JP6491254B2 - Antenna device and radar device - Google Patents

Description

  The present invention relates to an antenna device including an array type antenna and a radar device that detects an object using the antenna device.

  Conventionally, various radar devices (radar sensors) that transmit a transmission wave to a detection target region, receive a reflected wave from an object, and detect the object have been devised. As such a radar apparatus, a plurality of transmission antennas and reception antennas are arranged at regular intervals, and the direction in which an object exists is detected from the correlation of signals obtained by combining different transmission antennas and reception antennas. Is known to do.

  It is known that the angular resolution increases as the number of transmission antennas or reception antennas increases in the radar apparatus. Patent Document 1 below discloses a technique for improving angular resolution by arranging reception antennas at equal intervals and setting the intervals between the reception antennas to be equal to or greater than a half wavelength of a transmission wave.

JP 2008-134223 A

  The angular resolution can be ensured by increasing the number of antennas. On the other hand, there is a problem that the antenna device becomes larger as the number of antennas increases, and the number of transmission / reception circuits increases to increase power consumption.

  The present invention has been made in order to solve the above-described problem, and by reducing the number of antennas while ensuring the angular distance and the angular resolution, the antenna can be reduced in size and reduced in power consumption. An object is to provide a device and a radar device.

  (1) An antenna device according to the present invention includes a transmission antenna and a transmission antenna on a plane having a coordinate axis that is an angle measurement direction axis corresponding to an angle measurement direction and an angle measurement orthogonal axis orthogonal to the angle measurement direction axis. A plurality of receiving antennas having a constant positional relationship in the direction of the angle-measuring orthogonal axis with respect to each other and having different angle-measuring direction coordinates, and detecting a receiving direction within a angle measuring plane including the angle measuring direction axis The plurality of receiving antennas are formed by forming a plurality of receiving antenna arrays in which the plurality of receiving antennas are arranged in the angle-measuring direction and the angle-orthogonal coordinates are different from each other. An antenna is provided for each receiving antenna array having the positional relationship, forms an antenna pair with the receiving antenna array, and measures the receiving antenna with respect to the transmitting antenna with the antenna pair. Assuming that the difference in direction coordinates is a relative coordinate, the absolute value of the relative coordinate difference between the receiving antennas in all combinations of the two receiving antennas is such that the tolerance is less than a half wavelength of the transmission wave and the number of terms is The value of each term of an arithmetic sequence that is a predetermined number equal to or greater than the total number of the receiving antennas is taken, and the positional relationship in the angle measurement direction between any two of the antenna pairs is the receiving antenna in any one of the antenna pairs. The arrangement range of the angle measurement direction of the row includes the arrangement range of the reception antenna row of the other antenna pair in the angle measurement direction.

  (2) In the antenna device described in (1) above, the difference between the tolerance and the angle measurement direction coordinate of the transmission antenna in the two arbitrary antenna pairs can be a half wavelength of the transmission wave.

  (3) Another antenna device according to the present invention includes a receiving antenna on a plane whose coordinate axis is an angle measuring direction axis corresponding to an angle measuring direction and an angle measuring orthogonal axis orthogonal to the angle measuring direction axis, A plurality of transmitting antennas having a constant positional relationship in the direction of the angle-measuring orthogonal axis with respect to the receiving antenna and having different angle-measuring direction coordinates are arranged, and the receiving direction in the angle measuring plane including the angle measuring direction axis The plurality of transmission antennas form a plurality of transmission antenna arrays in which the plurality of transmission antennas are arranged in the angle measuring direction and the angle measurement orthogonal coordinates are different from each other, The reception antenna is provided for each transmission antenna array having the positional relationship, forms an antenna pair with the transmission antenna array, and the transmission antenna for the reception antenna in the antenna pair Assuming that the difference in the angle measurement direction coordinates is a relative coordinate, the absolute value of the difference between the relative coordinates between the transmission antennas in all combinations of the two transmission antennas is such that the tolerance is equal to or less than a half wavelength of the transmission wave. The value of each term of an arithmetic progression that is a predetermined number equal to or greater than the total number of the transmission antennas is taken, and the positional relationship in the angle measurement direction between any two of the antenna pairs is the one in the antenna pair. The arrangement range of the transmission antenna array in the angle measurement direction includes the arrangement range of the transmission antenna array in the angle measurement direction in the other antenna pair.

  (4) A radar apparatus according to the present invention includes any one of the antenna apparatuses described in (1) to (3) above, and is a radar apparatus that detects a target object. A transmission / reception processing unit that transmits the transmission wave by the selected antenna pair and obtains a reception result, and a plurality of the receptions obtained by the transmission / reception processing unit by the time-division transmission processing for each antenna pair Combining means for combining the result as a reception result of the virtual antenna related to one virtual transmission processing, and the reception corresponding to the direction in which the target object exists based on the reception result combined by the combining means Detection processing means for detecting a direction.

  According to the present invention, it is possible to obtain an antenna device and a radar device in which the number of array antennas is reduced while ensuring the angular distance and the angular resolution, and the size is reduced and the power consumption is reduced.

It is a schematic diagram which shows the structural aspect of an array type antenna. 1 is a schematic block configuration diagram of a radar apparatus according to an embodiment of the present invention. It is a typical front view of the antenna apparatus for demonstrating an antenna pair. It is a typical front view of the antenna device explaining the 1st example of antenna arrangement concerning the embodiment of the present invention. It is a typical front view of the antenna apparatus made into a comparative example with the antenna apparatus shown in FIG.4 (b). It is a schematic flowchart of the angle measurement process in the radar apparatus which concerns on embodiment of this invention. It is a typical front view of the antenna device explaining the 2nd example of antenna arrangement concerning the embodiment of the present invention. It is a typical front view of the antenna apparatus explaining the 3rd antenna arrangement example which concerns on embodiment of this invention.

  Hereinafter, a radar apparatus 10 according to an embodiment of the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings. The radar apparatus 10 according to the present embodiment constitutes a monitoring apparatus that detects an object existing in a space in which the radar apparatus 10 is installed. For example, a person is a detection target object. The antenna device of the radar device 10 is configured by arranging a plurality of receiving antennas. The antenna device can scan the beam direction corresponding to the arrangement direction of the receiving antennas, and the radar device 10 detects the direction of the object that reflects the radio wave in the space to be monitored.

  The space in which the radar apparatus 10 is installed and monitored is, for example, the inside of a building (room or hallway) or the surrounding site (garden or parking lot). For the monitoring application, the radar device 10 is installed obliquely downward so as to look down from a high place in the space to be monitored so that its position can be detected from a nearby object to a distant object. When installed in this manner, by arranging (extending) the receiving antennas in the vertical direction, the vertical angular resolution of the receiving antennas, that is, the resolution in the depth direction and the height direction of the space to be monitored can be increased.

  Here, when extended antennas are used as the transmitting antenna and the receiving antenna, the width of the antenna pattern related to the extending direction (that is, the range of radiation or reception of radio waves on a plane along the extending direction) is narrow. On the other hand, the gain increases. That is, directivity can be given to the radiation characteristic of the antenna. Therefore, in this embodiment, an array type antenna extending in the vertical direction is used.

  FIG. 1 is a schematic plan view showing an example of an array type antenna. An array type antenna 500 shown in FIG. 1A has a patch element 501 made of planar conductors of a size that takes into account the wavelength of radio waves to be transmitted / received, arranged in a straight line, and connected by a conductor line 502 between them. For example, it is formed and arranged on the surface of a substrate made of a dielectric. In the figure, the position of the antenna center 503 is indicated by “x”, and the extending direction 504 of the array antenna is indicated by a double arrow. The size of the patch element in one array type antenna may be different. For example, in the array type antenna 510 shown in FIG. 1B, two areas at both ends of the three patch elements are larger than one in the center. It is set small. In addition, the number of patch elements constituting one array antenna is not limited to three. For example, more patch elements may be used, and the array antenna 520 shown in FIG. The elements are connected in a straight chain.

  FIG. 2 is a schematic block diagram of the radar apparatus 10 according to the embodiment. The radar apparatus 10 has an antenna apparatus 20 according to the present invention. The antenna device 20 includes a transmission antenna 21 and a reception antenna 22. The radar apparatus 10 further includes a receiver 23, a switch 25, a transmitter 30, an analog-digital (A / D) converter 40, a modulation signal generator 50, a switch signal generator 60, a distance measurement and angle processing unit 70, An output unit 80 is provided.

  Hereinafter, each part of the radar apparatus 10 will be described.

  The antenna device 20 includes a planar substrate and a housing that protects the substrate. The transmitting antenna 21 and the receiving antenna 22 are formed by arranging a conductor pattern on a substrate surface made of a dielectric, for example. A plurality of transmission antennas 21 and reception antennas 22 are formed. In the configuration of FIG. 2, the antenna device 20 includes n transmission antennas 21-1 to 21-n and m (m> n) reception antennas 22-1 to 22-m. Each of the transmission antennas 21 and each of the reception antennas 22 is an array antenna having a linear conductor pattern including a plurality of patch elements arranged on a straight line and a conductor line connecting them.

  The transmission antenna 21 radiates a radio wave in a microwave band (for example, 24 GHz) according to a signal transmitted from the transmitter 30. The receiving antenna 22 receives the radio wave reflected by the object. The specific arrangement of the transmission antenna 21 and the reception antenna 22 will be described later. The reception antennas 22 are arranged in n columns, and one transmission antenna 21 is provided corresponding to each column of the reception antennas 22. Make an antenna pair with the antenna array.

  The switching signal generator 60 generates a switching signal that represents a timing for transmitting and receiving a plurality of (n sets in the present embodiment) antenna pairs constituting the antenna device 20 in a time division manner, and the modulation signal generator 50, The data is input to the switch 25 and the distance measurement and angle processing unit 70. In the present embodiment, it is assumed that the switching signal generator 60 generates a switching signal for sequentially switching antenna pairs at 4 kHz.

  The modulation signal generator 50 generates a modulation signal in FMCW (Frequency Modulated Continuous Wave) system. For example, the modulation signal generator 50 generates a triangular wave signal as the modulation signal. The modulation signal generator 50 generates a symmetric triangular wave in synchronization with the switching signal input from the switching signal generator 60, and realizes one cycle frequency sweep in the FMCW method for each antenna pair. The modulation signal may be a sawtooth wave instead of a symmetric triangular wave.

  The transmitter 30 generates a radio wave whose frequency changes according to the modulation signal input from the modulation signal generator 50. For example, the transmitter 30 receives a symmetrical triangular wave as a modulation signal, performs frequency up / down sweep, and generates an FMCW signal whose frequency changes in a triangular wave shape with respect to time. The frequency shift width can be set to, for example, 24.06 to 24.24 GHz.

  The switch 25 performs a switching process of selecting any one of the transmission antennas 21 according to the switching signal from the switching signal generator 60 and connecting to the transmitter 30. In this embodiment, as described above, the transmission antenna 21 is sequentially switched at 4 kHz to transmit radio waves.

  The receiver 23 is provided corresponding to each receiving antenna 22. That is, receivers 23-1 to 23-m are provided corresponding to the receiving antennas 22-1 to 22-m, respectively. Each receiver 23 detects and amplifies the reception signal input from the corresponding reception antenna 22, shapes the waveform of the amplified detection signal by filtering processing, and outputs the waveform to the A / D converter 40.

  The A / D converter 40 converts the result of waveform shaping by each receiver 23 into a digital value, and outputs the digital value to the distance measuring and angle processing unit 70. The A / D converter 40 is assumed to be able to input in multiple channels so that a plurality of signals simultaneously received by the m receiving antennas 22 and output in parallel from the receiver 23 can be converted into digital values.

  The distance measurement and angle processing unit 70 calculates the distance and angle of the object (person) with respect to the radar apparatus 10 using the reception result input from the A / D converter 40. The distance measurement and angle processing unit 70 acquires the reception result of the transmission antenna 21 that radiates radio waves and the reception antenna 22 that forms an antenna pair in synchronization with the switching signal input from the switching signal generator 60, and performs distance measurement. Used for corner processing.

  The radar apparatus 10 according to the present invention switches a plurality of antenna pairs in accordance with a switching signal from the switching signal generator 60 and acquires a reception result for each antenna pair. An antenna is formed to perform distance measurement and angle measurement processing. That is, the radar apparatus 10 combines the reception results of different antenna pairs into a virtual antenna reception result, and uses this to perform ranging and angle measurement processing.

  Here, since a plurality of antenna pairs transmit and receive in a time division manner, reception results of different antenna pairs can be obtained at different timings. Therefore, the distance measurement and angle processing unit 70 temporarily stores the reception result for each antenna pair obtained from the A / D converter 40 in the buffer memory. For example, the distance measurement angle processing unit 70 stores the reception results obtained by transmission / reception for each of the n pairs of antennas corresponding to the n consecutive switching signals of the switching signal generator 60 as one set. One distance measurement and angle measurement process is performed based on the stored one set of reception results. Note that the buffer memory can be configured to overwrite the processed reception results sequentially with new reception results.

  In the present embodiment, the FMCW method is used for the distance measurement process, and the beam forming method is used for the angle measurement process. However, the present invention is not limited to this, and another method that can be appropriately replaced may be used.

  The output unit 80 is a communication interface for outputting the distance and angle obtained by the distance measurement and angle processing unit 70 to an external device. As appropriate, it is realized according to standards such as Ethernet (registered trademark) and RS232C.

  Incidentally, in the configuration of the radar apparatus 10 described above, the switching signal generator 60, the modulation signal generator 50, the transmitter 30, the switching unit 25, the receiver 23, and the A / D converter 40 each include a plurality of antenna pairs. A transmission / reception processing unit that selects by division, transmits a transmission wave by the selected antenna pair, and acquires a reception result is configured. Further, the distance measurement and angle processing unit 70 uses the transmission / reception processing means to obtain a plurality of reception results obtained by the time-division transmission processing in units of antenna pairs, and the virtual antenna reception results related to one virtual transmission processing. And a detection processing means for detecting the reception direction corresponding to the direction in which the target object exists based on the reception result synthesized by the synthesis means.

  Next, the antenna pair will be further described. FIG. 3 is a schematic front view of an antenna device in which an array type antenna is arranged for explaining an antenna pair. The antenna device has a transmission antenna and a reception antenna made of a conductor pattern formed on a plane.

  In FIG. 3, the y-axis and z-axis of the orthogonal coordinate system xyz are the horizontal and vertical directions along the plane of the antenna device, respectively, and the x-axis is the normal direction of the plane of the antenna device. 3 shows a state in which the transmission antenna 21 and the reception antenna 22 are arranged on the substrate along the yz plane. The arrangement shown in FIG. 3 is for explaining the antenna pair, and is not the arrangement itself of the transmission antenna 21 and the reception antenna 22 in the antenna apparatus 20 of the radar apparatus 10 of the present embodiment.

  FIG. 3 shows a configuration in which angle measurement and distance measurement are performed by receiving radio waves radiated from one transmission antenna by a plurality of reception antennas arranged in the angle measurement direction. Specifically, in FIG. Is the direction of angle measurement. That is, among the coordinate axes that define the yz plane that is the substrate surface of the antenna, the z axis is the angle measurement direction axis, and the reception direction is detected within the angle measurement surface including the angle measurement direction axis. In this embodiment, the angle measuring surface is a surface orthogonal to the substrate, that is, the xz plane. On the other hand, the y-axis is an axis orthogonal to the direction of angle measurement and will be referred to as an angle measurement orthogonal axis. The positional relationship of the plurality of reception antennas with respect to the transmission antenna in the direction of the angle-measuring orthogonal axis is fixed, thereby avoiding unnecessarily complicated ranging and angle-measurement processing.

  Each of the two transmitting antennas 21 and the six receiving antennas 22-1 to 22-6 shown in FIG. 3 is an array antenna described with reference to FIG. 1, and shows an example having three patch elements arranged in the z-axis direction. ing. As already described, by using an array antenna extending in the angle measuring direction (z-axis direction), the beam width in the xz plane can be narrowed (having directivity).

  The receiving antennas 22-1 to 22-3 are arranged in a line on the straight line in the z-axis direction, which is the angle measuring direction, and similarly, the receiving antennas 22-4 to 22-6 are also arranged in a line on the straight line in the z-axis direction. ing. A row of the receiving antennas 22 arranged in the angle measuring direction is a receiving antenna row. That is, the receiving antennas 22-1 to 22-3 constitute one receiving antenna row 220, and the receiving antennas 22-4 to 22-6 constitute another receiving antenna row 221. The receiving antenna arrays 220 and 221 are arranged at positions where the y-coordinates that are angle-measuring orthogonal coordinates are different from each other, that is, at positions that are shifted in the direction of the angle-measuring orthogonal axis.

  Two transmitting antennas 21 are arranged corresponding to two receiving antenna arrays, the transmitting antenna 21-1 and the receiving antenna array 220 form one antenna pair, and the transmitting antenna 21-2 and the receiving antenna array 221 are already present. One antenna pair is formed. As described above, the positional relationship of the transmitting antennas 21 corresponding to the receiving antenna arrays 220 and 221 in the angle-measurement orthogonal axis direction is set to be constant. That is, the difference between the y coordinate of the receiving antenna array 220 and the y coordinate of the transmitting antenna 21-1 is the same as the difference between the y coordinate of the receiving antenna array 221 and the y coordinate of the transmitting antenna 21-2. In addition, the antenna pairs are arranged in parallel with each other on the substrate.

  Next, a method for arranging the transmitting antenna 21 and the receiving antenna 22 in the antenna device 20 according to the present invention will be described. The angle measuring direction axis and the angle measuring orthogonal axis of the antenna device 20 according to the embodiment are the same as those defined in the description of FIG. That is, the z axis is the angle measuring direction axis, and the y axis is the angle measuring orthogonal axis.

  Here, when the arrangement period of the array antenna becomes larger than the half wavelength of the transmitted / received radio wave, a virtual image is generated in the process of estimating the arrival angle of the received wave. That is, in order to eliminate the influence of the virtual image, it is necessary to set the arrangement period to a half wavelength or less. However, as shown in FIG. 3, when the array antenna is in the same longitudinal direction and array direction, if the array antenna is arranged on the same straight line with a period of less than half wavelength, the conductors of adjacent array antennas Pattern interference is likely to occur. In other words, when the receiving antennas that are array antennas extending in the angle measuring direction (z-axis direction) are arranged in a line in the angle measuring direction, the receiving antennas tend to physically overlap, and the angle of the receiving antenna in the angle measuring direction is increased. As a result, it is difficult to suppress the virtual image, or there is a problem that the angle measurement range in which a suitable angle measurement resolution in the z-axis direction is obtained becomes narrow.

  When interference occurs between the receiving antennas when they are arranged in a line in this way, the present invention avoids the interference by disposing one of the interfering receiving antennas in the direction of the angle-measurement orthogonal axis (y-axis). As a result, a receiving antenna with a different position in the angle-measurement orthogonal axis direction is generated. Form. Specific examples will be described below.

  The transmitting antenna 21 and the receiving antenna 22 of the antenna device 20 of the specific example are array antennas in which three patch elements are arranged in the angle measuring direction (z-axis direction), similarly to the transmitting antenna and the receiving antenna of FIG. The shape and size are common to each other. In the following example, the size of each antenna in the angle measuring direction is larger than 3λ / 2 and smaller than 2λ. Further, the distance w in the direction of the angle-measurement orthogonal axis (y-axis) used in the following example is set to a value larger than the size of each antenna in the direction of the angle-measurement orthogonal axis.

  The patch element is a size that takes into account the wavelength of radio waves to be transmitted and received. While securing the sensitivity as an antenna, the patch element is connected in the direction of angle by connecting a plurality of patch elements in the direction of angle. It becomes possible to have sex.

  Further, the transmission antenna and the reception antenna may include patch elements having different sizes as shown in FIG. 1B, or may be configured by a plurality of patch elements other than three as shown in FIG. 1C. .

  One feature of the radar apparatus 10 of this embodiment is that it has a function of measuring angles in the z-axis direction by arranging receiving antennas extending in the z-axis direction at a plurality of different z coordinates. Therefore, in the following description, the aspect regarding the angle measurement in the z-axis direction in the radar apparatus 10 will be mainly described.

[First antenna arrangement example]
In the antenna device 20 of the first example described here, two transmission antennas (Tx1, Tx2) and four reception antennas (Rx1 to Rx4) are arranged. The antenna device 20 of the first example has a configuration corresponding to the beam forming method as the angle measurement method, and the interval between the antennas is 1 to 6 that is half the wavelength λ of the transmission radio wave (λ / 2) in the angle measurement direction. The receiving antennas 22 are arranged so that intervals of each integral multiple up to double are formed.

  FIG. 4 is a schematic front view of an antenna device for explaining a first example of the antenna device 20 according to the embodiment, that is, a view of a substrate on which a transmission antenna and a reception antenna are arranged viewed from the normal direction. FIG. 4A is a front view of an antenna device related to the antenna device 20 which is the first example of the embodiment, and FIG. 4B is a front view of the antenna device 20 which is the first example of the embodiment. It is.

  In the figure, the “x” mark represents the center of each antenna, the position of the antenna is the position of this “x” mark, and the distance or distance between the antennas is measured using this “x” mark as a reference point. In particular, the difference between the z coordinates, that is, the distance in the z-axis direction, which is the angle measuring direction, will be referred to as the angle measuring direction distance.

  In the antenna device of FIG. 4A, the z coordinates of the receiving antennas Rx2 to Rx4 are −λ / 2, −2λ, and −3λ, respectively, with the receiving antenna Rx1 as a reference. In this arrangement, the angular direction distance between the receiving antennas Rx1 and Rx2 is one half wavelength, the angular direction distance between the receiving antennas Rx3 and Rx4 is twice the half wavelength, and the angular direction between the receiving antennas Rx2 and Rx3. The distance is three times the half wavelength, the angular direction distance between the receiving antennas Rx1 and Rx3 is four times the half wavelength, the angular direction distance between the receiving antennas Rx2 and Rx4 is five times the half wavelength, and the receiving antennas Rx1 and Rx4 Is 6 times the half wavelength, and includes a distance in the angle measuring direction that is 1 to 6 times the half wavelength.

  On the other hand, in the z coordinate of the receiving antennas Rx1 to Rx4, interference occurs when the four receiving antennas are arranged in a line in the z-axis direction. In this regard, by dividing the receiving antennas Rx1 to Rx4 into a plurality of receiving antenna arrays, they can be arranged at the above z-coordinates without overlapping each other, and 1 to 6 times a half wavelength can be obtained with respect to the angular direction distance. .

  Specifically, the receiving antenna Rx2 having a distance in the angle measurement direction with respect to the receiving antenna Rx1 is λ / 2 and is shifted from the distance Rx1 by the distance w in the direction of the angle orthogonal axis, that is, the y-axis direction. For example, Rx2 is shifted from Rx1 in the positive direction of the y axis. Thus, by arranging Rx1 and Rx2 so as to be shifted in the y-axis direction, interference between the two can be prevented.

  A receiving antenna Rx3 having a distance of 2λ from the receiving antenna Rx1 can be arranged at the same y coordinate as the receiving antenna Rx1 without overlapping with the receiving antenna Rx1.

  The receiving antenna Rx4 whose distance in the angle measurement direction with respect to the reception antenna Rx3 is λ is arranged so as to be shifted in the direction of the angle measurement orthogonal axis, that is, the y-axis direction in order to avoid interference with Rx3. Here, since the angular distance between Rx4 and Rx2 is 5λ / 2, even if Rx4 is arranged at the same y coordinate as Rx2, no interference occurs. Therefore, Rx4 is arranged by being shifted by a distance w in the positive direction of the y-axis with respect to Rx3.

  As described above, the receiving antennas Rx1 to Rx4 are distributed and arranged in two receiving antenna arrays separated by a distance w in the direction of the angle-measurement orthogonal axis (y-axis), thereby obtaining an arrangement in which no interference occurs between the receiving antennas. .

  Two transmission antennas Tx1 and Tx2 are arranged corresponding to the two reception antenna arrays. Specifically, the transmission antenna Tx1 that forms an antenna pair with the first reception antenna array including the reception antennas Rx1 and Rx3 is arranged at a position shifted in the positive direction of the y axis from the first reception antenna array. In addition, the transmission antenna Tx2 that forms an antenna pair with the second reception antenna array including the reception antennas Rx2 and Rx4 is disposed at a position shifted in the positive direction of the y axis from the second reception antenna array. Note that the transmission antennas Tx1 and Tx2 are arranged within the arrangement range of each reception antenna array in the z-axis direction with respect to the z-axis direction.

  Here, as already described, the positional relationship in the direction orthogonal to the angle-measurement axis between the receiving antenna array and the transmitting antenna forming the antenna pair is constant regardless of the antenna pair. Therefore, in response to the second receiving antenna array being displaced from the first receiving antenna array by a distance w in the positive y-axis direction, the transmitting antenna Tx2 is y with respect to the transmitting antenna Tx1. They are displaced by a distance w in the positive direction of the axis.

  The antenna device 20 according to the first example of the embodiment shown in FIG. 4B includes a first antenna pair including the first reception antenna array (Rx1, Rx3) and the transmission antenna Tx1 in FIG. On the other hand, the second antenna pair consisting of the second receiving antenna array (Rx2, Rx4) and the transmitting antenna Tx2 is arranged so as to be shifted by the distance λ / 2 in the positive direction of the angle measuring direction axis (z axis). . By determining the position of the antenna pair in the angle measuring direction in this way, the range of the second receiving antenna array in the angle measuring direction includes the area of the first receiving antenna array in the angle measuring direction, and the antenna element is The size in the angle measuring direction is smaller than the arrangement in FIG.

  Incidentally, in the antenna device 20 of FIG. 4B, in the arrangement of the receiving antennas, the z coordinates of the receiving antennas Rx2 to Rx4 are 0, −2λ, and −5λ / 2, respectively, with the receiving antenna Rx1 as a reference. The angular distance between the two receiving antennas is only 1, 4, and 5 times the half wavelength for all combinations of receiving antennas. That is, when attention is paid only to the receiving antenna, it seems to be different from FIG. 4A in that there is no set of receiving antennas in which the angular distance is 2 times, 3 times, and 6 times the half wavelength.

  However, as described above, transmission / reception of radio waves is performed in units of antenna pairs, and distance measurement and angle measurement processing is affected by the distance in the angle measurement direction between the transmission antenna and the reception antenna forming the antenna pair. Therefore, the difference in the angle measurement direction coordinate of the reception antenna with respect to the transmission antenna in the antenna pair is referred to as a relative coordinate.

In order to enable detection of the receiving direction in the angle measuring direction, the arrangement of the transmitting antenna 21 and the receiving antenna 22 in the antenna device 20 is relative coordinates between the receiving antennas in all combinations of the two receiving antennas. the absolute value of the difference (represented by the symbol delta _S.) is set to a plurality of types exists. Furthermore, high measuring angular resolution as the number of the types is present from greater large delta _S is obtained. In this regard, FIG. 4 antenna device 20 of (b) can be obtained delta _S of six as described below, it is equivalent to FIG. 4 (a).

  First, the relative coordinate defined by the difference in the angular direction coordinate of the receiving antenna with respect to the transmitting antenna is based on the relative coordinate in the receiving antenna Rx1, and the receiving antenna that forms an antenna pair with the transmitting antenna Tx1 is the same as Rx1 with respect to Rx1. Only the difference in the z coordinate causes a difference in the relative coordinate. On the other hand, for the receiving antenna that forms an antenna pair with the transmitting antenna Tx2, the difference in the z coordinate of Tx2 with respect to Tx1 is relative to the difference in the z coordinate with respect to Rx1 of the receiving antenna. Contributes to the difference in coordinates. Specifically, when the relative coordinates of the receiving antenna Rx1 are set as the reference value α, the relative coordinates of the receiving antennas Rx2 to Rx4 are α−λ / 2, α−2λ, and α−3λ.

Therefore, the absolute value delta _S of difference in the relative coordinates, 1 times a half wavelength for receive antenna pairs (Rx1, Rx2), set 2 times the half-wavelength for (Rx3, Rx4), pairs (Rx2, Rx3) About half 3 times the wavelength, 4 times the half wavelength for the set (Rx1, Rx3), 5 times the half wavelength for the set (Rx2, Rx4), and 6 times the half wavelength for the set (Rx1, Rx4). Exist.

Incidentally, the antenna device 20 shown in FIG. 4 (b), the absolute value delta _S of difference in the relative coordinates of the receiving antenna to each other in all combinations of the two receive antennas, the tolerance is located below half the wavelength of the transmitted wave This is an example of a configuration that takes the value of each term of an equidistant sequence in which the number of terms is a predetermined number equal to or greater than the total number m of receiving antennas. Specifically, with respect to m = 4, delta _S is the tolerance and the initial term forming the arithmetic sequence is a lambda / 2, the number of terms is 6. Thus the type of required number of delta _S in the radar device 10 can be realized from a small number of receive antennas it. That is, the number of antennas can be reduced while ensuring the angular distance and the angular resolution, and the size can be reduced and the power consumption can be reduced.

FIG. 5 is a schematic front view of an antenna device as a comparative example to the antenna device 20 according to the embodiment shown in FIG. 5, a plurality of receiving antennas that is set to z coordinates at regular intervals (lambda / 2), shows a configuration of an antenna device for realizing the antenna device 20 and the same number of delta _S in Figure 4 (b). Specifically, in this configuration, seven reception antennas Rx1 to Rx7 are divided into four reception antenna arrays, and four transmission antennas are required. On the other hand, in the configuration of FIG. 4B, as described above, the number of reception antennas is four, the number of reception antenna columns is two, and the number of transmission antennas is two.

  Furthermore, in the antenna device 20 of FIG. 4B, the positional relationship between any two antenna pairs in the angle measurement direction is such that the arrangement range in the angle measurement direction of the reception antenna array in either one of the antenna pairs is the other antenna pair. This is an example of a configuration that includes the arrangement range of the receiving antenna array in the angle measurement direction, and as described above, the size in the z-axis direction is made smaller than the arrangement of FIG. Can do. In the configuration of FIG. 5, the angular distance between Rx1 and Rx7 whose z coordinates are farthest apart is 3λ, whereas in the configuration of FIG. 4B, the measurement of Rx1 and Rx4 whose z coordinates are farthest away is performed. The angular distance is 5λ / 2. That is, the configuration in FIG. 4B is smaller in the angle measuring direction (z-axis direction) than the configuration in FIG.

  FIG. 6 is a schematic flowchart of angle measurement processing in the radar apparatus 10 using the first example of the antenna apparatus 20 shown in FIG. Hereinafter, an operation related to the angle measurement process of the radar apparatus 10 will be described with reference to FIG.

  Each time the series of processes shown in FIG. 6 is performed once, an angle measurement result at a certain timing is obtained, and the radar apparatus 10 repeats the process, for example, to change the direction in which the moving object exists. Can be detected.

  As described above, the radar apparatus 10 performs transmission / reception processing by sequentially switching the antenna pair in synchronization with the switching signal generated by the switching signal generator 60. In addition, the radar apparatus 10 processes a received signal using the concept of a virtual antenna, which is a well-known technique in the field of a MIMO (multiple input multiple output) antenna, and performs angle measurement of the arrival direction of the received wave. In the signal processing based on the virtual antenna, reception results obtained at different timings for each antenna pair are combined, and thus the reception results obtained earlier among the reception results for each antenna pair are temporarily stored. For example, when reception results for all reception antennas are obtained, the angle measurement processing is performed by regarding the reception results as one reception result.

  Therefore, the radar apparatus 10 sequentially selects antenna pairs by the switching signal generator 60, performs transmission / reception processing for the selected antenna pairs (step S100), and stores reception results obtained thereby in the buffer memory (step S110). ) And do. In the first example of the antenna device 20 described here, there are two antenna pairs, so steps S100 and S110 are executed twice.

  For example, when the switch 25 selects the transmission antenna Tx1 in accordance with the switching signal of the switching signal generator 60, the electromagnetic wave generated by the transmitter 30 is radiated from the transmission antenna Tx1 to, for example, a target space where object detection is performed. The receiving antennas Rx1 to Rx4 receive radio waves reflected by an object existing in the space. The received signal is detected and amplified by the receiver 23, converted to a digital signal by the A / D converter 40, and output to the distance measuring and angle processing unit 70. Ranging and measuring unit 70 receives reception results of reception antennas Rx1 and Rx3 that constitute a reception antenna array that forms an antenna pair with transmission antenna Tx1 among reception results of Rx1 to Rx4 input from A / D converter 40. Memorize temporarily.

  Similarly, when transmission is performed from the transmission antenna Tx2, reception results of the reception antennas Rx2 and Rx4 are temporarily stored.

  The switching signal from the switching signal generator 60 is input to the receiver 23 or the A / D converter 40, and only the received signal of the receiving antenna that forms an antenna pair with the transmitting antenna that transmits radio waves is detected and amplified. , A / D conversion may be performed, and only the reception result of the reception antenna may be input to the distance measurement and angle processing unit 70.

  The distance measurement and angle processing unit 70 performs a fast Fourier transform (FFT) on the reception result of each reception antenna 22 stored in the buffer memory (step S120). Specifically, the reception results of the reception antennas Rx1 to Rx4 obtained by two transmissions / receptions corresponding to the antenna pair are converted from the time domain to the frequency domain by FFT.

The distance measurement and angle processing unit 70 calculates a cross-correlation matrix R (ω) based on the result of the FFT (step S130). Note that ω is an angular frequency, and R (ω) is a function of ω. When the result of FFT of the reception result of the reception antenna Rxk (k is a natural number of 1 to 4) is expressed as X _k (ω), the cross-correlation matrix R (ω) is given by the following equation. X _k (ω) ^* means a complex conjugate of X _k (ω). The radio wave reflected by the object and incident on the receiving antenna is a plane wave and is incident on each receiving antenna with the same amplitude. A (ω) represents the amplitude of the radio wave at the frequency ω. Δt represents the delay time of radio wave arrival between adjacent receiving antennas.

  When attention is paid to the matrix appearing on the right side of the equation (1), six types of phase components from exp (−jωΔt) to exp (−j6ωΔt) are included in the components below the diagonal component. This can perform angle measurement processing similar to that of the antenna device in which the seven receiving antennas shown in FIG. 5 are arranged at equally-spaced z coordinates, and this antenna device 20 can perform measurement similar to the antenna device of FIG. It shows that it has angular performance. Note that the matrix is a self-adjoint matrix, and components above the diagonal component are essentially the same as the components below the diagonal component except for the phase sign.

  The distance measurement and angle processing unit 70 extracts the matrix component from the lower left half of the cross-correlation matrix R (ω) shown in equation (1) calculated in step S130, and creates virtual reception data shown in the following equation. (Step S140).

  Then, the distance measurement and angle processing unit 70 calculates a cross-correlation matrix defined by the following equation using the virtual reception data created in step S140 (step S150).

  The distance measurement and angle processing unit 70 calculates the steering vector V (ω, θ) represented by the following equation, where θ is the angle representing the arrival direction of the reflected radio wave in the angle measurement plane including the angle measurement direction axis (step) S160). The order (number of components) of the steering vector V (ω, θ) corresponds to the number of components of virtual received data shown in equation (2). In the present embodiment, the angle measurement surface is the xz plane, and θ defines the direction directly in front of the radar apparatus 10, that is, the positive direction of the x axis as 0 degrees.

Here, I (ω, θ) is the directivity characteristic of the antenna, and c is the speed of light. Further, d _k (k is a natural number of 1 to 6) represents a difference in propagation path length of radio waves in each of six sets of receiving antennas having different angular distances.

  The distance measurement and angle processing unit 70 uses the steering vector V (ω, θ) obtained by the equation (4) to calculate a weight vector W (ω, θ) defined by the following equation, and this weight vector W Using (ω, θ) and the cross-correlation matrix of equation (3), an azimuth spectrum P (ω, θ) defined by the following equation is obtained (step S160). Note that the symbol [•] ′ means the complex conjugate transpose of [•].

  The distance measurement and angle processing unit 70 estimates the angle θ that gives a peak in the azimuth spectrum P (ω, θ) of the equation (5) as the arrival angle of the radio wave, and outputs it to the output unit 80 (step S170).

  On the other hand, the distance measurement processing is performed by the well-known FMCW method in this embodiment, but other well-known methods such as a Doppler method (two-frequency CW) may be used.

[Second antenna arrangement example]
In the first antenna arrangement example described above, the antenna apparatus 20 having two transmission antennas (Tx1, Tx2) and four reception antennas (Rx1 to Rx4) is shown. However, the arrangement of each antenna in the antenna apparatus 20 is as described above. Not limited to anything.

  Similarly, by arranging in exactly the same procedure, it is possible to reduce the number of transmission antennas and reception antennas, thereby reducing the power consumption associated therewith, and to reduce the size.

  For example, if two transmission antennas and five reception antennas are prepared, an antenna device having up to nine times the half wavelength can be realized.

  Alternatively, as shown in FIG. 7, when two transmission antennas and six reception antennas are prepared, an antenna device having up to 13 times the half wavelength can be realized.

  FIG. 7 is a schematic front view of an antenna device for explaining a second example of the antenna device 20 according to the embodiment, that is, a view of a substrate on which a transmission antenna and a reception antenna are arranged as viewed from the normal direction.

Considering the same as in the case of the first antenna arrangement example, the absolute value Δ _S of the difference between the relative coordinates in the antenna device 20 of FIG. 7 is set to 1 × a half wavelength for the set of receive antennas (Rx1, Rx2) ( Rx4, Rx5), (Rx5, Rx6) twice the half wavelength, the pair (Rx3, Rx4) three times the half wavelength, the pair (Rx4, Rx6) four times the half wavelength, the pair (Rx2, Rx3), (Rx3, Rx5) is 5 times the half wavelength, the pair (Rx1, Rx3) is 6 times the half wavelength, the set (Rx3, Rx6) is 7 times the half wavelength, and the set (Rx2, Rx4) is 8 times the half wavelength. , 9 times the half wavelength for the set (Rx1, Rx4), 10 times the half wavelength for the set (Rx2, Rx5), 11 times the half wavelength for the set (Rx1, Rx5), and half the wavelength for the set (Rx2, Rx6) 12 times (Rx1, Rx6) for becomes 13 times the half wavelength, it is possible to obtain the thirteen delta _S.

The antenna device 20 shown in FIG. 7, similarly to the antenna device 20 shown in FIG. 5 (b), the absolute value delta _S of difference in the relative coordinates of the receiving antenna to each other in all combinations of the two receive antennas This is an example of a configuration that takes the value of each term of the differential number sequence in which the tolerance is equal to or less than a half wavelength of the transmission wave and the number of terms is a predetermined number greater than or equal to the total number m of the receiving antennas. Specifically, with respect to m = 6, delta _S is the tolerance and the initial term forming the arithmetic sequence is a lambda / 2, the number of terms 13. Thus the kinds of the number of delta _S required by the radar device 10 can be realized from a small number of receive antennas it. That is, the number of antenna elements in the array antenna can be reduced, and the size can be reduced and the power consumption can be reduced.

[Third antenna arrangement example]
In the examples shown so far, the number m of receiving antennas is larger than the number n of transmitting antennas, and an integer multiple of a half wavelength is realized for the arrangement of receiving antennas. Ranging and angle measurement processing similar to that of each antenna device 20 described above can be realized even when the antenna device 20 having the arrangement is used.

That is, in the radar apparatus 10 of FIG. 2, the antenna apparatus 20 has a larger number n of transmission antennas 21 than the number m of reception antennas 22, and each of the plurality of transmission antennas 21 is aligned in the direction of the angle measuring direction axis. It can be set as the structure which has several transmission antenna row | line | columns from which orthogonal coordinates mutually differ. In the antenna arrangement in the antenna device 20, any two transmission antennas 21 whose difference in angle measurement direction coordinates is less than the length of the transmission antenna 21 in the angle measurement direction are arranged in different transmission antenna arrays, and receive antennas 22. Is provided for each transmission antenna array and forms an antenna pair with each transmission antenna 21 of the transmission antenna array. The positional relationship in the direction of the angle orthogonal axis between the transmitting antenna 21 and the receiving antenna 22 forming the antenna pair is fixed. Further, the absolute value delta _S of difference in the relative coordinates of the transmitting antenna to each other in all combinations of two transmission antennas, the tolerance is the predetermined number of the number of terms or less half wavelength or n of the transmitted wave arithmetically The antenna arrangement is determined so as to take the value of each term in the sequence. The positional relationship in the angle measurement direction of any two antenna pairs includes the range in the angle measurement direction of the transmission antenna array in any one antenna pair includes the range in the angle measurement direction of the transmission antenna array in the other antenna pair. It is considered to be a relationship.

  FIG. 8 is a schematic front view of an antenna apparatus for explaining a third example of the antenna apparatus 20 according to the embodiment, that is, a view of a substrate on which a transmission antenna and a reception antenna are arranged as viewed from the normal direction. FIG. 8A is a front view of an antenna apparatus related to the antenna apparatus 20 which is the third example of the embodiment, and FIG. 8B is a front view of the antenna apparatus 20 which is the third example of the embodiment. It is. FIG. 8 shows an example of an antenna arrangement in which the transmitting antenna 21 and the receiving antenna 22 are interchanged. Specifically, in this example, the transmitting antenna and the receiving antenna are interchanged in the antenna arrangement shown in FIG. FIG. 8A shows an arrangement in which the transmission antenna 21 and the reception antenna 22 are interchanged in FIG. 4A, and FIG. 8B shows the arrangement corresponding to the antenna device 20. FIG. 1 shows an arrangement in which the transmitting antenna 21 and the receiving antenna 22 are interchanged, each having four transmitting antennas 21 (Tx1 to Tx4) and two receiving antennas (Rx1, Rx2).

  8B, similarly to FIG. 5B, the antenna pair composed of the transmission antennas (Tx2, Tx4) and the reception antenna Rx2 has an arrangement shifted by a distance λ / 2 in the positive z-axis direction. .

  The radar device 10 using the antenna device 20 transmits electromagnetic waves from the transmission antennas Tx1 to Tx4 in a time division manner, receives the transmission antennas that perform transmission and the reception antennas that constitute the antenna pair, and temporarily stores the reception results. When the reception results corresponding to all the transmission antennas 21 are obtained, the distance measurement and angle processing unit 70 performs angle measurement processing.

There are four antenna pairs (Tx1, Rx1), (Tx2, Rx2), (Tx3, Rx1), and (Tx4, Rx2) in the antenna device 20 of FIG. 8B. Te, similar to the configuration of FIG. 4 (b), obtained delta _S of six, downsizing of the antenna device 20, power consumption can be reduced. The antenna device 20 can also be reduced in size by setting the z-coordinate so that the above-described inclusion relationship is realized for different transmission antenna arrays.

Incidentally, the radar device 10 having an antenna device 20 of FIG. 8 (b), as Txk (k is a natural number of 1-4.) The results of the FFT of the received data when sent from _{X k} (omega) Except for handling, ranging angle measurement can be performed by basically the same processing as the radar apparatus 10 having the antenna apparatus 20 of FIG. 4B.

  Further, the antenna arrangement 20 shown in FIG. 7 may be an antenna arrangement in which the transmitting antenna and the receiving antenna are interchanged.

  Thus, according to the arrangement in which the transmitting antenna and the receiving antenna are switched, the number of the receivers 23 can be reduced, so that the entire antenna device 20 can be reduced in size.

  In the above-described embodiment, in order to perform horizontal angle measurement, the radar apparatus 10 has a configuration in which a plurality of the above-described antenna apparatuses 20 are arranged in the horizontal direction, or an antenna pair that configures the above-described antenna apparatus 20. It can be set as the structure provided with the antenna apparatus extended and arranged in the horizontal direction.

Further, in the embodiment described above, the two receiving antennas to each other at the receiving antenna array (or two transmission antennas among at transmit antenna array) the minimum value of the absolute values delta _S of difference in the relative coordinate is a half wavelength Although an example has been described, the value can be made smaller than a half wavelength, and generation of a virtual image can be avoided if it is less than a half wavelength.

  10 radar device, 20 antenna device, 21 transmitting antenna, 22 receiving antenna, 23 receiver, 25 switch, 30 transmitter, 40 A / D converter, 50 modulation signal generator, 60 switching signal generator, 70 ranging Angle measurement processing unit, 80 output unit.

Claims (4)

A positional relationship between the transmission antenna and the direction of the angle orthogonal axis relative to the transmission antenna on a plane whose coordinate axis is the angle measurement direction axis corresponding to the angle measurement direction and the angle measurement orthogonal axis orthogonal to the angle measurement direction axis A plurality of receiving antennas having a constant angle measurement direction coordinate and different from each other, and an antenna device capable of detecting a reception direction within a measurement surface including the angle measurement direction axis,
The plurality of receiving antennas form a plurality of receiving antenna arrays in which the plurality of receiving antennas are arranged in the angle measuring direction and the angle measurement orthogonal coordinates are different from each other,
The transmitting antenna is provided for each receiving antenna array having the positional relationship, and forms an antenna pair with the receiving antenna array,
Assuming that the difference in the angular direction coordinate of the reception antenna with respect to the transmission antenna in the antenna pair is a relative coordinate, the absolute value of the difference in the relative coordinate between the reception antennas in all combinations of the two reception antennas Takes the value of each term in the differential number sequence where the tolerance is less than a half wavelength of the transmitted wave and the number of terms is a predetermined number greater than or equal to the total number of the receiving antennas,
The positional relationship between any two of the antenna pairs in the angle measurement direction is such that the arrangement range of the angle measurement direction of the reception antenna array in any one of the antenna pairs is equal to the position of the reception antenna array in the other antenna pair. The relationship includes the arrangement range in the direction of angle measurement,
An antenna device characterized by the above.   The antenna apparatus according to claim 1, wherein the difference between the tolerance and the angle measurement direction coordinate of the transmission antenna in the two arbitrary antenna pairs is a half wavelength of the transmission wave. The positional relationship between the receiving antenna and the direction of the angle orthogonal axis relative to the receiving antenna on a plane having the angle measuring direction axis corresponding to the angle measuring direction and the angle measuring orthogonal axis orthogonal to the angle measuring direction axis as a coordinate axis A plurality of transmission antennas having different angle measurement direction coordinates, and an antenna device capable of detecting a reception direction in an angle measurement plane including the angle measurement direction axis,
The plurality of transmission antennas form a plurality of transmission antenna arrays in which the plurality of transmission antennas are arranged in the angle measurement direction and the angle measurement orthogonal coordinates are different from each other,
The receiving antenna is provided for each transmitting antenna array having the positional relationship, and forms an antenna pair with the transmitting antenna array,
Assuming that the difference in the angular direction coordinate of the transmitting antenna with respect to the receiving antenna in the antenna pair is a relative coordinate, the absolute value of the relative coordinate difference between the transmitting antennas in all combinations of the two transmitting antennas Takes the value of each term in the differential number sequence where the tolerance is less than half the wavelength of the transmitted wave and the number of terms is a predetermined number greater than or equal to the total number of the transmitting antennas,
The positional relationship between any two of the antenna pairs in the angle measurement direction is such that the range of arrangement of the transmission antenna arrays in any one of the antenna pairs in the angle measurement direction corresponds to the transmission antenna array in the other antenna pair. The relationship includes the arrangement range in the direction of angle measurement,
An antenna device characterized by the above. A radar device comprising any one of the antenna devices according to claim 1 to detect a target object,
A transmission / reception processing means for selecting a plurality of antenna pairs in a time-sharing manner, transmitting the transmission wave by the selected antenna pairs, and obtaining a reception result;
Combining means for combining a plurality of reception results obtained by the time-division transmission processing in units of antenna pairs by the transmission / reception processing means as virtual antenna reception results for one virtual transmission processing;
Detection processing means for detecting the reception direction corresponding to the presence direction of the target object based on the reception result synthesized by the synthesis means;
A radar apparatus comprising:

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