JP2008292264A - Radar device and control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent interference of a signal with another radar device with high accuracy, in a restricted frequency band. <P>SOLUTION: This radar device alternately repeating transmission of a radar signal and pause of transmission has a storage part for storing a plurality of combinations formed respectively, by combining the frequency with a transmission time so that at least either of the frequency of the radar signal and the transmission time, when transmission is performed is different; and a control part for selecting the frequency and the transmission time of the transmitted radar signal from among the plurality of combinations. The control part changes the frequency and the transmission time of the transmitted radar signal from the first combination in the plurality of combinations to the second combination at each prescribed timing, to thereby avoid with high accuracy, duplication of at least either the frequency or the transmission time of each signal from mutual radar devices. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radar apparatus that alternately repeats transmission and pause of a radar signal, and a control method therefor.

  2. Description of the Related Art In recent years, in vehicles such as automobiles, in-vehicle radar devices that detect relative speed and relative distance of a preceding vehicle ahead of the host vehicle are used in order to perform follow-up traveling control with respect to the preceding vehicle. As such an on-vehicle radar device, a FM-CW (Frequency Modulation-Continuous Wave) type radar device that is configured in a small and inexpensive manner by a simple signal processing circuit is widely employed. The FM-CW radar apparatus transmits a continuous wave, which is frequency-modulated according to a triangular wave, as a radar signal, receives a reflected signal with respect to the transmitted signal, and calculates the relative speed and relative distance of the target from the frequency difference between the transmitted signal and the received signal. Is detected.

  In a general FM-CW radar apparatus, the frequency of a transmission signal is modulated with a modulation width of about 50 MHz to 200 MHz. Therefore, when a plurality of vehicles mounted with the same FM-CW radar apparatus are approaching and the modulation widths of the respective radar apparatuses overlap, transmission signals of the same frequency are transmitted from the respective radar apparatuses. . Then, the signals interfere with each other, and erroneous detection occurs if an attempt is made to detect the relative distance and relative speed with respect to the preceding vehicle using the interfered signals. Therefore, a method for avoiding such signal interference between radar devices is desired.

As an example, Patent Document 1 discloses that the frequency modulation period (triangular wave period) of the transmission signal transmitted by the radar apparatus of the own vehicle is changed at random, thereby causing interference with the transmission signal from the radar apparatus of the other vehicle. A method for reducing the probability is described. Patent Documents 2 and 3 describe a method of changing the frequency of a transmission signal transmitted from the radar apparatus of the host vehicle when interference with a transmission signal from a radar apparatus of another vehicle is detected.
JP 2001-33546 A JP 2002-168947 A JP 2004-170183 A

  By the way, in order to prevent signal interference between a plurality of in-vehicle radar devices, it is desirable that the frequency modulation widths of transmission signals transmitted by the individual in-vehicle radar devices do not overlap. However, in the method described in Patent Document 1, even if the frequency modulation period of the transmission signal is changed, the modulation width of the signal transmitted by the radar device of the host vehicle and the modulation width of the signal from the radar device of the other vehicle The duplication of is not resolved. Therefore, there is a problem that the radar device of the own vehicle receives a transmission signal from the radar device of another vehicle having the same frequency as the own transmission signal.

  However, the frequency of the transmission signal of the on-vehicle radar is limited to a band of 76.0 GHz to 77.0 GHz according to the regulations of the Radio Law, and on the other hand, the modulation width of each radar device is about 50 MHz to 200 MHz. I need. Therefore, the patterns in which the modulation widths of a plurality of radar apparatuses can be arranged without duplication within a legally usable band are naturally limited. Therefore, if the frequency of the transmission signal is randomly set by each radar device, it is not possible to efficiently avoid duplication of the modulation width and prevent interference with high accuracy.

  Further, in the methods described in Patent Documents 2 and 3, if the frequency of the transmission signal is changed when the interference is detected, if the radar apparatus of the other vehicle performs the same operation, the interference at the changed frequency recurs. There is a problem of end up.

  Accordingly, an object of the present invention is to prevent interference of signals with other radar devices with high accuracy in a limited frequency band, and to prevent recurrence of interference with high accuracy even when interference is detected. It is an object of the present invention to provide a radar apparatus and a control method thereof that can be prevented.

  In order to achieve the above object, according to a first aspect of the present invention, in a radar apparatus that alternately repeats transmission of a radar signal and pause of the transmission, the frequency of the radar signal and a transmission time of the transmission are determined. A storage unit storing a plurality of combinations in which the frequency and the transmission time are combined so that at least one of them is different, and a control for selecting the frequency and transmission time of the transmitted radar signal from the plurality of combinations Part. And the said control part changes the frequency and transmission time of the radar signal transmitted at every predetermined timing from the 1st combination of the said several combinations to a 2nd combination, It is characterized by the above-mentioned.

  In a preferred embodiment of the above aspect, the radar apparatus further includes an interference detection unit that detects interference of another signal with the radar signal, and the control unit further includes the combination of the combination when the interference is detected. It is characterized by making a change.

  According to the above aspect, between radar devices including a storage unit storing a plurality of combinations in which the frequency and the transmission time are combined so that at least one of the frequency and the transmission time of the radar signal is different, By using different combinations for each, it is possible to reliably avoid at least one overlap in frequency or transmission time of transmission signals between radar devices. Since these radar devices change their combinations at predetermined timings, the probability of using the same combination can be reduced, and interference between signals between radar devices can be prevented with high accuracy. Moreover, according to the said embodiment, since the said combination is changed also when interference is detected, recurrence of interference can be prevented with high accuracy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof.

  FIG. 1 is a diagram illustrating a configuration of a radar apparatus according to the present embodiment. The radar apparatus 1 of FIG. 1 transmits a frequency-modulated transmission signal and receives a reflected signal reflected by a target such as a preceding vehicle, and compares the target signal based on the frequency difference between the transmission signal and the received signal. This is an FM-CW radar device that detects distance and relative velocity. The radar device 1 is mounted on a vehicle, for example, and is used to detect the relative speed and relative distance of a preceding vehicle.

  In the radar apparatus 1, the frequency modulator 2 generates a frequency modulation signal, and the oscillator 4 generates a transmission signal that is frequency-modulated according to the frequency modulation signal. The transmission signal is transmitted forward of the vehicle by the transmission antenna 6.

  At this time, the frequency modulator 2 alternately repeats a predetermined time interval in which the frequency modulation signal is generated and a predetermined time interval in which the generation is paused. Here, FIG. 2A shows the transmission timing and frequency of the transmission signal. Note that in FIG. 2A, the horizontal axis indicates time. As shown in FIG. 2A, the operation of the frequency modulator 2 alternately repeats a transmission time for transmitting a frequency-modulated transmission signal according to a triangular wave and a pause time for stopping transmission. In this embodiment, one set of transmission time and pause time corresponds to the transmission cycle. Further, the reception signal processing described below is performed during the downtime.

  When the transmission signal is reflected by a target such as a preceding vehicle, the reflected signal is received by the receiving antenna 8. The received signal is input to the mixer 10 and mixed with a part of the transmission signal. Then, a beat signal that is a frequency difference between the transmission signal and the reception signal is generated, and the beat signal is input to the frequency measuring device 12 and the interference detection unit 14.

  Here, the transmission signal, the reception signal, and the beat signal generated from them will be described with reference to FIGS. FIG. 2B shows the frequencies of the transmission signal W1 and the reception signal W2 transmitted during the transmission time, and FIG. 2C shows the frequency of the beat signal B1 that is the difference between these frequencies. In FIGS. 2B and 2C, the horizontal axis indicates time.

  As shown in FIG. 2B, the transmission signal W1 is a continuous wave that is frequency-modulated according to a triangular wave having a period 1 / fm, a center frequency f0, and an amplitude ΔF, and repeatedly increases and decreases with the amplitude ΔF as a frequency modulation width. . The received signal W2 receives a time lag (ΔT) corresponding to the distance of the target and a frequency shift (ΔD) due to the influence of the Doppler effect corresponding to the relative speed. Then, from such transmission signal W1 and reception signal W2, as shown in FIG. 2C, a beat signal B1 having a frequency fb1 in the rising section of the frequency of the transmission signal W1 and a frequency fb2 in the falling section is obtained. .

  The beat signal B1 is subjected to FFT (Fast Fourier Transform) by the frequency measuring device 12, and a frequency component is extracted. Then, the extracted frequency component is input to the control unit 20.

  The control unit 20 is configured by a microcomputer as an example. The function of the control unit 20 is realized by a CPU (not shown) operating according to various processing programs and control programs stored in the storage unit 19 that is a nonvolatile memory.

  When the frequency component of the beat signal B1 is input, the control unit 20 calculates the relative distance R and the relative speed V of the preceding vehicle using the following two equations. In the following two formulas, C is the speed of light.

Formula 1: R = C · (fb1 + fb2) / (8 · ΔF · fm)
Formula 2: V = C · (fb2-fb1) / (4.f0)
These calculation results are input to a travel control ECU (Electronic Control Unit) (not shown) that performs the following travel control of the vehicle. Then, the travel control ECU controls the operation of each part of the vehicle so that the inter-vehicle distance from the preceding vehicle is maintained at a predetermined distance.

  Here, a case where another vehicle equipped with another radar apparatus having the same configuration as that in FIG. 1 approaches the host vehicle will be described with reference to FIG. FIG. 3 shows the frequencies of the reception signal W2 of the radar device 1 of the host vehicle and the transmission signal W3 from the radar device of the other vehicle. As shown in FIG. 3, the same radar apparatus may have overlapping frequency modulation widths. Then, the transmission signal W3 from the radar apparatus of the other vehicle interferes with the reception signal W2 of the radar apparatus 1 of the own vehicle (arrow C), and the frequencies fb1 and fb2 of the beat signal B1 shown in FIG. To shift. Then, as is clear from the above formulas 1 and 2, the relative distance R and the relative speed V are erroneously detected. Therefore, this embodiment is characterized in that interference with a transmission signal from a radar device of another vehicle is prevented in the following manner.

  In this embodiment, as an example, frequency modulation of a transmission signal is performed with a modulation width of 100 MHz. Further, one transmission cycle shown in FIG. 2A is set to 100 milliseconds (transmission time is 20 milliseconds, pause time is 80 milliseconds). In the storage unit 19 of the control unit 20, a plurality of combinations of the frequency of the transmission signal, that is, the center frequency of the modulation width, and the transmission time, that is, the transmission start time in one transmission cycle are shown in FIG. It is stored as a matrix 19a as shown.

  In the matrix 19a, four frequencies are associated with the horizontal rows. FIG. 4B shows the relationship between the frequency for each horizontal row and the frequency modulation width centering on the frequency, and they are arranged so as not to overlap each other.

  The vertical column of the matrix 19a is associated with three transmission start times. At the start of transmission, it corresponds to a time when a transmission time of 20 milliseconds is started in 100 milliseconds of one transmission cycle. FIG. 4C shows the relationship between transmission times (and pause times) corresponding to this transmission start time. Then, at 0 milliseconds at the start of transmission in the first column, the transmission time is from 0 milliseconds to 20 milliseconds at the start of each transmission period, and the pause time is from 20 milliseconds to 100 milliseconds. In addition, at 40 milliseconds at the start of transmission in the second column, each transmission cycle starts from 0 milliseconds to 40 milliseconds, pause time, 40 milliseconds to 60 milliseconds is transmission time, and from 60 milliseconds to 100 milliseconds. Is the pause time. Furthermore, at 80 milliseconds at the start of transmission in the third column, the pause time is from 0 milliseconds to 80 milliseconds at the start of each transmission cycle, and the transmission time is from 80 milliseconds to 100 milliseconds. Accordingly, the transmission times at the start of transmission for each vertical column are arranged so as not to overlap, that is, the transmission time of one column corresponds to the pause time of the other column.

  The matrix 19a stores the above-described frequencies and 12 combinations S11,..., S34 at the start of transmission.

  When the radar apparatus 1 is started, the control unit 20 selects one combination from the matrix 19a as described above, and causes the frequency modulator 2 to generate a frequency modulation signal with the frequency and transmission time of the combination. A transmission signal is transmitted. At this time, the combination is selected by initial setting based on attribute information such as the model and serial number of the radar device 1 and attribute information such as the type of vehicle mounted. Alternatively, it can be determined at random based on the starting time and other random numbers.

  And the control part 20 acquires absolute time from a radio clock tower via the communication apparatus 30, and makes the frequency modulator 2 start a transmission period according to the start of the second of absolute time. That is, a transmission cycle of 100 milliseconds is started in synchronization with the start of every second, and transmission and pause of 10 cycles are executed per second. In each transmission cycle, a transmission time of 20 milliseconds is started at the start of transmission corresponding to the selected combination. In this way, by synchronizing the start of the transmission cycle with the start of the second of the absolute time, duplication of the transmission time is avoided between combinations with different columns.

  Here, considering a case where a plurality of vehicles equipped with the radar device 1 that performs the above-mentioned operation approach each other, if the combination selected at the start of each radar device is different, at least one of the frequency or the transmission time of the transmission signal Therefore, signals of the same frequency are not simultaneously transmitted from these radar devices. In this way, the matrix 19a is shared by a plurality of radar devices, and the frequency of the transmission signal is set in accordance with the matrix 19a, so that the frequency can be efficiently used in a legal band more efficiently than when each device sets the frequency randomly. The modulation width can be assigned. Therefore, interference of transmission signals between radar devices can be avoided, and erroneous detection of relative speed and relative distance can be prevented.

  In addition, the control unit 20 changes the combination of the frequency and the transmission start time to another combination of the matrix 19a every one or a plurality of transmission periods or every predetermined time. Here, the other combinations are arranged in the order of S11, S21, S31, S12, ..., S32, S13, ..., S33, S14, ..., S34, S11, ... according to the order of the rows or columns of the matrix 19a. You may choose. Alternatively, a new combination may be selected based on a random number generated by a known method using the current time or various noises.

  Thus, by changing the combination of the frequency and the transmission time as needed, the probability of using the combination at the same frequency and the start of transmission can be reduced among a plurality of radar apparatuses, and interference can be avoided with higher accuracy. If the combination selection at start-up, the change timing of the combination, or the selection method of the combination to be changed are set differently for each apparatus, a plurality of radar apparatuses use the same frequency and the combination at the start of transmission simultaneously. Probability can be further reduced.

  Returning to FIG. 1, the radar apparatus 1 further includes an interference detection unit 14. For example, the interference detection unit 14 detects interference when the amplitude or frequency of the beat signal B1 exceeds a preset threshold value, and inputs the result to the control unit 20.

  In the conventional technique, the plurality of radar devices shift the frequency of the transmission signal in order to avoid interference, but if each radar device performs the same operation, the interference at the changed frequency will reoccur. If the frequency shift width is insufficient, the frequency shift operation must be repeated in order to completely eliminate the modulation width overlap.

  Therefore, the present embodiment is characterized in that the control unit 20 randomly selects and uses the frequency and transmission time of the transmission signal from the matrix 19a described above. At that time, as described above, it is possible to select a new combination based on a random number generated by a known method using the current time and various noises. Alternatively, the matrix numbers S11, S12,..., S34 in the matrix 19a may be recombined with random numbers, and then the combinations may be selected in the order of the matrix numbers.

  As described above, since the combinations stored in the matrix 19a are configured such that at least one of the frequency of the transmission signal and the transmission time is different from each other, a plurality of radar devices select different combinations. By doing so, it is possible to reliably eliminate duplication of frequency modulation widths. Therefore, each of the plurality of radar devices can prevent the recurrence of interference with high accuracy.

  FIG. 5 is a flowchart for explaining the operation procedure of the radar apparatus 1 of the present embodiment. The procedure shown in FIG. 5 is executed when the radar apparatus 1 is activated. First, the control unit 20 selects an initial combination from the matrix 19a. At the same time, a counter variable for counting the number of times of interference detection is initialized to “0” (S2). When the value of the counter variable is less than “3” (YES in S4), that is, when interference is not detected three times or more, a transmission signal is transmitted at a frequency and transmission time corresponding to the selected pattern ( S6). On the other hand, when the value of the counter variable is “3” or more (NO in S4), that is, when interference is detected three times or more, another radar apparatus uses the same combination of frequency and transmission time, and the combination is changed. Since there is a high possibility that the patterns are the same, transmission of the transmission signal is stopped in order to prevent interference from occurring continuously (S20).

  Then, when no interference is detected from the received signal (NO in S10) and a predetermined time or a predetermined transmission cycle elapses (YES in S12), another combination of frequency and transmission time is selected from the matrix 19a (S14). . And it returns to procedure S4 and repeats a series of above-mentioned procedures. On the other hand, when interference is detected in step S10 (YES in S10), the combination is changed and the value of the counter variable is incremented by “1” (S18). And it returns to procedure S4 and repeats a series of above-mentioned procedures.

  The frequency, transmission time, transmission cycle, and the like of the transmission signal described above are examples, and the present embodiment can be applied to other than the above. In addition, the number of interference detections in step S4 in FIG. 5 can be arbitrarily set. Alternatively, instead of stopping the transmission in step S20, the order of the combination of the matrix 19a may be reconfigured with a random number.

  FIG. 6 is a flowchart for explaining the operation procedure of the radar apparatus 1 according to the modification of the present embodiment. The same procedures as those shown in FIG. 5 are denoted by the same reference numerals.

  When the radar apparatus 1 is activated, the control unit 20 selects an initial combination from the matrix 19a and stores the selected combination in a working memory in the control unit 20 (S2a). Then, a transmission signal is transmitted at a frequency and transmission time corresponding to the selected pattern (S6).

  If no interference is detected from the received signal (NO in S10) and a predetermined time or a predetermined transmission period has elapsed (YES in S12), another combination of frequency and transmission time is selected from the matrix 19a, and a new one is newly selected. The memory history is updated with the selected combination (S14a). And it returns to procedure S4 and a series of above-mentioned procedures are performed. On the other hand, when interference is detected in step S10 (YES in S10), the combination history is read from the memory to determine whether there is an unselected combination. When there is an unselected combination (YES in S16), one of them is selected and the selected combination is added to the memory history (S18a). And it returns to procedure S4 and a series of above-mentioned procedures are performed. If there is no unselected combination (NO in S16), a plurality of other radar devices exist around the radar device 1 of the host vehicle such as traffic congestion, and the combination of the matrix 19a is determined by the other radar device. Since it is being used, transmission is stopped in order to prevent interference from occurring continuously (S20).

  When the interference is not detected in step S10 in FIGS. 5 and 6, the combination in the matrix 19a is changed every time a predetermined time elapses, and steps S12 and S14 in FIG. 5 or steps S12 and S14a in FIG. It may be omitted. That is, when interference is not detected (NO in S10), the combination is not changed, and when interference is detected (YES in S10), the procedure may be changed as described above. By such a procedure, the combination of the frequency and the transmission time is not changed until interference is detected, so that the processing of the control unit 20 can be reduced. And when interference is detected, recurrence of interference can be avoided with high accuracy by changing the combination.

  Note that, after the transmission is stopped in step S20 of FIGS. 5 and 6, the history of the counter variables and the combination may be cleared after a predetermined time has elapsed, and the transmission may be resumed. By setting a sufficient time for a nearby vehicle to move, the probability of interference occurring even when transmission is resumed can be reduced. Moreover, it is good also as a structure which receives the transmission signal from the radar apparatus of another vehicle at a rest time, and the control part 20 detects the frequency. At this time, after confirming that the detected frequency does not interfere with the frequency of the transmission signal of the radar device 1 of the host vehicle, the transmission of the radar device 1 of the host vehicle may be resumed.

  FIG. 7 is a diagram illustrating an example in which the radar apparatus 1 is mounted on a vehicle. The radar device 1 is mounted on the front portion of the vehicle 100 and transmits a radar signal to the front of the vehicle 100 and a reflected signal through a bumper, a front grille, a radome provided on the side of the license plate, etc. Is received. In addition, the radar apparatus 1 may be mounted not only in front of the vehicle 100 but also in the rear part or the side part, and may be configured to search the rear or side of the vehicle 100. In that case, it can be implemented in the same manner as the above-described embodiment, and has the same effects.

  The radar apparatus 1 in the above description is configured to generate a radar signal transmitted by the transmission antenna 6 and process a reception signal received by the reception antenna 8, and does not include the transmission antenna 6 and the reception antenna 8. However, the present embodiment can also be applied to a configuration in which the radar apparatus 1 includes the transmission antenna 6 and the reception antenna 8.

  Note that the transmission time and pause time in the above description, and the length of the transmission cycle composed of these are not limited to the above example. In the above description, the FM-CW radar apparatus is taken as an example. However, the present embodiment can be applied to a radar apparatus that transmits a transmission signal while repeating a transmission time and a pause time. Furthermore, this embodiment can be applied not only as an in-vehicle radar device but also to a radar device that needs to avoid interference with other radar devices.

  As described above, according to the present embodiment, it is possible to avoid at least one overlap in frequency or transmission time of transmission signals between radar devices with high accuracy, and as a result, it is possible to prevent interference between signals between radar devices. it can. Further, even when interference is detected, recurrence of interference can be prevented with high accuracy.

It is a figure explaining the structure of the radar apparatus in this embodiment. It is a figure explaining the frequency and timing, such as a transmission signal. It is a figure explaining the relationship between the received signal of the radar apparatus 1 of the own vehicle, and the transmission signal from the radar apparatus of another vehicle. It is a figure explaining the matrix of the combination of the frequency of a transmission signal, and transmission time. It is a flowchart explaining the operation | movement procedure of the radar apparatus 1 of this embodiment. It is a flowchart explaining the operation | movement procedure of the radar apparatus 1 in the modification of this embodiment. It is a figure showing the example where radar device 1 was carried in vehicles.

Explanation of symbols

1: radar device, 2: frequency modulator, 4: oscillator, 6: transmission antenna, 8 reception antenna, 10: mixer, 12: frequency measuring device, 14, interference detection unit, 19: storage unit, 20: control unit

Claims (7)

In a radar apparatus that alternately repeats transmission of a radar signal and pause of the transmission,
A storage unit storing a plurality of combinations in which the frequency and the transmission time are combined such that at least one of the frequency of the radar signal and the transmission time for transmission is different;
A control unit for selecting a frequency and a transmission time of a radar signal to be transmitted from the plurality of combinations;
The control unit changes the frequency and transmission time of a radar signal to be transmitted from a first combination to a second combination of the plurality of combinations at every predetermined timing. In claim 1,
The radar apparatus according to claim 1, wherein the predetermined timing is a transmission cycle including a transmission time of the radar signal and a transmission pause time, or a timing based on an elapsed time. In claim 1,
An interference detector for detecting interference of other signals with the radar signal;
The control device further changes the combination when the interference is detected. In claim 3,
The radar apparatus according to claim 1, wherein the control unit stops transmission of the radar signal when the combination is changed a predetermined number of times. In claim 3,
The control unit repeatedly changes the combination every time the interference is detected, and when the interference is detected by a predetermined number or more of a plurality of combinations stored in the storage unit, the radar signal A radar apparatus characterized by stopping the transmission of. In any one of Claims 1 thru | or 5,
The control unit, when changing the combination, based on a predetermined order of the plurality of combinations, attribute information of the radar device, attribute information of a vehicle or the like on which the radar device is mounted, absolute time, or a random number And selecting the second combination. In a method for controlling a radar apparatus that alternately repeats transmission of a radar signal and pause of the transmission,
A frequency and a transmission time of a radar signal to be transmitted are selected from a plurality of combinations in which the frequency and the transmission time are combined so that at least one of the frequency of the radar signal and the transmission time for performing the transmission is different. A process to select;
Changing the frequency and transmission time of a radar signal to be transmitted from the first combination to the second combination of the plurality of combinations at predetermined timings. Method.

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