Radar target detection device and radar target detection program

Abstract

To improve the accuracy of detecting a target by applying a median filter to a mixer result of a radar reflection signal and a local oscillation signal and reducing the phase noise of each frequency component after the application of the median filter when removing interference spike noise from other devices.SOLUTION: The present disclosure is a radar target detection device R which applies a median filter to a multiplication result of a mixer 4 and detects a target T on the basis of an application result of the median filter, detects interference spike noise in the multiplication result of the mixer 4, on the basis of the magnitude of the difference between the multiplication result of the mixer 4 and the application result of the median filter, removes the multiplication result of the mixer 4 in an interference spike noise detection period, and interpolates the multiplication result of the mixer 4 in the interference spike noise removal period, on the basis of the multiplication result of the mixer 4 in periods before and after the interference spike noise removal period.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a radar target detection technology for removing interference from other devices.

Background Art

[0002] The configuration of a radar target detection device of the prior art (for example, Patent Document 1 etc.) is shown in FIG. 1. The radar target detection device R includes an oscillator 1, a transmission antenna 2, a reception antenna 3, a mixer 4, a median filter unit 5, and a target detection unit 6, and removes interference from other devices I.

[0003] The oscillator 1 generates a radar transmission signal and a local oscillation signal. The transmission antenna 2 irradiates the radar transmission signal. The reception antenna 3 receives the radar reflection signal. The mixer 4 multiplies the radar reflection signal and the local oscillation signal. The median filter unit 5 removes interference from other devices I by applying a median filter to the multiplication result of the mixer 4. The target detection unit 6 detects the target T based on the application result of the median filter unit 5.

[0004] The principle of the prior art interference removal process is shown in FIG. 2. In the left column of FIG. 2, when the radar target detection device R and other device I periodically operate intermittently at mutually shifted timings, periodic interference spike noise from other device I occurs. Different from the right column of FIG. 2, when a linear filter such as a moving average filter or a low-pass filter is applied to the multiplication result of the mixer 4, the interference spike time width from other device I is expanded. In the right column of FIG. 2, by applying a non-linear filter such as a median filter that adopts the amplitude median value in a predetermined time range to the multiplication result of the mixer 4, the interference spike noise from other device I is removed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Specific examples of the interference removal process for the problem to be solved are shown in FIGS. 3 and 4. In the left column of FIG. 3, the multiplication result of the mixer 4 includes the fundamental wave, the second harmonic, and the third harmonic, and also includes interference spike noise from another device I at time = 180 (the sampling interval is set to a somewhat wider interval). In the right column of FIG. 3, the application result of the median filter section 5 maintains the fundamental wave, the second harmonic, and the third harmonic, and removes the interference spike noise from another device I at time = 180.

[0007] In FIG. 4, the Fourier transform of the application result of the median filter section 5 includes the fundamental wave, the second harmonic, and the third harmonic, and also includes spurs such as the fourth harmonic and the fifth harmonic. This is because when a non-linear filter such as a median filter is applied, unlike when a linear filter such as a moving average filter or a low-pass filter is applied, an interaction occurs between each frequency component, so the relative phase between each frequency component is not maintained, and spurs such as harmonics are generated.

[0008] Then, when detecting the target T based on the phase of each frequency component, the phase noise of each frequency component increases, so there is a possibility that the detection accuracy of the target T will decrease.

[0009] Therefore, in order to solve the above problems, the present disclosure aims to improve the detection accuracy of a target by reducing the phase noise of each frequency component after applying a median filter when removing interference spike noise from another device by applying a median filter to the mixer result of the radar reflection signal and the local oscillation signal.

Means for Solving the Problems

[0010] In order to solve the above problems, interference spike noise in the multiplication result of the mixer is detected based on the magnitude of the difference between the multiplication result of the mixer and the application result of the median filter unit. Then, the interference spike noise is removed by applying the signal interpolation unit during the detection period of the interference spike noise without applying the median filter unit to the multiplication result of the mixer.

[0011] Specifically, the present disclosure provides a radar target detection device including an oscillator that generates a radar transmission signal and a local oscillation signal, a transmission antenna that irradiates the radar transmission signal, a reception antenna that receives the radar reflection signal, a mixer that multiplies the radar reflection signal and the local oscillation signal, a median filter unit that applies a median filter to the multiplication result of the mixer, and a target detection unit that detects a target based on the application result of the median filter unit, further comprising an interference detection unit that detects interference spike noise in the multiplication result of the mixer based on the magnitude of the difference between the multiplication result of the mixer and the application result of the median filter unit.

[0012] According to this configuration, by applying a median filter to the multiplication result of the mixer, interference spike noise from other devices can be detected.

[0013] The present disclosure further provides a radar target detection device, further comprising an interference removal unit that removes the multiplication result of the mixer during the detection period of the interference spike noise.

[0014] According to this configuration, the peak of the interference spike noise from other devices can be removed. Here, the period of the interference spike noise from other devices may be zero-padded.

[0015] The present disclosure further provides a radar target detection device, further comprising a signal interpolation unit that interpolates the multiplication result of the mixer during the removal period of the interference spike noise based on the multiplication result of the mixer in the periods before and after the removal period of the interference spike noise.

[0016] According to this configuration, it is possible to interpolate the period of interference spike noise from other devices. Here, the period of interference spike noise from other devices is a short period that is easy to interpolate.

[0017] Further, the present disclosure is a radar target detection program for causing a computer to execute a median filter procedure, a target detection procedure, and an interference detection procedure performed by the median filter unit, the target detection unit, and the interference detection unit included in the radar target detection device described above.

[0018] According to this configuration, it is possible to provide a program having the above-described effects.

Effects of the Invention

[0019] As described above, the present disclosure applies a median filter to the mixer result of the radar reflection signal and the local oscillation signal, and in removing interference spike noise from other devices, after applying the median filter, by reducing the phase noise of each frequency component, it is possible to improve the detection accuracy of the target.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

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Figure 9

Embodiments for Carrying Out the Invention

[0021] Embodiments of the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are examples of implementing the present disclosure, and the present disclosure is not limited to the following embodiments.

[0022] (Configuration of the Radar Target Detection Device of the Present Disclosure) The configuration of the radar target detection device of the present disclosure is shown in FIG. 5. The procedure of the interference removal process of the present disclosure is shown in FIG. 6. The radar target detection device R includes an oscillator 1, a transmission antenna 2, a reception antenna 3, a mixer 4, a median filter unit 5, a target detection unit 6, an interference detection unit 7, an interference removal unit 8, and a signal interpolation unit 9, and removes interference spike noise from another device I. The median filter unit 5, the target detection unit 6, the interference detection unit 7, the interference removal unit 8, and the signal interpolation unit 9 can be realized by installing the radar target detection program shown in FIG. 6 in a computer.

[0023] The oscillator 1 generates a radar transmission signal and a local oscillation signal. The transmission antenna 2 irradiates the radar transmission signal. The reception antenna 3 receives the radar reflection signal. The mixer 4 multiplies the radar reflection signal and the local oscillation signal. The median filter unit 5 applies a median filter to the multiplication result of the mixer 4 (step S1). The target detection unit 6 detects the target T based on the application results of the median filter unit 5 and the interference detection unit 7 to the signal interpolation unit 9.

[0024] The principle of the interference removal process of the present disclosure is shown in FIG. 7. In the upper left column of FIG. 7, when the radar target detection device R and the other device I intermittently operate periodically at mutually shifted timings, periodic interference spike noise from the other device I is generated. Different from the upper middle column of FIG. 7, when a linear filter such as a moving average filter or a low-pass filter is applied to the multiplication result of the mixer 4, the interference spike time width from the other device I is extended. In the upper middle column of FIG. 7, by applying a non-linear filter such as a median filter that employs the amplitude median value within a predetermined time range to the multiplication result of the mixer 4, the interference spike noise from the other device I is removed.

[0025] The interference detection unit 7 detects the interference spike noise in the multiplication result of the mixer 4 based on the magnitude of the difference between the multiplication result of the mixer 4 and the application result of the median filter unit 5 (step S2). In the upper right column of FIG. 7, the magnitude of the above difference is equal to or greater than a predetermined threshold during the interference spike noise detection period, and less than the predetermined threshold (substantially 0) during the non-detection period of the interference spike noise. This holds true not only when the amplitude of only the interference spike noise is large compared to the amplitudes other than the interference spike noise, but also when it is small.

[0026] In this way, by applying the median filter unit 5 to the multiplication result of the mixer 4, the interference spike noise from the other device I can be detected.

[0027] The interference removal unit 8 removes the multiplication result of the mixer 4 during the interference spike noise detection period (step S3). In the lower left column of FIG. 7, the multiplication result of the mixer 4 is removed during the interference spike noise detection period and maintained during the non-detection period of the interference spike noise.

[0028] In this way, the peak of the interference spike noise from the other device I can be removed. Here, the period of the interference spike noise from the other device I may be zero-padded.

[0029] The signal interpolation unit 9 interpolates the multiplication result of the mixer 4 during the interference spike noise removal period based on the multiplication results of the mixer 4 in the periods before and after the interference spike noise removal period (step S4). In the lower part of the middle column of FIG. 7, the multiplication result of the mixer 4 is interpolated during the interference spike noise removal period and maintained during the non-removal period of the interference spike noise.

[0030] In this way, it is possible to interpolate the period of the interference spike noise from the other device I. Here, the period of the interference spike noise from the other device I is a short period in which interpolation is easy.

[0031] (Specific example of the interference removal process of the present disclosure) That is, based on the magnitude of the difference between the multiplication result of the mixer 4 and the application result of the median filter unit 5, the interference spike noise in the multiplication result of the mixer 4 is detected. Then, the interference spike noise is removed by applying the signal interpolation unit 9 during the detection period of the interference spike noise without applying the median filter unit 5 to the multiplication result of the mixer 4. Hereinafter, the effects of the present disclosure different from the effects of the prior art will be described with reference to FIGS. 8 and 9.

[0032] Specific examples of the interference removal process of the present disclosure are shown in FIGS. 8 and 9. In the upper left column of FIG. 8, the multiplication result of the mixer 4 includes a fundamental wave, a second harmonic, and a third harmonic, and also includes interference spike noise from the other device I at time = 180 (the sampling interval is set to a somewhat wide interval). In the upper middle column of FIG. 8, the application result of the median filter unit 5 maintains the fundamental wave, the second harmonic, and the third harmonic, and removes the interference spike noise from the other device I at time = 180.

[0033] In the upper right column of FIG. 8, the application result of the interference detection unit 7 is that the fundamental wave, second harmonic, and third harmonic are almost removed, and the interference spike noise from the other device I at time = 180 is maintained and detected. In the lower left column of FIG. 8, the application result of the interference removal unit 8 is that the fundamental wave, second harmonic, and third harmonic are maintained, and the data during the interference spike noise period from the other device I at time = 180 is removed. In the middle lower column of FIG. 8, the application result of the signal interpolation unit 9 is that the fundamental wave, second harmonic, and third harmonic are maintained, and the data during the interference spike noise period from the other device I at time = 180 is interpolated.

[0034] In FIG. 4, the Fourier transform of the application result of the signal interpolation unit 9 includes the fundamental wave, second harmonic, and third harmonic, and does not include spurs such as the fourth harmonic and fifth harmonic. By applying the signal interpolation unit 9 during the interference spike noise detection period without applying the median filter unit 5 to the multiplication result of the mixer 4, no interaction occurs between the frequency components, so the relative phase between the frequency components is maintained and no spurs such as harmonics occur.

[0035] Thus, when removing the interference spike noise from the other device I by applying the median filter unit 5 to the processing result of the mixer 4 for the radar reflection signal and the local oscillation signal, the detection accuracy of the target T can be improved by reducing the phase noise of each frequency component after applying the median filter unit 5.

Industrial Applicability

[0036] The radar target detection device and radar target detection program of the present disclosure are applicable to microwave sensors using FSK, Doppler phenomenon, etc., and are particularly applicable to a large number of adjacent sensors (such as lighting control, home appliance control, parking lot control, and occupancy detection in individual toilet rooms).

Explanation of Signs

[0037] R: Radar target detection device T: Target I: Other device 1: Oscillator 2: Transmission antenna 3: Receiving antenna 4: Mixer 5: Median filter section 6: Target detection section 7: Interference detection section 8: Interference removal section 9: Signal interpolation section

Claims

1. An oscillator that generates a radar transmission signal and a local oscillation signal, A transmission antenna that irradiates the radar transmission signal, A reception antenna that receives the radar reflection signal, A mixer that multiplies the radar reflection signal and the local oscillation signal in the time domain, A median filter unit that applies a median filter to the multiplication result of the mixer in the time domain in the time domain, A target detection unit that detects a target based on the application result of the median filter unit in the time domain in the time domain, A radar target detection device comprising: An interference detection unit that detects interference spike noise in the multiplication result of the mixer in the time domain based on the magnitude of the difference between the multiplication result of the mixer in the time domain and the application result of the median filter unit in the time domain, A radar target detection device, further comprising the above.

2. An interference removal unit that removes the multiplication result of the mixer in the time domain during the detection period of the interference spike noise, The radar target detection device according to claim 1, further comprising the above.

3. A signal interpolation unit that interpolates the multiplication result of the mixer in the time domain during the removal period of the interference spike noise based on the multiplication result of the mixer in the time domain in the periods before and after the removal period of the interference spike noise, The radar target detection device according to claim 2, further comprising the above.

4. A radar target detection program for causing a computer to execute the median filter procedure, target detection procedure, and interference detection procedure performed by the median filter unit, target detection unit, and interference detection unit included in the radar target detection device according to any one of claims 1 to 3.

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