JP2005295446A - Device and program for detecting disturbance wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disturbance wave detecting device and a disturbance wave detecting program capable of detecting/measuring a disturbance wave, without using a special receiver, even when the disturbance wave is hidden behind the waveform of an OFDM wave. <P>SOLUTION: After frequency conversion of the OFDM wave received by an OFDM wave receiving set 2 is performed, and it is converted into a digital signal, the disturbance wave detecting device 1 receives the digital signal as an input, and detects the disturbance wave existing being mixed in an OFDM wave band, and is provided with a symbol cut-out means 3, summation/average calculating means 5, a histogram forming means 7, an disturbance wave determination means 9, and a disturbance wave waveform output means 11. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an interference wave detection apparatus and an interference wave detection program for detecting an interference wave mixed in an OFDM wave band in connection with reception of an OFDM wave.

  Conventionally, an OFDM (Orthogonal Frequency Division Multiplexing) wave is received, and a receiver having an FFT (Fast Fourier Transform) output is used to use a signal from the FFT output of the receiver. In addition, an apparatus for detecting and measuring an interfering wave buried (mixed) in the OFDM wave band (hereinafter referred to as a conventional interfering wave detecting apparatus) is realized (for example, Patent Document 1 and Non-Patent Document). Reference 1).

  In general, the interference wave buried in the OFDM wave band can be detected by measuring the modulation error amplitude (MER), but the D / U (Desireed to Undesired Ratio) of the interference wave. ) And the like are known to be impossible because the cause of the error that occurs when demodulating the received OFDM wave cannot be specified.

JP 2003-110509 A (paragraphs 0031 to 0039, FIG. 1) Minoru Minakami “Detection of jamming wave in OFDM band using FFT signal before equalization” ITE Technical Report Vol. 27, no. 17, PP. 21-24 (Mar. 2003)

  However, although the conventional interference wave detection apparatus uses a signal from the FFT output of the receiver, a general-purpose receiver currently on the market does not have the FFT output, and the interference wave of the OFDM wave There is a problem that the signal from the FFT output of the receiver cannot be used for detection of.

  In addition, in order to reliably transmit the OFDM wave, when an interference wave is generated in the OFDM wave band by a continuous wave (CW) such as a booster oscillation or an analog wave, a measuring instrument such as a spectrum analyzer is used. It is necessary to detect the interference wave and measure the frequency and D / U of the detected interference wave or the arrival direction of the interference wave. However, the interference wave is hidden in the waveform of the OFDM wave and is detected and measured. There is a problem that it is impossible.

  Therefore, the present invention solves the above-described problems and can detect and measure even if the interference wave is hidden in the waveform of the OFDM wave without using the signal from the FFT output of the receiver. An object is to provide a device and a jamming wave detection program.

  In order to solve the above-mentioned problem, the interference wave detection device according to claim 1, wherein the OFDM wave received by the reception device is frequency-converted and converted into a digital signal, and then the digital signal is used as an input to input the OFDM wave band. An interference wave detection device for detecting an interference wave mixed in the apparatus includes a sample data extraction unit, an addition unit, a frequency distribution calculation unit, and an interference wave determination unit.

  According to such a configuration, the interference wave detection device synchronizes the OFDM wave symbol from the input digital signal by the sample data extraction means, detects the symbol start point indicating the start of the symbol, and performs Fourier transform Cut out sample data necessary for. The digital signal is down-converted by the OFDM wave receiving means, frequency converting means, and analog-digital converting means provided in the receiving device, and the received time-domain OFDM wave (OFDM signal) is converted to AD. It has been done. Further, as shown in the constellation (signal arrangement diagram), the carrier wave (carrier) of the OFDM wave (OFDM signal) is arranged at a specific code point for each symbol. The next symbol) is discontinuous and can be said to be substantially uncorrelated in each symbol section (all data in the symbol). On the other hand, interference waves such as CW (sustained wave) due to booster oscillation or the like are continuous at symbol boundaries and have substantially constant amplitude and frequency. Taking advantage of this difference, the sample data extraction means synchronizes the symbols of the digital signal (AD converted OFDM signal) and extracts (extracts) the sample data in units.

  Subsequently, the interference wave detection device repeats the process of calculating the power spectrum by performing Fourier transform on the sample data cut out by the sample data cut-out means by the adding means by the number of cut-out sample data, A value (added value) obtained by adding the power spectra is calculated. What is calculated by this adding means is an added value of the power (power spectrum) for each spectrum, and by adding this, the component of the interference wave buried in the waveform of the OFDM wave (OFDM signal waveform) is detected. ing.

  And this interference wave detection apparatus sorts the addition value of the power spectrum calculated by the addition means by the frequency distribution calculation means (descending order or ascending order), and extracts the maximum number (peak value) of an arbitrary number, The frequency distribution of the appearance position of the maximum value is calculated by repeating a preset number of times. The number of times of setting can be arbitrarily set in relation to the detection accuracy of the interference wave and the time required to detect the interference wave. In other words, the addition values of the power spectrum calculated by the adding means are rearranged in descending order, an arbitrary number is extracted from the rearranged maximum values, and the extraction of the maximum values is repeatedly performed for the set number of times. The frequency distribution of appearance positions is calculated. For example, when the arbitrary number (arbitrary location) of the maximum value is 15 locations, when the number of repetitions is set to 20 times, the frequency distribution calculating means rearranges the addition values of the power spectrum in descending order, The top 15 appearance positions (frequency positions) are detected from the value, and this process is repeated 20 times. That is, the number of data of the created frequency distribution is an arbitrary number of maximum values (15 places) × the number of repetitions set (20 times) = 300, and the frequency of these 300 data is counted for each appearance position. Will be.

  And this interference wave detection apparatus determines with the interference wave determination means, when the frequency of the appearance position in the frequency distribution calculated by the frequency distribution calculation means exceeds a preset threshold value. The threshold value can be based on the set number of repetitions, or can be set to half of the set number (it is an arbitrary number).

  The interference wave detection device according to claim 2 is the interference wave detection device according to claim 1, further comprising interference wave waveform output means.

  According to such a configuration, the interference wave detection device calculates the interference wave waveform by calculating the frequency position and DU ratio of the interference wave based on the determination result of the interference wave determination means by the interference wave waveform output means. The calculated result and the obtained waveform of the disturbing wave are output to the display device. That is, the interference wave waveform output means displays the calculation result on the display device and draws the waveform of the interference wave.

  The interference wave detection program according to claim 3, wherein the OFDM wave received by the receiving device is frequency-converted and converted into a digital signal, and then the interference is mixed in the OFDM wave band using the digital signal as an input. The apparatus for detecting a wave is configured to function as sample data extraction means, addition means, frequency distribution calculation means, and interference wave determination means.

  According to such a configuration, the interference wave detection program synchronizes the OFDM wave symbol from the input digital signal by the sample data extraction means, detects the symbol start point indicating the start of the symbol, and performs Fourier transform. Cut out sample data necessary for. Subsequently, the interference wave detection program repeats the process of calculating the power spectrum by performing Fourier transform on the sample data cut out by the sample data cut-out means by the adding means by the number of cut-out sample data. Calculate the sum of the power spectrum. And this interference wave detection program sorts the addition value of the power spectrum calculated by the addition means by the frequency distribution calculation means, and repeats the process of extracting an arbitrary number of maximum values a preset number of times, The frequency distribution of the appearance position of the maximum value is calculated. Then, the interference wave detection program determines that the interference wave is detected as an interference wave when the frequency of the appearance position in the frequency distribution calculated by the frequency distribution calculation means exceeds a preset threshold.

  The interference wave detection program according to claim 4 is the interference wave detection program according to claim 3, characterized in that it has an interference wave waveform output means.

  According to such a configuration, the jamming wave detection program calculates the jamming wave waveform by calculating the frequency position and DU ratio of the jamming wave based on the judgment result by the jamming wave judgment unit by the jamming wave waveform output unit. The calculated result and the obtained waveform of the disturbing wave are output to the display device.

  According to the first and third aspects of the present invention, a digital signal obtained by receiving an OFDM wave, frequency-converting and AD-converting is input, and sampling data obtained by synchronizing the OFDM wave symbol from the digital signal is input. Since the Fourier transform is performed, a signal from the FFT output of the receiving device is not used. In addition, the frequency distribution of the added value of the power spectrum is obtained, and each frequency of the frequency distribution is compared with a threshold value to detect an interference wave hidden in the waveform of the OFDM wave in a measuring instrument such as a conventional spectrum analyzer. be able to.

  According to the second and fourth aspects of the invention, the frequency position and DU ratio of the disturbing wave are calculated to obtain the disturbing wave waveform, and the calculated calculation result and the obtained disturbing wave waveform are output to the display device. Therefore, the interference wave hidden behind the waveform of the OFDM wave can be measured (observed) by a conventional measuring instrument such as a spectrum analyzer.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
FIG. 1 is a block diagram of an interference wave detection system. As shown in FIG. 1, the interference wave detection system A includes an OFDM wave reception device 2, an interference wave detection device 1, and a display device 10.
The interfering wave detection system A detects an interfering wave buried (mixed) in the OFDM wave received by the OFDM wave receiving device 2 by the interfering wave detecting device 1, and displays the detection result on the display device 10. It is something to be made.

Prior to the description of the configuration of the interference wave detecting device 1, the OFDM wave receiving device 2 and the display device 10 will be described.
The OFDM wave receiving device 2 receives an OFDM wave (OFDM signal) and converts the OFDM wave into a digital signal that can be processed by the interference wave detecting device 1, and includes an OFDM wave receiving unit 4 and a frequency converting unit. 6 and analog-to-digital conversion means 8.

  The OFDM wave receiving means 4 receives an OFDM wave propagating in space as a broadcast wave for terrestrial digital broadcasting, and includes a reception antenna, an amplification circuit, a detection circuit, etc. (not shown). . The OFDM wave (OFDM signal) received by the OFDM wave receiving means 4 is output to the frequency converting means 6.

  The frequency converting means 6 converts the frequency band of the OFDM wave (OFDM signal) received by the OFDM wave receiving means 4 into a lower frequency band, so-called down-conversion. The frequency band signal (analog signal) converted by the frequency conversion means 6 is output to the analog-digital conversion means 8.

  The analog-digital conversion means 8 converts the OFDM wave (OFDM signal) whose frequency band has been converted (decreased) by the frequency conversion means 6 into a digital signal. The digital signal converted by the analog / digital conversion means 8 is output to the interference wave detecting device 1.

  The OFDM wave receiving apparatus 2 can be configured by assembling a separate broadcast wave receiving circuit, a separate frequency conversion circuit, a separate A / D conversion apparatus, and the like. It has the same function as an OFDM wave receiver.

  The display device 10 is configured by a display such as liquid crystal or plasma, and displays information (calculation result, waveform of interference wave) output from the interference wave detection device 1. In this embodiment, the display device 10 is handled as an independent and separate device, but may be provided integrally with the interference wave detection device 1.

<Configuration of interference detector>
Now, the configuration of the interference wave detection device 1 will be described.
The interference wave detection device 1 receives the OFDM wave (OFDM signal) converted into the digital signal converted by the OFDM wave reception device 2 and detects the interference wave buried (mixed) in the OFDM wave band. A symbol cut-out means (sample data cut-out means) 3, an addition average calculation means (addition means) 5, a histogram creation means (frequency distribution calculation means) 7, an interference wave determination means 9, and an interference wave waveform Output means 11.
Incidentally, the interference wave that can be detected by the interference wave detection device 1 indicates a CW (sustained wave) by booster oscillation or the like, an analog wave that is a broadcast wave of terrestrial analog broadcasting, or the like.

  The symbol cutout means (sample data cutout means) 3 detects the symbol start point indicating the start of the symbol by synchronizing the symbol of the OFDM wave (OFDM signal) from the input digital signal, A symbol is cut out (extracted). In this embodiment, the symbol cutout unit 3 cuts out a symbol (effective symbol) based on the symbol start point. However, the symbol cutout unit 3 is not limited to the symbol, and the data that can be Fourier transformed by the addition average calculation unit 5 is used. (Sample data) may be used.

  The carrier wave of the OFDM wave reaches several hundreds to thousands (so-called multi-carrier) and carries information to be distributed in a distributed manner. The modulation method of each carrier wave is QAM such as 64 QAM (64 Quadrature Amplitude Modulation). The method is adopted.

  A symbol (effective symbol) is a minimum structural unit of information propagated by an OFDM wave, and each symbol is usually provided to prevent an influence (interference) due to a delayed wave or a reflected wave of the OFDM wave. It is delimited by a guard interval that is a buffer time.

  The symbol start point indicates a point at which a transition from the guide interval to the symbol occurs when a plurality of symbols (effective symbols) continue through the guard interval. Since the guard interval is a part of the symbol (end part) copied and added to the symbol, by detecting the copied part, a portion continuing to the copied part is determined as the symbol start point. It will be.

  The addition average calculation means 5 performs the process of calculating the power spectrum by performing the fast Fourier transform (FFT) on the symbols cut (extracted) by the symbol cut-out means 3 and performing the number of the cut-out symbols. Thus, an average of the power spectrum is calculated. In this embodiment, the power spectrum addition average (addition average value) is calculated in order to facilitate the following processing (after the histogram creation means 7), but the power value is calculated without calculating the average value. The aspect which calculates | requires the addition value which added the spectra may be sufficient.

  The fast Fourier transform classifies input information (waveform) into samples and performs spectrum analysis. Here, the input symbols are converted into a power spectrum which is a power spectrum.

  The power spectrum is obtained by sequentially arranging the frequency component (frequency position) included in the symbol and the amplitude value of power for each symbol according to the magnitude of the frequency.

  The average addition of the power spectrum is to take the average by adding the power amplitude values for each frequency component of each symbol by the number of extracted symbols (the number of symbols).

  The histogram creation means (frequency distribution calculation means) 7 rearranges (sorts) the power spectrum that has been averaged by the addition average calculation means 5 in descending order (from the largest value to the smallest value) to obtain an arbitrary number of maximum values. The process of extracting (peak value) is repeated for a preset number of times to create a frequency distribution (histogram) of the appearance position (frequency position) of the maximum value.

  In this embodiment, the arbitrary number is 10 and the frequency position in the amplitude value (peak value) of power for 10 points is obtained. Further, the set number of times is 10, and the same processing is repeatedly executed for the digital signal input to the symbol cutout means 3 for 10 times.

  The interference wave determination means 9 compares the frequency of the appearance position in the histogram (frequency distribution of the appearance position of the maximum value) created by the histogram creation means 7 with a preset threshold value, thereby comparing the frequency in the histogram (frequency distribution). It is determined whether or not the appearance position (frequency position) includes an interference wave.

  When the interference wave determination means 9 determines that the interference wave is included in the appearance position (frequency position) in the histogram, the interference wave waveform output means 11 has a frequency component (frequency position) of this average value. Then, D / U is calculated to obtain the waveform of the interference wave, and the calculated calculation result and the waveform of the interference wave are output to the display device 10.

  The interference wave waveform output means 11 detects the frequency component (frequency position) of the addition average value based on the histogram created by the histogram creation means 7. Further, D / U is the sum of the power spectra (total power value) that has been added and averaged by the averaging means 5 and not detected by the histogram generator 7, and the power spectrum detected by the histogram generator 7 is divided by ( Subtracted in decibels).

  The interference wave waveform is drawn by the interference wave waveform output means 11 using the frequency component (frequency position) of the addition average value and D / U (DU ratio). That is, when the horizontal axis is the frequency axis and the vertical axis is the power amplitude axis, the position on the frequency axis is determined by the frequency component (frequency position), and the ratio of the amplitude with the original OFDM wave is determined by D / U. Since the (amplitude value) is obtained and the position on the amplitude axis is determined, the waveform of the interference wave is determined.

  According to the interference wave detecting device 1, the symbol cutout unit 3 synchronizes the OFDM wave symbol from the input digital signal, detects the symbol start point indicating the start of the symbol, and detects the symbol. Cut out (extracted). Subsequently, the process of calculating the power spectrum by Fourier-transforming the symbol extracted by the symbol extracting means 3 by the addition average calculating means 5 is repeated for the number of extracted symbols, thereby adding the power spectrum. An average is calculated. Then, the histogram generating means 7 sorts the power spectrum addition averages calculated by the addition average calculating means 5 in descending order, and extracts a rearranged arbitrary number of maximum values (peak values) in advance. A histogram indicating the frequency distribution of the appearance position (frequency position) of the maximum value is created by repeating the set number of times (10). Then, the interference wave determination means 9 compares the frequency of the appearance position in the histogram created by the histogram creation means 7 with the threshold value to determine whether or not it is an interference wave. Thereafter, the interfering wave waveform output means 11 calculates the interfering wave frequency position and D / U based on the determination result by the interfering wave determining means 9 to obtain the interfering wave waveform, and the calculation result and the interfering wave waveform are calculated. Is output to the display device 10. For this reason, when an OFDM wave reception failure occurs due to the influence of a CW (sustained wave) due to booster oscillation or the like, or an interference wave such as analog wave interference, the frequency (position of the frequency) of the interference wave, D / U, etc. Can be detected and measured. And it becomes possible to estimate the generation source of an interference wave using this interference wave detection apparatus 1, and to implement some countermeasures.

<Operation of interference detection system>
Next, the operation of the interference wave detection system A (including the operation of the interference wave detection device 1) will be described with reference to the flowchart shown in FIG. 2 (see FIG. 1 as appropriate).
First, the OFDM wave receiving apparatus 2 receives the propagating OFDM wave by the OFDM wave receiving means 4 (step S1). Subsequently, the OFDM wave receiver 2 down-converts the frequency band of the OFDM wave (OFDM signal) by the frequency conversion means 6 (converts it to a low band) (step S2). Then, the OFDM wave receiving apparatus 2 converts the OFDM signal, which is an analog signal, into a digital signal by the analog / digital conversion means 8 (step S3). Then, the OFDM wave receiving device 2 outputs the converted digital signal to the interference wave detecting device 1.

  Then, the interference wave detection device 1 synchronizes the symbols arranged on each carrier wave of the OFDM wave from the input digital signal by the symbol cutout means 3 (step S4).

  Then, the interference wave detection device 1 cuts out the symbol by the symbol cutout unit 3 (step S5), and performs FFT (fast Fourier transform) on the cut out symbol by the addition average calculation unit 5 (step S6). The power spectrum of each symbol is calculated (step S7). Then, the interference wave detection device 1 determines whether or not the calculation of the power spectrum has reached the number of extracted symbols by the addition average calculation means 5 (step S8). That is, it is determined whether the calculation of the power spectrum for the number of symbols is completed.

  Then, the interference wave detecting device 1 repeatedly executes Steps S5 to S7 until the addition average calculation unit 5 determines that the calculation of the power spectrum has reached the number of extracted symbols (No in Step S8). When it is determined that the number of symbols has been reached (Yes in step S8), the interfering wave detection device 1 calculates the addition average of the power spectrum by the addition average calculation means 5 (step S9).

  Subsequently, the interference wave detection device 1 sorts the addition average of the power spectra in descending order by the histogram creation means 7 to detect an arbitrary number (here, 10) of maximum values (peak values) (step S10). ), A histogram counting the frequency position where the maximum value is detected is created (step S11). Then, the interfering wave detection device 1 determines whether or not the processing from step S4 to step S11 has reached the preset number of times by the histogram creating means 7 (step S12), and until it is determined that the processing has been reached. (Step S12, No) The process is repeated.

  When it is determined that the processing from step S4 to step S11 has reached the preset number of times (step S12, Yes), the interference wave detection device 1 uses the interference wave determination means 9 to display the frequency position (appearance) in the histogram. When the frequency of (position) exceeds (exceeds) a preset threshold value, it is detected that an interference wave is included in the frequency position (appearance position) in the histogram (step S13).

  Then, the interference wave detection device 1 calculates the frequency position of the histogram and D / U (DU ratio) detected by the interference wave waveform output means 11 as including the interference wave (step S14). The waveform of the wave is obtained and output (drawn) to the display device 10 (step S15).

<How to detect jamming waves>
Next, with reference to FIG. 3, a method for detecting the interference wave by the interference wave detection device 1 will be described (see FIG. 1 as appropriate).
FIG. 3 is a diagram for explaining a concept when detecting an interference wave.

  As shown in FIG. 3, for the symbol n, symbol n + 1, symbol n + 2 and symbol n + 3, which are four symbols cut out by the symbol cutout means 3, the addition average calculation means 5 calculates the addition average, and this addition average In the histogram in which is calculated, the protruding portion corresponds to an interference wave.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, in the present embodiment, the jamming wave detection device 1 included in the jamming wave detection system A has been described. However, the jamming wave in which the processing of each component of the jamming wave detection device 1 is described in a general-purpose or special computer language. It can be regarded as a detection program, or it can be regarded as a jamming wave detection method in which the processing of each configuration is regarded as one process for detecting jamming waves from OFDM waves. In these cases, the same effect as the interference wave detection device 1 can be obtained.

1 is a block diagram of an interference wave detection system (including an interference wave detection device) according to an embodiment of the present invention. It is the flowchart explaining operation | movement of the jamming wave detection system (a jamming wave detection apparatus is included) shown in FIG. It is a figure explaining the concept at the time of detecting an interference wave.

Explanation of symbols

1 Interference wave detection device 3 Symbol extraction means (sample data extraction means)
5 addition average calculation means (addition means)
7 Histogram creation means (frequency distribution calculation means)
9 Interference wave judgment means 11 Interference wave waveform output means

Claims (4)

An interference wave detection device for detecting an interference wave mixed in the OFDM wave band using the digital signal as an input after the OFDM wave received by the reception device is frequency converted and converted into a digital signal. ,
Sample data extraction means for synchronizing symbols of the OFDM wave from the digital signal, detecting a symbol start point indicating the start of the symbol, and extracting sample data necessary for Fourier transform;
An adding means for calculating the power spectrum by repeating the process of calculating the power spectrum by Fourier transforming the sample data cut out by the sample data cutting means, and calculating the addition value of the power spectrum,
The frequency for calculating the frequency distribution of the appearance position of the maximum value by repeating the process of sorting the added value of the power spectrum calculated by the adding means and extracting an arbitrary number of maximum values for a preset number of times. Distribution calculation means;
When the frequency of the appearance position in the frequency distribution calculated by the frequency distribution calculating unit exceeds a preset threshold value, an interference wave determining unit that determines the interference wave,
An interference wave detecting device comprising:   Based on the determination result by the interference wave determination means, the frequency position and DU ratio of the interference wave are calculated to determine the waveform of the interference wave, and the calculated calculation result and the waveform of the determined interference wave are output to the display device. The interference wave detection device according to claim 1, further comprising an interference wave waveform output unit. An OFDM wave received by the receiving device is frequency-converted and converted into a digital signal, and the digital signal is used as an input to detect an interference wave mixed in the OFDM wave band.
Sample data extraction means for synchronizing symbols of the OFDM wave from the digital signal, detecting a symbol start point indicating the start of the symbol, and extracting sample data necessary for Fourier transform;
Addition means for calculating the power spectrum by repeating the process of calculating the power spectrum by Fourier transforming the sample data cut out by the sample data cutting means, and calculating the added value of the power spectrum,
The frequency for calculating the frequency distribution of the appearance position of the maximum value by repeating the process of sorting the added value of the power spectrum calculated by the adding means and extracting an arbitrary number of maximum values for a preset number of times. Distribution calculation means,
An interference wave determination means for determining the interference wave when the frequency of the appearance position in the frequency distribution calculated by the frequency distribution calculation means exceeds a preset threshold;
Interference wave detection program characterized by functioning as Based on the determination result by the interference wave determination means, the frequency position and DU ratio of the interference wave are calculated to determine the waveform of the interference wave, and the calculated calculation result and the waveform of the determined interference wave are output to the display device. The program for detecting an interference wave according to claim 3, further comprising an interference wave waveform output means.

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