Signal generating device, signal generating system, and signal generating method

Abstract

To provide a signal generator capable of securing continuity of a waveform simulating propagation delay and frequency shift for change in a Doppler coefficient.SOLUTION: A signal generator that simulates propagation delay and frequency shift includes storage means for storing propagation delay for each processing block which is a unit of signal processing, coefficient change degree calculation means for calculating a Doppler coefficient change degree between successive processing blocks on the basis of, propagation delay, determination means for determining whether the Doppler coefficient change degree is equal to or less than a threshold value, dividing means for dividing a processing block into a plurality of sub-blocks when the Doppler coefficient change degree is larger than a threshold value, sample position calculating means for calculating sample point positions requiring interpolation for each sub-block on the basis of propagation delay, interpolation processing means for executing interpolation processing for each sub-block on the basis of the sample point positions, and delay processing means for executing sample delay for each sub-block after the interpolation processing on the basis of, the propagation delay.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a signal generating device, a signal generating system, and a signal generating method for generating a signal that simulates a propagation delay and a frequency shift. [Background technology]

[0002] Conventionally, a signal generating device is known that generates a signal simulating the propagation delay of a wave and the frequency shift due to the Doppler effect in a simulator that simulates the propagation of a wave from a sound source to a receiving point. In addition, although it is not a signal generating device, when the wave to be analyzed is a radio wave, a marine radar observation device is known that emits a radio wave onto the ocean surface, measures the reflected wave, and observes oceanographic information such as ocean currents (for example, see Patent Document 1).

[0003] The marine radar observation device disclosed in Patent Document 1 divides the observation range in the range direction into blocks to deal with noise from water level fluctuations generated by ships, calculates a flow regression curve within each divided block, and detects and corrects abnormal flux values ​​based on the deviation from the regression curve and the standard deviation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-83992 Summary of the Invention [Problem to be solved by the invention]

[0005] The marine radar observation device disclosed in Patent Document 1 performs correction processing with a constant block length. If the technology disclosed in Patent Document 1 is applied to a signal generation device and the length of the processing block, which is the unit of signal processing, is constant, if the Doppler coefficient changes significantly between blocks, it may not be possible to simulate a waveform that ensures continuity between processing blocks. This is because, for example, when the distance between the sound source and the receiving point is close, the Doppler coefficient changes significantly between consecutive blocks compared to when the distance between the sound source and the receiving point is far. [Means for solving the problem]

[0006] The signal generating device of the present invention is a signal generating device that simulates a propagation delay and a frequency shift for a waveform, and has: a storage means for storing a propagation delay for each processing block, which is a unit of signal processing, for the waveform; a coefficient change degree calculation means for calculating a Doppler coefficient change degree between successive processing blocks based on the propagation delay; a determination means for determining whether the Doppler coefficient change degree is equal to or less than a predetermined threshold value; a division means for dividing the processing block into a plurality of sub-blocks if the Doppler coefficient change degree is greater than the threshold value; a sample position calculation means for calculating sample point positions requiring interpolation for each sub-block based on the propagation delay; an interpolation processing means for performing interpolation processing for each sub-block based on the sample point positions; and a delay processing means for performing a sample delay for each sub-block after the interpolation processing based on the propagation delay.

[0007] The signal generation system of the present invention is a signal generation system that simulates a propagation delay and a frequency shift for a waveform, and has: a storage means for storing a propagation delay for each processing block, which is a unit of signal processing, for the waveform; a coefficient change degree calculation means for calculating a Doppler coefficient change degree between successive processing blocks based on the propagation delay; a determination means for determining whether the Doppler coefficient change degree is equal to or less than a predetermined threshold value; a division means for dividing the processing block into a plurality of sub-blocks if the Doppler coefficient change degree is greater than the threshold value; a sample position calculation means for calculating sample point positions requiring interpolation for each sub-block based on the propagation delay; an interpolation processing means for performing interpolation processing for each sub-block based on the sample point positions; and a delay processing means for performing a sample delay for each sub-block after the interpolation processing based on the propagation delay.

[0008] The signal generation method of the present invention is a signal generation method by an information processing device that simulates a propagation delay and a frequency shift for a waveform, and includes the steps of: storing a propagation delay for each processing block, which is a unit of signal processing, for the waveform; calculating a degree of change in Doppler coefficient between successive processing blocks based on the propagation delay; determining whether the degree of change in Doppler coefficient is equal to or less than a predetermined threshold; if the degree of change in Doppler coefficient is greater than the threshold, dividing the processing block into a plurality of sub-blocks; calculating sample point positions requiring interpolation for each sub-block based on the propagation delay; performing interpolation processing for each sub-block based on the sample point positions; and performing a sample delay for each sub-block after the interpolation processing based on the propagation delay. Effect of the Invention

[0009] According to the present invention, a threshold is determined for the Doppler coefficient change rate, and when the Doppler coefficient change rate is small, a waveform is estimated in units of processing blocks, and when the Doppler coefficient change rate is large, the processing blocks are automatically divided into sub-blocks of finer block lengths to estimate the waveform. Therefore, even if the change in the Doppler coefficient between successive processing blocks is large, a waveform that ensures continuity can be simulated. [Brief description of the drawings]

[0010] [Figure 1] 4 is a schematic diagram showing an example of time changes in the position vector of a sound source and the position vector of a wave receiving point. FIG. [Diagram 2] FIG. 1 is a schematic diagram for explaining a first comparative example. [Diagram 3] FIG. 11 is a schematic diagram for explaining a second comparative example. [Figure 4] FIG. 13 is a schematic diagram for explaining a third comparative example. [Diagram 5] 1 is a diagram illustrating an example of a configuration of a signal generating device according to a first embodiment. [Figure 6] 6 is a functional block diagram showing an example of the configuration of a control unit shown in FIG. 5. [Figure 7] 7 is a functional block diagram showing an example of the configuration of a division unit shown in FIG. 6. [Figure 8] 4 is a flowchart showing an example of an operation procedure of the signal generating device according to the first embodiment. [Figure 9] 7 is a diagram showing an example of information stored in a propagation delay memory and a propagation delay sub-memory shown in FIG. 6. [Figure 10] 9 is a flowchart showing an example of an operational procedure of a dividing means in the process of step S108 shown in FIG. 8. [Figure 11] 1 is a block diagram showing an example of a configuration of a signal generation system according to a first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Embodiment 1 In the present embodiment 1, the signal generating device is described as a device that generates a signal simulating a propagation delay and a frequency shift due to the Doppler effect in a simulator that simulates wave propagation. Before describing the signal generating device of the present embodiment 1, the wave that the signal generating device simulates will be described by taking sound propagation as an example. Note that, since it is difficult to express Greek or Roman letters indicating various parameters in a text as vectors (bold notation, arrows above letters, etc.), vector notation in the text will be omitted below.

[0012] Fig. 1 is a schematic diagram showing an example of time changes in the position vector of a sound source and the position vector of a receiving point. As shown in Fig. 1, it is necessary to consider a situation in which the position vector ps of the sound source and the position vector pr of the receiving point change over time with the movement of one or both of the sound source and the receiving point. In other words, when generating a pseudo signal that simulates a received signal at a receiving point to which a sound radiated from a sound source has propagated, a signal that has been frequency shifted due to a propagation delay and the Doppler effect is simulated.

[0013] Next, in order to facilitate understanding of the signal generation method by the signal generating device of the first embodiment, three comparative examples will be described as a method of simulating a signal that undergoes frequency shift due to propagation delay and the Doppler effect.

[0014] First, a first comparative example will be described with reference to Fig. 2. The first comparative example is a phase integration method. Fig. 2 is a schematic diagram for explaining the first comparative example. It is assumed that a sound source signal s(n) is expressed by equation (1).

[0015]

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[0016] In equation (1), f is the signal frequency [Hz], φ0 is the initial phase [rad], f sis the sampling frequency [Hz], and n is the discrete time index. As shown in Figure 2, the propagation delay time in processing block 1 is τ1 [s] and the Doppler coefficient is d1, and the propagation delay time in the following processing block 2 is τ2 [s] and the Doppler coefficient is d2. A processing block is, for example, a signal that is cut out within a determined time range as a unit of signal processing for a sound source signal time waveform that shows the time change of the waveform of the sound source signal. The Doppler coefficient is the ratio at which the frequency changes depending on the relative speed between the sound source and the receiving point, and is shown in equation (2).

[0017]

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[0018] In equation (2), f' is the changed frequency [Hz], and c is the speed of sound [m / s]. vs' is the magnitude of vector vs', and represents the velocity component [m / s] in the direction of the sound source receiving point. vr' is the magnitude of vector vr', and represents the velocity component [m / s] in the opposite direction to the sound source direction at the receiving point. The received signal x1(t) after propagation through processing block 1 and the received signal x2(t) after propagation through processing block 2 are expressed in equations (3) to (5).

[0019]

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[0020]

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[0021]

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[0022] Here, the initial phase φ1 of processing block 2 is the phase at the end of processing block 1 calculated by equation (5). The equations expanded to processing block l are shown in equations (6) and (7).

[0023]

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[0024]

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[0025] The phase integration method is a method in which the Doppler coefficient is expressed in the phase rotation speed of the narrowband signal as shown in equations (6) and (7), and the phase is integrated so that the phase at the end of a processing block becomes the initial phase of the next processing block.

[0026] Next, a second comparative example will be described with reference to FIG. 3. The second comparative example is a sample update method. FIG. 3 is a schematic diagram for explaining the second comparative example. As shown in FIG. 3, in the sample update method, a waveform consisting of a series in which a propagation delay that can change for each sample of the sound source waveform is given is obtained. For example, by convolving a delay filter hn=[hn(0),hn(1),...,hn(M)] based on a finite impulse response in which the propagation delay changes every time, with the sound source signal s(n), a waveform x(n) is obtained as shown in equation (8).

[0027]

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[0028] Next, a third comparative example will be described with reference to FIG. 4. The third comparative example is a processing block expansion / contraction method. FIG. 4 is a schematic diagram for explaining the third comparative example. As shown in FIG. 4, when the propagation delay time of the processing block l is τ l and the propagation delay time of the subsequent processing block l+1 is τ l+1 When τ l+1 -τ l If ≠ 0, the end of processing block l is τ due to the continuity of the waveform. l+1 In other words, the time length of processing block l is considered to be equal to the propagation delay of N block [Sample] to N block +(τ l+1 -τl )*f s By stretching the waveform to [samples], the continuity of the waveform can be maintained. In addition, stretching the waveform is equivalent to shifting the frequency by the Doppler coefficient d shown in equation (9).

[0029]

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[0030] The waveform x(n) after the processing block is expanded or contracted is the source waveform s(n) = {s(0),s(1),...,s(N block -1),s(N block )} as shown in equation (10).

[0031]

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[0032] Note that s(d), s(2d),..., which are shifted from the sample points of the original discrete sound source waveform s(n), are obtained by interpolation.

[0033] Three comparative examples have been described so far, but each has the following problems. The phase integration method, which is the first comparative example, can simulate a frequency shift by changing the phase rotation speed. However, the signals that can be applied are limited to narrowband signals. Also, the length of the output processing block is the same as the length of the input processing block, and these lengths are constant. Therefore, there is a problem that the propagation delay of the signal in processing block 1 appears only in the Doppler coefficient and is not taken into account as the reception time.

[0034] The sample update method, which is the second comparative example, can accurately simulate the propagation delay and frequency shift for any signal waveform by convolving a delay filter that expresses the propagation delay that changes for each sample. The propagation delay is reflected in the reception time, but there is a problem in that the calculation cost is high because the propagation delay is calculated for each sample.

[0035] The processing block expansion / contraction method, which is the third comparative example, can simulate frequency shifts on a block-by-block basis by expanding or contracting the signal waveform within the processing block. However, unlike the sample update method, this method is not suitable for cases where the Doppler coefficient changes significantly within the processing block, since the Doppler coefficient is uniform within the processing block. In this case, it is possible to deal with this by setting the processing block length short enough that the Doppler coefficient can be considered constant within the processing block, but shortening the processing block length uniformly requires consideration of the trade-off with calculation costs.

[0036] The signal generating device of the first embodiment is intended to solve these problems. The configuration of the signal generating device of the first embodiment will be described. Fig. 5 is a diagram showing an example of the configuration of the signal generating device according to the first embodiment.

[0037] The signal generating device 1 is an information processing device such as a computer. As shown in Fig. 5, the signal generating device 1 has an input unit 2, a storage unit 3, a control unit 4, and an output unit 5. The storage unit 3 is, for example, a hard disk drive (HDD) device. The output unit 5 is, for example, a display device. The control unit 4 has a memory 11 that stores a program, and a central processing unit (CPU) 12 that executes processing according to the program. The memory 11 is, for example, a non-volatile memory such as a flash memory. A sound source signal time waveform that is a reference for a simulation signal is input to the input unit 2.

[0038] Fig. 6 is a functional block diagram showing an example of the configuration of the control unit shown in Fig. 5. The control unit 4 has a processing block update means 21, a coefficient change degree calculation means 22, a determination means 23, a sample position calculation means 31, an interpolation processing means 32, and a delay processing means 33. The control unit 4 also has a division means 41 and a sub-block update means 43. The processing block update means 21, the coefficient change degree calculation means 22, the determination means 23, the sample position calculation means 31, the interpolation processing means 32, the delay processing means 33, the division means 41, and the sub-block update means 43 are configured by the CPU 12 executing a program.

[0039] The storage unit 3 is divided into a plurality of memory areas. In the configuration example shown in Fig. 6, the storage unit 3 has an excitation waveform block memory 51, a propagation delay memory 52, and a sub-memory 53 as memory areas for storing data. The excitation waveform block memory 51 is a storage means for storing an excitation signal time waveform for each processing block. The propagation delay memory 52 is a storage means for storing a propagation delay for each processing block. The propagation delay memory 52 stores a pair of the block length and the propagation delay of a processing block in correspondence with a block index.

[0040] The sub-memory 53 has an excitation waveform sub-block memory 54 and a propagation delay sub-memory 55. The area of ​​the sub-memory 53 is created in the storage unit 3 by the dividing means 41. The excitation waveform sub-block memory 54 stores an excitation signal time waveform of a time range corresponding to each sub-block divided by the dividing means 41. The propagation delay sub-memory 55 stores a pair of a block length of a sub-block and a propagation delay corresponding to a sub-block index of the number of sub-blocks. A sub-block is one time range when a processing block is divided into a plurality of blocks.

[0041] The processing block update means 21 receives an excitation signal time waveform and a block index, and stores the excitation signal time waveform in the range of a processing block to be subjected to propagation delay and frequency shift in the excitation waveform block memory 51. In the first embodiment, the propagation delay memory 52 stores the propagation delay for each processing block, but the processing block update means 21 may function as a propagation delay calculation means for calculating a propagation delay for each processing block with respect to the excitation signal time waveform.

[0042] The coefficient change degree calculation means 22 reads out the propagation delay at the time corresponding to the block index from the propagation delay memory 52, receives the read propagation delay as an input, calculates the Doppler coefficient change degree, and outputs the Doppler coefficient change degree to the determination means 23. The determination means 23 receives the Doppler coefficient change degree as an input and determines whether the Doppler coefficient change degree is equal to or less than a predetermined threshold value. The determination means 23 notifies the coefficient change degree calculation means 22, the sample position calculation means 31, and the division means 41 of information on the determination result.

[0043] When the Doppler coefficient change rate is greater than a threshold value, the division means 41 reads out the propagation delay at the time corresponding to the block index from the propagation delay memory 52, and inputs the read out propagation delay and the Doppler coefficient change rate to determine the interpolated propagation delay and block length of the sub-block, and stores them in the propagation delay sub-memory 55.

[0044] The configuration of the division means 41 will be described with reference to Fig. 7. Fig. 7 is a functional block diagram showing an example of the configuration of the division means shown in Fig. 6. The division means 41 has a block length calculation means 141 and a propagation delay interpolation processing means 142.

[0045] The block length calculation means 141 refers to the propagation delay memory 52 to read out the propagation delay at the time corresponding to the block index, receives the read propagation delay and the Doppler coefficient change rate as input, divides the processing block into a plurality of sub-blocks, and outputs information on the number of sub-blocks and the block lengths of the sub-blocks to the propagation delay interpolation processing means 142. The propagation delay interpolation processing means 142 refers to the propagation delay memory 52 to read out the propagation delay at the time corresponding to the block index, receives the read propagation delay and the block length as input, performs propagation delay interpolation processing, and updates the information stored in the propagation delay sub-memory 55.

[0046] 6 reads out the block length of a sub-block corresponding to the sub-block index from the propagation delay sub-memory 55, and reads out the excitation signal time waveform of the time range corresponding to the block index from the excitation waveform block memory 51. The sub-block updating means 43 receives the read block length and excitation signal time waveform and the sub-block index as input, and stores the excitation signal time waveform of the time range corresponding to the sub-block index in the excitation waveform sub-block memory 54.

[0047] If the Doppler coefficient change rate is equal to or lower than the threshold, the sample position calculation means 31 reads out the propagation delay at the time corresponding to the block index from the propagation delay memory 52, receives the read propagation delay as input, and outputs information on the sample point position to the interpolation processing means 32. If the Doppler coefficient change rate is greater than the threshold, the sample position calculation means 31 reads out the propagation delay corresponding to the subblock index from the propagation delay sub-memory 55, receives the read propagation delay and the block length as input, calculates the sample point position, and outputs information on the sample point position to the interpolation processing means 32.

[0048] The interpolation processing means 32 receives as input the sound source signal time waveform of the processing block stored in the sound source waveform block memory 51 and the sample point position, generates a signal representing a phase delay and a frequency shift, and outputs the signal to the delay processing means 33. The interpolation processing means 32 reads out the sound source signal time waveform of the time range corresponding to the subblock index from the sound source waveform subblock memory 54, receives the read sound source signal time waveform and the sample point position as input, generates a signal representing a phase delay and a frequency shift, and outputs the signal to the delay processing means 33.

[0049] The delay processing means 33 reads out the propagation delay at the time corresponding to the block index from the propagation delay memory 52, receives the read propagation delay and a signal representing the phase delay and frequency shift as input, generates a waveform after the propagation delay and frequency shift, and outputs it to the output unit 5 shown in Fig. 5. The delay processing means 33 reads out the propagation delay corresponding to the sub-block index from the propagation delay sub-memory 55, receives the read propagation delay and a signal representing the phase delay and frequency shift as input, generates a waveform after the propagation delay and frequency shift, and outputs it to the output unit 5 shown in Fig. 5.

[0050] In the present embodiment 1, as shown in FIG. 6, the sound source waveform block memory 51, the propagation delay memory 52 and the sub-memory 53 are described as being provided in the storage unit 3, but these memories may also be provided in the memory 11 shown in FIG. 5.

[0051] Next, the operation of the signal generating device 1 of the present embodiment 1 will be described. Fig. 8 is a flowchart showing an example of an operation procedure of the signal generating device according to the embodiment 1. Fig. 9 is a diagram showing an example of information stored in the propagation delay memory and the propagation delay sub-memory shown in Fig. 6.

[0052] Here, we consider a case where the signal generating device 1 generates a pseudo signal that simulates the received waveform at the receiving point in a situation where the position vectors of the sound source and the receiving point change over time, taking sound propagation as an example. As shown in the upper part of Fig. 9, the propagation delay memory 52 stores the propagation delay at the time corresponding to each processing block.

[0053] As a sound source signal time waveform, a sound source time signal s(n) shown in equation (11) is input to the control unit 4 (step S101). In step S102, the processing block update means 21 receives the sound source time signal s(n) and updates a set n of time indexes corresponding to the block index l. l Time waveform s(n l ) is stored in the sound source waveform block memory 51. In step S102, the processing blocks are updated in sequence in accordance with the block index l. l is shown in equation (12), where the block index l is the index of the processing block, and L is the total number of processing blocks.

[0054]

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[0055]

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[0056] Propagation delay τ required for the processing after step S102 l , τ l+1 , τ l+2 is the propagation delay memory 52 stores τ={τ1, τ2, . . . , τ L} based on the block index l. In step S103, the coefficient change degree calculation means 22 calculates the propagation delay τ l , τ l+1 , τ l+2 Enter this into the following equation (13) to obtain the Doppler coefficient change Δd l Calculate.

[0057]

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[0058] In step S104, the determination means 23 determines the Doppler change rate |Δd l| is compared with a predetermined threshold δ, and the Doppler change |Δd l The Doppler change degree |Δd is judged to be equal to or smaller than a threshold value δ. When the calculation cost is important, the threshold value δ is set to a large value close to 0.01, and when the degree of simulation is important, a small value close to 0 is set. l When | is equal to or smaller than the threshold value δ, it is considered that the Doppler coefficient does not change significantly in the time range corresponding to the block index l. Therefore, the coefficient change degree calculation means 22 estimates the expansion / contraction ratio of the processing block using the propagation delay difference between successive processing blocks, without using information on the relative speed between the sound source and the wave receiving point.

[0059] In step S105, the sample position calculation means 31 expands or contracts the entire processing block by the estimated expansion / contraction rate, obtains the corresponding sample points by interpolation, and calculates the positions of the sample points after the propagation delay and frequency shift. l ' is calculated for a set of time indexes n l ' is shown in equation (14).

[0060]

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[0061] In equation (14), N block ' is the number of samples N block is the number of samples after waveform stretching of processing block l. l is the Doppler coefficient corresponding to the block index, and is shown in the second term of equation (13). l is the initial sample shift position expressed by equation (15).

[0062]

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[0063] In formula (15), the symbol floor[ ] represents an operation to truncate the decimal point. %x represents the remainder when dividing by x, and is a process to make {1}%1=0 when the value inside {} becomes 1.

[0064] If it is a fractional sample delay, then the integer sample delay floor[τ l f s ] fraction τ l f s -floor[τ l f s The original start time of the block is shifted by ]. The waveform is sampled at the original time scale sample time {1-(τ l f s -floor[τ l f s However, if the Doppler effect occurs, the start time is shifted by a factor of two.

[0065] In step S106, the interpolation processing means 32 performs waveform interpolation processing as follows. The interpolation processing means 32 estimates an interpolation function, which is a continuous signal, from a series of discrete points of the waveform. Specifically, the interpolation processing means 32 estimates an interpolation function, which is a continuous signal, from a series of discrete points of the waveform. l ) to obtain a continuous spline function f(n)(lN block ≦n≦(l+1)N block Then, the interpolation processing means 32 calculates the set of time indexes n l ' is substituted into the spline function to obtain the waveform s'(n) after fractional sample delay and frequency shift. The waveform s'(n) is shown in equation (16).

[0066]

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[0067] In step S107, the delay processing means 33 calculates the sample delay floor[τ l f s ] is the amount of shift in the waveform.

[0068]

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[0069] On the other hand, as a result of the determination in step S104, the Doppler change rate |Δd l If | is greater than the threshold δ, the Doppler coefficient changes significantly in the corresponding time range. Therefore, the control unit 4 of the first embodiment proceeds to the process of step S108, divides the processing block into small sub-blocks that can track the change in the Doppler coefficient, and performs a process of calculating the propagation delay and frequency shift in sub-block units. Here, the Doppler change |Δd l The ratio of | to the threshold δ is a = |Δd l Let | / δ>1.

[0070] In step S108, the division means 41 divides the processing block into floor[a]+1 sub-blocks in the block index l as shown in Fig. 9. As a result, the sub-blocks are divided into equal parts of the block length of the processing block (N block / floor[a]+1) samples. The division means 41 calculates the propagation delay from a Doppler coefficient obtained by interpolating between successive sub-blocks. The operation of the division means 41 will be described in detail later.

[0071] In step S109, the subblock update means 43 receives the sound source time signal s(n) and updates a set of time indexes n corresponding to the subblock index l'. l, Time waveform s(n l, ) is stored in the excitation waveform subblock memory 54. In step S109, the subblocks are updated in sequence in accordance with the subblock index l'. The excitation time signal s(n) is shown in equation (18), and the set of time indexes n l, is shown in equation (19).

[0072]

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[0073]

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[0074] In step S110, the sample position calculation means 31 performs the same calculation process as described in step S105, but for a sub-block instead of a processing block. l, ' is calculated for a set of time indexes n l, ' is shown in equation (20).

[0075]

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[0076] In equation (20), N block '' is the number of samples (N block / floor[a]+1) after waveform stretching of sub-block l'. l, is the Doppler coefficient corresponding to the subblock index. l, is the initial sample shift position expressed by the following equation (21).

[0077]

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[0078] In step S111, the interpolation processing means 32 performs waveform interpolation processing as follows. The interpolation processing means 32 interpolates the original waveform s(n l, ) to obtain a continuous spline function f(n)(lN block +(l'-1)(N block / floor[a]+1)≦n <lN block +l'(N block Then, the interpolation processing means 32 calculates the set of time indexes n input from the sample position calculation means 31.l, ' is substituted into the spline function to obtain the waveform s'(n) after fractional sample delay and frequency shift. The waveform s'(n) is shown in equation (22).

[0079]

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[0080] In step S112, the delay processing means 33 calculates the sample delay floor[τ l, 'f s ] is the amount of shift in the waveform.

[0081]

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[0082] When the sub-block update means 43 receives the information on the sub-block index from the delay processing means 33, it updates the sub-block index (step S113) and returns to step S109. The control unit 4 repeats the processes of steps S109 to S113 until the sub-block index l'=1,...,L' (where L'=floor[a]+1). As a result, for the block index l when it is determined in step S104 that the Doppler coefficient change rate is greater than the threshold value δ, a waveform after propagation delay and frequency shift is output from the delay processing means 33.

[0083] When the processing block update means 21 receives the block index information from the delay processing means 33, it updates the block index (step S114) and returns to step S102. The control unit 4 repeats steps S102 to S114 up to block index l=1,...,L, so that the waveforms after the propagation delay and frequency shift for the sound source waveform over the entire time are output from the delay processing means 33. In this way, a signal simulating the propagation delay and frequency shift at the wave receiving point is generated while ensuring the continuity of the waveform.

[0084] Next, the operation of the division means 41 in the process of step S108 shown in Fig. 8 will be described with reference to Fig. 7, Fig. 9, and Fig. 10. Fig. 10 is a flowchart showing an example of the operation procedure of the division means in the process of step S108 shown in Fig. 8.

[0085] Doppler coefficient change rate |Δd l When |=aδ (a>1), it is assumed that the Doppler coefficient changes linearly in order to reduce the load of calculation processing. In step S201, the block length calculation means 141 divides the original processing block length into floor[a]+1 equal parts, so that the Doppler coefficient change degree between sub-blocks can be set to the threshold value δ or less. That is, the Doppler coefficients of floor[a]+1 sub-blocks in the block index are as shown below (Equation (24)).

[0086]

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[0087] Next, the propagation delay interpolation processing means 142 sequentially obtains the propagation delay by equation (25) obtained by modifying equation (9) from the Doppler coefficient obtained by the interpolation as described above (step S202).

[0088]

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[0089] Here, the propagation delay interpolation processing means 142 uses τ1'=τ1 as the initial sub-block propagation delay. The propagation delay interpolation processing means 142 solves this for l'=1,2,...,floor[a] to obtain information to be stored in the propagation delay sub-memory 55. The information stored in the propagation delay sub-memory 55 is shown in the lower part of FIG.

[0090] The signal generating device 1 of the first embodiment includes a storage means for storing a propagation delay for each processing block, which is a unit of signal processing for a waveform, a coefficient change degree calculation means, a determination means, a division means, a sample position calculation means, an interpolation processing means, and a delay processing means. The storage means is, for example, a propagation delay memory 52. ​​The coefficient change degree calculation means 22 calculates a Doppler coefficient change degree between successive processing blocks based on the propagation delay. The determination means 23 determines whether the Doppler coefficient change degree is equal to or less than a predetermined threshold. If the Doppler coefficient change degree is greater than the threshold, the division means 41 divides the processing block into a plurality of sub-blocks. The sample position calculation means 31 calculates a sample point position that requires interpolation for each sub-block based on the propagation delay. The interpolation processing means 32 executes an interpolation process for each sub-block based on the sample point position. The delay processing means 33 executes a sample delay for each sub-block after the interpolation process based on the propagation delay.

[0091] According to the first embodiment, a threshold is determined for the Doppler coefficient change rate, and when the Doppler coefficient change rate is small, the waveform is estimated in units of processing blocks, and when the Doppler coefficient change rate is large, the processing block is automatically divided into sub-blocks with smaller block lengths to estimate the waveform. When the sound source is farther away than the receiving point and the Doppler coefficient changes slowly, the processing is performed in units of processing blocks, so that the calculation cost of the required calculation is small. Also, when the receiving point is close to the sound source, such as in the vicinity of the closest point of approach (CPA), and the Doppler coefficient changes suddenly, the processing block is divided into a plurality of sub-blocks for processing, so that not only the phase continuity of the waveform but also the continuity of the Doppler change can be simulated. In the first embodiment, by applying a block stretching method with an adaptive block length estimated according to the rate of change of the Doppler coefficient, the continuity of the waveform of the simulated signal can be ensured and the calculation cost can be reduced even if the Doppler coefficient changes significantly between processing blocks.

[0092] In the first comparative example, the length of the input processing block and the length of the output processing block are the same and constant, whereas in this embodiment 1, a block stretching method is applied in response to the rate of change of the Doppler coefficient to estimate a simulation signal.

[0093] In the second comparative example, the propagation delay is expressed for each sample and a delay filter is convolved to expand or contract the waveform, which increases the calculation cost. In contrast, in the first embodiment, the propagation delay for each processing block is used, and when the Doppler coefficient change rate is equal to or less than the threshold, calculation processing is performed for each processing block, which reduces the calculation cost.

[0094] In the third comparative example, the Doppler coefficient is uniform within the processing block, so the accuracy of the simulation signal decreases when the Doppler coefficient changes significantly within the processing block. In contrast, in the first embodiment, the estimation is performed by applying a block stretching method with an adaptive block length corresponding to the rate of change of the Doppler coefficient, so that the calculation cost can be reduced and the accuracy of the simulation signal can be improved.

[0095] (Description of Usage of First Embodiment) In the above-mentioned first embodiment, the propagation of sound has been described as an example, but the present invention can also be applied to any wave, such as radio waves used in radar.

[0096] In the above-mentioned embodiment 1, the propagation delay memory 52 stores information on the propagation delay times of all the processing blocks. However, the propagation delay calculation only requires the delay times of three consecutive processing blocks. Specifically, the delay times are the delay times of the processing block l and the processing blocks l+1 and l+2 following the processing block l. The propagation delay memory 52 stores the propagation delays of the processing blocks l and l+1 that it stores, and the newly calculated propagation delay of the processing block l+2. After the processing of step S107 or S111 shown in FIG. 8 is performed, the propagation delay memory 52 erases the propagation delay of the processing block l in the processing of step S102, and stores the propagation delays of the processing blocks l+1 and l+2. The propagation delay memory 52 can reduce the required memory capacity by sequentially changing the propagation delays to be stored and the propagation delays to be erased. The processing block update means 21 may manage the information stored in the propagation delay memory 52 as described above.

[0097] 8, spline interpolation has been described as an example in which the waveform interpolation always passes through sample data points, the first and second derivatives of block boundary points are continuous, and it is easy to output a value at any position, but the interpolation method is not limited to this. Linear interpolation, Lagrange interpolation, or the like may be used as long as the interpolation process can output a value at any interpolation position, taking into account the amount of calculation and the effect on the signal processing at the subsequent stage.

[0098] In the above-mentioned first embodiment, the case of a single information processing device has been described, but the signal generation system may have a plurality of information processing devices. FIG. 11 is a block diagram showing an example of a configuration of the signal generation system according to the first embodiment. The signal generation system 10 has information processing devices 101 to 103. The information processing devices 101 to 103 are connected to each other via a network 200 such as the Internet. The information processing device 101 has the storage unit 3 shown in FIG. 6. The information processing device 102 has the sample position calculation means 31, the interpolation processing means 32, and the delay processing means 33 of the control unit 4 shown in FIG. 6. The information processing device 103 has the processing block update means 21, the coefficient change degree calculation means 22, the determination means 23, the division means 41, and the sub-block update means 43 of the control unit 4 shown in FIG. 6. In the case of the configuration example shown in FIG. 11, the arithmetic processing required for executing the signal generation method of the first embodiment is shared and performed by the plurality of information processing devices 101 to 103, so that the speed of the arithmetic processing can be increased. [Explanation of symbols]

[0099] 1 Signal generator 2 Input section 3 Storage section 4. Control section 5 Output section 10 Signal Generation System 11. Memory 12 CPU 21 Processing block update means 22 Coefficient change degree calculation means 23 Judgment means 31 Sample position calculation means 32 Interpolation processing means 33 Delay Processing Methods 41 Division means 43 Subblock Update Method 51 Sound source waveform block memory 52 Propagation Delay Memory 53 Sub Memory 54 Sound source waveform subblock memory 55 Propagation Delay Sub-Memory 101~103 Information processing equipment 141 Block length calculation method 142 Propagation delay interpolation processing means 200 Network

Claims

1. 1. A signal generator for simulating a propagation delay and a frequency shift for a waveform, comprising: A storage means for storing a propagation delay for each processing block, which is a unit of signal processing, for the waveform; a coefficient variation calculation means for calculating a Doppler coefficient variation between successive processing blocks based on the propagation delay; a determination means for determining whether the Doppler coefficient change rate is equal to or less than a predetermined threshold; a dividing means for dividing the processing block into a plurality of sub-blocks when the Doppler coefficient change rate is greater than the threshold value; a sample position calculation means for calculating sample point positions requiring interpolation for each of the sub-blocks based on the propagation delay; an interpolation processing means for executing an interpolation process for each of the sub-blocks based on the sample point positions; a delay processing means for executing a sample delay for each of the sub-blocks after the interpolation processing based on the propagation delay; A signal generating device having the following:

2. The coefficient variation degree calculation means estimating a stretching ratio of the sub-blocks using a propagation delay difference between the successive sub-blocks; 2. A signal generating device according to claim 1.

3. The dividing means is interpolating the propagation delays such that the Doppler coefficient varies linearly between successive sub-blocks; 3. A signal generating device according to claim 1 or 2.

4. The sample position calculation means calculating the sample point positions in the sub-blocks based on the propagation delay times corresponding to the sub-blocks and the expansion / contraction ratios estimated by the coefficient variation degree calculation means; 3. A signal generating device according to claim 2.

5. The interpolation processing means an interpolation function, which is a continuous signal, is estimated from the discrete point series of the waveform, and the values ​​of the sample point positions are input to the interpolation function to output values ​​of positions between the discrete points; A signal generating device according to any one of claims 1 to 4.

6. 1. A signal generation system for simulating a propagation delay and a frequency shift for a waveform, comprising: A storage means for storing a propagation delay for each processing block, which is a unit of signal processing, for the waveform; a coefficient variation calculation means for calculating a Doppler coefficient variation between successive processing blocks based on the propagation delay; a determination means for determining whether the Doppler coefficient change rate is equal to or less than a predetermined threshold; a dividing means for dividing the processing block into a plurality of sub-blocks when the Doppler coefficient change rate is greater than the threshold value; a sample position calculation means for calculating sample point positions requiring interpolation for each of the sub-blocks based on the propagation delay; an interpolation processing means for executing an interpolation process for each of the sub-blocks based on the sample point positions; a delay processing means for executing a sample delay for each of the sub-blocks after the interpolation processing based on the propagation delay; A signal generating system comprising:

7. 1. A signal generation method for simulating a propagation delay and a frequency shift in a waveform by an information processing device, comprising: storing a propagation delay for each processing block, which is a unit of signal processing, for the waveform; calculating a Doppler coefficient change rate between successive processing blocks based on the propagation delay; determining whether the Doppler coefficient change rate is equal to or less than a predetermined threshold; if the Doppler coefficient variation is greater than the threshold, dividing the processing block into a plurality of sub-blocks; calculating sample point positions requiring interpolation for each of the sub-blocks based on the propagation delay; performing an interpolation process for each of the sub-blocks based on the sample point positions; performing a sample delay for each of the sub-blocks after the interpolation process based on the propagation delay; A signal generating method comprising:

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