JP2018163108A - On-vehicle radar device, antenna array control method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle radar device that can obtain a sufficient measurable distance while suppressing sidelobe.SOLUTION: A first embodiment of the present disclosure is directed at an on-vehicle radar device that comprises: an antenna array that is equipped with a first antenna group including at least an antenna element of either end, of m (m is an integer equal to or more than 3) pieces of antenna elements lined in a prescribed direction, and a second antenna group composed of an antenna element not included in the first antenna group and including at least a central antenna element in the prescribed direction; and a control unit that, when radiating an electromagnet wave in a first range including at least a front direction of the antenna array, controls so that radiation intensity of the electromagnetic wave from the second antenna group is greater than that of the electromagnetic wave from the first antenna group.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an on-vehicle radar device, an antenna array control method, and a program.

  In recent years, development of an on-vehicle radar device using a quasi-millimeter wave band (24 GHz) or a millimeter wave band (76 GHz to 81 GHz) has been progressing rapidly.

  Beam combining using an antenna array is used as one technique for efficiently radiating transmission power only in a desired direction with this type of in-vehicle radar device and accurately estimating the arrival direction of the target. When this technique is applied to an in-vehicle radar device, it is desirable to suppress unnecessary radiation (side lobe) of radio waves in directions other than the desired direction as much as possible in order to prevent erroneous detection due to objects existing in directions other than the desired direction. In order to suppress the side lobes, it is theoretically known that the electromagnetic wave radiation intensity from each antenna element should be gradually reduced from the center to the edge of the antenna array. Dropping has the side effect of dropping not only the side lobe but also the transmission output in the desired direction, and the required measurable distance may not be obtained.

Japanese Patent Laid-Open No. 10-325843

  An object of the present disclosure is to provide an on-vehicle radar device, an antenna array control method, and a program capable of obtaining a necessary measurable distance while suppressing side lobes.

  The first form of the present disclosure is not included in the first antenna group including at least antenna elements at both ends among m antenna elements (m is an integer of 3 or more) arranged in a predetermined direction, and the first antenna group. A second antenna group comprising antenna elements, the antenna array comprising: a second antenna group including at least a central antenna element in the predetermined direction; and an electromagnetic wave in a first range including at least a front direction of the antenna array. Is directed to an in-vehicle radar device including a control unit that controls the radiation intensity of the electromagnetic wave from the second antenna group to be larger than the radiation intensity of the electromagnetic wave from the first antenna group.

  The second form of the present disclosure includes a first antenna group including at least antenna elements at both ends among m antenna elements (m is an integer of 3 or more) arranged in a predetermined direction, and is not included in the first antenna group. A second antenna group comprising antenna elements, the second antenna group including at least a central antenna element in the predetermined direction, and a method for controlling an antenna array, including at least a front direction of the antenna array A method of controlling an antenna array, comprising the step of controlling the electromagnetic wave radiation intensity from the second antenna group to be greater than the electromagnetic wave radiation intensity from the first antenna group when the electromagnetic wave is radiated to the first range. Directed to.

  In the third embodiment of the present disclosure, among m antenna elements (m is an integer of 3 or more) arranged in a predetermined direction, the first antenna group including at least antenna elements at both ends, and not included in the first antenna group A program for controlling an antenna array comprising: a second antenna group comprising antenna elements, and a second antenna group including at least a central antenna element in the predetermined direction, wherein the program is stored in a computer. When radiating electromagnetic waves to the first range including the front direction of the array, processing is performed so that the radiant intensity of the electromagnetic waves from the second antenna group is greater than the radiant intensity of the electromagnetic waves from the first antenna group. Directed to the program.

  In each of the above embodiments, it is possible to provide an in-vehicle radar device, an antenna array control method, and a program that can obtain a sufficient measurable distance while suppressing side lobes.

The figure which shows the structural example of the radar apparatus of this indication, and a general radar apparatus The figure which shows the monitoring area used with the radar apparatus of FIG. The figure which shows the lane merge scene of the vehicle carrying the radar apparatus of FIG. 1 in time series Flow chart showing processing of radar device of present disclosure The figure which shows the characteristic curve of the gain with respect to an angle of the beam radiate | emitted to the 1st range by step S003 of FIG. The figure which shows the characteristic curve of the gain with respect to an angle of the beam radiate | emitted to the 1st range by a modification

[1 definition]
In FIG. 1 and others, the x-axis indicates a direction in which m antenna elements 111 are arranged (hereinafter referred to as a predetermined direction x). The y-axis is orthogonal to the x-axis and indicates the normal direction of the main surface of the dielectric substrate (hereinafter referred to as the front direction y).

  Table 1 below shows the meanings of acronyms and abbreviations used in the following description.

[2 embodiment]
Hereinafter, the vehicle-mounted radar device 1, the antenna array control method, and the program according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[2.1 General configuration of general in-vehicle radar device 5]
First, prior to the description of the in-vehicle radar 1 of the present disclosure, a general in-vehicle radar device 5 will be described in detail.

  As shown in FIG. 1, the in-vehicle radar device 5 includes an antenna array 11, a control unit 13, a phase shifter 15, a frequency converter 17, a local oscillator 19, an amplifier 21, and a power amplifier 23. It is equipped and monitors the surroundings of the vehicle V. The monitoring area of the in-vehicle radar device 5 will be described as an area defined in front of the right side of the vehicle V, but other than the right front side of the vehicle V (such as the right rear side) may be monitored.

  1 and the like are also used in the description of the on-vehicle radar device 1 according to the present disclosure described later. Therefore, both reference numerals 1 and 5 are used for the in-vehicle radar device 5 in these drawings.

  The antenna array 11 includes m antenna elements 111 (m is an integer of 3 or more). The m antenna elements 111 are formed on the main surface of the dielectric substrate so as to be aligned in a predetermined direction x. Hereinafter, the description will be continued assuming that m = 8.

  The antenna array 11 is attached to the front right corner of the vehicle V so that the main surface (that is, the antenna surface) of the dielectric substrate faces the monitoring area.

  The m antenna elements 111 are classified into a first antenna group 115 and a second antenna group 117.

  The first antenna group 115 includes at least antenna elements 111 located at both ends in the predetermined direction x among the m antenna elements 111.

  The first antenna group 115 may further include n antenna elements 111 continuous from the antenna elements 111 at both ends toward the center. In most cases, n is an integer of 2 or more, but may be 1. When n is 1, the first antenna group 115 includes only antenna elements 111 at both ends.

  The second antenna group 117 is composed of the antenna elements 111 not included in the first antenna group 115 among the m antenna elements 111, and essentially includes the antenna element 111 positioned at the center of the antenna array 11.

  Here, when m is an odd number, the central antenna element 111 is located at the (m−1) / 2th element in the central direction from the antenna elements 111 at both ends. On the other hand, when m is an even number, the center antenna element 111 is located at the m / 2th in the center direction from the antenna elements 111 at both ends.

  The second antenna group 117 includes four or more antenna elements 111 continuous in a predetermined direction x when m is an even number, and three or more antennas continuous in the predetermined direction x when m is an odd number. It consists of the element 111.

  Each antenna element 111 is driven by a modulation signal (high frequency signal) supplied from the power amplifier 23 at the subsequent stage, and radiates electromagnetic waves. The electromagnetic waves radiated from the antenna elements 111 are synthesized in space. In this description, an electromagnetic wave synthesized in space may be called a beam.

  Reference is now made to FIG. The beam is scanned in the monitoring area A by appropriately changing the phase of a baseband signal described later. Specifically, the monitoring area A is divided every predetermined angle step Δθ. In the monitoring area A of this description, it is assumed that eight partial areas B1 to B8 are formed in order from one end to the other end in the beam scanning direction. The number of divided areas may be other than eight.

  More specifically, the partial area B1 is in front of the vehicle, and the partial area B8 is on the right side of the vehicle. Further, the boundary area between the partial areas B4 and B5 is the center in the scanning direction and coincides with the front direction y of the antenna array 11. Such partial areas B4 and B5 are examples of the first range, and the other partial areas B1 to B3 and B6 to B8 are examples of the second range.

  The control unit 13 is, for example, an ECU in which an input unit, an output unit, a microcomputer, a program memory, a working memory, and the like are mounted on a control board. The microcomputer executes a program stored in advance in the program memory using the working memory, and controls each component of the in-vehicle radar device 5. In particular, the program memory stores, for example, an application for lane merging support by ADAS or lane merging by automatic driving of the vehicle, and the microcomputer executes this application as necessary.

  The control unit 13 outputs the baseband signal to each phase shifter 15.

  Each phase shifter 15 is electrically connected to the control unit 13, and in order to scan the outgoing beam from the antenna array 11 in the monitoring area A (see FIG. 2), an input baseband signal to itself. Shift the phase of. Here, the shift amount of each phase is designated by the control unit 13.

  Each phase shift amount is obtained in advance by an experiment or the like in the design / development stage of the in-vehicle radar device 1 and described in an LUT stored in the control unit 13.

  Each frequency converter 17 receives a baseband signal from the phase shifter 15 connected to the subsequent stage thereof. Each frequency converter 17 also receives a carrier wave (for example, a millimeter wave band carrier wave) from the local oscillator 19. Each frequency converter 17 modulates an input carrier wave with an input baseband signal to generate a modulated signal.

  In this description, the carrier wave output from one local oscillator 19 is branched into m and then input to the corresponding frequency converter 17 via the amplifier 21. The gain of each amplifier 21 is variable and is specified by the control unit 13. The setting of the amplification degree will be described later.

  Each power amplifier 23 receives a modulation signal from the frequency converter 17 connected to the subsequent stage thereof. Each power amplifier 23 amplifies the received modulation signal with the gain designated by the control unit 13 and supplies the amplified modulation signal to the antenna element 111 in the previous stage.

  When a modulation signal is supplied to each antenna element 111, the antenna array 11 emits a beam toward the monitoring area A (see FIG. 2). The outgoing beam is reflected by a target existing in the monitoring area A, and part of the outgoing beam arrives at the in-vehicle radar device 1 as a return wave. The control unit 13 derives the position (specifically, the distance and direction) of the target with reference to the in-vehicle radar device 1 using such a return wave. Note that the processing of the return wave is not a main part of the present disclosure, and therefore further explanation is omitted.

[2.2 Details of technical issues]
Here, the outgoing beam in the front direction y includes a main lobe and a plurality of side lobes. The side lobes are formed over a wide range in both the left and right directions when the front direction y of the antenna array 11 is 0 °.

  When this in-vehicle radar device 5 is applied to lane merging, it is important to obtain a sufficient measurable distance while suppressing side lobes. Hereinafter, this problem will be described in detail.

  FIG. 3 is a diagram showing the lane merge scene of the host vehicle V1 equipped with the above-described general vehicle-mounted radar device 5 in time series. FIG. 3 also shows a monitoring area A that is divided into eight partial areas B1 to B8 for easy understanding of the problem.

  First, when the control unit 13 executes an application for supporting lane merge, in FIG. 3, at time t0, the other vehicle V2 as a target exits toward the partial areas B7 and B8 on the right side of the host vehicle V1. Captured by the beam. At this time, if the host vehicle V1 is close to the other vehicle V2, the possibility of erroneous detection of an object such as another partial area B6 by the side lobe Ls is sufficiently low, and the control unit 13 Do not instruct to join the lane.

  Further, at time t2 after time t0, the other vehicle V2 is captured by a beam emitted toward the partial areas B3 and B4 in front of the host vehicle V1. At this time, since the other vehicle V2 is traveling at a position sufficiently away from the host vehicle V1, the side lobe characteristics are deteriorated (that is, the accuracy of the emitted beam is deteriorated due to the side lobe Ls). The control unit 13 does not greatly affect the determination as to whether or not the vehicle can join the lane on the right.

  Further, at t1 between times t0 and t2, the other vehicle V2 is caused by a beam emitted toward the partial areas B4 and B5 (that is, the first range including the front direction y) on the right side of the host vehicle V1. Be captured. When the other vehicle V2 is traveling in front of the antenna array 11 as described above, it is required to correctly derive the distance to the other vehicle V2 in order to determine whether or not the vehicle can join the lane on the right.

  However, if the side lobe Ls is not sufficiently suppressed even though the beams are emitted to the partial areas B4 and B5, an undesired object is generated based on the return wave from the undesired partial areas B3 and B6. In some cases, the distance and direction of the mark were derived.

[2.3 Radar Device 1 of the Present Disclosure]
In view of the above problems, the present inventor has come up with an in-vehicle radar device 1 described in detail below. The in-vehicle radar device 1 will be described in detail below with reference to FIGS. 4 and 5 in addition to FIGS. 1 to 3 used in the above description.

  In FIG. 1, the in-vehicle radar device 1 is different from the in-vehicle radar device 5 in that the contents of control by the control unit 13 (see FIG. 4) are different. Other than that, there is no difference between the in-vehicle radar devices 1 and 5. Therefore, in the in-vehicle radar device 1, the same reference numerals are assigned to the components corresponding to the configuration of the in-vehicle radar device 5, and description thereof is omitted.

  In FIG. 4, the control unit 13 uses the instruction from the navigation ECU connected thereto as a trigger to determine whether or not the range in which the beam is emitted this time is the first range during the lane merging support (step S001). ).

  If the first range is determined (YES in step S001), the control unit 13 compares with the gain of the power amplifier 23 connected to the antenna element 111 belonging to the second antenna group 117, assuming that it is necessary to accurately determine whether or not to join. Then, the gain of the power amplifier 23 connected to the antenna element 111 belonging to the first antenna group 115 is reduced (step S003). With this processing, when the radar apparatus 1 radiates electromagnetic waves in the first range, the radiation intensity of the electromagnetic waves from the antenna elements 111 belonging to the second antenna group 117 is radiated from those belonging to the first antenna group 115. Greater than strength.

  Specifically, as shown in Table 1 below, the gain of the power amplifier 23 is set so that the gain decreases from the center toward the antenna elements 111 at both ends.

  Here, it is assumed that at least a part of the integrated circuit constituting the in-vehicle radar device 1 is manufactured by a fine CMOS process. The withstand voltage of such an integrated circuit is smaller than that of other processes, and as a result, the intensity of the modulation signal supplied to each antenna element 111 is limited. The upper limit of the gain of the power amplifier 23 connected to the second antenna group 117 is preferably determined based on the withstand voltage of the integrated circuit manufactured by the CMOS process.

  In Table 2 below, suffixes a, b,..., H are added from the one end antenna element 111 to the other end antenna element 111 in the predetermined direction x.

  Further, the right column of Table 2 below shows the gain of the antenna element 111 obtained in step S005 for comparison.

  Although details will be described later by adjusting the gain in step S003, the gain of the side lobe can be sufficiently suppressed without significantly reducing the gain of the main lobe in the outgoing beam to the first range.

  On the other hand, if the second range is determined in step S001 (NO in step S001), the control unit 13 determines that it is not necessary to accurately determine whether or not to join, and all the antenna elements 111 belonging to the first antenna group and the second antenna group 117 are determined. The gain of the power amplifier 23 connected to is relatively increased (step S005).

  The gain of the power amplifier 23 in step S005 is determined based on the withstand voltage of the integrated circuit manufactured by the CMOS process, as in step S003.

  When the radar apparatus 1 radiates electromagnetic waves in the second range by step S005 as described above, the radiation intensity of the electromagnetic waves from the antenna elements 111 belonging to the first antenna group 115 and the second antenna group 117 is made the same. It becomes possible.

  Although the details will be described later by adjusting the gain in step S005, the gain of the main lobe and the gain of the side lobe can be maximized in the outgoing beam to the second range.

  Steps S001 to S005 as described above are repeated, for example, while an application for lane merging support is being executed (step S007).

[2.4 Operation / Effect of Radar Device 1 of Present Disclosure]
In FIG. 5, the characteristic curve C1 of the gain with respect to the angle of the beam emitted from the antenna array 11 toward the first range by executing step S003 is indicated by a solid line. The front direction y is 0 °.

  Further, for comparison, a characteristic curve C2 of the gain with respect to the angle of the outgoing beam to the first range when the gain of all the power amplifiers 23 is relatively increased is shown by a broken line for comparison.

  By executing step S003, the gain of the power amplifier 23 connected to the antenna elements 111 at both ends is made smaller than that of the central antenna element 111. In other words, the control unit 13 performs control so that the radiation intensity from each antenna element 111 constituting the second antenna group 117 is greater than the radiation intensity from each antenna element 111 constituting the first antenna group 115. As a result, each side lobe Ls1 in the characteristic curve C1 is greatly suppressed compared to each side lobe Ls2 in the characteristic curve C2.

  However, as the radar apparatus 1, a beam obtained by synthesizing electromagnetic waves from the plurality of antenna elements 111 is emitted to the first range including the front direction y, so the main lobe Lm1 of the characteristic curve C1 is theoretically Even if compared with the main lobe Lm2 of the characteristic curve C2, it is not so suppressed.

  From the above, according to the present radar apparatus 1, the main lobe Lm1 is suppressed while suppressing the side lobe Ls1 by performing gain adjustment in a limited manner in step S003 on the first range including the front direction y. It is possible to obtain a sufficient measurable distance by using. Therefore, even when the other vehicle V2 is traveling in a position away from the antenna array 11 in the front direction y as shown at time t1 in FIG. 3, the other vehicle V2 is suppressed while suppressing erroneous detection by the side lobe Ls1. It is possible to correctly derive the distance up to. As a result, the control unit 13 can correctly determine whether or not to merge into the adjacent lane while executing the application for supporting lane merge.

  Further, by executing step S005, the gains of the power amplifiers 23 connected to all the antenna elements 111 are set to be the same. In other words, the control unit 13 performs control so that the radiation intensities from the antenna elements 111 constituting the first antenna group 115 and the second antenna group 117 are the same. As a result of this processing, it is possible to obtain a sufficient measurable distance with respect to the second range.

[2.5 Modification]
By the way, if importance is placed on the suppression of the side lobe of the outgoing beam, for example, in the m antenna elements 111, it is necessary to finely adjust a large attenuation of 9 dB at the maximum from the center to the ends. come. It is very difficult to guarantee such specifications in consideration of manufacturing variations in the process. In particular, power calibration at the time of shipment of the radar apparatus 1 is often performed only for the maximum power, and when a large amount of attenuation is used as a specification, the error often becomes a problem.

  Therefore, paying attention only to the strength of side lobes adjacent on both sides of the main lobe, which is regarded as a problem in the lane merge support, out of the m antenna elements 111, the four antenna elements 111 belonging to the first antenna group 115 On the other hand, the gains of the remaining antenna elements 111 belonging to the second antenna group 117 are reduced by the same 6 dB without reducing the gain (see Table 3 below). According to this method, as shown in the characteristic curve of FIG. 6 (that is, the characteristic curve of the gain of the outgoing beam to the first range with respect to the angle) C3, the side lobe adjacent to the main lobe that is important when assisting lane merging is provided. The level of can be effectively reduced.

  In FIG. 6, a characteristic curve C4 similar to the characteristic curve C2 in FIG. 5 is also shown for comparison.

[3 Notes]
In the above description, the control unit 13 adjusts the gain of each power amplifier 23 in order to adjust the distribution of gain from the antenna array 11. However, the present invention is not limited to this, and the control unit 13 may adjust the gain distribution by adjusting the gain of each amplifier 21 or adjusting the amplitude of the baseband signal.

  In the above description, the distribution of the radiation intensity from each antenna element 111 is symmetric with respect to the front direction y. However, the distribution is not limited to this, and the distribution may be asymmetric.

  The vehicle-mounted radar device, the antenna array control method, and the program according to the present disclosure can obtain a sufficient measurable distance while suppressing side lobes, and are used for lane merging support, lane change support, automatic parking support, etc. It is suitable for.

DESCRIPTION OF SYMBOLS 1 In-vehicle radar apparatus 11 Antenna array 111 Antenna element 115 1st antenna group 117 2nd antenna group 13 Control part

Claims (7)

Of m antenna elements (m is an integer of 3 or more) arranged in a predetermined direction, a first antenna group including at least antenna elements at both ends, and a second antenna group including antenna elements not included in the first antenna group A second antenna group including at least a central antenna element in the predetermined direction, and an antenna array comprising:
When radiating an electromagnetic wave in a first range including at least the front direction of the antenna array, control is performed so that the radiant intensity of the electromagnetic wave from the second antenna group is greater than the radiant intensity of the electromagnetic wave from the first antenna group. A control unit;
An on-vehicle radar device comprising: The control unit, when radiating electromagnetic waves toward the second range other than the first range, controls the radiation intensity from the plurality of antenna elements to be the same,
The on-vehicle radar device according to claim 1. When m is an even number, the second antenna group includes four or more antenna elements including the central antenna element and continuing in the predetermined direction;
When m is an odd number, the second antenna group includes three or more antenna elements including the central antenna element and continuing in the predetermined direction.
The on-vehicle radar device according to claim 1. When the control unit radiates electromagnetic waves toward the first range, the radiation intensity from each antenna element from the first antenna group is the same, and from each antenna element of the second antenna group Control it to be smaller than the radiant intensity,
The on-vehicle radar device according to claim 1. When the control unit radiates electromagnetic waves to the first range when changing lanes, the electromagnetic wave radiation intensity from the second antenna group is greater than the electromagnetic wave radiation intensity from the first antenna group. Control,
The on-vehicle radar device according to claim 1. Of m antenna elements (m is an integer of 3 or more) arranged in a predetermined direction, a first antenna group including at least antenna elements at both ends, and a second antenna group including antenna elements not included in the first antenna group And a second antenna group including at least a central antenna element in the predetermined direction, and a method for controlling an antenna array, comprising:
When radiating an electromagnetic wave in a first range including at least the front direction of the antenna array, control is performed so that the radiant intensity of the electromagnetic wave from the second antenna group is greater than the radiant intensity of the electromagnetic wave from the first antenna group. Step,
An antenna array control method comprising: Of m antenna elements (m is an integer of 3 or more) arranged in a predetermined direction, a first antenna group including at least antenna elements at both ends, and a second antenna group including antenna elements not included in the first antenna group And a second antenna group including at least a central antenna element in the predetermined direction, and a program for controlling an antenna array comprising:
On the computer,
When radiating electromagnetic waves to the first range including at least the front direction of the antenna array, the radiation intensity of the electromagnetic waves from the second antenna group is processed to be greater than the radiation intensity of the electromagnetic waves from the first antenna group,
A program that executes

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