JP2022130763A - Signal generator, signal generating system and signal generating method - Google Patents

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

The present invention relates to a signal generation device, a signal generation system, and a signal generation method for generating a signal simulating propagation delay and frequency shift.

2. Description of the Related Art Conventionally, there is known a signal generating apparatus for generating a signal simulating a wave propagation delay and a frequency shift caused by the Doppler effect in a simulator that simulates wave propagation from a sound source to a wave receiving point. In addition, although it is not a signal generation device, when the waves to be analyzed are radio waves, the ocean radar observation device that emits radio waves to the sea surface, measures the reflected waves, and observes oceanographic information such as ocean currents. (See Patent Document 1, for example).

The marine radar observation device disclosed in Patent Document 1 divides the observation range in the range direction into blocks for water level fluctuation noise generated by ships, obtains the regression curve of the flow in the divided blocks, and calculates from the regression curve Detects and corrects abnormal flux values based on deviation and standard deviation.

JP-A-11-83992

The ocean radar observation device disclosed in Patent Document 1 performs correction processing with a constant block length. When the technology disclosed in Patent Document 1 is applied to a signal generation device and the length of a processing block, which is a unit of signal processing, is fixed, if the Doppler coefficient changes significantly between blocks, continuity between processing blocks is lost. There is a possibility that the secured waveform cannot be simulated. This is because, for example, when the distance between the sound source and the wave receiving point is short, the Doppler coefficient varies greatly between consecutive blocks compared to when the distance between the sound source and the wave receiving point is long.

A signal generating apparatus according to the present invention is a signal generating apparatus that simulates propagation delay and frequency shift for a waveform, and storage means for storing the propagation delay for each processing block, which is a unit of signal processing, for the waveform. , coefficient change degree calculation means for calculating the Doppler coefficient change degree between successive processing blocks based on the propagation delay, and determination means for determining whether the Doppler coefficient change degree is equal to or less than a predetermined threshold value. , dividing means for dividing a processing block into a plurality of sub-blocks when the degree of Doppler coefficient change is greater than a threshold; and sample position calculating means for calculating sample point positions requiring interpolation for each sub-block based on propagation delays. and interpolation processing means for executing interpolation processing for each sub-block based on the sample point position, and delay processing means for executing sample delay for each sub-block after interpolation processing based on the propagation delay. is.

A signal generation system according to the present invention is a signal generation system that simulates propagation delays and frequency shifts for waveforms, and storage means for storing propagation delays for each processing block, which is a unit of signal processing, for waveforms. , coefficient change degree calculation means for calculating the Doppler coefficient change degree between successive processing blocks based on the propagation delay, and determination means for determining whether the Doppler coefficient change degree is equal to or less than a predetermined threshold value. , dividing means for dividing a processing block into a plurality of sub-blocks when the degree of Doppler coefficient change is greater than a threshold; and sample position calculating means for calculating sample point positions requiring interpolation for each sub-block based on propagation delays. and interpolation processing means for executing interpolation processing for each sub-block based on the sample point position, and delay processing means for executing sample delay for each sub-block after interpolation processing based on the propagation delay. is.

A signal generation method according to the present invention is a signal generation method by an information processing apparatus that simulates a propagation delay and a frequency shift for a waveform. calculating a Doppler coefficient variation between successive processing blocks based on the propagation delay; determining whether the Doppler coefficient variation is less than or equal to a predetermined threshold; dividing the processing block into a plurality of sub-blocks when the degree of coefficient change is greater than the threshold; calculating sample point positions requiring interpolation for each sub-block based on propagation delay; and performing sample delay for each sub-block after interpolation based on the propagation delay.

According to the present invention, threshold determination is performed with respect to the Doppler coefficient change degree. Estimate the waveform by automatically dividing it into long sub-blocks. Therefore, even if there is a large change in the Doppler coefficient between successive processing blocks, it is possible to simulate a waveform that ensures continuity.

FIG. 4 is a schematic diagram showing an example of temporal changes of a position vector of a sound source and a position vector of a receiving point; FIG. 5 is a schematic diagram for explaining a first comparative example; It is a schematic diagram for demonstrating the 2nd comparative example. FIG. 11 is a schematic diagram for explaining a third comparative example; 1 is a diagram showing a configuration example of a signal generating device according to Embodiment 1; FIG. 6 is a functional block diagram showing a configuration example of a control unit shown in FIG. 5; FIG. FIG. 7 is a functional block diagram showing one configuration example of a dividing unit shown in FIG. 6; 4 is a flow chart showing an example of the operation procedure of the signal generating device according to Embodiment 1; 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; FIG. FIG. 9 is a flow chart showing an example of an operating procedure of a dividing means in the process of step S108 shown in FIG. 8; FIG. 1 is a block diagram showing a configuration example of a signal generation system according to Embodiment 1; FIG.

Embodiment 1.
In the first embodiment, the signal generator is a simulator that simulates wave propagation and generates a signal simulating frequency shift due to propagation delay and Doppler effect. Before describing the signal generation device of the first embodiment, the wave to be simulated by the signal generation device will be described by taking sound propagation as an example. Since it is difficult to use vector notation (boldface notation, attachment of an arrow above the character, etc.) for Greek or Roman letters that indicate various parameters in the text, the vector notation in the text will be omitted below.

FIG. 1 is a schematic diagram showing an example of temporal 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 the situation in which the position vector ps of the sound source and the position vector pr of the receiving point change over time as one or both of the sound source and the receiving point move. That is, when generating a pseudo signal that simulates a received wave signal at a wave receiving point through which sound radiated from a sound source propagates, a signal that is frequency-shifted due to propagation delay and the Doppler effect is simulated.

Next, in order to facilitate understanding of the signal generation method by the signal generation device of the first embodiment, three comparative examples will be described as methods of simulating a signal that is frequency-shifted due to propagation delay and the Doppler effect.

First, a first comparative example will be described with reference to FIG. A first comparative example is a phase integration method. FIG. 2 is a schematic diagram for explaining a first comparative example. Assume that the sound source signal s(n) is represented by Equation (1).

In equation (1), f is the signal frequency [Hz], φ ₀ is the initial phase [rad], _fs is the sampling frequency [Hz], and n is the discrete time index. As shown in FIG. 2, if the propagation delay time in processing block 1 is τ ₁ [s] and the Doppler coefficient is d ₁ , and the propagation delay time in subsequent processing block 2 is τ ₂ [s] and the Doppler coefficient is d ₂ do. The processing block is, for example, a signal that is cut out in a predetermined time range as a unit of signal processing from the sound source signal time waveform that indicates the time change of the waveform of the sound source signal. The Doppler coefficient is the rate at which the frequency changes due to the presence of relative velocities between the source and receiving points, and is shown in Equation (2).

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

where the initial phase φ ₁ of processing block 2 is the trailing phase of processing block 1 calculated in equation (5). The equations extended to processing block l are shown in equations (6) and (7).

In the phase integration method, the Doppler coefficient appears 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 the processing block becomes the initial phase of the next processing block. It is a method.

Next, a second comparative example will be described with reference to FIG. A second comparative example is a sample update method. FIG. 3 is a schematic diagram for explaining a second comparative example. As shown in FIG. 3, in the sample updating method, a waveform consisting of a sequence given a propagation delay that can change for each sample of the sound source waveform is obtained. For example, by convoluting the sound source signal s(n) with a delay filter hn=[hn(0), hn(1), . x(n) is obtained as shown in equation (8).

Next, a third comparative example will be described with reference to FIG. A third comparative example is a processing block expansion/contraction method. FIG. 4 is a schematic diagram for explaining a 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 , if τ _l+1 −τ _l ≠0, then the waveform is For continuity, the end of processing block l is considered equal to a propagation delay of τ _l+1 . That is, by expanding or contracting the time length of the processing block l from N _block [samples] to N _block + (τ _l+1 - τ _l )*f _s [samples], the continuity of the waveform can be maintained. Also, the expansion and contraction of the waveform is equivalent to frequency shifting by the Doppler coefficient d shown in Equation (9).

The waveform x(n) after expansion and contraction of the processing block corresponds to the Doppler coefficient d, and the sound source waveform s(n)={s(0), s(1), . . . , s(N _block −1), s(N _block )} is obtained by resampling as shown in equation (10).

Note that s(d), s(2d), .

Although three comparative examples have been described so far, each comparative example 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, applicable signals are limited to narrowband signals. Also, the length of the output processing block and the length of the input processing block are the same, and these lengths are constant. Therefore, there is a problem that the propagation delay of the signal of the processing block 1 appears only in the Doppler coefficient and is not taken into consideration as the reception time.

The sample update method, which is the second comparative example, can simulate accurate propagation delay and frequency shift for arbitrary signal waveforms by convoluting a delay filter that expresses propagation delay that changes for each sample. is. Although the propagation delay is reflected in the reception time, there is a problem that the calculation cost is high because the propagation delay is calculated for each sample.

The processing block expansion/contraction method, which is the third comparative example, can simulate the frequency shift in block units by expanding/contracting the signal waveform in the processing block. However, unlike the sample update method, the Doppler coefficient is uniform within the processing block, so it is not suitable when the Doppler coefficient varies greatly within the processing block. In this case, it can be handled by setting the processing block length so short that the Doppler coefficient can be regarded as constant within the processing block. .

The signal generator according to the first embodiment solves these problems. The configuration of the signal generation device according to the first embodiment will be described. FIG. 5 is a diagram illustrating a configuration example of a signal generating device according to Embodiment 1. FIG.

The signal generation device 1 is an information processing device such as a computer. As shown in FIG. 5 , the signal generation device 1 has an input section 2 , a storage section 3 , a control section 4 and an output section 5 . The storage unit 3 is, for example, an HDD (Hard Disk Drive) device. The output unit 5 is, for example, a display device. The control unit 4 has a memory 11 that stores programs and a CPU (Central Processing Unit) 12 that executes processes according to the programs. The memory 11 is, for example, a non-volatile memory such as flash memory. The input unit 2 receives a sound source signal time waveform that serves as a reference for the simulated signal.

FIG. 6 is a functional block diagram showing one configuration example of the control unit shown in FIG. The control unit 4 includes processing block update means 21 , coefficient variation calculation means 22 , determination means 23 , sample position calculation means 31 , interpolation processing means 32 and delay processing means 33 . The control unit 4 also has a dividing unit 41 and a subblock updating unit 43 . By executing the program by the CPU 12, the processing block updating means 21, the coefficient variation calculating means 22, the determining means 23, the sample position calculating means 31, the interpolation processing means 32, the delay processing means 33, the dividing means 41, and the sub-block updating means 43 is configured.

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 sound source waveform block memory 51 is storage means for storing the sound source signal time waveform for each processing block. The propagation delay memory 52 is storage means for storing propagation delays for each processing block. The propagation delay memory 52 stores the block length of the processing block and the propagation delay as a set corresponding to the block index.

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 section 3 by the dividing means 41 . The excitation waveform sub-block memory 54 stores the excitation signal time waveform of the time range corresponding to each sub-block divided by the dividing means 41 . The propagation delay sub-memory 55 stores the block length and propagation delay of sub-blocks as a set corresponding to the sub-block index of the number of sub-blocks. A sub-block is one time range when a processing block is divided into multiple pieces.

The processing block updating means 21 receives the excitation signal time waveform and the block index as inputs, and stores the excitation signal time waveform in the range of the processing blocks to be subjected to propagation delay and frequency shift in the excitation waveform block memory 51 . In the first embodiment, the case where the propagation delay memory 52 stores the propagation delay for each processing block will be described. It may also function as a propagation delay calculation means for calculating.

The coefficient change degree calculation means 22 reads 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 sends the Doppler coefficient change degree to the determination means 23. Output. The determining means 23 receives the Doppler coefficient change degree and determines whether or not 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 the information of the determination result.

When the Doppler coefficient change degree is larger than the threshold, the division unit 41 reads the propagation delay at the time corresponding to the block index from the propagation delay memory 52, receives the read propagation delay and the Doppler coefficient change degree as inputs, and interpolates the propagation. The delay and block length of the sub-block are determined and stored in the propagation delay sub-memory 55 .

The configuration of the dividing means 41 will be described with reference to FIG. FIG. 7 is a functional block diagram showing one configuration example of the dividing means shown in FIG. The dividing means 41 has block length calculating means 141 and propagation delay interpolation processing means 142 .

The block length calculation means 141 refers to the propagation delay memory 52 to read the propagation delay at the time corresponding to the block index, receives the read propagation delay and the Doppler coefficient variation, and divides the processing block into a plurality of sub-blocks. and outputs information on the number of sub-blocks and the block length 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 the propagation delay at the time corresponding to the block index, receives the read propagation delay and block length as inputs, performs propagation delay interpolation processing, and performs propagation delay interpolation processing. The information stored in the memory 55 is updated.

The sub-block updating means 43 shown in FIG. 6 reads the block length of the sub-block corresponding to the sub-block index from the propagation delay sub-memory 55, and retrieves the excitation signal time waveform in the time range corresponding to the block index from the excitation waveform block memory 51. read out. The sub-block update means 43 receives the read block length, excitation signal time waveform, and sub-block index, and stores the excitation signal time waveform in the time range corresponding to the sub-block index in the excitation waveform sub-block memory 54 .

When the Doppler coefficient change degree is equal to or less than the threshold value, the sample position calculation means 31 reads 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, and interpolates the sample point position information. Output to the processing means 32 . When the Doppler coefficient variation is greater than the threshold, the sample position calculation means 31 reads the propagation delay corresponding to the sub-block index from the propagation delay sub-memory 55, receives the read propagation delay and block length as inputs, and calculates the sample point position. It calculates and outputs the information of the sample point position to the interpolation processing means 32 .

The interpolation processing means 32 receives as inputs the excitation signal time waveform of the processing block stored in the excitation waveform block memory 51 and the sample point positions, generates a signal expressing the phase delay and frequency shift, and outputs the signal to the delay processing means 33 . output to The interpolation processing means 32 reads out the excitation signal time waveform in the time range corresponding to the sub-block index from the excitation waveform sub-block memory 54, receives the read excitation signal time waveform and the sample point position as inputs, and performs phase delay and frequency shift. The expressed signal is generated and output to the delay processing means 33 .

The delay processing means 33 reads the propagation delay at the time corresponding to the block index from the propagation delay memory 52, receives the read propagation delay and the signal expressing the phase delay and frequency shift, and after the propagation delay and frequency shift is generated and output to the output unit 5 shown in FIG. The delay processing means 33 reads the propagation delay corresponding to the sub-block index from the propagation delay sub-memory 55, receives the read propagation delay and the signal expressing the phase delay and frequency shift as inputs, and after the propagation delay and frequency shift is generated and output to the output unit 5 shown in FIG.

In the first embodiment, the excitation waveform block memory 51, the propagation delay memory 52 and the sub-memory 53 are provided in the storage unit 3 as shown in FIG. 6. However, these memories are shown in FIG. It may be provided in the memory 11 shown.

Next, the operation of the signal generator 1 according to the first embodiment will be described. 8 is a flowchart illustrating an example of an operation procedure of the signal generation device according to Embodiment 1. FIG. 9 is a diagram showing an example of information stored in the propagation delay memory and propagation delay sub-memory shown in FIG. 6. FIG.

Here, taking sound propagation as an example, consider a case in which the signal generating apparatus 1 generates a pseudo signal that simulates the received waveform at the wave receiving point in a situation where the position vectors of the sound source and the wave receiving point change over time. As shown in the upper part of FIG. 9, it is assumed that the propagation delay memory 52 stores the propagation delay at the time corresponding to each processing block.

As the sound source signal time waveform, the 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 updating means 21 receives the sound source time signal s(n) as an input, and stores the time waveform s(n _l ) of the set n _l of time indices corresponding to the block index l in the sound source waveform block memory 51 . Let At step S102, the processing blocks are sequentially updated corresponding to the block index l. A time waveform _nl is shown in Equation (12). Here, the block index l is the index of the processing block, and L is the total number of processing blocks.

Propagation delays τ ₁ , τ ₁₊₁ , τ ₁₊₂ required in the processing after step S102 are based on block index _l from τ={τ ₁ , τ ₂ , . is referred to. In step S103, the coefficient change degree calculator 22 inputs the propagation delays τ _l , τ _l+1 , and τ _l+2 into the following equation (13) to calculate the Doppler coefficient change degree Δd _l .

In step S104, the determining means 23 compares the Doppler variation |Δd _l | with a predetermined threshold value δ, and determines whether the Doppler variation |Δd _l | is equal to or less than the threshold value δ. The threshold value δ is set to a large value close to 0.01 when emphasizing the calculation cost, and is set to a small value close to 0 when emphasizing the degree of simulation. When the Doppler variation |Δd _l | is equal to or smaller than the threshold 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 variation calculating means 22 estimates the expansion/contraction rate of a processing block using the propagation delay difference between consecutive processing blocks without using information on the relative velocities of the sound source and the wave receiving point.

In step S105, the sample position calculation means 31 expands or contracts the entire processing block at the estimated expansion/contraction rate, obtains the corresponding sample points by interpolation, and calculates the positions of the sample points after propagation delay and frequency shift. Specifically, the sample position calculation means 31 obtains a set n _l ' of time indexes to be output to the interpolation processing means 32 as follows. A set n _l ' of time indices is shown in Equation (14).

In Equation (14), N _block ' is the number of samples after waveform expansion/contraction of the processing block l with the number of samples N _block . _dl is the Doppler coefficient corresponding to the block index and is shown in the second term of equation (13). φ _l is the initial sample shift position expressed in equation (15).

In Expression (15), the symbol floor [·] represents an operation of rounding down decimal places. %x represents the remainder of division by x, and is a process for making {1}%1=0 when { } becomes 1.

If it is a fractional sample delay, the original start time of the block is _shifted by a fraction of the integer sample delay floor[τ _l f _s ] - floor[ _{τ l} f _s ]. The waveform is sampled at the sample time {1-(τ _l f _s -floor[τ _l f _s ])} of the original time scale, but if the Doppler effect is occurring, it will start at a factor multiplication. The time is off.

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 the series of discrete points of the waveform. Specifically, the interpolation processing means 32 obtains a spline function f(n) (lN _block ≤ n ≤ (l+1)N _block ) which is a continuous function by spline interpolation from the discrete signal of the original waveform s (n=n _l ). Ask for Then, the interpolation processing means 32 substitutes the time index set n _l ' input from the sample position calculation means 31 into the spline function to obtain the waveform s'(n) after the fractional sample delay and frequency shift. Waveform s'(n) is shown in equation (16).

In step S107, the delay processing means 33 shifts the waveform by the sample delay floor [τ _{lf s} ] as shown in the following equation (17).

On the other hand, if the Doppler change degree |Δd _l | is greater than the threshold value δ as a result of the determination in step S104, 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 fine sub-blocks that can follow the change in the Doppler coefficient, and performs propagation delay and frequency shift on a sub-block basis. Perform processing to obtain Here, let a=|Δd _l |/δ>1 be the ratio between the Doppler variation |Δd _l | and the threshold value δ.

In step S108, the dividing unit 41 divides the processing block into floor[a]+1 sub-blocks within the block index l, as shown in FIG. As a result, the sub-block becomes (N _block /floor[a]+1) samples obtained by equally dividing the block length of the processing block. The dividing means 41 obtains the propagation delay from the Doppler coefficient obtained by interpolating between consecutive sub-blocks. The operation of the dividing means 41 will be described later in detail.

In step S109, the sub-block updating means 43 receives the sound source time signal s(n) as input, and converts the time waveform s(n _l, ) of the time index set n _l, corresponding to the sub-block index l′ to the sound source waveform sub- It is stored in block memory 54 . In step S109, the subblocks are sequentially updated corresponding to the subblock index l'. The sound source time signal s(n) is shown in Equation (18), and the set of time indices nl _, is shown in Equation (19).

In step S110, the sample position calculation unit 31 performs arithmetic processing similar to the processing described in step S105, with the sub-block as the processing target instead of the processing block. Specifically, the sample position calculation means 31 obtains a set n _l, ' of time indexes to be output to the interpolation processing means 32 . A set n _l, ' of time indices is shown in Equation (20).

In Equation (20), N _block ″ is the number of samples after waveform expansion/contraction of sub-block l′ of the number of samples (N _block /floor[a]+1). _dl, is the Doppler coefficient corresponding to the sub-block index. φ _l, is the initial sample shift position represented by the following equation (21).

In step S111, the interpolation processing means 32 performs waveform interpolation processing as follows. The interpolation processing means 32 obtains a spline function f(n) (lN _block + (l'-1) (N _block /floor[a]) which is a continuous function by spline interpolation from the discrete signal of the original waveform s(n _l, ). +1)≦n<lN _block +l′(N _block /floor[a]+1)). Then, the interpolation processing means 32 substitutes the time index set n _l, ' input from the sample position calculation means 31 into the spline function to obtain the waveform s'(n) after the fractional sample delay and frequency shift. Waveform s'(n) is shown in equation (22).

In step S112, the delay processing means 33 shifts the waveform by the sample delay floor [τ _l, 'f _s ] as shown in the following equation (23).

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

Upon receiving the block index information from the delay processing unit 33, the processing block updating unit 21 updates the block index (step S114), and returns to step S102. The control unit 4 repeats steps S102 to S114 until the block index l=1, . be done. In this way, a signal is generated that simulates the propagation delay and frequency shift at the receiving point while ensuring the continuity of the waveform.

Next, the operation of the dividing means 41 in the process of step S108 shown in FIG. 8 will be described with reference to FIGS. 7, 9 and 10. FIG. FIG. 10 is a flow chart showing an example of the operation procedure of the dividing means in the process of step S108 shown in FIG.

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

Next, the propagation delay interpolation processing means 142 successively obtains propagation delays from the Doppler coefficients obtained by interpolation as described above, using Equation (25) obtained by modifying Equation (9) (step S202). .

Here, the propagation delay interpolation processing means 142 uses τ ₁ ′=τ ₁ as the initial sub-block propagation delay. The propagation delay interpolation processing means 142 obtains information to be stored in the propagation delay sub-memory 55 by solving for l′=1, 2, . . . , floor[a]. Information stored in the propagation delay sub-memory 55 is shown in the lower part of FIG.

The signal generation device 1 of the first embodiment includes storage means for storing propagation delay for each processing block, which is a unit of signal processing, for a waveform, coefficient variation calculation means, determination means, division means, It has sample position calculation means, interpolation processing means, and delay processing means. The storage means is, for example, the propagation delay memory 52 . The coefficient change degree calculation means 22 calculates the Doppler coefficient change degree between consecutive processing blocks based on the propagation delay. The determining means 23 determines whether or not the Doppler coefficient variation is equal to or less than a predetermined threshold. The dividing means 41 divides the processing block into a plurality of sub-blocks when the Doppler coefficient variation is larger than the threshold. The sample position calculation means 31 calculates sample point positions requiring interpolation for each sub-block based on the propagation delay. The interpolation processing means 32 executes interpolation processing for each sub-block based on the sample point positions. The delay processing means 33 executes sample delay for each sub-block after interpolation processing based on the propagation delay.

According to the first embodiment, threshold determination is performed with respect to the Doppler coefficient change degree. Waveforms are estimated by automatically dividing into sub-blocks with finer block lengths. When the sound source is farther than the receiving point and the Doppler coefficient changes slowly, processing is performed in units of processing blocks, so the calculation cost of necessary operations can be reduced. In addition, when the receiving point is close to the sound source, such as near 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. , not only the phase continuity of the waveform, but also the continuity of the Doppler variation can be simulated. In the first embodiment, by applying the block expansion/contraction method with an adaptive block length estimated corresponding to the change rate of the Doppler coefficient, even if the Doppler coefficient changes greatly between processing blocks, the simulated signal The continuity of the waveform can be ensured, and the calculation cost can be reduced.

In the first comparative example, the length of the processing block to be input and the length of the processing block to be output are the same and constant. A stretching scheme can be applied to estimate the simulated signal.

In the second comparative example, the propagation delay is expressed for each sample and the delay filter is convoluted to expand or contract the waveform, which increases the calculation cost. On the other hand, in the first embodiment, when the Doppler coefficient change degree is equal to or less than the threshold value, the computational process is performed in units of processing blocks using the propagation delay of each processing block. Therefore, it is possible to reduce the calculation cost. can be done.

In the third comparative example, since the Doppler coefficient is uniform within the processing block, the accuracy of the simulated signal becomes low when the Doppler coefficient varies greatly within the processing block. On the other hand, in the first embodiment, estimation is performed by applying the block expansion/contraction method with an adaptive block length corresponding to the rate of change of the Doppler coefficient. can be improved.

(Description of usage form of the first embodiment)
In the first embodiment described above, the propagation of sound has been described as an example, but if it is a wave, it can be applied to radio waves used for radar, for example.

In the first embodiment described above, the propagation delay memory 52 stores the propagation delay time information of all processing blocks. good. Specifically, it is the delay time of each of processing block l and processing blocks l+1 and l+2 following processing block l. The propagation delay memory 52 holds the propagation delays of the processing block l and the processing block l+1, and the newly calculated propagation delay of the processing block l+2. After the process 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 process of step S102, Preserve propagation delay. 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 updating means 21 may manage the information stored in the propagation delay memory 52 as described above.

As for the waveform interpolation processing in steps S106 and S111 in FIG. 8, an example of spline interpolation that always passes sample data points, has continuous primary and secondary differentials at block boundary points, and easily outputs a value at an arbitrary position is taken as an example. , but the interpolation method is not limited to this. Linear interpolation, Lagrangian interpolation, or the like may be used as long as it is an interpolation process that can output a value at an arbitrary interpolation position, taking into consideration the amount of calculation and the effect on subsequent signal processing.

In the first embodiment described above, the case of a single information processing device has been described, but the signal generation system may have a plurality of information processing devices. 11 is a block diagram showing a configuration example of a signal generation system according to Embodiment 1. FIG. The signal generation system 10 has information processing devices 101-103. Information processing apparatuses 101 to 103 are connected to each other via a network 200 such as the Internet. The information processing apparatus 101 has the storage unit 3 shown in FIG. 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 section 4 shown in FIG. The information processing device 103 has the processing block updating means 21, the coefficient variation calculating means 22, the determining means 23, the dividing means 41 and the sub-block updating means 43 of the control section 4 shown in FIG. In the case of the configuration example shown in FIG. 11, the arithmetic processing necessary for executing the signal generation method of the first embodiment is shared among the plurality of information processing apparatuses 101 to 103, so that the speed of the arithmetic processing can be increased. can.

1 signal generation device 2 input unit 3 storage unit 4 control unit 5 output unit 10 signal generation system 11 memory 12 CPU
21 processing block updating means 22 coefficient variation calculating means 23 judging means 31 sample position calculating means 32 interpolation processing means 33 delay processing means 41 dividing means 43 sub-block updating means 51 excitation waveform block memory 52 propagation delay memory 53 sub-memory 54 excitation waveform Sub-block memory 55 Propagation delay sub-memory 101-103 Information processor 141 Block length calculation means 142 Propagation delay interpolation processing means 200 Network

Claims (7)

A signal generator that simulates propagation delays and frequency shifts for waveforms, comprising:
storage means for storing a propagation delay for each processing block, which is a unit of signal processing, for the waveform;
Coefficient change degree calculation means for calculating the Doppler coefficient change degree between the consecutive processing blocks based on the propagation delay;
determining means for determining whether or not the Doppler coefficient variation is equal to or less than a predetermined threshold;
dividing means for dividing the processing block into a plurality of sub-blocks when the Doppler coefficient variation is greater than the threshold;
sample position calculation means for calculating sample point positions requiring interpolation for each of the sub-blocks based on the propagation delay;
interpolation processing means for executing interpolation processing for each of the sub-blocks based on the sample point positions;
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 generator having a The coefficient change degree calculation means is
estimating the expansion/contraction ratio of the sub-block using the propagation delay difference between the consecutive sub-blocks;
A signal generation device according to claim 1 . The dividing means is
interpolating the propagation delay such that the Doppler coefficient varies linearly between successive sub-blocks;
3. A signal generator according to claim 1 or 2. The interpolation processing means is
simulating a frequency shift for a waveform of an arbitrary frequency by resampling the sub-blocks according to the expansion/contraction ratio estimated by the sample position calculation means;
3. A signal generating device according to claim 2. The interpolation processing means is
estimating an interpolation function that is a continuous signal from the series of discrete points of the waveform, and inputting the values of the sample point positions into the interpolation function to output the value of the position between the discrete points;
A signal generator according to any one of claims 1 to 4. A signal generation system that simulates propagation delays and frequency shifts for waveforms, comprising:
storage means for storing a propagation delay for each processing block, which is a unit of signal processing, for the waveform;
Coefficient change degree calculation means for calculating the Doppler coefficient change degree between the consecutive processing blocks based on the propagation delay;
Determination means for determining whether the Doppler coefficient variation is equal to or less than a predetermined threshold;
dividing means for dividing the processing block into a plurality of sub-blocks when the Doppler coefficient variation is greater than the threshold;
sample position calculation means for calculating sample point positions requiring interpolation for each of the sub-blocks based on the propagation delay;
interpolation processing means for executing interpolation processing for each of the sub-blocks based on the sample point positions;
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 generation system having A signal generation method by an information processing device that simulates propagation delay and frequency shift for a waveform,
storing a propagation delay for each processing block, which is a unit of signal processing, for the waveform;
calculating a Doppler coefficient variation between successive processing blocks based on the propagation delay;
determining whether the Doppler coefficient variation is equal to or less than a predetermined threshold;
dividing the processing block into a plurality of sub-blocks if the Doppler coefficient gradient is greater than the threshold;
calculating sample point positions requiring interpolation for each of the sub-blocks based on the propagation delay;
performing interpolation processing for each of the sub-blocks based on the sample point positions;
performing a sample delay for each of the interpolated sub-blocks based on the propagation delay;
A signal generation method comprising:

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