JP2010087745A - Information processing device and method, display, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration of reception performance in an OFDM reception device. <P>SOLUTION: A correlation detection circuit 111 calculates a complex conjugate correlation signal before and after delay of a complex base band signal in an effective symbol length delay circuit 110. A division circuit 120 divides one symbol section of the correlation signal into N. Each of average value calculation circuits 112-1 to 112-N obtains the respective average values of the divided correlation signals divided into N, a minimum value selection circuit 121 selects an average value whose absolute value becomes the minimum value as a corrected value among the respective average values. A correction circuit 113 corrects a correlation value signal from the correlation detection circuit 111 using the correlated value. A symbol timing reproduction circuit 115 detects the head timing of an effective symbol section from output of a guard interval length mobile average circuit 114, and outputs the detected head timing to an FFT operation circuit 107 as a symbol synchronizing signal. The present invention is applicable, for example, to editing of the OFDM reception device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an information processing device and method, a display device, and a program, and more particularly to an information processing device and method, a display device, and a program that can suppress degradation of reception performance in an OFDM receiving device.

  As a modulation system for terrestrial digital broadcasting, an orthogonal frequency division multiplexing system (OFDM system: Orthogonal Frequency Division Multiplexing system) has been proposed (for example, see Patent Document 1). The OFDM scheme is a scheme in which a large number of orthogonal carriers are used and each carrier is modulated by PSK (Phase Shift Keying) or QAM (Quadrature Amplitude Modulation).

  In the OFDM scheme, the entire transmission band is divided into a large number of subcarriers, so the band per subcarrier wave is narrowed and the transmission speed is slow. However, the OFDM system has a feature that is not different from the conventional modulation system in terms of the total transmission rate.

  In addition, the OFDM scheme has a feature that the symbol rate becomes slow because a large number of subcarriers are transmitted in parallel. Therefore, the time length of the multipath relative to the time length of one symbol can be shortened. As a result, the OFDM system has a feature that it is difficult to be affected by multipath.

  Further, in the OFDM scheme, data is allocated to a plurality of subcarriers. Therefore, a transmission circuit can be configured by using an IFFT (Inverse Fast Fourier Transform) arithmetic circuit that performs inverse Fourier transform at the time of modulation. Further, a receiving circuit can be configured by using an FFT (Fast Fourier Transform) arithmetic circuit that performs Fourier transform at the time of demodulation.

Because of these characteristics, the OFDM system is often applied to terrestrial digital broadcasting that is strongly affected by multipath interference. As digital terrestrial broadcasting adopting the OFDM system, for example, there is a standard such as DVB-T (Digital Video Broadcasting-Terrestrial). For example, there is a standard such as ISDB-T (Integrated Services Digital Broadcasting-Terrestrial).
Japanese Patent Laying-Open No. 2005-303440

  However, in the conventional OFDM receiver, the symbol timing synchronization performance and the frequency error correction performance may deteriorate, and the reception performance may deteriorate.

  The present invention has been made in view of such a situation, and is intended to suppress degradation of reception performance in an OFDM receiver.

  An information processing apparatus according to an aspect of the present invention is configured to perform orthogonal frequency division, in which an effective signal interval in which a data signal is transmitted and a guard interval interval in which a second half of the effective signal interval is copied as a redundant signal are configured as one symbol interval Receiving means for receiving an OFDM signal generated based on a multiplexing method (OFDM method: Orthogonal Frequency Division Multiplexing method); delay means for delaying the OFDM signal received by the receiving means by an effective signal interval length; Correlation value detection means for obtaining a complex correlation of the respective OFDM signals of the input and output of the delay means and outputting a correlation signal; N (1) symbols from the correlation signal output from the correlation value detection means ( N is an integer value of 2 or more), and N correction value candidates are generated on the basis of the N pieces of data collected by the collection unit. Generating means, selecting means for selecting a correction value based on a predetermined rule from the N correction value candidates generated by the generating means, and using the correction value selected by the selecting means, the correlation A correction means for correcting the correlation signal output from the value detection means, and the correlation signal corrected by the correction means, the start timing of the effective signal section of the OFDM signal received by the reception means. Symbol timing reproduction means for detecting and reproducing a symbol synchronization signal indicating the detection result, and the OFDM signal received by the reception means with reference to the symbol synchronization signal reproduced by the symbol timing reproduction means And FFT calculation means for performing FFT (Fast Fourier Transform) calculation processing.

  The sampling unit divides one symbol section of the correlation signal into N, samples each of the N-divided correlation signals as a divided correlation signal, and the generation unit calculates an average value of each of the N divided correlation signals, N correction candidates are generated.

  The selecting means selects a minimum absolute value of the N correction value candidates as the correction value.

  A frequency error is detected by using the correlation signal corrected by the correction means, and the detection result is output to the reception means by using the detection result by the frequency error detection means as feedback information. Frequency error correction means for correcting the frequency error of the newly received OFDM signal is further provided.

  Using the correlation signal corrected by the correcting means, a phase fluctuation estimating means for estimating a phase fluctuation amount in one symbol, and the FFT calculation based on the phase fluctuation amount estimated by the phase fluctuation estimating means And a phase fluctuation correcting unit that corrects the OFDM signal after the FFT calculation process is performed by the unit.

  Using the correlation signal corrected by the correcting means, a phase fluctuation estimating means for estimating a phase fluctuation amount in one symbol, and the FFT calculation based on the phase fluctuation amount estimated by the phase fluctuation estimating means And a phase fluctuation correcting means for correcting the OFDM signal before the FFT arithmetic processing is performed by the means.

  An information processing method and program according to one aspect of the present invention are a method and program corresponding to the information processing apparatus according to one aspect of the present invention described above. The display device according to one aspect of the present invention is a display unit that displays an image corresponding to the OFDM signal that has been subjected to the FFT operation processing by the FFT operation unit with respect to the information processing device according to one aspect of the present invention described above. Is further provided.

  In the information processing apparatus and method, the display device, and the program according to one aspect of the present invention, the effective signal section in which the data signal is transmitted and the guard interval section in which the second half of the effective signal section is copied as a redundant signal are 1 An OFDM signal generated based on an Orthogonal Frequency Division Multiplexing (OFDM method) configured as a symbol interval is received, and the received OFDM signal is delayed by an effective signal interval length before and after the delay. A complex signal of each of the OFDM signals is obtained and a correlation signal is output, and N (N is an integer value of 2 or more) data is collected from one symbol section of the output correlation signal and collected. N correction value candidates are generated based on the N pieces of data, and correction values are selected based on a predetermined rule from the generated N correction value candidates. Using the selected correction value, the output correlation signal is corrected, and using the corrected correlation signal, the start timing of the effective signal section of the received OFDM signal is detected, and the detection is performed. A symbol synchronization signal indicating the result is reproduced, and an FFT (Fast Fourier Transform) calculation process is performed on the received OFDM signal with reference to the reproduced symbol synchronization signal. Furthermore, in the display device according to one aspect of the present invention, an image corresponding to the OFDM signal subjected to the FFT calculation process is displayed.

  As described above, according to the present invention, it is possible to suppress degradation of reception performance in an OFDM receiver.

Hereinafter, embodiments of an information processing apparatus to which the present invention is applied will be described. In order to facilitate understanding of the present invention, a conventional description will be given first. Next, three embodiments of the information processing apparatus to which the present invention is applied (hereinafter referred to as first to third embodiments, respectively) will be described. Therefore, description will be given in the following order.
1. Conventional Description First embodiment (when the present invention is applied to an OFDM receiver)
3. Second embodiment (when the present invention is applied to an OFDM receiver)
4). Third embodiment (when the present invention is applied to an OFDM receiver)

<1. Conventional Description>
First, in order to facilitate the understanding of the present invention, the causes of the contents described in the section “Problems to be solved by the invention” will be described with reference to FIGS.

  FIG. 1 shows a configuration example of a transmission signal by the OFDM method.

  As shown in FIG. 1, a transmission signal according to the OFDM scheme is transmitted in units of symbols called OFDM symbols. The OFDM symbol includes an effective symbol that is a signal period during which IFFT is performed at the time of transmission, and a guard interval in which a partial waveform of the latter half of the effective symbol is copied as it is. Hereinafter, Tu [sec] is adopted as a symbol representing the effective symbol length of OFDM. Also, Fc [Hz] is adopted as a symbol representing the OFDM subcarrier interval. When the symbols are determined in this way, the relational expression Fc = 1 / Tu is established.

  The aforementioned guard interval is provided in the first half of the OFDM symbol. In the OFDM scheme, such a guard interval is provided to improve multipath tolerance.

  FIG. 2 shows a configuration example of a conventional OFDM receiving apparatus 100.

  The conventional OFDM receiver 100 is configured to include an antenna 101 to a frequency error detection circuit 116 and a display unit 210.

  Hereinafter, an operation example of the conventional OFDM receiving apparatus 100 will be described.

  Broadcast waves from the broadcast station are received by the antenna 101 of the conventional OFDM receiver 100 and supplied to the tuner 102 as RF signals.

  The tuner 102 includes a multiplication circuit 102a and a local oscillator 102b. The tuner 102 converts the RF signal received from the antenna 101 into an IF signal.

  The IF signal obtained by the tuner 102 is filtered by a band pass filter (BPF) 103, digitized by an A / D conversion circuit 104, and supplied to an orthogonal demodulation circuit 105.

  The orthogonal demodulation circuit 105 performs orthogonal demodulation on the digitized IF signal using a carrier signal having a predetermined frequency (carrier frequency), and outputs a baseband OFDM signal.

  The baseband OFDM signal output from the quadrature demodulation circuit 105 is a so-called OFDM time domain signal before being subjected to the FFT operation. As a result of orthogonal demodulation, the OFDM time domain signal becomes a complex signal including a real axis component (I channel signal) and an imaginary axis (Q channel signal).

  The sampling / carrier frequency error correction circuit 106 (hereinafter abbreviated as the circuit 106) performs sampling / carrier offset correction or the like on the OFDM time domain signal as the name implies. Specifically, for example, the circuit 106 corrects the sampling offset in the A / D conversion circuit 104 and the carrier frequency offset in the tuner 102. As other processing of the circuit 106, for example, filtering processing or the like may be performed in order to remove the same channel interference and the adjacent channel interference.

  The OFDM time domain signal is supplied to the FFT operation circuit 107 after being subjected to the above processing.

  The FFT operation circuit 107 extracts a signal section for performing FFT in accordance with the symbol synchronization signal supplied from the symbol timing recovery circuit 115 from the OFDM time domain signal that has been subjected to various processes, and performs an FFT operation in the signal section. Do. As a result, data transmitted for each subcarrier is extracted and output from the FFT operation circuit 107. The signal output from the FFT operation circuit 107 is a so-called frequency domain signal after the FFT operation. Therefore, hereinafter, the signal after the FFT calculation is referred to as an OFDM frequency domain signal.

  The transmission path distortion correction circuit 108 corrects the amplitude and phase distortion received by the OFDM frequency domain signal on the transmission path based on the estimated transmission path characteristics, and supplies the corrected signal to the error correction circuit 109 as an equalized signal.

  The error correction circuit 109 performs deinterleaving processing on the signal interleaved on the transmission side. The decoded data is output from the error correction circuit 109 through denpuncture, Viterbi decoding, spread signal removal, and RS decoding.

  The display unit 210 displays a video corresponding to the decoded data output from the error correction circuit 109.

  FIG. 3 shows an example of a timing chart of each output signal from the circuit 106 to the guard interval length moving average circuit 114. That is, each of A to F in FIG. 3 is an example of a timing chart of each output signal of the circuit 106 to the guard interval length moving average circuit 114.

  Therefore, an example of a series of operations of the effective symbol length delay circuit 110 to the frequency error detection circuit 116 of FIG. 2 will be described below with reference to the timing chart of FIG. 3 as appropriate.

  The effective symbol length delay circuit 110 delays the output signal of the circuit 106 by an effective symbol long period. That is, for example, a signal delayed as shown in B of FIG. 3 with respect to the signal of A in FIG. 3 is output from the effective symbol length delay circuit 110.

  The correlation detection circuit 111 obtains a complex conjugate correlation between the complex baseband signals output from the circuit 106 and the effective symbol length delay circuit 110, respectively. That is, for example, as a result of obtaining the complex conjugate correlation between the signal A in FIG. 3 and the signal B in FIG. 3, a signal such as C in FIG. 3 is obtained. Among the correlation values shown as the signal level of C in FIG. 3, the portion that is a large value (the high level value of the pulse) is the portion where the input complex baseband signals match.

  The average value calculation circuit 112 calculates the average of the correlation values output from the correlation detection circuit 111. The correlation value output from the correlation detection circuit 111 is a correlation signal output when there is a highly correlated interference wave such as CW (Continuous Wave), and the correlation signal when there is no interference wave and the correlation signal due to the interference wave. Is a synthesized signal. Therefore, the average value calculation circuit 112 calculates a correlation signal added by the interference wave. The resulting signal is, for example, the signal D in FIG.

  The correction circuit 113 corrects the correlation value output from the correlation detection circuit 111 using the output signal of the average value calculation circuit 112. For example, the signal C in FIG. 3 is corrected using the signal D in FIG. 3, and as a result, the signal E in FIG. 3 is obtained.

  The guard interval length moving average circuit 114 performs a guard interval length moving average process on the corrected correlation value output output from the correction circuit 113. Then, a correlation signal whose absolute value peaks at the end of the effective symbol period is obtained. Here, when there is no frequency error in the received signal, this peak appears only in the I component and the Q component becomes almost zero. For example, for the I component, the signal F in FIG. 3 is obtained.

  The symbol timing recovery circuit 115 detects the leading timing of the effective symbol interval from the output of the guard interval length moving average circuit 114 and supplies it to the FFT operation circuit 107 as a symbol synchronization signal.

  The frequency error detection circuit 116 obtains the phase angle from the I component and the Q component of the element where the absolute value of the correlation signal output from the guard interval length moving average circuit 114 peaks. As described above, when there is no frequency error in the received signal, this peak appears only in the I component and the Q component becomes almost zero. As a result, the magnitude of this phase angle is proportional to the frequency error. Therefore, the frequency error detection circuit 116 detects the frequency error from the magnitude of the phase angle and supplies it to the circuit 106 as a carrier frequency error signal.

  As described above, in the conventional OFDM receiver 100, the average value calculation circuit 112 estimates the influence of the interference wave on the output of the correlation detection circuit 111.

  4 and 5 are block diagrams showing a configuration example of the conventional average value calculation circuit 112. The average value calculation circuit 112 in FIG. 4 has a configuration in which an average of all inputs after the start of operation is obtained using an IIR type leak integration filter. The average value calculation circuit 112 of FIG. 5 has a configuration for obtaining an average of inputs for one symbol using an IIR type leak integration filter.

  FIG. 6 is an example of a timing chart of each output signal of the circuit 106 to the guard interval length moving average circuit 114, and shows an example different from the example of FIG. That is, each of A to F in FIG. 6 is an example of a timing chart of each output signal of the circuit 106 to the guard interval length moving average circuit 114, and is an example different from the example of FIG.

  As shown in FIG. 6C, the output of the correlation detection circuit 111 includes correlation signals of a portion where the correlation exists and a portion where the correlation does not exist. If the average is calculated by the average value calculation circuit 112 having the configuration shown in FIG. 4 or 5 in a state where the correlation signals of the two are combined, the influence of the interference wave cannot be estimated correctly. As a result, the correction circuit 113 may perform an incorrect correction as shown by the signal E in FIG. As a result, as shown as a signal F in FIG. 6, the absolute value peak of the output of the guard interval length moving average circuit 114 deviates from the end of the effective symbol. Moreover, the phase angle does not show an actual frequency error from the I component and the Q component of the peak element. Such a situation will occur.

  In this case, as shown in a section T1 in FIG. 6, if a section having no correlation, that is, a section other than the latter half of the guard interval section and the effective symbol section can be input to the average value calculation circuit 112, the above-described situation Can be prevented.

  However, it is difficult to detect the section T1 before the symbol timing reproduction. Further, when a delay wave as shown in FIG. 6 exists, or when the magnitude and delay time of the delay wave fluctuate, a section T1 in which there is no correlation signal when there is no interference wave is shown in FIG. It will fluctuate with respect to the section. In such a case, detection of the section T1 becomes even more difficult.

  That is, under the present circumstances, the above-described situation occurs, and as a result, the content described in the section “Problems to be solved by the invention” occurs. That is, symbol timing synchronization performance and frequency error correction performance are degraded, and reception performance is degraded.

  In the following, when there is an interference wave, even in the environment where a delay wave exists, the influence of the interference wave can be removed with a simple mechanism, and the symbol synchronization and the carrier frequency error correction performance are improved. The present invention capable of improving the reception performance will be described.

  That is, hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Needless to say, the present invention is not limited to the following embodiments, and can be arbitrarily changed without departing from the gist of the present invention.

<2. First Embodiment>
[Configuration example of the information processing apparatus according to the first embodiment]

  FIG. 7 shows a configuration example of an OFDM receiving apparatus as the first embodiment of the information processing apparatus to which the present invention is applied.

  In FIG. 7, portions corresponding to those in FIG. Therefore, these descriptions are omitted as appropriate.

  The OFDM receiver 300 according to the first embodiment is provided with an antenna 101 through an error correction circuit 109 and a display unit 210 as in the conventional OFDM receiver 100 of FIG.

  Further, the OFDM receiver 300 includes an effective symbol length delay circuit 110, a correlation detection circuit 111, a correction circuit 113, a guard interval length moving average circuit 114, a symbol timing recovery circuit, as in the conventional OFDM receiver 100 of FIG. 115 and a frequency error detection circuit 116 are provided.

  Thus, the configuration within the above-described range of the configuration of the OFDM receiving device 300 is the same as the configuration of the conventional OFDM receiving device 100 of FIG. That is, in the configuration of the OFDM receiving apparatus 300, the configuration in the range described below is different from the configuration of the conventional OFDM receiving apparatus 100 in FIG.

  That is, the conventional OFDM receiver 100 of FIG. 2 is provided with one average value calculation circuit 112 in addition to the above-described configuration. On the other hand, in addition to the configuration described above, the OFDM receiver 300 includes a dividing circuit 120, N (N is an integer value of 2 or more) average value calculation circuits 112-1 to 112-N, and a minimum value. A selection circuit 121 is provided.

  Each individual circuit itself of each of the average value calculation circuits 112-1 to 112-N has basically the same function and configuration as the conventional average value calculation circuit 112. That is, as the individual circuit configuration of the average value calculation circuits 112-1 to 112-N, for example, the configuration of FIG. 4 described above can be employed, and the configuration of FIG. 5 described above can also be employed.

[Operation Example of Information Processing Apparatus of First Embodiment]

  Hereinafter, an operation example of the OFDM receiver 300 in FIG. 7 will be described.

  A series of operations for the antenna 101 to the error correction circuit 109 and the display unit 210 is the same as the series of operations described as the operation of the conventional OFDM receiver 100. Therefore, the description is omitted here.

  Therefore, referring to FIG. 8 as appropriate, a series of the effective symbol length delay circuit 110 to the frequency error detection circuit 116, the dividing circuit 120, the average value calculation circuits 112-1 to 112-N, and the minimum value selection circuit 121 will be described below. Will be described.

  FIG. 8 shows an example of a timing chart of each output signal from the circuit 106 to the guard interval length moving average circuit 114.

  8A shows an example of an output signal of the circuit 106, FIG. 8B shows an example of an output signal of the effective symbol length delay circuit 110, and FIG. 8C shows an example of a timing chart of the output signal of the correlation detection circuit 111. ing.

  As can be easily understood by comparing the output signals A to C in FIG. 8 with the output signals A to C in FIG. 6 showing the conventional operation example, the circuit 106, the effective symbol length delay circuit 110, and the correlation detection A series of operations up to the circuit 111 is basically the same as the conventional operation. Therefore, the description is omitted here.

  The dividing circuit 120 performs a dividing process of dividing a signal of a section corresponding to 1 OFDM symbol (hereinafter referred to as 1 symbol section) out of the correlation signal output from the correlation detection circuit 111 into N parts. Each N-divided correlation signal (hereinafter referred to as a divided correlation signal) is input to average value calculation circuits 112-1 to 112-N, respectively. Each of the average value calculation circuits 112-1 to 112-N obtains an average value of the divided correlation signals input to itself.

  An example of a signal obtained by combining the output signals of the average value calculation circuits 112-1 to 112-N is a signal D in FIG. That is, the portion of the signal D in FIG. 8 that is divided by two dotted lines in the vertical direction in the figure shows the average value of one divided correlation signal.

  Even assuming the presence of a delayed wave having a long delay, the correlation occurs only in the interval in which the main wave and delayed wave guard interval interval and the latter half of the effective symbol interval are correlated, There is a section where no correlation occurs in one symbol section. That is, by setting an appropriate N, among the divided correlation signals divided into N from the one-symbol interval correlation signal, there exists at least one divided correlation signal in the interval where no correlation occurs. The absolute value of the average value of the divided correlation signal in the section where no correlation occurs should be smaller than the absolute value of the average value of the divided correlation signal including the section where the correlation occurs.

  Therefore, as shown in E of FIG. 8, the minimum value selection circuit 121 has the absolute value of the minimum value among the average values of the divided correlation signals divided into N from the correlation signal in one symbol period. The average value is selected as a correction value and supplied to the correction circuit 113.

  The subsequent series of operations of the correction circuit 113, the guard interval length moving average circuit 114, the symbol timing recovery circuit 115, and the frequency error detection circuit 116 are basically the same as those in the prior art. However, as described above, the absolute value of the average value of the divided correlation signals in the section where no correlation occurs is input to the correction circuit 113 as a correction value. Therefore, as shown in F and G of FIG. 8, the correction circuit 113 performs appropriate correction, and as a result, the absolute value peak of the output of the guard interval length moving average circuit 114 comes to the end of the effective symbol. Become. In addition, the phase angle indicates the actual frequency error from the I component and Q component of the peak element.

  FIG. 9 is a flowchart showing an example of the operation of the OFDM receiving apparatus 300 as OFDM demodulation processing.

  In step S <b> 1, the tuner 102 performs frequency conversion of the RF signal received by the reception antenna 101 into an IF signal, and outputs the IF signal to the A / D conversion circuit 104 via the BPF 103.

  In step S <b> 2, the A / D conversion circuit 104 performs A / D conversion on the IF signal and outputs the digital IF signal to the quadrature demodulation circuit 105.

  In step S3, the quadrature demodulation circuit 105 performs quadrature demodulation of the digitized IF signal, and an OFDM time domain signal obtained as a result is passed through the circuit 106 to the FFT operation circuit 107, the effective symbol length delay circuit 110, and To the correlation detection circuit 111.

  In step S4, the FFT operation circuit 107 extracts a signal section for performing FFT in accordance with the symbol synchronization signal from the OFDM time domain signal, and performs FFT operation processing in the signal section. Note that the symbol synchronization signal is output to the FFT operation circuit 107 as a result of executing processing according to the flowchart of FIG.

  An OFDM frequency domain signal obtained by performing the FFT operation processing is output to the transmission path distortion correction circuit 108. In step S5, the transmission path distortion correction circuit 108 corrects the transmission path distortion with respect to the OFDM frequency domain signal, and supplies it to the error correction circuit 109 as an equalized signal.

  In step S6, the error correction circuit 109 performs a deinterleaving process on the signal interleaved on the transmission side. As a result, decoded data is output from the error correction circuit 109, and a video corresponding to the decoded data is displayed on the display unit 210.

  FIG. 10 is a flowchart for explaining an example of processing (hereinafter referred to as symbol synchronization signal output processing) until the symbol synchronization signal used in the FFT operation processing in step S4 of FIG. 8 is output.

  In step S21, the effective symbol length delay circuit 110 delays the complex baseband signal (OFDM time domain signal) from the circuit 106 by an effective symbol long period.

  In step S22, the correlation detection circuit 111 obtains a complex conjugate correlation signal before and after the delay of the complex baseband signal.

  In step S23, the dividing circuit 120 divides one symbol section of the correlation signal into N, and outputs the N divided divided correlation signals obtained as a result to each of the average value calculating circuits 112-1 to 112-N.

  In step S24, each of the average value calculation circuits 112-1 to 112-N obtains an average value of the divided correlation signals divided into N.

  In step S <b> 25, the minimum value selection circuit 121 selects, as a correction value, the average value having the minimum absolute value from the average values of the N-divided divided correlation signals, and supplies the correction value to the correction circuit 113. .

  In step S <b> 26, the correction circuit 113 corrects the correlation value signal from the correlation detection circuit 111 using the correction value from the minimum value selection circuit 121.

  In step S27, the guard interval length moving average circuit 114 performs a moving average process of the guard interval length on the corrected correlation signal, and outputs a signal obtained as a result.

  In step S28, the symbol timing recovery circuit 115 detects the head timing of the effective symbol period from the output of the guard interval length moving average circuit 114, and outputs it to the FFT operation circuit 107 as a symbol synchronization signal.

<3. Second Embodiment>
[Configuration Example of Information Processing Apparatus of Second Embodiment]

  FIG. 11 shows a configuration example of an OFDM receiving apparatus as a second embodiment of the information processing apparatus to which the present invention is applied.

  In FIG. 11, parts corresponding to those in FIG. Therefore, these descriptions are omitted as appropriate.

  The OFDM receiver 400 according to the second embodiment can perform phase noise removal using the correlation signal in the guard interval section.

  For this reason, the OFDM receiver 400 of the second embodiment further includes a phase fluctuation between the FFT operation circuit 107 and the transmission path distortion correction circuit 108 in addition to the configuration of the OFDM receiver 300 of the first embodiment. A correction circuit 131 is provided. Further, in order to supply a phase fluctuation signal to the phase fluctuation correction circuit 131, the OFDM receiver 400 of the second embodiment is provided with a phase fluctuation estimation circuit 130. However, in the OFDM receiver 400 of the second embodiment, the frequency error detection circuit 116 in FIG. 7 is omitted. Other configurations of the OFDM receiving apparatus 400 of the second embodiment are basically the same as those of the OFDM receiving apparatus 400 of the first embodiment.

[Operation Example of Information Processing Apparatus of Second Embodiment]

  Hereinafter, an operation example of the OFDM receiver 400 in FIG. 11 will be described.

  A series of operations from the antenna 101 to the FFT operation circuit 107 is the same as the series of operations described as the operation of the OFDM receiver 300 according to the first embodiment. A series of operations of the effective symbol length delay circuit 110 to the symbol timing recovery circuit 115, the dividing circuit 120, the average value calculation circuits 112-1 to 112-N, and the minimum value selection circuit 121 are also described in the first embodiment. This is the same as the series of operations described as the operation of the OFDM receiving apparatus 300. Therefore, these descriptions are omitted.

  The phase angle of the I component and the Q component of the element that is the peak of the correlation signal output from the guard interval length moving average circuit 114 indicates the amount of phase fluctuation between the guard interval interval and the latter half of the effective symbol interval. . Therefore, the phase fluctuation estimation circuit 130 estimates the amount of phase fluctuation within one symbol period using this, and supplies the estimation result to the phase fluctuation correction circuit 131 as a phase fluctuation signal.

  The phase fluctuation correction circuit 131 corrects the OFDM frequency domain signal from the FFT operation circuit 107 using the phase fluctuation signal supplied from the phase fluctuation estimation circuit 131. Thereby, the phase noise fluctuation of the OFDM signal received by the OFDM receiver 400 can be removed.

  The subsequent series of operations, that is, the series of operations up to the transmission path distortion correction circuit 108, the error correction circuit 109, and the display unit 210 are also the series of operations described as the operation of the OFDM receiver 300 of the first embodiment. It is the same. Therefore, this description is omitted.

<4. Third Embodiment>
[Configuration Example of Information Processing Device of Third Embodiment]

  FIG. 12 shows a configuration example of an OFDM receiver as a third embodiment of the information processing apparatus to which the present invention is applied.

  In FIG. 12, the parts corresponding to those in FIG. Therefore, these descriptions are omitted as appropriate.

  The OFDM receiver 500 according to the third embodiment can perform phase noise removal before the FFT calculation using the correlation signal in the guard interval section.

  For this reason, the OFDM receiver 500 according to the third embodiment is provided with a circuit and the like similar to those of the OFDM receiver 400 according to the second embodiment. That is, the components themselves are the same as those of the OFDM receiving apparatus 500 of the third embodiment and the OFDM receiving apparatus 400 of the second embodiment. However, the arrangement position of the phase fluctuation correction circuit 131 is different. That is, in the OFDM receiver 400 of the second embodiment, the phase fluctuation correction circuit 131 is provided between the FFT operation circuit 107 and the transmission path distortion correction circuit 108. On the other hand, in the OFDM receiver 500 according to the third embodiment, a phase fluctuation correction circuit 131 is provided between the circuit 106 and the FFT operation circuit 107.

[Operation Example of Information Processing Device of Third Embodiment]

  Hereinafter, an operation example of the OFDM receiving apparatus 500 of FIG. 12 will be described.

  A series of operations from the antenna 101 to the circuit 106 is the same as the series of operations described as the operation of the OFDM receiver 400 according to the second embodiment. A series of operations of the effective symbol length delay circuit 110 to the symbol timing recovery circuit 115, the dividing circuit 120, the average value calculation circuits 112-1 to 112-N, and the minimum value selection circuit 121 are also described in the second embodiment. This is the same as the series of operations described as the operation of the OFDM receiver 400. Therefore, these descriptions are omitted.

  The phase angle of the I component and the Q component of the element that is the peak of the correlation signal output from the guard interval length moving average circuit 114 indicates the amount of phase fluctuation between the guard interval interval and the latter half of the effective symbol interval. . Therefore, the phase fluctuation estimation circuit 130 estimates the amount of phase fluctuation within one symbol period using this, and supplies the estimation result to the phase fluctuation correction circuit 131 as a phase fluctuation signal.

  The phase fluctuation correction circuit 131 corrects the OFDM time domain signal from the circuit 106 using the phase fluctuation signal supplied from the phase fluctuation estimation circuit 130. Thereby, the phase noise fluctuation of the OFDM signal received by the OFDM receiver 400 can be removed before the FFT calculation process.

  The subsequent series of operations, that is, the series of operations up to the FFT operation circuit 107, the transmission path distortion correction circuit 108, the error correction circuit 109, and the display unit 210 are also the operations of the OFDM receiver 500 of the second embodiment. This is the same as the series of operations described. Therefore, this description is omitted.

  As above, the first to third embodiments have been described as embodiments of the information processing apparatus to which the present invention is applied. However, it goes without saying that the present invention can take various embodiments in addition to the first to third embodiments. For example, instead of the minimum value selection circuit 121 employed in the first to third embodiments described above, the following circuit may be employed. That is, for example, it is possible to adopt a circuit that takes a majority decision on the absolute value of each average value of the divided correlation signal divided into N from the correlation signal in one symbol section and selects a correction value based on the result. Further, for example, it is possible to adopt a circuit that takes a majority decision for each of the I component and Q component of each average value of the divided correlation signal divided into N from the correlation signal of one symbol section, and selects a correction value based on the result. Further, for example, a circuit that selects a predetermined value such as a median value among the absolute values of the average values of the divided correlation signals divided into N from the correlation signal of one symbol section as a correction value can be employed. In addition, for example, a circuit that selects a predetermined value such as a median value of the I component and the Q component of each average value of the divided correlation signals divided into N from the correlation signal in one symbol section as a correction value can be employed.

  By the way, the series of processes described above can be executed by hardware, but can also be executed by software.

  In this case, for example, a personal computer shown in FIG. 13 may be employed as at least a part of the information processing apparatus to which the present invention is applied.

  In FIG. 13, a CPU (Central Processing Unit) 601 executes various processes according to a program recorded in a ROM (Read Only Memory) 602 or a program loaded from a storage unit 608 to a RAM (Random Access Memory) 603. To do. The RAM 603 also appropriately stores data necessary for the CPU 601 to execute various processes.

  The CPU 601, ROM 602, and RAM 603 are connected to each other via a bus 604. An input / output interface 605 is also connected to the bus 604.

  The input / output interface 605 includes an input unit 606 composed of a keyboard and a mouse, an output unit 607 composed of a display, a storage unit 608 composed of a hard disk, and a communication unit 609 composed of a modem, a terminal adapter, and the like. It is connected. The communication unit 609 controls communication performed with other devices (not shown) via a network including the Internet.

  A drive 610 is also connected to the input / output interface 605 as necessary, and a removable medium 611 composed of a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, or the like is appropriately installed, and a computer program read from them is loaded. The storage unit 608 is installed as necessary.

  When a series of processing is executed by software, a program constituting the software executes various functions by installing a computer incorporated in dedicated hardware or various programs. For example, a general-purpose personal computer is installed from a network or a recording medium.

  As shown in FIG. 13, the recording medium including such a program is distributed to provide a program to the user separately from the main body of the apparatus, and includes a magnetic disk (including a floppy disk) on which the program is recorded. , Removable media (package media) consisting of optical disks (including compact disk-read only memory (CD-ROM), DVD (digital versatile disk)), magneto-optical disks (including MD (mini-disk)), or semiconductor memory ), And a ROM 602 on which a program is recorded and a hard disk included in the storage unit 608 provided to the user in a state of being incorporated in the apparatus main body in advance.

  In the present specification, the step of describing the program recorded on the recording medium is not limited to the processing performed in chronological order according to the order, but is not necessarily performed in chronological order, either in parallel or individually. The process to be executed is also included.

  Further, the present invention can be applied to a display device as it can be applied to the OFDM receiver 300 including the display unit 210 of FIG. Such a display device can be applied to a display that displays video signals input to various electronic devices or generated in various electronic devices as images or videos. Here, as various electronic devices, for example, there are a digital still camera, a digital video camera, a notebook personal computer, a mobile phone, a television receiver, and the like. Examples of electronic devices to which such a display device is applied are shown below.

  For example, the present invention can be applied to a television receiver which is an example of an electronic device. This television receiver includes a video display screen including a front panel, a filter glass, and the like, and is manufactured by using the display device of the present invention for the video display screen.

  For example, the present invention can be applied to a notebook personal computer which is an example of an electronic device. In this notebook personal computer, the main body includes a keyboard that is operated when characters and the like are input, and the main body cover includes a display unit that displays an image. This notebook personal computer is manufactured by using the display device of the present invention for the display portion.

  For example, the present invention can be applied to a mobile terminal device that is an example of an electronic device. This portable terminal device has an upper housing and a lower housing. As states of the portable terminal device, there are a state in which the two casings are opened and a state in which the two casings are closed. This portable terminal device includes a connecting portion (here, a hinge portion), a display, a sub-display, a picture light, a camera, and the like in addition to the above-described upper housing and lower housing. It is manufactured by using it for sub-displays.

  For example, the present invention is applicable to a digital video camera that is an example of an electronic device. The digital video camera includes a main body, a lens for photographing a subject on a side facing forward, a start / stop switch at the time of photographing, a monitor, and the like, and is manufactured by using the display device of the present invention for the monitor.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

It is a figure explaining the transmission symbol of an OFDM signal. It is a block diagram which shows the structural example of the conventional OFDM receiver. It is a timing chart explaining an example of operation | movement of the conventional OFDM receiver. FIG. 3 is a diagram illustrating an internal configuration example of an average value calculation circuit in FIG. 2. FIG. 3 is a diagram illustrating an internal configuration example of an average value calculation circuit in FIG. 2. 10 is a timing chart for explaining another example of the operation of the conventional OFDM receiver. It is a block diagram which shows the structural example of the OFDM receiver as 1st Embodiment of the information processing apparatus with which this invention is applied. 8 is a timing chart for explaining an example of the operation of the OFDM receiving apparatus according to the first embodiment of FIG. 7. 8 is a flowchart for explaining an example of an OFDM demodulation process executed by the OFDM receiver of the first embodiment of FIG. 8 is a flowchart for explaining an example of a symbol synchronization signal output process executed by the OFDM receiver of the first embodiment of FIG. It is a block diagram which shows the structural example of the OFDM receiver as 2nd Embodiment of the information processing apparatus with which this invention is applied. It is a block diagram which shows the structural example of the OFDM receiver as 3rd Embodiment of the information processing apparatus to which this invention is applied. It is a block diagram which shows the structural example of the computer which runs the program with which this invention is applied.

Explanation of symbols

  101 antenna, 102 tuner, 103 band pass filter, 104 A / D conversion circuit, 105 quadrature demodulation circuit, 106 sampling / carrier frequency error correction circuit, 107 FFT operation circuit, 108 transmission path distortion correction circuit, 109 error correction Circuit, 110 effective symbol length delay circuit, 111 correlation detection circuit, 112, 112-1 to 112-N average value calculation circuit, 113 correction circuit, 114 guard interval length moving average circuit, 115 symbol timing recovery circuit, 116 frequency error detection Circuit, 120 division circuit, 121 minimum value selection circuit, 130 phase fluctuation estimation circuit, 131 phase fluctuation correction circuit, 210 display unit, 300, 400, 500 OFDM receiver, 601 CPU, 602 ROM, 603 RAM, 608 Storage unit, 611 removable media

Claims (9)

An Orthogonal Frequency Division Multiplexing system (OFDM system: Orthogonal Frequency Division Multiplexing system), in which an effective signal section in which a data signal is transmitted and a guard interval section in which the latter half of the effective signal section is copied as a redundant signal are configured as one symbol section Receiving means for receiving an OFDM signal generated based on
Delay means for delaying the OFDM signal received by the receiving means by an effective signal interval length;
Correlation value detection means for obtaining a complex correlation of the OFDM signal of each of the input and output of the delay means and outputting a correlation signal;
Sampling means for sampling N pieces (N is an integer value of 2 or more) of data from one symbol section of the correlation signal output from the correlation value detection means;
Generating means for generating N correction value candidates based on the N pieces of data collected by the collecting means;
Selection means for selecting a correction value based on a predetermined rule from the N correction value candidates generated by the generation means;
Correction means for correcting the correlation signal output from the correlation value detection means using the correction value selected by the selection means;
Symbol timing reproduction for detecting the leading timing of the effective signal section of the OFDM signal received by the receiving means using the correlation signal corrected by the correcting means and reproducing the symbol synchronization signal indicating the detection result Means,
Information processing comprising: FFT calculation means for performing FFT (Fast Fourier Transform) calculation processing on the OFDM signal received by the reception means with reference to the symbol synchronization signal reproduced by the symbol timing reproduction means apparatus. The sampling means divides one symbol section of the correlation signal into N, and samples each of the N-divided correlation signals as a divided correlation signal,
The information processing apparatus according to claim 1, wherein the generation unit generates an average value of each of the N divided correlation signals as the N correction candidates. The information processing apparatus according to claim 2, wherein the selection unit selects a minimum absolute value among the N correction value candidates as the correction value. A frequency error detecting means for detecting a frequency error using the correlation signal corrected by the correcting means and outputting the detection result;
2. The information processing apparatus according to claim 1, further comprising: a frequency error correction unit that corrects a frequency error of the OFDM signal newly received by the reception unit using the detection result of the frequency error detection unit as feedback information. . Phase fluctuation estimation means for estimating a phase fluctuation amount in one symbol using the correlation signal corrected by the correction means;
The phase fluctuation correction means for correcting the OFDM signal after the FFT calculation processing is performed by the FFT calculation means based on the phase fluctuation amount estimated by the phase fluctuation estimation means. The information processing apparatus described. Phase fluctuation estimation means for estimating a phase fluctuation amount in one symbol using the correlation signal corrected by the correction means;
The phase fluctuation correction means for correcting the OFDM signal before the FFT calculation processing is performed by the FFT calculation means based on the phase fluctuation amount estimated by the phase fluctuation estimation means. The information processing apparatus described. An Orthogonal Frequency Division Multiplexing system (OFDM system: Orthogonal Frequency Division Multiplexing system), in which an effective signal section in which a data signal is transmitted and a guard interval section in which the latter half of the effective signal section is copied as a redundant signal are configured as one symbol section ) To receive an OFDM signal generated based on
A delay step of delaying the received OFDM signal by an effective signal interval length;
A correlation value detection step for obtaining a complex correlation of each of the OFDM signals before and after the processing of the delay step and outputting a correlation signal;
A sampling step of sampling N pieces (N is an integer value of 2 or more) of data from one symbol section of the correlation signal output by the processing of the correlation value detection step;
A generation step for generating N correction value candidates based on the N pieces of data collected by the processing of the collection step;
A selection step of selecting a correction value based on a predetermined rule from the N correction value candidates generated by the processing of the generation step;
A correction step of correcting the correlation signal output by the processing of the correlation value detection step using the correction value selected by the processing of the selection step;
A symbol timing reproduction step of detecting a leading timing of the effective signal section of the received OFDM signal using the correlation signal corrected by the correction step, and reproducing a symbol synchronization signal indicating the detection result; ,
An FFT calculation step of performing FFT (Fast Fourier Transform) calculation processing on the received OFDM signal with reference to the symbol synchronization signal reproduced by the processing of the symbol timing reproduction step. An Orthogonal Frequency Division Multiplexing system (OFDM system: Orthogonal Frequency Division Multiplexing system), in which an effective signal section in which a data signal is transmitted and a guard interval section in which the latter half of the effective signal section is copied as a redundant signal are configured as one symbol section To the computer that controls the receiving device that receives the OFDM signal generated based on
A delay step of delaying the received OFDM signal by an effective signal interval length;
A correlation value detection step for obtaining a complex correlation of each of the OFDM signals before and after the processing of the delay step and outputting a correlation signal;
A sampling step of sampling N pieces (N is an integer value of 2 or more) of data from one symbol section of the correlation signal output by the processing of the correlation value detection step;
A generation step for generating N correction value candidates based on the N pieces of data collected by the processing of the collection step;
A selection step of selecting a correction value based on a predetermined rule from the N correction value candidates generated by the processing of the generation step;
A correction step of correcting the correlation signal output by the processing of the correlation value detection step using the correction value selected by the processing of the selection step;
A symbol timing reproduction step of detecting a leading timing of the effective signal section of the received OFDM signal using the correlation signal corrected by the correction step, and reproducing a symbol synchronization signal indicating the detection result; ,
An FFT calculation step that performs FFT (Fast Fourier Transform) calculation processing on the received OFDM signal with reference to the symbol synchronization signal reproduced by the symbol timing reproduction step processing is executed. Program to make. An Orthogonal Frequency Division Multiplexing system (OFDM system: Orthogonal Frequency Division Multiplexing system), in which an effective signal section in which a data signal is transmitted and a guard interval section in which the latter half of the effective signal section is copied as a redundant signal are configured as one symbol section Receiving means for receiving an OFDM signal generated based on
Delay means for delaying the OFDM signal received by the receiving means by an effective signal interval length;
Correlation value detection means for obtaining a complex correlation of the OFDM signal of each of the input and output of the delay means and outputting a correlation signal;
Sampling means for sampling N pieces (N is an integer value of 2 or more) of data from one symbol section of the correlation signal output from the correlation value detection means;
Based on the N pieces of data collected by the collection means, generating means for generating N correction value candidates;
Selection means for selecting a correction value based on a predetermined rule from the N correction value candidates generated by the generation means;
Correction means for correcting the correlation signal output from the correlation value detection means using the correction value selected by the selection means;
Symbol timing reproduction for detecting the leading timing of the effective signal section of the OFDM signal received by the receiving means using the correlation signal corrected by the correcting means and reproducing the symbol synchronization signal indicating the detection result Means,
FFT calculation means for performing FFT (Fast Fourier Transform) calculation processing on the OFDM signal received by the reception means with reference to the symbol synchronization signal reproduced by the symbol timing reproduction means;
A display device comprising: display means for displaying an image corresponding to the OFDM signal subjected to the FFT operation processing by the FFT operation means.

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