Signal processing device and measurement device
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-04
- Publication Date
- 2026-08-13
Smart Images
Figure JP2026004011_13082026_PF_FP_ABST
Abstract
Description
Signal processing device and measuring device
[0001] The present disclosure relates to a signal processing device and a measuring device.
[0002] "Positioning and ranging technology" is an essential technology in each industry. In industries such as automobiles, aerospace, logistics, construction civil engineering, communications, and agriculture, positioning and ranging technologies (GPS, radar, collision prevention ultrasonic sensors, LiDAR, etc.) using radio waves, sound, light, etc. are utilized. Positioning and ranging technology supports safety, efficiency, and reliability in each industry, and the essential factor here is the accuracy of the positioning and ranging.
[0003] The key factor affecting the "accuracy" of positioning and ranging technology lies in the measurement of the "propagation time". These technologies achieve positioning and ranging by measuring the time (propagation time) it takes for the transmission signal to propagate from the transmitter to the receiver. That is, if the propagation time can be accurately measured, the accuracy of positioning and ranging will also be improved.
[0004] When measuring the propagation time with high precision, "noise" has an impact. When a signal with noise superimposed is measured by the receiver during positioning and ranging, an error occurs in the propagation time measurement. To avoid this, it is important that the signal strength of the measurement signal is sufficiently large compared to the noise in the received signal, which is called the signal-to-noise ratio (SNR: Signal to Noise Ratio).
[0005] Therefore, conventionally, efforts have been made to improve the SNR of propagation time measurement. (There are) (1) a simple method of increasing the output of the transmitter, (2) a method using pulse compression, (3) a method using synchronous detection, etc. have been proposed. Similar to "echo", in a poor "multipath environment" where there are paths of reflected waves in addition to the direct wave, among these three methods, (1) and (3) are not solutions, and for example, the method using (2) pulse compression as described in Patent Document 1 is more frequently used.
[0006] (2) Pulse compression is a signal processing technique for improving resolution and SNR. By using a long, modulated pulse for transmission to ensure average power, the pulse length can be compressed during reception to improve distance resolution and SNR. The "resolution" and "SNR" improved by pulse compression are determined by two factors in the modulation described above: (i) bandwidth and (ii) pulse length. This relationship will be explained later using mathematical formulas.
[0007] International Publication No. 2018 / 131099
[0008] The "resolution" of pulse compression depends on (i) the bandwidth of the transmitted waveform. In pulse compression, if the wave speed is c [m / s] and the bandwidth is Δf [Hz], then: This can be calculated as follows: A wider bandwidth results in higher resolution, while a narrower bandwidth results in lower resolution.
[0009] On the other hand, the "SNR" of pulse compression depends on both (i) bandwidth and (ii) pulse length. The power of the received signal modulated in pulse compression, when the pulse length is T [s], is compared to the power before pulse compression. It can be thought of as becoming twice as large. From this, it can be seen that the longer the pulse length T [s] and the wider the bandwidth Δf [Hz], the greater the SNR improvement.
[0010] These two relationships indicate the need for pulse compression technology that does not depend on the bottleneck "(i) bandwidth". As shown in the relationships, in conventional technology, both resolution and SNR depend on the bandwidth of the transmitted waveform. If the bandwidth is increased, both resolution and SNR will improve, but in return, the bandwidth of the propagation path will be monopolized, hindering the use of other communications. Furthermore, in positioning and ranging using sound or ultrasound, the bandwidth is often limited by the performance of the speaker and transducer, creating a dilemma where resolution cannot be increased.
[0011] This disclosure has been made in view of the above-mentioned problems, and aims to provide a technology that can improve the resolution and SNR of pulse compression without monopolizing bandwidth, or even when bandwidth is limited.
[0012] This disclosure solves these problems by adding a process to increase bandwidth through post-processing. This disclosure is characterized by virtually multiplying the bandwidth of the transmitted and received signals in signal processing without increasing the actual bandwidth in the propagation path or delay line. In other words, the discloser arrived at this disclosure based on the technical idea that in pulse compression, the bandwidth of the transmitted waveform does not determine the "resolution" and "SNR," but rather that virtually multiplying it can be effective.
[0013] A signal processing device according to one aspect of the present disclosure is a signal processing device that processes a signal using pulse compression, comprising: a conversion unit that performs a Fourier transform on an input signal to generate a converted signal; a bandwidth multiplier unit that adds a signal bandwidth that was not included in the converted signal as a multiplied frequency component to the converted signal to generate an added signal; and an inverse transform unit that performs an inverse Fourier transform on the added signal to generate a processed signal.
[0014] Furthermore, a measuring device according to one aspect of this disclosure comprises a transmitter that transmits a signal, a receiver that receives the signal transmitted from the transmitter, and the signal processing device described above.
[0015] According to this disclosure, the resolution and SNR of pulse compression can be improved even without monopolizing bandwidth, or even when bandwidth is limited.
[0016] This is a block diagram showing an example of the schematic configuration of a measuring device according to Embodiments 1 to 5 of this disclosure. This is a block diagram showing an example of the schematic configuration of a signal processing device included in the measuring device. This is a block diagram showing an example of the functional configuration of a signal processing unit included in a signal processing device according to Embodiment 1. This is a diagram illustrating some of the processes performed by a signal processing device according to Embodiment 1. This is a graph showing the results of a simulation performed using a signal processing device according to Embodiment 1. This is a graph showing how much estimation error occurs when noise is intentionally superimposed. This is a block diagram showing an example of the functional configuration of a signal processing unit included in a signal processing device according to Embodiment 2 of this disclosure. This is a block diagram showing an example of the functional configuration of a signal processing unit included in a signal processing device according to Embodiment 3 of this disclosure. This is a block diagram showing an example of the functional configuration of a signal processing unit included in a signal processing device according to Embodiment 4 of this disclosure. This is a block diagram showing an example of the functional configuration of a signal processing unit included in a signal processing device according to Embodiment 5 of this disclosure.
[0017] <Embodiment 1> Hereinafter, Embodiment 1 of the present disclosure will be described in detail.
[0018] [Outline Configuration of Measurement Device 100] First, the measurement device 100 according to Embodiment 1 of this disclosure will be described. Figure 1 is a block diagram showing an example of the measurement device 100 according to Embodiment 1. As shown in Figure 1, the measurement device 100 includes a transmitter 1, a receiver 2, and a signal processing device 3. Note that one measurement device 100 may have only one transmitter 1, or it may have multiple transmitters 1 for position estimation. Similarly, one measurement device 100 may have only one receiver 2, or it may have multiple receivers 2 for position estimation. Incidentally, in Embodiment 1 of this disclosure, there is a transmitter 1 and a receiver 2, and the delay amount between them is measured as an example, but this disclosure may be used for measurements other than the transmitter 1 and receiver 2 (such as physical phenomena) as long as the measurement uses pulse compression. Furthermore, this disclosure determines waveform shifts, etc., and is not limited to positioning and distance measurement.
[0019] [Transmitter 1] Transmitter 1 transmits a signal suitable for pulse compression. A "signal suitable for pulse compression" may be, for example, a pseudo-random binary sequence (PRBS) modulated at the carrier frequency (BPSK: Binary Phase-Shift Keying, etc.), or it may transmit a comb signal or a chirp signal. Pseudo-random binary sequences include highly random M sequences, Gold sequences, etc. There is no fixed length for these signals, but it is desirable that the signal length be longer than the impulse response in the propagation path from transmitter 1 to receiver 2. For example, when using sound or ultrasound as the signal, it is desirable to use a signal length longer than the reverberation time of the space. Transmitter 1 may be configured to transmit a signal once per measurement, or it may be configured to transmit a signal multiple times (2 times, 4 times, 8 times, etc.) and then rest (perform intermittent operation). Transmitter 1 may also be configured to transmit a signal continuously without interruption during a single measurement. Of these, the preferred method is to repeatedly transmit the signal multiple times for each measurement. The signal transmitted by transmitter 1 may be radio waves, sound, ultrasound, light, etc. That is, the transmitting unit of transmitter 1 can be composed of an antenna, speaker, transducer, light source, etc. (not shown). When transmitter 1 transmits a signal to receiver 2, it supplies the signal as the first signal x(t) to signal processing device 3.
[0020] [Receiver 2] Receiver 2 is a device that receives signals transmitted from transmitter 1. That is, the receiving section of receiver 2 can be configured with an antenna, microphone, transducer, light receiving sensor, etc. (not shown) depending on the signal (radio waves, sound, ultrasound, light, etc.) transmitted from transmitter 1. If both receiver 2 and transmitter 1 use an antenna or transducer, the same antenna or transducer may be used for both receiver 2 and transmitter 1. Transmitter 1 and receiver 2 may also be arranged to measure round-trip propagation to an uninstructed reflector. Receiver 2 may also be integrated with transmitter 1. Receiver 2 supplies the signal received from transmitter 1 as a second signal y(t) to signal processing device 3.
[0021] [Signal Processing Device 3] The signal processing device 3 is a device that processes signals using pulse compression. Specifically, the signal processing device 3 calculates the signal delay amount (for example, the propagation time of the signal from the transmitter 1 to the receiver 2, the waveform difference between the first signal x(t) and the second signal y(t), etc.). Details of this signal processing device 3 will be described later.
[0022] [Specific Configuration of Signal Processing Device 3] As a specific configuration of the signal processing device 3, the signal processing device 3 according to Embodiment 1 of this disclosure will be described. Figure 2 is a block diagram showing an example of the schematic configuration of the signal processing device 3 according to Embodiment 1, and Figure 3 is a block diagram showing an example of the specific configuration of the signal processing unit 31 provided in the signal processing device 3. As shown in the upper part of Figure 2, the signal processing device 3 includes a signal processing unit 31, a signal input unit 32, and a delay amount calculation unit 33.
[0023] [Signal Input Section 32] The signal input section 32 is the input section of the signal processing device 3. The first signal x(t) is input to the signal input section 32 from the transmitter 1. The first signal x(t) is a reference signal used as the basis for measuring the delay amount. The second signal y(t) is also input to the signal input section 32 from the receiver 2. The second signal y(t) is a measurement signal used to measure the delay amount. There are no fixed rules for the length of each signal, but it is desirable that the lengths of each signal are the same. Furthermore, it is desirable that the lengths of each signal are such that periodicity is ensured. For example, in the case of intermittent operation in which BPSK is repeatedly transmitted multiple times (2 times, 4 times, 8 times, etc.) and then rests, sampling the repeat signal from the second time onward will better ensure periodicity. Alternatively, periodicity may be ensured by using a time window (Hamming window, Hanning window, etc.).
[0024] [Signal Processing Unit 31] As shown in Figure 3, the signal processing unit 31 includes a conversion unit 311, a bandwidth multiplication unit 312, and an inverse conversion unit 313.
[0025] (Conversion Unit 311) The conversion unit 311 is responsible for the process of performing a Fourier transform on the input signal to generate the converted signal. The conversion unit 311 according to Embodiment 1 comprises a first conversion unit 311a, a second conversion unit 311b, and a cross-spectrum calculation unit 311c.
[0026] - First conversion unit 311a The first conversion unit 311a is responsible for the process of performing a Fourier transform (FT) on the input first signal x(t) to generate the first transformed signal X(f). The first conversion unit 311a may be configured to perform either an FFT (Fast Fourier Transform) or a DFT (Discrete Fourier Transform).
[0027] - Second conversion unit 311b The second conversion unit is responsible for the process of performing a Fourier transform on the input second signal y(t) to generate the second-transformed signal Y(f). The second conversion unit 311b may be configured to perform an FFT, DFT, or the like as the Fourier transform, similar to the first conversion unit 311a.
[0028] - Cross-spectrum calculation unit 311c The cross-spectrum calculation unit 311c according to Embodiment 1 calculates the cross-spectrum Cxy(f) of the first converted signal X(f) and the second converted signal Y(f) as the converted signal. The cross-spectrum Cxy(f) is, This can be expressed as follows. Note that the cross spectrum Cxy(f) is generally the Fourier transform of the cross-correlation. For this reason, the cross spectrum calculation unit 311c may be configured to calculate the cross spectrum Cxy(f) using the cross-correlation method. Alternatively, the cross spectrum calculation unit 311c may be composed of an analog circuit.
[0029] (Bandwidth Multiplier Unit 312) The Bandwidth Multiplier Unit 312 is responsible for the process of adding a signal band that was not included in the converted signal Cxy(f) as a multiplied frequency component to the converted signal Cxy(f) to generate the added signal Cxy'(f). The Bandwidth Multiplier Unit 312 according to Embodiment 1 generates the added signal Cxy'(f) by adding the multiplied frequency component retrospectively through modulation or mapping.
[0030] An example of bandwidth multiplication by the bandwidth multiplication unit 312 is shown in Figure 4. The upper part of Figure 4 is the frequency spectrum of a certain waveform, and the lower part of Figure 4 is the frequency spectrum of the waveform obtained by adding multiplied frequency components to the waveform in the upper part by defining a mapping function in frequency space. As shown in the lower part of Figure 4, the bandwidth multiplication unit 312 duplicates a converted signal Cxy(f) having a certain bandwidth (Figure 4 illustrates the case of 40 to 41.45 [kHz]) to a bandwidth n times that of the converted signal Cxy(f) (Figure 4 illustrates the case of 3 times: 120 to 124.35 [kHz]). As a result, the frequency bandwidth of the added signal Cxy'(f) is wider than the frequency bandwidth of the converted signal Cxy(f). In Figure 4, an example is shown where the bandwidth of the added signal Cxy'(f) is equivalent to twice the original bandwidth by duplicating each frequency bin of the converted signal Cxy(f) to a frequency bin three times its original value. However, the bandwidth to be amplified does not have to be twice as much. In other words, it may be duplicated to multiple frequency bands. Also, although it was duplicated to a frequency bin three times the original value, the duplicated signal does not have to be at three times the frequency. Furthermore, in Figure 4, an example is shown where the intensity of the added amplified frequency component is the same as the intensity of the converted signal Cxy(f). However, the intensity of the added amplified frequency component does not have to be the same as the intensity of the converted signal Cxy(f). Note that the addition of the amplified frequency component is performed retrospectively after the signal has been transmitted from transmitter 1 to receiver 2, so there is no change in the bandwidth used in the actual signal propagation path.
[0031] The phase θ2 of the multiplied frequency component in the bandwidth multiplication unit 312 can be formulated mathematically. Consider a component in the converted signal Cxy(f) that has a phase θ1 at a certain frequency f1. In this case, the relationship between the phase θ2 of the multiplied frequency component in the conversion from frequency f1 to the multiplied frequency f2 can be expressed as shown in Equation 4. Note that this relationship also holds when the absolute value of the phase θ2 of the multiplied frequency component is 2π (radians) or more. In other words, the phase θ2 of the multiplied frequency component may be treated as a value folded back (wrapped value) within the defined range of principal values (for example, from -π to π).
[0032] Here, when f2 / f1 is an odd number greater than or equal to 3, the calculation can be performed simply as shown in Equation 4. When the frequency is multiplied by an odd multiple of 3 or more according to Equation 4, at the moment when frequency f1 is an upward convex portion in the time waveform, frequency f2 is also an upward convex portion. Also, at the moment when frequency f1 is a downward convex portion in the time waveform, frequency f2 is also a downward convex portion. In the added signal Cxy'(f), these are superimposed. The effect of this disclosure is obtained when the convex portion of frequency f1 in the time waveform and the convex portion of the multiplied frequency f2 are aligned.
[0033] When f2 / f1 is an even number greater than or equal to 2, the sign of the correlation between the first signal x(t) and the second signal y(t) must be known. When the frequency is multiplied by an even multiple of 2 or more according to equation 4, at the moment when frequency f1 is an upward convex part in the time waveform, frequency f2 is also an upward convex part. On the other hand, at the moment when frequency f1 is a downward convex part in the time waveform, frequency f2 is an upward convex part. In this case, in the superimposed signal Cxy'(f), the upward convex part in the time waveform of frequency f1 and the upward convex part of the multiplied frequency f2 are aligned, and the effect of this disclosure is obtained for positive correlation. Furthermore, when π is added to θ2 calculated according to equation 4, at the moment when frequency f1 is a downward convex part in the time waveform, frequency f2 is also a downward convex part. On the other hand, at the moment when frequency f1 is an upward convex part in the time waveform, frequency f2 is also a downward convex part. In this case, in the superimposed additional signal Cxy'(f), the downward convex portion of the time waveform at frequency f1 and the downward convex portion at frequency f2 align, thus achieving the effect of the disclosure for negative correlation. According to the disclosure, the sign of the correlation between the first signal x(t) and the second signal y(t) can be determined by calculating the correlation, and can therefore be treated as generally known.
[0034] If f2 / f1 contains a decimal point, the number of times (N) the phase of frequency f1 cycles around 2π before the delay is known must be known. According to Equation 4, the phase of frequency f2 rotates at a rate f2 / f1 times faster than that of frequency f1 in the time waveform. In this case, if the phase of frequency f1 shifts by 2Nπ, the phase of frequency f2 shifts by (f2 / f1) × 2Nπ. When f2 / f1 contains a decimal point, this shift amount is not a multiple of 2π and causes a phase shift when it folds back within the defined principal value range. That is, when f2 / f1 contains a decimal point, the upper convex portion of the time waveform of f2 shifts by (1 - f2 / f1) × 2Nπ relative to frequency f1. Therefore, by adding (1 - f2 / f1) × 2Nπ to θ2 calculated according to Equation 4, the upper convex portions align, and the effect of this disclosure is obtained. This is shown in Equation 5. Although the case with positive correlation has been explained, according to this disclosure, even in the case of negative correlation, the effect of this disclosure can be obtained for negative correlation by adding π to the calculated θ² and performing the calculation so that the downward convex portion aligns. Furthermore, according to this disclosure, the number of times (N) that the phase of frequency f1 cycles 2π by the delay amount can be treated as generally known, based on the approximate delay amount obtained from the correlation between the first signal x(t) and the second signal y(t) that has been determined in advance.
[0035] Therefore, this disclosure is implementable as long as f2 / f1 is a number other than 1. As already stated, the effect of this disclosure is obtained when the convex portion of the time waveform of frequency f1 and the convex portion of the multiplied frequency f2 are aligned. When no assumptions can be made, f2 / f1 may be made to be an odd number of 3 or more. When the sign of the correlation between the first signal x(t) and the second signal y(t) is known or can be assumed, f2 / f1 may be made to be an even number of 2 or more. Furthermore, when the number of times (N) the phase of frequency f1 cycles around 2π by the delay amount is known or can be assumed, f2 / f1 may include a decimal point. Note that even when f2 / f1 is a negative number, it can still hold in principle and is within the scope of this disclosure.
[0036] (Inverse transform unit 313) The inverse transform unit 313 is responsible for performing an inverse Fourier transform on the added signal Cxy'(f) to generate the processed signal cxy'(t).
[0037] [Delay Amount Calculation Unit 33] The delay amount calculation unit 33 calculates the delay amount t. The delay amount t is the value of t at which the processed signal cxy'(t) is maximized. Note that when cxy'(t) is discretized, the maximum value of the processed signal cxy'(t) and the corresponding value of t will have quantization errors. For this reason, the delay amount calculation unit 33 may be configured to calculate the maximum value of cxy'(t) by combining a method for obtaining a second-order approximation or a method for performing a Hilbert transform.
[0038] [Effects of the Signal Processing Device 3] Figure 5 is a graph showing the results of a simulation using the signal processing device 3 according to Embodiment 1. In Figure 5, the second signal y(t) is obtained by superimposing delay and noise on the first signal x(t). The added signal Cxy'(f) has peaks around 40 [kHz] and around 120 [kHz], which is three times that frequency, confirming that the bandwidth multiplier unit has added amplified frequency components (a process to increase bandwidth). The point at the maximum value in the graph of the processed signal cxy'(t) indicates the amount of delay (the time difference between the first signal x(t) and the second signal y(t)). In other words, the steeper the upward convex shape of the graph, the more accurate the delay measurement becomes. Looking at the graph, it can be seen that the waveform obtained by signal processing using the signal processing device 3 according to this disclosure (Embodiment 1) (the darker colored waveform) is steeper than the waveform obtained by conventional signal processing (the lighter colored waveform), indicating improvements in both resolution and SNR.
[0039] Figure 6 is a graph showing the estimation error that occurs when intentional noise is superimposed. The signal obtained by conventional signal processing (upper panel) had a standard deviation σ of 3.30 × 10⁻⁸, while the signal obtained by the signal processing device 3 according to this disclosure (Embodiment 1) (lower panel) had a standard deviation σ of 2.61 × 10⁻⁸. In other words, in this example, the noise is reduced by 20%, and the performance is improved. It should be noted that this is merely an example, and a 20% reduction is not the upper limit of performance. Thus, the signal processing device 3 can improve the resolution and SNR of pulse compression without monopolizing bandwidth, or even when bandwidth is limited.
[0040] <Embodiment 2> Next, Embodiment 2 of the present disclosure will be described in detail. For convenience of explanation, members having the same functions as those described in Embodiment 1 above are denoted by the same reference numerals, and the description thereof will be omitted.
[0041] [Schematic Configuration of Measurement Device 100A and Signal Processing Device 3A] FIG. 7 is a block diagram showing an example of the functional configuration of a signal processing unit 31A included in a signal processing device 3A according to Embodiment 2. The measurement device 100A according to Embodiment 2 includes a signal processing device 3A in addition to the transmitter 1 and the receiver 2 similar to those included in the measurement device 100 according to Embodiment 1 (see FIG. 1). The signal processing device 3A according to Embodiment 2 includes a signal processing unit 31A in addition to the signal input unit 32 and the delay amount calculation unit 33 similar to those included in the signal processing device 3 according to Embodiment 1 above (see the upper part of FIG. 2). As shown in FIG. 7, the signal processing unit 31A according to Embodiment 2 includes a conversion unit 311A and a bandwidth doubling unit 312A in addition to the inverse conversion unit 313 similar to that included in the signal processing unit 31 according to Embodiment 1 above.
[0042] (Conversion Unit 311A) The conversion unit 311A includes a first conversion unit 311a and a second conversion unit 311b similar to those included in the conversion unit 311 according to Embodiment 1 above. On the other hand, the conversion unit 311A does not include a configuration corresponding to the cross-spectrum calculation unit 311c included in the conversion unit 311 according to Embodiment 1 above.
[0043] (Bandwidth Doubling Unit 312A) The bandwidth doubling unit 312A includes a first bandwidth doubling unit 312a, a second bandwidth doubling unit 312b, and a cross-spectrum calculation unit 312c.
[0044] - First Bandwidth Doubling Unit 312a The first bandwidth doubling unit 312a adds frequency components after doubling that were not included in the first-converted signal X(f) to the first-converted signal X(f) to generate a first-added signal X'(f).
[0045] - Second Bandwidth Doubling Unit 312b The second bandwidth doubling unit 312b adds frequency components after doubling that were not included in the second-converted signal Y(f) to the second-converted signal Y(f) to generate a second-added signal Y'(f).
[0046] - Cross-spectrum calculation unit 312c The cross-spectrum calculation unit 312c according to Embodiment 2 calculates the cross-spectrum Cxy'(f) of the first post-addition signal X'(f) and the second post-addition signal Y'(f) as the post-addition signal.
[0047] [Operation and effect of signal processing device 3A] Although the order of signal processing executed by the signal processing unit 31A in the signal processing device 3A described above is different from that of the signal processing unit 31 according to Embodiment 1, the same result as that of the signal processing unit 31 according to Embodiment 1 is calculated. Therefore, according to the signal processing device 3A, similar to the signal processing device 3 according to Embodiment 1, it is possible to improve the resolution and SNR of pulse compression without occupying a bandwidth or even when there are bandwidth constraints.
[0048] <Embodiment 3>Next, Embodiment 3 of the present disclosure will be described in detail. For the sake of convenience of explanation, members having the same functions as those described in Embodiment 1 above are denoted by the same reference numerals, and their descriptions are omitted.
[0049] [Schematic configuration of measurement device 100B and signal processing device 3B] FIG. 8 is a block diagram showing an example of the functional configuration of a signal processing unit 31B included in a signal processing device 3B according to Embodiment 3. The measurement device 100B according to Embodiment 3 includes a signal processing device 3B in addition to a transmitter 1 and a receiver 2 similar to those included in the measurement device 100 according to Embodiment 1 (see FIG. 1). The signal processing device 3B according to Embodiment 3 includes a signal processing unit 31B in addition to a signal input unit 32 and a delay amount calculation unit 33 similar to those included in the signal processing device 3 according to Embodiment 1 (see the upper part of FIG. 2). As shown in FIG. 8, the signal processing unit 31B according to Embodiment 3 includes a window processing unit 314 in addition to a conversion unit 311, a bandwidth doubling unit 312, and an inverse conversion unit 313 similar to those included in the signal processing unit 31 according to Embodiment 1.
[0050] (Window Processing Unit 314) The window processing unit 314 is responsible for extracting each input signal using a window function. The window processing unit 314 according to Embodiment 3 comprises a first window processing unit 314a and a second window processing unit 314b. The first window processing unit 314a extracts the input first signal x(t) using a window function. The first conversion unit 311a of the conversion unit 311 then generates a converted signal X(f) from the extracted first signal x(t). The second window processing unit 314b extracts the input second signal y(t) using a window function. The second conversion unit 311b of the conversion unit 311 then generates a converted signal Y(f) from the extracted second signal y(t).
[0051] [Effects of the signal processing device 3B] The signal processing device 3B described above extracts the input first signal x(t) and second signal y(t) using a window function via the window processing device 314. Therefore, with the signal processing device 3B, periodicity can be ensured when the signals (first signal x(t) and second signal y(t)) are extracted by time, preventing the estimated delay amount from becoming unexpected.
[0052] <Embodiment 4> Next, Embodiment 4 of the present disclosure will be described in detail. For the sake of convenience of explanation, components having the same function as those described in Embodiment 1 will be denoted by the same reference numerals, and their descriptions will be omitted.
[0053] [Outline Configuration of Measurement Device 100C and Signal Processing Device 3C] Figure 9 is a block diagram showing an example of the functional configuration of the signal processing unit 31C included in the signal processing device 3C according to Embodiment 4. The measurement device 100C according to Embodiment 4 includes a transmitter 1 and a receiver 2 similar to those included in the measurement device 100 according to Embodiment 1, as well as a signal processing device 3C (see Figure 1). The signal processing device 3C according to Embodiment 4 includes a signal input unit 32 similar to those included in the signal processing device 3 according to Embodiment 1, as well as a signal processing unit 31C and a delay amount calculation unit 33A (see lower part of Figure 2). As shown in Figure 9, the signal processing unit 31C according to Embodiment 4 includes a conversion unit 311 and a bandwidth multiplication unit 312 similar to those included in the signal processing unit 31 according to Embodiment 1, as well as an inverse conversion unit 313A.
[0054] (Inverse Transform Unit 313A) The inverse transform unit 313A according to Embodiment 4 comprises a first inverse transform unit 313a, a phase shift unit 313b, and a second inverse transform unit 313c. The first inverse transform unit 313a generates a processed signal cxy'(t) from the added signal (cross spectrum Cxy'(f)). The phase shift unit 313b generates a second added signal Cxy''(f) from the added signal Cxy'(f), which is shifted in phase by 90° from the added signal Cxy'(f). The second inverse transform unit 313c performs an inverse Fourier transform on the second added signal Cxy''(f) to generate a second processed signal cxy''(t).
[0055] [Delay Amount Calculation Unit 33A] The delay amount calculation unit 33A according to Embodiment 4 calculates the delay amount using the Hilbert transform. As described above, the delay amount to be obtained is the t at which the processed signal cxy'(t) is maximized. Therefore, The delay is calculated from discrete values, and the second processed signal cxy''(t), which is 90° out of phase with the processed signal cxy'(t), becomes 0 when the processed signal cxy'(t) takes its maximum value. Using this, the delay amount calculation unit 33A can calculate the delay amount using linear approximation of the preceding and succeeding signals. The delay amount calculation unit 33A may also be configured to calculate the delay amount using an interpolation method.
[0056] [Effects of the signal processing device 3C] The signal processing device 3C described above has a delay amount calculation unit 33A that calculates the delay amount using a Hilbert transform. Therefore, the maximum value can be easily calculated using the signal processing device 3C.
[0057] <Embodiment 5> Next, Embodiment 5 of the present disclosure will be described in detail. For the sake of convenience of explanation, components having the same function as those described in Embodiment 1 will be denoted by the same reference numerals, and their descriptions will be omitted.
[0058] [Outline Configuration of Measurement Device 100D and Signal Processing Device 3D] Figure 10 is a block diagram showing an example of the functional configuration of the signal processing device 3D according to Embodiment 5. The measurement device 100D according to Embodiment 5 includes a transmitter 1 and a receiver 2 similar to those provided in the measurement device 100 according to Embodiment 1, as well as a signal processing device 3D (see Figure 1). The signal processing device 3D according to Embodiment 5 includes a signal input unit 32 and a delay amount calculation unit 33 similar to those provided in the signal processing device 3 according to Embodiment 1, as well as a signal processing unit 31D (see upper part of Figure 2). As shown in Figure 10, the signal processing unit 31D according to Embodiment 5 includes a bandwidth multiplier unit 312 and an inverse conversion unit 313 similar to those provided in the signal processing unit 31 according to Embodiment 1, as well as a conversion unit 311B.
[0059] (Conversion Unit 311B) The conversion unit 311B according to Embodiment 5 generates a converted signal Cxy(f) using the Welch method. The conversion unit 311B according to Embodiment 5 includes a first conversion unit 311a, a second conversion unit 311b, and a cross-spectrum calculation unit 311c, similar to those provided in the conversion unit 311 according to Embodiment 1, as well as a first window processing unit 311d and a second window processing unit 311e. The first window processing unit 311d and the second window processing unit 311e are configured similarly to the first window processing unit 314a and the second window processing unit 314b provided in the window processing unit 314 of the signal processing unit 31B according to Embodiment 3. The conversion unit 311B then repeats the same operations as those performed by the window processing unit 314 and the conversion unit 311 of the signal processing unit 31B according to the third embodiment, while sliding the first window processing unit 311d and the second window processing unit 311e (while changing the window function). The conversion unit 311B then calculates the average of multiple cross spectra obtained by the cross-spectrum calculation unit 311c through repeated calculations, and uses this average as the converted signal Cxy(f).
[0060] [Effects of the signal processing device 3D] The signal processing device 3D described above generates a converted signal Cxy(f) using the Welch method in the conversion unit 311B. Therefore, with the signal processing device 3D, cross-spectral noise is reduced, and if sufficient measurement time can be secured, accuracy can be improved.
[0061] <Modifications> Although embodiments for implementing this disclosure have been described above using Embodiments 1 to 5, this disclosure is not limited in any way to these embodiments, and various modifications and substitutions can be made without departing from the gist of this disclosure. Furthermore, embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure.
[0062] <Summary 1> The signal processing device according to Embodiment 1A of the present disclosure is a signal processing device that processes signals using pulse compression, and comprises: a conversion unit that performs a Fourier transform on an input signal to generate a converted signal; a bandwidth multiplication unit that adds a signal bandwidth that was not included in the converted signal to generate an added signal; and an inverse conversion unit that performs an inverse Fourier transform on the added signal bandwidth together with the added signal bandwidth to generate a processed signal.
[0063] The signal processing device according to Embodiment 2A of the present disclosure may be configured such that, in Embodiment 1A above, the conversion unit comprises: a first conversion unit that performs a Fourier transform on a first signal used as a reference for the delay amount, which is input from a transmitter or the like, to generate a first converted signal; a second conversion unit that performs a Fourier transform on a second signal used as the target of measurement for the delay amount, which is input from a receiver or the like, to generate a second converted signal; and a cross-spectrum calculation unit that calculates the cross spectrum of the first converted signal and the second converted signal as the converted signal.
[0064] The signal processing device according to embodiment 3A of the present disclosure may be configured such that, in embodiment 1A or 2A above, the conversion unit comprises a first conversion unit that performs a Fourier transform on a first signal used as a reference for the amount of delay input from a transmitter or the like to generate a first converted signal, and a second conversion unit that performs a Fourier transform on a second signal used as the target of measurement for the amount of delay input from a receiver or the like to generate a second converted signal, and the bandwidth multiplier unit comprises a first bandwidth multiplier unit that adds a signal bandwidth not included in the first converted signal to generate a first added signal, a second bandwidth multiplier unit that adds a signal bandwidth not included in the second converted signal to generate a second added signal, and a cross-spectrum calculation unit that calculates the cross spectrum of the first added signal and the second added signal as the added signal.
[0065] The signal processing device according to aspect 4A of the present disclosure may be a signal processing device in which the bandwidth multiplier unit retrospectively adds the signal bandwidth by modulation or mapping, in any one of the above aspects 1A to 3A.
[0066] In the signal processing apparatus according to embodiment 5A of the present disclosure, the cross-spectrum calculation unit may be configured to calculate the cross-spectrum using the cross-correlation method, as described in embodiment 2A or 3A above.
[0067] The signal processing device according to embodiment 6A of the present disclosure may be the signal processing device that further comprises a delay amount calculation unit for calculating the delay amount in embodiment 2A or 3A described above.
[0068] In the signal processing apparatus according to embodiment 7A of the present disclosure, the delay amount calculation unit may be configured to calculate the delay amount using an interpolation method or a Hilbert transform, as in embodiment 6A described above.
[0069] The signal processing device according to aspect 8A of the present disclosure may further include a window processing unit that extracts the input signal using a window function, as described in any one of aspects 1A to 7A above.
[0070] In the signal processing apparatus according to aspect 9A of the present disclosure, the conversion unit may be configured to generate the converted signal using the Welch method, as described in aspect 8A above.
[0071] The measuring device according to embodiment 10A of the present disclosure may be configured to include, in any one of embodiments 1A to 9A above, a transmitter that transmits a signal, a receiver that receives the signal transmitted from the transmitter, and the signal processing device.
[0072] <Summary 2> The signal processing device according to Embodiment 1B of the present disclosure is a signal processing device that processes a signal using pulse compression, and may be configured to include: a conversion unit that performs a Fourier transform on an input signal to generate a converted signal; a bandwidth multiplier unit that adds a signal bandwidth that was not included in the converted signal as a multiplied frequency component to generate an added signal; and an inverse transform unit that performs an inverse Fourier transform on the added signal to generate a processed signal.
[0073] In the signal processing apparatus according to embodiment 2B of the present disclosure, the bandwidth multiplier unit may be configured such that, in embodiment 1B, the multiplier unit generates the multiplied frequency component such that at least one convex portion in the time waveform of any frequency component of the converted signal aligns with at least one convex portion in the time waveform of the multiplied frequency component.
[0074] In the signal processing apparatus according to embodiment 3B of the present disclosure, the bandwidth multiplier unit may be configured to generate the added signal by subsequently adding the multiplied frequency component by modulation or mapping, as in embodiment 1B or 2B described above.
[0075] The signal processing device according to Embodiment 4B of the present disclosure may be configured such that, in any one of Embodiments 1B to 3B above, the conversion unit comprises a first conversion unit that performs a Fourier transform on a first signal from the input signal which is used as a reference for the delay amount to generate a first converted signal, and a second conversion unit that performs a Fourier transform on a second signal from the input signal which is used as the target for measuring the delay amount to generate a second converted signal, and the bandwidth multiplier unit has a cross-spectrum calculation unit which adds the respective multiplied frequency components to the first converted signal and the second converted signal, and generates the added signal by calculating the cross spectrum of the obtained signals using the cross-spectrum calculation unit, or the conversion unit has a cross-spectrum calculation unit which calculates the cross spectrum of the first converted signal and the second converted signal using the cross-spectrum calculation unit, and generates the added signal by adding the multiplied frequency components to the obtained cross spectrum using the bandwidth multiplier unit.
[0076] In the signal processing apparatus according to embodiment 5B of the present disclosure, the cross-spectrum calculation unit may be configured to calculate the cross-spectrum using the cross-correlation method, as described in embodiment 4B above.
[0077] The signal processing device according to embodiment 6B of the present disclosure may further include a delay amount calculation unit for calculating the delay amount, as in embodiment 4B or 5B described above.
[0078] The measuring device according to embodiment 7B of the present disclosure may be configured to include, in any one of embodiments 1B to 6B above, a transmitter that transmits a signal, a receiver that receives the signal transmitted from the transmitter, and the signal processing device.
[0079] 100, 100A, 100B, 100C, 100D Measuring device 1 Transmitter 2 Receiver 3, 3A, 3B, 3C, 3D Signal processing device 31, 31A, 31B, 31C, 31D Signal processing unit 311, 311A, 311B Conversion unit 311a First conversion unit 311b Second conversion unit 311c Cross-spectrum calculation unit 311d First window processing unit 311e Second window processing unit 312, 312A Bandwidth multiplication unit 312a First bandwidth multiplication unit 312b Second bandwidth multiplication unit 312c Cross-spectrum calculation unit 313, 313A Inverse conversion unit 313a First inverse conversion unit 313b Phase change unit 313c Second inverse conversion unit 314, 314A Window processing unit 314a First window processing unit 314b Second window processing unit 32 Signal input unit 33, 33A Delay amount calculation unit x(t) First signal y(t) Second signal X(f) First converted signal Y(f) Second converted signal Cxy(f) Converted signal (cross spectrum of the first converted signal and the first converted signal) X'(f) First added signal Y'(f) Second added signal Cxy'(f) Added signal (cross spectrum of the first added signal and the second added signal) cxy'(t) Processed signal cxy''(t) Second processed signal
Claims
1. A signal processing device that processes signals using pulse compression, comprising: a conversion unit that performs a Fourier transform on an input signal to generate a converted signal; a bandwidth multiplier unit that adds a signal bandwidth not included in the converted signal as a multiplied frequency component to the converted signal to generate an added signal; and an inverse transform unit that performs an inverse Fourier transform on the added signal to generate a processed signal.
2. The signal processing apparatus according to claim 1, wherein the bandwidth multiplier generates the multiplied frequency component such that at least one convex portion in the time waveform of any frequency component of the converted signal aligns with at least one convex portion in the time waveform of the multiplied frequency component.
3. The signal processing apparatus according to claim 1, wherein the bandwidth multiplier unit subsequently adds the multiplied frequency component by modulation or mapping to generate the added signal.
4. The signal processing apparatus according to any one of claims 1 to 3, wherein the conversion unit comprises: a first conversion unit that performs a Fourier transform on a first signal from the input signal which is used as a reference for the delay amount to generate a first converted signal; and a second conversion unit that performs a Fourier transform on a second signal from the input signal which is the target of measurement for the delay amount to generate a second converted signal, and the band multiplication unit comprises: a cross-spectrum calculation unit which adds the respective multiplied frequency components to the first converted signal and the second converted signal, and generates the added signal by calculating the cross spectrum of the obtained signals using the cross-spectrum calculation unit, or: the conversion unit comprises a cross-spectrum calculation unit which calculates the cross spectrum of the first converted signal and the second converted signal using the cross-spectrum calculation unit, and generates the added signal by adding the multiplied frequency components to the obtained cross spectrum using the band multiplication unit.
5. The signal processing apparatus according to claim 4, wherein the cross-spectrum calculation unit calculates the cross-spectrum using the cross-correlation method.
6. The signal processing apparatus according to claim 4, further comprising a delay amount calculation unit for calculating the aforementioned delay amount.
7. A measuring device comprising: a transmitter that transmits a signal; a receiver that receives the signal transmitted from the transmitter; and a signal processing device according to any one of claims 1 to 3.