WO2024023933A1 - Antenna device - Google Patents

Antenna device Download PDF

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WO2024023933A1
WO2024023933A1 PCT/JP2022/028803 JP2022028803W WO2024023933A1 WO 2024023933 A1 WO2024023933 A1 WO 2024023933A1 JP 2022028803 W JP2022028803 W JP 2022028803W WO 2024023933 A1 WO2024023933 A1 WO 2024023933A1
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Prior art keywords
arrangement
antenna
waves
wave
antenna elements
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PCT/JP2022/028803
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French (fr)
Japanese (ja)
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浩之 福本
洋輔 藤野
誓治 大森
勇弥 伊藤
美春 大岩
亮太 奥村
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日本電信電話株式会社
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Priority to PCT/JP2022/028803 priority Critical patent/WO2024023933A1/en
Publication of WO2024023933A1 publication Critical patent/WO2024023933A1/en

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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L15/00—Speech recognition
    • G10L15/28—Constructional details of speech recognition systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station

Definitions

  • the present invention relates to a technology for receiving wireless signals transmitted using radio waves and sound waves (including ultrasonic waves).
  • ISI Inter-symbol-interference
  • CCI co-channel interference
  • the term "antenna” is used to represent a concept that is not limited to a configuration for receiving radio waves, but also includes a configuration for receiving sound waves (including ultrasonic waves). Furthermore, in the following description, waves such as multipath waves and interference waves that may affect the reception of the desired wave (direct wave) to be received are referred to as "unnecessary waves.”
  • an array antenna is equipped with an FIR (Finite Impulse Response) filter and an FB (Feed-back) filter for each array antenna, and the filter coefficients are determined using an optimization algorithm such as the LMS (Least Mean Square) method or the RLS (Recursive Least Square) method. There is a method to perform optimization.
  • FIR Finite Impulse Response
  • FB Breast Biharmonic Switching Function
  • LMS Least Mean Square
  • RLS Recursive Least Square
  • the suppression performance of unnecessary waves in the spatial domain is fundamentally determined by the shape of the array antenna. Since the size of the aperture of the array antenna determines the spatial resolution, generally speaking, the wider the aperture, the better the unnecessary wave suppression performance. In other words, the larger the overall size of the array antenna, the more effectively it is possible to suppress unnecessary waves that have a small angular difference from the desired wave.
  • Spatial aliasing means that when the direction of arrival of a signal is expressed as a vector by using the phase difference between antenna elements, a combination of linearly dependent directions of arrival occurs.
  • a vector indicating the direction of arrival of a signal will be referred to as a "steering vector.”
  • antenna elements may not be arranged at intervals of half a wavelength or less depending on the aperture width of the array depending on the angular resolution.
  • spatial aliasing may occur within the transmission frequency band depending on the arrangement pattern. Specifically, there are the following cases.
  • the present invention aims to provide a technology that can improve the performance of equalization processing performed when receiving desired waves that are radio waves or sound waves (including ultrasonic waves) to be received.
  • One aspect of the present invention includes N antenna elements (N is an integer of 3 or more) that receive sound waves or radio waves, and the antenna elements each have a steering vector corresponding to an incident angle ⁇ of a certain sound wave or radio wave, and a steering vector corresponding to an incident angle ⁇ of a certain sound wave or radio wave.
  • This is an antenna device in which the steering vector corresponding to the incident angle ⁇ _d ( ⁇ _d is ⁇ /2 to + ⁇ /2) of the sound wave or radio wave is located at a position that is not linearly dependent.
  • FIG. 3 is a diagram showing a specific example of the arrangement of antenna elements 11 in the antenna device 10 configured as an array antenna.
  • 1 is a diagram showing a configuration example of a receiving system 100.
  • FIG. It is a figure showing an outline of computer simulation. It is a figure showing an outline of computer simulation. These are the specifications of the transmission signal in computer simulation. These are the specifications of antenna placement for comparative evaluation using computer simulation.
  • FIG. 3 shows a comparison of sequences. These are simulation results.
  • FIG. 3 is a diagram showing a first specific example of a two-dimensional arrangement. It is a figure which shows the second specific example of two-dimensional arrangement
  • FIG. 1 is a diagram showing a specific example of the arrangement of antenna elements 11 in an antenna device 10 configured as an array antenna.
  • the antenna device 10 includes at least three antenna elements 11.
  • the antenna element 11 receives waves such as radio waves and sound waves (including ultrasonic waves) and generates electrical signals corresponding to the waves.
  • the antenna element 11 is arranged one-dimensionally or two-dimensionally. With this arrangement, the antenna device 10 is configured as an array antenna. In the example of FIG. 1, N antenna elements 11 are arranged on a one-dimensional line. That is, the antenna device 10 in the example of FIG. 1 is configured as a linear array. Each antenna element 11 is given a code from #0 to #N-1.
  • the #i antenna element is placed d_i away.
  • the description "A_B” indicates a description in which "B” is placed as a subscript at the lower right of "A”. It is assumed that the received waves (including desired waves and unnecessary waves) are incident from any direction at an angle ⁇ ( ⁇ is ⁇ /2 to + ⁇ /2).
  • Equation 1 When the steering vector corresponding to the incident angle ⁇ and the steering vector corresponding to another arrival direction ⁇ _d ( ⁇ _d is ⁇ /2 to + ⁇ /2) are linearly dependent, the following conditional expression (Equation 1) is satisfied. It is filled.
  • ⁇ is a wavelength corresponding to any frequency within the transmission band.
  • the transmission band refers to a band that is assumed to be used in transmitting a desired wave (direct wave) to be received.
  • the numerical range of each ⁇ _n is shown by Equation 2 below.
  • Equation 3 By rearranging Equation 1, the following Equation 3 can be obtained.
  • m and n are each a set of integers from 1 to (N-1). For all pairs of m and n where m and n are different, if there is at least one set of ⁇ _1, ..., ⁇ _(N-1) that satisfies Equation 4 shown below, in a direction different from the incident angle ⁇ . One or more linearly dependent directions of arrival occur. In other words, when ⁇ _1 to ⁇ _(N-1) form a set that satisfies Expression 3, one or more linearly dependent arrival directions occur in a direction different from the incident angle ⁇ .
  • the ratio of the element spacing (d_n'/d_m') of at least one of the set of d_n and d_m is an irrational number
  • the arrangement of the antenna element 11 under such conditions is called a first arrangement.
  • d_1 be a value that is 1/2 or more of the minimum wavelength within the transmission band and less than the minimum wavelength.
  • ⁇ _1 can only take +1 or ⁇ 1 for all wavelengths within the transmission band.
  • d_2 is arranged so that it is not an integral multiple of d_1, linear dependence of the steering vectors will not occur.
  • the arrangement of the antenna element 11 under such conditions is called a second arrangement.
  • equation 5 can be obtained from the inequality evaluation of equation 2.
  • ⁇ _min is the minimum wavelength within the transmission band.
  • FIG. 2 is a diagram showing a configuration example of the receiving system 100.
  • the receiving system 100 includes an antenna device 10 and a receiving device 20.
  • the antenna device 10 is an array antenna.
  • the antenna device 10 includes at least three or more antenna elements 11.
  • the number of antenna elements 11 included in the antenna device 10 is expressed as N (N is an integer of 3 or more).
  • the N antenna elements 11 are arranged so as not to satisfy the above-mentioned linear dependency generation condition (Equation 4) of the steering vector.
  • the antenna elements 11 may be arranged in a one-dimensional array or a two-dimensional array.
  • the receiving device 20 includes N converters 201 (201_1 to 201_N), N FF filters 202 (202_1 to 202_N), a combiner 203, an output estimation unit 204, and a filter coefficient acquisition unit 205.
  • N is the same value as the number of antenna elements 11 that the antenna device 10 has. In this way, it is desirable that the number of conversion units 201 and FF filters 202 is the same as the number of antenna elements 11. If some functions are not used, they do not necessarily have to be the same number. Note that, in the following description, the configurations common to the N devices with the same name will be described with symbols such as "_1" omitted. For example, regarding the conversion unit, it is written as “conversion unit 201” instead of “conversion unit 201_1”.
  • the conversion unit 201 samples the electrical signal converted by the antenna element 11 of the antenna device 10. Specifically, the details are as follows. The conversion unit 201 performs analog-to-digital conversion on the electrical signal converted by the antenna element 11. The conversion unit 201 then performs frequency conversion on the digital signal obtained by analog-to-digital conversion. Note that other configurations (modifications) may be adopted for the conversion unit 201. For example, the conversion unit 201 may be configured to perform only analog-to-digital conversion. For example, the conversion unit 201 may be configured to perform frequency conversion on an analog signal and then perform analog-to-digital conversion.
  • the FF filter 202 performs waveform manipulation on the signal sampled by the conversion unit 201.
  • the FF filter 202 outputs the waveform-manipulated signal to the synthesizer 203.
  • the synthesizer 203 synthesizes the N signals whose waveforms have been manipulated by the FF filter 202.
  • the output estimation unit 204 may tentatively determine the output of the combiner 203 based on the signals combined by the combiner 203.
  • the output estimation unit 204 may calculate a desired response by using the signal combined by the combiner 203 and the training signal.
  • the desired response may be, for example, a symbol included in a desired wave signal received by the antenna device 10.
  • the filter coefficient acquisition unit 205 adaptively acquires the filter coefficients of the N FF filters 202.
  • the filter coefficient acquisition unit 205 may acquire the filter coefficients by calculation, for example, or may acquire the filter coefficients based on a preset lookup table.
  • the filter coefficient acquisition unit 205 may be configured to include, for example, an error calculation unit and an adaptive algorithm unit.
  • the error calculation unit calculates the error between the output of the equalizer and the desired response.
  • the adaptive algorithm section adaptively updates the filter coefficients based on the error calculated by the error calculation section, and optimizes the filter coefficients based on a criterion such as least square error.
  • the adaptive algorithm includes means for recursively calculating filter coefficients, such as the LMS (least mean square) method, the RLS (recursive least square) method, and the APA (Affine projection algorithm) method. It also includes algorithms derived from these.
  • the output estimation section 204 and the filter coefficient acquisition section 205 are each configured using a processor such as a CPU and a memory.
  • the output estimation unit 204 and the filter coefficient acquisition unit 205 operate when a processor reads and executes a program stored in a storage device.
  • the program may be recorded on a computer-readable recording medium.
  • the computer-readable recording medium is a non-temporary storage medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or other portable medium, or a hard disk or other storage device built into a computer system.
  • the program may be transmitted via a telecommunications line.
  • a part or all of the operations of the output estimation section 204 and the filter coefficient acquisition section 205 may be realized using hardware including an electronic circuit using an LSI, an ASIC, a PLD, an FPGA, or the like, for example.
  • the receiving device 20 may further include an FB filter and a DPLL (digital PLL), as shown in Non-Patent Documents 1 and 2.
  • a DPLL digital PLL
  • the configuration of the antenna device 10 will be described in detail.
  • the arrangement of the antenna elements 11 in the antenna device 10 does not create a set of linearly dependent arrival directions whose steering vectors completely match. Therefore, there are FF filter coefficients whose gains in any two directions do not match. That is, independent control in two directions is possible, such as making the reception gain of unnecessary waves smaller than that of desired waves, regardless of the combination of arrival directions. As a result, the degree of freedom in controlling the adaptive algorithm increases, and it becomes possible to effectively suppress unnecessary waves and extract desired waves.
  • the first arrangement is characterized in that there is at least one combination of spacings between antenna elements 11 that are irrational ratios.
  • the antenna elements 11 may be arranged so as to satisfy Equation 6 below.
  • the installation interval of the antenna elements 11 is an approximate value of an irrational number ratio, so a value that sufficiently approximates an irrational number may be used.
  • d_1 is greater than or equal to 1/2 of the minimum wavelength within the transmission band and less than the minimum wavelength. Further, at least one of d_2 to d_(N-1) is not an integral multiple of d_1.
  • the antenna element 11 is configured such that any n (n is 2 or more and less than (N-1)) satisfies the following formula 7 and that d_n and kd_1 are different (k is a natural number). is placed.
  • both p_n' and p_m' are (2d_(N-1)).
  • p_n' and p_m' are (2d_(N-1)).
  • 3 and 4 are diagrams showing an overview of computer simulation.
  • a linear array is assumed, and a direct wave (desired wave) is incident from a direction perpendicular to the arrangement direction of the linear array.
  • a multipath wave delayed by 100 symbols is made incident from the ⁇ direction ( ⁇ is a value between 0 and ⁇ /2).
  • the equalizer has the same configuration as shown in FIG. 2, and extracts direct waves and removes multipath waves based on the training sequence.
  • Equalization performance is evaluated by evaluating the mean square error (MSE) between the desired signal and the output value of the equalizer.
  • MSE mean square error
  • the table shown in FIG. 5 is the specifications of the transmission signal in the computer simulation.
  • the table shown in FIG. 6 is the specifications of the antenna arrangement for comparative evaluation by computer simulation.
  • the aperture diameter of the array antenna is set to 1 m in common to all four patterns of arrangement. Equal spacing is a common array to compare and has a linear dependence on the steering vector.
  • Figure 8 shows the simulation results.
  • the horizontal axis represents the arrival direction of the delayed wave
  • the vertical axis represents the mean square error with respect to the desired signal (the signal indicated by the desired wave). It can be said that the smaller the mean squared error, the more effectively interference caused by unnecessary waves can be removed.
  • the results show that in the equally spaced arrangement, the interference wave suppression performance deteriorates after the angle (8.7 degrees) at which spatial aliasing occurs at the highest frequency of the band (30 kHz).
  • the first to third arrangements achieve better performance than the equally spaced arrangement at arrival angles of 10 degrees or more, and the equalization performance is improved.
  • wavelengths often differ by more than twice the length within a frequency band.
  • the above problem becomes more serious in underwater communications because the relationship between directions of arrival that causes spatial aliasing differs for each wavelength within the band, making it difficult to remove unnecessary waves from all directions.
  • the accuracy of equalization processing for the received signal can be improved by using the antenna device 10 that adopts one of the first arrangement, second arrangement, and third arrangement as described above. becomes possible.
  • the antenna elements 11 in the antenna device 10 are arranged one-dimensionally, but the antenna elements 11 may be arranged two-dimensionally. In this case, the beam is scanned two-dimensionally, and it works effectively against interference waves from two directions: elevation and azimuth.
  • FIG. 9 is a diagram showing a first specific example of a two-dimensional arrangement.
  • FIG. 10 is a diagram showing a second specific example of two-dimensional arrangement.
  • the antenna elements 11 are arranged in one row along the first axis and in one row along the second axis.
  • the first axis and the second axis are orthogonal.
  • the antenna elements 11 are arranged in an L-shape.
  • a cross array or other two-dimensional array may be used.
  • each of the first axis and the second axis may not be arranged in one row, but may be arranged in a plurality of rows.
  • the antenna elements 11 are arranged in a rectangular shape along the first axis and the second axis.
  • the arrangement interval d_(1,1) to d_(1,N-1) does not satisfy the condition of Equation 4, and the arrangement interval d_(2,1) to d_(2 , N-1) does not satisfy the condition of Equation 4.
  • any of the first to third arrangements may be used.
  • the set of arrangement intervals d_(2,1) to d_(2,N-1) may be any one of the first arrangement to the third arrangement.
  • the arrangement pattern from d_(1,1) to d_(1,N-1) and the arrangement pattern from d_(2,1) to d_(2,N-1) are the same.
  • the set from d_(1,1) to d_(1,N-1) is the first arrangement, and the set from d_(2,1) to d_(2,N-1) is also the first arrangement. may be configured respectively.
  • the set from d_(1,1) to d_(1,N-1) is the first arrangement, and the set from d_(2,1) to d_(2,N-1) is the second arrangement. Each may be configured as an arrangement.
  • the set from d_(1,1) to d_(1,N-1) does not satisfy the condition of Equation 4, and the set from d_(2,1) to d_(2,N-1) It may be configured to satisfy the condition of Expression 4. Furthermore, the set of arrangement intervals d_(1,1) to d_(1,N-1) satisfies the condition of formula 4, and the set of arrangement intervals d_(2,1) to d_(2,N-1) satisfies the condition of formula 4. The configuration may be such that condition 4 is not satisfied.
  • the set of the above-mentioned arrangement intervals d_(1,1) to d_(1,N-1) does not satisfy the condition of Equation 4, and the set of the arrangement intervals d_(2,1) to d_(2,N-1) -1) may also have lower performance than a configuration that does not satisfy the condition of Equation 4, but it is possible to improve the performance at least more than the conventional configuration.
  • FIG. 7 they may be arranged in a two-dimensional mesh grid.
  • the arrangement shown in FIGS. 9 and 10 does not have a linearly dependent set of steering vectors in any two-dimensional direction. Therefore, it is possible to improve equalization performance.
  • the first axis and the second axis are orthogonal, but they do not necessarily need to be orthogonal.
  • the present invention can be applied to techniques for receiving radio waves and sound waves (including ultrasonic waves).

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Computational Linguistics (AREA)
  • Health & Medical Sciences (AREA)
  • Audiology, Speech & Language Pathology (AREA)
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Abstract

One aspect of the present invention is an antenna device comprising N antenna elements (where N is an integer of 3 or more) that receive sound waves or radio waves, wherein the antenna elements are each disposed in such a position that a steering vector corresponding to an incident angle θ of one sound wave or radio wave and a steering vector corresponding to an incident angle θ_d ( where θ_d is -π/2 to +π/2) of another sound wave or radio wave are not linearly dependent.

Description

アンテナ装置antenna device
　本発明は、電波や音波（超音波を含む）を用いて伝送される無線信号を受信する技術に関する。 The present invention relates to a technology for receiving wireless signals transmitted using radio waves and sound waves (including ultrasonic waves).
　比帯域が数十％を超える広帯域の水中音響通信システムでは、海面や海底からのマルチパス波によって生じるISI（Inter-symbol-interference）や他システムからの干渉波によって生じるCCI（co-channel interference）によって波形が歪みやすい。そのため、このような水中音響通信システムでは、受信機で等化処理を行う必要がある。このような等化処理は、水中での音響通信特有のものではなく、電波を用いた通信でも行われる。 In broadband underwater acoustic communication systems with a fractional bandwidth of more than several tens of percent, ISI (Inter-symbol-interference) caused by multipath waves from the sea surface or the bottom of the ocean, and CCI (co-channel interference) caused by interference waves from other systems. The waveform is easily distorted. Therefore, in such an underwater acoustic communication system, it is necessary to perform equalization processing in the receiver. Such equalization processing is not unique to underwater acoustic communication, but is also performed in communication using radio waves.
　なお、以下の説明では“アンテナ”という文言を、電波を受信するための構成に限らず、音波（超音波を含む）を受信するための構成も含む概念を表す文言として用いる。また、以下の説明では、マルチパス波及び干渉波のように、受信対象となっている所望波（直接波）の受信に影響を及ぼす可能性のある波を「不要波」という。 Note that in the following description, the term "antenna" is used to represent a concept that is not limited to a configuration for receiving radio waves, but also includes a configuration for receiving sound waves (including ultrasonic waves). Furthermore, in the following description, waves such as multipath waves and interference waves that may affect the reception of the desired wave (direct wave) to be received are referred to as "unnecessary waves."
　アレーアンテナを用いた信号処理では、時空間領域の双方を活用して不要波の除去を行うことができる。そのため、一般的な時間領域の等化器に比べて、アレーアンテナを用いた信号処理では補償効果が高い。したがって、水中通信ではアレーアンテナを用いた信号処理が用いられることがある。例えば、アレーアンテナ個別のＦＩＲ（Finite impulse response）フィルターとＦＢ（Feed-back）フィルターとを備え、フィルター係数をＬＭＳ（Least mean square）法やＲＬＳ（Recursive least square）法等の最適化アルゴリズムを用いて最適化を行う方法がある。（例えば、非特許文献１や非特許文献２を参照）。フィルター係数の制御によって、周波数―空間方向の利得を制御することができる。そして、周波数―空間方向の利得を制御することで所望波を抽出し、不要波を除去することができる。 In signal processing using an array antenna, unnecessary waves can be removed by utilizing both the spatio-temporal domain. Therefore, compared to a general time-domain equalizer, signal processing using an array antenna has a higher compensation effect. Therefore, signal processing using an array antenna is sometimes used in underwater communications. For example, an array antenna is equipped with an FIR (Finite Impulse Response) filter and an FB (Feed-back) filter for each array antenna, and the filter coefficients are determined using an optimization algorithm such as the LMS (Least Mean Square) method or the RLS (Recursive Least Square) method. There is a method to perform optimization. (For example, see Non-Patent Document 1 and Non-Patent Document 2). By controlling the filter coefficients, the gain in the frequency-spatial direction can be controlled. By controlling the gain in the frequency-spatial direction, desired waves can be extracted and unnecessary waves can be removed.
　空間領域における不要波の抑圧性能は、根本的にはアレーアンテナの形状で決まる。アレーアンテナの開口の大きさが空間分解能を決定するため、一般的には開口を広くした方が不要波の抑圧性能が向上する。換言すれば、アレーアンテナ全体の大きさが大きいほど、所望波と角度差が小さい不要波をより有効に抑圧できる。 The suppression performance of unnecessary waves in the spatial domain is fundamentally determined by the shape of the array antenna. Since the size of the aperture of the array antenna determines the spatial resolution, generally speaking, the wider the aperture, the better the unnecessary wave suppression performance. In other words, the larger the overall size of the array antenna, the more effectively it is possible to suppress unnecessary waves that have a small angular difference from the desired wave.
　ただし、伝送周波数帯域において空間エイリアシングが発生しないように、帯域の最も短い波長（最も高い周波数）の半波長以下の間隔でアンテナ素子を配列する必要がある。空間エイリアシングとは、アンテナ素子間の位相差を用いることで信号の到来方向をベクトルで表現したときに、一次従属な到来方向の組み合わせが生じることである。以下の説明では、信号の到来方向を示すベクトルを「ステアリングベクトル」という。 However, in order to prevent spatial aliasing from occurring in the transmission frequency band, it is necessary to arrange the antenna elements at intervals of half a wavelength or less of the shortest wavelength (highest frequency) in the band. Spatial aliasing means that when the direction of arrival of a signal is expressed as a vector by using the phase difference between antenna elements, a combination of linearly dependent directions of arrival occurs. In the following description, a vector indicating the direction of arrival of a signal will be referred to as a "steering vector."
　しかしながら、装置の制約等が原因となり、角度分解能に応じたアレーの開口幅に応じて、半波長以下の間隔でアンテナ素子を配置できない場合がある。この場合、配列パターンによっては伝送周波数帯域内に空間エイリアシングが生じる可能性がある。具体的には、以下のようなケースがある。 However, due to limitations of the device, antenna elements may not be arranged at intervals of half a wavelength or less depending on the aperture width of the array depending on the angular resolution. In this case, spatial aliasing may occur within the transmission frequency band depending on the arrangement pattern. Specifically, there are the following cases.
　所望波と不要波との到来方向を示すステアリングベクトルが一次従属のとき、等化器が不要波に対して空間的にヌル形成しようとすると、所望波方向にもヌル形成されてしまう。一方で、所望波方向にメインローブを向けると、不要波の到来方向にもメインローブが向けられてしまい、不要波を抑圧できない。そのため、どのような適応アルゴリズムを用いてフィルター係数を最適化したとしても、不要波の抑圧も所望波の抽出も効果的に行うことができず、等化の性能が低下してしまう。 When the steering vectors indicating the direction of arrival of the desired wave and the unwanted wave are linearly dependent, if the equalizer attempts to spatially form a null for the unwanted wave, a null will also be formed in the direction of the desired wave. On the other hand, if the main lobe is directed in the direction of the desired wave, the main lobe will also be directed in the direction in which unnecessary waves arrive, making it impossible to suppress unnecessary waves. Therefore, no matter what kind of adaptive algorithm is used to optimize the filter coefficients, neither unnecessary waves nor desired waves can be effectively suppressed, and the equalization performance deteriorates.
　上記事情に鑑み、本発明は、受信対象となる電波や音波（超音波を含む）である所望波を受信する際に行われる等化処理の性能を向上可能な技術の提供を目的としている。 In view of the above circumstances, the present invention aims to provide a technology that can improve the performance of equalization processing performed when receiving desired waves that are radio waves or sound waves (including ultrasonic waves) to be received.
　本発明の一態様は、音波又は電波を受信するＮ個（Ｎは３以上の整数）のアンテナ素子を備え、前記アンテナ素子は、ある音波又は電波の入射角度θに対応するステアリングベクトルと、他の音波又は電波の入射角度θ＿ｄ（θ＿ｄは－π／２～＋π／２）に対応するステアリングベクトルと、が一次従属にならない位置に配置されている、アンテナ装置である。 One aspect of the present invention includes N antenna elements (N is an integer of 3 or more) that receive sound waves or radio waves, and the antenna elements each have a steering vector corresponding to an incident angle θ of a certain sound wave or radio wave, and a steering vector corresponding to an incident angle θ of a certain sound wave or radio wave. This is an antenna device in which the steering vector corresponding to the incident angle θ_d (θ_d is −π/2 to +π/2) of the sound wave or radio wave is located at a position that is not linearly dependent.
　本発明により、受信対象となる電波や音波（超音波を含む）である所望波を受信する際に行われる等化処理の性能を向上させることが可能となる。 According to the present invention, it is possible to improve the performance of equalization processing performed when receiving desired waves that are radio waves or sound waves (including ultrasonic waves) to be received.
アレーアンテナとして構成されるアンテナ装置１０におけるアンテナ素子１１の配列の具体例を示す図である。FIG. 3 is a diagram showing a specific example of the arrangement of antenna elements 11 in the antenna device 10 configured as an array antenna. 受信システム１００の構成例を示す図である。1 is a diagram showing a configuration example of a receiving system 100. FIG. 計算機シミュレーションの概要を示す図である。It is a figure showing an outline of computer simulation. 計算機シミュレーションの概要を示す図である。It is a figure showing an outline of computer simulation. 計算機シミュレーションにおける伝送信号の諸元である。These are the specifications of the transmission signal in computer simulation. 計算機シミュレーションで比較評価を行うアンテナ配置の諸元である。These are the specifications of antenna placement for comparative evaluation using computer simulation. 配列の比較を示す図である。FIG. 3 shows a comparison of sequences. シミュレーション結果である。These are simulation results. 二次元的な配置の第一具体例を示す図である。FIG. 3 is a diagram showing a first specific example of a two-dimensional arrangement. 二次元的な配置の第二具体例を示す図である。It is a figure which shows the second specific example of two-dimensional arrangement|positioning.
　［ステアリングベクトルの一次従属性の発生条件］
　アレーアンテナとして構成されるアンテナ装置において、空間エイリアシングによってステアリングベクトルの一次従属性が発生する条件について説明する。図１は、アレーアンテナとして構成されるアンテナ装置１０におけるアンテナ素子１１の配列の具体例を示す図である。アンテナ装置１０は、少なくとも３つのアンテナ素子１１を備える。アンテナ素子１１は、電波や音波（超音波を含む）等の波を受けて、波に応じた電気信号を生成する。 [Conditions for occurrence of linear dependence of steering vector]
In an antenna device configured as an array antenna, conditions under which linear dependence of steering vectors occurs due to spatial aliasing will be described. FIG. 1 is a diagram showing a specific example of the arrangement of antenna elements 11 in an antenna device 10 configured as an array antenna. The antenna device 10 includes at least three antenna elements 11. The antenna element 11 receives waves such as radio waves and sound waves (including ultrasonic waves) and generates electrical signals corresponding to the waves.
　アンテナ素子１１は、一次元又は二次元に配置される。このような配置により、アンテナ装置１０はアレーアンテナとして構成される。図１の例では、一次元のライン上にＮ個のアンテナ素子１１が配置されている。すなわち、図１の例におけるアンテナ装置１０は線形アレーとして構成されている。各アンテナ素子１１には、＃０～＃Ｎ－１の符号が与えられている。 The antenna element 11 is arranged one-dimensionally or two-dimensionally. With this arrangement, the antenna device 10 is configured as an array antenna. In the example of FIG. 1, N antenna elements 11 are arranged on a one-dimensional line. That is, the antenna device 10 in the example of FIG. 1 is configured as a linear array. Each antenna element 11 is given a code from #0 to #N-1.
　＃０のアンテナ素子１１を基準点として、＃ｉのアンテナ素子はｄ＿ｉ離れた位置に配置される。なお、“Ａ＿Ｂ”という記載は、“Ａ”の右下に添え字として“Ｂ”が配置された記載を示す。受信波（所望波及び不要波を含む）は、角度θ（θは－π／２～＋π／２）のいずれかの方向から入射するものと仮定する。 With the #0 antenna element 11 as a reference point, the #i antenna element is placed d_i away. Note that the description "A_B" indicates a description in which "B" is placed as a subscript at the lower right of "A". It is assumed that the received waves (including desired waves and unnecessary waves) are incident from any direction at an angle θ (θ is −π/2 to +π/2).
　入射角度θに対応するステアリングベクトルと、他の到来方向θ＿ｄ（θ＿ｄは－π／２～＋π／２）に対応するステアリングベクトルと、が一次従属である場合、以下の条件式（式１）が満たされる。 When the steering vector corresponding to the incident angle θ and the steering vector corresponding to another arrival direction θ_d (θ_d is −π/2 to +π/2) are linearly dependent, the following conditional expression (Equation 1) is satisfied. It is filled.
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
　ここで、λは伝送帯域内のいずれかの周波数に対応する波長である。伝送帯域とは、受信対象となっている所望波（直接波）の伝送において使用されることが想定されている帯域を示す。α＿ｎ（ｎ＝０，…，Ｎ－１）は０を除く整数である。各α＿ｎの数値範囲は以下の式２で示される。 Here, λ is a wavelength corresponding to any frequency within the transmission band. The transmission band refers to a band that is assumed to be used in transmitting a desired wave (direct wave) to be received. α_n (n=0,...,N-1) is an integer excluding 0. The numerical range of each α_n is shown by Equation 2 below.
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000002
　式１を整理することによって、以下の式３を得ることができる。 By rearranging Equation 1, the following Equation 3 can be obtained.
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000003
　ｍ及びｎは、それぞれ１以上（Ｎ－１）以下の整数の集合である。ｍとｎとが異なる全てのｍ及びｎのペアについて、以下に示す式４を満たすα＿１，…，α＿（Ｎ－１）の組が少なくとも一つ存在する場合、入射角度θと別の方向に１つ以上の一次従属な到来方向が生じる。言い換えれば、α＿１～α＿（Ｎ－１）が式３を満たす組となる場合には、入射角度θと別の方向に１つ以上の一次従属な到来方向が生じる。 m and n are each a set of integers from 1 to (N-1). For all pairs of m and n where m and n are different, if there is at least one set of α_1, ..., α_(N-1) that satisfies Equation 4 shown below, in a direction different from the incident angle θ. One or more linearly dependent directions of arrival occur. In other words, when α_1 to α_(N-1) form a set that satisfies Expression 3, one or more linearly dependent arrival directions occur in a direction different from the incident angle θ.
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000004
　［ステアリングベクトルの一次従属性が発生しない条件］
　次に、ステアリングベクトルの一次従属性が発生しない条件について説明する。伝送帯域内でステアリングベクトルの一次従属性が発生しない条件は、－π／２～＋π／２の任意のθについて、上述した式４を満たさないｄ＿ｎ及びｄ＿ｍの組が少なくとも一つ存在することである。 [Conditions under which linear dependence of steering vectors does not occur]
Next, conditions under which linear dependence of steering vectors does not occur will be explained. The condition that linear dependence of steering vectors does not occur within the transmission band is that for any θ between -π/2 and +π/2, there exists at least one pair of d_n and d_m that does not satisfy Equation 4 above. be.
　例えば、ｄ＿ｎ及びｄ＿ｍの組の少なくとも一つの素子間隔の比（ｄ＿ｎ’／ｄ＿ｍ’）が無理数であれば、θの値によらずに式４の条件を満たす整数比が存在しない。そのため、このように素子間隔の比が無理数であれば、ステアリングベクトルの一次従属性は、全ての角度及び全ての波長について発生しない。このような条件におけるアンテナ素子１１の配置を、第一配置と呼ぶ。 For example, if the ratio of the element spacing (d_n'/d_m') of at least one of the set of d_n and d_m is an irrational number, there is no integer ratio that satisfies the condition of Equation 4 regardless of the value of θ. Therefore, if the ratio of the element spacings is an irrational number, linear dependence of the steering vector does not occur for all angles and all wavelengths. The arrangement of the antenna element 11 under such conditions is called a first arrangement.
　例えば、ｄ＿１を伝送帯域内の最小波長の１／２以上、且つ、最小波長未満の値とする。この場合、伝送帯域内の全ての波長について、α＿１は＋１か－１しか取りえない。ｄ＿２をｄ＿１の整数倍でないように配置すれば、ステアリングベクトルの一次従属性は発生しない。このような条件におけるアンテナ素子１１の配置を、第二配置と呼ぶ。
　例えば、式２の不等式評価から以下の式５を得ることができる。 For example, let d_1 be a value that is 1/2 or more of the minimum wavelength within the transmission band and less than the minimum wavelength. In this case, α_1 can only take +1 or −1 for all wavelengths within the transmission band. If d_2 is arranged so that it is not an integral multiple of d_1, linear dependence of the steering vectors will not occur. The arrangement of the antenna element 11 under such conditions is called a second arrangement.
For example, the following equation 5 can be obtained from the inequality evaluation of equation 2.
Figure JPOXMLDOC01-appb-M000005
Figure JPOXMLDOC01-appb-M000005
　ここで、λ＿ｍｉｎは伝送帯域内における最小の波長である。式５より以下の事象を導きだすことができる。ｄ＿ｎとｄ＿ｍとの比を、互いに素な数ｐ＿ｎ及びｐ＿ｍを用いて、ｄ＿ｎ／ｄ＿ｍ＝ｐ＿ｎ／ｐ＿ｍと表した場合、ｐ＿ｎ及びｐ＿ｍのいずれもが（２ｄ＿（Ｎ－１））／λ＿ｍｉｎ　よりも大きければ、式４を満たす整数α＿ｎ及びα＿ｍの組は存在しない。すなわち、上述した条件を満たすことにより、ステアリングベクトルの一次従属性は発生しない。このような条件におけるアンテナ素子１１の配置を、第三配置と呼ぶ。 Here, λ_min is the minimum wavelength within the transmission band. The following phenomenon can be derived from Equation 5. When the ratio of d_n and d_m is expressed as d_n/d_m=p_n/p_m using mutually prime numbers p_n and p_m, both p_n and p_m are less than (2d_(N-1))/λ_min. If it is large, there is no set of integers α_n and α_m that satisfies Equation 4. That is, by satisfying the above-mentioned conditions, linear dependence of steering vectors does not occur. The arrangement of the antenna element 11 under such conditions is called a third arrangement.
　［受信システムの構成］
　次に、アンテナ装置１０を含む受信システム１００について説明する。図２は、受信システム１００の構成例を示す図である。受信システム１００は、アンテナ装置１０及び受信装置２０を備える。 [Receiving system configuration]
Next, a receiving system 100 including the antenna device 10 will be explained. FIG. 2 is a diagram showing a configuration example of the receiving system 100. The receiving system 100 includes an antenna device 10 and a receiving device 20.
　アンテナ装置１０はアレーアンテナである。アンテナ装置１０は、少なくとも３以上のアンテナ素子１１を備える。以下の説明では、アンテナ装置１０が備えるアンテナ素子１１の数をＮ（Ｎは３以上の整数）として表す。アンテナ装置１０において、Ｎ個のアンテナ素子１１は、上述したステアリングベクトルの一次従属発生条件（式４）を満たさないように配置される。アンテナ素子１１の配置は、一次元のアレー配置であってもよいし、二次元のアレー配置であってもよい。 The antenna device 10 is an array antenna. The antenna device 10 includes at least three or more antenna elements 11. In the following description, the number of antenna elements 11 included in the antenna device 10 is expressed as N (N is an integer of 3 or more). In the antenna device 10, the N antenna elements 11 are arranged so as not to satisfy the above-mentioned linear dependency generation condition (Equation 4) of the steering vector. The antenna elements 11 may be arranged in a one-dimensional array or a two-dimensional array.
　受信装置２０は、Ｎ台の変換部２０１（２０１＿１～２０１＿Ｎ）、Ｎ台のＦＦフィルター２０２（２０２＿１～２０２＿Ｎ）、合成器２０３、出力推定部２０４及びフィルター係数取得部２０５を備える。Ｎは、アンテナ装置１０が有するアンテナ素子１１の数と同じ値である。このように、変換部２０１及びＦＦフィルター２０２は、それぞれアンテナ素子１１と同数設けられることが望ましい。一部の機能を使用しないのであれば、必ずしも全てが同数である必要はない。なお、以下の説明では、Ｎ台の同名の装置に共通する構成に関しては、“＿１”等の符号を省略して記載する。例えば、変換部に関しては、“変換部２０１＿１”ではなく、“変換部２０１”と記載する。 The receiving device 20 includes N converters 201 (201_1 to 201_N), N FF filters 202 (202_1 to 202_N), a combiner 203, an output estimation unit 204, and a filter coefficient acquisition unit 205. N is the same value as the number of antenna elements 11 that the antenna device 10 has. In this way, it is desirable that the number of conversion units 201 and FF filters 202 is the same as the number of antenna elements 11. If some functions are not used, they do not necessarily have to be the same number. Note that, in the following description, the configurations common to the N devices with the same name will be described with symbols such as "_1" omitted. For example, regarding the conversion unit, it is written as “conversion unit 201” instead of “conversion unit 201_1”.
　変換部２０１は、アンテナ装置１０のアンテナ素子１１によって変換された電気信号のサンプリングを行う。具体的には以下の通りである。変換部２０１は、アンテナ素子１１によって変換された電気信号に対し、アナログデジタル変換を行う。そして、変換部２０１は、アナログデジタル変換によって得られたデジタル信号について、周波数変換を行う。なお、変換部２０１には他の構成（変形例）が採用されてもよい。例えば、変換部２０１は、アナログデジタル変換のみを行うように構成されてもよい。例えば、変換部２０１は、アナログ信号に対して周波数変換を行い、その後にアナログデジタル変換を行うように構成されてもよい。 The conversion unit 201 samples the electrical signal converted by the antenna element 11 of the antenna device 10. Specifically, the details are as follows. The conversion unit 201 performs analog-to-digital conversion on the electrical signal converted by the antenna element 11. The conversion unit 201 then performs frequency conversion on the digital signal obtained by analog-to-digital conversion. Note that other configurations (modifications) may be adopted for the conversion unit 201. For example, the conversion unit 201 may be configured to perform only analog-to-digital conversion. For example, the conversion unit 201 may be configured to perform frequency conversion on an analog signal and then perform analog-to-digital conversion.
　ＦＦフィルター２０２は、変換部２０１によってサンプリングされた信号に対して波形操作を行う。ＦＦフィルター２０２は、波形操作された信号を合成器２０３に出力する。 The FF filter 202 performs waveform manipulation on the signal sampled by the conversion unit 201. The FF filter 202 outputs the waveform-manipulated signal to the synthesizer 203.
　合成器２０３は、ＦＦフィルター２０２によって波形操作が行われた後のＮ個の信号を合成する。 The synthesizer 203 synthesizes the N signals whose waveforms have been manipulated by the FF filter 202.
　出力推定部２０４は、合成器２０３によって合成された後の信号に基づいて、合成器２０３の出力を仮判定してもよい。出力推定部２０４は、合成器２０３によって合成された後の信号とトレーニング信号とを用いることで、所望の応答を計算してもよい。所望の応答とは、例えばアンテナ装置１０によって受信された所望波の信号に含まれるシンボルであってもよい。 The output estimation unit 204 may tentatively determine the output of the combiner 203 based on the signals combined by the combiner 203. The output estimation unit 204 may calculate a desired response by using the signal combined by the combiner 203 and the training signal. The desired response may be, for example, a symbol included in a desired wave signal received by the antenna device 10.
　フィルター係数取得部２０５は、Ｎ個のＦＦフィルター２０２のフィルター係数を適応的に取得する。フィルター係数取得部２０５は、例えば計算によってフィルター係数を取得してもよいし、予め設定されたルックアップテーブルに基づいてフィルター係数を取得してもよい。 The filter coefficient acquisition unit 205 adaptively acquires the filter coefficients of the N FF filters 202. The filter coefficient acquisition unit 205 may acquire the filter coefficients by calculation, for example, or may acquire the filter coefficients based on a preset lookup table.
　フィルター係数取得部２０５は、例えば誤差計算部及び適応アルゴリズム部を含むように構成されてもよい。誤差計算部は、等化装置の出力と所望の応答との誤差を計算する。適応アルゴリズム部は、誤差計算部によって計算された誤差に基づいてフィルター係数を適応的に更新し、最小二乗誤差などの規範に基づき最適化する。適応アルゴリズムとは、LMS(least mean square)法、RLS（recursive least square）法、APA（Affine projection algorithm）法など再帰的にフィルタ係数を算出する手段を含む。また、これらの派生したアルゴリズムも含む。 The filter coefficient acquisition unit 205 may be configured to include, for example, an error calculation unit and an adaptive algorithm unit. The error calculation unit calculates the error between the output of the equalizer and the desired response. The adaptive algorithm section adaptively updates the filter coefficients based on the error calculated by the error calculation section, and optimizes the filter coefficients based on a criterion such as least square error. The adaptive algorithm includes means for recursively calculating filter coefficients, such as the LMS (least mean square) method, the RLS (recursive least square) method, and the APA (Affine projection algorithm) method. It also includes algorithms derived from these.
　出力推定部２０４及びフィルター係数取得部２０５は、それぞれＣＰＵ等のプロセッサーやメモリを用いて構成される。出力推定部２０４及びフィルター係数取得部２０５は、記憶装置に記憶されたプログラムをプロセッサーが読み出して実行することによって動作する。プログラムは、コンピューター読み取り可能な記録媒体に記録されてもよい。コンピューター読み取り可能な記録媒体とは、例えばフレキシブルディスク、光磁気ディスク、ＲＯＭ、ＣＤ－ＲＯＭ等の可搬媒体、コンピューターシステムに内蔵されるハードディスク等の記憶装置などの非一時的な記憶媒体である。プログラムは、電気通信回線を介して送信されてもよい。出力推定部２０４及びフィルター係数取得部２０５の動作の一部又は全部は、例えば、ＬＳＩ、ＡＳＩＣ、ＰＬＤ又はＦＰＧＡ等を用いた電子回路を含むハードウェアを用いて実現されてもよい。 The output estimation section 204 and the filter coefficient acquisition section 205 are each configured using a processor such as a CPU and a memory. The output estimation unit 204 and the filter coefficient acquisition unit 205 operate when a processor reads and executes a program stored in a storage device. The program may be recorded on a computer-readable recording medium. The computer-readable recording medium is a non-temporary storage medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or other portable medium, or a hard disk or other storage device built into a computer system. The program may be transmitted via a telecommunications line. A part or all of the operations of the output estimation section 204 and the filter coefficient acquisition section 205 may be realized using hardware including an electronic circuit using an LSI, an ASIC, a PLD, an FPGA, or the like, for example.
　なお、受信装置２０は、非特許文献１及び２に示されるように、ＦＢフィルターとＤＰＬＬ（デジタルＰＬＬ）をさらに備えてもよい。 Note that the receiving device 20 may further include an FB filter and a DPLL (digital PLL), as shown in Non-Patent Documents 1 and 2.
　［アンテナ装置の詳細］
　次に、アンテナ装置１０の構成について詳細に説明する。上述したように、アンテナ装置１０におけるアンテナ素子１１の配置では、ステアリングベクトルが完全に一致する一次従属な到来方向の組が生じない。したがって、任意の２方向の利得が一致しないＦＦフィルター係数が存在する。すなわち、到来方向の組み合わせによらず、不要波の受信利得を所望波よりも小さくするといった２方向の独立制御が可能である。その結果、適応アルゴリズムにおける制御の自由度が高まり、不要波の抑圧と所望波の抽出とを効果的に行うことが可能となる。 [Details of antenna device]
Next, the configuration of the antenna device 10 will be described in detail. As described above, the arrangement of the antenna elements 11 in the antenna device 10 does not create a set of linearly dependent arrival directions whose steering vectors completely match. Therefore, there are FF filter coefficients whose gains in any two directions do not match. That is, independent control in two directions is possible, such as making the reception gain of unnecessary waves smaller than that of desired waves, regardless of the combination of arrival directions. As a result, the degree of freedom in controlling the adaptive algorithm increases, and it becomes possible to effectively suppress unnecessary waves and extract desired waves.
　上述したように、アンテナ素子１１の配列の具体例として、第一配置、第二配置及び第三配置がある。それぞれの具体例について説明する。 As described above, specific examples of the arrangement of the antenna elements 11 include the first arrangement, the second arrangement, and the third arrangement. Specific examples of each will be explained.
　［第一配置］
　第一配置では、無理数比となるアンテナ素子１１の間隔の組み合わせが少なくとも一つ存在することを特徴とする。例えば、以下の式６を満たすようにアンテナ素子１１が配列されてもよい。 [First arrangement]
The first arrangement is characterized in that there is at least one combination of spacings between antenna elements 11 that are irrational ratios. For example, the antenna elements 11 may be arranged so as to satisfy Equation 6 below.
Figure JPOXMLDOC01-appb-M000006
Figure JPOXMLDOC01-appb-M000006
　式６において、ｄ＿ｎ、ｄ＿ｍは、図１に示されるとおりである。Ｍ＿ｏは無理数である。ｎ及びｍは互いに異なる１以上（Ｎ－１）以下の整数である。式６の条件によれば、ｄ＿ｎ／ｄ＿ｍ＝１／Ｍ＿ｏである。このように、式６を満たすようにアンテナ素子１１が配列されることによって、ｄ＿ｎ／ｄ＿ｍが無理数比となる。そのため、式４を満たさない。その結果、常にステアリングベクトルの一次従属が発生しない。 In Equation 6, d_n and d_m are as shown in FIG. M_o is an irrational number. n and m are mutually different integers of 1 or more (N-1) or less. According to the condition of Equation 6, d_n/d_m=1/M_o. In this way, by arranging the antenna elements 11 so as to satisfy Expression 6, d_n/d_m becomes an irrational ratio. Therefore, formula 4 is not satisfied. As a result, linear dependence of the steering vector does not always occur.
　なお、実運用上、アンテナ素子１１の設置間隔は無理数比の近似値となることから、無理数を十分に近似した値が用いられてもよい。 Note that in actual operation, the installation interval of the antenna elements 11 is an approximate value of an irrational number ratio, so a value that sufficiently approximates an irrational number may be used.
［第二配置］
　第二配置では、ｄ＿１は伝送帯域内の最小波長の１／２以上、且つ、最少波長未満とする。また、ｄ＿２からｄ＿（Ｎ－１）のうちの少なくとも一つが、ｄ＿１の整数倍ではない。つまり、以下の式７を満たし、且つ、ｄ＿ｎとｋｄ＿１とが異なる（ｋは自然数）、という条件を、いずれかのｎ（ｎは２以上（Ｎ－１）未満）で満たすようにアンテナ素子１１が配置される。 [Second arrangement]
In the second arrangement, d_1 is greater than or equal to 1/2 of the minimum wavelength within the transmission band and less than the minimum wavelength. Further, at least one of d_2 to d_(N-1) is not an integral multiple of d_1. In other words, the antenna element 11 is configured such that any n (n is 2 or more and less than (N-1)) satisfies the following formula 7 and that d_n and kd_1 are different (k is a natural number). is placed.
Figure JPOXMLDOC01-appb-M000007
Figure JPOXMLDOC01-appb-M000007
［第三配置］
　第三配置では、ｄ＿ｎとｄ＿ｍとの組の少なくとも一つのアンテナ素子間隔の比を互いに素な因数ｐ＿ｎ’／ｐ＿ｍ’で表したときに、ｐ＿ｎ’もｐ＿ｍ’も（２ｄ＿（Ｎ－１））／λ＿ｍｉｎ　よりも大きい値となる配置である。つまり、ｄ＿ｎ＝γＰ＿ｎ，ｄ＿ｍ＝γＰ＿ｍ　、γは実数、Ｐ＿ｎ，Ｐ＿ｍ　は互いに素な整数であり、以下の式８の条件を満たす、という条件を、いずれかのｎ，ｍ（ｎとｍは１以上（Ｎ－１）以下）の組で満たすようにアンテナ素子１１が配列される。 [Third arrangement]
In the third arrangement, when the ratio of the spacing between at least one antenna element of the set d_n and d_m is expressed by a relatively prime factor p_n'/p_m', both p_n' and p_m' are (2d_(N-1)). This is an arrangement where the value is larger than /λ_min. In other words, d_n=γP_n, d_m=γP_m, γ is a real number, P_n, P_m are mutually prime integers, and the condition of formula 8 below is satisfied. The antenna elements 11 are arranged so as to satisfy the following (N-1) or less pairs.
Figure JPOXMLDOC01-appb-M000008
Figure JPOXMLDOC01-appb-M000008
［実施例］
　次に、上述した第一配置、第二配置及び第三配置の各アンテナ装置１０を用いた受信システム１００について、一般的な等間隔配置のアンテナ装置を用いた受信システムと効果について計算機シミュレーションした結果を示す。 [Example]
Next, the results of a computer simulation regarding the effects of the reception system 100 using the antenna devices 10 in the first, second, and third configurations described above and the effects of a general receiving system using antenna devices arranged at equal intervals will be described. shows.
　図３及び図４は、計算機シミュレーションの概要を示す図である。本シミュレーションでは、線形アレーを仮定し、線形アレーの配列方向と直交した方向から直接波（所望波）を入射させる。さらに、１００シンボル遅延したマルチパス波をθ（θは０からπ／２の間の値）方向から入射させる。等化装置は図２に示される構成と同一であり、トレーニング系列を基に直接波を抽出し、マルチパス波を除去する。所望信号と等化装置の出力値との平均二乗誤差（ＭＳＥ；mean square error）を評価することで等化性能を評価する。 3 and 4 are diagrams showing an overview of computer simulation. In this simulation, a linear array is assumed, and a direct wave (desired wave) is incident from a direction perpendicular to the arrangement direction of the linear array. Furthermore, a multipath wave delayed by 100 symbols is made incident from the θ direction (θ is a value between 0 and π/2). The equalizer has the same configuration as shown in FIG. 2, and extracts direct waves and removes multipath waves based on the training sequence. Equalization performance is evaluated by evaluating the mean square error (MSE) between the desired signal and the output value of the equalizer.
　図５に示される表は、計算機シミュレーションにおける伝送信号の諸元である。図６に示される表は、計算機シミュレーションで比較評価を行うアンテナ配置の諸元である。アレーアンテナの開口径は角度分解能をそろえるため、４パターンの配置すべてに共通して１ｍとする。等間隔配置は、比較対象となる一般的な配列であり、ステアリングベクトルの一次従属を持つ。第一配置から第三配置は、上述した配列構成である。第一配置では、ｄ＿２／ｄ＿１がルート２（２の１／２乗）になる。第二配置では、ｄ＿１が１波長（０．０５ｍ）であり、ｄ＿２／ｄ＿１＝１０．５である。第三配列では、本シミュレーションでは The table shown in FIG. 5 is the specifications of the transmission signal in the computer simulation. The table shown in FIG. 6 is the specifications of the antenna arrangement for comparative evaluation by computer simulation. In order to make the angular resolution uniform, the aperture diameter of the array antenna is set to 1 m in common to all four patterns of arrangement. Equal spacing is a common array to compare and has a linear dependence on the steering vector. The first arrangement to the third arrangement are the arrangement configurations described above. In the first arrangement, d_2/d_1 becomes root 2 (2 to the 1/2 power). In the second arrangement, d_1 is one wavelength (0.05 m) and d_2/d_1=10.5. In the third array, in this simulation
Figure JPOXMLDOC01-appb-M000009
Figure JPOXMLDOC01-appb-M000009
　に対して、ｄ＿２／ｄ＿１＝４３／４１となる比で配列している。配列の比較を図７に示す。 , they are arranged at a ratio of d_2/d_1=43/41. A comparison of the sequences is shown in Figure 7.
　図８はシミュレーション結果である。横軸は遅延波の到来方向、縦軸は所望信号（所望波が示す信号）との平均二乗誤差である。平均二乗誤差が小さいほど不要波による干渉を効果的に除去できていると言える。結果より、等間隔配置では、帯域の最高周波数（３０　ｋＨｚ）において空間エイリアシングが生じる角度（８．７度）以降は干渉波の抑圧性能が低下している。他方で、第一配置～第三配置では、１０度以上の到来角で等間隔配置よりも良い性能が達成できており、等化性能が向上していることがわかる。 Figure 8 shows the simulation results. The horizontal axis represents the arrival direction of the delayed wave, and the vertical axis represents the mean square error with respect to the desired signal (the signal indicated by the desired wave). It can be said that the smaller the mean squared error, the more effectively interference caused by unnecessary waves can be removed. The results show that in the equally spaced arrangement, the interference wave suppression performance deteriorates after the angle (8.7 degrees) at which spatial aliasing occurs at the highest frequency of the band (30 kHz). On the other hand, it can be seen that the first to third arrangements achieve better performance than the equally spaced arrangement at arrival angles of 10 degrees or more, and the equalization performance is improved.
　以上の評価結果より、第一配置～第三配置によって等化性能の向上効果が得られることを示した。
　このように、第一配置、第二配置及び第三配置のいずれかが採用されたアンテナ装置１０を用いることによって、受信された信号に対する等化処理の精度を向上させることが可能となる。 From the above evaluation results, it was shown that the effect of improving equalization performance can be obtained by the first to third arrangements.
In this way, by using the antenna device 10 in which one of the first arrangement, the second arrangement, and the third arrangement is adopted, it is possible to improve the accuracy of equalization processing for received signals.
　特に、広帯域の水中通信では、周波数帯域内で波長の長さが２倍以上異なることがしばしばある。帯域内の波長ごとに空間エイリアシングが生じる到来方向の関係性が異なることから、水中通信では上記の問題がより深刻化し、あらゆる方向からの不要波の除去が難しくなる。このような状況においても、上述したように第一配置、第二配置及び第三配置のいずれかが採用されたアンテナ装置１０を用いることによって、受信された信号に対する等化処理の精度を向上させることが可能となる。 In particular, in broadband underwater communications, wavelengths often differ by more than twice the length within a frequency band. The above problem becomes more serious in underwater communications because the relationship between directions of arrival that causes spatial aliasing differs for each wavelength within the band, making it difficult to remove unnecessary waves from all directions. Even in such a situation, the accuracy of equalization processing for the received signal can be improved by using the antenna device 10 that adopts one of the first arrangement, second arrangement, and third arrangement as described above. becomes possible.
　以下、アンテナ装置１０の変形例について説明する。上述した説明では、いずれもアンテナ装置１０におけるアンテナ素子１１の配置は一次元的な配置であったが、二次元的にアンテナ素子１１が配置されてもよい。この場合、二次元的にビームを走査し、仰角・方位角方向の２つからの干渉波に対して有効に働く。 Hereinafter, a modification of the antenna device 10 will be described. In the above description, the antenna elements 11 in the antenna device 10 are arranged one-dimensionally, but the antenna elements 11 may be arranged two-dimensionally. In this case, the beam is scanned two-dimensionally, and it works effectively against interference waves from two directions: elevation and azimuth.
　図９は二次元的な配置の第一具体例を示す図である。図１０は二次元的な配置の第二具体例を示す図である。図９では、アンテナ素子１１が、第一軸に沿って１列、第二軸に沿って１列、それぞれ配置されている。第一軸と第二軸とは直交している。具体的には、図９ではアンテナ素子１１がＬ字型に配置されている。Ｌ字以外にも十字配列や他の二次元配列でもよい。また、第一軸と第二軸とはそれぞれ１列ではなく、複数の列が配置されてもよい。図１０では、アンテナ素子１１が第一軸及び第二軸に沿って矩形状に配置されている。 FIG. 9 is a diagram showing a first specific example of a two-dimensional arrangement. FIG. 10 is a diagram showing a second specific example of two-dimensional arrangement. In FIG. 9, the antenna elements 11 are arranged in one row along the first axis and in one row along the second axis. The first axis and the second axis are orthogonal. Specifically, in FIG. 9, the antenna elements 11 are arranged in an L-shape. In addition to the L-shape, a cross array or other two-dimensional array may be used. Further, each of the first axis and the second axis may not be arranged in one row, but may be arranged in a plurality of rows. In FIG. 10, the antenna elements 11 are arranged in a rectangular shape along the first axis and the second axis.
　図９及び図１０の配置例では、配置間隔ｄ＿（１，１）からｄ＿（１，Ｎ－１）の組が式４の条件を満たさず、且つ、ｄ＿（２，１）からｄ＿（２，Ｎ－１）の組が式４の条件を満たさない。配置間隔ｄ＿（１，１）からｄ＿（１，Ｎ－１）の組に関しては、第一配置～第三配置のいずれであってもよい。また、配置間隔ｄ＿（２，１）～ｄ＿（２，Ｎ－１）の組に関しても、第一配置～第三配置のいずれであってもよい。このとき、配置間隔ｄ＿（１，１）からｄ＿（１，Ｎ－１）の配置パターンと、ｄ＿（２，１）からｄ＿（２，Ｎ－１）の配置パターンとは、同じであってもよいし、異なっていてもよい。例えば、配置間隔ｄ＿（１，１）からｄ＿（１，Ｎ－１）の組が第一配置であり、ｄ＿（２，１）からｄ＿（２，Ｎ－１）の組も第一配置としてそれぞれ構成されてもよい。また、例えば、配置間隔ｄ＿（１，１）からｄ＿（１，Ｎ－１）の組が第一配置であり、ｄ＿（２，１）からｄ＿（２，Ｎ－１）の組が第二配置としてそれぞれ構成されてもよい。 In the arrangement examples shown in FIGS. 9 and 10, the arrangement interval d_(1,1) to d_(1,N-1) does not satisfy the condition of Equation 4, and the arrangement interval d_(2,1) to d_(2 , N-1) does not satisfy the condition of Equation 4. Regarding the set of arrangement intervals d_(1,1) to d_(1,N-1), any of the first to third arrangements may be used. Furthermore, the set of arrangement intervals d_(2,1) to d_(2,N-1) may be any one of the first arrangement to the third arrangement. At this time, the arrangement pattern from d_(1,1) to d_(1,N-1) and the arrangement pattern from d_(2,1) to d_(2,N-1) are the same. It may be different or it may be different. For example, the set from d_(1,1) to d_(1,N-1) is the first arrangement, and the set from d_(2,1) to d_(2,N-1) is also the first arrangement. may be configured respectively. Also, for example, the set from d_(1,1) to d_(1,N-1) is the first arrangement, and the set from d_(2,1) to d_(2,N-1) is the second arrangement. Each may be configured as an arrangement.
　また、配置間隔ｄ＿（１，１）からｄ＿（１，Ｎ－１）の組が式４の条件を満たさず、且つ、ｄ＿（２，１）からｄ＿（２，Ｎ－１）の組が式４の条件を満たすように構成されてもよい。また、配置間隔ｄ＿（１，１）からｄ＿（１，Ｎ－１）の組が式４の条件を満たし、且つ、ｄ＿（２，１）からｄ＿（２，Ｎ－１）の組が式４の条件を満たさないように構成されてもよい。このような構成では、上述した配置間隔ｄ＿（１，１）からｄ＿（１，Ｎ－１）の組が式４の条件を満たさず、且つ、ｄ＿（２，１）からｄ＿（２，Ｎ－１）の組も式４の条件を満たさないように構成されたものに比べて性能は低い可能性があるが、少なくとも従来の構成よりは性能を向上させることが可能である。 Also, the set from d_(1,1) to d_(1,N-1) does not satisfy the condition of Equation 4, and the set from d_(2,1) to d_(2,N-1) It may be configured to satisfy the condition of Expression 4. Furthermore, the set of arrangement intervals d_(1,1) to d_(1,N-1) satisfies the condition of formula 4, and the set of arrangement intervals d_(2,1) to d_(2,N-1) satisfies the condition of formula 4. The configuration may be such that condition 4 is not satisfied. In such a configuration, the set of the above-mentioned arrangement intervals d_(1,1) to d_(1,N-1) does not satisfy the condition of Equation 4, and the set of the arrangement intervals d_(2,1) to d_(2,N-1) -1) may also have lower performance than a configuration that does not satisfy the condition of Equation 4, but it is possible to improve the performance at least more than the conventional configuration.
　また、図７のように、二次元上にメッシュグリッドに配列されてもよい。図９や図１０に示された配置であれば、二次元方向のいずれの方向にも一次従属な組のステアリングベクトルを持たない。そのため、等化性能を向上させることが可能となる。
　図９及び図１０の例では、第一軸と第二軸とは直交していたが、必ずしも直交していなくてもよい。 Further, as shown in FIG. 7, they may be arranged in a two-dimensional mesh grid. The arrangement shown in FIGS. 9 and 10 does not have a linearly dependent set of steering vectors in any two-dimensional direction. Therefore, it is possible to improve equalization performance.
In the examples of FIGS. 9 and 10, the first axis and the second axis are orthogonal, but they do not necessarily need to be orthogonal.
　以上、この発明の実施形態について図面を参照して詳述してきたが、具体的な構成はこの実施形態に限られるものではなく、この発明の要旨を逸脱しない範囲の設計等も含まれる。 Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and includes designs within the scope of the gist of the present invention.
　本発明は、電波や音波（超音波を含む）を受信する技術に適用することができる。 The present invention can be applied to techniques for receiving radio waves and sound waves (including ultrasonic waves).
１０…アンテナ装置、１１…アンテナ素子，２０…受信装置（等化装置）、２０１…変換部、２０２…ＦＦフィルター、２０３…合成器、２０４…出力推定部、２０５…フィルター係数取得部 DESCRIPTION OF SYMBOLS 10... Antenna device, 11... Antenna element, 20... Receiving device (equalization device), 201... Conversion section, 202... FF filter, 203... Combiner, 204... Output estimation section, 205... Filter coefficient acquisition section

Claims (1)

  1. 　音波又は電波を受信するＮ個（Ｎは３以上の整数）のアンテナ素子を備え、
    　前記アンテナ素子は、ある音波又は電波の入射角度θに対応するステアリングベクトルと、他の音波又は電波の入射角度θ＿ｄ（θ＿ｄは－π／２～＋π／２）に対応するステアリングベクトルと、が一次従属にならない位置に配置されている、アンテナ装置。     Equipped with N antenna elements (N is an integer of 3 or more) that receive sound waves or radio waves,
    The antenna element has a steering vector corresponding to an incident angle θ of a certain sound wave or radio wave, and a steering vector corresponding to an incident angle θ_d (θ_d is −π/2 to +π/2) of another sound wave or radio wave, which are linear. An antenna device located in a non-subordinate position.
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