JP6499217B2 - 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.

  Various radar devices have been devised that transmit a transmission wave to a detection target region, receive a reflected wave from an object, and detect the object. 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.

  The following Patent Document 1 exemplifies a radar device in which five receiving antennas are arranged in the horizontal direction at intervals of a half wavelength or more of a transmission wave. In the radar apparatus, a method of eliminating the influence of a virtual image caused by setting the antenna interval larger than a half wavelength by verifying the consistency of the movement history of the target and the antenna directivity pattern is shown.

  In the technique disclosed in Patent Document 1, it is assumed that the detection target (target) is an object such as a car having a constant reflection cross-sectional area.

JP 2008-134223 A

  However, with conventional technology, it is difficult to verify the consistency of a detection target whose reflection cross-section changes due to a change in orientation due to movement, or a detection target whose reflection cross-section changes due to a change in posture, such as a human being. There was a problem that the influence of could not be eliminated.

  Thus, in order to detect the existence direction of an object whose reflection cross section can change with high accuracy, it is necessary to increase the number of antennas and shorten the antenna interval. For example, the antenna interval needs to be a half wavelength of the transmission wave.

  On the other hand, when an array type antenna is used for a receiving antenna or a transmitting antenna, the width of an antenna pattern (that is, a range in which radio waves are radiated or received on a plane along the direction) in a direction in which the array of patch elements extends is narrow. On the other hand, the gain increases. That is, directivity can be given to the radiation characteristic of the antenna, and a long angle measurement distance can be secured (an angle can be measured far).

  An example of an array antenna is schematically shown in FIG. The array type antenna 500 is a linear array in which a plurality of patch elements 501 made of a planar conductor having a size that takes into account the wavelength of radio waves to be transmitted and received are arranged on a straight line and connected to each other by a conductor line 502. It is. The patch element 501 preferably has a long side having a half wavelength. In the figure, the position of the antenna center 503 is indicated by “x”.

  However, even if an array type antenna 500 is arranged side by side at a half-wavelength interval (interval between antenna centers) along the direction 504 in order to ensure a long angular distance while corresponding to an object whose reflection cross-section changes, the antenna There was a problem that they could not be physically placed due to interference.

  The present invention has been made to solve the above problems, and an antenna that facilitates the arrangement of an array type antenna that can ensure angle measurement accuracy and angle measurement distance even when a person whose reflection cross section changes is detected. An object is to provide a device and a radar device using the 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 measurement direction and the angle measurement orthogonal coordinates are different from each other. Any two receiving antennas whose angular coordinate difference is less than the length of the receiving antenna in the angle measuring direction are arranged in different receiving antenna arrays, and the transmitting antenna is connected to each receiving antenna. Provided for columns, form the receiving antenna array and antenna pair.

  (2) In the antenna device described in (1) above, the receiving antenna may be an array antenna in which a plurality of patch elements are connected in a straight line in the angle measurement direction.

  (3) In the antenna device described in (1) and (2) above, 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 two antennas of the reception antenna The absolute value of the difference between the relative coordinates between the receiving antennas in all combinations, each term of the equivalence 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 equal to or greater than the total number of the receiving antennas An antenna arrangement having a value of

  (4) 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, Any two of the transmission antennas whose difference in coordinate of the angle direction is less than the length of the angle of the transmission antenna is arranged in the transmission antenna row different from each other, and the reception antenna is each of the transmission antennas. It provided for containers columns, forming a respective transmit antenna and antenna pair of the transmission antenna array.

  (5) A radar apparatus according to the present invention includes the antenna apparatus according to any one of (1) to (4) above, and is a radar apparatus that detects a target object. Transmission / reception processing means for selecting a transmission and transmitting a transmission wave by the selected antenna pair and obtaining a reception result; and a plurality of the receptions obtained by the transmission / reception processing means in a time-division transmission process 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.

  ADVANTAGE OF THE INVENTION According to this invention, the antenna apparatus and radar apparatus which make arrangement | positioning of the array type antenna which can ensure an angular distance and angle resolution easy are obtained.

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 1st example of the antenna device which concerns on embodiment of this invention. FIG. 5 is a schematic flowchart of angle measurement processing in a radar device using the antenna device shown in FIG. 4. It is a typical front view of the 2nd example of the antenna device which concerns on embodiment of this invention. FIG. 7 is a schematic flowchart of angle measurement processing in a radar device using the antenna device shown in FIG. 6. It is a typical front view of the 3rd example of the antenna device 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 of the present embodiment constitutes a monitoring apparatus that detects an object existing in a space where the radar apparatus 10 is installed, and mainly uses a person as a detection target object. 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 way, by arranging (extending) the receiving antennas in the vertical direction, the angle measurement accuracy in the vertical direction of the receiving antennas, that is, the accuracy in the depth direction and the height direction of the space to be monitored can be improved. . The radar apparatus 10 basically transmits and receives radio waves of a predetermined frequency, and typically 24 GHz microwaves are used as the radio waves. Note that the frequency is not necessarily constant. For example, in the present embodiment, the radar apparatus 10 is a frequency modulation continuous wave radar (FM-CW radar). In this case, the frequency of the radio wave changes with a predetermined frequency shift width. The space where the radar apparatus 10 is installed and monitored may be indoors or outdoors.

  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 symmetrical 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 symmetric triangular wave as a modulation signal, performs frequency up / down sweep, and generates an FWCW 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, the beam width in the zx plane can be narrowed by using the array type antenna extending in the z-axis direction.

  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 y coordinates, which are angle-measuring orthogonal coordinates, are different from each other, that is, positions shifted in the y-axis direction.

  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, and the difference between the y coordinate of the receiving antenna array 221 and the y coordinate of the transmitting antenna 21-2 are the same. 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.

  As already described, when receiving antennas (see FIG. 1), which 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. Therefore, it is constrained to reduce the arrangement period of the receiving antenna in the angle measuring direction, and as a result, there is a problem that it becomes difficult to suppress the virtual image or the angle measuring range in which a suitable angle measuring resolution can be 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 different coordinates in the angle-measurement orthogonal axis direction is generated. In response to this, a transmission antenna is added, and the antenna pair described above is added to each reception antenna with different coordinates in the angle-measurement orthogonal axis direction. 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 connected linearly in the angle measuring direction, similar 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 orthogonal axis used in the following example is set to a value larger than the size in the direction of the angle orthogonal axis of each antenna.

  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]
FIG. 4 is a schematic front view of 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 as viewed from the normal direction. The antenna device 20 of FIG. 4 has a configuration corresponding to the beam forming method as an angle measurement method, and the interval between the antennas is 1 to 9 times the half of the wavelength λ (λ / 2) of the transmission radio wave in the angle measurement direction. 10 shows a state in which ten reception antennas 22 (Rx1 to Rx10) are arranged so that intervals of integer multiples are formed.

  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.

  The receiving antennas Rx1 to Rx10 have z coordinates arranged in this order, and the z coordinates are set at equal intervals. Specifically, the angular distance between any two receiving antennas adjacent to each other is λ / 2.

  As shown in FIG. 4, the size of each receiving antenna in the z-axis direction is such that if the receiving antennas Rx1 to Rx10 are arranged in a line in the angle measuring direction, they interfere with the three receiving antennas on both sides. For example, when attention is paid to the receiving antenna Rx1, the receiving antennas Rx2 to Rx4 overlap with the Rx1.

  Therefore, the receiving antenna Rx2 is arranged so as to be shifted from the receiving antenna Rx1 by the distance w in the direction of the angle-measurement 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.

  In order to avoid interference with the reception antennas Rx1 and Rx2, the reception antenna Rx3 is disposed, for example, by being shifted from the Rx2 by a distance w in the positive direction of the y axis.

  In order to avoid interference with the receiving antennas Rx1 to Rx3, the receiving antenna Rx4 is arranged, for example, further shifted from the Rx3 by a distance w in the positive direction of the y-axis.

  Accordingly, the receiving antennas Rx1 to Rx4 are arranged without overlapping in the angle measuring direction.

  Next, the receiving antenna Rx5 whose distance from the receiving antenna Rx1 is four times the half wavelength can be arranged at the same y coordinate as the receiving antenna Rx1 without overlapping with the receiving antenna Rx1.

  The positional relationship in the z-axis direction of the receiving antennas Rx6 to Rx8 with respect to the receiving antenna Rx5 is the same as the positional relationship in the z-axis direction of the receiving antennas Rx2 to Rx4 with respect to the receiving antenna Rx1, and the receiving antennas Rx6 to Rx8 are respectively receiving antennas. The distances w, 2w, and 3w are shifted from Rx5 in the positive direction of the y-axis. In this arrangement, the receiving antennas Rx6 to Rx8 are arranged at the same y coordinate as that of the receiving antennas Rx2 to Rx4, respectively, but the receiving antennas Rx2 and Rx6, the receiving antennas Rx3 and Rx7 are the same as the receiving antennas Rx1 and Rx5 do not interfere with each other. , And the receiving antennas Rx4 and Rx8 do not interfere with each other.

  Therefore, the receiving antennas Rx6 to Rx8 are also arranged without overlapping in the angle measuring direction.

  Similarly, the receiving antenna Rx9 whose angular direction distance from the receiving antenna Rx5 is four times the half wavelength can be arranged at the same y coordinate as the receiving antennas Rx1 and Rx5 without overlapping with the receiving antenna Rx5. Further, the receiving antenna Rx10 is arranged by shifting the distance w from the receiving antenna Rx9 in the positive direction of the y axis, thereby avoiding interference with Rx9 and does not interfere with Rx6 having the same y coordinate.

  In this way, the receiving antennas whose size in the z-axis direction is greater than 3λ / 2 and less than 2λ have four consecutive ranges in the angle measurement direction (z-axis direction) that overlap each other with respect to the position in the angle measurement direction. In this case, by arranging the receiving antennas in order in four columns having different angle-measurement orthogonal coordinates (y-coordinates), an arrangement in which the receiving antennas do not interfere with each other can be obtained.

  The minimum number of receiving antenna arrays in which receiving antennas are arranged without causing interference differs depending on the size La of the receiving antenna in the angle measuring direction and the arrangement period Pa in the angle measuring direction of the receiving antenna that is equally spaced, Specifically, int (La / Pa) +1, that is, a value larger by 1 than the integer quotient obtained by dividing La by Pa.

  On the other hand, a transmission antenna is provided for each reception antenna array, and the same number of antenna pairs as the number of reception antenna arrays is provided. Specifically, the transmission antenna Tx1 that forms an antenna pair with the first reception antenna array including the reception antennas Rx1, Rx5, and Rx9 is disposed at a position that is shifted in the positive direction of the y axis from the reception antenna array. In addition, a transmission antenna Tx2 that forms an antenna pair with a second reception antenna array that includes reception antennas Rx2, Rx6, and Rx10; a transmission antenna Tx3 that forms an antenna pair with a third reception antenna array that includes reception antennas Rx3 and Rx7; The transmission antenna Tx4 that forms an antenna pair with the fourth reception antenna array including the reception antennas Rx4 and Rx8 is also arranged at a position shifted in the positive direction of the y-axis from the pair of reception antenna arrays.

  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. Similarly, the transmission antennas Tx3 and Tx4 are displaced by a distance 2w and 3w in the positive direction of the y-axis with respect to the transmission antenna Tx1, respectively.

As described above, transmission / reception of radio waves is performed in units of antenna pairs. Here, 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. The number of the types is large and high angle measuring resolution as present to large delta _S is obtained. In this regard, by making the z coordinate of the transmission antennas Tx1 to Tx4 common to the arrangement of the reception antennas Rx1 to Rx10 described above, for example, the reception antenna Rxk (k is 2 to 10 with respect to the relative coordinates of the reception antenna Rx1). absolute value of the difference between the relative coordinates of a natural number.) is, (k-1) λ / 2 , and the the delta _S nine patterns obtained.

  FIG. 5 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. Hereafter, the operation | movement concerning the angle measurement process of the radar apparatus 10 is demonstrated, referring FIG.

  Each time the series of processes shown in FIG. 5 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 four antenna pairs, so steps S100 and S110 are executed four times.

  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 Rx10 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. The ranging and angulation processing unit 70 receives the reception antennas Rx1, Rx5, and Rx9 that form the reception antenna array that forms an antenna pair with the transmission antenna Tx1 among the reception results of Rx1 to Rx10 input from the A / D converter 40. Temporarily store the results.

  Similarly, when transmitting from the transmitting antenna Tx2, the receiving results of the receiving antennas Rx2, Rx6, and Rx10 are temporarily stored, and when transmitting from the transmitting antenna Tx3, the receiving results of the receiving antennas Rx3 and Rx7 are temporarily stored. In the case of transmission from the transmission antenna Tx4, the reception results of the reception antennas Rx4 and Rx8 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 Rx10 obtained by four 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 reception result of the reception antenna Rxk (k is a natural number of 1 to 10) 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.

  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 along the angle measurement direction axis ( Step S160). In the present embodiment, the angle measuring surface is an xz plane, and θ is defined as a direction in front of the radar apparatus 10, that is, a positive direction of the x axis as 0 degree.

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 9) represents a difference in radio wave propagation path length between the reference receiving antenna and other receiving antennas. In the example described here, the receiving antenna Rx1 is As a reference, a difference between the propagation path length of the reception antenna Rx (k + 1) with respect to the propagation path length of the reception antenna Rx1 is defined as d _k . As can be understood from this, in this example, the number of reception antennas 22 is the order of the steering vector (the number of components).

  The distance measuring and angle processing unit 70 uses the steering vector V (ω, θ) obtained by the equation (2) 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 R (ω), 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 (3) 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 same number of receiving antennas as the desired order of the steering vector are arranged at equal intervals with respect to the angle measurement direction coordinates. However, the arrangement of the antenna elements in the antenna device 20 is limited to this. I can't. An example of this will be described below.

  FIG. 6 is a schematic front view of a second example of the antenna device 20 according to the embodiment. In the antenna device 20 of the second example, two transmission antennas (Tx1, Tx2) and five reception antennas (Rx1 to Rx5) are arranged.

  The five receiving antennas Rx1 to Rx5 are arranged in a plurality of z-coordinates without overlapping each other by being divided into a plurality of receiving antenna arrays as in the first example. If the z-coordinate of the receiving antenna Rx1 is 0, the z-coordinates of the receiving antennas Rx2 to Rx5 are set to 0, −2λ, −3λ, and −9λ / 2, respectively, and the first receiving antenna column includes the receiving antenna Rx1 and Three receiving antennas Rx3 2λ apart from Rx1 and three receiving antennas Rx5 5λ / 2 away from Rx3 are arranged, and the second receiving antenna row has a receiving antenna Rx2 having the same z-coordinate as the receiving antenna Rx1, and Rx2 And two receiving antennas Rx4 that are 3λ away from each other. The second receiving antenna array is arranged to be shifted from the first receiving antenna array by a distance w in the positive y-axis direction.

  Two transmission antennas Tx1 and Tx2 are provided corresponding to the two reception antenna columns, the transmission antenna Tx1 and the first reception antenna column form one antenna pair, and the transmission antenna Tx2 and the second reception antenna column Forms another antenna pair. Accordingly, the transmission antenna Tx2 is arranged so as to be shifted from the transmission antenna Tx1 by the distance w in the positive direction of the y-axis, corresponding to the difference between the y coordinates of the two reception antenna arrays. Further, the transmission antenna Tx2 is arranged so as to be shifted from the transmission antenna Tx1 by a distance λ / 2 in the positive z-axis direction.

  Here, focusing only on the receiving antenna, the angular direction distance between the receiving antennas Rx3 and Rx4 is twice the half wavelength, the angular direction distance between the receiving antennas Rx4 and Rx5 is three times the half wavelength, the receiving antenna Rx1 and Rx2 and Rx3 angle measurement direction distance is 4 times the half wavelength, reception antenna Rx3 and Rx5 angle measurement direction distance is 5 times the half wavelength, reception antenna Rx1, Rx2 and Rx4 angle measurement direction distance is half wavelength Of the receiving antennas Rx1 and Rx2 and Rx5 are 6 times as long as the angular direction distance is 9 times the half wavelength, and the angular direction distance is 1 time, 7 times, and 8 times the half wavelength. Does not exist.

However, the absolute value delta _S of difference in the relative coordinates of the receiving antenna to each other as described in the first embodiment can be obtained nine in the second embodiment shown in FIG. 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 coordinate of the receiving antenna Rx1 is set as the reference value α, the relative coordinates of the receiving antennas Rx2 to Rx5 are α−λ / 2, α−2λ, α−7λ / 2, and α−9λ / 2. It becomes.

Therefore, the absolute value delta _S of difference in the relative coordinates, 1 times a half wavelength for receive antenna pairs (Rx1, Rx2), a set (Rx4, Rx5) 2 times the half wavelength for the set (Rx2, Rx3), and ( Rx3, Rx4) three times the half wavelength, pair (Rx1, Rx3) four times the half wavelength, pair (Rx3, Rx5) five times the half wavelength, pair (Rx2, Rx4) six times the half wavelength, The set (Rx1, Rx4) is 7 times the half wavelength, the set (Rx2, Rx5) is 8 times the half wavelength, and the set (Rx1, Rx5) is 9 times the half wavelength.

That is, the second example of the antenna device 20 shown in FIG. 6, 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 less half wavelength of the transmitted wave And the number of terms is an example of a configuration that takes the value of each term in an arithmetic sequence having a predetermined number equal to or greater than the total number m of receiving antennas. Specifically, with respect to m = 5, delta _S is the tolerance and the initial term forming the arithmetic progression lambda / 2, the number of terms is nine.
In the case of the arrangement example of the antenna device 20 shown in FIG. 6, it can be seen that the number of antennas to be used is significantly smaller than the arrangement example shown in FIG. 4. That is, in the second antenna arrangement example, power consumption can be reduced.

  The cross-correlation matrix R (ω) relating to the antenna arrangement in FIG.

  When attention is paid to the matrix appearing on the right side of equation (4), nine types from exp (−jωΔt) to exp (−j9ωΔt) that are the same as the components included in equation (1) are included in the components below the diagonal component. Phase components are included. This indicates that angle measurement processing similar to that of the first example of the antenna device 20 described above can be performed, and this antenna device 20 has angle measurement performance similar to that of the first example. 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.

  FIG. 7 is a schematic flowchart of angle measurement processing in the radar apparatus 10 using the second 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. The angle measurement process shown in FIG. 7 is different from the angle measurement process shown in FIG. 5 in that steps S140 and S150 are added, and the other steps are composed of common steps. Therefore, description of the matters described with reference to FIG. 5 is basically omitted here, and the added steps S140 and S150 will be mainly described.

  In step S140, the distance measurement and angle processing unit 70 extracts a matrix component from the lower left half of the cross-correlation matrix R (ω) shown in the equation (4) calculated in step S130, and generates a virtual equation shown in the following equation. Create received data.

  In step S150, a cross-correlation matrix defined by the following equation is calculated using the virtual reception data created in step S140.

  In the processing after step S160, the cross-correlation matrix given by equation (6) is used instead of the cross-correlation matrix R (ω) used in the first example, and the azimuth vector P ( ω, θ) is obtained. At this time, as the steering vector V (ω, θ), a vector having an order corresponding to the virtual received data shown in the equation (5) is used to obtain the weight vector W (ω, θ). Incidentally, as described above, the antenna device 20 of FIG. 6 can obtain the same type of phase component as the antenna device 20 of FIG. 4, and thus the steering vector has the same order as the equation (2).

[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 axis direction are arranged in different transmission antenna arrays and receive signals. An antenna 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 between the transmitting antenna 21 and the receiving antenna 22 forming an antenna pair in the direction of the angle-measurement orthogonal axis is fixed.

  FIG. 8 is a schematic front view of a third example of the antenna device 20 according to the embodiment, and shows an example of an antenna arrangement in which the transmission antenna 21 and the reception antenna 22 are interchanged. Specifically, the example shown in FIG. 8 is an antenna device 20 in which the transmitting antenna and the receiving antenna are interchanged in the antenna arrangement shown in FIG. 4, and there are 10 transmitting antennas 21 (Tx1 to Tx10), and the receiving antennas are Four (Rx1 to Rx4) are arranged.

  The radar apparatus 10 using the antenna apparatus 20 transmits electromagnetic waves in a time division manner from the transmission antennas Tx1 to Tx10, 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.

  The antenna pairs in the antenna device 20 of FIG. 8 are (Tx1, Rx1), (Tx2, Rx2), (Tx3, Rx3), (Tx4, Rx4), (Tx5, Rx1), (Tx6, Rx2), (Tx7, Rx3). ), (Tx8, Rx4), (Tx9, Rx1), and (Tx10, Rx2), and the interval between the transmission antennas is covered without omission from 1 to 9 times the half wavelength.

In addition, the radar apparatus 10 provided with the antenna apparatus 20 of FIG. 8 except that the result of FFT of the received data when transmitting from Txk (k is a natural number of 1 to 10) is treated as X _k (ω). Ranging can be performed by basically the same processing as that of the radar device 10 including the antenna device 20 of FIG.

  Further, the antenna arrangement 20 shown in FIG. 6 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 embodiment, 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.

  As described above, the antenna device according to the present invention and the radar device using the antenna device can ensure angle measurement accuracy and angle measurement distance even when a person whose reflection cross section changes is detected.

  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 (5)

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,
Any two of the receiving antennas whose difference in the angle measuring direction coordinate is less than the length of the angle measuring direction of the receiving antenna are arranged in the receiving antenna row different from each other,
The transmitting antenna is provided for each receiving antenna array, and forms an antenna pair with the receiving antenna array;
An antenna device characterized by the above.   The antenna apparatus according to claim 1, wherein the reception antenna is an array antenna in which a plurality of patch elements are connected in a straight line shape in the angle measurement direction.   Assuming that the difference in the angular direction coordinate of the receiving antenna with respect to the transmitting antenna in the antenna pair is a relative coordinate, the absolute value of the difference in the relative coordinate between the receiving antennas in all combinations of the two receiving antennas The value of each term of the differential number sequence, wherein the tolerance is equal to or less than a half wavelength of the transmission wave and the number of terms is a predetermined number equal to or greater than the total number of the receiving antennas, is defined in claim 1 or 2. The antenna device described. 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,
Any two of the transmission antennas whose difference between the angle measurement direction coordinates is less than the length of the transmission antenna in the angle measurement direction are arranged in the transmission antenna rows different from each other,
The receiving antenna is provided for each transmitting antenna array, and forms an antenna pair with each transmitting antenna of the transmitting antenna array;
An antenna device characterized by the above. A radar device comprising the antenna device according to any one of claims 1 to 4 and detecting a target object,
A transmission / reception processing means for selecting a plurality of the antenna pairs in a time division manner, transmitting a 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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