JP4829849B2 - OFDM signal combining receiver and repeater - Google Patents

Description

  The present invention relates to a receiving apparatus and a relay apparatus for OFDM signal synthesis for digital broadcasting and digital transmission using an OFDM (Orthogonal Frequency Division Multiplexing) system, and particularly when receiving radio waves in digital broadcasting or wireless LAN. The present invention relates to a receiving apparatus for OFDM signal synthesis and a relay apparatus that apply adaptive array antenna technology and diversity reception technology to prevent fading and interference waves that are problematic.

  Examples of OFDM signal combining receivers to which the adaptive array technology is applied include those described in Patent Documents 1 and 2, for example.

[Outline of adaptive array for OFDM signal]
First, an outline of an OFDM signal adaptive array will be described. FIG. 5 is a diagram for explaining the outline of an OFDM signal combining receiver to which the adaptive array technology is applied. The OFDM signal combining receiver 101 includes an FFT (Fast Fourier Transform) unit 10-1, i, a weighting factor calculating unit 211, a reference signal generating unit 212, and a subtracting unit 213. And an array combining unit (carrier symbol combining unit) 30. Here, the FFT units 10-1 and i are configured by FFT units corresponding to the number of array elements, and i indicates a generic name of the numbers (the same applies hereinafter).

  Hereinafter, the operation of the OFDM signal combining receiver 101 will be described in detail. However, the number of array elements constituting an array antenna is L, the number assigned to any array element is l (0 ≦ l <L), the total number of subcarriers constituting the OFDM signal is K, and any subcarrier is assigned. The obtained number is assumed to be k (0 ≦ k <K).

The FFT unit 10 obtains carrier symbols x _{l, k} that are signals in the frequency domain by performing FFT on the effective symbol period of the received OFDM signal output from the l-th array element.

ここで、ｙ_ｋ，ｗ_ｋ，ｘ_ｋは、それぞれｋ番目のサブキャリヤにおけるアレー合成信号、重み係数ベクトル、および入力キャリヤシンボルベクトルであり、以下のように表すことができる。 If the weighting coefficient for the kth subcarrier of the received OFDM signal output from the lth array element is w _{l, k} , the array composite signal of the kth subcarrier by the array combiner (carrier symbol combiner) 30 is It is shown by Formula (1).

Here, y _k , w _k , and x _k are an array composite signal, a weight coefficient vector, and an input carrier symbol vector in the k-th subcarrier, respectively, and can be expressed as follows.

ここで、上付きの＊，Ｔ，Ｈは、それぞれ複素共役、転置、複素共役転置を示す。

Here, the superscripts *, T, and H indicate complex conjugate, transpose, and complex conjugate transpose, respectively.

ここで、Ｅ［・］は期待値演算を、ｅ_ｋおよびｒ_ｋはサブキャリヤｋにおける誤差および参照信号を示す。 Further, the weighting factor w _{l, k} can be obtained by optimization by the weighting factor control unit 201 so that the evaluation function J _represented by the equation (4) is minimized.

Here, E [•] indicates the expected value calculation, and e _k and r _k indicate the error and the reference signal in the subcarrier k.

  The reference signal must be able to be generated on the receiving side (OFDM signal combining receiver 101). For example, in the ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) system and the DVB-T (Digital Video Broadcasting-Terrestrial) system, which are broadcasting systems for digital terrestrial television broadcasting, SP (reference signal) is used as a reference signal as shown in FIG. Scattered Pilot) signal is inserted. In FIG. 7, SP is indicated by a black circle, and other carrier symbols are indicated by white circles. The SP signal is a signal having a predetermined amplitude and phase at the time of signal generation, and the same signal can be generated on the receiving side (OFDM signal combining receiver 101). Can be used.

  FIG. 6 is a diagram for explaining an outline of another OFDM signal combining receiver to which the adaptive array technique is applied. This OFDM signal combining receiver 102 includes an FFT unit 10-1, i, a channel estimation unit 214-1, i, a weight coefficient calculation unit 215, an array combining unit (channel response combining unit) 216, and a reference signal generating unit 217. And a weight coefficient control unit 202 having a subtracting unit 218 and an array combining unit (carrier symbol combining unit) 30.

The channel estimation unit 214 obtains a channel response by dividing the received SP signal (hereinafter referred to as the received SP signal) by the transmitted SP signal, that is, the SP signal at the time of generation (hereinafter referred to as the transmitted SP signal). . The weighting factor calculation unit 215 obtains a weighting factor by minimizing the evaluation function represented by Expression (6) using the channel response.

また、ｚ_ｋは、チャネル応答のアレー合成信号である。 Here, u _{l, k} represents the channel response at the subcarrier number k of the l-th array element, and u _k is a channel response vector obtained by vectorizing the channel response as follows.

Z _k is an array composite signal of channel response.

[Judgment-oriented type]
When the interference wave is the same ISDB-T signal as the desired wave, and the reception timing of the SP signal inserted in the same subcarrier every 4 symbols is close to or coincides with the desired wave, only the SP signal information If the weighting factor is calculated based on, the desired wave and the interference wave cannot be distinguished, and the interference wave is not removed but actively received. For this reason, not only the SP signal but also a data symbol whose modulation content is unknown is subjected to threshold determination, and an estimated value (hereinafter simply referred to as a determination value) of the data symbol obtained thereby is also used as a reference signal. There is a need to.

ただし、ｄ_ｋは、ｋ番目のサブキャリヤのキャリヤシンボルのアレー合成信号ｙ_ｋをしきい値判定処理することにより得られる判定値である。また、ｄｅｃ（ｙ）はしきい値判定のための関数であり、ｙに最も近い送信信号を返す。 At this time, the error _ek is defined by the following equation.

Here, d _k is a determination value obtained by performing threshold determination processing on the array combined signal y _k of the carrier symbol of the k-th subcarrier. Dec (y) is a function for determining a threshold value, and returns a transmission signal closest to y.

  FIG. 10 shows a block diagram of a weighting factor calculation method based on each optimization when the SP signal is a reference signal (SP reference type) and when the determination value is a reference signal (determination-oriented type).

[Phase identification]
In general, there may be a plurality of signal points having different phases only in the signal space of a digitally modulated signal such as PSK or QAM. For example, in QAM, since signal points similarly exist at positions obtained by rotating each signal point by π / 2, π, and 3π / 2 phases, the determination value has uncertainty regarding the phase. In order to eliminate this phase uncertainty, it is necessary to perform the following phase correction on the reference signal.

ただし、ｗ_{ｋ，ｏｐｔ}はｋ番目のサブキャリヤにおける最適重みを示す。チャネル応答値を最適重みで合成した結果が所望応答すなわち１＋０ｊとなることから、ｎはチャネル応答のアレー合成信号ｚ_ｋの位相から求められ、図１１に示すように、複素平面を４分割し、ｚ_ｋの位置からｎ_ｋを決定する。これをＮ_ｋとすれば、位相補正値はｅｘｐ（−ｊＮ_ｋπ／２）となる。 The channel response in all subcarriers can be obtained by performing SP reference channel estimation using an SP signal that is a transmission symbol having a known amplitude and phase, and performing interpolation in the symbol direction and subcarrier direction. When the weighting factor has not converged to the true minimum value of the evaluation function, the phase rotation of exp (jnπ / 2) is applied to the array synthesized signal z _k of the channel response as in the following equation (10). ing.

Here, w _{k, opt} represents the optimum weight in the kth subcarrier. Since the result of combining the channel response values with the optimum weight is a desired response, that is, 1 + 0j, n is obtained from the phase of the array response signal z _k of the channel response, and the complex plane is divided into four as shown in FIG. n _k is determined from the position of z _k . If this is N _k , the phase correction value is exp (−jN _k π / 2).

ここで、ｄｅｃ（ｙ）はしきい値判定の関数であり、ｙに最も近い送信信号を返す。 Therefore, as shown in the following equation (11), the determination value can be converged to the true optimum solution by multiplying the determination value by the phase correction value.

Here, dec (y) is a function of threshold determination, and returns a transmission signal closest to y.

とすると、以下の式（１３）（１４）が得られる。

ただし、Ｒｅ［・］，Ｉｍ［・］はそれぞれ複素数の実部および虚部を示す。ここで、図１１の領域判定について、式（１２）の左辺の実部、虚部の符号からＮ_ｋを求めることができる。また、符号のみを求めることができればよいから、式（１３）（１４）において√２は省略することができる。

Also, add π / 4 phase rotation to z _k

Then, the following equations (13) and (14) are obtained.

However, Re [•] and Im [•] indicate the real part and imaginary part of the complex number, respectively. Here, for the region determination in FIG. 11, N _k can be _obtained from the sign of the real part and the imaginary part on the left side of Expression (12). Further, since it is sufficient to obtain only the sign, √2 can be omitted in the equations (13) and (14).

  For such phase identification processing, refer to Japanese Patent Application No. 2006-241767, which was made by the same applicant and inventor as the present patent application and has not been published at the time of the present patent application.

JP 2003-174427 A JP 2005-295506 A

  Conventional OFDM signal combining receivers 101 and 102 use the difference in phase difference between a desired wave and an interference wave between a plurality of reception systems in order to remove the interference wave. Therefore, when there is no difference in the phase difference, the interference wave cannot be removed.

  However, if the arrival directions of the desired wave and interference wave are known, a directional antenna is used as the receiving antenna, the main antenna is directed to the arrival direction of the desired wave, and the auxiliary antenna is directed to the arrival direction of the interference wave. The interference D / U can be made different in the received signal output from each antenna. In particular, the auxiliary antenna can extract the interference wave component with a large U / D. In this way, by using the directivity gain of the physical antenna, the interference wave component received by the main antenna can be canceled by the replica signal generated from the interference wave component received by the auxiliary antenna, and interference cancellation can be performed. It becomes possible.

  On the other hand, when the interference signal includes the same signal component as the desired signal, such as when the SP reception timing difference between the desired signal and the interference signal matches, the interference component of the same channel is small in the signal of the auxiliary antenna reception system. Become. Therefore, in the conventional OFDM signal synthesis receivers 101 and 102, a plurality of received signals are handled in the same manner, so that there is a possibility that miscapture in which an interference wave is received instead of a desired wave occurs. There was a problem that the hope wave was suppressed.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to obtain a phase difference between a desired wave and an interference wave included in each of reception signals output from a plurality of antennas between the reception signals. Even if they are equal, the interference wave component contained in the main antenna reception signal is canceled by the replica signal generated from the interference wave component contained in the reception signal of one or more other auxiliary antennas, and the desired signal is good. It is an object of the present invention to provide an OFDM signal synthesizing receiver that can be easily extracted and a relay device that relays a desired wave favorably and stably using the same.

  In order to solve the above-described problems, an OFDM signal combining receiver according to the present invention receives an OFDM wave by an array antenna configured by using each of one main antenna and one or more auxiliary antennas as an array element, and outputs the received OFDM wave. , An FFT unit for the number of array elements to be output by converting the received OFDM signals for the number of array elements output from the array receiving unit into carrier symbols that are signals in the frequency domain by FFT, and the outputs of the FFT units A first carrier symbol combining unit that generates and outputs an array combined signal by performing weighted combining for each subcarrier of the OFDM signal with respect to a carrier symbol to be performed, and a weighting factor control unit that controls a weighting factor used for the weighted combining In the receiving apparatus for combining OFDM signals, the weighting coefficient control unit includes the FFs. A pilot extraction unit for the number of array elements for extracting pilot signals transmitted by a predetermined symbol number and subcarrier number from carrier symbols for the number of array elements output by the unit, and transmitting pilot signals with known amplitudes and phases. An array for obtaining a channel response in each array element and each subcarrier is obtained by dividing the received pilot signals for the number of array elements output by the pilot generation unit and the pilot extraction unit by the transmission pilot signals output by the pilot generation unit. Channel response calculation units for the number of elements, and channel response interpolation units for the number of array elements for interpolating the channel responses output from the channel response calculation units in the symbol direction and subcarrier direction to obtain channel responses in all subcarriers A channel estimation unit comprising: A channel response synthesizing unit that performs channel combining for the number of array elements output by the channel estimation unit using the weighting factor for each subcarrier of the OFDM signal; a desired response generating unit that generates a desired channel response; A phase identification unit comprising: an array combined signal of channel responses output from the channel response combining unit; and a phase correction value calculating unit for obtaining a phase correction value to be corrected from the desired response output from the desired response generating unit; A channel equalization unit that divides a carrier symbol output from the FFT unit in the reception system by a channel response output from the channel estimation unit in the main antenna reception system for each subcarrier of the OFDM signal; and an array element output from each FFT unit Array of carrier symbols for several minutes using the weighting factors of the relevant and adjacent subcarriers A plurality of second carrier symbol combining units for performing composition, and a plurality of array combined signals output from the plurality of carrier symbol combining units, multiplied by a phase correction value for each weight coefficient output from the phase identifying unit. Multiplying a vector composed of a plurality of phase correction units and a plurality of array combined signals output from the plurality of phase correction units by a predetermined carrier-to-carrier averaging matrix, and multiplying each component of the vector after the multiplication An inter-carrier averaging unit that outputs as a plurality of array composite signals after inter-carrier averaging processing, and a main antenna that the channel equalization unit outputs for each of the multiple array composite signals output by the inter-carrier averaging unit A plurality of weighting combining units for weighting and combining with carrier symbols after channel equalization of the receiving system, and a plurality of outputs from the respective weighting combining units A plurality of threshold value determination units for determining and outputting respective threshold values of the combined signal, and subtracting the combined signal output from each of the weighted combining units from the determination value output from each of the threshold value determination units A plurality of modulation error ratio calculation units for calculating a modulation error ratio using the plurality of errors and a plurality of determination values output from the respective threshold determination units, and each of the modulation error ratio calculation units A plurality of multipliers for multiplying each of a plurality of modulation error ratios to be output by a predetermined constant, and the threshold for giving a maximum value among the modulation error ratios output by the multipliers after constant multiplication; A reference signal calculation unit including a selection unit that selects a determination value output from the value determination unit and outputs the selection value as a reference signal; an array synthesis signal output from the first carrier symbol synthesis unit; and an output from the reference signal calculation unit With reference signal to The difference is characterized by comprising a weight coefficient calculation unit to optimize the weighting coefficients so as to minimize.

  In the OFDM signal combining receiver according to the present invention, the reference signal calculation unit of the weighting factor control unit outputs the threshold value determination unit instead of the modulation error ratio calculation unit, the multiplication unit, and the selection unit. A plurality of error calculation units for calculating an error by subtracting the combined signal output from each of the weighted combining units from the determination value, and multiplying each of the plurality of errors output from the respective error calculation units by a predetermined constant A selection unit that selects a determination value output from the threshold value determination unit that gives a minimum value from errors after constant multiplication output from each multiplication unit, and outputs the reference value as a reference signal; It is characterized by providing.

  Further, in the OFDM signal combining receiver according to the present invention, the weighting factor control unit outputs, for each subcarrier of the OFDM signal, carrier symbols corresponding to the number of array elements output from each FFT unit, instead of the weighting factor calculation unit. By dividing by the reference signal output from the reference signal calculation unit, a division unit for calculating a channel response, and channel response corresponding to the number of array elements output from each division unit is subjected to array combining processing using the weighting factor. An error calculation for calculating an error by subtracting the array response signal of the channel response output from the channel response combining unit from the desired response output from the desired response generating unit, a channel response combining unit, a desired response generating unit for generating a desired response And an error output from the error calculation unit using the channel response value corresponding to the number of array elements output from each division unit and the error output from the error calculation unit. So as to, characterized in that it comprises a weighting coefficient calculating unit to optimize the weighting coefficients.

  Also, in the OFDM signal combining receiver according to the present invention, the weighting factor calculation unit of the weighting factor control unit optimizes the weighting factor so that the error is minimized, and the weighting factor and the auxiliary in the receiving system of the main antenna An optimization unit that outputs a weighting factor in the reception system of the antenna, a norm calculation unit that calculates a norm for each subcarrier with respect to the weighting factor in the reception system of the main antenna that is output from the optimization unit, and a norm calculation unit For the norm of the weighting factor for each subcarrier to be output, an averaging unit for obtaining an average value of all the subcarriers, and multiplying the norm average value of the weighting factor output by the averaging unit by a predetermined constant, A multiplier that outputs a value, a norm of a weight coefficient for each subcarrier output from the norm calculation unit, and a threshold value output from the multiplier; A comparison unit that outputs a comparison result, and a subcarrier whose weight coefficient norm is smaller than a threshold value based on the comparison result output from the comparison unit; Weighting factor replacement that replaces the weighting factor of the subcarrier among the weighting factors in the receiving system of the antenna with one of the weighting factor of the adjacent subcarrier, the weighting factor obtained by interpolation, or a predetermined initial weighting factor. And a section.

  Furthermore, the relay apparatus according to the present invention uses the OFDM signal synthesis receiver.

  As described above, according to the present invention, even when the phase difference between the desired wave and the interference wave included in each of the received signals output from the plurality of antennas is equal between the received signals, the received signal is the main antenna received signal. For OFDM signal synthesis, which can cancel out the included interference wave component with a replica signal generated from the interference wave component included in the received signal of one or more other auxiliary antennas, and extract the desired signal well It is possible to realize a receiving apparatus and a relay apparatus that relays a desired wave favorably and stably using the receiving apparatus.

The best mode for carrying out the present invention will be described below in detail with reference to the drawings.
[Example 1]
FIG. 1 is a block diagram showing a first configuration of an OFDM signal combining receiver according to an embodiment of the present invention. The OFDM signal combining receiver 1 includes an FFT unit 10-1, i, a weight coefficient control unit 21, and an array combining unit (carrier symbol combining unit) 30. The weight coefficient control unit 21 includes a weight coefficient calculation unit 41, a subtraction unit 42, a reference signal calculation unit 50, and a phase identification unit 70. The reference signal calculation unit 50 includes a carrier symbol synthesis unit 51, a phase correction unit 52, an inter-carrier averaging unit 53, a channel equalization unit 54, a weighting synthesis unit 55, a threshold determination unit 56, and a modulation error ratio calculation unit. 57, a multiplication unit 58, a maximum value detection unit 59-1, and a selection unit 59-2. The phase identification unit 70 includes a channel estimation unit 71-1, i, a channel response synthesis unit 72, a desired response generation unit 73, And a phase correction value calculation unit 74.

  The FFT unit 10 is composed of FFT units for the number of array elements, and receives each received OFDM signal for the number of array elements received and output by the array antenna composed of a main antenna and a plurality of auxiliary antennas. Fast Fourier transform is performed on the received OFDM signal, and a carrier symbol which is a frequency domain signal is output. The output of the FFT unit 10-1 of the main antenna reception system is divided into five and input to the carrier symbol combining unit 30, the weight coefficient calculating unit 41, the carrier symbol combining unit 51, the channel equalizing unit 54, and the channel estimating unit 71-1. Is done. The output of the FFT unit 10-i of the auxiliary antenna reception system is divided into four and input to the carrier symbol combining unit 30, the weighting factor calculating unit 41, the carrier symbol combining unit 51, and the channel estimating unit 71-i.

  The carrier symbol combining unit 30 performs array combining processing for each subcarrier of the OFDM signal using the carrier symbols for the number of array elements input from each FFT unit 10 and the weighting factor input from the weighting factor calculating unit 41. And output as an array composite signal. Details of the carrier symbol combining unit 30 will be described later. The output of the carrier symbol synthesis unit 30 is divided into two, one is input to the subtraction unit 42 and the other is supplied to the outside.

  The subtracting unit 42 of the weighting coefficient control unit 21 subtracts the array combined signal input from the carrier symbol combining unit 30 from the reference signal input from the reference signal calculating unit 50, and outputs the result as an error signal. The weighting coefficient calculation unit 41 uses the carrier symbols for the number of array elements input from each FFT unit 10 and the error signal input from the subtraction unit 42 to calculate a weighting coefficient that minimizes the error signal. Output. The weighting coefficient output from the weighting coefficient calculation unit 41 is divided into three and input to the carrier symbol combining unit 30, the carrier symbol combining unit 51, and the channel response combining unit 72, respectively.

  The channel estimation unit 71 in the phase identification unit 70 of the weighting factor control unit 21 is composed of channel estimation units for the number of array elements, and each sub signal of the OFDM signal is generated from carrier symbols for the number of array elements input from the FFT unit 10. Each channel response in the carrier is estimated and output. Details of the channel estimation unit 71 will be described later. The channel response combining unit 72 performs an array combining process on the channel response of each subcarrier of the OFDM signal corresponding to the number of array elements input from each channel estimating unit 71 using the weighting factor input from the weighting factor calculating unit 41. And output as an array composite signal of channel response. Details of the channel response combining unit 72 will be described later. The desired response generation unit 73 generates and outputs a desired channel response, that is, 1 + 0j. The phase correction value calculation unit 74 obtains the phase rotation angle by using the array response signal of the channel response input from the channel response combination unit 72 and the desired channel response input from the desired response generation unit 73, and obtains this. A phase correction value for correction is calculated and output.

  The channel equalization unit 54 in the reference signal calculation unit 50 of the weighting coefficient control unit 21 inputs the carrier symbol input from the FFT unit 10-1 of the main antenna reception system from the channel estimation unit 71 for each subcarrier of the OFDM signal. By dividing by the channel response, channel equalization is performed and output as a carrier symbol after channel equalization.

  The carrier symbols corresponding to the number of array elements output from each FFT unit 10 and input to the reference signal calculation unit 50 are distributed and input to a plurality of carrier symbol combining units 51. For each subcarrier of the OFDM signal, the plurality of carrier symbol combining units 51 uses the weighting factors of the subcarriers or a plurality of adjacent subcarriers among the weighting factors input from the weighting factor calculating unit 41 to perform each FFT. The carrier symbols for the number of array elements input from the unit 10 are subjected to array combining processing, and a plurality of array combined signals are output. Details of the carrier symbol combining unit 51 will be described later.

  The plurality of phase correction units 52 multiply the plurality of array combined signals input from the carrier symbol combining unit 51 by the phase correction value for each subcarrier of the OFDM signal input from the phase identification unit 70, and perform phase correction processing. And output. The inter-carrier averaging unit 53 multiplies a vector composed of a plurality of array composite signals input from the phase correction unit 52 by a predetermined inter-carrier averaging matrix and outputs the result. The plurality of weighting / combining units 55 receives the plurality of array combined signals input from the inter-carrier averaging unit 53 and the channel equalized carrier symbols input from the channel equalizing unit 54 from the weight coefficient calculating unit 41. Each is weighted and synthesized according to the input error and output. The outputs of the plurality of weighting / combining units 55 are divided into two, one being input to the threshold value determining unit 56 and the other being input to the modulation error ratio calculating unit 57.

  The plurality of threshold determination units 56 perform threshold determination processing on the plurality of weighted combined signals input from the weighted combining unit 55, and are known ideals having the smallest error from the input array combined signal. Output a signal. The ideal signals output from the plurality of threshold determination units 56 are divided into two, one being input to the selection unit 59-2 and the other being input to the modulation error ratio calculation unit 57. The plurality of modulation error ratio calculation units 57 calculate errors by subtracting the respective weighted combined signals input from the weighted combining unit 55 from the respective ideal signals input from the threshold value determining unit 56. The modulation error ratio is calculated using the error and each ideal signal input from the threshold value determination unit 56, and the result is output. The plurality of multipliers 58 multiply each modulation error ratio input from the modulation error ratio calculator 57 by a predetermined constant and output the result. The maximum value detection unit 59-1 detects the maximum value among the plurality of modulation error ratios input from the multiplication unit 58, and outputs a selection control signal indicating the system that has output the maximum value. The selection unit 59-2 is based on the selection control signal indicating the system that has output the maximum value of the modulation error ratio input from the maximum value detection unit 59-1, and the ideal is input from the threshold value determination unit 56 of that system. A signal is selected and output as a reference signal.

  FIG. 8 is a block diagram showing a configuration of channel estimation unit 71 shown in FIG. The channel estimation unit 71 includes a pilot extraction unit 711, a pilot generation unit 712, a division unit 713, and an interpolation unit 714.

  Pilot extraction section 711 extracts a pilot signal transmitted as a carrier symbol having a predetermined symbol number and subcarrier number from the carrier symbol input from FFT section 10 and outputs it as a received pilot signal. Pilot generation section 712 generates and outputs a pilot signal having a predetermined amplitude and phase. Divider 713 divides the received pilot signal input from pilot extractor 711 by the pilot signal input from pilot generator 712, and obtains and outputs a channel response in the subcarrier on which the pilot signal is transmitted. Interpolation section 714 interpolates the channel response input from division section 713 in the symbol direction and subcarrier direction, calculates the channel response in all subcarriers of the OFDM signal, and outputs it.

  FIG. 9 is a block diagram showing the configuration of carrier symbol combining unit 30, carrier symbol combining unit 51, and channel response combining unit 72, which are the array combining units shown in FIG. This array synthesis unit includes complex conjugate units 301-1, i, multiplication units 302-1, i, and an addition unit 303. A channel response combining unit 45, which will be described later, also has the same internal configuration as this array combining unit. The carrier symbol combining units 30 and 51 input carrier symbols from the outside, whereas the channel response combining units 72 and 45 input channel responses from the outside.

  The complex conjugate unit 301 includes complex conjugate units for the number of array elements, and generates and outputs complex conjugate values of weight coefficients for the number of array elements input from the weight coefficient calculation unit 41. Multiplier 302 includes multipliers for the number of array elements, and multiplies the input carrier symbol or channel response by the complex conjugate value input from complex conjugate unit 301 and outputs the result. Adder 303 adds the multiplication results for the number of array elements input from multiplier 302 and outputs the result as an array composite signal.

[Example 2]
FIG. 2 is a block diagram showing a second configuration of the OFDM signal combining receiver according to the embodiment of the present invention. The OFDM signal combining receiver 2 includes an FFT unit 10-1, i, a weight coefficient control unit 22, and an array combining unit (carrier symbol combining unit) 30. The weight coefficient control unit 22 includes a weight coefficient calculation unit 41, a subtraction unit 42, a reference signal calculation unit 60, and a phase identification unit 70. The reference signal calculation unit 60 includes a carrier symbol synthesis unit 51, a phase correction unit 52, an inter-carrier averaging unit 53, a channel equalization unit 54, a weighting synthesis unit 55, a threshold value determination unit 56, an error calculation unit 61, Multiplier 58, minimum value detector 63, and selector 59-2, and phase identification unit 70 includes channel estimators 71-1 and 71, channel response synthesizer 72, desired response generator 73, and phase correction value. A calculation unit 74 is provided.

  The OFDM signal combining receiver 1 shown in FIG. 1 and the OFDM signal combining receiver 2 shown in FIG. 2 have the same configuration of the FFT units 10-1 and i and the array combining unit (carrier symbol combining unit) 30. Yes, the configurations of the weight coefficient control units 21 and 22 are different. In the weight coefficient control unit 22 of the OFDM signal combining receiver 2, the weight coefficient calculation unit 41, the subtraction unit 42, and the phase identification unit 70 have the same configuration, and the error calculation unit 61 and the minimum value detection in the reference signal calculation unit 60 The configuration other than the unit 63 is the same. That is, the OFDM signal synthesis receiver 2 shown in FIG. 2 uses an error calculator 61 and a minimum value detector instead of the modulation error ratio calculator 57 and the maximum value detector 59-1 of the OFDM signal synthesis receiver 1. The difference is that 63 is provided. Hereinafter, the description of the same configuration as that in FIG. 1 is omitted.

  The plurality of error calculators 61 subtract the respective weighted combined signals input from the weighted combiner 55 from the determination values that are the respective ideal signals input from the threshold determination unit 56 to generate an error signal. Output. The plurality of multipliers 58 multiply each error signal input from the error calculator 61 by a predetermined constant and output the result. The minimum value detection unit 63 detects the minimum value of the plurality of error signals input from the multiplication unit 58, and outputs a selection control signal indicating the system that has output the minimum value.

Example 3
FIG. 3 is a block diagram showing a third configuration of the OFDM signal combining receiver according to the embodiment of the present invention. This OFDM signal combining receiver 3 includes FFT units 10-1, i, a weight coefficient control unit 23, and an array combining unit (carrier symbol combining unit) 30. In addition, the weight coefficient control unit 23 includes a weight coefficient calculation unit 41, a subtraction unit 42, a division unit 43-1, i, a channel response synthesis unit 45, a desired response generation unit 46, a reference signal calculation unit 50, and a phase identification unit 70. It has. The reference signal calculation unit 50 includes a carrier symbol synthesis unit 51, a phase correction unit 52, an inter-carrier averaging unit 53, a channel equalization unit 54, a weighting synthesis unit 55, a threshold determination unit 56, and a modulation error ratio calculation unit. 57, a multiplication unit 58, a maximum value detection unit 59-1, and a selection unit 59-2. The phase identification unit 70 includes a channel estimation unit 71-1, i, a channel response synthesis unit 72, a desired response generation unit 73, And a phase correction value calculation unit 74.

  The OFDM signal combining receiver 1 shown in FIG. 1 and the OFDM signal combining receiver 3 shown in FIG. 3 have the same configuration of the FFT units 10-1, i and the array combining unit (carrier symbol combining unit) 30. Yes, the configurations of the weight coefficient control units 21 and 23 are different. In the weight coefficient control unit 23 of the OFDM signal combining receiver 3, the weight coefficient calculation unit 41, the subtraction unit 42, the reference signal calculation unit 50, and the phase identification unit 70 have the same configuration. That is, the receiving apparatus 3 for OFDM signal synthesis shown in FIG. 3 is different in that it includes a dividing unit 43, a channel response combining unit 45, and a desired response generating unit 46 in addition to the configuration of the receiving apparatus 1 for OFDM signal synthesis. To do. Hereinafter, the description of the same configuration as that in FIG. 1 is omitted.

  The division unit 43 is composed of division units for the number of array elements, and the carrier symbols for the number of array elements input from the FFT unit 10 are received from the reference signal calculation unit 50 for each subcarrier of the OFDM signal. Divide by and output the channel response. The output of the division unit 43 is divided into two, one being input to the weight coefficient calculation unit 41 and the other being input to the channel response synthesis unit 45. The channel response combining unit 45 performs array combining of the channel responses corresponding to the number of array elements input from the dividing unit 43 using the weighting factor input from the weighting factor calculating unit 41 for each subcarrier of the OFDM signal, The array composite signal is output. Desired response generator 46 generates and outputs a desired channel response. The subtracting unit 42 subtracts the array response signal of the channel response input from the channel response combining unit 45 from the desired channel response input from the desired response generating unit 46 and outputs it as an error signal. The weighting factor calculation unit 41 uses the channel response for the number of array elements input from the division unit 43 and the error signal input from the subtraction unit 42 to calculate a weighting factor that minimizes the error signal. Output.

Example 4
FIG. 4 is a block diagram showing a fourth configuration of the OFDM signal combining receiver according to the embodiment of the present invention. The OFDM signal combining receiver 4 includes an FFT unit 10-1, i, a weight coefficient control unit 24, and an array combining unit (carrier symbol combining unit) 30. In addition, the weight coefficient control unit 24 includes a weight coefficient calculation unit 41, a subtraction unit 42, a division unit 43-1, i, a channel response synthesis unit 45, a desired response generation unit 46, a reference signal calculation unit 60, and a phase identification unit 70. It has. The reference signal calculation unit 60 includes a carrier symbol synthesis unit 51, a phase correction unit 52, an inter-carrier averaging unit 53, a channel equalization unit 54, a weighting synthesis unit 55, a threshold value determination unit 56, an error calculation unit 61, Multiplier 58, minimum value detector 63, and selector 59-2, and phase identification unit 70 includes channel estimators 71-1 and 71, channel response synthesizer 72, desired response generator 73, and phase correction value. A calculation unit 74 is provided.

  The OFDM signal combining receiver 2 shown in FIG. 2 and the OFDM signal combining receiver 4 shown in FIG. 4 have the same configuration of the FFT units 10-1, i and the array combining unit (carrier symbol combining unit) 30. Yes, the configurations of the weight coefficient control units 22 and 24 are different. In the weight coefficient control unit 24 of the OFDM signal combining receiver 4, the configurations of the weight coefficient calculation unit 41, the subtraction unit 42, the reference signal calculation unit 50, and the phase identification unit 70 are the same. That is, the OFDM signal combining receiver 4 shown in FIG. 4 is different in that it includes a dividing unit 43, a channel response combining unit 45, and a desired response generating unit 46 in addition to the configuration of the OFDM signal combining receiver 2. To do.

  3 is compared with the OFDM signal synthesis receiver 4 shown in FIG. 4, the OFDM signal synthesis receiver 3 calculates the modulation error ratio in the reference signal calculator 50. The OFDM signal synthesizing receiving device 4 is different from the reference signal calculating unit 60 in that the error calculating unit 61 and the minimum value detecting unit 63 are provided. To do. The division unit 43, the channel response synthesis unit 45, and the desired response generation unit 46 included in the OFDM signal synthesis receiver 4 are the same as those shown in FIG. 3, and the error calculation unit 61 and the minimum value detection unit 63 are Since it is the same as what was shown in FIG. 2, description is abbreviate | omitted here.

[When using ISDB-T method]
A detailed description will be given of a case where the ISDB-T system is used in the OFDM signal combining receivers 1, 2, 3, and 4 configured as described above.

を満足する。ただし、ｍｏｄは剰余を示す。以下、式（１６）を満足するｉ，ｋをそれぞれｉ_ｐ，ｋ_ｐとする。 [SP reference channel estimation and decision-oriented channel estimation]
In the ISDB-T system, the subcarriers assigned to the SP are assumed to have a symbol number i and a sub carrier number k.

Satisfied. However, mod indicates a remainder. Hereinafter, i and k satisfying the equation (16) are assumed to be i _p and k _p , respectively.

In the channel estimation unit 71 shown in FIG. 8, the received SP signal extracted by the pilot extraction unit (SP extraction unit) 711 is x _{ip, kp} , and the SP signal (ISDBT) generated by the pilot generation unit (SP generation unit) 712 Assuming that an SP signal generated and transmitted by the modulator (hereinafter simply referred to as a transmitted SP signal) is s _{ip, kp} , the channel response u at the symbol number i _p and subcarrier number k _p calculated by the division unit 713. _{ip and kp} are expressed by the following equations.

  Here, the method of using the SP signal adopted in the ISDB-T system as a reference signal for calculating the channel response has been described. However, the amplitude and phase are known and the receiving side (OFDM signal combining receivers 1 and 2). , 3, 4) can be used as a reference signal for calculating the channel response in the same manner.

  Thus, when the channel response is obtained with reference to the SP signal, the channel responses in all symbols and subcarriers cannot be obtained directly. In order to obtain channel responses in all symbols and subcarriers, the interpolation unit 714 needs to perform interpolation processing on the symbols and subcarrier directions.

As the interpolation in the symbol direction, for example, the following latest value holding method or linear interpolation method can be used, and the interpolation unit 714 performs interpolation processing according to the following equation.
In the case of the latest value holding method, the following formula is used.

In the case of linear interpolation, the following formula is used.

Further, for example, the following linear interpolation method can be used as the interpolation in the subcarrier direction, and the interpolation unit 714 performs an interpolation process according to the following equation.

  On the other hand, as a method of directly obtaining channel responses in all symbols and subcarriers, a method of estimating a data symbol (hereinafter simply referred to as a transmission signal) at the time of signal generation in an ISDB-T modulator and using it in the same manner as an SP signal. is there.

If the decision value obtained by threshold decision processing of the received carrier symbol at symbol number i and subcarrier number k in equation (9) is d _{i, k} (estimated value of transmission signal), the channel response is given by can get.

ここで、左辺はチャネル等化後のキャリヤシンボルを示す。 [Channel equalization]
Since the carrier symbol output from the FFT unit 10 includes transmission path distortion and an error in processing on the demodulation side (reception side (OFDM signal synthesis receivers 1, 2, 3, 4)), threshold determination Before the decoding process, it is necessary to divide by the channel response value obtained using the SP signal. The channel equalization unit 54 performs such channel equalization processing by the following equation.

Here, the left side shows a carrier symbol after channel equalization.

ここで、ｙ_ｋおよびｚ_ｋは、それぞれキャリヤシンボルのアレー合成信号およびチャネル応答のアレー合成信号を示し、ｗ_ｋ，ｘ_ｋおよびｕ_ｋは、それぞれサブキャリヤ番号ｋについての重み係数ベクトル、受信キャリヤシンボルベクトルおよびチャネル応答ベクトルを示す。 [Combination of carrier symbols and channel response]
Dividing both sides of formula (1) in the reference signal r _k, the following equation is obtained.

Here, y _k and z _k indicate an array combined signal of a carrier symbol and an array combined signal of a channel response, respectively, and w _k , x _k, and u _k respectively represent a weight coefficient vector and a received carrier for subcarrier number k. A symbol vector and a channel response vector are shown.

したがって、受信キャリヤシンボルベクトルｘ_ｋを重み係数ベクトルｗ_ｋを用いてアレー合成した結果ｙ_ｋと参照信号ｒ_ｋとの間の誤差を最小化する、すなわちｙ_ｋ→ｒ_ｋとすることは、チャネル応答ベクトルｕ_ｋを重み係数ベクトルｗ_ｋを用いてアレー合成した結果ｚ_ｋ→１となるように最適化することと等価である。 Similarly, dividing both sides of Equation (4) in the reference signal r _k, the following equation is obtained.

Therefore, minimizing the error between the result y _{k of} the received carrier symbol vector x _k using the weighting coefficient vector w _k and the reference signal r _k , ie, y _k → r _k This is equivalent to optimizing the response vector u _{k so} that z _k → 1 as a result of array synthesis using the weight coefficient vector w _k .

  Here, in the OFDM signal combining receiver 1 shown in FIG. 1 and the OFDM signal combining receiver 2 shown in FIG. 2, the weighting coefficient calculating unit 41 minimizes the evaluation function of the expression (4). In the OFDM signal synthesis receiver 3 shown in FIG. 3 and the OFDM signal synthesis receiver 4 shown in FIG. 4, the weighting coefficient calculation unit 41 minimizes the evaluation function of Equation (6).

(Phase identification part)
Since the phase identification unit 70 has been described above, the description thereof is omitted here. For details, see Japanese Patent Application No. 2006-241767 filed by the same applicant and inventor.

ここで、ｌ（エル）はｋ−ｍ≦ｌ≦ｋ＋ｍを満たす任意の整数である。ｍは十分小さな整数であり、例えば１でもよい。図１〜４の例はｍ＝１の場合を示している。 [Reference signal calculator]
Next, the reference signal calculation units 50 and 60 will be described. The reference signal calculation units 50 and 60 perform processing for each subcarrier of the OFDM signal. Here, the subcarrier number is k. First, the carrier symbol vector x _k for subcarrier number k, and array combined processing using the weighting coefficients for the adjacent 2m + 1 sub carriers, generates an array combined signal.

Here, l (el) is an arbitrary integer satisfying k−m ≦ l ≦ k + m. m is a sufficiently small integer, and may be 1, for example. The example of FIGS. 1-4 has shown the case where m = 1.

The phase is determined by multiplying the array composite signal by the phase correction value as shown in Expression (27).

に対して、次の式（２８）のように、キャリヤ間平均化行列Ａを掛ける。

ここで、

である。ここで、

は行列演算後のアレー合成信号である。 Further, when a multipath with a long delay time is received, since the optimum weight differs for each subcarrier, a vector composed of 2m + 1 array composite signals

Is multiplied by an intercarrier averaging matrix A as shown in the following equation (28).

here,

It is. here,

Is an array composite signal after matrix operation.

The intercarrier averaging matrix A is multiplied to absorb the difference in channel response multiplied by each adjacent subcarrier. For example, when m = 1, the following may be performed.

  In the first row of A, an array combined signal is obtained by the average value of the weight coefficient vectors between both adjacent subcarriers. For example, when only the subcarrier has not sufficiently converged to the optimum solution, a correct determination value can be obtained by the action from both adjacent subcarriers and the convergence can be made. Further, in the second row of A, an array combined signal based on the weight coefficient vector of only the subcarrier is obtained. This corresponds to a normal decision-oriented type. In the third row of A, an array combined signal is obtained by a coefficient vector obtained by weighted averaging of the weight coefficient vectors of the subcarrier and both adjacent subcarriers.

ここで、

は主アンテナ受信系統のチャネル等化後のキャリヤシンボルを示す。また、α_ｉは、時刻ｉにおける重み付けの適応係数であり、例えば式（４）の評価関数値を０≦α_ｉ≦１の範囲になるように定数倍した値とすればよい。

Next, the array combined signal after the inter-carrier averaging is weighted and combined with the carrier symbol after channel equalization of the main antenna reception system.

here,

Indicates a carrier symbol after channel equalization of the main antenna reception system. Α _i is a weighting adaptive coefficient at time i, and may be a value obtained by multiplying the evaluation function value of Equation (4) by a constant so as to be in the range of 0 ≦ α _i ≦ 1, for example.

At a stage where the evaluation function value is large and the weighting coefficient has not converged to the optimal solution, α _i becomes a large value, and the weight for the carrier symbol after channel equalization of the main antenna reception system becomes large in Equation (32). Thereby, it is possible to prevent miscapture of the interference wave. The stage where the weighting factor converges to the optimal solution and the evaluation function value decreases means that the interference wave is removed from the array composite signal, and the main antenna reception system from which the interference wave is not removed in Equation (32) The weight for the array combined signal from which the interference wave is removed becomes larger than the carrier symbol after channel equalization. If the weighting coefficient finally converges sufficiently, the interference signal is removed from the array composite signal, and the desired wave is extracted.

をそれぞれしきい値判定し、式（３４）に示す仮の判定値

を生成する。

ここで、ｄｅｃ（ｙ）はしきい値判定の関数であり、ｙに最も近い送信データを返す。さらにそれぞれについて式（３５）を用いて仮の判定値

とアレー合成信号

とのノルム（残留誤差）

をそれぞれ算出する。

ここで、定数β_ｌは、それぞれの誤差に対する重み付けをするパラメータである。 Next, multiple array combined signals after weighted combining

Are respectively determined as threshold values, and provisional determination values shown in Expression (34)

Is generated.

Here, dec (y) is a threshold determination function, and returns transmission data closest to y. Further, a provisional judgment value is used for each using equation (35)

And array composite signal

Norm (residual error)

Are calculated respectively.

Here, the constant β _l is a parameter for weighting each error.

が最小であるｌをｊとして選択し、

を参照信号とする。

Finally,

Choose l, where is the smallest, as j,

Is a reference signal.

  Here, in the OFDM signal combining receiver 1 shown in FIG. 1 and the OFDM signal combining receiver 3 shown in FIG. 3, the maximum value detector 59-1 obtains the maximum value of the modulation error ratio. On the other hand, in the OFDM signal synthesis receiver 2 shown in FIG. 2 and the OFDM signal synthesis receiver 4 shown in FIG. 4, the minimum value detector 63 obtains the minimum value of the error.

ここで、

はキャリヤ番号ｋにおける受信シンボルを示す。（Ｉ_ｋ，Ｑ_ｋ）は、式（９）のように、受信シンボルをシンボル判定して得られる既知の送信信号ベクトルの推定値である。（δＩ_ｋ，δＱ_ｋ）は、推定送信信号ベクトルと受信シンボルとの誤差ベクトルを示す。 The modulation error ratio (MER) is generally defined by the following equation. Refer to the following documents for details.
ETR290: Measurement guidelines for DVB Systems, ETSI Technical Report, may 1997

here,

Indicates a received symbol in carrier number k. (I _k , Q _k ) is an estimated value of a known transmission signal vector obtained by symbol-determining a received symbol as shown in Equation (9). (ΔI _k , δQ _k ) indicates an error vector between the estimated transmission signal vector and the received symbol.

変調誤差比は、キャリヤシンボルの信号点としての確からしさを示す数値であり、誤差との違いはその信号点電力によって正規化されているか否かにある。 The modulation error ratio is generally the ratio of the sum of signal power and error power for all data symbols for each OFDM symbol as shown in equation (38). Considering the modulation error ratio for each subcarrier, Then, it defines with Formula (40).

The modulation error ratio is a numerical value indicating the probability of a carrier symbol as a signal point, and the difference from the error is whether or not it is normalized by the signal point power.

  Also, the smaller the error, the more likely the signal point, whereas the larger the modulation error ratio, the more likely the signal point. For this reason, when the modulation error ratio is used, the maximum value of the plurality of modulation error ratios may be detected, and the threshold determination value of the carrier symbol that gives the maximum modulation error ratio may be selected.

について、判定値としての確からしさを次の式（４１）により定義する。

ここで、定数β_ｌは、それぞれの変調誤差比に対して重み付けを行うためのパラメータである。 Further, since the purpose is to compare the probabilities as signal points, there is no need for dB conversion. Therefore, provisional judgment value

The probability as a determination value is defined by the following equation (41).

Here, the constant β _l is a parameter for weighting each modulation error ratio.

Further, when equation (33) is used for A, the determination error (selection error) is reduced by increasing the weight β _k for the determination value generated using the weight coefficient in the second row, that is, the subcarrier. Can do.

Since the larger value of the MER is likely to be a signal point, the maximum value of a plurality of weighted MERs is detected, and l giving the maximum weighted MER is j, and the threshold determination value of the carrier symbol Select.

[Weight coefficient calculation unit]
Next, the weight coefficient calculation unit 41 will be described. In the OFDM signal combining receiver 1 shown in FIG. 1 and the OFDM signal combining receiver 2 shown in FIG. 2, the weighting factor calculation unit 41 uses the carrier symbols and error signals corresponding to the number of array elements, and A weighting coefficient that minimizes the error signal is calculated. That is, a weighting coefficient that minimizes the evaluation function of the above-described equation (4) is calculated. Further, in the OFDM signal combining receiver 3 shown in FIG. 3 and the OFDM signal combining receiver 4 shown in FIG. 4, the weighting factor calculation unit 41 uses channel responses and error signals corresponding to the number of array elements. The weighting coefficient that minimizes the error signal is calculated. That is, a weighting coefficient that minimizes the evaluation function of the above-described equation (6) is calculated. However, even if an array composite signal is generated using the weighting factor calculated in this way, the desired wave is suppressed in some subcarriers due to miscapture that receives an interference wave instead of the desired wave. May end up. That is, in all subcarriers, there are cases where it is not sufficient to cancel the interference wave and extract the desired wave well. Therefore, by using the weighting coefficient calculation unit 41 described below, the interference wave is surely canceled and the desired wave is extracted.

  FIG. 13 is a diagram illustrating a configuration of the weighting factor calculation unit 41 in the OFDM signal combining receivers 1 and 2 illustrated in FIGS. 1 and 2. The weighting factor calculation unit 41 includes an optimization unit 401, a norm calculation unit 402, an averaging unit 403, a multiplication unit 404, a comparison unit 405, and a weighting factor replacement unit 406. The optimization unit 401 uses the carrier symbols for the number of array elements input from each FFT unit 10 and the error signal input from the subtraction unit 42 to calculate a weighting coefficient that minimizes the error signal. Output. The weighting factor of the main antenna reception system output from the optimization unit 401 is divided into two, one being input to the weighting factor replacement unit 406 and the other being input to the norm calculation unit 402. Further, the weighting factor of the auxiliary antenna reception system output from the optimization unit 401 is input to the weighting factor replacement unit 406.

  The norm calculation unit 402 receives the weighting factor of the main antenna reception system from the optimization unit 401, calculates the norm of the weighting factor for each subcarrier, and outputs it. The norm of the weight coefficient for each subcarrier output from the norm calculation unit 402 is divided into two, one being input to the comparison unit 405 and the other being input to the averaging unit 403.

  Averaging section 403 receives the norm of the weighting coefficient for each subcarrier from norm calculating section 402, and calculates and outputs the average value of the norms of the weighting coefficients of all subcarriers. Multiplier 404 receives an average value in the norm of the weight coefficients of all subcarriers from averaging unit 403, multiplies this average value by a predetermined constant, and outputs the multiplication result as a threshold value.

  The comparison unit 405 compares the norm of the weighting factor for each subcarrier calculated by the norm calculation unit 402 with the threshold value multiplied by the multiplication unit 404 for each subcarrier, and outputs a comparison result.

  The weighting factor replacement unit 406 receives the weighting factor for each subcarrier of the main antenna reception system and the auxiliary antenna reception system from the optimization unit 401, inputs the comparison result for each subcarrier from the comparison unit 405, and the comparison result is The subcarrier whose weight coefficient norm is smaller than the threshold value in the comparison unit 405 is identified, and among the weight coefficients of all subcarriers in the main antenna reception system and the auxiliary antenna reception system input from the optimization unit 401, The weight coefficient of the identified subcarrier is replaced with a predetermined weight coefficient. Specifically, the weighting coefficient of the subcarrier is replaced with the weighting coefficient of the adjacent subcarrier, the weighting coefficient obtained by the interpolation, or the weighting coefficient as a predetermined initial value. In this way, the weighting factor replacement unit 406 determines a predetermined subcarrier weighting factor indicated by the comparison result input from the comparison unit 405 out of the weighting factors of all subcarriers of all systems input from the optimization unit 401. Replace with weighting coefficient and output.

  The weighting factor output from the weighting factor replacing unit 406 is distributed into three and input to the carrier symbol combining units 30 and 51 and the channel response combining unit 72, respectively. 13 can be applied to the OFDM signal synthesis receivers 3 and 4 shown in FIGS. 3 and 4 by using the input signal as a channel response.

  FIG. 14 is a conceptual diagram illustrating a state in which interference waves are removed. Here, the D / U of the main antenna reception system is 10 dB, and the D / U of the auxiliary antenna reception system is −10 dB. An AGC (Automatic Gain Control) unit (not shown) in the OFDM signal combining receivers 1 to 4 of FIGS. 1 to 4 performs gain adjustment so that the power of the input signal becomes a predetermined power value. Specifically, the AGC unit performs gain adjustment on the basis of the desired wave received power in the main antenna reception system and on the basis of the interference wave reception power in the auxiliary antenna reception system. In this case, as shown in FIG. 14, the interference wave can be ideally removed by setting the weight coefficient of the main antenna reception system to 1 and the weight coefficient of the auxiliary antenna reception system to -0.1. Since it is assumed that the D / U of the main antenna reception system is always positive, the norm of the weight coefficient for the auxiliary antenna reception system must always be smaller than the norm of the weight coefficient for the main antenna reception system.

  FIG. 15 is a diagram for explaining a state in which interference waves are removed in all subcarriers. The optimum weighting factor under the reception conditions in FIG. 14 is represented on a complex plane. The left side is a diagram showing the weighting factor of the main antenna receiving system, and the right side is the diagram showing the weighting factor of the auxiliary antenna receiving system. As shown in FIG. 15, considering the phase terms for all subcarriers, the weighting factor is considered to be on a circumference having a certain amplitude. It can also be seen that the circle based on the weighting factor of the main antenna receiving system exists outside the circle based on the weighting factor of the auxiliary antenna receiving system (having a large diameter).

  FIG. 16 is a conceptual diagram for explaining a state in which a miscapture occurs in which an interference wave is received instead of the desired wave (the interference wave is regarded as the desired wave). The interference wave is received and the desired wave is removed. It shows how it is. Here, as in FIG. 14, the case where the D / U of the main antenna reception system is 10 dB and the D / U of the auxiliary antenna reception system is −10 dB is shown. As shown in FIG. 16, the desired wave is removed by setting the weighting factor of the main antenna receiving system to -0.1 and the weighting factor of the auxiliary antenna receiving system to 1. In this case, the norm of the weighting factor for the auxiliary antenna receiving system is larger than the norm of the weighting factor for the main antenna receiving system.

  FIG. 17 is a diagram for explaining a state in which miscapture has occurred in some subcarriers. The weighting factor under the reception conditions in FIG. 16 is represented on a complex plane. The left side is a diagram showing the weighting factor of the main antenna receiving system, and the right side is the diagram showing the weighting factor of the auxiliary antenna receiving system. As shown in FIG. 17, there are two circles with different weighting coefficient sizes in the main antenna reception system, and there are also two circles in the auxiliary antenna reception system. The subcarriers where miscapture has occurred are the circle with the smaller diameter among the weighting factors of the main antenna receiving system (left figure) and the circle with the larger diameter among the weighting coefficients of the auxiliary antenna receiving system (right figure). expressed. The weighting factor on the circumference with a large diameter among the weighting factors of the main antenna receiving system means that the desired wave is received, and the weighting factor on the circumference with a small diameter represents the interference wave. It means that you are receiving.

ここで、ｗ_ｋ，０はサブキャリヤ番号ｋにおける主アンテナ受信系統の重み係数、βは予め決められた定数であり、０＜β＜１の範囲の実数である。つまり、図１３に示した平均化部４０３および乗算部４０４は、式（４４）のしきい値を算出し、比較部４０５は、このしきい値を用いてサブキャリヤ毎の比較を行う。 Therefore, when the weighting factor of the main antenna receiving system is on the circle having a small diameter on the complex plane, it is considered that the subcarrier has caused miscapture. Whether or not this miscapture has occurred is determined by comparing the norm of the weighting factor of the main antenna reception system with the threshold given by the following equation.

Here, w _{k, 0} is a weighting factor of the main antenna receiving system at subcarrier number k, β is a predetermined constant, and is a real number in the range of 0 <β <1. That is, averaging section 403 and multiplication section 404 shown in FIG. 13 calculate the threshold value of equation (44), and comparison section 405 performs comparison for each subcarrier using this threshold value.

Also, when the weighting factor replacement unit 406 shown in FIG. 13 determines that miscapture has occurred (when there is a subcarrier whose weighting factor is smaller than the threshold value in the comparison unit 405), for example, As shown in the following equation, the interpolation coefficient is interpolated by using the weighting coefficient of the adjacent subcarrier, and the weighting coefficient of the subcarrier is replaced.

Further, when it is determined that the subcarrier adjacent to the subcarrier causing the miscapture also causes the miscapture (the sub-carrier having a weighting factor smaller than the threshold exists in the comparison unit 405, Are adjacent to each other), using w _k−1 , w _{k + 1} or w ₀ (initial value) instead of (w _k−1 + w _{k + 1} ) / 2 in equation (45), miscapture Replace with a weighting factor that does not occur.

  As described above, according to the weighting factor calculation unit 41 shown in FIG. 13, the weighting factor of the subcarrier that causes miscapture is replaced with the weighting factor that does not cause miscapture. Is suppressed, and interference waves can be canceled and desired waves can be extracted well in all subcarriers.

[Repeater]
FIG. 12 is a block diagram showing a configuration of a relay apparatus using the OFDM signal combining receivers 1, 2, 3, and 4 shown in FIGS. This relay device 501 is for OFDM signal synthesis of any one of an external reception antenna 502, feeder cables 503 and 512, a reception filter 504, a reception unit 505, and OFDM signal synthesis receivers 1, 2, 3, and 4. A receiving device, a determination unit 506, an IFFT (Inverse Fast Fourier Transform) unit 507, a GI adding unit 508, an external transmission unit 509, a PA 510, a transmission filter 511, and a transmission antenna 513 are provided.

  The desired wave (OFDM wave) transmitted from the master station is received by the plurality of receiving antennas 502 in the relay apparatus 501 of the broadcast wave relay station. The plurality of reception filters 504 input reception signals from the plurality of reception antennas 502 through the feeder cable 503, and remove unnecessary signal components outside the frequency band of the desired wave. The plurality of receiving units 505 input the output signals of the reception filters 504 corresponding to the number of reception antennas 502, respectively, AGC-amplify the output levels so as to be constant, and then perform frequency conversion to output IF signals. As the center frequency of this IF signal, 37.15 MHz is generally used.

  The IF signals output from the receiving units 505 corresponding to the number of receiving antennas 502 are input to the OFDM signal combining receivers 1, 2, 3, and 4. The frequency converters (not shown) of the OFDM signal synthesis receivers 1, 2, 3, and 4 frequency-convert the input IF signal, convert it to a second IF signal, and output it. As the center frequency of the second IF signal, 512/63 (8.127689...) MHz is generally used. An A / D converter (not shown) receives the second IF signal from the frequency converter, performs A / D conversion, and outputs a digital IF signal. A quadrature demodulator (not shown) receives the digital IF signal from the A / D converter, performs quadrature demodulation processing, converts it into a complex baseband signal, and outputs it. The FFT unit receives a complex baseband signal from the quadrature demodulator, performs FFT, and outputs a carrier symbol. The carrier symbol output from the FFT unit is subjected to array combining processing, and multipath distortion and an interference wave in the same frequency band as the desired wave are removed from the input signal and output.

  The determiner 506 receives the output signal of the OFDM signal combining receivers 1, 2, 3, and 4 and estimates and outputs a transmission symbol by threshold determination processing for each subcarrier of the OFDM signal. The IFFT unit 507 receives the carrier symbol from the determiner 506, performs IFFT processing, and converts it into a time domain signal. GI adding section 508 receives the time domain signal from IFFT section 507 and adds a GI to the head of the OFDM symbol. The quadrature modulator (not shown) performs quadrature modulation processing on the complex baseband signal input from the GI adding unit 508, converts the signal into a digital IF signal, and outputs the digital IF signal. A D / A converter (not shown) converts the digital IF signal input from the quadrature modulator into a second IF signal and outputs the second IF signal. A frequency converter (not shown) converts the second IF signal input from the D / A converter into an IF signal and outputs the IF signal.

  The transmission unit 509 converts the IF signal input from the frequency conversion unit into an RF band, amplifies the signal to a certain level, and outputs the amplified signal. The PA 510 amplifies and outputs the RF signal input from the transmission unit 509 in order to obtain a transmission signal having a desired output. The transmission filter 511 removes unnecessary radiation components outside the band from the transmission signal input from the PA 510. The transmission signal from which unnecessary components outside the band are removed by the transmission filter 511 is supplied to the transmission antenna 513 through the feeder cable 512 and radiated as a radio wave.

  Although the relay apparatus 501 shown in FIG. 12 includes the determination unit 506, it is not always necessary. The threshold determination process by the determiner 506 is a process of replacing with a known transmission symbol closest to the input carrier symbol. This process has the advantage that residual errors in interference removal and white noise uncorrelated between elements can be removed, but this is not always necessary.

It is a block diagram which shows the 1st structure of the receiver for OFDM signal synthesis by embodiment of this invention. It is a block diagram which shows the 2nd structure of the receiver for OFDM signal synthesis by embodiment of this invention. It is a block diagram which shows the 3rd structure of the receiver for OFDM signal synthesis by embodiment of this invention. It is a block diagram which shows the 4th structure of the receiver for OFDM signal synthesis by embodiment of this invention. It is a figure explaining the outline | summary of the receiver for OFDM signal synthesis | combination. It is a figure explaining the outline | summary of the other receiving apparatus for OFDM signal synthesis | combination. It is a figure explaining arrangement | positioning of SP. It is a figure which shows the structure of a channel estimation part. It is a figure which shows the structure of an array synthetic | combination part. It is a figure explaining the weighting factor calculation method by optimization. It is a figure explaining a phase identification algorithm. It is a figure which shows the structure of the relay apparatus using the receiver for OFDM signal synthesis | combination of FIGS. It is a figure which shows the structure of a weighting coefficient calculation part. It is a conceptual diagram explaining the state from which an interference wave is removed. It is a figure explaining the weighting coefficient on a complex plane when an interference wave is removed. It is a conceptual diagram explaining the state in which the miss capture has arisen. It is a figure explaining the weighting coefficient on a complex plane when miscapture has arisen.

Explanation of symbols

1, 2, 3, 4, 101, 102 OFDM signal combining receiver 10 FFT unit 21, 22, 23, 24, 201, 202 Weight coefficient control unit 30, 51 Array combining unit (carrier symbol combining unit)
21, 121 Determination value calculator 41, 211, 215 Weight coefficient calculator 42, 213, 218 Subtractor 43, 713 Divider 45, 72, 216 Array combiner (channel response combiner)
46, 73 Desired response generation unit 50, 60 Reference signal calculation unit 52 Phase correction unit 53 Inter-carrier averaging unit 54 Channel equalization unit 55 Weighting synthesis unit 56 Threshold judgment unit 57 Modulation error ratio calculation unit 58, 302 Multiplication unit 59-1 maximum value detection unit 59-2 selection unit 61 error calculation unit 63 minimum value detection unit 70 phase identification unit 71, 214 channel estimation unit 74 phase correction value calculation unit 212, 217 reference signal generation unit 401 optimization unit 402 norm Calculation unit 403 Averaging unit 404 Multiplication unit 405 Comparison unit 406 Weight coefficient replacement unit 301 Complex conjugate unit 303 Addition unit 501 Relay device 502 Reception antenna 503, 512 Feeder cable 504 Reception filter 505 Reception unit 506 Determiner 507 IFFT unit 508 GI addition Unit 509 transmitting unit 510 PA
511 Transmission filter 513 Transmission antenna 711 Pilot extraction unit 712 Pilot generation unit 714 Interpolation unit

Claims (5)

An array receiver configured to receive and output an OFDM wave by an array antenna configured with one main antenna and one or more auxiliary antennas as array elements, and received OFDM signals for the number of array elements output from the array receiver. Is converted into carrier symbols, which are frequency domain signals, by FFT, and the number of FFT elements corresponding to the number of array elements to be output, and the carrier symbols output from the FFT sections are weighted and combined for each subcarrier of the OFDM signal. In an OFDM signal combining receiver having a first carrier symbol combining unit that generates and outputs an array combined signal, and a weighting factor control unit that controls a weighting factor used for the weighting combining,
The weight coefficient control unit includes:
Pilot extraction units for the number of array elements for extracting pilot signals transmitted by a predetermined symbol number and subcarrier number from carrier symbols for the number of array elements output from each FFT unit, transmissions with known amplitudes and phases A pilot generator for generating a pilot signal, and the received pilot signals for the number of array elements output from each pilot extractor are divided by the transmission pilot signals output from the pilot generator, and channel responses in each array element and each subcarrier are divided. Channel response calculation units for the number of array elements to be obtained, and channels corresponding to the number of array elements for obtaining channel responses in all subcarriers by interpolating the channel responses output from the channel response calculation units in the symbol direction and subcarrier direction. Channel estimation with response interpolator A channel response synthesizer that performs array synthesis using the weighting coefficient for each subcarrier of the OFDM signal, and a desired response that generates a desired channel response. A phase identification unit comprising: a generation unit; an array combined signal of channel responses output from the channel response combining unit; and a phase correction value calculating unit for obtaining a phase correction value to be corrected from a desired response output from the desired response generating unit; ,
A channel equalization unit that divides the carrier symbol output from the FFT unit in the main antenna reception system by the channel response output from the channel estimation unit in the main antenna reception system for each subcarrier of the OFDM signal; and the output of each FFT unit A plurality of second carrier symbol combining sections for combining the carrier symbols corresponding to the number of array elements using the weighting coefficients of the corresponding and adjacent subcarriers, and a plurality of arrays output from the plurality of carrier symbol combining sections. A vector composed of a plurality of phase correction units for multiplying a combined signal by a phase correction value for each weighting factor output from the phase identification unit, and a plurality of array combined signals output from the plurality of phase correction units. Multiplying a predetermined intercarrier averaging matrix and multiplying each component of the vector after multiplication An inter-carrier averaging unit that outputs a plurality of array composite signals after inter-carrier averaging processing, and a main antenna that the channel equalization unit outputs for each of the plurality of array composite signals output by the inter-carrier averaging unit A plurality of weighting combining units for weighting and combining with carrier symbols after channel equalization of the receiving system, and a plurality of threshold determining units for determining and outputting a plurality of combined signals output from the respective weighting combining units And an error is calculated by subtracting the combined signal output from each of the weighted combining units from the determination value output from each of the threshold determination units, and the plurality of errors and the plurality of outputs output from the respective threshold determination units A plurality of modulation error ratio calculation units that respectively calculate modulation error ratios using the determination values, and for each of the plurality of modulation error ratios output by each of the modulation error ratio calculation units A plurality of multipliers for multiplying a predetermined constant, and a determination value output from the threshold value determination unit that gives a maximum value from the modulation error ratios after the constant multiplication output from each of the multipliers, A reference signal calculation unit comprising a selection unit for outputting as a reference signal;
A weighting factor calculating unit that optimizes a weighting factor so that an error between the array combined signal output from the first carrier symbol combining unit and the reference signal output from the reference signal calculating unit is minimized. A receiving apparatus for synthesizing OFDM signals. In the OFDM signal combining receiver according to claim 1,
The reference signal calculation unit of the weight coefficient control unit, instead of the modulation error ratio calculation unit, the multiplication unit, and the selection unit,
A plurality of error calculation units for calculating an error by subtracting a combined signal output from each of the weighted combining units from a determination value output from each of the threshold determination units, and a plurality of errors output from the respective error calculation units. A plurality of multipliers for multiplying a predetermined constant with respect to and a determination value output from the threshold value determination unit for giving a minimum value among errors after constant multiplication output from each multiplier And an OFDM signal synthesizing receiver comprising a selection unit that outputs the reference signal. In the receiving apparatus for OFDM signal synthesis according to claim 1 or 2,
The weighting factor control unit, instead of the weighting factor calculation unit,
A division unit for calculating a channel response by dividing carrier symbols for the number of array elements output by each FFT unit by a reference signal output by the reference signal calculation unit for each subcarrier of the OFDM signal, and each division unit Channel response for the number of array elements to be output from the channel response combining unit that performs an array combining process using the weighting factor, a desired response generating unit that generates a desired response, and a desired response output from the desired response generating unit, An error calculation unit that calculates an error by subtracting the array response signal of the channel response output from the channel response synthesis unit, and a channel response value corresponding to the number of array elements output from each division unit and the error output from the error calculation unit And a weighting factor calculation unit for optimizing the weighting factor so that the error is minimized. . In the OFDM signal synthesis receiver according to any one of claims 1 to 3,
The weighting factor calculation unit of the weighting factor control unit includes:
An optimization unit that optimizes the weighting factor so as to minimize the error, and outputs a weighting factor in the receiving system of the main antenna and a weighting factor in the receiving system of the auxiliary antenna;
A norm calculation unit for calculating a norm for each subcarrier with respect to a weighting factor in the reception system of the main antenna output from the optimization unit;
An averaging unit that calculates an average value of all subcarriers for the norm of the weighting factor for each subcarrier output by the norm calculation unit;
A multiplier for multiplying a norm average value of the weighting coefficients output by the averaging unit by a predetermined constant and outputting a threshold value;
A comparison unit that compares a norm of a weighting factor for each subcarrier output from the norm calculation unit with a threshold value output from the multiplier, and outputs a comparison result;
Of the subcarriers whose norm of the weighting factor is smaller than the threshold value according to the comparison result output from the comparison unit, the weighting factor in the receiving system of the main antenna and the weighting factor in the receiving system of the auxiliary antenna output from the optimization unit And a weighting factor replacement unit that replaces the weighting factor of the subcarrier with any of a weighting factor of an adjacent subcarrier, a weighting factor obtained by interpolation, or a predetermined initial weighting factor. OFDM signal combining receiver.   A relay apparatus using the OFDM signal combining receiver according to any one of claims 1 to 4.

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