JP2012088238A - On-vehicle radar device and detection method of electric wave interference for on-vehicle radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect an occurrence of electric wave interference from another radar, etc., even though a noise level changes or an instrumental difference exists.SOLUTION: A detection method includes: a transmission section (10) for transmitting modulation waves having frequencies repeating the rise/fall; a receiving section (20) for receiving a reflection wave of which the modulation waves are reflected by an object; and a signal processing section (30) for frequency-analyzing a beat signal having the frequency difference between a transmission wave and the reflection wave, calculating peak frequencies from the frequency analyzing result respective at the rising/falling of frequency, and calculating a distance of the object and a relative speed from both peak frequencies. The signal processing section includes an interference detection section (34) which compares a noise level at the rise time and a noise level at the fall time in the frequency analysis of the respective beat signals at the rising/falling of frequency, and when one of noise levels has a difference of a predetermined value or larger as compared with another noise level, the occurrence of the interference caused by an externally disturbed electric wave is determined, and the signal is output as an interference detection signal.

Description

  The present invention relates to an in-vehicle radar device that can accurately detect the occurrence of interference due to disturbance radio waves, and a radio wave interference detection method for an in-vehicle radar device.

  An on-vehicle radar device mounted on a vehicle or the like has a function of measuring an inter-vehicle distance and a relative speed with another vehicle, and controls vehicles such as an ACC (Adaptive Cruise Control) or a collision reduction / prevention device with a preceding vehicle. Used in equipment.

  A frequency-modulated continuous wave (FMCW: Frequency Modulated Continuous Wave) is often used in the on-vehicle radar device for such applications (see, for example, Non-Patent Document 1).

  Here, as one of the problems of the on-vehicle radar device, when a radio wave is received from another radar or other radio wave transmitting device, a signal of a specific frequency or spike on the beat signal due to the disturbance radio wave is received. The noise is superimposed. In the case of an FMCW radar device, a disturbance signal is often affected only by the moment when the disturbance radio wave and the transmission frequency are close to each other, resulting in a beat signal (see, for example, FIG. 2 described later in detail).

  When the beat signal affected by the disturbance radio wave is subjected to frequency analysis, the influence of the disturbance radio wave appears as a form in which the reception level increases not only at a specific frequency but at any frequency (for example, described in detail later). (See FIG. 3). That is, the noise level increases at every frequency. Thus, when the noise level rises at any frequency, the peak of the beat frequency corresponding to the reflected wave from the object to be detected may be buried in the noise level and cannot be detected.

  This state will be referred to as “a state in which interference has occurred” in the following description. If the state in which interference occurs continues, normal operation of the in-vehicle radar device cannot be expected. For this reason, when interference occurs, it is necessary to notify this state from the in-vehicle radar device to the vehicle control device, cancel the operation until the interference disappears, or notify the driver.

  Therefore, there is a conventional technique for measuring the reception level every time and determining that interference has occurred when the current reception level changes to a threshold value or more with respect to the reception level at the time of the previous measurement (for example, Patent Document 1). reference).

JP 2007-225602 A

Radar Technology IEICE ISBN4-88552-049-5

However, the prior art has the following problems.
Among the reception levels when the beat signal is subjected to frequency analysis, the noise level is generated in the circuit of the in-vehicle radar device. In particular, in a high frequency circuit, the noise level increases or decreases due to heat. In addition, there are instrumental differences among in-vehicle radar devices, and the magnitude of the noise level differs for each in-vehicle radar device. If these noise level changes and instrumental differences are large, it becomes difficult to determine a threshold value when determining that interference has occurred. On the other hand, there is a problem of increasing the cost in order to reduce the change in noise level and instrumental error as much as possible.

  In addition, this prior art is to detect the occurrence of interference by a change from a state in which no interference has occurred to a state in which interference has occurred, and when interference has already occurred immediately after the start of observation, I can't catch this change.

  The present invention has been made in order to solve the above-described problems. Even if there is a change in noise level or instrumental error, or even if interference occurs immediately after the start of observation, the present invention can be used with high accuracy. An object of the present invention is to obtain an FMCW in-vehicle radar device capable of detecting the occurrence of radio wave interference from a radar or the like, and a radio wave interference detection method for the in-vehicle radar device.

  An in-vehicle radar device according to the present invention includes a transmitter that transmits a modulated wave having a frequency that repeats ascending and descending, and a reflection of the transmitted modulated wave reflected by an object that is a detection target of distance and relative speed. Frequency analysis of the receiving unit that receives the wave and the beat signal having a frequency difference between the frequency of the transmitted wave and the reflected wave, and calculates the peak frequency from the frequency analysis results at the time of frequency rise and fall, In an FMCW in-vehicle radar device having a signal processing unit that calculates a distance and a relative speed of an object from a peak frequency and a peak frequency when the frequency is lowered, the signal processing unit performs frequency analysis of a beat signal when the frequency is increased Compare the rising noise level in the frequency with the falling noise level in the frequency analysis of the beat signal when the frequency drops. If any one of the noise levels has a difference of more than a predetermined value with respect to the other noise level, it is determined that interference due to disturbance radio waves from the outside of the radar has occurred, and the interference is output as an interference detection signal. It has a detection part.

  The radio wave interference detection method for an on-vehicle radar device according to the present invention includes a transmission step of transmitting a modulated wave having a frequency that repeatedly rises and falls, and the transmitted modulated wave is a target for detecting distance and relative speed. The receiving step for receiving the reflected wave reflected by the target object, and the frequency analysis of the beat signal having the frequency difference between the frequency of the transmitted wave and the frequency of the reflected wave, and from the frequency analysis results when the frequency is rising and falling respectively A radio wave interference detection method for an in-vehicle radar device of the FMCW system comprising a signal processing step for calculating a peak frequency and calculating a distance and a relative speed of an object from the peak frequency when the frequency is increased and the peak frequency when the frequency is decreased In the signal processing step, the rising noise level in the frequency analysis of the beat signal when the frequency is increased and the frequency of the beat signal when the frequency is decreased Compared to the falling noise level in the analysis, if the noise level of either the rising noise level or the falling noise level is different from the other noise level by a predetermined value or more, It is determined that the interference due to the disturbance electric wave has occurred, and has an interference detection step of outputting as an interference detection signal.

  According to the on-vehicle radar device and the radio wave interference detection method for the on-vehicle radar device according to the present invention, interference is generated by comparing the noise levels at the time of frequency increase and frequency decrease at one or a plurality of transmission frequencies. By detecting, even if there is a change in noise level or instrumental difference, or even if interference occurs immediately after the start of observation, it is possible to accurately detect the occurrence of radio wave interference from other radars. An FMCW in-vehicle radar device and a radio wave interference detection method for the in-vehicle radar device can be obtained.

It is a block diagram of the ACC system using the vehicle-mounted radar apparatus in Embodiment 1 of this invention. FIG. 6 is a diagram of Case 1 showing temporal changes in transmission frequency and disturbance radio wave frequency and beat signals at that time when a disturbance radio wave is received in the in-vehicle radar device according to the first embodiment of the present invention. It is the figure which showed the FFT result of the beat signal in the condition of case 1 of previous FIG. 2 in Embodiment 1 of this invention. FIG. 5 is a diagram of Case 2 showing temporal changes in the transmission frequency and the frequency of the disturbance radio wave and the beat signal at that time when the disturbance radio wave is received in the in-vehicle radar device according to the first embodiment of the present invention. It is the figure which showed the FFT result of the beat signal in the condition of case 2 of previous FIG. 4 in Embodiment 1 of this invention. It is the figure which showed the Hanning window used as a window function in Embodiment 1 of this invention. FIG. 6 is a diagram of Case 3 showing temporal changes in transmission frequency and disturbance radio frequency and beat signals at that time when a disturbance radio wave is received in the in-vehicle radar device according to the first embodiment of the present invention. It is the figure which showed the FFT result of the beat signal in the condition of case 3 of previous FIG. 7 in Embodiment 1 of this invention. It is a flowchart which shows a series of processes of the interference detection part in the signal processing part of Embodiment 1 of this invention. FIG. 6 is a diagram of Case 4 showing a temporal change in transmission frequency and disturbance radio frequency when a disturbance radio wave is received and a beat signal at that time in the in-vehicle radar device according to the second embodiment of the present invention. It is the figure which showed the FFT result of the beat signal in the condition of case 4 of previous FIG. 10 in Embodiment 2 of this invention. FIG. 6 is a diagram of Case 5 showing a temporal change in transmission frequency and disturbance radio frequency and a beat signal at that time when a disturbance radio wave is received in the in-vehicle radar device according to the second embodiment of the present invention. It is the figure which showed the FFT result of the beat signal in the condition of case 5 of the previous FIG. 12 in Embodiment 2 of this invention. FIG. 10 is a diagram of Case 6 showing temporal changes in the transmission frequency and the frequency of the disturbance radio wave and the beat signal at that time when the disturbance radio wave is received in the in-vehicle radar device according to the second embodiment of the present invention. It is the figure which showed the FFT result of the beat signal in the condition of case 6 of the previous FIG. 14 in Embodiment 2 of this invention. It is a flowchart which shows a series of processes of the interference detection part in the signal processing part of Embodiment 2 of this invention.

  Hereinafter, preferred embodiments of an on-vehicle radar device and a radio wave interference detection method for an on-vehicle radar device according to the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of an ACC system that uses an in-vehicle radar device according to Embodiment 1 of the present invention. In the first embodiment, measurement is performed with two types of modulation, that is, frequency increase and decrease.

  The ACC system shown in FIG. 1 includes an on-vehicle radar device 1, a user interface device 101, an engine control ECU 102, and a brake control ECU 103, which are connected to each other via an in-house LAN 110.

  The in-vehicle radar device 1 includes a transmission unit 10, a reception unit 20, and a signal processing unit 30. Therefore, the internal configuration and operation of the on-vehicle radar device 1 of the present invention will be described in detail in the order of the transmission unit 10, the reception unit 20, and the signal processing unit 30.

  The transmission unit 10 includes a VOC 11, a distributor 12, and a transmission antenna 13. The VOC 11 controls the increase and decrease of the frequency of the transmission signal based on a command from the signal processing unit 30. The distributor 12 distributes the transmission signal generated by the VCO 11 to the transmission antenna 13 and the mixer 22 in the receiving unit 20 described later. The transmission antenna 13 radiates a transmission wave to the outside of the on-vehicle radar device.

  The receiving unit 20 includes a receiving antenna 21, a mixer 22, an amplifier 23, a low-pass filter 24, and an A / D converter 25. The receiving antenna 21 receives a reflected wave reflected by the object 120 detected by the in-vehicle radar device 1 as a received signal. In the first embodiment, the case of having two receiving antennas is illustrated.

  The mixer 22 mixes the reception signal received by the reception antenna 21 with the transmission signal distributed by the distributor 12, and generates a beat signal corresponding to the distance, speed, and direction of the object 120. The amplifier 23 amplifies the beat signal generated by the mixer 22. The low pass filter 24 removes unnecessary high frequency components from the amplified signal. The A / D converter 25 converts the output signal of the low-pass filter from an analog signal to a digital signal.

  Furthermore, the signal processing unit 30 corresponds to a CPU that performs signal processing, and includes a window function processing unit 31, an FFT processing unit 32, an object calculation unit 33, an interference detection unit 34, and an ACC processing unit 35. The window function processing unit 31 applies a window function to a digital signal obtained by A / D converting the beat signal corresponding to each receiving antenna 21. The FFT processing unit 32 performs fast Fourier transform (FFT) on the signal output from the window function processing unit 31.

  The object calculation unit 33 performs peak detection from the FFT results of the beat signal when the transmission frequency is increased and the beat signal when the transmission frequency is decreased, which is output from the FFT processing unit 32. Further, the target object calculation unit 33 calculates the distance, speed, and direction of the target object 120 from the sum or difference of the phase difference or amplitude of the peak frequency component when the transmission frequency increases and the peak frequency component when the transmission frequency decreases. Note that specific methods for calculating the distance, speed, and direction are described in Non-Patent Document 1, Patent Document 1, and the like described above.

  The interference detection unit 34 performs an interference detection process from the FFT result output by the FFT processing unit 32. The function of the interference detection unit 34 is a technical feature of the present invention, and will be specifically described later with reference to the flowchart of FIG.

  Further, the ACC processing unit 35 calculates an ACC control signal based on the processing results of the object calculation unit 33 and the interference detection unit 34. Specifically, information is transmitted from the ACC processing unit 35 through the in-vehicle LAN 110, and the user interface device 101, the engine control ECU 102, and the brake control ECU 103 operate to perform acceleration / deceleration control and the like. At this time, when the interference detection unit 34 detects the occurrence of interference, the ACC processing unit 35 interrupts the ACC control or informs the user that the ACC control is interrupted via the user interface device 101. Or notify.

  Each device connected to the vehicle-mounted radar device 1 via the in-vehicle LAN 110 has the following functions. The user interface device 101 notifies the user of information according to information from the in-vehicle radar device 1. The engine control ECU 102 performs engine control based on the processing result calculated by the ACC processing unit 35. Further, the brake control ECU 103 performs brake control based on the processing result calculated by the ACC processing unit 35.

  The point of the present invention is how to detect the “state in which interference has occurred”, and will be described below with a focus on the function of the interference detection unit 34 that is a technical feature of the present invention.

  As a case where interference occurs in the in-vehicle radar device, there may be a case where radio waves are received from the in-vehicle radar device mounted on another vehicle. Generally, there are FMCW method, CW method, pulse method, etc. for the transmission wave of the on-vehicle radar device. Of these, the pulse system transmits radio waves only at very short pulse intervals, and is therefore considered to have little effect on other radars.

Therefore, a case where an FMCW disturbance radio wave is received will be collectively described in Embodiment 1 as Case 1 to Case 3.
The case of receiving a CW disturbance radio wave will be described later as Embodiment 4 to Case 6 in Embodiment 2.

[Case 1]
FIG. 2 is a diagram of Case 1 showing the temporal change of the transmission frequency and the frequency of the disturbance radio wave and the beat signal at that time when the disturbance radio wave is received in the in-vehicle radar device according to the first embodiment of the present invention. It is. Specifically, FIG. 2 shows that in the state of receiving a reflected wave from an object having a certain distance y [m] and a relative velocity of 0 [m / s], the transmission wave of another FMCW radar is used as a disturbance radio wave. This shows a case in which interference with the frequency of disturbance radio waves occurs only when the frequency is lowered.

  The frequency of the beat signal by the reflected wave of the object at this time is the same frequency when the frequency is increased and when the frequency is decreased because the relative speed is zero. Here, a signal in which a very small random noise is superimposed on a sin wave is schematically illustrated. In the FMCW in-vehicle radar device, only a necessary low frequency region is extracted from the beat signal by a low pass filter. For this reason, the influence of the disturbance radio wave appears only in the part where the transmission frequency and the frequency of the disturbance radio wave are close.

  FIG. 3 is a diagram showing the FFT result of the beat signal in the case 1 of FIG. 2 in the first embodiment of the present invention. In the situation shown in FIG. 2, the interference with the frequency of the disturbance radio wave occurs only when the frequency is lowered. Therefore, as shown in FIG. 3, when the frequency is increased, there is no influence of disturbance radio waves, and only when the frequency is decreased, the noise level is increased due to the influence of disturbance radio waves.

[Case 2]
FIG. 4 is a diagram of Case 2 showing the time change of the transmission frequency and the frequency of the disturbance radio wave and the beat signal at that time when the disturbance radio wave is received in the in-vehicle radar device according to the first embodiment of the present invention. It is. Specifically, FIG. 4 shows the transmission of another FMCW radar in the same manner as in the case 1 in a state where a reflected wave from an object having a certain distance y [m] and a relative speed of 0 [m / s] is received. When a wave is received as a disturbance radio wave, the case where the frequency of the disturbance radio wave and interference occur both when the frequency is rising and when the frequency is falling is shown.

  FIG. 5 is a diagram showing the FFT result of the beat signal in the case 2 of FIG. 4 in the first embodiment of the present invention. In the case of the situation shown in FIG. 4, the waveform of the beat signal is disturbed at a portion where the transmission frequency and the frequency of the disturbance radio wave are close both when the frequency is increased and when the frequency is decreased. For this reason, the noise level of the FFT result of the beat signal increases both when the frequency is increased and when the frequency is decreased.

  However, as shown in the beat signal diagram of FIG. 4, if the position of the noise appearing in the beat signal differs between when the frequency is increased and when the frequency is decreased, the magnitude of the noise changes depending on the window function. For this reason, as shown in FIG. 5, a difference occurs between the noise levels when the frequency is increased and when the frequency is decreased. FIG. 6 is a diagram showing a Hanning window used as a window function in Embodiment 1 of the present invention.

[Case 3]
FIG. 7 is a diagram of Case 3 showing temporal changes in the transmission frequency and the frequency of the disturbance radio wave and the beat signal at that time when the disturbance radio wave is received in the in-vehicle radar device according to the first embodiment of the present invention. It is. Specifically, FIG. 7 shows other FMCW radars in the same manner as cases 1 and 2 in the state of receiving a reflected wave from an object having a certain distance y [m] and a relative velocity of 0 [m / s]. When the transmitted wave is received as a disturbance radio wave, the frequency of the disturbance radio wave and the interference are generated both when the frequency is increased and when the frequency is decreased.

  However, unlike Case 2 shown in FIG. 4, FIG. 7 shows a case where interference occurs in substantially the same frequency band when the frequency is increased and when the frequency is decreased. FIG. 8 is a diagram showing the FFT result of the beat signal in the case 3 of FIG. 7 in the first embodiment of the present invention. In case 3, as shown in FIG. 8, the noise level of the FFT result of the beat signal increases by the same amount both when the frequency is increased and when the frequency is decreased. However, the frequency of occurrence of such interference is considered to be very low.

As described above, in the first embodiment when the disturbance radio wave is FMCW, it is possible to detect the occurrence of interference by detecting the following conditions.
[Interference judgment condition A] The difference or ratio of the noise level of the FFT result of the beat signal when the frequency is increased and when the frequency is decreased is larger than a predetermined value.

  Then, next, a series of operations for detecting interference in the ACC system using the in-vehicle radar device according to the first embodiment will be described using a flowchart. FIG. 9 is a flowchart illustrating a series of processes of the interference detection unit 34 in the signal processing unit according to the first embodiment of the present invention.

  First, in step S101, the interference detection unit 34 calculates a noise level from the FFT result of the beat signal at the time of the frequency increase output from the FFT processing unit 32. Hereinafter, this is referred to as a noise level when the frequency is increased.

  The calculation method of the noise level includes the average of all the data of the FFT result, the average of the data after removing the peak portion above a certain reception level, and the data of the frequency domain portion outside the detection distance / velocity range of the object 120. Average (for example, refer to JP 2008-107280 A) and the like.

  Next, in step S102, the interference detection unit 34 calculates the noise level from the FFT result of the beat signal at the time of the frequency decrease output from the FFT processing unit 32, as in step S101. Hereinafter, this is referred to as a noise level when the frequency drops.

  Next, in step S103, the interference detection unit 34 compares the above-described interference determination condition A with respect to the noise level when the frequency is increased and the noise level when the frequency is decreased. If either one does not exceed the predetermined multiple of the other, the interference detection unit 34 proceeds to step S104, determines that no interference has occurred, and notifies the ACC processing unit 35 that there is no interference. Then, the number of times of interference detection is reset to 0, and a series of interference detection processing is terminated.

  On the other hand, when either one of the noise level at the time of the frequency increase and the noise level at the time of the frequency decrease becomes equal to or more than the predetermined multiple of the other in step S103, the interference detection unit 34 proceeds to step S105 and performs interference. And the number of interference detections is set to +1.

  Next, in step S106, the interference detection unit 34 determines whether or not the number of times of interference detection exceeds a predetermined value n. If it has exceeded, in step S107, the interference detection unit 34 notifies the ACC processing unit 35 to cancel the ACC, and ends the series of interference detection processing.

  On the other hand, if the number of times of interference detection is n or less in the previous step S106, the interference detection unit 34 maintains the past measurement result in step S108, assuming that the state in which the interference has not occurred has yet been determined. Then, the ACC processing unit 35 is notified to continue the ACC, and a series of interference detection processes are terminated.

  As described above, according to the first embodiment, the occurrence of interference is detected by comparing the noise levels when the frequency is increased and when the frequency is decreased. If it is determined that there is a possibility that a malfunction occurs in the radar operation due to the continued detection of the occurrence of interference and the ACC operation may be inconvenient, the ACC operation is canceled and the driver is informed. You can be notified.

  As a result, the FMCW method can accurately detect the occurrence of radio wave interference from other radars even if there is a noise level change or instrumental difference, or even if interference occurs immediately after the start of observation. In-vehicle radar device can be obtained.

Embodiment 2. FIG.
In the first embodiment, three cases of Case 1 to Case 3 have been described in the case of receiving FMCW disturbance radio waves. On the other hand, in the second embodiment, three cases of Case 4 to Case 6 will be described in the case of receiving a CW disturbance radio wave. The overall configuration in the second embodiment is the same as the configuration in FIG. 1 in the first embodiment, and a description thereof will be omitted.

[Case 4]
FIG. 10 is a diagram of Case 4 showing the time change of the transmission frequency and the frequency of the disturbance radio wave and the beat signal at that time when the disturbance radio wave is received in the in-vehicle radar device according to the second embodiment of the present invention. It is. Specifically, FIG. 10 shows that a CW wave without FM modulation is received as a disturbance radio wave in a state in which a reflected wave from an object having a certain distance y [m] and a relative velocity of 0 [m / s] is received. In this case, the frequency and interference of the disturbance radio wave are generated both when the frequency is increased and when the frequency is decreased.

  FIG. 11 is a diagram showing an FFT result of the beat signal in the case 4 of FIG. 10 in the second embodiment of the present invention. In the case of the situation shown in FIG. 10, the beat signal waveform is disturbed in the same frequency band in the same frequency band both when the frequency is increased and when the frequency is decreased. For this reason, the noise level of the FFT result of the beat signal increases by the same amount both when the frequency is increased and when the frequency is decreased. Therefore, from this result alone, the presence or absence of interference cannot be detected.

[Case 5]
FIG. 12 is a diagram of Case 5 showing the time change of the transmission frequency and the frequency of the disturbance radio wave and the beat signal at that time when the disturbance radio wave is received in the in-vehicle radar device according to the second embodiment of the present invention. It is. Specifically, FIG. 12 shows that a CW wave without FM modulation is received as a disturbance radio wave in a state in which a reflected wave from an object having a certain distance y [m] and a relative velocity of 0 [m / s] is received. In this case, by using two types of transmission frequencies (first pattern and second pattern) having different modulation bands, the frequency of disturbance radio waves and interference are generated only at one transmission frequency.

  FIG. 13 is a diagram showing the FFT result of the beat signal in the case 5 of FIG. 12 in the second embodiment of the present invention. In the case of the situation shown in FIG. 12, when the first frequency rises and when the first frequency falls, the waveform of the beat signal is disturbed in the same frequency band in the portion where the transmission frequency and the frequency of the disturbance radio wave are close. The noise level of the FFT result of the beat signal increases by the same amount. On the other hand, since no interference occurs when the second frequency is increased or when the second frequency is decreased, the noise level of the FFT result of the beat signal does not increase both when the frequency is increased and when the frequency is decreased.

  Accordingly, as shown in FIG. 12, two types of transmission frequencies with different modulation bands are used, and interference occurs only at one transmission frequency, so that a CW wave without FM modulation is received as a disturbance radio wave. The presence or absence of interference at the time can also be reliably detected.

[Case 6]
FIG. 14 is a diagram of Case 6 showing the time change of the transmission frequency and the frequency of the disturbance radio wave and the beat signal at that time when the disturbance radio wave is received in the in-vehicle radar device according to the second embodiment of the present invention. It is. Specifically, FIG. 14 shows that a CW wave without FM modulation is received as a disturbance radio wave in a state where a reflected wave from an object having a certain distance y [m] and a relative velocity of 0 [m / s] is received. In this case, by using two types of transmission frequencies (first pattern and second pattern) having different modulation widths, the frequency of disturbance radio waves and interference are generated only at one transmission frequency.

  FIG. 15 is a diagram showing the FFT result of the beat signal in the case 6 of FIG. 14 in the second embodiment of the present invention. In the case of the situation shown in FIG. 14, when the first frequency is increased and the first frequency is decreased, the waveform of the beat signal is disturbed in the same frequency band in the portion where the transmission frequency and the frequency of the disturbance radio wave are close. The noise level of the FFT result of the beat signal increases by the same amount. On the other hand, since no interference occurs when the second frequency is increased or when the second frequency is decreased, the noise level of the FFT result of the beat signal does not increase both when the frequency is increased and when the frequency is decreased.

  Therefore, as shown in FIG. 14, when two types of transmission frequencies having different modulation widths are used and interference occurs only at one transmission frequency, two types of transmissions having different modulation bands are used. As in the previous case 5 using the frequency, it is possible to reliably detect the presence or absence of interference when a CW wave without FM modulation is received as a disturbance radio wave.

  As shown in FIG. 14 above, when the modulation widths are different, when the frequency of the disturbance radio wave is present in the portion where the modulation bands overlap, the FFT results of all four beat signals are obtained. The noise level will increase. However, since the location where the waveform is disturbed by the disturbance radio wave on the beat signal differs between different modulation bands, a difference occurs in the noise level as shown in FIG. Therefore, such interference caused by disturbance radio waves can be reliably detected.

Therefore, considering both the case where the FMCW disturbance radio wave is received as in the first embodiment and the case where the CW wave disturbance wave without FM modulation is received as in the second embodiment, the following is considered. By detecting such conditions, it is possible to detect the occurrence of interference in either case.
[Interference occurrence condition B] In different modulation widths and modulation bands, the difference or ratio of the noise level of the FFT result of the beat signal when the first frequency of the first pattern is increased and when the first frequency is decreased is larger than a predetermined value. Or the difference or ratio of the noise level of the FFT result of the beat signal when the second frequency of the second pattern is increased and when the second frequency is decreased is greater than a predetermined value [interference occurrence condition C]. In the modulation width and modulation band, whether the difference or ratio of the noise level of the FFT result of the beat signal when the first frequency of the first pattern rises and the second frequency of the second pattern rises is greater than a predetermined value, Alternatively, the difference or ratio of the noise level of the FFT result of the beat signal when the first frequency of the first pattern is lowered and when the second frequency of the second pattern is lowered is larger than a predetermined value.

  That is, by determining the interference occurrence condition B, it is possible to detect the presence or absence of interference when receiving the FMCW disturbance radio wave as in the first embodiment, and by determining the interference occurrence condition C, the present embodiment Thus, it is possible to detect the presence or absence of interference when a disturbance wave of a CW wave without FM modulation is received as in the second embodiment.

  Then, next, a series of operations for detecting interference in the ACC system using the in-vehicle radar device according to the second embodiment will be described using a flowchart. FIG. 16 is a flowchart showing a series of processes of the interference detection unit 34 in the signal processing unit according to the second embodiment of the present invention.

  In the flowchart of FIG. 16, four types of modulation of increasing and decreasing frequencies with different modulation bands as shown in FIG. 12 or 4 of increasing and decreasing frequencies with different modulation widths as shown in FIG. Measurements will be performed with different types of modulation. Here, as shown in FIG. 12 or FIG. 14, the modulation order is a first frequency increase, a first frequency decrease, a second frequency increase, and a second frequency decrease.

  First, in step S <b> 201, the interference detection unit 34 calculates a noise level from the FFT result of the beat signal at the time of the first frequency increase output from the FFT processing unit 32. Hereinafter, this is referred to as a noise level when the first frequency is increased.

  Next, in step S <b> 202, the interference detection unit 34 calculates a noise level from the FFT result of the beat signal at the time of the first frequency drop output from the FFT processing unit 32. Hereinafter, this is referred to as a noise level when the first frequency is lowered.

  Next, in step S <b> 203, the interference detection unit 34 calculates a noise level from the FFT result of the beat signal at the time of the second frequency increase output from the FFT processing unit 32. Hereinafter, this is referred to as a noise level when the second frequency is increased.

  Next, in step S <b> 204, the interference detection unit 34 calculates a noise level from the FFT result of the beat signal at the time of the second frequency decrease output from the FFT processing unit 32. Hereinafter, this is referred to as a noise level when the second frequency is lowered.

  Next, in step S205, the interference detection unit 34 determines the noise level when the first frequency is increased, the noise level when the first frequency is decreased, the noise level when the second frequency is increased, and the noise level when the second frequency is decreased. The interference determination condition B described above is compared for the noise level. Then, when the interference determination condition B is not satisfied, the interference detection unit 34 proceeds to step S206.

  In step S206, the interference detection unit 34 determines the noise level when the first frequency is increased, the noise level when the first frequency is decreased, the noise level when the second frequency is increased, and the noise when the second frequency is decreased. For the level, the above-described interference determination condition C is compared. If the interference determination condition C is not satisfied, the interference detection unit 34 proceeds to step S207, determines that no interference has occurred, notifies the ACC processing unit 35 that there is no interference, and sets the number of interference detections to 0. To complete the series of interference detection processing.

  On the other hand, when the interference determination condition B is satisfied in the previous step S205 or when the interference determination condition C is satisfied in the previous step S206, the interference detection unit 34 proceeds to step S208 and interference occurs. It is determined that the number of times of interference detection is +1.

  Next, in step S209, the interference detection unit 34 determines whether or not the number of times of interference detection exceeds a predetermined value n. If it has exceeded, in step S210, the interference detection unit 34 notifies the ACC processing unit 35 to cancel the ACC, and ends a series of interference detection processing.

  On the other hand, when the number of times of interference detection is n or less in the previous step S209, in step S211, the interference detection unit 34 maintains the past measurement result, assuming that the state in which the interference has not yet been determined. Then, the ACC processing unit 35 is notified to continue the ACC, and a series of interference detection processes are terminated.

  As described above, according to the second embodiment, not only the noise level of the FFT result of the beat signal when the frequency is increased and when the frequency is decreased, but also when the first and second frequencies with different modulation widths are increased. By comparing the noise levels when the first and second frequencies are lowered, it is possible to detect the occurrence of interference due to the CW wave that could not be determined in the first embodiment.

  Instead of determining whether the interference determination condition B and the interference determination condition C as shown in FIG. 16 are satisfied, the rising noise level, the falling noise level in the first pattern, and the rising noise level in the second pattern Compare the four noise levels of the descent noise level, and if any one of the noise levels is more than a predetermined value with respect to the other noise levels, the interference caused by disturbance radio waves from the outside of the radar It is also possible to determine that has occurred.

  DESCRIPTION OF SYMBOLS 1 Vehicle-mounted radar apparatus, 10 transmission part, 11 VCO, 12 divider | distributor, 13 transmission antenna, 20 reception part, 21 reception antenna, 22 mixer, 23 amplifier, 24 low-pass filter, 25 A / D converter, 30 signal processing part , 31 Window function processing unit, 32 FFT processing unit, 33 Object calculation unit, 34 Interference detection unit, 35 ACC processing unit, 101 User interface device, 102 Engine control ECU, 103 Brake control ECU, 110 In-vehicle LAN, 120 Object .

Claims (4)

A transmitter that transmits a modulated wave having a frequency that repeats rising and falling; and
A receiving unit that receives the reflected wave reflected by the object that is the detection target of the distance and the relative velocity of the modulated wave transmitted;
Analyzes the beat signal having a frequency difference between the frequency of the transmitted wave and the frequency of the reflected wave, calculates the peak frequency from the frequency analysis results when the frequency is rising and falling, and calculates the peak frequency and frequency when the frequency is rising In an FMCW in-vehicle radar device comprising: a signal processing unit that calculates a distance and a relative speed of the object from a peak frequency when descending;
The signal processing unit compares the rising noise level in the frequency analysis of the beat signal when the frequency is increased with the falling noise level in the frequency analysis of the beat signal when the frequency is decreased, and the rising noise level or the falling noise level. If any one of the noise levels is more than a predetermined value with respect to the other noise level, it is determined that interference due to disturbance radio waves from the outside of the radar has occurred, and interference detection is output as an interference detection signal. A vehicle-mounted radar device characterized by comprising a part. The on-vehicle radar device according to claim 1,
The transmission unit transmits a modulated wave including a first pattern and a second pattern configured with different frequency modulation widths or different frequency modulation bands at the time of frequency increase and frequency decrease,
The interference detection unit compares four noise levels of a rising noise level and a falling noise level in the first pattern, and a rising noise level and a falling noise level in the second pattern, and any one or more of them. When there is a difference of more than a predetermined value with respect to other noise levels, it is determined that interference due to disturbance radio waves from outside the radar has occurred, and is output as an interference detection signal. Radar equipment. A transmission step of transmitting a modulated wave having a frequency that repeats rising and falling; and
A receiving step of receiving the reflected wave reflected by the object whose distance and relative velocity are detected by the transmitted modulated wave;
Analyzes the beat signal having a frequency difference between the frequency of the transmitted wave and the frequency of the reflected wave, calculates the peak frequency from the frequency analysis results when the frequency is rising and falling, and calculates the peak frequency and frequency when the frequency is rising In the radio wave interference detection method for a vehicle-mounted radar device of the FMCW system, comprising: a signal processing step for calculating a distance and a relative speed of the object from a peak frequency at the time of descent;
The signal processing step compares the rising noise level in the frequency analysis of the beat signal when the frequency is increased with the falling noise level in the frequency analysis of the beat signal when the frequency is decreased, and the rising noise level or the falling noise level. If any one of the noise levels is more than a predetermined value with respect to the other noise level, it is determined that interference due to disturbance radio waves from the outside of the radar has occurred, and interference detection is output as an interference detection signal. A radio wave interference detection method for an on-vehicle radar device, comprising: a step. The radio wave interference detection method for an on-vehicle radar device according to claim 3,
The transmitting step transmits a modulated wave including a first pattern and a second pattern configured with different frequency modulation widths or different frequency modulation bands when the frequency is increased and decreased.
The interference detection step compares the four noise levels of the rising noise level and falling noise level in the first pattern, and the rising noise level and falling noise level in the second pattern, and any one or more of them. When there is a difference of more than a predetermined value with respect to other noise levels, it is determined that interference due to disturbance radio waves from outside the radar has occurred, and is output as an interference detection signal. Method for detecting radio wave interference for radar equipment.

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