JP2008153775A - Symbol synchronizing device, symbol synchronizing method, and testing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a synchronization position of a symbol at a high speed with simple constitution. <P>SOLUTION: Disclosed is a symbol synchronizing device which detects the synchronization position of the symbol of an orthogonal frequency division multiplexing modulated signal (OFDM modulated signal) having a preamble symbol as a symbol including a predetermined signal, the symbol synchronizing device having a replica storage unit which stores a part of the preamble symbol as a replica signal, and a synchronization unit which detects the synchronization position of the symbol of the OFDM modulated signal to be synchronized based upon the correlation between the replica signal and a corresponding part of the OFDM modulated signal to be synchronized. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a symbol synchronization apparatus, a symbol synchronization method, and a test apparatus. In particular, the present invention relates to a symbol synchronization apparatus, a symbol synchronization method, and symbol synchronization for detecting a symbol synchronization position in an orthogonal frequency division multiplexing modulated signal (OFDM modulated signal) having a preamble symbol that is a symbol including a predetermined signal. The present invention relates to a test apparatus for testing a device under test using the apparatus.

  For example, in a communication standard such as a wireless LAN (IEEE802.11a, IEEE802.16e, UWB (Ultra Wide Band)), an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme is adopted. An OFDM communication apparatus employing the OFDM modulation scheme transmits and receives orthogonal frequency division multiplex modulation signals (hereinafter referred to as OFDM modulation signals). The OFDM communication apparatus generates an OFDM modulated signal by performing an IFFT (Inverse Fast Fourier Transform) operation on a plurality of data for each symbol on the transmitting side, and performs an FFT on each symbol for the OFDM modulated signal on the receiving side. (Fast Fourier transform) operation is performed to extract data modulated by each subcarrier.

  Here, the OFDM communication apparatus includes a symbol synchronization apparatus that detects a symbol synchronization position of the received OFDM modulation signal. The OFDM communication apparatus extracts data included in each symbol by performing an FFT operation on a range based on the synchronization position of the symbol.

  The symbol synchronizer stores a preamble symbol, which is a predetermined signal included in the OFDM modulated signal, as a replica signal. Then, the symbol synchronization apparatus searches for a position in the OFDM modulated signal having the highest correlation value with the replica signal, and determines a symbol synchronization position of the OFDM modulated signal based on the position obtained by the search.

As an example, the symbol synchronizer calculates the correlation value Corr by a calculation represented by the following formula (1). In Equation (1), Z is the sample value of the OFDM modulated signal, R ^* is the complex conjugate of the sample value of the replica signal, and Σ is the sum of the number of samples of the replica signal.

  That is, the symbol synchronizer multiplies the complex conjugate of the plurality of sample values of the replica signal and the plurality of sample values of the OFDM modulated signal by the sample values at the same position, and obtains a plurality of multiplication results obtained by multiplication. The numerator value obtained by adding and squaring the absolute value (the numerator value of the formula (1)) is calculated. Furthermore, the symbol synchronizer adds a value obtained by adding a square value of each absolute value of a plurality of sample values of the OFDM modulation signal and a value obtained by adding a value obtained by squaring the absolute values of the plurality of sample values of the replica signal. And the denominator value (value of the denominator in the equation (1)) is calculated. Then, the symbol synchronizer calculates the correlation value Corr by dividing the numerator value by the denominator value.

  Such a symbol synchronizer can calculate a correlation value from which the influence of fluctuations in the absolute value of the received signal is removed. Therefore, the symbol synchronizer can accurately detect the symbol synchronization position. In addition, since the presence of a prior art document is not recognized at this time, the description regarding a prior art document is abbreviate | omitted.

  By the way, it is desirable that the symbol synchronization apparatus can detect the symbol synchronization position at high speed with a simple configuration. However, since the above-described symbol synchronization apparatus calculates the correlation value by an operation including division, the amount of calculation is large.

  Therefore, an object of the present invention is to provide a symbol synchronization apparatus, a symbol synchronization method, and a test apparatus that can solve the above-described problems. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous specific examples of the present invention.

  In order to solve the above problem, in the first embodiment of the present invention, a symbol synchronization position is detected in an orthogonal frequency division multiplex modulation signal (OFDM modulation signal) having a preamble symbol that is a symbol including a predetermined signal. A symbol synchronizer that stores a part of a preamble symbol as a replica signal and an OFDM modulation to be synchronized based on a correlation between the replica signal and a corresponding part of the OFDM modulated signal to be synchronized Provided is a symbol synchronization device including a synchronization unit that detects a synchronization position of a symbol of a signal.

  According to a second aspect of the present invention, there is provided a symbol synchronization method for detecting a symbol synchronization position in an orthogonal frequency division multiplex modulation signal (OFDM modulation signal) having a preamble symbol that is a symbol including a predetermined signal, Provided is a symbol synchronization method for storing a replica signal including a part of a preamble symbol and detecting a synchronization position of a symbol of an OFDM modulated signal to be synchronized based on a correlation between the OFDM modulated signal to be synchronized and the replica signal. .

  According to a third aspect of the present invention, there is provided a test apparatus for testing a device under test, wherein an orthogonal frequency division multiplex modulation signal (OFDM modulation signal) having a preamble symbol which is a symbol including a predetermined signal is received. An input unit that inputs from the test device, an extraction unit that extracts a reception signal included in each of a plurality of subcarriers in the OFDM modulated signal for each symbol, a quality determination unit that determines the quality of the reception signal, and an OFDM modulation signal A symbol synchronizer that detects a symbol synchronization position in the symbol synchronization apparatus, the symbol synchronizer includes a replica storage unit that stores a replica signal including a part of a preamble symbol, and a correlation between an OFDM modulated signal and a replica signal to be synchronized And a synchronization unit for detecting the synchronization position of the symbol of the OFDM modulation signal to be synchronized, based on Providing a test device having.

  The above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the scope of claims, and all combinations of features described in the embodiments are included. It is not necessarily essential for the solution of the invention.

  FIG. 1 shows a configuration of a test apparatus 10 according to the present embodiment, together with a transmission apparatus 100 under test. The test apparatus 10 tests a device under test 100 that is an example of a device under test according to the present invention. The transmission apparatus under test 100 is a transmission apparatus that employs an OFDM modulation scheme, and outputs a transmission signal obtained by orthogonally modulating an orthogonal frequency division multiplexing (OFDM) modulation signal with a carrier signal having a predetermined frequency.

  The test apparatus 10 includes an output unit 12, an input unit 14, an extraction unit 16, a pass / fail determination unit 18, and a symbol synchronization device 20. The output unit 12 causes the transmission apparatus under test 100 to output a transmission signal obtained by modulating the OFDM modulated signal with a carrier signal. Here, the OFDM modulation signal has a preamble symbol that is a symbol including a predetermined signal. The output unit 12 may include a signal generation unit 122 as an example. The signal generator 122 supplies the transmission data to the transmission device under test 100 and causes the transmission device under test 100 to output a transmission signal.

  The input unit 14 receives the OFDM modulated signal output from the transmission apparatus under test 100. As an example, the input unit 14 may receive the transmission signal output from the transmission device under test 100, and input the OFDM modulated signal from the transmission device under test 100 by performing orthogonal demodulation on the received transmission signal.

  As an example, the input unit 14 may include a down converter 142, an AD conversion unit 144, an orthogonal demodulation unit 146, and a signal storage unit 148. The down converter 142 down-converts the carrier frequency of the transmission signal output from the transmission apparatus under test 100. The AD conversion unit 144 samples and digitizes the signal output from the down converter 142. The AD conversion unit 144 may directly sample and digitize the transmission signal output from the transmission apparatus under test 100 without using the down converter 142.

  The quadrature demodulator 146 performs quadrature demodulation on the signal digitized by the AD converter 144 by digital computation, and outputs a baseband OFDM modulated signal. The signal storage unit 148 sequentially stores the OFDM modulation signals output from the quadrature demodulation unit 146. As an example, the signal storage unit 148 sequentially stores each sample of the OFDM modulated signal output from the orthogonal demodulation unit 146 in the order of addresses.

  The extraction unit 16 extracts a reception signal included in each of a plurality of subcarriers in the OFDM modulated signal input from the input unit 14 for each symbol. For example, the extraction unit 16 may include an FFT operation unit 162. The FFT operation unit 162 takes out the sample points of the OFDM modulated signal stored in the signal storage unit 148 for each symbol, and performs an FFT (Fast Fourier Transform) operation. Thereby, the FFT calculation part 162 can extract the received value contained in each of a some subcarrier for every symbol.

  The quality determination unit 18 determines quality of the received signal extracted by the extraction unit 16. For example, the quality determination unit 18 may measure the EVM (Error Vector Magnitude) of the received signal to determine the quality of the received signal.

  The symbol synchronizer 20 detects a symbol synchronization position in the OFDM modulated signal input from the input unit 14. The symbol synchronization device 20 supplies the detected symbol synchronization position to the extraction unit 16. Thereby, the extraction part 16 can extract a received signal for every symbol from an OFDM modulation signal.

  The symbol synchronization device 20 includes a replica storage unit 22 and a synchronization unit 24. The replica storage unit 22 stores a replica signal including a part of the preamble symbol. That is, the replica storage unit 22 stores a sample value of a part of all samples constituting the preamble symbol as a replica signal. Further, as an example, the replica storage unit 22 may separately store the positions of some samples stored as replica signals in the preamble symbol.

  The synchronization unit 24 detects the symbol synchronization position of the OFDM modulated signal input by the input unit 14 to be synchronized based on the correlation between the OFDM modulated signal input by the input unit 14 to be synchronized and the replica signal. . According to such a symbol synchronizer 20, the symbol synchronization position can be detected at high speed with a simple configuration. The test apparatus 10 including the symbol synchronization apparatus 20 can test the transmission apparatus under test 100 at a high speed with a simple configuration.

  FIG. 2 shows an example of an OFDM modulated signal, a symbol of the OFDM modulated signal, and a synchronization position. An OFDM modulation signal is a signal in which symbols of a predetermined time length are continuous. Each symbol includes a transmission signal and a guard interval (GI) added before the transmission signal. The transmission signal includes a signal to be transmitted from the transmission side to the reception side. The transmission signal is a signal obtained by orthogonally modulating each of a plurality of frequency subcarriers with digital data. The guard interval is a signal having the same waveform as the last part of the transmission signal.

  In addition, the OFDM modulation signal includes a preamble symbol in a part of the plurality of symbols. In the preamble symbol, for example, a predetermined signal is modulated to each subcarrier, and as a result, a signal waveform in the time domain of the OFDM modulated signal is a predetermined waveform. The signal waveform of the preamble symbol is determined by, for example, a communication method.

  When extracting each received value of a plurality of subcarriers included in each symbol, the FFT operation unit 162 calculates, from each symbol, consecutive sample points corresponding to the length of the transmission signal (that is, the guard interval length from the symbol length). (Excluding consecutive sample points) is taken out and FFT operation is performed. In this case, the FFT operation unit 162 performs the FFT operation except for the vicinity of the symbol boundary where intersymbol interference may occur due to multipath or the like. It is preferred to take consecutive sample points.

  For example, the symbol synchronizer 20 may generate the address of the signal storage unit 148 for each symbol as a symbol synchronization position, and supply it to the FFT operation unit 162. On the condition that OFDM modulation signals are stored in order of address, the symbol synchronizer 20 stores the FFT calculation start address (for example, the address of the approximate center position of the guard interval of each symbol) as the symbol synchronization position. Part 148 may be supplied. Thereby, the signal storage unit 148 can extract the received value for each symbol by reading data of a predetermined number of samples from the address designated by the symbol synchronizer 20 and performing an FFT operation.

  The symbol synchronizer 20 sequentially extracts partial signals of the number and arrangement corresponding to the replica signal from the OFDM modulated signals stored in the signal storage unit 148. Then, the symbol synchronizer 20 calculates the correlation between the extracted partial signal and replica signal.

  Here, when the extracted partial signal is a signal at the same position as the replica signal, the correlation between the extracted partial signal and the replica signal is the highest. Therefore, the symbol synchronizer 20 searches for the peak position of the correlation between the extracted partial signal and replica signal, and uses the peak position obtained by the search as a reference to the symbol synchronization position (for example, the guard interval). Approximate center position) is detected.

Furthermore, as an example, the symbol synchronizer 20 may calculate a correlation value Corr indicating the correlation between the partial signal extracted from the OFDM modulated signal and the replica signal by an operation represented by the following equation (2). In Equation (2), Z is the sample value of the OFDM modulated signal, R ^* is the complex conjugate of the sample value of the replica signal, and Σ is the sum of the number of samples of the replica signal.

  That is, the symbol synchronizer 20 multiplies a plurality of sample values included in the partial signal and a complex conjugate of the plurality of sample values included in the replica signal by the sample values at the same position, and obtains a plurality of values obtained by multiplication. A value obtained by adding the multiplication results is calculated as a correlation value Corr. Thereby, the symbol synchronizer 20 can calculate a correlation value without dividing, and the arithmetic processing is simplified.

  FIG. 3 shows an example of a preamble symbol waveform and an example of a replica signal waveform. Further, the replica storage unit 22 may store a portion of the preamble symbol having the highest power as a replica signal.

  For example, when storing a part of a waveform (for example, a continuous waveform of a predetermined length) in a preamble symbol as a replica signal, the replica storage unit 22 stores a part having the highest total power of the part of the waveform as a replica signal. You can do it. That is, the replica storage unit 22 may use, as a replica signal, the waveform at the position where the power is highest in the case where the power is calculated by sequentially extracting some waveforms from the beginning to the end of the preamble symbol.

  By storing the portion with the highest power as a replica signal in this way, the symbol synchronizer 20 can set the peak position of the value calculated as in Equation (2) regardless of the magnitude of the power of the transmission signal. The position having the highest correlation with the replica signal can be obtained. Note that the replica storage unit 22 may store, as a replica signal, a portion in the preamble symbol in which the average power is higher than the average power of the entire preamble symbol.

  FIG. 4 shows an example of the configuration of the synchronization unit 24 together with the replica storage unit 22. As an example, the synchronization unit 24 may include a selection unit 32, a correlation value calculation unit 34, and a synchronization position detection unit 36. The selection unit 32 sequentially selects partial signals including a plurality of sample values in an arrangement corresponding to the replica signal from the OFDM modulated signals to be synchronized.

  The correlation value calculation unit 34 sequentially outputs the correlation values between the selected partial signal and the replica signal every time the selection unit 32 selects the partial signal. In this example, the correlation value calculation unit 34 multiplies the sample values included in the partial signal and the complex conjugate of the sample values included in the replica signal by the sample values at the same position, and obtains the result. A value obtained by adding the plurality of multiplication results is output as a correlation value.

  The correlation value calculation unit 34 may include, as an example, a complex conjugate conversion unit 40, a multiplication unit 42, and an addition unit 44. The complex conjugate conversion unit 40 converts a plurality of sample values included in the replica signal stored in the replica storage unit 22 into a complex conjugate and outputs the complex conjugate. The multiplying unit 42 multiplies the sample values selected by the selecting unit 32 and the complex conjugate of the plurality of sample values included in the replica signal by the sample values at the same position. The adder 44 adds a plurality of multiplication results from the multiplier 42 and outputs the result as a correlation value.

  The synchronization position detector 36 detects the synchronization position of the OFDM modulated signal to be synchronized based on a plurality of correlation values. As an example, the synchronization position detection unit 36 detects the peak value of the correlation value that is sequentially output each time a partial signal is selected by the selection unit 32. Then, the synchronization position detection unit 36 determines that the position of the partial signal having the peak correlation value is the position of the replica signal, and sets the position of the partial signal having the peak correlation value to the FFT calculation unit 162 as a reference. The symbol synchronization position (for example, the approximate center position of the guard interval) on the stored OFDM modulation signal is calculated.

  According to such a synchronization unit 24, since the synchronization position can be detected with a simple configuration, the synchronization position of the symbol can be detected at high speed by being configured by hardware. Note that the replica storage unit 22 may store each complex conjugate of a plurality of sample values included in the replica signal. In this case, the correlation value calculation unit 34 does not need to include the complex conjugate conversion unit 40, and the multiplication unit 42 stores each of the plurality of sample values selected by the selection unit 32 and the replica storage unit 22. Multiply the corresponding value directly.

  FIG. 5 shows an example of a replica signal. Instead of storing a continuous waveform of a predetermined length in a preamble symbol as a replica signal, as an example, the replica storage unit 22 uses a set of two or more non-consecutive sections in a preamble symbol as a replica signal as shown in FIG. May be stored as

  According to such symbol synchronizer 20, the power of the replica signal can be increased, and the peak value of the correlation value between the replica signal and the partial signal can be increased. As a result, the symbol synchronization device 20 can detect the symbol synchronization position with high accuracy.

  For example, the replica storage unit 22 may store, as a replica signal, a set of sections selected in descending order of power in the preamble symbol when the preamble symbol is divided into a plurality of sections. In this case, one section may be composed of one sample. Thereby, the symbol synchronizer 20 can maximize the power of the replica signal.

  FIG. 6 shows a configuration of the symbol synchronization apparatus 20 according to the first modification of the present embodiment. Since the configuration and function of the test apparatus 10 according to the present modification are substantially the same as those of the test apparatus 10 shown in FIG. 1, the configuration and function that are substantially the same as the members of the same reference numerals shown in FIG. Are denoted by the same reference numerals, and the description thereof will be omitted except for the following differences.

  The replica storage unit 22 according to this modification stores a plurality of replica signals corresponding to two or more types of preamble symbols. As an example, the replica storage unit 22 may store a plurality of replica signals corresponding to a plurality of preamble symbols according to the type of transmission signal transmitted by the transmission apparatus under test 100 and the type of operation mode. For example, the replica storage unit 22 may store replica signals having different signal contents and positions and lengths in the symbols corresponding to two or more kinds of preamble symbols.

  The synchronization unit 24 according to the present modification selects one replica signal from among a plurality of replica signals according to the content of the preamble symbol assumed to be included in the OFDM modulation signal to be synchronized, and obtains the correlation . As an example, the synchronization unit 24 may select any one of the replica signals according to the standard and operation mode of the transmission signal transmitted from the transmission apparatus under test 100. For example, the synchronization unit 24 may calculate a correlation value for all of a plurality of replica signals stored in the replica storage unit 22 and detect a symbol synchronization position from any one of the correlation values.

  According to the test apparatus 10 according to this modification, it is possible to detect symbol synchronization positions for a plurality of types of OFDM modulated signals. Therefore, according to the test apparatus 10 according to this modification, it is possible to test a plurality of types (for example, a plurality of standards and operation modes) of the transmission apparatus under test 100 without switching special settings.

  FIG. 7 shows a processing flow of the symbol synchronization apparatus 20 according to the second modification of the present embodiment. Since the test apparatus 10 according to the present modification has substantially the same configuration and function as the test apparatus 10 shown in FIG.

  The replica storage unit 22 according to this modification example includes a first replica signal that is a part of a preamble symbol and a second replica signal that is a part of the preamble symbol and has a sample value larger than that of the first replica signal. Remember. The replica storage unit 22 may store a part of the second replica signal as the first replica signal. Further, the replica storage unit 22 may store a common sample value for the first replica signal and the second replica signal in common.

  First, in step S1001, the synchronization unit 24 according to the present modification synchronizes the symbols of the OFDM modulated signal to be synchronized based on the correlation between the first replica signal and the corresponding portion of the OFDM modulated signal to be synchronized. Select multiple candidates for position. For example, the synchronization unit 24 selects, for example, a plurality of partial signals in descending order of the correlation value from the partial signals in which the correlation between the OFDM modulated signal and the first replica signal has reached a peak, and the plurality of selected partial signals A plurality of candidates for symbol synchronization positions are calculated from positions on the OFDM modulated signal.

  Next, in step S1002, the synchronization unit 24 according to this modification example uses a plurality of partial signals corresponding to the second replica signal corresponding to the synchronization positions of the plurality of candidates from the OFDM modulation signal to be synchronized. select. Then, the synchronization unit 24 detects the symbol synchronization position of the OFDM modulation signal to be synchronized based on the correlation between the second replica signal and each of the selected partial signals. As an example, the synchronization unit 24 calculates the symbol synchronization position from the position on the OFDM modulated signal of the partial signal having the highest correlation value with the second replica signal among the plurality of selected partial signals.

  According to the test apparatus 10 according to the present modification, the synchronization position of one symbol can be detected from a plurality of candidates narrowed down with a small amount of calculation. As a result, according to the test apparatus 10 according to the present modification, the symbol synchronization position can be accurately detected with a small amount of calculation.

  FIG. 8 shows the configuration of a test apparatus 10 according to a third modification of the present embodiment, together with the transmission apparatus under test 100. Since the test apparatus 10 according to the present modification has substantially the same configuration and function as the test apparatus 10 shown in FIG. 1, the same reference numerals are used for the same configurations and functions as those of the same reference numerals shown in FIG. The description will be omitted except for the differences.

  The test apparatus 10 further includes a trigger generator 52. The trigger generator 52 generates a trigger signal indicating the approximate position of the preamble symbol in the OFDM modulation signal to be synchronized. For example, the trigger generation unit 52 may generate a trigger signal indicating the timing at which a preamble symbol is generated from the transmission device under test 100 from transmission data supplied from the signal generation unit 122 to the transmission device under test 100.

  The synchronization unit 24 according to this modification selects a section assumed to include a preamble symbol from the OFDM modulated signal input from the input unit 14 from the trigger signal generated by the trigger generation unit 52. . Then, the synchronization unit 24 detects the symbol synchronization position of the OFDM modulation signal to be synchronized based on the correlation with the partial signal corresponding to the replica signal in the section selected based on the trigger signal. As an example, the synchronization unit 24 selects partial signals sequentially from the section of the OFDM signal selected based on the trigger signal, and assumes that the position of the partial signal having a peak correlation is the position of the replica signal. The symbol synchronization position above may be detected. According to the test apparatus 10 according to the present modification, the symbol synchronization position can be detected at high speed and with a small amount of calculation.

  FIG. 9 shows the configuration of a test apparatus 10 according to a fourth modification of the present embodiment, together with the receiving apparatus 200 under test. Since the test apparatus 10 according to the present modification has substantially the same configuration and function as the test apparatus 10 shown in FIG. 1, the same reference numerals are used for the same configurations and functions as those of the same reference numerals shown in FIG. The description will be omitted except for the differences.

  The test apparatus 10 according to this modification tests a test receiver 200 that is an example of a device under test according to the present invention. The receiving device under test 200 is a receiving device that employs an OFDM modulation method, receives a transmission signal obtained by modulating an OFDM modulated signal, and outputs a baseband OFDM modulated signal.

  In this modification, the output unit 12 generates a transmission signal obtained by modulating an OFDM modulation signal with a carrier signal. Then, the output unit 12 supplies the transmission signal to the receiver under test 200 for reception, and outputs an OFDM modulated signal obtained by orthogonally demodulating the transmission signal.

  For example, the output unit 12 may include a signal generation unit 122 and a transmission unit 124. The signal generator 122 generates transmission data. The transmission unit 124 converts the transmission data generated by the signal generation unit 122 into an OFDM modulated signal by performing, for example, IFFT, and generates a transmission signal obtained by orthogonally modulating the converted OFDM modulated signal with a carrier signal.

  In the present modification, the input unit 14 may include a signal storage unit 148. The signal storage unit 148 sequentially stores the OFDM modulated signals output from the receiver under test 200. For example, the signal storage unit 148 sequentially stores each sample of the OFDM modulated signal output from the receiver under test 200 in the order of addresses. According to the test apparatus 10 according to this modification as described above, the receiver under test 200 can be tested using the symbol synchronization apparatus 20 that detects the symbol synchronization position at high speed with a simple configuration.

  FIG. 10 shows a configuration of a test apparatus 10 according to a fifth modification of the present embodiment, together with an amplifier under test 300. Since the test apparatus 10 according to the present modification has substantially the same configuration and function as the test apparatus 10 shown in FIGS. 1 and 9, the configuration and functions substantially the same as those of the members having the same reference numerals shown in FIGS. Functions are denoted by the same reference numerals, and description thereof will be omitted except for differences.

  The test apparatus 10 according to this modification tests an amplifier under test apparatus 300 that is an example of a device under test according to the present invention. As an example, the amplifier under test 300 may be an amplifying device that is used in a transmitting device or a receiving device that employs an OFDM modulation scheme and transmits or receives a transmission signal in which an OFDM modulated signal is modulated.

  In this modification, the output unit 12 generates a transmission signal obtained by modulating an OFDM modulation signal with a carrier signal. Then, the output unit 12 supplies the transmission signal to the amplifier under test 300 for amplification, and outputs a signal obtained by amplifying the transmission signal.

  In this modification, the input unit 14 receives a transmission signal obtained by modulating an OFDM modulated signal, and outputs a baseband OFDM modulated signal. As an example, the input unit 14 may include a receiving unit 150 and a signal storage unit 148. The receiving unit 150 down-converts the carrier frequency of the transmission signal output from the amplifier under test 300, samples and digitizes it, orthogonally demodulates the digitized signal, and outputs a baseband OFDM modulated signal.

  The signal storage unit 148 sequentially stores the OFDM modulated signals output from the receiving unit 150. As an example, the signal storage unit 148 sequentially stores each sample of the OFDM modulated signal output from the receiving unit 150 in the order of addresses.

  According to the test apparatus 10 according to this modification as described above, the amplifier under test 300 can be tested using the symbol synchronization apparatus 20 that detects the symbol synchronization position at high speed with a simple configuration. The test apparatus 10 according to the present modification is used for a transmission apparatus or a reception apparatus that employs the OFDM modulation method in place of or in addition to the amplifier under test 300 or in addition to the amplifier under test 300. A downconverter that downconverts the carrier frequency or an upconverter that upconverts may be tested.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

1 shows a configuration of a test apparatus 10 according to an embodiment of the present invention, together with a transmission apparatus under test 100. An example of an OFDM modulation signal, a symbol of the OFDM modulation signal, and a synchronization position is shown. An example of the waveform of a preamble symbol and an example of the waveform of a replica signal are shown. An example of the configuration of the synchronization unit 24 is shown together with the replica storage unit 22. An example of a replica signal is shown. The structure of the symbol synchronizer 20 which concerns on the 1st modification of this embodiment is shown. The processing flow of the symbol synchronizer 20 which concerns on the 2nd modification of this embodiment is shown. The structure of the test apparatus 10 which concerns on the 3rd modification of this embodiment is shown with the to-be-transmitted transmitter 100. FIG. The structure of the test apparatus 10 which concerns on the 4th modification of this embodiment is shown with the to-be-tested receiving apparatus 200. FIG. The structure of the test apparatus 10 which concerns on the 5th modification of this embodiment is shown with the to-be-tested amplifier 300. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Test apparatus 12 Output part 14 Input part 16 Extraction part 18 Pass / fail judgment part 20 Symbol synchronization apparatus 22 Replica storage part 24 Synchronization part 32 Selection part 34 Correlation value calculation part 36 Synchronization position detection part 40 Complex conjugate conversion part 42 Multiplication part 44 Addition Unit 52 trigger generation unit 100 transmission device under test 122 signal generation unit 124 transmission unit 142 downconverter 144 AD conversion unit 146 quadrature demodulation unit 148 signal storage unit 150 reception unit 162 FFT operation unit 200 device under test 300 device under test 300 device under test

Claims (11)

A symbol synchronization device for detecting a symbol synchronization position in an orthogonal frequency division multiplexing modulated signal (OFDM modulated signal) having a preamble symbol that is a symbol including a predetermined signal,
A replica storage unit for storing a part of the preamble symbol as a replica signal;
A symbol synchronization apparatus comprising: a synchronization unit that detects a synchronization position of a symbol of the OFDM modulation signal to be synchronized based on a correlation between the replica signal and a corresponding portion of the OFDM modulation signal to be synchronized. The symbol synchronization device according to claim 1, wherein the replica storage unit stores a portion of the preamble symbol having the highest power as a replica signal. The symbol synchronization device according to claim 1, wherein the replica storage unit stores a portion in the preamble symbol in which the average power is higher than an average power of the entire preamble symbol as a replica signal. The synchronization unit is
A selection unit that sequentially selects a partial signal including a plurality of sample values in an arrangement corresponding to the replica signal from the OFDM modulation signal to be synchronized;
A correlation value calculating unit that sequentially calculates a plurality of correlation values between each of the selected partial signals and the replica signal;
A synchronization position detector that detects a synchronization position of the OFDM modulation signal to be synchronized based on a plurality of the correlation values;
The correlation value calculation unit
A value obtained by multiplying a plurality of sample values included in the partial signal and a complex conjugate of the plurality of sample values included in the replica signal by sample values at the same position, and adding a plurality of multiplication results obtained by multiplication. The symbol synchronization apparatus according to claim 2, wherein: The symbol synchronization device according to claim 1, wherein the replica storage unit stores a set of two or more non-consecutive sections in the preamble symbol as a replica signal. The symbol synchronization device according to claim 5, wherein the replica storage unit stores the set of sections selected in descending order of power in the preamble symbol as a replica signal. The replica storage unit stores a plurality of replica signals corresponding to two or more kinds of the preamble symbols,
The synchronization unit selects one replica signal from a plurality of the replica signals according to the content of the preamble symbol assumed to be included in the OFDM modulation signal to be synchronized, and obtains the correlation. The symbol synchronizer according to 1. The replica storage unit stores a first replica signal that is a part of the preamble symbol and a second replica signal that is a part of the preamble symbol and has more sample values than the first replica signal. ,
The synchronization unit is
Based on the correlation between the first replica signal and the corresponding portion of the OFDM modulated signal to be synchronized, a plurality of candidates for the synchronization position of the symbol of the OFDM modulated signal to be synchronized is selected,
Selecting a plurality of portions corresponding to the second replica signal according to the respective synchronization positions of the plurality of candidates from the OFDM modulated signal to be synchronized;
The symbol synchronization apparatus according to claim 1, wherein a synchronization position of a symbol of the OFDM modulation signal to be synchronized is detected based on a correlation between the second replica signal and each of the selected plurality of portions. A symbol synchronization method for detecting a symbol synchronization position in an orthogonal frequency division multiplexing modulated signal (OFDM modulated signal) having a preamble symbol that is a symbol including a predetermined signal,
Storing a replica signal including a part of the preamble symbol;
A symbol synchronization method for detecting a synchronization position of a symbol of an OFDM modulation signal to be synchronized based on a correlation between the OFDM modulation signal to be synchronized and the replica signal. A test apparatus for testing a device under test,
An input unit for inputting an orthogonal frequency division multiplex modulation signal (OFDM modulation signal) having a preamble symbol which is a symbol including a predetermined signal from the device under test;
An extraction unit that extracts, for each symbol, a received signal included in each of a plurality of subcarriers in the OFDM modulated signal;
A pass / fail judgment unit for judging pass / fail of the received signal;
A symbol synchronizer for detecting a symbol synchronization position in the OFDM modulated signal;
The symbol synchronizer is
A replica storage unit for storing a replica signal including a part of the preamble symbol;
A test apparatus comprising: a synchronization unit that detects a synchronization position of a symbol of the OFDM modulation signal to be synchronized based on a correlation between the OFDM modulation signal to be synchronized and the replica signal. The synchronization unit is
Based on the correlation between the replica signal and the corresponding part of the section selected based on the trigger signal indicating the approximate position of the preamble symbol in the OFDM modulation signal to be synchronized, the synchronization of the symbol of the OFDM modulation signal to be synchronized The test apparatus according to claim 10, wherein the position is detected.

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