radar equipment

Abstract

The present invention provides a radar device that has a simple circuit configuration, performs simple signal processing, and reduces the computational load of signal processing. [Solution] The radar device comprises a transmitting unit that transmits a transmission pulse having a first pulse width, a receiving unit that receives a reflected wave generated when the transmission pulse is reflected as a received signal, a reference signal generation unit that generates a reference pulse having a second pulse width at predetermined intervals, a correlation processing unit that calculates a correlation amount between the received signal and the reference pulse by integrating a mixed signal generated by mixing the received signal and the reference pulse, and a signal processing unit that processes the correlation amount. The first pulse width is at least twice the predetermined interval.

Description

[Technical Field]

[0001] The present invention relates to a radar apparatus for object detection. [Background Art]

[0002] Conventionally, various radar apparatuses have been proposed for object detection. Patent Document 1 discloses a radar apparatus that transmits a pulse wave and performs quadrature detection on a received signal. The radar apparatus comprises a transmission unit, a reception unit, and a signal processing unit. The transmission unit transmits radar pulses toward a radar target. The reception unit receives the reflected wave of the radar pulse, mixes the received signal with a reference pulse, and integrates the mixed product. The radar apparatus performs first to fourth radar measurements. The delay time of the reference pulse relative to the radar pulse in each of the second to fourth radar measurements is a quarter of the wavelength of the radar pulse longer than the delay time of the reference pulse relative to the radar pulse in each of the first to third radar measurements, respectively. The signal processing unit obtains the difference between the integrated mixed products of the first and third radar measurements as an estimated value of an in-phase component I, and obtains the difference between the integrated mixed products of the second and fourth radar measurements as an estimated value of a quadrature component Q. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese National Publication of International Patent Application No. 2024-543170 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] The radar apparatus disclosed in Patent Document 1 requires high-precision control of the phase of radar pulses of a plurality of reference pulses, and thus has a complicated circuit configuration. In addition, the above-described radar apparatus requires complicated branched signal processing to perform quadrature detection, and also requires a large amount of computation for signal processing.

[0005] The object of the present invention is to provide a radar device that has a simple circuit configuration, performs simple signal processing, and can reduce the amount of computation required for signal processing. [Means for solving the problem]

[0006] A radar device according to one embodiment of the present invention includes a transmitting unit that transmits a transmission pulse having a first pulse width, a receiving unit that receives a reflected wave generated by the reflection of the transmission pulse as a received signal, a reference signal generation unit that generates a reference pulse having a second pulse width at predetermined intervals, a correlation processing unit that calculates a correlation amount between the received signal and the reference pulse by integrating a mixed signal generated by mixing the received signal and the reference pulse, and a signal processing unit that processes the correlation amount, wherein the first pulse width is at least twice the predetermined interval.

[0007] A radar device according to another embodiment of the present invention includes: a transmitting unit that transmits a transmission pulse having a first pulse width; a receiving unit that receives a reflected wave generated when the transmission pulse is reflected from a reflector as a received signal; a reference signal generating unit that generates a reference pulse having a second pulse width at predetermined intervals; a correlation processing unit that integrates a mixed signal generated by mixing the received signal and the reference pulse to calculate a correlation amount between the received signal and the reference pulse; and a signal processing unit that processes the correlation amount and calculates a correlation amount for measurement points at distance intervals corresponding to predetermined intervals of the reference pulse, wherein the transmission pulse is set such that the received signal from the reflector affects the correlation amount of the plurality of measurement points. [Effects of the Invention]

[0008] According to the present invention, a radar device can be realized that has a simple circuit configuration, performs simple signal processing, and reduces the amount of computation required for signal processing. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a functional block diagram showing a radar system according to an embodiment. [Figure 2] Figure 2 is a conceptual diagram showing the relationship between the reference signal, the transmitted pulse, the received signal, and the reference pulse. [Figure 3] Figure 3 is a conceptual diagram showing a reference pulse. [Figure 4] Figure 4 shows an example of the total correlation. [Figure 5] Figure 5 shows an example of the mean square of the residuals of the total correlation shown in Figure 4. [Figure 6] Figure 6 shows an example of the relationship between correlation and distance. [Modes for carrying out the invention]

[0010] Figure 1 is a functional block diagram showing a radar device according to an embodiment. Figure 2 is a conceptual diagram showing the relationship between the reference signal, the transmitted pulse, the received signal, and the reference pulse. Figure 3 is a conceptual diagram showing the reference pulse.

[0011] The radar system comprises a transmitter 1, a receiver 2, a reference signal generation unit 3, a correlation processing unit 4, and a signal processing unit 5. The transmitter 1 transmits a transmission pulse having a pulse width Ts (first pulse width). The receiver 2 receives the reflected wave generated by the reflection of the transmission pulse as a received signal. The reference signal generation unit 3 generates reference pulses having a pulse width Tr (second pulse width) at intervals Ti (predetermined intervals). The interval Ti corresponds to the time from the start of any given reference pulse to the start of the next reference pulse. The correlation processing unit 4 calculates the correlation amount between the received signal and the reference pulse by integrating the mixed signal generated by mixing the received signal and the reference pulse. The signal processing unit 5 processes the correlation amount. The pulse width Ts is at least twice the interval Ti. The pulse width Tr is equal to a natural number multiple of half the period Tc of the carrier wave of the reference pulse.

[0012] Specifically, the transmitting unit 1 includes, for example, an oscillator, modulator, power amplifier, antenna, etc., and generates a reference signal, modulates and amplifies the reference signal to generate a transmission pulse, and radiates the transmission pulse. The transmitting unit 1 radiates radio waves, particularly millimeter waves. The carrier wave of the transmission pulse has the same frequency as the reference signal and the same phase as the reference signal. The receiving unit 2 includes, for example, an antenna, low-noise amplifier, A / D converter, etc., and receives radio waves, particularly reflected waves generated when the transmission pulse is reflected by an object. The reference signal generation unit 3 modulates the reference signal acquired from the transmitting unit 1 to generate each reference pulse. The carrier wave of each reference pulse has the same frequency as the reference signal and the same phase as the reference signal. The interval Ti of the reference pulses is longer than the pulse width Tr of the reference pulses. The amplitude of each reference pulse changes in the same way with time, relative to the time the reference pulse starts, and is substantially constant in particular during the duration of the reference pulse. The duration of a reference pulse corresponds to the period from when the reference pulse starts until when it ends. The reference signal generation unit 3 and the correlation processing unit 4 are composed of a CPU, memory, etc., and store a program. By executing this program, they perform predetermined processing.

[0013] In the modified example, the pulse width Tr may be different from a natural number multiple of half the period of the carrier wave of the reference pulse.

[0014] In another modified example, the transmitted pulse may have a phase that is shifted from the phase of the reference signal. Each reference pulse may have a phase that is shifted by the same amount from the phase of the reference signal.

[0015] The radar system repeats a cycle consisting of the process from transmitting a transmission pulse to processing a received signal. The transmission unit 1 transmits one transmission pulse in each cycle. The reference signal generation unit 3 generates N reference pulses in each cycle.

[0016] Referring to Figure 2, the correlation processing unit is:

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[0017] When a transmission pulse is reflected by an object that does not move at a very high speed, the reception signal and the reference pulse are generally [Math.]] expressed as follows. Here, βm(t) represents the amplitude value of the reception signal xm at time t. γ(t) represents the amplitude value of the reference pulse y1,1 at time t. Um,n represents the time from time t1,1 to time tm,n. f represents the frequency of the reference signal, ψ0 represents the initial phase of the reference signal, and λ represents the wavelength of a radio wave radiated from the transmission unit 1. dm represents the distance from the radar device to the object when the transmission pulse of the m-th cycle reaches the object. θm represents the phase difference of the reception signal xm with respect to the reference signal caused by factors other than the distance dm. When the amplitude of the reference pulse is constant over the duration of the reference pulse and can be considered to take a value of C, the correlation amount is [Math.]] expressed as follows. Since the integrand of the first term of Equation 3 fluctuates periodically, the absolute value of the integral of the first term of Equation 3 becomes small.

[0018] In particular, the pulse width Tr is equal to a natural number multiple of Tc / 2. Therefore, the integration range of the first term in Equation 3 is equal to a natural number multiple of Tc / 2. On the other hand, the period of the cosine in the integrand of the first term in Equation 3 is equal to Tc / 2. Therefore, if the amplitude of the received signal can be considered constant over the duration of the reference pulse, the absolute value of the integral of the first term in Equation 3 becomes very small.

[0019] Therefore, the correlation is approximately

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[0020] The amplitude of the received signal changes depending on the presence or absence of a reflector that reflects radio waves. Therefore, the correlation also changes depending on the presence or absence of a reflector. In addition, the phase difference of the received signal with respect to the reference signal changes significantly with small changes in the distance from the radar device to the reflector. Therefore, the correlation fluctuates periodically according to the movement of the reflector. Furthermore, the average amplitude Bm,n of the received signal takes a larger value when the reflector is near a distance cτn / 2 from the radar device during the mth cycle than when the reflector is not near that position. Here, c is the speed of light in a vacuum. τn is the time from the start time of transmission of a given cycle's transmission pulse to the start time of the nth reference pulse of that cycle. Therefore, the correlation changes depending on the distance from the radar device to the reflector. Thus, by processing the correlation, it is possible to detect objects, detect object motion, and estimate the distance from the laser device to an object.

[0021] The correlation quantity can be zero even when the amplitude of the received signal is large, because the cosine in the integrand of the second term of Equation 3 takes a value of zero within the integration range. However, the pulse width Ts is set to more than twice the interval Ti. Also, generally, the transmitted pulse is reflected off the surface of an object with a complex shape, so the reflected wave has a complex waveform. Therefore, the phase φm(t) of the received signal is not exactly equal to ψ(t)+χm. As a result, the cosine in the integrand of the second term of Equation 3 may take a value of zero in the integration range from tm,i to tm,i+Tr, but may take a non-zero value in the integration range from another tm,j to tm,j+Tr. Therefore, even if the correlation quantity S(m,i) takes a value of zero, the correlation quantity S(m,j) may take a non-zero value. Thus, the loss of amplitude information of the received signal can be suppressed.

[0022] In the modified example, the transmitted pulse only needs to affect multiple integration ranges, and is not limited to setting the pulse width Ts to more than twice the interval Ti. For example, even if the pulse width Ts of the transmitted pulse is less than twice the interval Ti, multiple pulse waves may be transmitted at regular intervals in each cycle. This makes it possible to achieve substantially the same effect by mixing the received signal from a reflector at a certain distance with multiple reference pulses having interval Ti.

[0023] In other words, influencing multiple integration ranges can be rephrased as saying that a received pulse from a reflector at a certain distance affects the correlation at multiple adjacent distances corresponding to the interval Ti of the reference pulses.

[0024] The signal processing unit calculates the total correlation by summing the absolute values ​​of the differences between the average correlation values ​​A(m,1), ..., A(m,N) and the reference value of the average correlation. A(m,n) represents the average value of one or more S(ml,n), ..., S(mu,n) that include S(m,n). Specifically, the signal processing unit,

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[0025] In the modified example, A(m,n) may represent the average value of S(m,n), ..., S(m+Ma-1,n).

[0026] Next, the signal processing unit compares the total correlation amount with a threshold to determine the presence or absence of a reflector. For example, if the total correlation amount E(m) is greater than or equal to the threshold, the signal processing unit may determine that the object is within the radar's coverage area during the mth cycle. If the total correlation amount E(m) is less than the threshold, the signal processing unit may determine that the object is not within the radar's coverage area during the mth cycle. The radar's coverage area may be set, for example, to a range within a distance cτN / 2 from the radar.

[0027] As can be seen from equation 4, the absolute value of the correlation S(m,n) can be larger when the object is near a distance cτn / 2 from the radar device during the m-th cycle than when the object is not near that location. The average correlation corresponds to the smoothed correlation. Therefore, the total correlation E(m) takes a large value when the object is within the radar device's coverage area during the m-th cycle. Thus, by comparing the total correlation E(m) with a threshold, it is possible to determine whether the object is within the radar device's coverage area during the m-th cycle.

[0028] The signal processing unit determines whether or not the reflector is moving based on the variation in the total correlation. Specifically, first, the signal processing unit calculates the mean square of the residuals of the total correlation. Specifically, the signal processing unit 5,

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[0029] In the modified example, Se(m) may represent the sum of squared residuals of a linear regression applied to the data (1, E(m)), ..., (Mr, E(m+Mr-1)).

[0030] Next, the signal processing unit compares the mean square of the residuals with a threshold to determine whether or not the reflecting object is moving. For example, if the mean square of the residuals F(m) is greater than or equal to the threshold, the signal processing unit may determine that the object is moving during the mth cycle. If the mean square of the residuals F(m) is less than the threshold, the signal processing unit may determine that the object is stationary during the mth cycle.

[0031] As can be seen from equation 4, when an object moves near a distance cτn / 2 from the radar device around the time of the mth cycle, the correlation S(μ,n) fluctuates periodically with the change in μ around μ=m. The mean correlation corresponds to the smoothed correlation. Therefore, when an object moves within the radar device's coverage area around the time of the mth cycle, the total correlation E(μ) fluctuates periodically around μ=m, and the residual mean square F(m) takes a large value. Thus, by comparing the residual mean square F(m) with a threshold, it is possible to determine whether the object is moving during the mth cycle.

[0032] In the modified form, the variability of the total correlation may be expressed in terms of variance, standard deviation, or other statistics instead of the mean square of the residuals.

[0033] Figure 4 shows an example of the total correlation. Figure 5 shows an example of the mean square residual of the total correlation shown in Figure 4. In Figure 4, Ma is set to 10. In Figure 5, Mr is set to 50. In Figures 4 and 5, a1, a2, a3, a4, and a5 represent periods when there is no object, when there is a person, when there is a vehicle with the engine running, when there is a vehicle with the engine not running, and when there is a vehicle being shaken by a person, respectively. The total correlation is large during periods when an object is present. Also, the total correlation fluctuates significantly and periodically during periods when a person is present. The mean square residual of the total correlation is large during periods when a person is present and during periods when the presence or absence of an object changes. In the examples shown in Figures 4 and 5, by calculating the total correlation and its mean square residual, it is possible to detect an object and determine whether that object is a person or another object.

[0034] The signal processing unit estimates the distance from the radar device to the reflector based on the change in the correlation quantity S(m,n) in response to a change in n. For example, if the absolute value of the difference between the value of the correlation quantity S(m,ν) and the reference value of the correlation quantity takes its maximum value at ν=n in response to a change in ν, the signal processing unit estimates the distance from the radar device to the object based on the behavior of the correlation quantity S(m,ν) around ν=n. The reference value of the correlation quantity corresponds, for example, to the correlation quantity when there is no object.

[0035] Figure 6 shows an example of the relationship between the difference of a correlation quantity to its reference value and the distance. Figure 6 shows the value of the correlation quantity S(m,n) for a given m, expressed as a distance of cτn / 2. For example, the signal processing unit estimates the distance from the radar device to the object based on the behavior of the correlation quantity around its peak. The distance intervals of the measurement points in Figure 6 correspond to the interval Ti of the reference pulse.

[0036] A radar system may perform the following steps in a single cycle, for example: First, the radar system transmits a transmission pulse in its transmitter unit and receives the reflected wave as a received signal in its receiver unit. Next, the radar system calculates a correlation amount from the received signal and its respective reference pulses in its correlation processing unit. Then, the radar system calculates a total correlation amount from the correlation amount in its signal processing unit and determines whether an object is present based on this total correlation amount. If an object is detected, the signal processing unit calculates the sum of squared residuals of the total correlation amount, determines whether the object is moving based on this sum of squared residuals, estimates the distance from the radar system to the object, ends the current cycle, and starts the next cycle. If no object is detected, the signal processing unit ends the current cycle and moves to the next cycle.

[0037] The signal processing unit may start calculating the total correlation and the sum of squared residuals from the Mrth cycle. Alternatively, the signal processing unit may calculate the total correlation and the sum of squared residuals in a cycle prior to the Mrth cycle using a pre-given initial value for the correlation.

[0038] In the modified version, the signal processing unit does not need to detect the motion of the object. Furthermore, the signal processing unit does not need to estimate the distance from the laser device to the object. Additionally, the signal processing unit may process the correlation quantity in a manner different from that described above.

[0039] For example, radar equipment may be installed in factories or construction sites to monitor whether people are in dangerous areas in order to ensure human safety.

[0040] Furthermore, the laser device can detect an object by transmitting one or several transmission pulses depending on the setting of the number of data points Ma, and therefore can detect objects at high speed. For this reason, the laser device may be used to detect the passage of a fast-moving object.

[0041] Furthermore, since laser devices can distinguish between people and vehicles, they may also be used to detect parking.

[0042] Alternatively, the laser device may be mounted on a vibrating body such as heavy machinery, and while monitoring for abnormalities in the vibrating body, it may also monitor for the presence or absence of workers.

[0043] Furthermore, the laser device may estimate the distance from the laser device to the object and determine whether the object is within a predetermined area.

[0044] According to this embodiment, the reference signal generation unit generates reference pulses at intervals Ti. The correlation processing unit integrates the mixed signal generated by mixing the received signal and the reference pulses to calculate the correlation amount between the received signal and the reference pulses.

[0045] Therefore, radar systems do not require phase control of the reference pulse. Consequently, the circuit configuration of radar systems becomes simpler.

[0046] Furthermore, radar systems do not require branching signal processing like quadrature detection. Therefore, signal processing in radar systems is simplified, and the error in signal processing is reduced. Additionally, the amount of computation required for signal processing is reduced, resulting in lower power consumption for the radar system.

[0047] Furthermore, the pulse width Ts is more than twice the interval Ti. Therefore, as mentioned above, it is unlikely that all correlation values ​​for the same cycle will be zero. Consequently, the loss of amplitude information in the received signal can be suppressed.

[0048] Furthermore, the correlation processing unit mixes the received signal with a reference pulse generated at interval Ti to thin the received signal, and uses that thinned signal to calculate the correlation amount. Therefore, the computational load of signal processing can be further reduced.

[0049] Furthermore, the pulse width Tr is equal to a natural number multiple of half the period Tc of the reference pulse's carrier wave. Therefore, as described above, the correlation quantity S(m,n) is more clearly proportional to the cosine of the average amplitude Bm,n of the received signal and the phase difference χm of the received signal with respect to the reference signal. The signal processing unit processes the correlation quantity assuming such a proportional relationship. Thus, the accuracy of the results of the correlation quantity processing can be improved.

[0050] Furthermore, the signal processing unit can perform object detection, object motion detection, and distance estimation from the laser device to the object by processing correlation quantities.

[0051] Furthermore, as described above, the laser device can detect objects by transmitting one or several transmission pulses depending on the setting of the number of data points Ma, and therefore can detect objects at high speed.

[0052] The configurations shown in the above embodiments or modifications may be replaced or combined as appropriate.

[0053] The above description of embodiments should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not by the above embodiments. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0054] 1: Transmitter 2: Receiving unit 3: Reference signal generation section 4: Correlation Processing Unit 5: Signal Processing Unit

Claims

1. A transmitting unit that transmits a transmission pulse having a first pulse width, A receiving unit that receives the reflected wave generated when the transmitted pulse is reflected as a received signal, A reference signal generation unit that generates a reference pulse having a second pulse width at predetermined intervals, A correlation processing unit calculates the correlation between the received signal and the reference pulse by integrating the mixed signal generated by mixing the received signal and the reference pulse, It comprises a signal processing unit that processes correlation quantities, A radar device in which the first pulse width is at least twice the predetermined interval.

2. The radar apparatus according to claim 1, wherein the second pulse width is equal to a natural number multiple of half the period of the carrier wave of the reference pulse.

3. The transmitting unit transmits one transmission pulse in each cycle. The aforementioned reference signal generation unit generates N reference pulses in each cycle, The signal processing unit calculates the total correlation amount as the sum of the absolute values ​​of the differences between the average correlation amounts A(m,1), ..., A(m,N) and a reference value of the average correlation amount, compares the total correlation amount with a threshold to determine the presence or absence of a reflector, A(m,n) represents the average value of one or more S(ml,n), ..., S(mu,n) including S(m,n), and S(m,n) represents the correlation amount between the received signal received in the mth cycle and the nth reference pulse generated in the mth cycle, according to claim 1 or 2.

4. The radar device according to claim 3, wherein the signal processing unit determines whether or not there is movement of a reflector based on the variation in the total correlation amount.

5. The radar device according to claim 4, wherein the signal processing unit calculates the mean square of the residuals of the total correlation amount and compares the mean square of the residuals with a threshold to determine whether or not there is movement of the reflector.

6. The radar device according to claim 3, wherein the signal processing unit estimates the distance from the radar device to the reflector based on the change in the correlation amount S(m,n) with respect to the change in n.

7. A transmitting unit that transmits a transmission pulse having a first pulse width, A receiving unit that receives the reflected wave generated when the transmitted pulse is reflected from a reflector as a received signal, A reference signal generation unit that generates a reference pulse having a second pulse width at predetermined intervals, A correlation processing unit calculates the correlation between the received signal and the reference pulse by integrating the mixed signal generated by mixing the received signal and the reference pulse, The system includes a signal processing unit that processes the correlation amount and calculates the correlation amount of measurement points at distance intervals corresponding to a predetermined interval of the reference pulse, A radar device in which the transmission pulse is set such that the received signal from the reflector affects the correlation between the multiple measurement points.

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