JP5235857B2 - OFDM signal combining receiver - Google Patents

Description

  The present invention relates to a receiver for OFDM signal synthesis for digital broadcasting or digital transmission using the OFDM system, and in particular, for countermeasures against fading and interference waves that are problematic when receiving radio waves in digital broadcasting or wireless LAN, etc. The present invention relates to a receiving apparatus for combining OFDM signals to which an adaptive array antenna technique or a diversity receiving technique is applied.

  As an adaptive array antenna technique for OFDM signals, for example, those described in Patent Documents 1 and 2 are known, and these are all intended to be applied to a broadcast wave relay device. Since an interference canceling apparatus for relaying broadcast waves using these techniques is a transmission-side facility, it is required to obtain a highly accurate interference canceling characteristic rather than performing processing with a low calculation amount. However, this broadcast wave relay interference canceller is not expected to be used in an extremely poor reception environment. In particular, the service area of the SFN (Single Frequency Network) environment is an environment that is affected by multipath waves that have a high level and are within the GI (Guard Interval) but have a long delay time. There is a problem that there are things that cannot be obtained. Another problem is that the number of weighting factors to be optimized is the product of the number of subcarriers and the number of branches, which increases the amount of calculation.

  On the other hand, when it is assumed that the above-described adaptive array technology for OFDM signals is applied to a receiver, in order to realize a reduction in cost, the receiver has a BER with a simpler configuration and less calculation amount. It is required that (Bit Error Rate) can be obtained and that it can operate in a worse reception environment.

  In a broadcast wave relay device, the minimum requirement is that a required BER is obtained after interference removal, and it is required how to suppress the deterioration of transmission characteristics due to interference. On the other hand, the receiving device in the service area only needs to obtain a required BER after interference cancellation. As described above, the requirements for the OFDM signal adaptive array technology are greatly different between the broadcast wave relay device and the reception device in the service area.

  On the other hand, Non-Patent Documents 1 and 2 describe a pre-FFT type adaptive array technology for OFDM signals that synthesizes signals in the time domain. The technique of Non-Patent Document 1 assumes mobile reception, and can suppress all incoming waves other than the desired wave. The technique of Non-Patent Document 2 assumes fixed reception, and can suppress only multipath waves whose delay time exceeds GI. All of these can be processed with a small amount of calculation.

  However, the techniques described in Non-Patent Documents 1 and 2 both use the feature of the OFDM signal that the GI is the same as the rear part of the effective symbol. For this reason, when the interference wave is the same method as the desired wave and the GI ratio is the same, there is a problem that the interference wave may not be suppressed. For example, if the symbol synchronization position or the frame synchronization position of the desired wave and the interference wave match, the desired wave and the interference wave cannot be distinguished, and the interference wave cannot be suppressed.

  On the other hand, there has been proposed an OFDM signal combining receiver described in Japanese Patent Application No. 2008-232846, which was filed by the same applicant as the present application and has not been published at the time of the present application. In this OFDM signal combining receiver, the array combining unit performs weighted combining in the time domain to generate an array combined signal, and the channel equalizing unit generates carrier symbols after channel equalization in the frequency domain. The control unit uses a time domain signal obtained by IFFT of a predetermined pilot signal or the like as a reference signal, and a weight coefficient used for array synthesis minimizes an error between the array synthesized signal and the reference signal. Is obtained by optimization. Thereby, processing can be performed with a low calculation amount, and interference waves can be effectively suppressed even in a poor reception environment.

Japanese Patent No. 3759448 JP 2005-295506 A

Satoshi Hori, Nobuyoshi Kikuma, Naoki Inagaki, “MMSE Adaptive Array Using Guard Interval in OFDM”, Theory of Science, J85-B (9): 1608-1615, Sep 2002 Satoshi Hori, Nobuyoshi Kikuma, Naoki Inagaki, “MMSE Adaptive Array for Fixed Reception for Suppressing Only Incoming Waves Exceeding Guard Interval”, IEICE, J86-B (9): 1934-1940, 2003

  However, this OFDM signal synthesizing receiver has resistance against a poor reception environment, but broadcasting starts when the broadcasting is stopped and only interference waves are transmitted. When the desired wave transmission starts, even if the received power of the desired wave is greater than the received power of the interference wave, the symbol synchronization position or the frame synchronization position of the desired wave and the interference wave match. Sometimes, there is a problem that the desired wave that should be received is suppressed and the interference wave is continuously received.

  FIG. 13 is a diagram illustrating an example of the combined directivity characteristics of the OFDM signal combining receiver in a state where only the interference wave is transmitted. This combined directivity characteristic is such that when the element spacing of the receiving antenna is half the wavelength at the carrier frequency and the arrival angle of the interference wave is 0 degrees, the broadcast is paused and only the interference wave is transmitted. The characteristics are shown. In this case, the receiving apparatus for synthesizing the OFDM signal establishes synchronization in a state where only the interference wave is received, and is in a synchronization established state, and thus demodulates the signal by regarding the interference wave as a desired wave.

  It is assumed that broadcasting starts in this state, transmission of the desired wave starts, and the received power of the desired wave is greater than the received power of the interference wave. However, the arrival angle of the desired wave is 90 degrees. In such a state, it is desirable for the OFDM signal combining receiver to receive the desired wave while suppressing the interference wave.

  However, if the symbol synchronization position or the frame synchronization position of the desired wave and the interference wave match, there will be no synchronization shift. Therefore, the OFDM signal synthesizing receiver has continuously established synchronization. Even if the desired wave has arrived, the interference wave is regarded as the desired wave and the signal is demodulated. That is, the OFDM signal synthesizing receiving apparatus operates so as to continue to receive the interference wave while the synchronization establishment state continues before the broadcast starts. Therefore, the interference wave cannot be suppressed and the desired wave cannot be received. This is because, as shown in the example of the combined directivity shown in FIG. 13, a null is formed at the arrival angle (90 degrees) of the desired wave, so the received power of the desired wave is greater than the received power of the interference wave. Even in this case, the desired wave is suppressed, and as a result, the interference wave is continuously received.

  Here, when the broadcast is paused and only the interference wave is transmitted, when the broadcast starts and the transmission of the desired wave starts, the OFDM signal combining receiver detects the state change. Then, if the synchronous reproduction unit can be initialized and the weighting factor calculation unit for calculating the weighting factor for performing array combining can be initialized, that is, the OFDM signal combining receiving device is set to the power-up state. If it is possible, the above-mentioned problem is solved, and it is possible to receive the desired wave while suppressing the interference wave without suppressing the desired wave that should be received. Here, initialization means performing the same processing at the time of power-up of the OFDM signal synthesis receiver, for example, without deleting the data stored in the memory or using the calculation result in advance. It means calculating from the beginning using the set initial value.

  If the symbol position of the desired wave does not match the symbol position of the interference wave, a synchronization error occurs. Therefore, the OFDM signal combining receiver determines that synchronization is not established, and the desired wave is reflected. New synchronization information can be generated and demodulated. In this case, since the desired wave is not suppressed, the interference wave is suppressed and the desired wave is received, the above problem does not occur.

  Therefore, the present invention has been made to solve such a problem, and the object thereof is to suppress the interference wave in order to receive the desired wave without continuously suppressing the desired wave to be received. Another object of the present invention is to provide an OFDM signal combining receiver.

  In order to achieve the above object, an invention according to claim 1 is an OFDM signal synthesizing receiver that receives an OFDM wave by an array antenna including a plurality of array elements and outputs a bit string. The equivalent baseband signal is synthesized by weighting in the time domain to generate an array synthesized signal, and the desired signal receiving array synthesizing unit, and the array synthesized signal generated by the desired signal receiving array synthesizing unit are demodulated, and a bit string Generating a time domain reference signal based on the frequency characteristic obtained by channel demodulation and the carrier symbol obtained by channel equalization or symbol reproduction in the demodulation unit, and the array combined signal And the reference signal in the time domain are optimized so that the error is minimized, A weighting factor calculating unit for calculating a weighting factor for receiving a desired wave for suppressing an interference wave, used for weighting in the unit, and reproducing synchronization based on the equivalent baseband signal in the time domain to establish synchronization. A synchronization reproduction unit that generates a synchronization establishment state signal indicating whether or not a D / U measurement unit that measures a D / U (Desired to Undesired signal ratio) based on the equivalent baseband signal in the time domain, Based on the synchronization establishment state signal generated by the synchronization reproduction unit, it is determined that synchronization is established, the D / U measured by the D / U measurement unit is determined to be negative, And a control unit for initializing the weighting coefficient calculation unit and the synchronous reproduction unit.

  Further, the invention of claim 2 is the OFDM signal combining receiver according to claim 1, wherein the D / U measurement unit is based on the desired wave reception weight coefficient calculated by the weight coefficient calculation unit. An interference wave reception weight coefficient calculating unit that calculates an interference wave reception weight coefficient for suppressing a desired wave, and using the interference wave reception weight coefficient calculated by the interference wave reception weight coefficient calculation unit, An equivalent baseband signal is synthesized by weighting in the time domain to generate an array composite signal, and an array signal for interference wave reception and the power of the array composite signal generated by the array synthesis unit for desired signal reception A desired wave power calculation unit that calculates as the interference wave power, and an interference wave power calculation unit that calculates, as the interference wave power, the power of the array combined signal generated by the interference wave receiving array combining unit, Characterized by comprising a D / U calculation unit from the interference wave power calculated by the desired signal power is calculated and the interference wave power calculation unit by the wave power calculation unit for calculating a D / U, a.

  The invention according to claim 3 is the OFDM signal combining receiver according to claim 1, wherein the weighting factor calculation unit calculates an autocorrelation matrix in the time domain equivalent baseband signal. An inverse matrix calculation unit that calculates an inverse matrix of the autocorrelation matrix calculated by the autocorrelation matrix calculation unit, and a cross correlation vector that calculates a cross correlation vector from the time domain equivalent baseband signal and the time domain reference signal A correlation vector calculation unit and a multiplication unit for multiplying the inverse matrix of the autocorrelation matrix calculated by the inverse matrix calculation unit by the cross correlation vector calculated by the cross correlation vector calculation unit to obtain a desired wave reception weight coefficient And.

  According to a fourth aspect of the present invention, there is provided the OFDM signal synthesizing receiver according to the second aspect, wherein the interference wave receiving weighting factor calculating unit of the D / U measuring unit is calculated by the weighting factor calculating unit. An orthogonal vector calculation unit that calculates an orthogonal vector orthogonal to a wave reception weighting factor, and the orthogonal vector calculated by the orthogonal vector calculation unit is multiplied by an inverse matrix of an autocorrelation matrix in the time domain equivalent baseband signal. And a multiplication unit for obtaining a weighting factor for interference wave reception.

  The invention according to claim 5 is the OFDM signal combining receiver according to claim 1, wherein the synchronization reproduction section performs symbol synchronization reproduction based on the time domain equivalent baseband signal to establish symbol synchronization. A status signal indicating whether or not frame synchronization is established by performing a frame synchronization reproduction based on the time base equivalent baseband signal and a symbol synchronization unit for generating a status signal indicating whether or not A frame synchronization unit, a clock synchronization unit that performs clock synchronization recovery based on the time domain equivalent baseband signal and generates a status signal indicating whether clock synchronization is established, and the time domain equivalent baseband signal. A frequency synchronization unit that performs frequency-synchronized reproduction based on the signal and generates a status signal indicating whether or not frequency synchronization is established; and Synchronization status signal indicating that synchronization is established when all status signals generated by the synchronization unit, frame synchronization unit, clock synchronization unit, and frequency synchronization unit indicate that synchronization is established And a synchronization establishment state generation unit that generates a synchronization establishment state signal indicating that synchronization is not established when at least one of the state signals indicates that synchronization is not established. And.

  According to a sixth aspect of the present invention, in the OFDM signal synthesizing receiver according to the first aspect, the demodulating unit performs MER (Modulation) based on a carrier symbol obtained by channel equalization and a carrier symbol obtained by symbol reproduction. Error Ratio) is calculated, the control unit determines that synchronization is established based on the synchronization establishment state signal generated by the synchronization reproduction unit, and is measured by the D / U measurement unit. When it is determined that the D / U is negative for a predetermined period, it is determined based on the synchronization establishment state signal that synchronization is not established, and the synchronization is not established. When it is determined that time has elapsed, or based on the synchronization establishment state signal, it is determined that synchronization is established, and the demodulation unit Based on the calculated MER, when it is determined that the MER is smaller than a predetermined value for a predetermined period, the weight coefficient calculation unit and the synchronous reproduction unit are initialized.

  As described above, according to the present invention, the change from the state in which only the interference wave is transmitted to the state in which the transmission of the desired wave starts and the reception power of the desired wave becomes larger than the reception power of the interference wave. Detecting and initializing the weighting factor calculation unit and the synchronous reproduction unit. As a result, the receiving apparatus for OFDM signal synthesis operates in the same manner as when the power is turned on, so that the weighting factor calculation unit outputs and receives a desired initial receiving weighting factor for the initial value. A new desired wave receiving weighting coefficient corresponding to the desired wave and the interference wave is calculated. Further, the desired wave receiving array combining unit generates an array combined signal corresponding to the received desired wave using a new desired wave receiving weighting coefficient. In addition, the synchronous reproduction unit resets the synchronous reproduction process and performs new synchronous reproduction according to the received desired wave and interference wave. Accordingly, it is possible to suppress the interference wave in order to receive the desired wave without suppressing the desired wave that should be received.

It is a block diagram which shows the structure of the receiver for OFDM signal synthesis by embodiment of this invention. It is a block diagram which shows the structure of a demodulation part. It is a block diagram which shows the structure of a channel estimation part. It is a block diagram which shows the structure of a channel equalization part. It is a block diagram which shows the structure of a weighting coefficient calculation part. It is a block diagram which shows the structure of the weighting coefficient calculation part for interference wave reception. It is a block diagram which shows the structure of a synchronous reproduction | regeneration part. It is a block diagram which shows the structure of a symbol synchronizer. It is a figure explaining the transition of the index produced | generated in a symbol synchronization part. It is a flowchart which shows the process of a control part. It is a figure explaining the simulation result by the receiver for OFDM signal synthesis of FIG. (1) is a figure explaining the operation | movement at the normal time. (2) is a diagram for explaining the operation when the desired wave is stopped (when broadcasting is suspended). (3) is a diagram for explaining the operation after the start of desired wave transmission (after the start of broadcasting) (the problem to be solved by the present invention). It is a figure which shows the example of the synthetic | combination directional characteristic of the receiver for OFDM signal synthesis | combination in the state in which only the interference wave is transmitted.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an OFDM signal combining receiver according to an embodiment of the present invention. This OFDM signal combining receiver 1 includes an antenna 10, a frequency converting unit 11, an A / D converting unit 12, an orthogonal demodulating unit 13, a desired wave receiving array combining unit 14, a D / U (Desired to Unsigned signal ratio: DU). Ratio) measuring unit 15, demodulating unit 16, weighting factor calculating unit 17, synchronous reproduction unit 18 and control unit 19. The frequency conversion unit 11, the A / D conversion unit 12, and the orthogonal demodulation unit 13 have the same number of configurations as the array elements of the antenna 10.

  Frequency converters 11 corresponding to the number of array elements frequency-convert OFDM signal received through antenna 10 into IF signals. The IF signals output from the frequency converters 11 corresponding to the number of array elements are respectively input to the A / D converter 12. The A / D converters 12 corresponding to the number of array elements A / D convert the IF signals input from the frequency converter 11 into digital IF signals. The digital IF signals output from the A / D converters 12 corresponding to the number of array elements are respectively input to the orthogonal demodulator 13. The number of orthogonal demodulation units 13 corresponding to the number of array elements orthogonally demodulates the digital IF signal input from the A / D conversion unit 12 to generate an equivalent baseband signal. The equivalent baseband signals output from the quadrature demodulation units 13 corresponding to the number of array elements are divided into four and input to the desired wave receiving array combining unit 14, the D / U measuring unit 15, the weighting factor calculating unit 17, and the synchronous reproduction unit 18. The

  The desired wave receiving array synthesizing unit 14 uses the desired wave receiving weight coefficient (weight coefficient for suppressing the interference wave component) input from the weight coefficient calculating unit 17, and the orthogonal demodulation units 13 corresponding to the number of array elements. The equivalent baseband signal input from is synthesized in the time domain. An equivalent baseband signal (equivalent baseband signal including a desired wave component, array synthesized signal) which is array-synthesized for receiving a desired wave output from the desired-wave receiving array synthesizing unit 14 is divided into two parts, one of which is D / U measurement. The other part is input to the demodulator 16.

  The desired wave receiving array synthesizing unit 14 includes a multiplying unit 141, an adding unit 142, and a complex conjugate unit 143 corresponding to the number of array elements. The complex conjugate unit 143 calculates the complex conjugate value of the desired wave reception weight coefficient input from the weight coefficient calculation unit 17. The complex conjugate value of the desired wave receiving weight coefficient output from the complex conjugate section 143 is input to the multiplication sections 141 corresponding to the number of array elements. Multipliers 141 corresponding to the number of array elements multiply the equivalent baseband signals input from orthogonal demodulator 13 corresponding to the number of array elements by the complex conjugate value of the desired wave reception weight coefficient input from complex conjugate section 143. . The equivalent baseband signal multiplied by the complex conjugate value of the weighting coefficient for receiving the desired wave, which is output from the multipliers 141 corresponding to the number of array elements, is input to the adder 142. Adder 142 adds the equivalent baseband signal multiplied by the complex conjugate value of the desired wave reception weighting coefficient output from multiplier 141 for the number of array elements, and is equivalent to an equivalent base array synthesized for receiving the desired wave Generate a band signal. The equivalent baseband signal array-synthesized for receiving the desired wave output from the adder 142 is divided into two, one being input to the D / U measuring unit 15 and the other being input to the demodulator 16.

  The D / U measurement unit 15 includes an equivalent baseband signal that is array-synthesized for receiving a desired wave, which is input from the array unit for receiving desired signals 14, a weighting factor for receiving desired waves that is input from a weighting factor calculating unit 17, The D / U of the received signal is measured using the inverse matrix of the autocorrelation matrix. The D / U output from the D / U measuring unit 15 is input to the control unit 19.

  The D / U measuring unit 15 includes an interference wave receiving weight coefficient calculating unit 151, an interference wave receiving array combining unit 152, a desired wave power calculating unit 153, an interference wave power calculating unit 154, and a D / U calculating unit 155. Yes. The desired wave power calculation unit 153 calculates the power of the equivalent baseband signal array-combined for receiving the desired wave input from the desired wave reception array combining unit 14. The desired wave power output from the desired wave power calculation unit 153 is input to the D / U calculation unit 155.

  The interference wave reception weight coefficient calculation unit 151 uses the desired wave reception weight coefficient input from the weight coefficient calculation unit 17 and the inverse matrix of the autocorrelation matrix to interfere with the desired wave component by array synthesis. A reception weight coefficient is calculated. The interference wave reception weight coefficient (weight coefficient for suppressing the desired wave component) output from the interference wave reception weight coefficient calculation unit 151 is input to the interference wave reception array combining unit 152.

  The interference wave receiving array synthesizing unit 152 uses the desired wave receiving weight coefficient input from the interference wave receiving weight coefficient calculating unit 151 and uses the equivalent baseband signal input from the orthogonal demodulating units 13 corresponding to the number of array elements. Are synthesized in the time domain. The equivalent baseband signal (equivalent baseband signal including an interference wave component, array combined signal) synthesized for interference wave reception output from the interference wave reception array synthesis unit 152 is input to the interference wave power calculation unit 154. .

  The interference wave receiving array synthesizing unit 152 includes multiplying units 157, adding units 158, and complex conjugate units 159 corresponding to the number of array elements. The complex conjugate unit 159 calculates a complex conjugate value of the interference wave reception weight coefficient input from the interference wave reception weight coefficient calculation unit 151. The complex conjugate value of the interference wave receiving weight coefficient output from the complex conjugate unit 159 is input to the multiplication units 157 corresponding to the number of array elements. Multipliers 157 for the number of array elements multiply the equivalent baseband signals input from orthogonal demodulator 13 for the number of array elements by the complex conjugate value of the interference wave receiving weight coefficient input from complex conjugate section 159. . The equivalent baseband signal multiplied by the complex conjugate value of the interference wave receiving weighting coefficient output from the multipliers 157 corresponding to the number of array elements is input to the adder 158. Adder 158 adds equivalent baseband signals multiplied by the complex conjugate value of the interference wave reception weight coefficient output from multipliers 157 for the number of array elements, and is equivalent to an equivalent base array-combined for interference wave reception. Generate a band signal. The equivalent baseband signal array-combined for receiving the interference wave output from the adder 158 is input to the interference wave power calculator 154.

  The interference wave power calculation unit 154 calculates the power of an equivalent baseband signal that is array-synthesized for interference wave reception and input from the interference wave reception array synthesis unit 152. The interference wave power output from the interference wave power calculation unit 154 is input to the D / U calculation unit 155.

  The D / U calculation unit 155 calculates the D / U of the received signal using the desired wave power input from the desired wave power calculation unit 153 and the interference wave power input from the interference wave power calculation unit 154. The D / U output from the D / U calculation unit 155 is input to the control unit 19.

  The demodulating unit 16 uses the synchronization information input from the synchronization reproducing unit 18 to OFDM-demodulate the equivalent baseband signal array-combined for receiving the desired wave input from the array combining unit 14 for receiving the desired wave, Is output to the outside, and the carrier symbol after channel equalization, frequency characteristics, and MER (Modulation Error Ratio) are calculated. The carrier symbol and frequency characteristic output from the demodulator 16 are input to the weight coefficient calculator 17 and the MER is input to the controller 19.

  The weighting factor calculation unit 17 calculates an inverse matrix of the autocorrelation matrix using the equivalent baseband signals input from the orthogonal demodulation units 13 corresponding to the number of array elements, and is input from the equivalent baseband signal and demodulation unit 16. Using the carrier symbol and the frequency characteristic, a desired wave receiving weight coefficient is calculated. Also, the weighting factor calculation unit 17 resets and initializes the processing based on the initialization control signal input from the control unit 19 and sets in advance in the same manner as when the power of the OFDM signal combining receiver 1 is turned on. The initial value of the desired wave receiving weight coefficient and the inverse matrix of the autocorrelation matrix are output. One of the desired wave receiving weight coefficients output from the weight coefficient calculating unit 17 is input to the desired wave receiving array combining unit 14, and the other is input to the D / U measuring unit 15. Further, the inverse matrix of the autocorrelation matrix output from the weight coefficient calculation unit 17 is input to the D / U measurement unit 15.

  The synchronous reproduction unit 18 performs synchronous reproduction using the equivalent baseband signals input from the orthogonal demodulation units 13 corresponding to the number of array elements, generates synchronous information indicating the timing of the frame, symbol, clock, and frequency offset, A synchronization establishment state signal indicating the establishment state or the synchronization non-establishment state is generated. The synchronous reproduction unit 18 resets and initializes the processing based on the initialization control signal input from the control unit 19, and performs the same processing as when the OFDM signal synthesizing receiver 1 is turned on. The synchronization establishment state signal output from the synchronization reproduction unit 18 is input to the control unit 19, and the synchronization information is input to the demodulation unit 16.

  The control unit 19 uses a synchronization establishment state signal input from the synchronization reproduction unit 18, a D / U input from the D / U measurement unit 15, and a MER input from the demodulation unit 16 to set a predetermined condition. Is satisfied, and an initialization control signal for initializing the weighting factor calculation unit 17 and the synchronous reproduction unit 18 is generated. One of the initialization control signals output from the control unit 19 is input to the weight coefficient calculation unit 17 and the other is input to the synchronous reproduction unit 18. The conditions for generating the initialization control signal will be described later.

ここで、ｔは時刻、Ｌはアンテナ１０のアレー素子数を示す。また、上付きのＴは転置を示す。 [Synthesizer for receiving desired signal]
Next, the desired wave receiving array combining unit 14 shown in FIG. 1 will be described in detail. Vectors of equivalent baseband signals output from the orthogonal demodulation units 13 corresponding to the number of array elements are shown below.

Here, t represents time, and L represents the number of array elements of the antenna 10. Superscript T indicates transposition.

希望波受信用アレー合成部１４は、以下の演算を行い、アレー合成信号として希望波受信用にアレー合成された等価ベースバンド信号を出力する。

ここで、上付きのＨは複素共役転置を示す。ｙ（ｔ）は、干渉波が抑圧され希望波成分が抽出されたアレー合成信号である。なお、前記式（３）には、図１に示した複素共役部１４３による処理が含まれる。 The vector of the desired wave receiving weighting coefficient output from the weighting coefficient calculating unit 17 is shown below.

The desired wave receiving array synthesizing unit 14 performs the following calculation and outputs an equivalent baseband signal array-synthesized for receiving the desired wave as an array synthesized signal.

Here, the superscript H indicates complex conjugate transpose. y (t) is an array composite signal in which the interference wave is suppressed and the desired wave component is extracted. The equation (3) includes processing by the complex conjugate unit 143 shown in FIG.

[Interference wave receiving array combiner]
Next, the interference wave receiving array combining unit 152 of the D / U measuring unit 15 shown in FIG. 1 will be described in detail. The interference wave receiving array combining unit 152 performs the same processing as the desired wave receiving array combining unit 14. The vector of the interference wave reception weight coefficient output from the interference wave reception weight coefficient calculation unit 151 is shown below.

ｚ（ｔ）は、希望波が抑圧され干渉波成分が抽出されたアレー合成信号である。なお、前記式（５）には、図１に示した複素共役部１５９による処理が含まれる。 The interference wave receiving array combining unit 152 performs the following calculation, and outputs an equivalent baseband signal that is array combined for interference wave reception as an array combined signal.

z (t) is an array combined signal in which the desired wave is suppressed and the interference wave component is extracted. The expression (5) includes processing by the complex conjugate unit 159 shown in FIG.

(Demodulator)
Next, the demodulator 16 shown in FIG. 1 will be described in detail. FIG. 2 is a block diagram showing the configuration of the demodulator 16. The demodulation unit 16 includes a GI removal unit 161, an FFT unit 162, a channel estimation unit 163, a channel equalization unit 164, a symbol reproduction unit 169, a parallel / serial conversion unit 166, and a MER calculation unit 168. The demodulating unit 16 performs various processes based on the synchronization information input from the synchronous reproduction unit 18.

  The GI removal unit 161 removes the GI from the equivalent baseband signal array-combined for receiving a desired wave input from the desired-wave reception array combining unit 14 and extracts a signal having a time corresponding to an effective symbol period. The equivalent baseband signal that is array-combined for receiving the desired wave in the effective symbol period and that is output from the GI removal unit 161 is input to the FFT unit 162.

  The FFT unit 162 converts the equivalent baseband signal array-combined for receiving the desired wave in the effective symbol period output from the GI removal unit 161 into a carrier symbol that is a frequency domain signal by FFT. The carrier symbols output from the FFT unit 162 are divided into two, one being input to the channel estimation unit 163 and the other being input to the channel equalization unit 164.

  Channel estimation section 163 estimates frequency characteristics (channel response) from the carrier symbols output from FFT section 162. The frequency characteristics output from the channel estimation unit 163 are divided into two, one being input to the channel equalization unit 164 and the other being input to the weighting factor calculation unit 17.

  The channel equalization unit 164 performs channel equalization by dividing the carrier symbol input from the FFT unit 162 by the frequency characteristic input from the channel estimation unit 163. The channel equalized carrier symbols output from the channel equalization unit 164 are divided into two, one input to the symbol reproduction unit 169 and the other input to the MER calculation unit 168.

  The symbol reproduction unit 169 includes a demapping unit 165 and a remapping unit 167. The demapping unit 165 demaps the carrier symbol after channel equalization output from the channel equalization unit 164 and converts it to a parallel signal. The parallel signal output from the demapping unit 165 is divided into two, one being input to the parallel-serial conversion unit 166 and the other being input to the remapping unit 167.

  The remapping unit 167 remaps the parallel signal input from the demapping unit 165 and generates a carrier symbol after reproduction. The reproduced carrier symbols output from the remapping unit 167 are divided into two, one being input to the MER calculation unit 168 and the other being input to the weighting factor calculation unit 17.

  Here, the demodulating unit 16 outputs the carrier symbol reproduced by the remapping unit 167 to the weighting factor calculating unit 17, but the carrier symbol that has been channel equalized by the channel equalizing unit 164 to the weighting factor calculating unit 17. You may make it output.

  The MER calculation unit 168 calculates MER using the channel equalized carrier symbol input from the channel equalization unit 164 and the reproduced carrier symbol input from the remapping unit 167. The MER output from the MER calculation unit 168 is input to the control unit 19.

  The parallel-serial conversion unit 166 converts the parallel signal input from the demapping unit 165 into a serial signal, and outputs the bit string to the outside.

(Channel estimation part)
Next, the channel estimation unit 163 shown in FIG. 2 will be described in detail. FIG. 3 is a block diagram illustrating a configuration of the channel estimation unit 163. The channel estimation unit 163 includes a pilot extraction unit 201, a pilot generation unit 202, a division unit 203, and an interpolation unit 204.

  Pilot extraction section 201 extracts a pilot signal transmitted as a carrier symbol having a predetermined symbol number and subcarrier number from the carrier symbols input from FFT section 162. The pilot signal output from pilot extraction section 201 is input to division section 203 as a received pilot signal.

  Pilot generating section 202 generates a pilot signal having a predetermined amplitude and phase. The pilot signal output from pilot generation section 202 is input to division section 203.

  Dividing section 203 divides the received pilot signal input from pilot extracting section 201 by the pilot signal input from pilot generating section 202, and obtains frequency characteristics in symbols and subcarriers in which the pilot signal is transmitted. The frequency characteristic output from the division unit 203 is input to the interpolation unit 204.

  Interpolation section 204 interpolates the frequency characteristics of the symbols and subcarriers transmitted from the pilot signal, which are input from division section 203, in the symbol direction and subcarrier direction, and calculates the frequency characteristics of all subcarriers of the OFDM signal. .

ただし、ｍｏｄは剰余を示す。以下、前記式（６）を満足するｉ，ｋをそれぞれｉ_ｐ，ｋ_ｐとする。 In the ISDB-T system, subcarriers assigned to SP (Scattered Pilot), which is a pilot signal, satisfy the following expression, where the symbol number is i and the subcarrier number is k.

However, mod indicates a remainder. In the following, i and k that satisfy the above equation (6) are assumed to be i _p and k _p , respectively.

Here, the pilot extraction unit 201 shown in FIG. 3 is an SP extraction unit, and the pilot generation unit 202 is an SP generation unit. The reception SP signal extracted by the SP extraction unit is X _{ip, kp,} and the SP signal generated by the SP generation unit, that is, the SP signal (transmission SP signal generated and transmitted by the ISDB-T modulator on the transmission side) ) Is S _{ip, kp} , the frequency characteristics U _{ip, kp at} symbol number i _p and subcarrier number k _p are expressed by the following equations.

  Here, the method of calculating the frequency characteristics using the SP signal employed in the ISDB-T system as a reference signal has been described. However, any signal that has a known amplitude and phase and can be generated on the receiving side is used. Similarly, it can be used as a reference signal for calculating frequency characteristics. That is, the present invention is not limited to using the SP signal as the reference signal in calculating the frequency characteristics.

  By the way, when calculating the frequency characteristics using the SP signal, it is not possible to directly calculate the frequency characteristics of all symbols and subcarriers. In order to calculate the frequency characteristics of all symbols and subcarriers, it is necessary to perform interpolation processing in the symbol and subcarrier directions.

また、線形補間法を用いる場合、以下の式により補間処理を行う。

For the interpolation in the symbol direction performed by the interpolation unit 204, for example, the latest value holding method or the linear interpolation method can be used. When the latest value holding method is used, interpolation processing is performed using the following formula.

Further, when the linear interpolation method is used, interpolation processing is performed according to the following formula.

On the other hand, for interpolation in the subcarrier direction, for example, a linear interpolation method can be used, and interpolation processing is performed by the following equation.

(Channel Equalization Department)
Next, the channel equalization unit 164 shown in FIG. 2 will be described in detail. FIG. 4 is a block diagram showing the configuration of the channel equalization unit 164. As shown in FIG. The channel equalization unit 164 includes a division unit 211.

ここで、Ｚ_ｋはチャネル等化後のキャリヤシンボルを示す。 The division unit 211 performs channel equalization by dividing the carrier symbol X _k input from the FFT unit 162 by the frequency characteristic U _k input from the channel estimation unit 163 as in the following equation.

Here, Z _k represents a carrier symbol after channel equalization.

(Symbol playback part)
Next, the demapping unit 165 and the remapping unit 167 of the symbol reproduction unit 169 shown in FIG. 2 will be described in detail.

ただし、Ｔ_ｋは送信キャリヤシンボル、Ｎ_ｋは雑音成分を示す。 The demapping unit 165 estimates the transmitted carrier symbol from the carrier symbol after channel equalization input from the channel equalization unit 164, and extracts a parallel signal composed of a plurality of bits. The remapping unit 167 performs carrier modulation on the parallel signal (a parallel signal composed of a plurality of bits) input from the demapping unit 165 and reproduces a carrier symbol. Here, the formula (11) can be expressed by the following formula.

Here, T _k represents a transmission carrier symbol, and N _k represents a noise component.

ここで、ｄｅｃはマッピングおよび再マッピングを示す関数であり、具体的には、与えられたキャリヤシンボルとの間のノルムが最も小さい送信キャリヤシンボルを返す関数である。これにより、シンボル再生部１６９は、チャネル等化後のキャリヤシンボルをデマッピング部１６５にてデマッピングし、再マッピング部１６７にて再マッピングすることにより、送信キャリヤシンボルを得ることができる。 Therefore, when the noise component N _k is sufficiently small, it can be expressed by the following equation.

Here, dec is a function indicating mapping and remapping, and specifically, a function that returns a transmission carrier symbol having the smallest norm with respect to a given carrier symbol. Thereby, symbol reproduction section 169 can obtain a transmission carrier symbol by demapping carrier symbol after channel equalization by demapping section 165 and remapping by remapping section 167.

ここで、Ｋは全サブキャリヤ数を示す。なお、ＭＥＲの詳細については、下記の非特許文献を参照されたい。
ETR 290：Measurement guidelines for DVB Systems, ETSI Technical Report, may 1997 (MER calculation unit)
Next, the MER calculation unit 168 shown in FIG. 2 will be described in detail. The MER calculation unit 168 is defined by the following equation using the equalized carrier symbol Z _k input from the channel equalization unit 164 and the regenerated carrier symbol D _k input from the remapping unit 167. MER to be calculated is calculated.

Here, K indicates the total number of subcarriers. For details of MER, refer to the following non-patent literature.
ETR 290: Measurement guidelines for DVB Systems, ETSI Technical Report, may 1997

[Weight coefficient calculation unit]
Next, the weighting factor calculation unit 17 shown in FIG. 1 will be described in detail. FIG. 5 is a block diagram showing a configuration of the weighting factor calculation unit 17. The weight coefficient calculation unit 17 includes an autocorrelation matrix calculation unit 171, an inverse matrix calculation unit 172, a pilot insertion unit 173, a multiplication unit 174, an OFDM remodulation unit 175, a cross correlation vector calculation unit 176, and a multiplication unit 177. .

  The autocorrelation matrix calculation unit 171 calculates an autocorrelation matrix using the equivalent baseband signal input from the orthogonal demodulation units 13 for the number of array elements. The autocorrelation matrix output from the autocorrelation matrix calculation unit 171 is input to the inverse matrix calculation unit 172. The inverse matrix calculation unit 172 calculates an inverse matrix of the autocorrelation matrix input from the autocorrelation matrix calculation unit 171. The inverse matrix of the autocorrelation matrix output from the inverse matrix calculation unit 172 is divided into two, one being input to the multiplication unit 177 and the other being input to the D / U measurement unit 15.

  The pilot insertion unit 173 generates a new carrier symbol by inserting a known pilot signal into the carrier symbol input from the demodulation unit 16. Specifically, a carrier symbol assigned to a pilot signal among the carrier symbols is replaced with a carrier symbol of a known pilot signal. A new carrier symbol output from pilot insertion section 173 is input to multiplication section 174. Multiplication section 174 multiplies the new carrier symbol input from pilot insertion section 173 by the frequency characteristic input from demodulation section 16. The carrier symbol output from the multiplier 174 is input to the OFDM remodulator 175 as a frequency domain reference signal.

  Since the frequency domain reference signal output from the multiplier 174 is a signal calculated using the frequency characteristic, the reference signal includes the frequency characteristic. The weighting factor calculation unit 17 calculates a desired wave receiving weighting factor using this reference signal. Here, even in an environment where a multipath of a desired wave is received, the weighting factor calculating unit 17 calculates a desired wave receiving weighting factor by which the interference wave can be removed by the desired wave receiving array combining unit 14. be able to. That is, the interference wave is removed by the desired wave receiving array combining unit 14, and the frequency characteristic distortion due to multipath is equalized by the channel equalizing unit 164 of the demodulating unit 16. Thereby, the receiving apparatus 1 for OFDM signal synthesis can receive the OFDM signal satisfactorily.

  The OFDM remodulation unit 175 performs IFFT on the frequency domain reference signal input from the multiplication unit 174, and OFDM remodulates it to a time domain reference signal. The time domain reference signal output from OFDM remodulation section 175 is input to cross-correlation vector calculation section 176.

  Cross-correlation vector calculation section 176 calculates a cross-correlation vector using the equivalent baseband signal input from orthogonal demodulation sections 13 corresponding to the number of array elements and the reference signal input from OFDM remodulation section 175. The cross correlation vector output from the cross correlation vector calculation unit 176 is input to the multiplication unit 177.

Multiplier 177 multiplies the inverse matrix of the autocorrelation matrix input from inverse matrix calculator 172 by the cross-correlation vector input from cross-correlation vector calculator 176 to calculate a desired wave reception weight coefficient. One of the desired wave receiving weight coefficients output from the multiplier 177 is input to the desired wave receiving array combining unit 14 and the other is input to the D / U measuring unit 15.
It is.

ここで、Ｒ_０，Ｒ_１，・・・，Ｒ_Ｋ−１は周波数領域の参照信号を示し、ｒ（ｔ）は時間領域の参照信号を示す。 (Reference signal)
Next, details of the reference signal generated by OFDM remodulation section 175 shown in FIG. 5 will be described. The OFDM remodulator 175 converts the frequency domain reference signal input from the multiplier 174 into a time domain reference signal using IFFT. The OFDM remodulation unit 175 performs processing shown in the following equation.

Here, R ₀ , R ₁ ,..., R _K-1 represent frequency domain reference signals, and r (t) represents a time domain reference signal.

(Autocorrelation matrix, inverse matrix, cross-correlation vector, desired wave reception weight coefficient)
Next, the autocorrelation matrix calculated by the autocorrelation matrix calculation unit 171, the inverse matrix of the autocorrelation matrix calculated by the inverse matrix calculation unit 172, the cross correlation vector calculated by the cross correlation vector calculation unit 176, and the multiplication unit The desired wave reception weighting coefficient calculated by 177 will be described in detail.

また、希望波受信用にアレー合成された信号を以下の式に示す。

An input signal vector of an equivalent baseband signal input from the orthogonal demodulator 13 for the number of array elements is shown in the following equation.

A signal synthesized by array for receiving a desired wave is shown in the following equation.

  The weighting factor calculation unit 17 receives the desired wave so that the square error between the signal y (t) synthesized for receiving the desired wave of the equation (17) and the reference signal r (t) is minimized. Optimize the weighting factor.

ここで、Ｅ［・］は期待値演算を示す。 The square error is defined by the following equation.

Here, E [•] indicates an expected value calculation.

ここで、Ｒ_ｘｘはｘ（ｔ）の自己相関行列を示し、ｒ_ｘｒはｘ（ｔ）とｒ（ｔ）の相互相関ベクトルを示す。 The desired wave reception weighting coefficient w _opt that minimizes the square error of the equation (18) is expressed by the following equation.

Here, R _xx represents an autocorrelation matrix of x (t), and r _xr represents a cross-correlation vector of x (t) and r (t).

希望波受信用重み係数の更新間隔を例えば１シンボル間隔として、処理を行う。ただし、上付きの＊は複素共役を示す。 Here, the autocorrelation matrix and the cross-correlation vector are respectively expressed by the following equations,

The processing is performed with the update interval of the desired wave reception weighting coefficient set to, for example, one symbol interval. However, the superscript * indicates a complex conjugate.

ここで、ｎは、希望波受信用重み係数の更新時間を示す。また、λは、０≦λ＜１を満たす適応係数を示し、忘却係数と呼ばれる。さらに、前記式（２２）および（２３）における右辺の第２項の期待値演算は、希望波受信用重み係数の更新間隔、例えば１シンボルのうちで有効シンボル期間に相当する期間における期待値を示す。 That is, the autocorrelation matrix calculation unit 171 performs processing of the following formula (22) using the input signal vector x (t) of the equivalent baseband signal, and calculates the self-phase matrix R _xx (n). Further, the cross-correlation vector calculation unit 176 performs processing of the following equation (23) using the input signal vector x (t) and the reference signal r (t) of the equivalent baseband signal, and the cross-correlation vector r _xr ( n) is calculated.

Here, n represents the update time of the desired wave receiving weighting coefficient. Λ represents an adaptive coefficient that satisfies 0 ≦ λ <1 and is called a forgetting coefficient. Further, the expected value calculation of the second term on the right-hand side in the above equations (22) and (23) is the update interval of the desired wave receiving weighting coefficient, for example, the expected value in the period corresponding to the effective symbol period in one symbol. Show.

The inverse matrix calculation unit 172 calculates an inverse matrix R _xx ⁻¹ (n) of the self-phase matrix R _xx (n) calculated by the autocorrelation matrix calculation unit 171. The multiplier 177 multiplies the inverse matrix R _xx ⁻¹ (n) calculated by the inverse matrix calculator 172 and the cross-correlation vector r _xr (n) calculated by the cross-correlation vector calculator 176 to _obtain the desired A wave receiving weight coefficient w (n) is calculated. Therefore, the weight coefficient calculation unit 17 can obtain the desired wave reception weight coefficient w (n) by the following equation.

[Weight coefficient calculation unit for interference wave reception]
Next, the interference wave reception weight coefficient calculation unit 151 of the D / U measurement unit 15 shown in FIG. 1 will be described in detail. FIG. 6 is a block diagram illustrating a configuration of the interference wave receiving weight coefficient calculation unit 151. The interference wave receiving weight coefficient calculation unit 151 includes an orthogonal vector calculation unit 221 and a multiplication unit 222.

The interference wave reception weight coefficient calculation unit 151 suppresses the desired wave component by array synthesis using the desired wave reception weight coefficient w input from the weight coefficient calculation unit 17 and the inverse matrix R _xx ⁻¹ of the autocorrelation matrix. The interference wave receiving weight coefficient v is calculated.

  The orthogonal vector calculation unit 221 calculates an orthogonal vector using the desired wave reception weight coefficient input from the weight coefficient calculation unit 17. The orthogonal vector output from the orthogonal vector calculation unit 221 is input to the multiplication unit 222. The multiplier 222 multiplies the orthogonal vector input from the orthogonal vector calculator 221 by the inverse matrix of the autocorrelation matrix input from the weight coefficient calculator 17 to obtain an interference wave reception weight coefficient. The interference wave receiving weighting coefficient obtained by the multiplier 222 is input to the interference wave receiving array combining unit 152.

前記式（２５）を満たすｓは、例えば以下の式により求めることができる。

ここで、Ｌはアンテナ１０のアレー素子数を示し、ｗ_ｌは、干渉波受信用重み係数ｗの第ｌ番目の要素を示す。 If the weighting factor for receiving a desired wave is w, the arrival direction vector s of the interference wave satisfies the following expression. That is, they are in an orthogonal relationship.

For example, s satisfying the equation (25) can be obtained by the following equation.

Here, L is indicates the number of array elements of the antenna 10, w _l shows the l-th element of the interference wave receiving weighting factors w.

E and u are expressed by the following equations.

とすると、直交ベクトルｓは、以下の式により求めることができる。

For example, when L = 2,

Then, the orthogonal vector s can be obtained by the following equation.

Therefore, the interference wave receiving weighting coefficient in which the beam having the combined directional characteristic is directed toward the interference wave and the desired wave component is suppressed by the array combination can be obtained by the following equation.

[Synchronized playback section]
Next, the synchronized playback unit 18 shown in FIG. 1 will be described in detail. FIG. 7 is a block diagram showing the configuration of the synchronous playback unit 18. The synchronization reproduction unit 18 includes a symbol synchronization unit 181, a frame synchronization unit 182, a clock synchronization unit 183, a frequency synchronization unit 184, and a synchronization establishment state generation unit 185.

  The symbol synchronization unit 181 performs symbol synchronous reproduction processing using the equivalent baseband signals input from the orthogonal demodulation units 13 corresponding to the number of array elements, generates index synchronization information indicating symbol synchronization positions, and performs synchronization. When it is established, a status signal indicating that synchronization is established is generated. When synchronization is not established, a status signal indicating that synchronization is not established is generated. Synchronization information (symbol synchronization position index) output from the symbol synchronization unit 181 is input to the demodulation unit 16, and a state signal is input to the synchronization establishment state generation unit 185. Further, the symbol synchronization unit 181 resets the symbol synchronous reproduction processing based on the initialization control signal input from the control unit 19, and performs the same initialization processing as when the OFDM signal synthesizing receiver 1 is powered on. I do.

  The frame synchronization unit 182 uses the equivalent baseband signals input from the orthogonal demodulation units 13 corresponding to the number of array elements to perform frame synchronous reproduction processing, generates index synchronization information indicating the frame synchronization position, and When it is established, a status signal indicating that synchronization is established is generated. When synchronization is not established, a status signal indicating that synchronization is not established is generated. The synchronization information (frame synchronization position index) output from the frame synchronization unit 182 is input to the demodulation unit 16, and the state signal is input to the synchronization establishment state generation unit 185. Also, the frame synchronization unit 182 resets the synchronized playback process of the frame based on the initialization control signal input from the control unit 19, and performs the same initialization process as when the OFDM signal synthesizing receiver 1 is turned on. I do.

  The clock synchronizer 183 uses the equivalent baseband signal input from the orthogonal demodulator 13 for the number of array elements to perform synchronous clock recovery processing, generates clock control information for an oscillator (not shown), and establishes synchronization. When the synchronization is established, a status signal indicating that synchronization is established is generated. When the synchronization is not established, a status signal indicating that synchronization is not established is generated. The clock control information output from the clock synchronization unit 183 is input to an oscillator (not shown), and the state signal is input to the synchronization establishment state generation unit 185. Also, the clock synchronization unit 183 resets the clock synchronous reproduction processing based on the initialization control signal input from the control unit 19 and performs the same initialization processing as when the OFDM signal synthesizing receiver 1 is powered on. I do.

  The frequency synchronization unit 184 uses the equivalent baseband signals input from the orthogonal demodulation units 13 as many as the number of array elements, performs frequency synchronization reproduction processing, generates a frequency offset of the equivalent baseband signal, and establishes synchronization. When the synchronization is not established, a status signal indicating that synchronization is established is generated. When the synchronization is not established, a status signal indicating that synchronization is not established is generated. The frequency offset output from the frequency synchronization unit 184 is input to the demodulation unit 16 as synchronization information, and the state signal is input to the synchronization establishment state generation unit 185. Also, the frequency synchronization unit 184 resets the frequency synchronous reproduction process based on the initialization control signal input from the control unit 19 and performs the same initialization process as when the OFDM signal synthesizing receiver 1 is powered on. I do.

  The synchronization establishment state generation unit 185 generates a synchronization establishment state signal based on the state signals input from the symbol synchronization unit 181, the frame synchronization unit 182, the clock synchronization unit 183, and the frequency synchronization unit 184, respectively. Specifically, the synchronization establishment state generation unit 185 generates a synchronization establishment state signal indicating that the synchronization is established when all the input state signals indicate that synchronization is established. . Further, when at least one of the input status signals indicates that synchronization is not established, a synchronization establishment status signal indicating that the synchronization is not established is generated. The synchronization establishment state signal output from the synchronization establishment state generation unit 185 is input to the control unit 19.

  Next, details of the symbol synchronization unit 181 shown in FIG. 7 will be described. FIG. 8 is a block diagram showing the configuration of the symbol synchronization unit 181. As shown in FIG. The symbol synchronization unit 181 includes a delay unit 186, a complex conjugate unit 187, a multiplication unit 188, a moving average filter 189, an absolute value calculation unit 190, a maximum value detection unit 191 and an index generation unit 192.

  The delay unit 186 performs delay processing for the effective symbol length on the equivalent baseband signal input from the orthogonal demodulation unit 13 for the number of array elements. The delayed equivalent baseband signal output from the delay unit 186 is input to the complex conjugate unit 187. Further, the delay unit 186 resets and initializes the delay process based on the initialization control signal input from the control unit 19. The complex conjugate unit 187 obtains a complex conjugate value of the delayed equivalent baseband signal input from the delay unit 186. The complex conjugate value of the equivalent baseband signal delayed by the effective symbol length output from the complex conjugate unit 187 is input to the multiplication unit 188.

  Multiplier 188 multiplies the equivalent baseband signal input from orthogonal demodulator 13 for the number of array elements by the complex conjugate value of the equivalent baseband signal delayed from effective symbol length input from complex conjugate unit 187. . The multiplication result output from the multiplier 188 is input to the moving average filter 189. The moving average filter 189 performs a moving average filter process for the GI length on the multiplication result input from the multiplication unit 188, and calculates a moving average value. The moving average filter 189 resets and initializes the moving average filter processing based on the initialization control signal input from the control unit 19. The moving average value output by the moving average filter 189 is input to the absolute value calculation unit 190.

  The absolute value calculation unit 190 calculates the absolute value of the moving average value input from the moving average filter 189 and obtains the amplitude value. The amplitude value output from the absolute value calculation unit 190 is input to the maximum value detection unit 191. The maximum value detection unit 191 detects the maximum value of the amplitude value input by the absolute value calculation unit 190 with respect to the amplitude value for the number of points in a predetermined one symbol period on the time axis. A point number having an amplitude is generated as an index. Further, the maximum value detection unit 191 resets and initializes the maximum value detection process based on the initialization control signal input from the control unit 19. The index output from the maximum value detection unit 191 is input to the index generation unit 192.

  The index generation unit 192 uses the index having the maximum amplitude input from the maximum value detection unit 191 to determine whether synchronization has been established, generates a status signal, and generates index synchronization information ( Symbol). Further, the index generation unit 192 resets and initializes the index generation process based on the initialization control signal input from the control unit 19. The synchronization information (symbol) generated by the index generation unit 192 is input to the demodulation unit 16, and the state signal is input to the synchronization establishment state generation unit 185.

  FIG. 9 is a diagram illustrating the transition of the index generated by the maximum value detection unit 191 of the symbol synchronization unit 181 and input to the index generation unit 192. The horizontal axis shows time, and the vertical axis shows the point number index. The index generation unit 192 inputs a transition index as shown in FIG. In the synchronization establishment state of index i1, with respect to the transition from index i1 to index i2, i3, it is determined that index i2, i3 is an index that has instantaneously changed within a predetermined period and is ignored, and the synchronization information of index i1 Will continue to be output. Further, in response to the transition from index i1 to i4, it is determined that index i4 is not an index that has instantaneously transitioned, and a status signal indicating that synchronization has not been established is generated and output. As a result, the synchronization is not established. Then, when there is no change in the index i4 within a predetermined period, the index generation unit 192 generates and outputs synchronization information of the index i4, and generates and outputs a status signal indicating that synchronization is established. Thereby, it will be in the synchronization establishment state. As described above, the index generation unit 192 indicates that the synchronization is established based on the transition of the index input from the maximum value detection unit 191 within a predetermined period, or the synchronization is not established. Is generated, and an index when synchronization is established is output as synchronization information.

  Although only the details of the symbol synchronization unit 181 have been described here, the frame synchronization unit 182, the clock synchronization unit 183, and the frequency synchronization unit 184 also perform synchronization reproduction processing similar to that of the symbol synchronization unit 181 to obtain the synchronization information and status. A signal is generated, and the synchronous reproduction processing is reset and initialized based on the initialization control signal.

また、干渉波電力算出部１５４は、干渉波受信用アレー合成部１５２から入力される干渉波受信用にアレー合成された等価ベースバンド信号から、以下の式により干渉波電力Ｐ_Ｕを算出する。

ここで、Ｅ［・］は期待値演算を示す。 [Desired wave power calculation unit, interference wave power calculation unit, D / U calculation unit]
Next, the desired wave power calculation unit 153, the interference wave power calculation unit 154, and the D / U calculation unit 155 of the D / U measurement unit 15 illustrated in FIG. 1 will be described in detail. Desired wave power calculating portion 153 calculates a desired signal power P _D from the array synthesized equivalent baseband signal for a desired wave received input from the desired wave receiving array combining section 14, by the following equation.

Also, the interference wave power calculation unit 154, from the array synthesized equivalent baseband signal for the interference wave receiving input from the interference wave receiving array combining section 152 calculates the interference wave power P _U by the following equation.

Here, E [•] indicates an expected value calculation.

Therefore, D / U calculation section 155 calculates D / U Γ, which is the ratio of the desired wave power and the interference wave power of the received signal, using the following equation.

(Control part)
Next, the control unit 19 shown in FIG. 1 will be described in detail. FIG. 10 is a flowchart showing the processing of the control unit 19. In any of the following cases (a) to (c), the control unit 19 generates an initialization control signal, and resets and initializes the weight coefficient calculation unit 17 and the synchronous reproduction unit 18.
(A) When the state where synchronization is not established (non-established state) continues for a predetermined time in the synchronization establishment state signal generated by the synchronization reproduction unit 18 (b) In the synchronization establishment state, the D / U measurement unit 15 When the D / U measured by the above is negative for a predetermined period (the reception power of the interference wave is larger than the reception power of the desired wave) (c) calculated by the demodulator 16 in the synchronization establishment state When MER is less than a specified value for a specified period

  When the broadcast is stopped and only the interference wave is transmitted, the broadcast is started and the transmission of the desired wave is started, and the reception power of the desired wave becomes larger than the reception power of the interference wave. It becomes a state. The control unit 19 determines the state of (b) to generate an initialization control signal, and resets and initializes the weighting factor calculation unit 17 and the synchronous reproduction unit 18. As a result, the synchronization reproducing unit 18 generates new synchronization information according to the received desired wave and interference wave, and the weighting factor calculating unit 17 sets a preset initial value of the desired wave receiving weighting factor. The demodulating unit 16 calculates a new carrier symbol and frequency characteristic corresponding to the received desired wave and interference wave based on the synchronization information generated by the synchronization reproducing unit 18. Then, the weight coefficient calculation unit 17 calculates a new desired wave reception weight coefficient based on the received equivalent baseband signal of the desired wave and the interference wave, and the new carrier symbol and frequency characteristic, and the desired wave. The receiving array synthesizing unit 14 generates an array synthesized signal reflecting the received desired wave. Also, the interference wave reception weight coefficient calculation unit 151 calculates a new interference wave reception weight coefficient, and the interference wave reception array combination unit 152 generates an array combined signal in which the received interference wave is reflected. To do. That is, it is possible to suppress the interference wave in order to receive the desired wave without continuously suppressing the desired wave to be received.

  The control unit 19 receives the synchronization establishment state signal from the synchronization reproduction unit 18, and determines whether the synchronization establishment state signal indicates a synchronization non-establishment state or a synchronization establishment state (step S1001). When it is determined that the synchronization non-established state is indicated (step S1001: synchronization non-established), it is determined whether or not a predetermined time has passed while the non-established synchronization established state signal is continuously input (step S1002). ). If it is determined that the predetermined time has elapsed (step S1002: Y), an initialization control signal is generated and output to the weighting factor calculation unit 17 and the synchronous reproduction unit 18 (step S1005), and the process proceeds to step S1001. On the other hand, when it is determined that the predetermined time has not elapsed (step S1002: N), the process proceeds to step S1001.

  When it is determined in step S1001 that the synchronization establishment state signal indicates the synchronization establishment state (step S1001: synchronization establishment), the control unit 19 calculates D / U and 0 input from the D / U measurement unit 15 as follows. A comparison is made to determine whether D / U is negative for a predetermined period (step S1003). When it is determined that D / U is negative (step S1003: Y), that is, as described in (b) above, when the reception power of the interference wave is larger than the reception power of the desired wave in the synchronization established state, initialization control is performed. A signal is generated and output to the weighting factor calculation unit 17 and the synchronous reproduction unit 18 (step S1005), and the process proceeds to step S1001.

  When the control unit 19 determines in step S1003 that D / U is not negative (step S1003: N), the control unit 19 compares the MER input from the demodulating unit 16 with a predetermined value, and the MER is in a predetermined period. Whether or not it is less than the predetermined value (step S1004). If it is determined that the value is less than the predetermined value (step S1004: Y), an initialization control signal is generated, and the weighting factor calculation unit 17 and the synchronization It outputs to the reproduction | regeneration part 18 (step S1005), and transfers to step S1001. When it is determined that the value is not less than the predetermined value (step S1004: N), the process proceeds to step S1001.

  As described above, the control unit 19 determines (a) to (c), generates an initialization control signal, resets the weighting factor calculation unit 17 and the synchronous reproduction unit 18 and initializes them. In particular, the control unit 19 determines a state in which the D / U in the synchronization establishment state is negative based on the synchronization establishment state signal from the synchronization reproduction unit 18 and the D / U from the D / U measurement unit 15. From the state where the broadcast is paused and only the interference wave is transmitted, the broadcast starts and the transmission of the desired wave starts, and the reception power of the desired wave is detected to be greater than the reception power of the interference wave, An initialization control signal is generated to reset and initialize the weighting factor calculation unit 17 and the synchronous reproduction unit 18. Thus, the desired wave receiving weighting coefficient and the interference wave receiving weighting coefficient are calculated according to the incoming desired wave and interference wave, and an array composite signal is generated. That is, it is possible to suppress the interference wave in order to receive the desired wave without continuously suppressing the desired wave to be received.

  Next, the process (b) by the control unit 19 shown in FIG. 10 (process when the received power of the interference wave is larger than the received power of the desired wave in the synchronization established state, that is, step S1001: synchronization established, step The relationship between S1003: Y and the processing of step S1005) and the operation of the OFDM signal combining receiver 1 will be described in detail. 12 (1) is a diagram for explaining the normal operation, FIG. 12 (2) is a diagram for explaining the operation when the desired wave is stopped (when broadcasting is stopped), and FIG. 12 (3) is the desired wave. It is a figure explaining operation | movement (issue which this invention should solve) after transmission start (after broadcast start).

  In FIG. 12 (1), at the normal time when broadcasting is started, the desired wave and the interference wave are transmitted, and the received power of the desired wave is larger than the received power of the interference wave. The reception power of the signals synthesized by the desired wave receiving array synthesizing unit 14 of the OFDM signal synthesizing receiver 1 becomes the power reflecting the desired wave by suppressing the interference wave, and the interference wave receiving array synthesizing unit 152. The received power of the signals combined by the array is the power in which the desired wave is suppressed and the interference wave is reflected. Therefore, since the OFDM signal combining receiver 1 demodulates the signal of the desired wave, it is operating normally.

  In FIG. 12 (2), only the interference wave is transmitted when the desired wave is stopped when the broadcast is stopped. Since the OFDM signal combining receiver 1 is an apparatus that receives an OFDM signal, the received power of the signal combined by the desired signal receiving array combining unit 14 is a power that considers the interference wave as the desired wave (interference). The power of the wave becomes the power of the desired wave), and the received power of the signal combined by the interference wave receiving array combining unit 152 becomes a value close to zero.

  Also, in FIG. 12 (3), after the broadcast starts from the state of FIG. 12 (2) and the desired wave transmission starts, the desired wave and the interference wave are transmitted as in FIG. The received power is larger than the received power of the interference wave. As described above, when the symbol synchronization position or frame synchronization position of the desired wave and the interference wave match, the conventional OFDM signal combining receiver determines that synchronization has been established from before. Then, the interference wave is regarded as a desired wave and the signal is demodulated. In other words, the conventional OFDM signal synthesizing receiving apparatus continues the synchronization establishment state before the broadcast starts, suppresses the desired wave to be originally received, and continues to receive the interference wave. That is, in the OFDM signal combining receiver 1 shown in FIG. 1, when the weighting factor calculation unit 17 and the synchronous reproduction unit 18 are not initialized (in the conventional OFDM signal combining receiver), the desired wave receiving array is used. The received power of the signals combined by the combining unit 14 is the power in which the desired wave is suppressed and the interference wave is reflected, and the received power of the signals combined by the interference wave receiving array combining unit 152 is the interference wave. Is suppressed to a power reflecting the desired wave. That is, the conventional OFDM signal combining receiver demodulates the interference wave signal, and thus does not operate normally.

  When the OFDM signal combining receiver 1 according to the embodiment of the present invention shown in FIG. 1 changes from the state of FIG. 12 (2) to the state of FIG. 12 (3), this change is indicated by the steps shown in FIG. Detection is performed by the processing of S1001 and step S1003. That is, in a synchronization established state, a state in which the D / U measured by the D / U measuring unit 15 is negative for a predetermined period (a state in which the interference wave received power is larger than the desired wave received power) is detected. To do. Then, an initialization control signal is generated, and the weighting factor calculation unit 17 and the synchronous reproduction unit 18 are reset and initialized. As a result, the OFDM signal synthesizing receiver 1 can receive the interference wave to receive the desired wave without continuing to suppress the desired wave to be originally received, as in the normal operation shown in FIG. Can be suppressed.

〔Experimental result〕
Next, D / U experimental results obtained by computer simulation will be described. 11 shows the relationship between the D / U between the incoming waves and the D / U (estimated D / U) output from the D / U calculator 155 of the OFDM signal combining receiver 1 shown in FIG. The experimental results obtained by computer simulation are shown. This experimental result shows that when both the desired wave and the interference wave are signals by ISDB-T and the GI ratio is the same, only the interference wave of the two waves of the desired wave and the interference wave has arrived. It is assumed that the broadcast starts and the transmission of the desired wave begins. Further, it is assumed that the symbol synchronization positions of the desired wave and the interference wave are exactly the same, the array element interval of the antenna 10 is half the wavelength at the carrier frequency, the interference wave arrives from 0 degrees, and the desired wave Is assumed to come from 90 degrees. Further, the OFDM signal combining receiver 1 operates in a state where only an interference wave has arrived before the desired wave starts transmission. That is, since the OFDM signal combining receiver 1 receives an interference wave, the coordinate axis D / U shown in FIG. 11 is in an actual reciprocal number of D / U (positive and negative in dB are reversed). ing. From this state, when the broadcast starts and the transmission of the desired wave starts, the characteristics shown in FIG. 11 are obtained.

  As can be seen from FIG. 11, the D / U is correctly estimated by the D / U calculation unit 155 of the OFDM signal combining receiver 1. That is, when the transmission of the desired wave starts from the state where only the interference wave has arrived and the received power of the desired wave becomes larger than the received power of the interference wave, the OFDM signal combining receiver 1 generates the desired wave. It can be seen that suppression is detected, and that the weighting factor calculation unit 17 and the synchronous reproduction unit 18 are reset and initialized. That is, as shown in FIG. 12A, the desired signal to be received is not suppressed by the OFDM signal combining receiver 1, and the interference wave is suppressed as in the normal operation. I understand that.

  As described above, according to the OFDM signal combining receiver 1 according to the embodiment of the present invention shown in FIG. 1, the control unit 19 starts transmitting the desired wave from the state where only the interference wave is transmitted. A change to a state where the received power of the desired wave is larger than the received power of the interference wave is detected. Specifically, the control unit 19 determines the synchronization establishment state based on the synchronization establishment state signal from the synchronization reproduction unit 18, and in the synchronization establishment state, based on the D / U from the D / U measurement unit 15, It is determined whether the received power of the desired wave is greater than the received power of the interference wave (D / U is negative), and outputs an initialization control signal to the weighting factor calculation unit 17 and the synchronous reproduction unit 18 to calculate the weighting factor. The unit 17 and the synchronous playback unit 18 are reset and initialized. Here, when only the interference wave is transmitted, the synchronization is established. After that, when transmission of the desired wave starts and the received power of the desired wave becomes larger than the received power of the interference wave, the synchronization is established. Since D / U becomes negative in the established state, the control unit 19 can detect the above-described state change.

  As a result, the weighting factor calculation unit 17 and the synchronous reproduction unit 18 are initialized, the synchronous reproduction unit 18 generates new synchronization information, and the weighting factor calculation unit 17 outputs the initial value of the desired wave reception weighting factor. Then, the demodulator 16 calculates a new carrier symbol and frequency characteristic according to the received desired wave and interference wave based on the synchronization information generated by the synchronization reproducing unit 18. Then, the weight coefficient calculation unit 17 calculates a new desired wave reception weight coefficient based on the received equivalent baseband signal of the desired wave and the interference wave, and the new carrier symbol and frequency characteristic, and the desired wave. The receiving array combining unit 14 generates an array combined signal reflecting the received desired wave, and the interference wave receiving weighting factor calculating unit 151 calculates a new interference wave receiving weighting factor, and The wave receiving array combining unit 152 can generate an array combined signal in which the received interference wave is reflected. That is, it is possible to suppress the interference wave in order to receive the desired wave without continuously suppressing the desired wave to be received.

DESCRIPTION OF SYMBOLS 1 OFDM signal combining receiver 10 Antenna 11 Frequency converter 12 A / D converter 13 Orthogonal demodulator 14 Desired wave receiving array combiner 15 D / U measuring unit 16 Demodulator 17 Weight coefficient calculator 18 Synchronous playback unit 19 Control units 141, 157, 174, 177, 188, 222 Multiplication units 142, 158 Addition units 143, 159, 187 Complex conjugate unit 151 Interference wave reception weight coefficient calculation unit 152 Interference wave reception array synthesis unit 153 Calculation of desired wave power Unit 154 interference wave power calculation unit 155 D / U calculation unit 161 GI removal unit 162 FFT unit 163 channel estimation unit 164 channel equalization unit 165 demapping unit 166 parallel serial conversion unit 167 remapping unit 168 MER calculation unit 169 symbol reproduction unit 171 Autocorrelation matrix calculation unit 172 Inverse matrix calculation unit 173 Pilot insertion Input unit 175 OFDM remodulation unit 176 Cross correlation vector calculation unit 181 Symbol synchronization unit 182 Frame synchronization unit 183 Clock synchronization unit 184 Frequency synchronization unit 185 Synchronization establishment state generation unit 186 Delay unit 189 Moving average filter 190 Absolute value calculation unit 191 Maximum value detection Unit 192 Index generation unit 201 Pilot extraction unit 202 Pilot generation unit 203, 211 Division unit 204 Interpolation unit 221 Orthogonal vector calculation unit

Claims (6)

An OFDM signal combining receiver that receives an OFDM wave by an array antenna including a plurality of array elements and outputs a bit string,
An equivalent baseband signal of the received OFDM wave is synthesized by weighting in the time domain, and an array synthesis unit for receiving a desired wave to generate an array synthesis signal;
A demodulator that demodulates the array combined signal generated by the desired wave receiving array combiner and outputs a bit string;
Based on the carrier symbol obtained by channel equalization or symbol reproduction in the demodulator and the frequency characteristic obtained by channel estimation, a time domain reference signal is generated, and the array synthesized signal and the time domain reference signal are generated. A weighting factor calculation unit that calculates a weighting factor for receiving a desired wave for suppressing an interference wave, which is used for weighting in the array combining unit for receiving a desired wave, ,
A synchronization reproduction unit that reproduces synchronization based on the time domain equivalent baseband signal and generates a synchronization establishment state signal indicating whether synchronization is established;
A D / U measurement unit that measures a D / U (Desired to Undesired signal ratio) based on the equivalent baseband signal in the time domain;
Based on the synchronization establishment state signal generated by the synchronization reproduction unit, it is determined that synchronization is established, the D / U measured by the D / U measurement unit is determined to be negative, An OFDM signal combining receiver comprising: a weighting factor calculation unit; and a control unit that initializes the synchronous reproduction unit. In the OFDM signal combining receiver according to claim 1,
The D / U measuring unit is
An interference wave receiving weight coefficient calculating unit for calculating an interference wave receiving weight coefficient for suppressing the desired wave based on the desired wave receiving weight coefficient calculated by the weight coefficient calculating unit;
An interference wave receiving array combining unit that generates an array combined signal by combining the equivalent baseband signal by weighting in the time domain using the interference wave receiving weighting factor calculated by the interference wave receiving weighting factor calculating unit. When,
A desired wave power calculating unit that calculates the power of the array combined signal generated by the desired wave receiving array combining unit as desired wave power;
An interference wave power calculating unit that calculates the power of the array combined signal generated by the array combining unit for receiving an interference wave as interference wave power;
An OFDM comprising: a desired wave power calculated by the desired wave power calculating unit; and a D / U calculating unit that calculates a D / U from the interference wave power calculated by the interference wave power calculating unit. Signal synthesis receiver. In the OFDM signal combining receiver according to claim 1,
The weight coefficient calculation unit includes:
An autocorrelation matrix calculator that calculates an autocorrelation matrix in the time domain equivalent baseband signal;
An inverse matrix calculation unit for calculating an inverse matrix of the autocorrelation matrix calculated by the autocorrelation matrix calculation unit;
A cross-correlation vector calculating unit that calculates a cross-correlation vector from the time-domain equivalent baseband signal and the time-domain reference signal;
A multiplier for multiplying the inverse matrix of the autocorrelation matrix calculated by the inverse matrix calculator by the cross-correlation vector calculated by the cross-correlation vector calculator and obtaining a weighting factor for receiving a desired wave. An OFDM signal combining receiver characterized by the above. The OFDM signal combining receiver according to claim 2,
The interference wave receiving weight coefficient calculating unit of the D / U measuring unit is:
An orthogonal vector calculator that calculates an orthogonal vector that is orthogonal to the desired wave reception weight coefficient calculated by the weight coefficient calculator;
A multiplying unit that multiplies the orthogonal vector calculated by the orthogonal vector calculating unit by an inverse matrix of an autocorrelation matrix in the time domain equivalent baseband signal to obtain a weighting factor for interference wave reception. An OFDM signal synthesizing receiver. In the OFDM signal combining receiver according to claim 1,
The synchronized playback unit
A symbol synchronization unit that performs symbol synchronization reproduction based on the time domain equivalent baseband signal and generates a state signal indicating whether or not symbol synchronization is established;
A frame synchronization unit that performs frame synchronization reproduction based on the time domain equivalent baseband signal and generates a status signal indicating whether or not frame synchronization is established;
A clock synchronization unit that performs clock synchronization recovery based on the equivalent baseband signal in the time domain and generates a status signal indicating whether or not clock synchronization is established;
A frequency synchronization unit that performs frequency synchronization reproduction based on the time domain equivalent baseband signal and generates a state signal indicating whether or not frequency synchronization is established; and
If all the status signals generated by the symbol synchronization unit, the frame synchronization unit, the clock synchronization unit, and the frequency synchronization unit indicate that synchronization is established, synchronization establishment indicating that synchronization is established A synchronization establishment state that generates a state signal and generates a synchronization establishment state signal indicating that synchronization is not established if at least one of the state signals indicates that synchronization is not established; An OFDM signal combining receiver comprising: a generator. In the OFDM signal combining receiver according to claim 1,
The demodulation unit calculates MER (Modulation Error Ratio) based on the carrier symbol obtained by channel equalization and the carrier symbol obtained by symbol reproduction,
The controller is
Based on the synchronization establishment state signal generated by the synchronization reproduction unit, it is determined that synchronization is established, and the D / U measured by the D / U measurement unit is negative for a predetermined period. If you decide that
When determining that synchronization is not established based on the synchronization establishment state signal and determining that a predetermined time has elapsed in a state where the synchronization is not established, or
Based on the synchronization establishment state signal, it is determined that synchronization is established, and based on the MER calculated by the demodulator, it is determined that the MER is smaller than a predetermined value for a predetermined period. If
An OFDM signal synthesizing receiver characterized by initializing the weight coefficient calculation unit and the synchronous reproduction unit.

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