JP2005252844A - Receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a circuit of an adaptive array antenna device used for a receiver in radio communication. <P>SOLUTION: The receiving apparatus comprises n antenna elements 101-1 to 101-n; phase shifters 102-1 to 102-n which are connected to the antenna elements; a multiplexer 14 for multiplexing signals, of which the phases are adjusted by the phase shifter; an A/D converter 105 for converting the multiplexed signals into digital signals; a Fourier transformation means 107 for transforming the digital signals from the signals of the time domain into those of the frequency domain, wherein the phase sifter is controlled by the frequency characteristics obtained by Fourier transformation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a receiving apparatus that performs wireless communication, and more particularly, to a technique for adjusting a beam forming direction in a receiving apparatus having a plurality of antennas.

  In recent years, wireless communication has become popular. For example, in wireless LAN communication and the like, ultra-high-speed data communication technology, for example, as a transmission band, broadband wireless transmission of several tens to several hundreds of MHz is required. It has become. When performing broadband wireless communication, it is known that communication performance deteriorates because frequency selective distortion due to multipath is likely to occur. In order to prevent performance degradation due to multipath distortion, a technology that makes it possible to select and receive the azimuth angle of signals using multiple antennas, and to combine the received signals of multiple antennas with optimized weighting Antenna devices have been developed. Here, an antenna apparatus using a plurality of antenna elements is generally referred to as an array antenna.

  In order to control the arrival azimuth angle by the array antenna, it is only necessary to adjust and / or synthesize either or both of the phase and amplitude of each received signal for a plurality of antenna elements. As a result, it is possible to control the azimuth (direction) of the received signal. Such a technique for controlling the direction of the received signal is generally called a beam forming technique. Beam forming technology is an analog beam forming technology that adjusts the phase and amplitude of the signals received by multiple antenna elements in the state of analog signals, and digitally combines the received signals of the multiple antenna elements. It can be divided into a digital beam forming technique that adjusts and combines the phase and amplitude using processing.

  As an example of an analog beam forming technique, a technique using a phased array antenna is known. This phased array antenna is an antenna device characterized in that a beam is formed by adjusting the phase of a signal received by an antenna element.

  Moreover, an adaptive array antenna is known as an example of a digital beam forming technique. An adaptive array antenna generally has a configuration shown in FIG. FIG. 9 shows an example when the number of antenna elements is n. Here, the receiving circuit for each antenna element is called a branch. The signals received by the antenna elements 201-1 to 201-n are BPF (band pass filter) 207-1 to n, mixers 208-1 to n, and LPF (low pass filter) 209 for each branch. A signal in a desired band is selected through −1 to n and converted into a baseband signal.

The baseband signal is sampled by the A / D converters 205-1 to 20-n for each branch and converted into a digital signal. With respect to the digitized reception signal, the phase and amplitude are adjusted by the phase and amplitude adjustment units 202-1 to 202-n. The adjustment amount between the phase and the amplitude is given by the output from the signal processing unit 203. The signals of the respective branches whose phase and amplitude are changed are combined by the multiplexer 204 and demodulated by the receiving circuit 206. The signal processing unit 203 obtains an optimum value of the adjustment amount between the phase and the amplitude based on the information on the phase and amplitude of the received signal of each branch, the combined array output signal 210, information from the demodulation circuit, and the like. As the control algorithm, RLS (Recursive Least-Squares) or MMSE (Minimum Mean Square Error) is used (for example, see Non-Patent Document 1).
"MMSE adaptive array using guard section in OFDM", Hori, Kikuma, Inagaki, IEICE Transactions B, Vol. J85-B, No. 9, pp. 1608-1615, September 2002.

  However, since the above-described phased array antenna adjusts only the phase, it requires a great number of antenna elements to control the desired beam formation in detail. Therefore, the apparatus becomes large-scale and is suitable for the sectorization of the base station system. On the other hand, in order to reduce the number of antenna elements and reduce the size or to finely control the beam shape, it is necessary to arrange the antenna elements with a narrow interval between the antenna elements. In such a case, there is a problem that mutual coupling occurs between the antenna elements. Further, since the antenna element is also coupled to the housing, coupling different from the theoretical and ideal cases occurs. The distortion of the beam shape due to these couplings is difficult to calibrate because the information on the amplitude and phase of the received signal at each antenna element cannot be obtained by the analog beam forming method that combines in the analog signal. .

  Further, according to the above adaptive array antenna, the calculation of MMSE and RLS for obtaining the optimum values of phase and amplitude adjustment amounts is very complicated, and a large-scale digital circuit or digital signal processing circuit DSP (Digital Signal Processor) Therefore, it is difficult to reduce the size of the apparatus. In addition, in order to make each antenna signal a baseband signal, not only the BPF (bandpass filter), mixer and LPF (lowpass filter) shown in FIG. 9 but also RF circuits including power amplifiers are required for the number of antennas. There is also a problem that the circuit scale increases.

  As described above, although wireless communication devices that prevent deterioration of multipath distortion have been developed by analog beam forming technology and digital beam forming technology, the number of antenna elements is large, and the mutual coupling between antenna elements and the case is difficult. There are problems in reducing the size of the receiving device, such as the fact that the influence is large, the scale of the RF circuit tends to increase, and the optimization control circuit for beam formation is complicated. For this reason, the above-described technology is not suitable as a wireless device for a mobile terminal in which downsizing of the device is an essential requirement.

  An object of the present invention is to provide a receiving apparatus suitable for a mobile terminal that can prevent deterioration in communication quality due to multipath distortion or the like.

  In order to achieve the above object, a receiving apparatus of the present invention includes a plurality of antenna elements, a circuit that adjusts the phase of a carrier wave of a signal received by the antenna element for each branch of the plurality of antennas, and a phase adjustment of each branch. A circuit for synthesizing the received signal, a circuit for detecting the frequency characteristics of the synthesized received signal, a control circuit for determining and detecting the detected frequency characteristics and changing the phase data for beam formation, and data for phase adjustment And a D / A circuit that converts the phase adjustment data into an analog voltage and applies a control voltage to the phase adjustment circuit.

  The receiving apparatus according to the present invention combines the received signals of a plurality of antennas with analog signals, determines the frequency characteristics using the spectral flatness, and can perform beam forming with a simple and small-sized control circuit. Thus, multipath distortion can be prevented. In addition, a beam that takes into account the distortion of the entire device is used by using the correction coefficient estimated from the measurement results for the mutual coupling, the coupling with the case, and the arrangement state of the elements, which are problems when miniaturizing the antenna. Formation is possible.

  When the beam forming method of the present invention is used, it is possible to form a beam from which distortion due to coupling or the like is removed by using a coupling matrix including coupling with a casing and an arrangement state of a phase shifter and the like. It is also possible to correct individual differences between the receiving devices. Further, according to the above method, even when the asymmetric antenna arrangement or the number of antennas is small, it is possible to easily form a null or a beam only by simple phase adjustment.

  Furthermore, according to the present invention, when the communication method is the OFDM (Orthogonal Frequency Division Multiplexing) method, it is possible to reduce the circuit scale of the receiving device by sharing the FFT for reception and the FFT for frequency determination. It is.

  1) Perform beam control using spectral flatness, and 2) Obtain spectral flatness by a method using one threshold and use it for beam control. 3) Obtain spectral flatness by a method using a plurality of threshold values and use it for beam control. 4) Spectral flatness is obtained by changing the weighting coefficient of data and pilot when the communication system is the OFDM communication system and the subcarriers for data and pilot are separated and used for beam control. 5) Spectral flatness is obtained by calculating the spectral flatness using only a plurality of pilot subcarriers when the communication method is OFDM and a plurality of pilot subcarriers are arranged at equal intervals in frequency. It is characterized by being used for.

  The frequency characteristic determination circuit has a function of calculating signal flatness by calculating signal power with respect to frequency components and performing a comparison operation using average power and a threshold value, and can be realized with a very simple circuit. Furthermore, when obtaining the spectral flatness, by providing a plurality of threshold values and a plurality of weighting factors, a more accurate spectral flatness can be obtained, and the resistance to multipath distortion can be further increased. In addition, when the communication scheme is the OFDM scheme and the data transmission subcarrier and the pilot subcarrier are separated, the weighting coefficient of the data subcarrier and the pilot subcarrier is changed when determining the spectral flatness. The communication quality can be further improved by increasing the pilot weight and obtaining the spectral flatness. In addition, when the communication method is the OFDM method and the pilot subcarriers are arranged at equal intervals, the number of computations (the number of stages of the comparison circuit) can be obtained by using only the pilot carrier when obtaining the spectral flatness in the frequency characteristic determination circuit. ) Can be reduced, and the circuit scale can be reduced.

  In the memory of the present invention, a plurality of received beam shape data having different directivity directions and shapes are stored, ranked for each shape, and by using a beam switching means using priority order, more appropriate. Since beam forming can be selectively switched at high speed, it is possible to cope with dynamic changes such as fading.

  As described above, according to one aspect of the present invention, a plurality of antenna elements that receive radio signals, and a phase shifter that adjusts the phase of a carrier wave of a received signal in each of the plurality of antenna elements for each antenna element; A multiplexer that synthesizes the received signal whose phase is adjusted by the phase shifter; an analog / digital converter that converts the synthesized signal synthesized by the multiplexer into a digital signal; and There is provided a receiving apparatus having Fourier transform means for converting a domain signal into a frequency domain signal, and a control means for controlling the phase shifter based on the frequency characteristic obtained by the Fourier transform means. The phase shifter may be provided for at least one antenna element of the plurality of antenna elements, or may be provided for all antenna elements of the plurality of antenna elements. good.

  When the control means outputs a phase adjustment amount (antenna weight) to the phase shifter and gives a certain beam shape (coupling between the antenna elements and the surroundings of the antenna elements and the antenna elements) And determining the influence of electromagnetic coupling due to the arrangement state of the antenna element (with the influence of coupling with the antenna element), and forming a desired beam shape so as to reduce the influence based on the determination. To do.

  According to another aspect of the present invention, a plurality of antenna elements that receive a radio signal, a phase shifter that adjusts a phase of a carrier wave of a reception signal in each of the plurality of antenna elements for each antenna element, and the phase shift Based on the output of the multiplexer that synthesizes the received signal phase-adjusted by the multiplexer, the analog / digital converter that converts the synthesized signal synthesized by the multiplexer into a digital signal, and the analog / digital converter A receiving circuit that performs signal processing of the received signal, and a Fourier transform unit that converts a digital signal obtained as an output of the analog / digital converter from a time domain signal to a frequency domain signal And a frequency characteristic determination unit for determining the flatness of the signal power in the frequency spectrum obtained by the Fourier transform means and determining the flatness. If the receiving device is provided with a control means on the basis of the flatness of the determination result performs control related to adjustment by the phase shifter. It is also possible to provide a program for causing a computer to execute the function of the device.

  According to the present invention, it is possible to provide a receiving apparatus that can prevent deterioration in communication quality due to multipath distortion, and that can perform simple antenna control and miniaturization suitable for mobile communication.

  In this specification, the received beam shape (or beam shape) means the directivity pattern of the array antenna, that is, the received electric field strength with respect to each direction of the array antenna.

  Hereinafter, a wireless communication receiver according to an embodiment of the present invention will be described with reference to the drawings. First, the configuration of the receiving device will be described. FIG. 1 is a diagram illustrating an example of the overall configuration of a receiving apparatus according to the present embodiment, and is a diagram for explaining a control flow in the receiving apparatus.

  As shown in FIG. 1, the receiving apparatus according to the present embodiment has n antenna elements (the number of branches), n antenna elements 101-1 to 101-n and each antenna element 101-1. Phase shifters 102-1 to n connected to n, D / A converters 103-1 to 103-n connected to control terminals of the phase shifters 102-1 to n, and phase shifter 102-1. 1 includes a multiplexer 104 in which output terminals 1 to n are combined, a BPF 111 connected to the multiplexer 104, a mixer 112, an LPF 113, an A / D converter 105, and a receiving circuit 106. Yes. The output of the A / D converter 105 is also input to the FFT 107, and different outputs from the memory 110 are sent to the D / A converter 103- through the frequency characteristic determination circuit 108, the beam switching control circuit 109, and the memory 110. 1 to n are input.

  In the receiving apparatus, the signals received by the antenna elements 101-1 to 101-n respectively give control voltages to the D / A converters 103-1 to 103-n to the phase shifters 102-1 to 102-n. Thus, the phase is adjusted for each branch, synthesized by the multiplexer 104, and becomes the array output signal 114. The memory 110 stores a data set corresponding to the phase difference of each branch, that is, phase adjustment amount (phase shift amount) data of each branch. The array output signal 114 is converted from the RF band to the baseband band through the BPF 111, the mixer 112, and the LPF 113, and converted into a digital signal by the A / D converter 105. The digitized received signal is converted from a time domain signal to a frequency domain signal in an FFT (Fast Fourier Transform) circuit 107 and divided into signal components for each frequency component. The frequency characteristic determination circuit 108 determines the spectral flatness (the definition and calculation method of the spectral flatness will be described later in the embodiment) from the frequency component signal of the FFT circuit 107.

  The beam switching control circuit 109 determines whether to change the received beam shape from the current received beam shape based on the spectral flatness determined by the frequency characteristic determining circuit 108, and changes the current received beam shape from the current received beam shape. In this case, the phase shift amount data of the beam shape to be changed stored in the memory 110 is output to the D / A converters 103-1 to 103-n.

  With the configuration of the receiving apparatus shown in FIG. 1, the scale of the RF circuit can be made smaller than the RF circuit in the general receiving apparatus shown in FIG. 9, and multipath distortion is prevented by beam forming control with a simple circuit configuration. be able to.

  When the communication system is the OFDM communication system, since the receiving circuit includes an FFT, the FFT circuit 107 shown in FIG. 1 can be shared with the FFT of the OFDM receiving circuit. It can be reduced, and beam control is possible with a simple configuration.

  Next, a detailed example of each functional block will be described with reference to FIG. First, data stored in the memory will be described. In FIG. 2, in order to simplify the description, the case where the number of branches is four will be described as an example. The memory 110 stores a phase adjustment amount necessary for forming a plurality of different beam shapes. That is, a control signal (control voltage) for controlling the phase is applied to each of the phase shifters 102-1 to 102-1 to D / A circuits 103-1 to 103-4. Furthermore, the phase shift amount of the branch # 1 to be controlled to the phase shift amount of the branch # 4 is given to the respective D / A circuits 103-1 to 103-4. For example, if the phase control amount is 30 ° and the control voltage from the D / A converter that is output to the phase shifter is 5V, data for outputting an output voltage of 5V from the D / A converter is obtained. , Stored in corresponding memory locations in the matrix of beam shapes and branch phase shifts. This value is determined, for example, in the process of manufacturing the device, and is stored in, for example, an EPROM so that it can be adjusted as needed when adjustment is required. It should be noted that the value stored in the memory may be changed as appropriate so that it can be corrected later.

  By scanning the beam switching control circuit 108, the data supplied to each branch can be changed. The scanning procedure will be described later with reference to FIG.

  An example of the beam shape will be described with reference to FIG. 3A to 3E are diagrams showing examples of five different beam shapes (beam shapes # 1 to # 5) shown in FIG. As shown in FIG. 2, in order to form the beam shape # 1, the phase shift amount data data1-1 of the branch # 1, the phase shift amount data data 1-2 of the branch # 2, and the phase shift of the branch # 3 The amount data data1-3 and the phase shift amount data data1-4 of the branch # 4 are necessary. That is, assuming that the number of antenna elements (the number of branches) is n, when forming i beam shapes, it is necessary to store n (columns) × i (rows) data in the memory. Further, in the memory 110, for example, when it is desired to delay the phase of the carrier wave by 90 degrees, a control voltage necessary for delaying 90 degrees by the phase shifters 102-1 to 10-4 is supplied to the D / A converter 103-1. Data converted into values necessary to be output in .about.4 are stored. The memory 110 is one of the beam shapes # 1 to # 4 selected by the beam selection signal for selecting each of the branches # 1 to # 4 from the beam switching control circuit 109, and each branch has Corresponding data is output to the D / A converters 103-1 to 103-4, respectively. The D / A converters 103-1 to 103-4 convert the data into control voltages and supply them to the phase shifters 102-1 to 102-4.

  Next, a method for generating a beam forming phase adjustment amount will be described. The amount of phase adjustment (phase shift amount) given to the received signal of each antenna element corresponding to the desired beam shape is the number of antenna elements, the arrangement of antenna elements, and the beam shape of each antenna element (single orientation of the antenna element) ) And a theoretical value can be obtained. Next, a technique for determining the amount of phase shift in consideration of the actual antenna state, such as mutual coupling between antenna elements accompanying the downsizing of the antenna array, the influence of the casing, and the non-uniformity of the elements will be described. The beam shape of an array antenna has a beam shape different from the ideal state even if a certain amount of phase shift is given due to mutual coupling between antenna elements, element arrangement, element non-uniformity, influence of the case, etc. It will be. Therefore, first, a coefficient indicating the deviation between the actual beam shape of the antenna and the ideal state is defined as Y, and when the number of antenna elements is n, Y is defined as an n × n matrix of Equation (1).

本発明は、アレーアンテナの理想的な状態と実際のビーム形状のずれを、係数Ｙとして求め、このＹを補正するように位相調整量を決定し、より理想的なビーム形状得ることが可能となる。ここでｎ素子のアレーアンテナのウェイトベクトル、すなわち、各アンテナ素子の位相調整量Ｗ_mを

The present invention obtains a deviation between the ideal state of the array antenna and the actual beam shape as a coefficient Y, determines the phase adjustment amount so as to correct this Y, and can obtain a more ideal beam shape. Become. Here, the weight vector of the n-element array antenna, that is, the phase adjustment amount W _m of each antenna element is expressed by

とおく。このときＷ_mの要素Ｗ_miはｉ番目のアンテナ素子のウェイト（位相調整量）である。また、方向ベクトルＶ_kを

far. At this time, the element W _{mi of} W _m is the weight (phase adjustment amount) of the i-th antenna element. Also, the direction vector V _k

とおく。ここで、Ｖ_kは角度θ_kの方向から信号が入射したときの素子間結合等のない理想的な状態での各アンテナ素子の受信信号であり、Ｖ_kの要素Ｖ_kiはθ_kの方向から信号が入射したときのｉ番目のアンテナ素子における理想的な受信信号である。

far. Here, V _k is the received signal of each antenna element in an ideal state without linkages such element when the incident signal from the direction of angle theta _k, the direction of the elements V _ki is theta _k of V _k This is an ideal received signal at the i-th antenna element when the signal enters from.

From the above, the array signal output (114 in FIG. 1) out _mk when one wave arrives from the direction of the angle θ _k when the antenna weight W _m is given is

と表すことができる。ここで、

It can be expressed as. here,

は、行列又はベクトルの転置を意味する。

Means the transpose of a matrix or vector.

  Next, a procedure for obtaining Y using the above relational expression and further obtaining an antenna weight for generating a desired beam shape will be described.

  FIG. 5 is a flowchart showing a procedure for obtaining the antenna weight W 'necessary for correcting the mutual coupling and performing beam forming. The corrected antenna weight W 'means an adjustment amount of the amplitude and phase shift of the antenna element. In the antenna configuration according to the present embodiment, the antenna weight is only for phase shift adjustment, and when changing the weight, only the phase shift amount is changed (n is the number of antenna elements).

As shown in FIG. 5, first, processing is started in step S1. In step S2, the equation ^{_{out mk = W m T YV k}} , antenna weights W _m is varied antenna element number n times, i.e., the weight W _1, ... W _m ..., suitably given W _n, to each of the weights On the other hand, the direction in which the signal is incident on the array antenna is changed n times, and the array output signal out _mk (m = 1,..., N, k = 1,..., N) is measured. That is, for n W _m (m = 1,..., N), the signal incident direction is changed n times, that is, n V _k (k = 1,..., N) are given, and n ² Measure out _mk (m = 1, ..., n, k = 1, ..., n). This measurement result is

と表すことができる。ここで、Ｗ、Ｖ、outはそれぞれ、

It can be expressed as. Here, W, V, and out are respectively

である。（２）式から、

It is. From equation (2)

となり、Ｗ、Ｖ、outは実際に設定した値、あるいは測定した値であるため、Ｙが決定する。尚、ステップＳ２におけるウェイトＷ_mをｎ個変化させ、アレーアンテナにｎ個の方向から信号を入射しｎ²個のアレー出力信号を測定し、Ｙを決定したが、この場合、最低ｎ²個必要であることを意味し、求めるＹの精度を高めるために、Ｗ_mの個数、信号の入射方向を変更する回数を増やし、最小二乗法等を用いてＹ（ｎ×ｎ行列）を求めるのが好ましい。以上より、Ｙを求めることができる（ステップＳ３）。

Since W, V, and out are actually set values or measured values, Y is determined. Incidentally, the weight W _m in Step S2 is the n change, incident signals of n directions to measure the n ² array output signals to the array antenna has been determined Y, in this case, a minimum of ^two n In order to improve the accuracy of Y to be obtained, the number of W _{m and} the number of times of changing the incident direction of the signal are increased, and Y (n × n matrix) is obtained by using the least square method or the like. Is preferred. From the above, Y can be obtained (step S3).

  Next, in step S4, the antenna weight is determined using Y obtained in step S3. Y is a distortion coefficient depending on the installation state of the mutual coupling between the housing and the antenna, the phase shifter, the combiner, etc., that is, a coefficient indicating a deviation from the ideal state. Therefore, in order to obtain the array output signal out ′ from which the deviation has been removed, it may be obtained as a new antenna weight W ′ that allows the deviation. Therefore,

となる。ただしＹ^-1はＹの逆行列である。

It becomes. Y ^-1 is an inverse matrix of Y.

  Since the distortion-corrected antenna weight W 'has an amplitude term and a phase term, an array antenna with only phase adjustment gives only the phase term. As a result, when the difference from the desired beam shape is large, W ′ may be slightly changed to correct the beam shape closer to the desired beam shape. (Step S4).

Next, regarding the processing content in step S4, in particular, in an array antenna that adjusts only the amount of phase shift, a beam shape having a null (a point where the received electric field strength takes a value of “0” or “0”) in a certain direction A method for obtaining a phase adjustment amount (weight) necessary for forming the above will be described in more detail with reference to FIG. 6 as an example of the embodiment. Incidentally, in the processing shown in FIG. 6, a description will be given of a case of obtaining a beam shape having a null in the direction of a certain orientation theta _k.

First, the process starts in step S11, in step S12, providing an initial value W ₁ of the weight W _i. The initial value W ₁ is given as i = 1 (i is a counter indicating the number of times the extreme value problem is calculated). Here, the initial value W ₁ is an arbitrary value. However, the convergence becomes faster by appropriately selecting the initial value. For example, when it is desired to obtain a beam shape having a null in the direction of θ _k , it is assumed that an initial weight W ₁ and a certain phase perturbation Φ are given (step S13). A phase perturbation Φ

すると、アレー出力信号out'_1kは以下の式になる。

Then, the array output signal out ′ _1k is as follows.

白抜きの×印は行列の要素毎の積を表す。ここで、θ_kの方向にヌルをもつためには前式は

The white cross indicates the product of each element of the matrix. Here, in order to have null in the direction of θ _k

となる。ここで、（３）式のヌル条件を拘束条件として、位相摂動量の自乗和を最小とする拘束条件付極値問題と考えれば、次式のように表せる。

It becomes. Here, assuming that the null condition of the equation (3) is a constraint condition and is considered as an extreme value problem with a constraint condition that minimizes the square sum of the amount of phase perturbation, it can be expressed as the following equation.

ここで、φ_iが十分小さいとして

Where φ _i is sufficiently small

と近似し、ラグランジュの未定係数法を用いて（４）式を解き、結果Φは（５）式となる（ステップＳ１４）。

(4) is solved using Lagrange's undetermined coefficient method, and the result Φ becomes (5) (step S14).

但し、Ｉはｎ次元単位ベクトルを示す。

Here, I represents an n-dimensional unit vector.

  Next, in step S15, it is determined whether or not a null condition is satisfied. It should be noted that whether or not the null condition is satisfied is that the beam shape formed by Φ obtained in step S14 is a constraint condition expression (3) (because (3) is set to = 0, but not completely = 0). It is determined whether or not the error is within an allowable range. If the null condition is not satisfied (No), it is determined whether or not i <imax (imax is a preset value and is the upper limit of the number of times to calculate the extreme value problem) in step S19. If not (NO), the process is terminated (step S20). If i <imax, the process proceeds to step S18, and the antenna weight is set to

と設定し直す。尚Φは式（５）で求めた結果である。次いで、ステップＳ１７に進み、ｉ＝ｉ＋１により、計算結果を示すカウンタをアップし、ステップＳ１３に進む。

And set again. Note that Φ is a result obtained by Expression (5). Next, the process proceeds to step S17, where i = i + 1, the counter indicating the calculation result is increased, and the process proceeds to step S13.

The calculation based on the above equation (5) is repeated using the phase perturbation Φ and the weight to obtain the phase perturbation Φ that satisfies the null condition (Yes in step S15). From the obtained phase perturbation Φ and the weight W _i at that time, the corrected antenna weight W ′,

を得る。Ｗ'から位相調整データを作成し、メモリに格納する（ステップＳ１６）ことにより受信装置が実現できる。

Get. The receiving apparatus can be realized by creating phase adjustment data from W ′ and storing it in the memory (step S16).

  As described above, when the antenna weight generation method according to the present embodiment is used, the phase corresponding to the beam shape having a null point in an arbitrary direction in the actual state of the apparatus including the influence between the antenna elements and the case is included. An adjustment amount can be obtained. Further, when the antenna elements are slightly deviated, that is, when the objectivity is lost, the phase adjustment amount can be easily calculated by using the beam shape forming method according to this embodiment. This is extremely effective when the antenna is actually mounted on the housing.

  Next, the frequency determination circuit and the spectral flatness will be described. First, a configuration example of the frequency characteristic determination circuit and an example of how to obtain a parameter indicating spectral flatness will be described. The spectral flatness in the frequency characteristic determination circuit can be defined and determined as follows.

  FIG. 4 is a diagram illustrating an example of a frequency spectrum. For the received signal in the transmission band, the amplitude and phase of the signal of each frequency component are extracted by FFT. As shown in FIG. 4A, the power (Y1, Y2,..., Yi,..., Yx) is obtained from the amplitude and phase of the extracted frequency component. Only amplitude may be used instead of electric power.

  Next, the average power A of the received signal within the transmission band is obtained. The absolute value | Yi−A | (i = 1,..., X) of the difference between the signal power Y1 to Yx of each frequency component and the average power A is obtained. A threshold value B to be compared with the average power A is set in advance.

  Next, the number of frequency components satisfying | Yi−A | ≦ B is counted to obtain the spectral flatness F. For example, as shown in FIG. 3A, when x frequency components are detected in the transmission band, if Z out of the x frequency components satisfy | Yi−A | ≦ B, F = Z It becomes. A larger value of F can be used as a parameter indicating that the received frequency spectrum is flatter. As described above, since the flatness determination process can be executed only by the signal power comparison operation and the counter, it can be easily realized by a digital circuit, and the circuit scale can be reduced.

  As shown in FIG. 4B, a plurality of threshold values (for example, p, for example, p = 2 in FIG. 4B) for comparing the average power A and the power (Y1 to Yx) of the frequency component are shown. ), Threshold values are B1, B2,..., B (p-1), Bp, and B1 <B2 <... <Bp, the spectrum flatness is obtained as follows. it can. First, the number of frequency components satisfying | Yi−A | ≦ B1 is counted as Z1, and a weight C1 is added to Z1 to obtain C1Z1.

  Next, the number of frequency components satisfying B1 <| Yi−A | ≦ B2 is counted as Z2, and a weight C2 is added to Z2 as C2Z2. Subsequently, in the same manner, the number of frequency components satisfying B (p−1) <| Yi−A | ≦ Bp is counted as Zp, and a weight Cp is added to Zp as CpZp. By adding these, the spectral flatness F can also be determined.

  That is, the spectral flatness F can be set to F = C1Z1 + C2Z2 + ... + CpZp. However, the weighting coefficients (C1, C2,..., Cp) are C1> C2>. Thus, by using a plurality of threshold values (B1 to Bp) and a plurality of weighting factors (C1 to Cp), the spectral flatness can be obtained more accurately, and multipath distortion can be effectively prevented. it can.

  When obtaining the above spectral flatness, if the communication method is a multicarrier communication method or OFDM method, the signal power (Y1 to Yx) of each frequency component may be the signal power of a subcarrier. Furthermore, when the pilot carrier and the data transmission carrier are divided among all the subcarriers in the OFDM communication system, the weighting factor used when obtaining the spectral flatness is determined by the pilot carrier and the data transmission carrier. By preparing different weighting factors separately and increasing the weighting factor of the pilot carrier, the flatness can be obtained. By using the above-mentioned method, the antenna is controlled so that the reception state of the pilot carrier is improved, so that the communication quality is improved in the communication system that performs fading compensation and error correction control using the pilot signal. There are advantages.

  Furthermore, in a communication system in which pilot carriers are arranged at equal intervals with respect to frequency, it is possible to obtain the flatness of the frequency characteristics using only the pilot carrier, and the arithmetic processing can be simplified, so the circuit scale There is an advantage that can be further reduced.

Next, the configuration of the control circuit and the beam switching method will be described. As described above, the spectral flatness F obtained by the frequency characteristic determination circuit is a parameter indicating a large value when the frequency characteristic is flatter. In the present embodiment, a threshold value TH _F of spectral flatness is set, and when F is larger than TH _F , it is determined that there is no influence of distortion due to multipath. Further, the beam switching control circuit has a function of detecting the received signal (array output signal) power P after antenna combination. The beam switching control circuit has a function of storing the optimum beam shape and a function of storing the spectral flatness of the optimum beam.

  Hereinafter, the flow of beam switching (scanning) control processing in the control unit will be described with reference to FIG. In the flowchart shown in FIG. 7, when the process is started (start), first, in step S31, after the power is turned on or waiting for the received signal, the beam switching control circuit reads the initial phase shift amount data, that is, the initial beam from the memory. Shape data, for example, data having a beam shape similar to that of an omni antenna is output, and a phase adjustment amount is set in the phase shifter of each branch. Next, in step S32, the beam switching control circuit stores the initial beam shape as the optimal beam shape, and stores “0” as the initial value of the flatness of the optimal beam.

Next, in step S33, a reception signal detection wait is performed, and the reception circuit or the beam switching control circuit determines whether or not there is a reception signal. If it is detected that there is a reception signal, the process proceeds to the next step S34. In step S34, the beam switching control circuit measures the array output signal power P). Then, in step S35, when the received signal power P measured in step S34, if it is determined to be larger than the threshold value TH _P set in advance the process proceeds to step S36, it is determined to be smaller than the threshold value TH _P Advances to step S40.

Here, use a threshold TH _P of the received signal power as a criterion, the received signal power is in order to prevent the cause flatness increases buried in the noise power. In other words, the received power P is equal to or higher than a certain value and the spectral flatness is high in order to obtain an appropriate beam shape.

  In step S36, the frequency characteristic determination circuit calculates the spectral flatness F. In step S <b> 37, the beam switching control circuit compares the spectral flatness of the optimum beam shape searched up to now with the spectral flatness of the current beam shape. As a result, if the flatness of the current beam shape is larger than the flatness of the optimum beam so far, the process proceeds to step S38, and if not, the process proceeds to step S40. In step S38, the beam switching control circuit stores the current beam shape as the optimum beam shape, and further stores the spectral flatness of the current beam shape as the optimum beam flatness.

In step S39, the beam switching control circuit compares the spectral flatness F of the current beam shape with a preset threshold value TH _F, and if the flatness F is greater than TH _F , the influence of multipath distortion is present. It is determined that there is no beam, the reception process is continued with the currently set beam shape, and the beam switching control flow is terminated (proceeds to END).

On the other hand, if the flatness F is smaller than the threshold value TH _F , the process proceeds to step S40. In step S40, in order to switch to the next candidate beam shape, the beam switching control unit outputs the phase adjustment amount for the next candidate beam shape from the memory, and switches the beam shape to the next candidate beam shape. After switching to the next candidate beam shape, the process proceeds to S34, and the process described above is repeated in the same manner.

  The processing described above is repeated until the beam shape satisfies the above conditions (S35, S37, S39), and a beam shape that is not affected by multipath distortion is searched. If there is no beam having a beam shape satisfying the above conditions (S35, S37, S39) in all the beam shapes stored in the memory, the beam shape is switched again to the optimum beam shape stored in the beam switching circuit. It is also possible to perform reception processing.

  Next, a reception technique according to a modification of the embodiment of the present invention will be described with reference to the drawings. The reception technique according to this modification is a technique for speeding up the process of switching to an appropriate beam shape by reducing the number of detections of the frequency characteristics of the beam shape when a plurality of beam shapes are stored in a memory. As shown in FIGS. 8A to 8D, as the beam shape stored in the memory in advance, for example, a plurality of beams having different beam widths or different beam directions are prepared ((A ) To (D)). The beam candidate ranks (in the figure, ranks 1 to 4) are assigned in order from the widest beam width.

  The received power and the spectral flatness are calculated by the above-described method in order from the rank 1 beam in the descending order of rank priority (rank number is low), and a beam exceeding the threshold is searched. When the condition regarding the spectral flatness is not satisfied at rank 1, a beam satisfying the spectral flatness condition is searched for the beam shapes # 2 and # 3 of rank 2 which is the next rank. If the flatness condition is not satisfied even in the rank-2 beam, the received powers of the beam shapes # 2 and # 3 are compared. As a comparison result, for example, if the received power of the beam shape # 2 is strong, # 4, # 5, and # 7 having directivity in the same direction as the # 2 direction from the candidate beam shape of the next rank are used as beam shape candidates. The received power is detected and the spectral flatness is detected.

  Similarly, when there is no beam shape satisfying the flatness condition at rank 3, the received power of rank 3 is compared, and a rank 4 beam having directivity in the same direction as the largest beam is searched as the next candidate. To do. By repeating the above processing, a beam satisfying the flatness condition is searched. Using the technique according to this modification has an advantage that the process of switching to an appropriate beam shape can be speeded up.

  As mentioned above, although demonstrated along this Embodiment, it cannot be overemphasized that this invention is not limited to these examples, and various deformation | transformation are possible.

  The present invention can be used as a reception system of a small wireless communication apparatus.

It is a figure which shows the example of whole structure of the receiver by one Embodiment of this invention, and is a figure for demonstrating collectively the flow of control in a receiver. It is a figure which shows the structural example of the memory by this Embodiment. 3A to 3E are diagrams showing examples of five different beam shapes (beam shapes # 1 to # 5). It is a figure which shows the example of a pattern of a frequency spectrum. It is a flowchart figure which shows the procedure which calculates | requires an antenna weight. FIG. 6 is a diagram illustrating in more detail the processing content in step S4 of FIG. It is a figure which shows the structural example of an adaptive array antenna, and has shown the example when the number of antenna elements is n pieces. When a plurality of beam shapes (beam shapes # 1 to # 15) having different beam widths and beam directions are stored in the memory, the ranking of the beam shapes (rank 1) when performing a search by ranking the beam shapes. It is a figure which shows the example of-rank 4). It is a figure which shows the structure of a general adaptive array antenna.

Explanation of symbols

  101-1 to 101-n: n antenna elements, 102-1 to n: phase shifter, 103-1 to n: D / A converter, 104: multiplexer, 105: A / D converter, 106: reception circuit, 107: FFT, 108: frequency characteristic determination circuit, 109: beam switching control circuit, 110: phase shift memory, 111: BPF, 112: mixer, 113: LPF.

Claims (21)

A plurality of antenna elements for receiving radio signals;
A phase shifter for adjusting the phase of the carrier wave of the received signal in each of the plurality of antenna elements for each antenna element;
A multiplexer that synthesizes the received signal whose phase is adjusted by the phase shifter;
An analog / digital converter that converts the synthesized signal synthesized by the multiplexer into a digital signal;
Fourier transform means for converting the digital signal from a time domain signal to a frequency domain signal;
And a control unit that controls the phase shifter based on the frequency characteristic obtained by the Fourier transform unit.   The receiving device according to claim 1, wherein the phase shifter is provided for at least one of the plurality of antenna elements.   The receiving device according to claim 1, wherein the phase shifter is provided for each of the plurality of antenna elements.   When the control means outputs a phase adjustment amount (antenna weight) to the phase shifter and gives a certain beam shape (coupling between the antenna elements and the surroundings of the antenna elements and the antenna elements) And determining the influence of electromagnetic coupling due to the arrangement state of the antenna element (with the influence of coupling with the antenna element), and forming a desired beam shape so as to reduce the influence based on the determination. The receiving device according to any one of claims 1 to 3.   In the control to be output to the phase shifter, the influence of the arrangement state of the antenna elements is changed at least by changing the antenna weight by the number of the antenna elements, and further changing the direction in which the carrier wave signal is incident by the number of the antenna elements. The phase shifter control based on the result of multiplying the inverse matrix of the Y matrix by the antenna weight in an ideal state. The receiving apparatus according to claim 4, wherein the receiving apparatus is provided as:   The control output to the phase shifter has an uncontrollable amplitude component for the result of multiplying the inverse matrix of Y and the antenna weight in an ideal state when adjusting only the phase. It is possible to obtain an antenna weight that can correct the deviation by giving a phase perturbation that minimizes the deviation of the beam shape by performing the calculation, and to give control of the phase shifter using the result. The receiving device according to claim 1, wherein the receiving device is characterized in that: A plurality of antenna elements for receiving radio signals;
A phase shifter for adjusting the phase of the carrier wave of the received signal in each of the plurality of antenna elements for each antenna element;
A multiplexer that synthesizes the received signal phase-adjusted by the phase shifter;
An analog / digital converter that converts the synthesized signal synthesized by the multiplexer into a digital signal;
A receiving circuit that performs signal processing of a received signal based on an output of the analog / digital converter,
Fourier transform means for converting a digital signal obtained as an output of the analog / digital converter from a time domain signal to a frequency domain signal;
Frequency characteristic determining means for determining flatness of the signal power in the frequency spectrum obtained by the Fourier transform means and making a determination on the flatness;
And a control unit that performs control related to adjustment by the phase shifter based on the determination result of the flatness.   The control means includes beam switching control means for switching a received beam shape representing directivity of an array output signal defined as a signal synthesized by the multiplexer based on the determination result. The receiving device according to claim 7. A memory for storing data relating to a phase shift amount necessary to generate a plurality of the desired beam shapes, and to the phase shifter to be read from the memory based on the determination result of the spectral flatness 9. The receiving device according to claim 7, wherein the control data is changed. In the beam switching control circuit and the means for determining the frequency characteristic,
A threshold of spectral flatness for determining reception characteristics;
A threshold of received power is prepared in advance,
The received power measured by the receiving circuit is compared with the threshold value of the received power, and when the received power is larger than the threshold value, the spectral flatness obtained by the frequency determination circuit and the threshold value of the spectral flatness 10. The receiving apparatus according to claim 7, wherein the receiving apparatus has a function of determining that the reception quality is good when the flatness is larger than a threshold value of the spectral flatness. .   11. The receiving apparatus according to claim 7, wherein the receiving apparatus has a function of searching for and setting a beam shape having good reception quality using the reception quality determination criterion.   The memory stores a plurality of beam shapes having different beam shape widths (half-value angles) and beam directions, and has the same rank for at least one beam shape having the same beam width but different beam directions. The rank has a function of increasing the priority of the rank in order of the width of the beam shape, and searching for a beam shape having good reception quality in descending order of the priority of the rank. The receiving device according to any one of 7 to 11.   When searching for the beam shape, if there are multiple beam shapes with different beam directions in the next-rank beam shape to be searched, the beam shape determined as the beam with the best reception quality in the result of searching at the current rank 13. The receiving apparatus according to claim 12, wherein a beam shape having a beam direction similar to is selected as a beam shape candidate to be searched next preferentially.   For the spectral flatness, a threshold value B is prepared in advance, and the absolute value of the difference between the average power A of each frequency component signal and the signal power Yi of each frequency component with respect to the frequency component signal that is the output result of the Fourier transform means. The receiving apparatus according to claim 7, wherein | Yi−A | is a result of counting the number of frequency components that are smaller than a threshold value B.   For the spectral flatness, a plurality of threshold values B1 to Bp and a plurality of weighting factors C1 to Cp are prepared in advance, and an average power A of each frequency component signal is obtained with respect to a frequency component signal that is an output result of the Fourier transform unit. The absolute value | Yi−A | of the difference between the signal power Yi of each frequency component is obtained, the number of frequency components satisfying | Yi−A | ≦ B1 is counted as Z1, and B1 <| Yi−A | ≦ B2 is satisfied. When the number of frequency components is counted and set as Z2, and the same processing is continued, the number of frequency components satisfying B (p−1) <| Yi−A | ≦ Bp is counted and set as Zp. 15. The reception apparatus according to claim 14, wherein the result of C1Z1 + C2Z2 +... + CpZp is defined as spectral flatness. The communication method is orthogonal frequency division multiplexing,
The receiving apparatus according to any one of claims 1 to 15, wherein the Fourier transform means is also used as a receiving Fourier transformer.   17. The receiver according to claim 16, wherein when the communication method is dedicated to a subcarrier for transmitting a pilot and a carrier for transmitting data, the spectrum flatness is determined by a subcarrier for pilot transmission and a subcarrier for data transmission. A receiving apparatus, wherein the calculation is performed by changing a weighting factor for a carrier.   The receiving apparatus according to claim 15 or 16, wherein when pilot carriers are arranged at equal intervals, only the pilot carrier is used when obtaining the flatness of the spectrum in the frequency characteristic determination circuit. A plurality of antenna elements;
A phase adjustment circuit for adjusting the phase of the carrier wave of the signal received by the antenna element for each branch of the plurality of antenna elements;
A synthesizing circuit that synthesizes the phase-adjusted received signals of the branches;
A receiving circuit that processes an output signal of the combining circuit;
A frequency characteristic detection circuit for detecting a frequency characteristic of the reception signal synthesized by the synthesis circuit;
A control circuit for performing control to change the beam forming phase adjustment data based on the detected frequency characteristics;
A memory for storing phase adjustment data for each antenna element;
A receiving apparatus comprising: a digital-analog circuit that converts the phase adjustment data into an analog signal voltage and outputs the analog signal voltage as a control voltage applied to the phase adjustment circuit.   A mobile terminal device comprising the receiving device according to claim 1.   The program for making a computer perform the function of the apparatus of any one of Claim 1-20.

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