JP2009186241A - Receiving device range-finding system, positioning system, computer program, and reception time point determining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiving set for determining the reception time point of a signal with higher accuracy, a range finding system and a positioning system that uses the receiving set, a computer program, and a reception time point determining method. <P>SOLUTION: In this receiving set 1, a delay signal estimating part 14 is used for analyzing/estimating a delay signal, having arrived later than a received signal and superimposed thereon. A reproduced signal preparing part 15 is used for preparing/outputting a reproduced signal for reproducing a reference signal with the effect of the delay signal reflected therein, based on a replica signal, which is contained in a transmitted signal and which is a replica of the reference signal, and on the delay signal estimated by the estimation part 14. A correlation between the received signal and the reproduced signal is found by means of a second matched filter 16, and the receiving time point is determined by means of a received signal determining part 17. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a positioning technique for measuring the position of a moving body from the time required for transmission / reception of radio waves, and in particular, a receiving device that can specify the reception time point of a transmitted signal with higher accuracy, and a measurement including the receiving device. The present invention relates to a distance system, a positioning system, a computer program, and a reception time specifying method.

  Various methods have been proposed to realize the position detection of the moving body with higher accuracy. Japanese Patent Application Laid-Open No. 2004-228688 discloses a technique for improving the accuracy by removing the influence of multipath and phase shift when detecting the position by calculating the distance from the arrival time difference of the radio wave from the radio wave source. Patent Document 2 discloses a technique for receiving a plurality of radio waves, calculating a distance from each phase difference, and detecting a position. Patent Document 3 discloses a technique for synchronizing the clock of the transmission device and the clock of the reception device, which are radio wave sources, in order to accurately calculate the arrival time difference or the phase difference.

  In these methods, the distance is calculated when a specific signal included in a radio wave transmitted from a radio wave source is received or from a phase difference between specific signals included in each of a plurality of received radio waves.

As a specific signal, a reference signal called a pilot signal is used in an OFDM (Orthogonal Frequency Division Multiplexing) system used in, for example, digital terrestrial television and wireless LAN (802.11a). . The pilot signal is a signal included for reference at the time of reading information from the signal. The receiving device stores the same signal as the transmitted pilot signal, identifies the time when the pilot signal is received from the time when the correlation becomes maximum based on the correlation output with the received signal, and uses the identified time as a reference. Information is extracted by detecting a symbol delimiter included in the signal and demodulating the signal.
Japanese Patent No. 3739078 Japanese Patent No. 33839797 Japanese Patent No. 3961951

  The emitted radio wave includes noise due to various causes. Since the radio wave that has arrived directly and the radio wave that arrives after being delayed by reflection are superimposed and received (referred to as multipath), the time corresponding to the maximum of the correlation shifts backward or the correlation curve becomes dull. As a result, detection of symbol delimiters may be shifted. However, in the original communication application in the OFDM system, measures are taken so that the signal can be sufficiently demodulated if the symbol delimiters detected under the influence of multipath are slightly shifted.

  However, when the reception time point at which a specific signal is received is used for position detection, it is necessary to obtain the reception time point with higher accuracy. For example, when the correlation between the received signal and a specific signal is maximized due to the influence of multipath and the reception time is specified incorrectly by 50 nanoseconds, there is no problem in many current communication applications. However, in a position detection application, an error of 50 nanoseconds corresponds to an error of 15 meters, and accuracy may be insufficient.

  The present invention has been made in view of such circumstances, and a receiving device capable of specifying a signal reception time point with higher accuracy, a ranging system and a positioning system using the receiving device, and a computer including the receiving device. It is an object of the present invention to provide a computer program that functions as a receiver, and a reception time specifying method.

  A receiving apparatus according to a first aspect of the present invention is a receiving apparatus that stores a copy of a reference signal included in a signal to be transmitted and identifies a reception time point when the signal is received, and is superimposed on the received signal. Analyzing means for analyzing the delayed signal, creating means for creating a correction reference signal for correcting the copy based on the delayed signal analyzed by the analyzing means, received signal and correction reference created by the creating means And a means for specifying the reception time of the signal based on the correlation with the signal.

  In the receiving apparatus according to the second aspect of the invention, the analyzing means includes: a means for estimating a backward delay signal having a delay time longer than a reference time related to a bandwidth of the received signal, among the delayed signals; A removing means for removing a backward delay signal, and means for analyzing a delayed signal having a delay time shorter than the reference time from the signal after the removing means removes the backward delay signal.

  According to a third aspect of the present invention, there is provided a receiving apparatus comprising: a first calculating unit that obtains a first calculation signal by a predetermined calculation using a real part and an imaginary part of a received signal; and a real part and an imaginary part of the correction reference signal. And a second calculation means for obtaining a second calculation signal by a predetermined calculation used, and a means for specifying a reception time point of the signal based on a correlation between the first calculation signal and the second calculation signal. .

  According to a fourth aspect of the present invention, in the receiving device, the analyzing means obtains an impulse response by obtaining a transfer function from the received signal, and the obtained impulse response is a linear sum of two or more predetermined functions having time as a variable. And a means for specifying the predetermined function using a least square method, and based on the specified predetermined function, the delay time and the intensity ratio of the delayed signal with respect to the earliest received signal are estimated. It is characterized by that.

  The receiver according to a fifth aspect is characterized in that the predetermined function is a sinc function.

  According to a sixth aspect of the present invention, there is provided a receiving apparatus comprising means for extracting a signal in a range including the reference signal from the received signal.

  The receiving apparatus according to a seventh aspect is characterized in that the extraction means extracts at least two ranges of signals having different time ranges from the received signal.

  A ranging system according to an eighth aspect of the present invention includes a transmission device that transmits a signal including a reference signal and information on a transmission time point, and a reception device according to any one of the first to seventh aspects, wherein the reception device is The distance between the transmission device and the reception device is measured from the time difference between the transmission time point included in the signal received from the transmission device and the reception time point specified by the reception device.

  A positioning system according to a ninth aspect of the present invention comprises a transmission device that transmits a signal including a reference signal and information about a transmission time point, and the reception device according to any one of the first to seventh aspects of the invention, and the transmission device or the reception device. A positioning system for measuring the position of the device, wherein at least one of the transmission device or the reception device is provided in a plurality, and means for storing position information of any of the transmission device or the reception device, Based on the transmission time point included in the signal transmitted from the transmission device, the distance measurement means for measuring the distance from the time difference between the reception time points specified by the reception device, the position information and the distance measured by the distance measurement device, And means for measuring the position of a device whose position information is unknown in the transmitting device or the receiving device.

  A computer program according to a tenth aspect of the invention is a computer program for storing a copy of a reference signal included in the signal in a computer that receives a signal to be transmitted, and for specifying a reception time point when the signal is received. Analyzing means for analyzing a delay signal superimposed on the received signal; generating means for generating a correction reference signal for correcting the copy based on the delay signal analyzed by the analyzing means; and It is characterized by functioning as means for specifying the reception time of the signal based on the correlation between the signal and the correction reference signal created by the creation means.

  A reception time specifying method according to an eleventh invention is a reception time specifying method for storing a copy of a reference signal included in a signal to be transmitted and specifying the reception time when the signal is received. Analyzing the delayed signal superimposed on the signal, creating a corrected reference signal with the duplicate corrected based on the analyzed delayed signal, and receiving the signal based on the correlation between the received signal and the created corrected reference signal It is characterized by specifying a time point.

  In the first invention, the tenth invention and the eleventh invention, a delay signal that arrives late is analyzed, and the reference signal stored in advance is corrected based on the analyzed delay signal, thereby being included in the delay signal. A corrected reference signal for reproducing the reference signal when the reference signal to be superimposed is superimposed is created. Correlation between the received signal and the corrected reference signal that reproduces the superposition of the delayed signal, so that the signal on which the delayed signal is superimposed and the replica equal to the reference signal when ideally received are correlated Rather, the correlation can be obtained with higher accuracy.

  In the second aspect of the invention, the delay signal received with a delay longer than the reference time is removed in advance, and then the other delay signal is analyzed. The reference time is the time related to the bandwidth of the signal, and even when a signal whose delay time is longer than the reference time is removed from the original received signal, it can be determined that there is little influence when analyzing the original signal. It is. When the intensity of a signal having a long delay time is high, the analysis is performed after the signal is removed, thereby improving the accuracy of analysis processing of other delay signals. When many delay signals are included, it may be difficult to accurately estimate all the delay signals at once, but the accuracy is improved by performing analysis with fewer delay signals included.

  In the third aspect of the invention, the component of the imaginary part corresponding to the 90 ° phase lag of the transmitted signal is reflected, and the calculation of the pseudo-high frequency signal is utilized, in particular, the signal received earliest. The influence of the delayed signal received in the vicinity becomes obvious. As a result, it is possible to evaluate the degree of influence of the delayed signal having a relatively short delay time. That is, since the accuracy of analysis of a delayed signal that is difficult to separate and has a short delay time is improved, the accuracy of specifying the reception time can be increased by performing correction according to the evaluated degree.

  In the fourth aspect of the invention, the delay signal can be analyzed with higher accuracy by the analysis using the least squares method, and the correlation can be obtained with higher accuracy, so that the identification accuracy at the reception time is improved.

  In the fifth aspect of the invention, the impulse response obtained from the received signal is handled as a linear sum of sinc functions, so that the delayed signal can be analyzed with high accuracy.

  In the sixth aspect of the invention, the amount of calculation can be reduced by limiting the analysis target to a range including the reference signal included in the received signal.

  In the seventh invention, the possibility of extracting a range including the reference signal that can be analyzed with high accuracy is increased, and the calculation amount can be reduced and the accuracy of the analysis can be increased.

  In the eighth invention and the ninth invention, it is possible to accurately obtain the correlation with the received signal by correctly reflecting the influence of the delayed signal, so that the identification accuracy at the time of reception is increased. Therefore, when the distance is measured using the time difference between the transmission time and the reception time, and the position is measured using the measured distance, the measurement accuracy is increased.

  In the case of the present invention, a correction reference signal that reproduces a reference signal actually received by correcting a copy of the reference signal by taking into account the influence on the correlation caused by the reference signal included in the signal received with a delay is created. Then, since the correlation with the received signal is taken, the reception time of the signal can be specified with higher accuracy. Since the reception time point can be specified with high accuracy, the distance and further the position can be measured with higher accuracy.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a receiving apparatus in the first embodiment. The receiving device 1 is configured to receive OFDM radio waves, and includes a receiving unit 10, a storage unit 11, an FFT processing unit 12, a first matched filter 13, a delay signal estimation unit 14, and a reproduction signal creation unit 15. , A second matched filter 16, a reception time specifying unit 17 and a time measuring unit 18.

  The receiving unit 10 receives radio waves in a predetermined frequency band and outputs a signal. The receiving unit 10 performs analog / digital conversion on the signal output from the antenna unit 101 that has received the radio wave by the receiving circuit 102 including an amplifier circuit, a filter circuit, and the like, and performs the subsequent FFT processing unit 12, the first matched unit, and the like. Output to the filter 13 and the second matched filter 16.

  The storage unit 11 is a ROM such as a mask ROM. In the storage unit 11, a replica of the pilot signal (hereinafter referred to as a replica signal R (t)) is used in order to obtain a pattern match, that is, a correlation for identifying the time point at which the pilot signal P (t) included in the received signal is inserted Is called).

  The first matched filter 13 and the second matched filter 16 take the correlation between the input signals and output them. The first matched filter 13 obtains a correlation on the time axis between the received signal Sr (t) input from the receiving unit 10 and the replica signal R (t) stored in the storage unit 11, and performs an FFT processing unit 12. Output to. The second matched filter 16 correlates the received signal Sr (t) input from the receiving unit 10 and the adjusted replica signal R ′ (t) input from the reproduction signal generating unit 15 to specify the reception time point. To the unit 17.

The FFT processing unit 12 performs FFT (Fast Fourier Transform) processing on the input signal, and outputs the frequency distribution of the input signal to the delayed signal estimation unit 14 at the subsequent stage. The range in which the FFT processing unit 12 performs the FFT processing (hereinafter referred to as the FFT window) is in the vicinity of the time T _c1 when the correlation output from the first matched filter 13 is maximized, and the time width of the replica signal a range having the same width or the time width T _R or wider and T _R. As a result, it is possible to extract a signal in a range in which the pilot signal P (t) will be included, and perform FFT processing. More specifically, the FFT windows are two FFT windows centered at time points that are appropriately shifted forward and backward from the time point T _c1 at which the correlation output from the first matched filter 13 is maximized. The FFT processing is preferably performed in each range. As a result, there is a high possibility that the entire pilot signal P (t) is included in the range in which the FFT processing is performed, and the time point at which the correlation is maximized can be specified with high accuracy, thereby improving the accuracy of the subsequent analysis. it can.

The delay signal estimation unit 14 obtains a transfer function of the transmission path from a range including the pilot signal P (t) in the reception signal Sr (t) received by the reception device 1, and is superimposed on the reception signal Sr (t). The characteristic of the delayed signal, that is, the delay profile is estimated. The delay signal estimation unit 14 estimates the intensity ratio r and the delay time t _delay with respect to the shortest signal reached through the shortest path as a delay profile, and outputs the estimation result to the reproduction signal creation unit 15. Specifically, the delay signal estimation unit 14 first obtains a transfer function from the frequency distribution output from the FFT processing unit 12 and the frequency distribution of the replica signal R (t) that is a replica of the pilot signal P (t). . The transfer function G (s) is obtained by G (s) = Sr (s) / R (s). At this time, s is a Laplace variable, Sr (s) is a frequency component of the received signal Sr (t), and R (s) is a frequency component of the replica signal R (t). The delay signal estimation unit 14 performs an inverse FFT process on the transfer function G (s) to obtain an impulse response.

The delayed signal estimation unit 14 treats the impulse response as a linear combination of the impulse response when only the shortest signal is present and the impulse response when only the delayed signal is present. The linear coefficient (intensity ratio) r and the delay time t _delay from the shortest signal are estimated and output to the reproduction signal creation unit 15. It has been found that the impulse response obtained by performing FFT processing with a rectangular FFT window from only the shortest signal or the delayed signal is a sinc function (sin (x) / x). Therefore, the delay signal estimation unit 14 treats the obtained impulse response as a linear combination of sinc functions, and analyzes the intensity ratio and delay time of the delay signal. Further, when a plurality of delayed signals are estimated, the delayed signal estimating unit 14 estimates and outputs the respective linear coefficients r _i and t _{delay i} (i = 1, 2, 3,...).

Based on the intensity ratio r _i output from the delay signal estimation unit 14 and the delay time t _{delay i} , the reproduction signal creation unit 15 affects the pilot signal P (t−t _delay ) included in the superimposed delay signal. A reproduction signal (corrected pilot signal) R ′ (t) obtained by correcting the replica signal R so as to reproduce the signal is generated and output to the second matched filter 16. Specifically, the reproduction signal R ′ (t) is created as R ′ (t) = R (t) + Σ {r _i * R (t−t _{delay i} )}.

The reception time point specifying unit 17 specifies the time point T _c2 at which the correlation output from the second matched filter 16 is maximized with reference to the time (clock count) obtained from the time measuring unit 18 that measures time in a predetermined cycle. To do.

  In FIG. 1 and the description thereof, the FFT processing unit 12, the delay signal estimation unit 14, and the reproduction signal creation unit 15 have been described as a configuration that performs processing. However, these components are described as being functionally distinguished for the sake of clarity, and components that realize each function by a series of processes may be provided. The same applies to the other components.

  Next, processing for specifying a reception time point by the operation of each component configured as described above will be described with reference to a flowchart. FIG. 2 is a flowchart illustrating an example of a processing procedure in which a reception time point is specified by the reception device 1 according to the first embodiment.

The first matched filter 13 takes a correlation between the received signal Sr (t) and the replica signal R (t) read from the storage unit 11 on the time axis (step S11). Since the correlation output from the first matched filter 13 is input to the FFT processing unit 12, the FFT processing unit 12 is a rectangle including a point in time when the correlation output from the first matched filter 13 is maximized and its vicinity. A signal Sr _ex (t) to be processed is extracted from the received signal Sr (t) by a window (FFT window) (step S12). The FFT processing unit 12 performs FFT processing on the extracted received signal Sr _ex (t) and converts it to a frequency component (step S13).

The delay signal estimation unit 14 obtains the transfer function G (s) by dividing the received signal Sr _ex (t) converted into the frequency component by the frequency component of the replica signal R (t), and the obtained transfer function G An impulse response is obtained by performing inverse FFT processing on (s) (step S14). Based on the obtained impulse response, the delayed signal estimation unit 14 treats the impulse response as a linear combination of sinc functions, and estimates a delayed signal by analysis (step S15).

  The reproduction signal creation unit 15 creates the reproduction signal R ′ (t) based on the intensity ratio and delay time of the delay signal estimated by the delay signal estimation unit 14 and the replica signal R (t) (step S16). The second matched filter 16 receives the received signal Sr (t) and the reproduction signal R ′ (t) created by the reproduction signal creation unit 15. The second matched filter 16 takes these correlations and outputs them (step S17).

The reception time specifying unit 17 specifies the time T _c2 at which the correlation output from the second matched filter 16 is maximized with reference to the time acquired from the time measuring unit 18 (step S18). Thus, the reception time specifying process in the receiving device 1 is completed.

  Next, each processing procedure described in the flowchart of FIG. 2 will be described in detail with a specific example. FIG. 3 is an explanatory diagram illustrating a content example of the replica signal R (t) and the received signal Sr (t) stored in the storage unit 11 of the receiving device 1 according to the first embodiment. In the explanatory diagram of FIG. 3, the passage of time is shown from the left to the right, and the replica signal R (t), the reception signal Sr (t), and the correlation signal Cor (t) are shown from the top, and the reception signal Sr (t). The FFT window for is shown by a broken line.

  The reception signal Sr (t) includes a pilot signal P (t) at a predetermined period. Therefore, by taking a correlation with the replica signal R (t) which is a replica of the pilot signal P (t), the correlation should be maximized when the pilot signal P (t) is included. However, the received signal Sr (t) is also superimposed with a delayed signal received with a delay due to the influence of multipath. Even in the example of the explanatory diagram of FIG. 3, it is difficult to find a waveform that approximates the received signal Sr (t) and the replica signal R (t). When the correlation between the received signal Sr (t) and the replica signal R (t) is taken, the maximum is originally in the vicinity of the time when the pilot signal P (t) is included, but the time at which the maximum is shifted is shifted backward. Or, if the correlation curve has a dullness and the reception time is the time when the correlation is maximized, there is a possibility that the error will increase.

The pilot signal P (t−t _delay ) received with a _delay is superimposed on the pilot signal P (t) received in the shortest time in the range including the pilot signal P (t) in the received signal Sr (t). I guess it is. Therefore, by obtaining a transfer function based on the received signal Sr (t) and the replica signal R (t) and analyzing the impulse response further obtained from the obtained transfer function, a delay signal for the signal received in the shortest time is obtained. Intensity ratio and delay time of the

In order to obtain the impulse response, first, an FFT process is performed on the received signal Sr (t) to obtain a transfer function. To obtain a transfer function with higher accuracy, the FFT is applied to a range including the entire pilot signal P (t). It is desirable to perform processing. However, since it is difficult to correctly specify the range corresponding to the pilot signal P (t) by the superposition of the delay signal, the target range to be subjected to the FFT processing is the correlation between the received signal Sr (t) and the replica signal R (t). The range included in the time width T (≧ T _R ) with the reception time point T _c1 approximately specified by can be roughly specified as the target range, that is, the FFT window. Note that the reception time T _c1 specified from the local maximum of the correlation between the actually received reception signal Sr (t) and the replica signal R (t) may already contain a large error. Since the difference in reception time between the pilot signal P (t) received in the shortest time and the pilot signal P (t−t _delay ) received late is obtained, the intensity of the impulse response for any signal is high. It is necessary to be able to fully identify the point of maximum. Therefore, as the FFT window, as shown in the lower part of FIG. 3, two rectangular FFT windows shifted by an arbitrary time before and after T _c1 are used. Then, from the transfer function obtained from each of the received signals Sr _ex (t) extracted using the two FFT windows, the time point at which the intensity is satisfactorily maximized among the two further obtained impulse response spectra. It is possible to determine the intensity ratio and delay time of the delayed signal with higher accuracy.

FIG. 4 is a graph illustrating an example of an impulse response obtained from the received signal Sr (t) by the receiving device 1 according to the first embodiment. The solid line in FIG. 4A is an impulse response obtained through FFT processing and transfer function calculation on the received signal Sr _ex (t) extracted from the received signal Sr (t) in the FFT window shown in FIG. is there. In the graph of FIG. 4A, the horizontal axis indicates time, and the vertical axis indicates intensity. The time axis indicates the time when the starting point of the FFT window is zero. For comparison, FIG. 4B shows a curve of a sinc function corresponding to an impulse response obtained from a single-wave signal not including a delay signal.

When compared with the waveform of the sinc function shown in FIG. 4B, the impulse response shown in FIG. 4A is gentle in the second half of the curve near the maximum point where the absolute value is maximum, and further, the gentle curve. A local maximum appears in the middle of The delay signal estimation unit 14 analyzes the impulse response shown in FIG. 4A as a linear combination of the sinc functions, and estimates the intensity ratio and delay time of the delay signal. The impulse response shown in FIG. 4A is analyzed as, for example, a linear combination of four sinc functions indicated by broken lines. The sinc function with the earliest point in time at which the intensity of the four sinc functions becomes maximum should be the impulse response of the shortest signal. Therefore, it is possible to estimate the other three sinc functions as the impulse response of the delayed signal. The time differences from the time when the intensity of the sinc function estimated as the impulse response of the shortest signal is maximized to the time when the intensity of the other three sinc functions are maximized are 38 nanoseconds, 76 nanoseconds and 120 nanoseconds, respectively. Furthermore, when the signal received with the shortest signal strength is set to 1, when it can be analyzed as 1.33, 0.84, and 0.64, respectively, the reproduction signal from the delayed signal estimation unit 14 R ₁ = 1.33, t _{delay 1} = 38, r ₂ = 0.84, t _{delay 2} = 76, r ₃ = 0.64, t _{delay 3} = 120 are output to the creation unit 15.

  FIG. 5 is an explanatory diagram illustrating an example of the correlation between the reproduction signal R ′ (t) created based on the replica signal R (t) by the reception device 1 according to Embodiment 1 and the reception signal Sr (t). is there. In the explanatory diagram of FIG. 5, the passage of time is shown from the left to the right, and the reproduction signal R ′ (t), the reception signal Sr (t), and the correlation signal Cor ′ (t) are shown from the top. Further, for comparison with the curve of the correlation signal Cor ′ (t), the correlation signal Cor (t) when the correlation between the replica signal R (t) and the reception signal Sr (t) is simply obtained (see FIG. 3). Is indicated by a broken line.

In the example illustrated in FIG. 5, for example, the reproduction signal R ′ (t) is generated by the reproduction signal creation unit 15 based on the intensity ratio r _i of each delay signal input from the delay signal estimation unit 14 and the delay time t _{delay i.} It is created as shown in Equation 1.

  Reproduction signal R ′ (t) = R (t) + 1.33 * R (t−38) + 0.84 * R (t−76) + 0.64 * R (t−120) (1)

The generated reproduction signal R ′ (t) is input to the second matched filter 16, and the second matched filter 16 correlates with the received signal Sr (t) on the time axis. Thereby, the time point T _c2 at which the obtained correlation becomes maximum is specified as the reception time point. In this case, the reproduction signal R ′ (t) is created so as to reproduce the superimposition with the pilot signal P (t−t _delay ) included in the three delay signals, so that the received signal Sr (t) actually received is reproduced. The waveform is close to the signal included in (). Therefore, the reception time point T _c2 specified by taking a correlation with the reproduction signal R ′ (t) is more accurate than the reception time point T _c1 specified simply from the maximum point of the correlation with the replica signal R (t). is there. When the reception signal Sr (t) includes a delay signal due to the influence of multipath, the reception time T _c1 specified from the time when the correlation with the replica signal R (t) is maximized is not affected by the delay. Received and delayed from the exact reception time. In this case, the reception time point T _c2 specified from the time point when the correlation with the reproduction signal R ′ (t) becomes maximum is an earlier time point than the reception time point T _c1 .

As shown in the content examples shown in FIGS. 3 to 5, when the sinc function constituting the impulse response can be estimated with high accuracy, it is specified by simply correlating with the replica signal R (t). The error of the received reception time T _c1 with respect to the original reception time is about 30 nanoseconds, but the error can be suppressed to 1 nanosecond. One nanosecond corresponds to 0.3 meters in distance. Thus, the correlation between the received signal Sr (t) on which the delayed signal is superimposed and the reproduced signal R ′ (t) created based on the replica signal R (t) so as to reproduce the superimposed superimposed delay signal is obtained. Thus, the reception time point T _c2 can be specified with high accuracy.

(Embodiment 2)
In the example shown in the first embodiment, it is possible to accurately specify the reception time point by suppressing the error to 1 nanosecond, but this is possible when the impulse response can be analyzed accurately. However, usually, in an environment where there are many reflections of radio waves, there are more delay signals and they are close to each other and complex, and the intensity and delay time are various. When a large number of delayed signals are received over a long time, it is necessary to consider that the impulse response obtained from the received signal is composed of the sum of a large number of sinc functions. However, in this case, it may be difficult to accurately estimate each of a plurality of sinc functions constituting the impulse response. For example, compared with the case of analyzing as a linear sum of three sinc functions, the degree of difficulty increases in the case of analyzing as a linear sum of four sinc functions, and the possibility of finding a solution as a linear sum is reduced.

  Therefore, in the second embodiment, an impulse of a backward delay signal having a delay time longer than a reference time related to a bandwidth in order to specify a reception time point with high accuracy even for a signal received in an environment where the influence of multipath is large. The analysis is performed after removing the response. Further, the impulse response after removal is analyzed by the least square method. This makes it possible to estimate the delay signal with higher accuracy and specify the reception time point.

  The configuration of receiving apparatus 1 in the second embodiment is the same as the configuration in the first embodiment except for the detailed processing contents in delay signal estimating section 14. Therefore, the same reference numerals as those in the first embodiment are given, and detailed description of each component is omitted. Hereinafter, processing in which the delay signal estimation unit 14 estimates other delay signals by removing the impulse response of the backward delay signal whose delay time is longer than the reference time from the obtained impulse response will be described.

  FIG. 6 is a flowchart illustrating an example of a processing procedure in which the reception time point is specified by the reception device 1 according to the second embodiment. Among the processing procedures shown in the flowchart of FIG. 6, the steps common to the processing procedure shown in the flowchart of FIG. 2 in the first embodiment are denoted by the same step numbers and detailed description thereof is omitted.

  The delay signal estimation unit 14 of the reception device 1 estimates a backward delay signal having a delay time longer than the reference time based on the impulse response obtained in step S14 (step S21). Then, the delay signal estimation unit 14 removes the estimated impulse response of the backward delay signal by subtracting it from the impulse response obtained in step S14 (step S22), analyzes the impulse response after the removal by the least square method, and so on. Is delayed (step S23).

  In this way, among the delay signals included in the impulse response, backward delay signals that do not have a large effect when the reception time point is finally identified can be removed, and the number of delay signals to be analyzed can be reduced. . As a result, even when a large number of delay signals are included, analysis can be performed with high accuracy. The effect will be described by applying the following specific example.

  FIG. 7 is an explanatory diagram illustrating an example in which a received signal is simulated when an OFDM signal is received via a transmission path that models an actual radio wave environment in an urban area. FIG. 7A is an explanatory diagram showing a modeled transmission path. In FIG. 7B, the horizontal axis indicates time, the vertical axis indicates signal strength, and a delay profile representing the arrival time and strength time distribution of the received signal obtained by simulation is shown.

  As shown in the explanatory diagram of FIG. 7A, the simulation is performed assuming the reception of an OFDM signal transmitted at an intersection of a road on which a vehicle passes. It is assumed that the radio wave source RS is at an intersection and there is a reception point RP where the receiving device 1 is located on a straight line from the radio wave source RS along the roadway. However, it is assumed that the reception point RP is shielded from the radio wave source RS by a large metal truck and is surrounded by a plurality of large metal trucks.

  In this case, as shown in the delay profile of FIG. 7B, there are a large number of delayed signals received late in the actual transmission path, and the delay times are also various. In the example of the delay profile shown in FIG. 7B, the intensity of the delayed signal tends to be stronger than the shortest signal reaching the receiving apparatus 1 at the shortest indicated by S1 in the figure.

  An example in which the reception time point is specified by the receiving device 1 when an OFDM signal having a bandwidth of 7.8125 MHz is transmitted from the radio wave source RS via a transmission line having a delay profile as shown in FIG. explain.

  FIG. 8 is a graph showing the correlation between the received signal Sr (t) obtained by the receiving apparatus 1 and the replica signal R (t) in the example in the second embodiment. The solid line in the graph of FIG. 8 shows the correlation between the received signal Sr (t) including the delayed signal and the replica signal R (t), and the broken line shows the received signal and the replica signal R (t (t) when only the shortest signal is received. ) And the correlation obtained.

As in the delay profile shown in the explanatory diagram of FIG. 7B, a large number of delay signals are superimposed on the reception signal Sr (t). As shown in FIG. 8, the correlation obtained in this case is not a plurality of local maximum points but a curve having substantially one local maximum point even in a range where a plurality of delayed signals are superimposed. Note that the curve in the vicinity of the correlation maximum point shown in the graph of FIG. 8 is duller than the curve in the vicinity of the correlation maximum point obtained when only the shortest signal is received, and is shifted backward. When the time T _{c1 at} which the correlation of the correlation curve becomes maximum is the reception time point, the correlation curve as a whole is strongly influenced by the delayed signal having a stronger intensity than the shortest signal. The error is about 50 nanoseconds with respect to the reception time of the shortest signal, which is calculated from the distance from to the reception point RP. Note that 50 nanoseconds corresponds to a distance of 15 meters.

  FIG. 9 is a graph illustrating an example of an impulse response obtained by the receiving device 1 in the example of the second embodiment. FIG. 9A shows an example of an impulse response, and FIG. 9B shows an ideal impulse response for comparison, that is, an impulse response of only the shortest signal. Moreover, the horizontal axis of Fig.9 (a) and FIG.9 (b) shows time, and a vertical axis | shaft shows intensity | strength. In the example of the impulse response shown in FIG. 9, it can be seen that the rear is duller than the impulse response of only the shortest signal and is affected by the delay signal.

Then, the delay signal estimation unit 14 performs a process of removing the impulse response of the backward delay signal from the impulse response illustrated in FIG. Here, the backward delay signal refers to a delay signal having a delay time longer than a reference time based on the bandwidth of the OFDM signal. The reference time is a time obtained by dividing the reciprocal T of the bandwidth f _band by 2. The reciprocal of the bandwidth f _band corresponds to the time difference between the intersections between the curve near the maximum point where the absolute value of the intensity of the impulse response of only the shortest signal shown in FIG. . When the intensity of the impulse response of the backward delay signal delayed later than the time corresponding to half the time difference of the intersection with the intensity = 0 horizontal line becomes the maximum, the intensity of the impulse response of the shortest signal becomes the maximum. Well separated from the time. Therefore, when analyzing the impulse response as a linear sum of the sinc functions, the accuracy of the strength and delay time estimated by the analysis of the backward delay signal is finally determined when the reception time point specifying unit 17 specifies the reception time point. The knowledge that it does not have a big influence is obtained. The reference time is not limited to the time obtained by dividing the reciprocal T of the bandwidth f _band by 2. The reference time is defined as a time that can be determined as a signal received with a delay sufficiently long that the specific accuracy at the time of reception is not affected. In the example in the second embodiment, since an OFDM signal having a bandwidth of 7.8125 MHz is transmitted, the reference time is specifically set to 64 nanoseconds (= 1 / 7.8125 MHz / 2).

  FIG. 10 is an explanatory diagram illustrating an example in which the impulse response of the backward delay signal is removed from the impulse response in the example in the second embodiment. The graphs shown in FIG. 10A to FIG. 10D are spectra based on impulse responses, the horizontal axis indicates time, and the vertical axis indicates intensity.

A curve A in FIG. 10A shows an impulse response obtained from the extracted received signal Sr _ex (t). A curve B represented by a broken line is an ideal impulse response centered at a time point t _{B at} which the intensity of the impulse response obtained from the signal Sr _ex (t) extracted from the received signal Sr (t) is maximized. . Curve C in FIG. 10 (b), from the impulse response obtained from FIG. 10 reception signal Sr _ex in (a) (t) (curve A), the ideal centered on time t _B the strength is maximum The impulse response (curve B) is subtracted. The time point corresponding to the rear maximum point of the two maximum points shown in FIG. 10B is the reference time from the time t _B when the intensity of the ideal impulse response shown in FIG. It can be estimated that the maximum point corresponds to the maximum point of the impulse response of the backward delay signal. Therefore, a sinc function curve centered on a time point corresponding to the rear maximum point shown in the curve D of FIG. 10B is estimated as the impulse response of the backward delay signal, and the impulse response is removed.

FIG. 10C shows the backward delay indicated by the curve D in FIG. 10B obtained by estimation from the impulse response of the extracted received signal Sr _ex (t) indicated by the curve A in FIG. The spectrum after removing the impulse response of the signal is shown. A curve E in FIG. 10C approximates an ideal impulse response curve shown in a curve B in FIG. Here, the impulse response (curve A) of the received signal is the impulse of the backward delay signal estimated from the ideal impulse response shown by the curve B in FIG. 10A and the rear maximum point in FIG. 10B. When analyzing that it is a linear combination with the response (curve D), the ideal impulse response is the impulse response of the shortest signal. In this case, since the maximum value of the curve D in FIG. 10B when the maximum value of the curve B in FIG. 10A is 1 is 0.4, the intensity ratio r of the backward delay signal is r = 0.4 can be read. Further, since the time point corresponding to the local maximum value of the curve D in FIG. 10B is delayed by 75 nanoseconds from the time point t _B corresponding to the local maximum value of the curve _B in FIG. It can be read that the delay time t _delay = 75 nanoseconds of the backward delay signal. When the intensity ratio r and the delay time t _delay are input to the reproduction signal generator 15, the generated reproduction signal R ′ (t) is R ′ (t) = R (t) + 0.4 * R (t −75). When the reproduction signal R ′ (t) thus created is input to the second matched filter 16 and correlated with the reception signal Sr (t), the reception time specifying unit 17 receives the time T _c2. Identified as a point in time. In this case, the time T _c2 has an error of 39 nanoseconds compared to the original reception time, and the accuracy is higher than the error of 50 nanoseconds when the correlation is taken without considering the influence of the backward delay signal. Is shown. Note that 39 nanoseconds corresponds to 11.7 meters in distance.

  Note that the spectrum shown by the curve E in FIG. 10C is not only the impulse response of the shortest signal but also the linear combination with the impulse response of the delayed signal received with a relatively short delay time immediately after the shortest signal. there is a possibility. Therefore, the spectrum shown by the curve E in FIG. 10C is further analyzed using the least square method as a linear combination of the impulse responses of the shortest signal and the delayed signal.

  When the spectrum shown by the curve E in FIG. 10C is a linear combination of the impulse response of the shortest signal and the impulse response of the delayed signal, it is expressed by the following equation 2.

By the processing of the delay signal estimation unit 14, the linear coefficients a and b and the delay times t _a and t _b in Equation 3 are estimated using the least square method. By performing after removing the impulse response of the backward delay signal, a more accurate estimated value can be obtained compared to the case where each sinc function is analyzed at once using the least squares method as a linear sum of three sinc functions. It can be obtained.

  The case where the spectrum shown by the curve E in FIG. 10C in the example in the second embodiment is analyzed by the least square method will be described below. Note that the spectrum shown by the curve E in FIG. 10C is the reproduction signal R ′ (t) = R (t) + 0.4 * R (t−75) created from the analysis of the backward delay signal described above. It corresponds to the portion of R (t) which is the first term. Here, when the spectrum shown by the curve E in FIG. 10C is Re (t) and the curve E is further composed of a linear sum of two sinc functions, the analysis is performed by the least square method, as shown in the following Expression 3. I want to.

That is, the spectrum indicated by the curve E in FIG. 10C is obtained as a linear combination of the curves F and G in FIG. When the maximum value of the curve B in FIG. 10A is 1, the maximum value of the curve F is 0.60, and the maximum value of the curve G is 0.73. Therefore, the intensity ratios of the other delayed signals can be read as r = 0.60 and r = 0.73, respectively. In addition, the time point corresponding to the maximum value of the curve F in FIG. 10D is 29 nanoseconds earlier than the time point _B corresponding to the maximum value of the curve _B in FIG. The time corresponding to the local maximum is 20 nanoseconds behind t _B. Therefore, the delay times of the other delay signals can be read as t _delay = −29 nanoseconds and t _delay = 20 nanoseconds, respectively.

  When combined with the impulse response (sinc function) obtained only from the backward delay signal, the spectrum Ra (t) of the impulse response (curve A in FIG. 10A) of the received signal Sr (t) is expressed by the following Equation 4. I want to.

  As a result, the reproduction signal R ′ (t) becomes the reproduction signal R ′ (t) = 0.60 * R (t−29) + 0.73 * R (t−20) + 0.40 * R (t−75). And created. In this way, the reception time point is specified by correlating with the reproduction signal R ′ (t) that reproduces the delay profile of the reception signal Sr (t) that is closer to reality. In this case, the specified reception time point has an error of 9 nanoseconds with respect to the original reception time point, and the accuracy can be improved.

The time _Tc2 is determined based on the time _Tc2 specified by correlation with the reproduction signal R ′ (t) = R (t) + 0.4 * R (t−75) reflecting the influence of only the backward delay signal. _Since it can be estimated by analysis that there will be a signal received at a time point 29 nanoseconds earlier than _c2 , the reception time point may be specified by a correction that _advances time _Tc2 by 29 nanoseconds. The time T _c2 is a time when the error is delayed by 39 nanoseconds from the original reception time due to the influence of the delay signal. However, the error at the specified reception time is 10 nanoseconds due to the correction advanced by 29 nanoseconds. Become.

  As described above, even under the severe transmission path conditions as the OFDM signal reception environment shown in FIG. 7A, it is possible to specify a highly accurate reception time point of about 2.7 meters in 9 nanoseconds, that is, a distance. There is an excellent effect.

(Embodiment 3)
In the second embodiment, the impulse response obtained by removing the backward delay signal whose delay time is longer than the reference time is reanalyzed, and the intensity ratio and delay time of the delay signal having a relatively short delay time are estimated. The specific accuracy could be further increased. On the other hand, in the third embodiment, the reproduction signal R ′ (t) reproduced in consideration of the intensity ratio of the delay signal with a relatively long delay time to the shortest signal and the delay time, and the reception signal Sr (t), respectively. On the other hand, an example in which the reception time point is specified with high accuracy by a configuration that performs a predetermined calculation that makes the influence on the impulse response due to the delay signal having a short delay time apparent will be described.

  FIG. 11 is a block diagram showing a configuration of receiving apparatus 1 in the third embodiment. The configuration of the receiving device 1 in the third embodiment includes a configuration in which the first calculation unit 191 and the second calculation unit 192 are provided in the preceding stage of the second matched filter 16, and details of the reception time point specifying process by the reception time point specifying unit 17 Except for this, the configuration is the same as in the first embodiment. The components common to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Hereinafter, calculation processing performed by the first calculation unit 191 and the second calculation unit 192 on the generated reproduction signal R ′ (t) and the reception signal Sr (t) will be described.

  The first calculation unit 191 and the second calculation unit 192 perform predetermined calculation processing on the input signal and output as a calculation signal. The first calculation unit 191 is provided in the subsequent stage of the reception unit 10, and the second calculation unit 192 is provided in the subsequent stage of the reproduction signal creation unit 15. The first calculation unit 191 in the third embodiment multiplies the reception signal Sr (t) output from the reception unit 10 by the reception signal Sr (t−1) with the time shifted by 1 nanosecond to obtain the second Output to the matched filter 16. The second calculation unit 192 multiplies the reproduction signal R ′ (t) created by the reproduction signal creation unit 15 and the reproduction signal R ′ (t−1) with the time shifted by 1 nanosecond to obtain the second Output to the matched filter 16.

The calculation signals output from the first calculation unit 191 and the second calculation unit 192 are Sr (t−1) × Sr (t) and R ′ (t−1) × R ′ (t) as described above. In addition, a signal obtained by other arithmetic processing may be used. For example, when the signal input to the first calculation unit 191 and the second calculation unit 192 is generalized to be f (t) and the calculation signal is g (t), g (t) is as follows: It may be a signal obtained by simple arithmetic processing. Note that f (t) is represented by f (t) = f ₁ (t) + jf ₂ (t) (j: imaginary unit).

g (t) = f (t) × f (t) = {f ₁ (t)} ² − {f ₂ (t)} ² + j2f ₁ (t) × f ₂ (t),
g (t) = f (t−2) × f (t−1) × f (t),
g (t) = f (t−3) × f (t−2) × f (t−1) × f (t),
g (t) = f (t−64) × f (t),
g (t) = {f ₁ (t)} ⁴ − {f ₂ (t)} ⁴

  The second matched filter 16 includes a calculation signal of the reception signal Sr (t) that has been subjected to the calculation process by the first calculation unit 191 and a reproduction signal R ′ (t) that has been subjected to the calculation process by the second calculation unit 192. ) Is input. The second matched filter extracts the real part of each of the input arithmetic signals, obtains a correlation between the real parts of the arithmetic signals, and outputs the correlation to the reception time specifying part 17.

The reception time point specifying unit 17 basically specifies the time point T _c2 at which the correlation output from the second matched filter 16 is maximized with reference to the time acquired from the time measuring unit 18, but in the third embodiment, In particular, the reception time point specifying unit 17 specifies a time point at which the absolute value of the correlation is maximized among the time points when the correlation is maximum as the reception time point T _c2 . Note that, depending on the calculation processing method, that is, which g (t) is adopted, the time point T _c2 at which the absolute value of the correlation is the maximum among the time points when the correlation becomes minimum is specified as the reception time point. There is also. Then, the reception time point specifying unit 17 in Embodiment 3 specifies feature points included in the correlation curve of the correlation output from the second matched filter 16, and specifies a time difference corresponding to the feature points. A correction value T obtained by simulation is stored in advance in the time difference between the feature points in association with the storage unit 11, and the reception time point specifying unit 17 _{calculates the} correction value T from the reception time point T _c2 specified as described above. The time T _c3 obtained by subtracting is newly specified as a more accurate reception time.

  The characteristic points of the correlation curve will be described with reference to the drawings showing examples. FIG. 12 is an explanatory diagram schematically illustrating feature points included in a correlation curve between calculation signals output by the first calculation unit 191 and the second calculation unit 192 that configure the reception device 1 according to the third embodiment. . The graphs shown in FIGS. 12A, 12B, 12C, and 12D are correlation curves, the horizontal axis indicates time, and the vertical axis indicates intensity. Further, in the graphs shown in FIGS. 12A, 12B, 12C, and 12D, feature points (maximum points and minimum points) to be particularly noted are surrounded by broken lines, and the absolute value is maximum. It shows the maximal point.

  FIG. 12A shows a correlation curve when the correlation between the received signal Sr (t) and the replica signal R (t) is obtained without performing arithmetic processing. FIG. 12B shows a case where the received signal Sr (t) and the replica signal R (t) are multiplied twice, respectively, and the arithmetic processing is performed by g (t) = f (t−1) × f (t). The correlation curve which took the correlation between calculation signals is represented. In FIG. 12C, the received signal Sr (t) and the replica signal R (t) are multiplied four times respectively, and g (t) = f (t−3) × f (t−2) × f (t−1). ) × f (t) represents a correlation curve in which the correlation between the calculation signals is calculated. In FIG. 12D, the received signal Sr (t) and the replica signal R (t) are multiplied by 8 times, respectively, and g (t) = f (t−7) × f (t−6) × f (t−5). ) × f (t−4) × f (t−3) × f (t−2) × f (t−1) × f (t) It represents a correlation curve. Note that the intensity scales in the graphs of FIGS. 12A to 12D are not the same.

  As shown in the graphs from FIG. 12A to FIG. 12D, the greater the number of multiplications, the sharper the vicinity of the feature points such as the maximum point and the minimum point of the correlation curve. This is because the OFDM signal includes a sin function component and is multiplied by a plurality of multiplication operations as described above to become a pseudo high frequency signal. Note that the imaginary part included in the received signal, that is, a component having a phase delay of 90 ° is included in the real part by the calculation by multiplication, and the component of the imaginary part can be reflected in the real part when correlation is taken.

  In this way, the calculation process makes the curve near the feature point such as the maximum point and the minimum point sharp, and the identification by the analysis becomes easy. In the case where the arithmetic processing is not performed and the case where the arithmetic processing is performed, the time corresponding to the maximum point where the absolute value of the correlation is the maximum is the contents of the arithmetic processing from FIG. 12A to FIG. It does not change regardless. The receiving apparatus according to the third embodiment uses feature points that can be easily specified by arithmetic processing, and specifies a time difference corresponding to the distance between feature points. Hereinafter, a maximum point having the maximum absolute value will be described as a feature point L, a minimum point immediately before the feature point L will be described as a feature point M, and a minimum point immediately after the feature point L will be described as a feature point N. Depending on the arithmetic processing, the correlation curve obtained by correlation between the arithmetic signals may have the polarity opposite to that of the correlation curve shown in FIG. In this case, the minimum point having the maximum absolute value is set as the feature point L, the maximum point immediately before the feature point L is set as the feature point M, and the maximum point immediately after the feature point L is set as the feature point N.

  As described above, when the delay signal is superimposed on the received signal Sr (t), the vicinity of the maximum point where the absolute value of the correlation curve with the replica signal R (t) is maximum is compared with the case of only the shortest signal. And dull. At this time, the dullness of the curve in the vicinity of the maximum point where the absolute value of the correlation of the correlation curve becomes maximum changes according to the delay time of the delay signal. Then, by performing the above-described arithmetic processing on each of the received signal Sr (t) and the replica signal R (t), the change in the characteristic of the correlation curve according to the delay time of the delay signal becomes obvious, and the change can be specified. It becomes easy.

  FIG. 13 is an explanatory diagram schematically showing an example in which the correlation curve between the received signal Sr (t) and the replica signal R (t) changes under the influence of the delay signal. The graphs shown in FIGS. 13A, 13 </ b> B, 13 </ b> C, and 13 </ b> D are correlation curves, the horizontal axis indicates time, and the vertical axis indicates intensity.

  FIG. 13A shows the correlation when only the shortest signal is received. The graph on the left is an example in which the correlation is obtained without performing the arithmetic processing, and the graph on the right is four times. This is an example in the case where a correlation is obtained by performing multiplication operation. In the following, the left and right graphs are examples of the case where the arithmetic processing is not performed and the case where it is performed. FIG. 13 (b) shows the correlation when a delay signal with a delay of 20 nanoseconds is superimposed on the shortest signal, and FIG. 13 (c) shows a delay signal with a delay of 30 nanoseconds superimposed on the shortest signal. Shows the correlation of the case. FIG. 13D shows the correlation when a delay signal with a delay of 40 nanoseconds is superimposed on the shortest signal.

  In the graphs from FIG. 13 (a) to FIG. 13 (d), the curve near the maximum point where the absolute value of the correlation curve is maximum becomes gentle according to the delay time of the delay signal, and the maximum point shifts backward. It has been shown. In addition, it is shown that when the calculation process is performed, the longer the delay time, the wider between the feature points LM and LN. Therefore, by obtaining the spread between the feature points in advance for each of a plurality of different delay times, it is possible to estimate the magnitude of the deviation of the maximum point due to the delay signal from the distance between the feature points, that is, the time difference. .

  FIG. 14 is an explanatory diagram illustrating an example of the content of the correction value corresponding to the time difference corresponding to the feature points included in the correlation curve. However, the example shown in the explanatory diagram of FIG. 14 is a value obtained by simulation when an OFDM signal having a bandwidth of 15.625 MHz is transmitted.

  As shown in the explanatory diagram of FIG. 14, when an OFDM signal having a bandwidth of 15.625 MHz is transmitted, when only the shortest signal is received, the characteristic points LM of the correlation curve are 15 ns, and the LN is 15 ns. Corresponding to is obtained by simulation. Of course, the correction value is zero nanoseconds when the correlation is maximized when only the shortest signal is received because it is not affected by the delayed signal. When a delay signal with a delay of 20 nanoseconds is superimposed, the correlation curve between the characteristic points LM corresponds to 17 nanoseconds and the interval between LNs corresponds to 17 nanoseconds. The spread between the feature points when compared with the case of only the shortest signal is a time difference stretched by the delay signal, and it can be considered that the time when the correlation becomes maximum is shifted backward. Therefore, it is estimated that the shortest signal is received at a time earlier by the extended time difference from the time when the correlation becomes maximum, and the correction value is set to 4 nanoseconds (= (17 + 17) − (15 + 15)). Similarly, when a delay signal with a delay of 30 nanoseconds is superimposed, the feature points LM and LN are each 20 nanoseconds, and the correction value is 10 nanoseconds (= (20 + 20) − (15 + 15)). .

  In addition, the signal input to each of the first calculation unit 191 and the second calculation unit 192 in the third embodiment is a reproduction signal R ′ (t) that reflects the influence of the reception signal Sr (t) and the backward delay signal. . Therefore, the time difference between the feature points that appears when the correlation is obtained after arithmetic processing of each of them appears due to the influence of the delay signal that has a relatively short delay time after the backward delay signal is removed. Estimating a delayed signal with a relatively short delay time is difficult because it is difficult to separate the impulse response of the delayed signal, but the change in the time difference between feature points is considered as an effect of such a delayed signal that is difficult to estimate. This provides an excellent effect in that it can be captured and the reception time point from which the influence is removed can be specified with high accuracy.

  As shown in the explanatory diagram of FIG. 14, by storing the correspondence between the time difference corresponding to the characteristic points of the correlation curve and the correction value, the delay time is relatively simple with a simple configuration for specifying the time difference. It is possible to specify the reception time point with high accuracy without analyzing the short delay signal in detail.

  FIG. 15 is a flowchart illustrating an example of a processing procedure in which a reception time point is specified by the reception device 1 according to the third embodiment. Of the processing procedures shown in the flowchart of FIG. 15, procedures common to those shown in the flowchart of FIG. 2 in the first embodiment and the flowchart of FIG. 6 in the second embodiment are denoted by the same step numbers and detailed. Description is omitted.

  After the reproduction signal creation unit 15 creates the reproduction signal R ′ (t) based on the intensity ratio and delay time of the delay signal estimated by the delay signal estimation unit 14 and the replica signal R (t) (S16), The first calculation unit 191 and the second calculation unit 192 obtain calculation signals of the reproduction signal R ′ (t) and the reception signal Sr (t) generated by the reproduction signal generation unit 15 (step S31). Since the operation signals output from the first operation unit 191 and the second operation unit 192 are input to the second matched filter 16, the second matched filter 16 extracts each real part and extracts the time axis. The correlation between the calculation signals is taken and output (step S32).

The reception time point specifying unit 17 specifies a time point T _c2 at which the correlation output from the second matched filter 16 is maximized with reference to the time acquired from the time measuring unit 18, and further corresponds to the feature points of the correlation curve. The time difference to be specified is specified (step S33). The reception time point specifying unit 17 corrects the correction value T corresponding to the specified time difference from the time point specified in step S33 (step S34), and ends the process of specifying the reception time point.

FIG. 16 is a graph illustrating an example of a correlation curve between the reception signal Sr (t) and the reproduction signal R ′ (t) after the arithmetic processing in the third embodiment. Note that the example shown in the graph of FIG. 16 is an example when an OFDM signal having a bandwidth of 7.8125 MHz is transmitted under the conditions of the transmission path shown in FIG. The reproduction signal R ′ (t) created based on the intensity ratio r of the backward delay signal and the delay time t _delay estimated by the method shown in FIG. 2 is a correlation curve between calculation signals after calculation processing by the calculation unit 192. Note that the reception time point T _c2 specified from the time point when the correlation of the correlation curve shown in FIG. 16 becomes maximum is the original reception time point, that is, the shortest signal reception time point calculated from the distance from the radio wave source RS to the reception point RP. It is assumed that it is 39 nanoseconds behind.

  That is, since the influence of the backward delay signal is already reproduced by the reproduction signal R ′ (t) and canceled by taking the correlation, the correlation curve shown in the graph of FIG. 16 is influenced by the delay signal having a short delay time. It is a manifested curve, and it can be considered that the time difference corresponding to the feature points is stretched by a delay signal with a short delay time.

Note that the correction value corresponding to the time difference between the feature points LM + LN shown in the graph of FIG. 16 when an OFDM signal with a bandwidth of 7.8125 MHz is transmitted is 24 ns in advance by simulation. It is sought and stored. Therefore, the reception time point specifying unit 17 uses 24 nanoseconds as the correction value, and specifies the time point obtained by subtracting the correction value from the time point T _c2 at which the correlation of the correlation curve becomes maximum as the reception time point T _c3 . Since the point of time T _c2 at which the correlation is maximized is incorrect with a delay of 39 nanoseconds from the original reception point, it is corrected 24 nanoseconds earlier, resulting in an error of 15 nanoseconds and higher accuracy. Note that 15 nanoseconds corresponds to a distance of 4.5 meters.

  As described above, the correlation between the calculation signal of the reception signal Sr (t) after the calculation process and the calculation signal of the reproduction signal R ′ (t) that reproduces the superposition of the delay signal is obtained, and between the feature points specified from the correlation curve A delay signal with a short delay time that is difficult to separate with a simple configuration that corrects the reception time point specified from the time point when the correlation of the correlation curve becomes maximum using a correction value stored in advance corresponding to the distance of It is possible to accurately identify the reception time point that reflects the influence of.

(Embodiment 4)
In the fourth embodiment, an example in which the receiving device 1 described in the first to third embodiments is applied to a positioning system that specifies the position of the receiving device 1 will be described.

  FIG. 17 is a block diagram showing a configuration of a positioning system in the fourth embodiment. The positioning system includes at least two transmission devices 2 and 2 whose position information is known in advance and one reception device 1. The transmitters 2 and 2 are fixed not at a moving body but at a position represented by position information. On the other hand, the receiving device 1 is a mobile body, and the receiving device 1 receives signals transmitted from the transmitting devices 2 and 2, respectively, and measures the distance from the arrival time from when the signal is transmitted until it is received. And configured to measure its own position. In the following description, among the internal configuration of receiving apparatus 1, components that are the same as those in Embodiment 1 are assigned the same reference numerals as in Embodiment 1 and detailed descriptions of the components are omitted. .

  The transmission device 2 transmits a control unit 20 that controls each component unit, a storage unit 21 that stores its position information, a time measuring unit 22 that measures time by counting at a predetermined frequency, and a signal. And a transmission unit 23. Note that the timer unit 22 of the transmission device 2 and the timer unit 18 of the receiver device 1 are required to be synchronized with high accuracy, but the synchronization method is not limited.

  The position information stored in the storage unit 21 is, for example, ID information that can specify the longitude and latitude or the position. The control unit 20 of the transmission device 2 reads the position information stored in the storage unit 21 at a predetermined timing, modulates the signal including the read position information by the transmission unit 23 using the orthogonal frequency division multiplexing modulation scheme, and transmits the signal. To do. The pilot signal is periodically transmitted when the transmitter 23 modulates the signal and transmits the modulated signal. And the control part 20 is made to transmit by including the time acquired from the time measuring part 22 at the time of transmitting a pilot signal as a transmission time.

  FIG. 18 is a block diagram showing an internal configuration of receiving apparatus 1 in the fourth embodiment. Receiving apparatus 1 according to Embodiment 4 receives not only each component for specifying a reception time point, but also a reception time point that demodulates the signal to acquire and specify transmission point information and transmission point information included in the signal. A component for measuring the position of itself is used.

  The receiving device 1 is based on an FFT processing unit 193 that performs an FFT process for demodulating a signal received by the receiving unit 10, a demodulation unit 194 that demodulates information from the received signal, and information output from the demodulation unit 194. A control unit 195 that performs control and an output unit 196 that outputs information.

  The FFT processing unit 193 receives the signal received by the receiving unit 10 and the correlation from the first matched filter 13 for symbol synchronization. The FFT processing unit 193 identifies the start of the symbol based on the correlation, performs FFT processing on each symbol, and inputs the result to the demodulation unit 194. The demodulation unit 194 demodulates the signal input from the FFT processing unit 193 for each subcarrier, performs parallel-serial conversion processing, and obtains position information and transmission time information of the transmission device 2 included in the signal received from the transmission device 2. Take out and output.

  The position information of the transmission device 2 and the transmission time information output from the demodulation unit 194 are input to the control unit 195. Further, information on the reception time point specified by the reception time point specifying unit 17 is also input to the control unit 195. The control unit 195 measures its own position based on the position information of the transmission device 2 and the transmission time information and the reception time information input from the demodulation unit 194. Specifically, the control unit 195 calculates the time difference between the transmission time points transmitted from the plurality of transmission devices 2 and the reception time point input from its own reception time point specifying unit 17, and based on the calculated time difference, The distance from the transmission device 2 is calculated. Then, the control unit 195 measures its own position based on the position specified by the position information of each of the transmission devices 2 and 2 and the calculated distance.

  The control unit 195 performs a predetermined process using the measured position. For example, the output unit 196 outputs information indicating the measured position. The output unit 196 may be configured to use a display device so as to overlap and display the map information stored in a storage unit (not shown), or may be an audio output device.

  In this way, using the receiving device 1 that can specify the reception time point with high accuracy, the time difference between the transmission time point and the reception time point, that is, the time required for the signal transmitted from the transmission device 2 to arrive is highly accurate. The distance can be measured from the measured time. Since the distance can be measured with high accuracy, the receiving device 1 can measure its own position with high accuracy.

  In the positioning system in the fourth embodiment, the receiving device 1 is a moving body, the distance from the two fixed transmitting devices 2 and 2 is measured, and the position of the receiving device 1 itself is determined based on the measured distance. It was set as the structure to measure. However, the positioning system is not limited to this, and one transmission device 2 is a moving body, and signals received from the transmission device 2 are received by two fixed reception devices 1 and 1, respectively, and the difference between the transmission time point and the reception time point It is good also as a structure which measures a distance from, and measures the position of the transmitter 2 from the measured distance.

  The positioning system in the fourth embodiment can be applied to, for example, a vehicle position measurement system that measures the position of a vehicle traveling on a road with high accuracy. The vehicle position measurement system, for example, accurately measures the distance from traffic lights installed at intersections to prevent traffic accidents between vehicles at or near the intersection, or between vehicles and pedestrians, and before the stop line. It is used in a system that reliably stops the vehicle. In this case, in order to effectively prevent a traffic accident, it is necessary to control the vehicle position to be correctly measured and stopped with an error of at least several meters. In such a vehicle position measurement system, a vehicle provided with the receiving device 1 shown in the first to fourth embodiments is used, and the transmitting device 2 shown in the fourth embodiment is installed in a traffic light, so that FIG. ), The distance from the traffic light can be measured with an error of less than 3 meters. Thereby, in an emergency, the vehicle can be effectively stopped, and an excellent effect is achieved.

  Needless to say, the receiving device 1 and the exemplified reception time specifying method shown in the first to fourth embodiments not only provide the above-described highly accurate measurement of the vehicle position but also the highly accurate position of the mobile communication device such as a mobile phone. It is also possible to apply to a system for measuring and detecting.

  The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

3 is a block diagram showing a configuration of a receiving apparatus in Embodiment 1. FIG. 6 is a flowchart illustrating an example of a processing procedure in which a reception time point is specified by the reception device according to Embodiment 1. 6 is an explanatory diagram illustrating an example of contents of a replica signal R (t) and a received signal Sr (t) stored in a storage unit of the receiving device in Embodiment 1. FIG. 6 is a graph illustrating an example of an impulse response obtained from a signal Sr (t) received by the receiving device in Embodiment 1. FIG. 6 is an explanatory diagram illustrating an example of a correlation between a reproduced signal R ′ (t) created based on a replica signal R (t) by the receiving device in Embodiment 1 and a received signal Sr (t). FIG. 10 is a flowchart illustrating an example of a processing procedure in which a reception time point is specified by a reception device according to Embodiment 2. It is explanatory drawing which shows the example which simulated the received signal in the case of receiving an OFDM signal via the transmission path which modeled the actual radio wave environment of the urban area. 10 is a graph showing a correlation between a received signal Sr (t) obtained by a receiving apparatus and a replica signal R (t) in the example in the second embodiment. FIG. 10 is a graph illustrating an example of an impulse response obtained by the receiving device in the example in the second embodiment. FIG. In the example in Embodiment 2, it is explanatory drawing which shows the example from which the impulse response of a back delay signal is removed from an impulse response. FIG. 10 is a block diagram illustrating a configuration of a receiving device according to Embodiment 3. FIG. 10 is an explanatory diagram schematically showing feature points included in a correlation curve between calculation signals output from a first calculation unit and a second calculation unit that constitute a receiving apparatus according to Embodiment 3. It is explanatory drawing which shows typically the example from which the correlation curve of the received signal Sr (t) and the replica signal R (t) changes under the influence of a delay signal. It is explanatory drawing which shows the example of the content of the correction value corresponding to the time difference corresponded between the feature points contained in a correlation curve. 10 is a flowchart illustrating an example of a processing procedure in which a reception time point is specified by a reception device according to Embodiment 3. FIG. 11 is a graph illustrating an example of a correlation curve between a reception signal Sr (t) after calculation processing and a reproduction signal R ′ (t) in the third embodiment. FIG. 10 is a block diagram illustrating a configuration of a positioning system in a fourth embodiment. FIG. 10 is a block diagram illustrating an internal configuration of a receiving device according to Embodiment 4.

Explanation of symbols

1 Receiving Device 10 Receiving Unit 11 Storage Unit R Replica Signal (Replication)
DESCRIPTION OF SYMBOLS 12 FFT processing part 14 Delay signal estimation part 15 Reproduction signal creation part 16 2nd matched filter 17 Reception time specific | specification part 191 1st calculating part 192 2nd calculating part 195 Control part 196 Output part 2 Transmitting device 22 Time measuring part 23 Transmitting part

Claims (11)

A receiver that stores a copy of a reference signal included in a signal to be transmitted and identifies a reception time point when the signal is received,
An analysis means for analyzing the delayed signal superimposed on the received signal;
Creating means for creating a correction reference signal for correcting the copy based on the delay signal analyzed by the analyzing means;
A receiving device comprising: means for specifying a reception time point of a signal based on a correlation between a received signal and a correction reference signal created by the creating means. The analysis means includes
Means for estimating a backward delay signal having a delay time longer than a reference time related to a bandwidth of the received signal among the delay signals;
Removing means for removing the backward delay signal from the received signal;
The receiving apparatus according to claim 1, further comprising: means for analyzing a delayed signal whose delay time is shorter than the reference time from the signal after the removing means removes the backward delay signal. First calculation means for obtaining a first calculation signal by a predetermined calculation using a real part and an imaginary part of the received signal;
Second calculation means for obtaining a second calculation signal by a predetermined calculation using a real part and an imaginary part of the correction reference signal;
The receiving apparatus according to claim 1, further comprising: means for specifying a reception time point of a signal based on a correlation between the first calculation signal and the second calculation signal. The analysis means includes
Means for obtaining an impulse response by obtaining a transfer function from the received signal;
Means for treating the obtained impulse response as a linear sum of two or more predetermined functions having time as a variable, and specifying the predetermined function using a least square method;
The receiving apparatus according to any one of claims 1 to 3, wherein a delay time and an intensity ratio of a delay signal with respect to a signal received earliest are estimated based on a specified function specified. . The receiving apparatus according to claim 4, wherein the predetermined function is a sinc function. The receiving apparatus according to claim 1, further comprising: means for extracting a signal in a range including the reference signal from the received signal. The receiving device according to claim 6, wherein the extraction unit extracts at least two ranges of signals having different time ranges from the received signal. A transmission device that transmits a signal including a reference signal and information at a transmission time point, and a reception device according to any one of claims 1 to 7,
The distance between the transmission device and the reception device is measured from the time difference between the transmission time point included in the signal received from the transmission device by the reception device and the reception time point specified by the reception device. Distance system. A positioning apparatus that includes a transmitting device that transmits a signal including a reference signal and information at a transmission time point, and a receiving device according to any one of claims 1 to 7, and that measures the position of the transmitting device or the receiving device. There,
A plurality of at least one of the transmission device or the reception device is provided,
Means for storing position information of a device provided with any one of the transmitting device and the receiving device;
Ranging means for measuring a distance from a transmission time point included in a signal transmitted from the transmission device, and a time difference between reception time points specified by the reception device;
A positioning system comprising: means for measuring a position of an apparatus in which position information of the transmitting apparatus or the receiving apparatus is unknown based on the position information and the distance measured by the ranging means. A computer program that receives a signal to be transmitted, stores a copy of a reference signal included in the signal, and identifies a reception time when the signal is received,
Computer
Analysis means for analyzing the delayed signal superimposed on the received signal;
Based on the delay signal analyzed by the analysis means, a creation means for creating a correction reference signal that corrects the duplicate; and
A computer program that functions as means for specifying a reception time of a signal based on a correlation between a received signal and a correction reference signal created by the creating means. A reception time specifying method for storing a copy of a reference signal included in a signal to be transmitted and specifying a reception time when the signal is received,
Analyzing the delayed signal superimposed on the received signal,
Based on the analyzed delay signal, create a correction reference signal that corrects the replication,
A reception time specifying method, characterized in that a signal reception time is specified based on a correlation between a received signal and a created correction reference signal.

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