving incoming waves which are radio waves arriving at an array antenna including a plurality of antenna elements (10_1, ..., 10_N), which receiving method comprises: a receiving step of generating a plurality of digital signals corresponding to a plurality of signals based on the plurality of signals received via the plurality of antenna elements (10_1, ..., 10_N); a first estimation step of estimating a plurality of first electrical energy delay profiles corresponding to the plurality of digital signals based on the plurality of digital signals; a synthesis step of generating a synthesized electric power delay profile by synthesizing the plurality of first electric power delay profiles; a group processing step of changing a direction of a null point of the array antenna and generating a group processing signal by performing group processing for the plurality of digital signals by directing the null point in the changed direction; a second estimation step of estimating a second delay profile for electrical energy from the group processing signal; a differential step of generating a differential electric power delay profile obtained by subtracting the second electric power delay profile from the synthesized electric power delay profile; a two-dimensional map step of forming a two-dimensional map indicating a relationship between delay times and arrival angles of the incoming waves, on a basis of the differential delay profile for electric energy and the changed direction of the zero point; a step of changing the direction of the zero point and performing the receiving step, the first estimation step, the synthesis step, the group processing step, the second estimation step, the difference step, and the two-dimensional map step; and an arrival angle estimation step of outputting an arrival angle of a component having a shortest delay time and a largest electric energy from the incoming waves on the two-dimensional map.

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