JP5097467B2 - Automotive radar equipment - Google Patents

Description

  The present invention relates to an on-vehicle radar device, and more particularly to an on-vehicle radar device used in a preventive safety system such as an inter-vehicle distance warning system, an adaptive cruise control system, and a pre-crash system.

  In recent years, there has been a great interest in automobile safety technology. In response, various systems have begun to be put into practical use mainly by automobile-related companies. Among these, a system for avoiding a collision such as an inter-vehicle distance warning system, an adaptive cruise control system, a pre-crash system, and a system for reducing the impact at the time of the collision are particularly well known.

  When constructing these systems, there is an in-vehicle radar device as one of devices for measuring a distance to a target, a relative speed, and the like. This in-vehicle radar device radiates radio waves and receives reflected waves from targets such as vehicles and obstacles, detects the propagation time of radio waves, signal intensity of reflected waves, Doppler shift of frequency, etc. A method of measuring the distance to the target and the relative speed based on the information is known.

  It is known that there are various types of modulation methods used in such an on-vehicle radar device. Particularly, the FMCW (Frequency Modulated Continuous Wave) method and the two-frequency CW (Continuous Wave) method are famous. It is.

  First, the operating principle of the FMCW in-vehicle radar device will be briefly described with reference to FIG.

FIG. 1A shows an example of a frequency pattern of transmission / reception waves. Radio waves subjected to triangular wave modulation are transmitted so that the frequency repeats increasing and decreasing linearly on the time axis. A reflected wave reflected by the transmission signal is received and mixed with a local signal having the same frequency as the transmission signal, thereby obtaining a beat signal as shown in FIG. 1B. When this beat signal is subjected to FFT processing in a specific section (for example, section Td in FIG. 1B), a target peak frequency f _b D as shown in FIG. 1C is obtained. From this target peak frequency, the distance R to the target and the relative velocity V are obtained based on the principle described below. In FIG. 1A, the transmission wave (Tx) is drawn with a solid line, and the reception wave (Rx) is drawn with a broken line.

  The received signal reflected back from the target has a delay time τ (= 2R proportional to the distance R to the target, that is, the time required for the radio wave to make a round trip to the target with respect to the transmitted signal. / C) occurs. Here, c is the speed of light.

  Further, the Doppler shift is performed by a frequency fd (= −2 Vf / c) proportional to the relative speed V between the target and the target. Here, f is the frequency of the transmission wave. Here, the sign of the relative velocity V defines the direction away from the radar device as positive (> 0).

At this time, the frequency of the beat signal obtained in the section where the frequency of the transmission wave is increasing on the time axis is f _b U, and the beat signal obtained in the section where the frequency of the transmission wave is decreasing on the time axis Let f _b D be the frequency. Further, when the frequency difference generated based on the delay time τ is fr, the following equations (1.1) and (1.2) are established.

  Here, fr is proportional to the distance R, and fd is proportional to the relative speed V. Therefore, the distance R and the relative speed V can be obtained by solving Equation 1 for fr and fd.

Next, similarly to the FMCW method, a method (two-frequency ramp method) in which modulation having a portion whose frequency changes linearly on the time axis will be described. In the two-frequency ramp method, at least two types of parallel and discontinuous frequency modulation lamps that are slightly shifted by a frequency fluctuation (ΔF) are alternately sent, and the frequency is obtained from one of the lamps at the end of a specific period (Tf). Switch to the other lamp and determine the detected distance from the target between the received signal for the first lamp (S ₁ (t)) and the received signal corresponding to the second lamp (S ₂ (t)). It is a method of obtaining the target velocity from the estimated distance and the ambiguous straight line associated with the target as a function of the phase difference (Δφ). The operation principle of this in-vehicle radar device will be briefly described with reference to FIG. 2 (Patent Document 1).

  A weak point of the two-frequency CW method that is well-known as a modulation method for in-vehicle radar devices is when the relative speed with respect to the target is zero. On the other hand, the two-frequency ramp method is an improved modulation method so that the beat frequency can be detected according to the distance to the target even when the relative speed to the target is zero, as in the FMCW method.

  FIG. 2 shows an example of the frequency pattern of the transmission wave. Frequency modulation is performed so that the frequency increases linearly on the time axis while switching two frequencies slightly shifted by ΔF every Tf. Transmit the transmission wave with the added. A reflected wave reflected by the transmission signal is received and mixed with a local signal having the same frequency as the transmission signal to obtain a beat signal. From the target peak frequency obtained by subjecting this beat signal to FFT processing, the distance R to the target and the relative velocity V are obtained based on the principle described below.

  The received signal reflected back from the target is Doppler shifted by a frequency fd (= −2 Vf / c) proportional to the relative velocity V between the target and the target. Here, f is the frequency of the transmission wave. Further, the sign of the relative speed V defines the direction away from the radar device as positive (> 0).

  Furthermore, the received signal is shifted by the frequency difference fr corresponding to the delay time τ (= 2R / c) required for the radio wave to make a round trip with the target with respect to the transmission signal.

When the frequency of the beat signal obtained at this time is f _b Ramp, the following formula (2) is established.

  At this time, a phase difference φ caused by ΔF occurs between the two received waves, and the following formula (3) is established for the distance R from the target.

  Here, since fr is proportional to the distance R and fd is proportional to the relative velocity V, the distance R and the relative velocity V can be obtained by solving fr and fd for Equation 2 and Equation 3.

  By the way, in the on-vehicle radar device as described above, a voltage controlled oscillator (hereinafter referred to as “VCO”) is often used to generate a transmission signal. Therefore, in order to accurately detect the distance to the target and the relative speed based on the principle described above, the relationship between the control voltage input to the VCO and the oscillation frequency (hereinafter referred to as “VF characteristic”) is as follows. It is desired that the characteristics be stable and linear.

  However, since the actual VF characteristics are not necessarily linear, it is necessary to finely adjust the control voltage in accordance with the VF characteristics. In addition, the VF characteristics vary greatly for each VCO solid. In addition, since the VF characteristic generally varies greatly depending on the temperature, it is necessary to adjust the control voltage for each temperature. Furthermore, it is necessary to consider the effects of aging and the like.

  For the reasons described above, it is very important to ensure the linearity of the transmission wave particularly in the FM modulation system having a portion where the frequency increases or decreases on the time axis, as represented by the FMCW system and the 2-frequency ramp system. It has become difficult.

  Next, an adverse effect on the target detection performance caused by the fact that the linearity of the transmission wave is not ensured will be described.

  FIG. 3 is a diagram illustrating an example of a transmission / reception frequency, a beat signal frequency, and an FFT signal in a state where the linearity of a transmission wave is not ensured (non-linear state) in an in-vehicle radar using the FMCW method. . In the figure, the case where the relative speed of the target is zero is shown for the sake of simplicity.

  As shown in FIG. 3A, a received wave having a waveform transmitted in a non-linear state is received as a received wave in a non-linear state. For this reason, the beat signal frequency, which should be constant, is not constant as shown in FIG. 3B. As a result, as shown in FIG. 3C, the level of the peak signal of the target in the FFT signal is lowered, and the signal component is distributed with a predetermined width. Furthermore, the position of the vertex may deviate from the original target peak frequency.

  Thus, when the linearity of the transmission signal is not ensured, the following states (1) to (3) are obtained.

(1) Since the target peak level is reduced, it becomes difficult to ensure the original signal to noise ratio.
(2) Since the target peaks are distributed over a wide area, it is difficult to separate and hide other target peaks.

  (3) Since the target peak frequency cannot be accurately detected, it is difficult to accurately detect the target distance and relative speed.

  In the above description, the FMCW method is taken as an example, but the above problem is the same when the two-frequency ramp method and other FM modulation methods are used.

Japanese Patent Laid-Open No. 10-253753

  In such a case, it is difficult to detect the presence of the target even though the target is in the vicinity of the host vehicle, and incorrect measurement is performed that is different from the original target distance and relative speed. It will end up.

  In the inter-vehicle distance warning system, adaptive cruise control system, and pre-crash system, appropriate control according to each system is performed based on the distance and relative speed with the target around the vehicle detected by the in-vehicle radar device. Therefore, it is difficult to ensure sufficient system reliability without solving these problems.

  Accordingly, an object of the present invention is to achieve a state in which target detection accuracy is high by automatically correcting the nonlinearity of a transmission wave generated due to the characteristics of a voltage controlled oscillator in order to solve the above-described problem. It is an object to provide an in-vehicle radar device that maintains the above.

  In order to solve the above-described problem, a representative one of the on-vehicle radar devices according to the present invention generates a control voltage waveform that changes so as to gradually decrease while switching two voltages for each cycle. A modulation processing unit; a modulation correction processing unit that corrects the control voltage waveform generated by the two-frequency modulation processing unit; and a voltage-controlled oscillator that generates a frequency signal depending on an output voltage value from the modulation correction processing unit. A transmission antenna for radiating the frequency signal as a transmission radio wave in space, a reception antenna for receiving a radio wave reflected from a target by the transmission radio wave radiated from the transmission antenna, and the frequency signal A mixer that generates a beat signal by mixing a reception signal received by the reception antenna, and a nonlinear characteristic of the voltage-controlled oscillator based on the beat signal. It calculates information for correcting, having a signal processing unit for outputting the information to the modulation correction unit.

  Another representative example of the on-vehicle radar device according to the present invention is a voltage-controlled transmission unit that generates a transmission wave subjected to frequency modulation, and a frequency is generated on the time axis from the voltage-controlled transmission unit. Means for generating a control voltage for FM modulation so as to have an increasing or decreasing part; transmission means for transmitting the transmission wave; reception means for receiving a reflected wave reflected by the transmission wave on a target; Means for generating a beat signal from a local signal having the same frequency as the transmitted wave and the received wave, means for subjecting the beat signal to frequency spectrum conversion processing, and the distance and relative speed of the target based on the frequency spectrum conversion processing data , A means for measuring the distance and relative velocity with the target by a second method different from the method, and a target measured by the second method From the distance and the relative speed and means for calculating a characteristic of the FM modulation.

  In particular, as the second method, an FSK (Frequency Shift Keying) method or a pulse modulation method is preferably used.

  The other features of the present invention will be described in detail in the embodiments described later.

  ADVANTAGE OF THE INVENTION According to this invention, a highly accurate vehicle-mounted radar apparatus can be provided.

  An in-vehicle radar device according to an embodiment of the present invention will be described below with reference to FIGS. In the description of the embodiments and the drawings, the same reference numerals or the same reference symbols are used for the same components.

  The in-vehicle radar device according to the first embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 4 is a diagram illustrating a block configuration of the in-vehicle radar device according to the first embodiment of the present invention. The on-vehicle radar device includes a modulation switching processing unit 400, a two-frequency ramp modulation processing unit 401, a two-frequency CW modulation processing unit 402, a modulation correction processing unit 403, a voltage control oscillator 404, a transmission antenna 405, a reception antenna 406, and a mixer 407. , A demodulation processing unit 408, an A / D conversion unit 409, a signal processing unit 410, and a notification device 411.

  As shown in the two-frequency ramp section (T1) in FIG. 5A, the two-frequency ramp modulation processing unit 401 performs control that changes so as to gradually decrease while switching two voltages for each period (ΔT). Voltage waveforms (v1_1, v1_2) are generated and applied to the voltage controlled oscillator 404. Further, as shown in the two-frequency CW section (T2) in FIG. 5A, the two-frequency CW modulation processing unit 402 generates control voltage waveforms (v2_1, v2_2) for switching two voltages for each period (ΔT). And applied to the voltage controlled oscillator 404. In addition, the control voltage waveform generated by the two-frequency ramp modulation processing unit 401 or the two-frequency CW modulation processing unit 402 has a frequency-voltage characteristic of the voltage-controlled oscillator 404 measured in advance at the time of product shipment, as will be described later. Often generated on the basis of

  As shown in FIG. 5A, the modulation switching processing unit 400 controls the start timings of the two-frequency ramp modulation processing unit 401 and the two-frequency CW modulation processing unit 402 so that the transmission waveforms are alternately switched in time. Yes.

  The modulation correction processing unit 403 corrects the control voltage waveforms (v1_1, v1_2) generated by the two-frequency ramp modulation processing unit 401 according to the two-frequency ramp modulation nonlinearity correction information generated by the signal processing unit 410 described later. In addition, the control voltage waveform is corrected so that the linearity of the transmission waveform is maintained.

  The voltage-controlled oscillator 404 generates high-frequency signals (f1_1, f1_2) that are frequency-modulated in response to the control voltage waveforms (v1_1, v1_2) input in the two-frequency ramp section (T1). Further, in response to the control voltage waveforms (v2_1, v2_2) input in the two-frequency CW section (T2), the frequency-modulated high-frequency signals (f2_1, f2_2) are generated. FIG. 5B shows, as an example, a state in which high-frequency signals are alternately generated in time corresponding to each input control voltage.

  FIG. 6 is a diagram showing an example of frequency-voltage characteristics of the voltage controlled oscillator 404. As already described, the voltage-controlled oscillator 404 is desired to have a linear frequency-voltage characteristic. However, in reality, it is difficult to have a completely linear characteristic. For this reason, it is often the case that the initial characteristic (p1) is measured in advance and a region showing a linear characteristic as much as possible is used, or the control voltage waveform is adjusted in accordance with a non-linear characteristic.

  In general, such frequency-voltage characteristics are often measured in advance using a measuring instrument such as a spectrum analyzer at the time of product shipment. However, as described above, the frequency-voltage characteristic may change as shown by the changed characteristic (p2) in FIG. 6 due to the influence of temperature and aging. In such a case, the linearity of the transmission waveform cannot be maintained, and as a result, the target detection performance is adversely affected.

  Subsequently, the high-frequency signal is input to the transmission antenna 405 and radiated into the space as a transmission radio wave. The transmission radio wave is reflected by a target such as a vehicle or an obstacle (not shown) and received by the reception antenna 406 as a reception radio wave. The reception signal input to the reception antenna 406 is input to the mixer 407, and the mixer 407 mixes the transmission signal and the reception signal to generate a beat signal. Thereafter, the beat signal is demodulated by the demodulation processing unit 408 and converted into a digital signal by the A / D conversion unit 409. An example of the A / D conversion unit 409 is an A / D converter.

  This digital signal is input to the signal processing unit 410. The signal processing unit 410 calculates the target distance, relative speed, two-frequency Ramp modulation nonlinearity correction information, notification device activation information, and the like by a method described later. For the signal processing unit 410, a processor such as a microcomputer or a digital signal processor is often used.

  The notification device 411 has a function of notifying the driver when the target detection accuracy of the in-vehicle radar device is deteriorated from a predetermined numerical value in accordance with notification device activation information generated by the signal processing unit 410 described later. In addition, as a notification method, there are a display method using an LED or the like, an alarm sound, or the like.

  Next, specific processing of the signal processing unit 410 included in the in-vehicle radar device according to Embodiment 1 of the present invention will be described with reference to FIG. This figure is a flowchart of a routine executed by the signal processing unit 410 and is repeated at predetermined time intervals.

  When the routine is started, first, FFT processing in step 700 is executed, and an FFT signal including frequency spectrum information is generated. Note that the FFT processing can be selected to be performed by software or by a dedicated circuit such as an ASIC.

  Next, a modulation method determination process in step 701 is executed to determine whether the current FFT signal is based on two-frequency CW modulation or two-frequency ramp modulation. If it is determined that the two-frequency CW modulation is performed, the two-frequency CW physical value conversion process in step 702 is executed. On the other hand, if it is determined that the two-frequency ramp modulation, the two-frequency ramp physical value conversion process in step 703 is executed. Note that this determination method can be easily implemented by using a signal at a timing when the modulation switching processing unit 400 switches the modulation method.

  Next, a case where the two-frequency CW physical value conversion process in step 702 is executed will be described. When the two-frequency CW physical value conversion process is executed, the target distance is calculated by Equation (4) based on the FFT signal.

Here, R _fsk is the target distance by two-frequency CW modulation, C is the speed of light, φ ₂ is the phase difference between f2_1 and f2_2 in the received radio wave, and Δf ₂ is the frequency difference between f2_1 and f2_2.

  Further, the relative speed of the target is calculated by Equation 5.

Here, V _fsk is the relative speed of the target by two-frequency CW modulation, C is the speed of light, fd is the Doppler frequency, and f is the transmission frequency.

  Next, the case where the two-frequency Ramp physical value conversion process in step 703 is executed will be described. When the two-frequency CW physical value conversion process is executed, the target distance is calculated by Equation 6 based on the FFT signal.

Here, R _Ramp is the target distance by two-frequency ramp modulation, C is the speed of light, φ ₁ is the phase difference between f1_1 and f1_2 in the received radio wave, and Δf ₁ is the frequency difference between f1_1 and f1_2.

Next, a method for calculating the relative speed of the target in the two-frequency ramp method will be described. As described above, the beat signal (f _b Ramp) obtained by the two-frequency ramp method depends on the delay time τ (= 2R _Ramp / c) until the transmission radio wave is reflected by the target and received again by the radar. Frequency shift (fr) occurs (formula (7)). The delay time τ is also proportional to the distance to the target. Therefore, the relative speed of the target is calculated by Expression (8) that processes so as to subtract the frequency shift (fr) corresponding to this distance.

  Here, fr is a frequency shift according to the distance, ΔRamp is a frequency change amount in the two-frequency ramp section, τ is a delay time, and T1 is a time in the two-frequency ramp section.

Here, V _Ramp is the relative speed of the target by two-frequency ramp modulation, C is the speed of light, f is the transmission frequency, f _b Ramp is the beat frequency, and fr is the frequency shift according to the distance.

  Next, the small section FFT process in step 704 is executed. In this step, the beat signal of the two-frequency ramp section that is normally processed as one FFT section is time-divided into a plurality of small sections, and the FFT processing is executed for each. Note that it is possible to select whether the small section FFT processing is performed by software or by a dedicated circuit such as an ASIC.

  Here, in order to facilitate understanding of the method in the present embodiment, with reference to FIG. 8, for each beat signal obtained when the transmission waveform of the two-frequency ramp section is linear and nonlinear, a small section FFT is obtained. An example when the process is executed will be described. In the figure, an example in which the normal FFT section is divided into four is shown.

  FIG. 8A is an example of a diagram in which the beat signal (a) when the transmission waveform is linear and the beat signal (b) when the transmission waveform is nonlinear are superimposed. These beat signals are time-divided into four sub-sections A to D as shown in the figure, and each is subjected to FFT processing. FIGS. 8B and 8C are superimposed. In FIG. 8B, since the transmission waveform is linear, the obtained beat signal is also constant, and the peak frequencies of the small sections match even when FFT processing is performed by time division.

  However, in FIG. 8C, since the transmission waveform is non-linear, the obtained beat signal is not constant, and the peak frequency varies for each small section. It can be considered that this variation in peak frequency is due to the difference in the amount of frequency change in each small section. Therefore, in order to correct the amount of frequency change for each small section to a value designed in advance using a method described later, the control voltage is corrected for each small section. Thereby, the amount of frequency change in each small section becomes constant, and the transmission waveform can be corrected to a linear state.

  Note that the number of time divisions of the normal processing section can be appropriately determined according to the system. For example, when the normal processing section is sufficiently small, it is possible to abolish this step and immediately execute the next step.

Next, a two-frequency ramp frequency change amount estimation process in step 705 is executed. In this step, the target distance R _fsk and the relative velocity V _fsk , which are the output results of the two-frequency CW physical value conversion process executed last time, and the target in the sub-section subjected to the division FFT process using Equation (9). A two-frequency Ramp frequency change amount in a small section subjected to the current division FFT processing is estimated from the peak frequency (hereinafter referred to as “estimated frequency change amount”).

Here, ΔRamp _est is the estimated frequency change amount in the small section, C is the speed of light, T _i is the time of the small section i, R _fsk is the target distance by the two-frequency CW modulation, f _Ramp is the target peak frequency in the small section, f is a transmission frequency, and V _fsk is a relative speed of a target by two-frequency CW modulation.

  Next, a voltage correction amount calculation process in step 706 is executed. In this step, first, an ideal value of the frequency change amount in the selected small section i is calculated by the equation (10).

Here, ΔRamp _i is an ideal value of the frequency change amount in the small interval i, ΔRamp is the frequency change amount in the two-frequency ramp interval, T _i is the time in the small interval i, and T1 is the time in the two-frequency ramp interval.

  Generally, the control voltage and the like input are adjusted so that the frequency change amount (ΔRamp) in the two-frequency ramp section becomes a value designed in advance according to the demand of the system to be used. For this reason, in practice, signal processing is often performed while ΔRamp used in Equation (7) or the like is constant. For this reason, an error in ΔRamp causes an error in the target detection result.

  Next, the estimated frequency change amount calculated in the two-frequency Ramp frequency change amount estimation process in step 705, the ideal value of the two-frequency Ramp slope in the small section i calculated by Equation (10), and the small section i From the control voltage, the corrected control voltage in the small section i is calculated by Equation (11).

Here, ΔV _i _corr is the corrected control voltage in the small section i, ΔRamp _est is the estimated frequency variation in the small section, ΔRamp _i is the ideal value of the frequency variation in the small section i, and ΔV _i is the control in the small section i. Voltage.

  That is, the processing content of this step is a process of changing the input control voltage amount according to the ratio between the actual FM modulation change amount in a divided FFT section and the FM modulation change amount designed in advance. doing.

  Next, in step 707, it is confirmed whether or not the voltage correction value has been calculated for all of the divided subsections. If completed, the process proceeds to step 708. If not completed, step 706 is performed. Try again.

  Next, the contents of the notification process in step 708 will be described. As described above, the estimated frequency change amount for each small section has already been calculated before this step is reached. Therefore, when the estimated frequency change amount exceeds a preset reference value, it is determined that the target detection reliability of the in-vehicle radar device is significantly reduced. In that case, a signal is transmitted to the notification device 411 to notify the driver vehicle.

  An in-vehicle radar device according to a second embodiment of the present invention will be described in detail with reference to FIGS. 9 to 11.

  This embodiment is different from the configuration of the on-vehicle radar device of the first embodiment in that a pulse modulation method is used as a second method for measuring the target distance and relative speed. Here, the description will focus on the differences from the first embodiment, and the description of the same parts as the first embodiment will be omitted.

  FIG. 9 is a diagram illustrating a block configuration of the in-vehicle radar device according to the second embodiment of the present invention. As shown in the figure, the in-vehicle radar device of this embodiment includes a pulse modulation processing unit 901, a pulse count processing unit 902, and a second signal processing unit 903.

  The pulse modulation processing unit 901 generates a control voltage waveform for generating a transmission pulse signal indicated as Tx in FIG. 10 and applies it to the voltage controlled oscillator 404. The generated transmission signal is radiated into the space through the transmission antenna 405, reflected by a target such as a vehicle or an obstacle (not shown), and received by the reception antenna 406. The received wave at this time is a received signal indicated as Rx in FIG. That is, it is received after a delay time τ corresponding to the distance to the target has elapsed. Further, at this time, the Doppler shift is performed by a frequency fd proportional to the relative speed V with respect to the target.

  The pulse count processing unit 902 measures the time from the time when the transmission wave is generated by the pulse modulation processing unit 901 to the time when a signal having a signal strength of a certain value or more is received from the receiving antenna 406, and the second signal Input to the processing unit 903.

  The second signal processing unit 903 calculates the target distance and relative speed, dual-frequency Ramp modulation nonlinearity correction information, notification device activation information, and the like by a method described later.

  The other blocks are the same as those in the first embodiment.

  Next, specific processing of the second signal processing unit 903 provided in the in-vehicle radar device according to the second embodiment of the present invention will be described with reference to FIG. The features in the figure are the modulation method determination process (2) in step 1100, the pulse modulation physical value conversion process in step 1101, and the two-frequency Ramp frequency change estimation process (2) in step 1102. For this reason, only these processes are demonstrated and other description is abbreviate | omitted.

  In the modulation system determination process (2) in step 1100, it is determined whether the current FFT signal is based on pulse modulation or 2-frequency ramp modulation. Here, when it is determined that the pulse modulation is performed, the pulse modulation physical value conversion process of Step 1101 is executed. On the other hand, if it is determined that the two-frequency ramp modulation, the two-frequency ramp physical value conversion process in step 703 is executed.

  In the pulse modulation physical value conversion process of step 1101, first, the relative velocity of the target is calculated by the equation (12) based on the FFT signal.

Here, V _pulse is the relative speed of the target by pulse modulation, C is the speed of light, fd is the Doppler frequency, and f is the transmission frequency.

  Further, the target distance is calculated by Equation (13) based on the delay time τ input from the pulse count processing unit.

Here, R _pulse is the distance of the target by pulse modulation, C is the speed of light, and τ is the propagation time of the radio wave between the radar and the target.

In the two-frequency Ramp frequency variation estimation process (2) in step 1102, the target distance (R _fsk ) by the two-frequency CW modulation and the target relative velocity (V _fsk ) by the two-frequency CW modulation in the above equation (10). ) _Are replaced with the target distance (R _pulse ) by pulse modulation and the relative velocity (V _pulse ) of the target by pulse modulation, respectively.

  Other steps are the same as those in the first embodiment.

  An in-vehicle radar device according to a third embodiment of the present invention will be described in detail with reference to FIGS.

  The present embodiment is different from the configuration of the in-vehicle radar device of the first embodiment in that a laser radar 1202 is used as a second method for measuring the distance to the target and the relative speed. Here, the description will focus on the differences from the first embodiment, and the description of the same parts as in the first embodiment will be omitted.

  FIG. 12 is a diagram illustrating a block configuration of the in-vehicle radar device according to the third embodiment of the present invention. The on-vehicle radar device of this embodiment is different from the above-described embodiment in that it includes a data receiving unit 1200, a third signal processing unit 1201, and a laser radar 1202. Laser radar is a device that measures the distance and relative speed with a target using light as a transmission wave.

  The laser radar 1202 measures the distance and relative speed with the target at a predetermined cycle, and inputs the measurement result to the data receiving unit 1200. The data receiving unit 1200 receives data input at a predetermined cycle, and inputs this data to the third signal processing unit 1201. As the data transmission means of the laser radar 1202 and the data receiving unit 1200, CAN (Control Area Network), serial communication, or the like can be used.

  The third signal processing unit 1201 calculates target distance and relative speed, two-frequency Ramp modulation nonlinearity correction information, notification device activation information, and the like by a method described later.

  The other blocks are the same as those in the first embodiment, but the modulation switching processing unit 400 and the two-frequency CW modulation processing unit 402 are not provided as compared with the first embodiment. For this reason, as shown in FIG. 13, the transmission waveform is modulated such that the two-frequency ramp modulation is repeated at the period T1.

  Next, specific processing of the third signal processing unit 1201 provided in the in-vehicle radar device according to Embodiment 3 of the present invention will be described with reference to FIG. The feature in this figure is the two-frequency ramp frequency change amount estimation process (3) in step 1400. For this reason, only this process will be described, and description regarding other parts will be omitted.

The two-frequency Ramp frequency change estimation process (3) in step 1400 includes the target distance (R _fsk ) by the two-frequency CW modulation and the target relative velocity (V _fsk ) by the two-frequency CW modulation in the above equation (9). ) Can be executed by substituting the distance and relative speed of the target by the laser radar.

  Other steps are the same as those in the first embodiment.

  The on-vehicle radar device according to the fourth embodiment of the present invention is to use a UWB (Ultra Wide Band) radar instead of the laser radar 1202 used in the third embodiment. Even in this configuration, it is possible to obtain the same effect as in the third embodiment.

  In the first to fourth embodiments, the two-frequency ramp method has been described as an example, but the same effect can be expected for the FMCW method and other FM modulation methods. In the first to fourth embodiments, the technique using the 76 GHz band has been described. However, similar effects can be obtained at other frequencies.

  As described above, according to the above-described embodiment of the present invention, the vehicle-mounted radar that maintains the high target detection accuracy by automatically linearly correcting the nonlinearity of the transmission wave generated due to the characteristics of the voltage-controlled oscillator. An apparatus can be provided.

It is a wave form diagram when a transmission wave exists in a linear state. It is a figure explaining the modulation method in a 2 frequency Ramp system. It is a wave form diagram when a transmission wave is in a nonlinear state. It is a figure which shows the block configuration of the vehicle-mounted radar apparatus of Example 1. FIG. It is a figure which shows the modulation method of the vehicle-mounted radar apparatus of Example 1. FIG. It is a characteristic view of the voltage control type | mold transmitter of the vehicle-mounted radar apparatus of Example 1. FIG. 3 is a flowchart of a routine executed by a signal processing unit provided in the in-vehicle radar device according to the first embodiment. It is a figure explaining the small area FFT process in the signal processing part with which the vehicle-mounted radar apparatus of Example 1 is equipped. It is a figure which shows the block structure of the vehicle-mounted radar apparatus of Example 2. FIG. It is a figure which shows the 2nd modulation method of the vehicle-mounted radar apparatus of Example 2. FIG. 7 is a flowchart of a routine executed by a second signal processing unit provided in the in-vehicle radar device according to the second embodiment. It is a figure which shows the block configuration of the vehicle-mounted radar apparatus of Example 3. FIG. It is a figure which shows the modulation method of the vehicle-mounted radar apparatus of Example 3. FIG. 12 is a flowchart of a routine executed by a third signal processing unit provided in the in-vehicle radar device according to the third embodiment.

Explanation of symbols

400 modulation switching processing unit 401 2 frequency Ramp modulation processing unit 402 2 frequency CW modulation processing unit 403 modulation correction processing unit 404 voltage controlled oscillator 405 transmission antenna 406 reception antenna 407 mixer 408 demodulation processing unit 409 A / D conversion unit 410 signal processing Unit 411 Notification Device 900 Pulse Modulation Processing Unit 902 Pulse Count Processing Unit 903 Second Signal Processing Unit 1200 Data Reception Unit 1201 Third Signal Processing Unit 1202 Laser Radar

Claims (17)

A voltage-controlled oscillation means for generating a transmission wave multiplied by the frequency modulation,
It means for generating a control voltage for the FM modulation to have a portion frequency from the voltage-controlled oscillation unit increases or decreases on the time axis,
Transmitting means for transmitting the transmission wave;
Receiving means for receiving a reflected wave generated by reflecting the transmitted wave on a target as a received wave;
Means for generating a beat signal based on a local signal having the same frequency as the transmission wave and the reception wave;
Means for frequency spectrum conversion processing of the beat signal;
Means for calculating the distance and relative speed with the target based on the data processed by the means for performing frequency spectrum conversion processing;
Means for measuring a distance and relative velocity with respect to the target by a second method different from the FM modulation;
Means for calculating the FM modulation characteristic based on the distance and relative velocity of the target measured by the second method. The on-vehicle radar device according to claim 1,
The means for performing frequency spectrum conversion processing performs frequency spectrum conversion processing for each of a plurality of small sections by time-dividing the beat signal obtained by the FM modulation method,
The on-vehicle radar device characterized in that the means for calculating the FM modulation characteristic calculates the characteristic for each of the plurality of divided small sections. The on-vehicle radar device according to claim 1,
The on-vehicle radar device, wherein the second method is an FSK (Frequency Shift Keying) method. The on-vehicle radar device according to claim 1,
The on-vehicle radar device characterized in that the second method is a pulse modulation method. The on-vehicle radar device according to claim 1,
The on-vehicle radar device further comprises means for temporally switching between the FM modulation method and the second method. The on-vehicle radar device according to claim 1,
The on-vehicle radar device, wherein the second method is a measurement result by a laser radar. The on-vehicle radar device according to claim 6,
The laser radar has a separate structure from the main body of the in-vehicle radar device,
An in-vehicle radar device configured to receive information on a distance and a relative velocity output from the laser radar by communication. The on-vehicle radar device according to claim 1,
The on-vehicle radar device characterized in that the second method is a measurement result by a UWB (Ultra Wide Band) radar. The on-vehicle radar device according to claim 8,
The UWB radar has a separate structure from the main body of the in-vehicle radar device,
An in-vehicle radar device configured to receive information on a distance and a relative velocity output from the UWB radar by communication. The on-vehicle radar device according to claim 1,
Further, the on-vehicle radar device further includes a correction unit that performs a correction process of the control voltage in the FM modulation according to the characteristic of the FM modulation. The on-vehicle radar device according to claim 10,
The on-vehicle radar device according to claim 1, wherein when the FM modulation characteristic has a change greater than a preset value, the correction unit executes the correction process. The on-vehicle radar device according to claim 1,
The vehicle-mounted radar device further comprises means for notifying a driver when there is a change in the FM modulation characteristic that exceeds a preset value. The on-vehicle radar device according to claim 11,
The on-vehicle radar device characterized in that the FM modulation characteristic is a frequency change amount of an FM modulated wave in a selected section. A two-frequency Ramp modulation processing unit that generates a control voltage waveform that gradually decreases while switching between two voltages for each period;
A modulation correction processing unit for correcting the control voltage waveform generated by the two-frequency modulation processing unit;
A voltage-controlled oscillation unit for generating a frequency signal dependent on the output voltage value from the modulation correction unit,
A transmission antenna for radiating the frequency signal as a transmission radio wave in space;
A receiving antenna for receiving the radio wave reflected from the target by the transmission radio wave radiated from the transmission antenna;
A mixer that mixes the frequency signal and the received signal received by the receiving antenna to generate a beat signal;
On the basis of the beat signal, the nonlinear characteristic of the voltage-controlled oscillation unit calculates information for correcting, and having a signal processing unit for outputting the information to the modulation correction unit, the In-vehicle radar device. The on-vehicle radar device according to claim 14,
The signal processing unit by estimating a two-frequency Ramp frequency change, the in-vehicle radar device and calculates the information for correcting the nonlinear characteristic of the voltage-controlled oscillation unit. The in-vehicle radar device according to claim 15,
The on-vehicle radar device has a notification device for notifying the driver when the amount of change in the two-frequency ramp frequency estimated by the signal processing unit is worse than a preset value. An on-vehicle radar device. The in-vehicle radar device according to claim 15,
Further generates a control voltage waveform for switching the two voltage in each cycle, the two-frequency CW modulation processing unit for applying a control voltage waveform to the voltage-controlled oscillation unit,
An in-vehicle radar device comprising: a dual-frequency ramp modulation processing unit and a modulation processing switching unit that controls a start timing of the dual-frequency CW modulation processing unit.

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