Radar sensor

Abstract

Provided is a radar sensor capable of determining the degree of deformation and shape variation of an object with high accuracy.　This radar sensor includes: a transmission antenna which is capable of transmitting radio waves toward an object; a reception antenna which is capable of receiving radio waves reflected by the object; a first reflector which is capable of reflecting radio waves reflected by the object toward the object; and a detection unit which detects the distance to the object on the basis of multi-reflected waves, which are radio waves transmitted from the transmission antenna, reflected by the object, then reflected by the first reflector at least once, and then received by the reception antenna.

Description

Radar sensor

[0001] This disclosure relates to a radar sensor.

[0002] Conventionally, there has been a radar cross-section measurement device that includes a reflector in the radiation direction of a transceiver antenna, reflects radio waves radiated from the transceiver antenna, and radiates them to a measurement object, so that the distance from the transceiver antenna to the measurement object is about twice the distance between the measurement object and the reflector (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2006-214938

[0004] By the way, conventional radar cross-section measurement devices cannot accurately discriminate the degree of deformation and shape variation of multiple objects.

[0005] Therefore, an object is to provide a radar sensor capable of accurately discriminating the degree of deformation and shape variation of an object.

[0006] The radar sensor according to an embodiment of this disclosure includes a transmission antenna capable of transmitting radio waves toward an object, a reception antenna capable of receiving radio waves reflected by the object, a first reflector capable of reflecting the radio waves reflected by the object toward the object, and a detection unit that detects the distance to the object based on a multiple reflection wave, which is radio waves transmitted from the transmission antenna, reflected by the object, and then reflected at least once by the first reflector and received by the reception antenna.

[0007] A radar sensor capable of accurately discriminating the degree of deformation and shape variation of an object can be provided.

[0008] This figure shows an example of the configuration of the radar sensor 100 of the embodiment. This figure shows an example of the configuration of the radar sensor 100 of the embodiment when disassembled. This figure shows an example of the configuration of the cross section viewed along the line A-A in Figure 1A. This figure shows an example of the distribution of the radio wave intensity of the reflected wave obtained by the radar sensor 100. This figure illustrates an example of distance detection by the radar sensor 100. This figure shows an example of the distance detection result by the radar sensor 100. This figure shows an example of the distance detection result by the radar sensor 100. This figure shows an example of the distance detection result by the radar sensor 100. This figure shows an example of the distance detection result by the radar sensor 100. This figure shows an example of the distance detection result by the radar sensor 100. This figure shows an example of the distance detection result by the radar sensor 100. This figure shows an example of the distance detection result by the radar sensor 100. This figure shows an example of the distance detection result by the radar sensor 100. This figure summarizes an example of the measurement results of distances D1 and D2. This figure shows an example of the configuration of the radar sensor 100M1 of the first modified example of the embodiment. This figure shows an example of the configuration of the radar sensor 100M1 of the first modified example of the embodiment. This figure illustrates an example of distance detection using radar sensor 100M1. This figure illustrates an example of the configuration of radar sensor 100M2 in a second modified embodiment. This figure illustrates an example of distance detection using radar sensor 100M2.

[0009] The following describes embodiments applying the radar sensor of this disclosure.

[0010] In the following, we define and explain the XYZ coordinate system. For the sake of explanation, the -Z direction will be referred to as the lower side or bottom, and the +Z direction as the upper side or top, but this does not represent a universal up-down relationship. Viewing from the XZ plane will be referred to as a plan view. Viewing an opening from the XZ plane will be referred to as an opening plane view.

[0011] <Embodiment> <Configuration of Radar Sensor 100> Figure 1A shows an example of the configuration of the radar sensor 100 of the embodiment. Figure 1B shows an example of the configuration of the radar sensor 100 of the embodiment when disassembled. Figure 1C shows an example of the configuration of the cross-section taken along the line A-A in Figure 1A.

[0012] The radar sensor 100 includes a base 101, a circuit board 110, a transmitting / receiving unit 120, an electromagnetic horn 130, a radio wave lens 140, and a retroreflector 150. The electromagnetic horn 130 is an example of a waveguide. The retroreflector 150 is an example of a first reflector.

[0013] The cross-section shown in Figure 1C is a cross-sectional plane obtained by cutting the electromagnetic horn 130 in the YZ plane containing the central axis C of the electromagnetic horn 130 (see Figure 1B). The central axis C of the electromagnetic horn 130 coincides with the optical axis of the radio wave lens 140.

[0014] The radar sensor 100 is a device that measures the distance to an object to be measured (an example of an object) by transmitting and receiving radio waves. The radio wave lens 140 narrows the radiation pattern of the transmitted wave and focuses the received radio waves with the radio wave lens 140.

[0015] Such a radar sensor 100 can be used, for example, as a radar device that receives reflected waves that are returned after a transmitted wave is reflected by an object to be measured, and measures the distance to the object. The distance to the object can be measured based on the round-trip time from when the radio waves are transmitted as a transmitted wave until when the reflected radio waves are received.

[0016] The radio waves transmitted and received by the radar sensor 100 are, for example, millimeter-wave radio waves. Millimeter waves are radio waves in the frequency band of 30 GHz to 300 GHz and behave almost identically to light. However, the radio waves transmitted and received by the radar sensor 100 may also be radio waves with frequencies belonging to bands other than the millimeter-wave band.

[0017] <Configuration of the base 101> The base 101 is a component that holds the substrate 110 on which the transmitting / receiving unit 120 is provided and the retroreflector 150. Since accurate positioning of the transmitting / receiving unit 120 and the retroreflector 150 is important in the operation of the radar sensor 100, the base 101 only needs to be a component that can stably hold the substrate 110 on which the transmitting / receiving unit 120 is provided and the retroreflector 150, and does not affect the transmission and reception of radio waves by the radar sensor 100.

[0018] The base 101 can be made of a dielectric material, and for example, it is made of resin. The base 101 is a rectangular parallelepiped member and has an upper surface 101A, a lower surface 101B, and a holding portion 101C. A substrate 110 on which the transmitting and receiving unit 120 is provided is fixed to the upper surface 101A.

[0019] The holding portion 101C is provided on approximately half of the base 101 on the +X side, and is notched to penetrate the upper surface 101A and the lower surface 101B so that it can hold the inverted triangular pyramidal outer surface of the retroreflector 150. The inner surface of the holding portion 101C has a shape that abuts the intermediate portion of the inverted triangular pyramidal outer surface of the retroreflector 150, excluding the +Y end and the -Y end. The holding portion 101C is also in communication with the side surface of the base 101 on the +X side. The holding portion 101C can have any shape as long as it can stably hold the retroreflector 150 so that it does not shift position.

[0020] <Configuration of the circuit board 110> The circuit board 110 is a circuit board on which the transmitting and receiving unit 120 is mounted, and as an example, a wiring board conforming to the FR-4 (Flame Retardant type 4) standard can be used. The circuit board 110 is fixed to the -Y direction side of the electromagnetic horn 130.

[0021] <Configuration of the Transceiver Unit 120> The transceiver unit 120 is mounted on the surface of the substrate 110 on the +Y direction side. The transceiver unit 120 is an example of an integrated circuit chip and is composed of one IC chip. The transceiver unit 120 has a transmitting antenna 121Tx, a receiving antenna 121Rx, and a detection unit 122. The detection unit 122 is included in the transceiver unit 120 as an example of an integrated circuit chip.

[0022] The transmitting antenna 121Tx and the receiving antenna 121Rx are mounted on the surface of the transmitting / receiving unit 120 on the +Y direction side. The detection unit 122 incorporates the transmitting / receiving circuits connected to the transmitting antenna 121Tx and the receiving antenna 121Rx and performs distance detection. Distance detection is the process of detecting distance, and is synonymous with measuring distance.

[0023] The transmitting / receiving unit 120 is smaller than the substrate 110 in plan view, and is, for example, square in shape. The transmitting / receiving unit 120 is positioned in the center of the opening 131 in plan view (opening surface view), and more specifically, the center of the transmitting / receiving unit 120 in plan view is positioned on the central axis C. Furthermore, the position in the Y direction of the surface of the transmitting / receiving unit 120 on the +Y direction side coincides with the position in the Y direction of the opening 131, for example.

[0024] The transmitting antenna 121Tx and the receiving antenna 121Rx are provided on the surface of the transmitting / receiving unit 120 on the +Y direction side, spaced apart in the Z direction. For example, the transmitting antenna 121Tx and the receiving antenna 121Rx are antennas of the same shape and size. The transmitting antenna 121Tx transmits radio waves via the electromagnetic horn 130, and the receiving antenna 121Rx receives radio waves via the electromagnetic horn 130.

[0025] The transmitting antenna 121Tx and the receiving antenna 121Rx are arranged so as to be point-symmetric with respect to the central axis C in a plan view. Viewing the transmitting antenna 121Tx and the receiving antenna 121Rx in a plan view is equivalent to viewing the transmitting antenna 121Tx and the receiving antenna 121Rx in a plan view of the opening surface (plan view) of the opening 131.

[0026] The transmitting antenna 121Tx and the receiving antenna 121Rx are said to be point-symmetric with respect to the central axis C in a plan view if the centers of the transmitting antenna 121Tx and the receiving antenna 121Rx in a plan view are arranged point-symmetrically with respect to the central axis C in a plan view. Since the central axis C coincides with the optical axis of the radio wave lens 140, the transmitting antenna 121Tx and the receiving antenna 121Rx are positioned offset from the optical axis of the radio wave lens 140.

[0027] Since it is not possible to place both the transmitting antenna 121Tx and the receiving antenna 121Rx on the central axis C (the optical axis of the radio lens 140), they are arranged in this manner to match the transmission and reception characteristics of the transmitting antenna 121Tx and the receiving antenna 121Rx. The transmitting antenna 121Tx and the receiving antenna 121Rx can be implemented using, for example, a loop antenna, patch antenna, monopole antenna, or dipole antenna.

[0028] Furthermore, the Y-direction position of the surface of the transmitting / receiving unit 120 on the +Y-direction side coincides with the Y-direction position of the opening 131.

[0029] The intensity of the radio waves (transmitted waves) radiated from the transmitting antenna 121Tx is strongest in the direction connecting the center of the transmitting antenna 121Tx and the center of the radio wave lens 140. Similarly, the intensity of the radio waves (received waves) received by the receiving antenna 121Rx is strongest in the direction connecting the center of the receiving antenna 121Rx and the center of the radio wave lens 140. The center of the radio wave lens 140 is located at the center of the thickness of the radio wave lens 140 in the Y direction, on the optical axis of the radio wave lens 140 (the central axis C of the electromagnetic horn 130).

[0030] The detection unit 122 incorporates a transmitting and receiving circuit connected to the transmitting antenna 121Tx and the receiving antenna 121Rx, as well as an electronic circuit. The electronic circuit is implemented by a computer, for example, including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), input / output interface, and internal bus. The detection unit 122 detects the distance from the transmitting and receiving unit 120 to the object to be measured based on the time from when the transmitting antenna 121Tx emits radio waves until the reflected waves are received by the receiving antenna 121Rx, by executing instruction codes stored in memory. The detection unit 122 performs a peak search on the reflected waves acquired by the transmitting and receiving circuit and determines the timing when the signal level of the reflected waves reaches a peak (maximum) as the timing when the receiving antenna 121Rx receives the reflected waves, thereby calculating the time from when the transmitting antenna 121Tx emits radio waves until the reflected waves are received by the receiving antenna 121Rx.

[0031] The detection unit 122 detects the distance to the object to be measured based on a multiple-reflected wave, which is a radio wave transmitted from the transmitting antenna 121Tx, reflected by the object to be measured, reflected at least once by the retroreflector 150, reflected again by the object to be measured, and then received by the receiving antenna 121Rx, in order to accurately determine the degree of deformation and shape variation of the object to be measured.

[0032] Here, multiple reflected waves are radio waves that have been reflected three or more times between the transmitting / receiving unit 120 and the object being measured, and between the retroreflector 150 and the object being measured, and are received by the receiving antenna 121Rx. In other words, multiple reflected waves here are radio waves that have traveled at least two round trips between the transmitting / receiving unit 120 and the object being measured, and between the retroreflector 150 and the object being measured, and are received by the receiving antenna 121Rx. Details of the distance detection to the object being measured by the detection unit 122 will be described later.

[0033] <Configuration of the electromagnetic horn 130> The electromagnetic horn 130 is, for example, a cylindrical waveguide. The electromagnetic horn 130 is made of metal (conductor). The electromagnetic horn 130 has an opening 131, an opening 132, and an inner wall surface 133. The inside of the electromagnetic horn 130 is a waveguide through which radio waves propagate. The centers of the openings 131 and 132 coincide when viewed from the opening surface. The +Y direction is an example of the radiation direction of the transmitting antenna 121Tx of the transmitting / receiving unit 120.

[0034] The opening 131 is located at the -Y direction end of the electromagnetic horn 130, and the opening 132 is located at the +Y direction end of the electromagnetic horn 130. The section in which the electromagnetic horn 130 functions as a device through which radio waves propagate is the section between the opening 131 and the opening 132. The sizes of the openings 131 and 132 are equal when viewed from the opening plane. The centers of the openings 131 and 132 in the opening plane view are located on the central axis C. Note that the same function can be achieved even if the electromagnetic horn has a shape in which the opening 132 is larger than the opening 131.

[0035] A transmitting and receiving unit 120 mounted on the substrate 110 is provided on the side of the opening 131. The opening 131 surrounds the transmitting antenna 121Tx and the receiving antenna 121Rx when viewed from the opening surface. Here, as an example, the opening 131 surrounds the transmitting and receiving unit 120 having the transmitting antenna 121Tx and the receiving antenna 121Rx when viewed from the opening surface.

[0036] The inner wall surface 133 connects the openings 131 and 132. The inner wall surface 133 is circular when viewed from the opening surface, and the opening area is constant from the opening 131 side to the opening 132 side. The electromagnetic horn 130 is a cylindrical member, and the inner wall surface 133 has a shape corresponding to the inner circumferential surface of the cylindrical member.

[0037] A radio wave lens 140 is attached to the end of the inner wall surface 133 on the +Y direction side. When the radio wave lens 140 is attached to the inner wall surface 133, the device is configured so that there is no gap between the outer edge of the radio wave lens 140 and the inner wall surface 133 when viewed from the aperture. This is to prevent radio waves from passing through the gap between the inner wall surface 133 and the outer edge of the radio wave lens 140.

[0038] <Configuration of the radio wave lens 140> The radio wave lens 140 is fixed to the +Y direction end of the inner wall surface 133 of the electromagnetic horn 130. The radio wave lens 140 can be fixed to the inner wall surface 133 with adhesive, double-sided tape, or a jig. The radio wave lens 140 is made of glass or resin, for example. The radio wave lens 140 is a lens that can focus radio waves transmitted and received by the transmitting antenna 121Tx and the receiving antenna 121Rx in both directions, and for example it is a biconvex lens that is circular in plan view. However, the radio wave lens 140 may be a uniconvex lens. Biconvex lenses and uniconvex lenses are examples of convex lenses.

[0039] When the radio wave lens 140 is attached to the inner wall surface 133, in a view from the opening surface, a gap is not formed between the outer peripheral portion (outer edge portion) of the radio wave lens 140 and the inner wall surface 133. This is to ensure that all the transmitted waves radiated from the transmission antenna 121Tx enter the radio wave lens 140 and no transmitted wave propagates to the opening 132 side without entering the radio wave lens 140. Also, this is to ensure that all the reflected waves reflected to the -Y direction side at the opening 132 enter the radio wave lens 140 and do not propagate to the opening 131 side without entering the radio wave lens 140.

[0040] When the radar sensor 100 measures the distance to the measurement object, the reference point (hereinafter, reference point 140A) is the center of the surface on the +Y direction side of the radio wave lens 140 and is the point located most on the +Y direction side of the radio wave lens 140.

[0041] As an example, the detection unit 122 calculates the distance from the transmission / reception unit 120 to the measurement object and subtracts the distance from the transmission / reception unit 120 to the reference point 140A to detect the distance from the reference point 140A to the measurement object.

[0042] <Retroreflector 150> The retroreflector 150 is a reflector that performs retroreflection to reflect radio waves arriving from various directions on the +Y direction side in the arrival direction. As an example, the retroreflector 150 is fitted and fixed to the holding portion 101C of the pedestal 101 and is located on the +X direction side of the transmission / reception unit 120.

[0043] As an example, the retroreflector 150 has three reflecting surfaces 151 recessed in an inverted triangular pyramid shape. Each of the three reflecting surfaces 151 is a right-angled isosceles triangle. The three reflecting surfaces 151 are arranged such that the right-angled vertices of the right-angled isosceles triangles of the three reflecting surfaces 151 are adjacent to each other at the apex of the triangular pyramid, and the three reflecting surfaces 151 are orthogonal to each other.

[0044] As an example, the thickness of the three walls of the retroreflector 150, each having three reflective surfaces 151, is constant, and the outer surface has an inverted triangular pyramidal shape. Such a retroreflector 150 may be made of a metal such as aluminum, for example. However, the retroreflector 150 is not limited to this configuration; any reflector that performs retroreflection, reflecting radio waves arriving from various directions on the +Y side back in the direction of arrival, is acceptable. Furthermore, when the three reflective surfaces 151 of the retroreflector 150 are inverted triangular pyramidal, the shape of the outer surface of the retroreflector 150 is not limited to an inverted triangular pyramidal shape, but can be any shape.

[0045] <Reason for detecting distance based on multiple reflected waves> Figure 2 shows an example of the distribution of radio wave intensity of reflected waves obtained by the radar sensor 100. In Figure 2, the horizontal axis represents the distance (mm) in the +Y direction from the reference point 140A of the radar sensor 100. The distance on the horizontal axis is obtained by converting the time from when the radio waves are emitted by the transmitting antenna 121Tx until the radio waves are received by the receiving antenna 121Rx into distance, and subtracting the distance between the transmitting / receiving unit 120 and the reference point 140A. To convert time into distance, time is multiplied by the speed of light. The speed of light is 3 × 10⁻⁶ ８ (m / s). The vertical axis in Figures 2A and 2B shows the intensity of the radio waves received by the receiving antenna 121Rx. The radio wave intensity is shown as a normalized value (unitless).

[0046] Figure 2 shows the distribution of radio wave intensity of reflected waves that are not multiple reflected waves, but rather waves that are emitted from the transmitting antenna 121Tx, reflected once by the object being measured, and received by the receiving antenna 121Rx. In other words, the reflected waves whose radio wave intensity is shown in Figure 2 are reflected waves that have traveled once round trip between the radar sensor 100 and the object being measured.

[0047] For example, in the case of a plurality of measurement objects of the same type, there may be a need to determine whether the degree of dimensional variation due to deformation or shape variation of each measurement object is within the acceptable range as a product or outside the acceptable range. In such a case, each measurement object is sequentially placed in front of the radar sensor 100 to detect the distance from the radar sensor 100, and it is determined whether the difference between the detected distance and the reference value is within the acceptable range, thereby determining whether each measurement object passes or fails as a product.

[0048] In such a case, as an example, it is assumed that the detection error of the distance by the radar sensor 100 is ±5 mm, and the acceptable range for the measurement object is the reference value ±5 mm. Also, as an example, it is assumed that the actual distance from the radar sensor 100 to the measurement object is 240 mm.

[0049] In this case, based on the reflected wave that travels back and forth once between the radar sensor 100 and the measurement object, if the distance from the radar sensor 100 to the measurement object is detected and the detected distance is 245 mm, it is impossible to determine whether the distance is deviated by 5 mm due to the detection error or the distance is deviated by 5 mm due to the deformation or shape variation of the measurement object.

[0050] In such a case, when detecting twice the distance from the radar sensor 100 to the measurement object based on the reflected wave that travels back and forth twice between the radar sensor 100 and the measurement object, although the detection error included in twice the distance is 5 mm, the distance deviation due to the deformation or shape variation of the measurement object included in twice the distance becomes 10 mm.

[0051] As described above, even in a case where it is difficult to distinguish between the distance detection error by the radar sensor 100 and the deformation or shape variation of the measurement object, the radar sensor 100 uses multiple reflected waves to perform distance detection in order to be able to determine whether the deformation or shape variation of the measurement object is within the acceptable range.

[0052] <Example of Distance Detection> Fig. 3 is a diagram for explaining an example of distance detection by the radar sensor 100. Fig. 3 schematically shows a measurement object 1, a transmission antenna 121Tx, a reception antenna 121Rx, a radio wave lens 140, and a retroreflector 150.

[0053] In the radar sensor 100, as an example, as shown by the solid arrow, radio waves emitted from the transmitting antenna 121Tx are reflected by the object to be measured 1, reflected by the retroreflector 150, and then reflected again by the object to be measured 1 as shown by the dashed arrow, and the distance D from the reference point 140A to the object to be measured 1 is detected based on the multiple reflected waves that reach the receiving antenna 121Rx.

[0054] In other words, as shown in Figure 3, the radar sensor 100 makes two round trips between the transmitting / receiving unit 120 (transmitting antenna 121Tx, receiving antenna 121Rx) and the retroreflector 150 and the object to be measured 1, and detects the distance D from the reference point 140A to the object to be measured 1 based on the multiple reflected waves received by the receiving antenna 121Rx. The distance D is synonymous with the distance from the radar sensor 100 to the object to be measured 1.

[0055] <Measurement Results> Figures 4A to 4D and 5A to 5D show examples of distance detection results by the radar sensor 100. In Figures 4A to 4D and 5A to 5D, the horizontal axis represents the distance (mm) in the +Y direction from the reference point 140A of the radar sensor 100. The distance on the horizontal axis is obtained by converting the time from when the transmitting antenna 121Tx emits radio waves until the receiving antenna 121Rx receives the radio waves into distance, and subtracting the distance between the transmitting / receiving unit 120 and the reference point 140A. To convert time into distance, time is multiplied by the speed of light. The speed of light is 3 × 10⁻⁶ ８ (m / s). The vertical axis in Figures 4A to 4D and 5A to 5D shows the intensity of the radio waves received by the receiving antenna 121Rx. The radio wave intensity is shown as a normalized value (unitless).

[0056] Figures 4A and 4B show examples of waveforms of the reflected radio wave intensity received by the receiving antenna 121Rx after one round trip between the transmitting / receiving unit 120 (transmitting antenna 121Tx, receiving antenna 121Rx) and the object to be measured 1. Figure 4A shows an example of the reflected radio wave intensity waveform when the distance from the radar sensor 100 to the object to be measured 1 is 240 mm, and Figure 4B shows an example of the reflected radio wave intensity waveform when the distance from the radar sensor 100 to the object to be measured 1 is 245 mm.

[0057] From the waveform shown in Figure 4A, the distance D detected by the detection unit 122 was 240 mm. Also, from the waveform shown in Figure 4B, the distance D detected by the detection unit 122 was 245 mm. However, in the waveforms shown in Figures 4A and 4B, peaks are also present near the distance D to be detected, which may prevent the detection of the actual distance D correctly.

[0058] Figures 4C and 4D show an example of the waveform of the reflected wave intensity received by the receiving antenna 121Rx after two round trips between the transmitting / receiving unit 120 (transmitting antenna 121Tx, receiving antenna 121Rx) and the object to be measured 1. When two round trips are made, the radio waves radiated from the transmitting antenna 121Tx are reflected by the object to be measured 1, reflected by the retroreflector 150, reflected again by the object to be measured 1, and received as a multiple reflected wave by the receiving antenna 121Rx.

[0059] Since the approximate distance between the radar sensor 100 and the object to be measured 1 is known, it is possible to distinguish whether the waveform is one round trip or two round trips based on the time from when it is emitted from the transmitting antenna 121Tx until it is received by the receiving antenna 121Rx.

[0060] Figure 4C shows an example of the waveform of the radio wave intensity of multiple reflected waves after two round trips when the distance from the radar sensor 100 to the object 1 is 240 mm, and Figure 4D shows an example of the waveform of the radio wave intensity of multiple reflected waves after two round trips when the distance from the radar sensor 100 to the object 1 is 245 mm.

[0061] From the waveform shown in Figure 4C, the distance D detected by the detection unit 122 was 479 mm. From this, the distance to the object can be determined to be half of the detected value, 239.5 mm (≒240 mm). Also, from the waveform shown in Figure 4D, the distance D detected by the detection unit 122 was 489 mm. From this, the distance to the object can be determined to be half of the detected value, 244.5 mm (≒245 mm). Therefore, a displacement or movement of 5 mm of the object can be detected.

[0062] Figures 5A and 5B show examples of waveforms of the reflected radio wave intensity received by the receiving antenna 121Rx after one round trip between the transmitting / receiving unit 120 (transmitting antenna 121Tx, receiving antenna 121Rx) and the object to be measured 1. Figure 5A shows an example of the reflected radio wave intensity waveform when the distance from the radar sensor 100 to the object to be measured 1 is 260 mm, and Figure 5B shows an example of the reflected radio wave intensity waveform when the distance from the radar sensor 100 to the object to be measured 1 is 265 mm.

[0063] From the waveform shown in Figure 5A, the distance D detected by the detection unit 122 was 260 mm. Also, from the waveform shown in Figure 5B, the distance D detected by the detection unit 122 was 265 mm.

[0064] Figures 5C and 5D show an example of the waveform of the reflected radio wave intensity received by the receiving antenna 121Rx after two round trips between the transmitting / receiving unit 120 (transmitting antenna 121Tx, receiving antenna 121Rx) and the object to be measured 1.

[0065] Figure 5C shows an example of the waveform of the radio wave intensity of multiple reflected waves after two round trips when the distance from the radar sensor 100 to the object 1 is 260 mm, and Figure 5D shows an example of the waveform of the radio wave intensity of multiple reflected waves after two round trips when the distance from the radar sensor 100 to the object 1 is 265 mm.

[0066] From the waveform shown in Figure 5C, the distance D detected by the detection unit 122 was 521 mm. Also, from the waveform shown in Figure 5D, the distance D detected by the detection unit 122 was 530 mm.

[0067] <Measurement Results of Distances D1 and D2> Figure 6 is a diagram summarizing an example of the measurement results of distances D1 and D2. Distance D1 is the distance D detected by the detection unit 122 based on the reflected wave of one round trip, and distance D2 is the distance D detected by the detection unit 122 based on the multiple reflected waves of two round trips.

[0068] Figure 6 shows the distances D1 and D2, and the amount of change in distances D1 and D2, when the distance from the reference point 140A of the radar sensor 100 to the object to be measured 1 is changed from 240 mm to 305 mm in 5 mm increments.

[0069] As shown in Figure 6, the distance to object 1 and distance D1 all coincide from 240 mm to 305 mm. Furthermore, the error of distance D2 relative to the distance to object 1 is ±1 mm or 0 mm. The change in distance D1 was 5 mm increments, and the change in distance D2 was 9 mm, 10 mm, or 11 mm increments.

[0070] Thus, in distance detection based on one round-trip reflected wave, the change in distance D1 is 5 mm, but in distance detection based on multiple round-trip reflected waves, the change in distance D2 is 9 mm, 10 mm, or 11 mm.

[0071] Therefore, for example, even in cases where it is difficult to distinguish between the distance detection error by the radar sensor 100 and the deformation or shape variation of the object being measured, such as when the distance to the object being measured is approximately 240 mm to 305 mm, it becomes possible to determine whether the deformation or shape variation of the object being measured is within an acceptable range.

[0072] In other words, if the change in distance D2 is 10 mm or less (9 mm or 10 mm), the object being measured is considered acceptable as a product. However, if the change in distance D2 exceeds 10 mm, such as 11 mm, the object being measured is considered unacceptable as a product.

[0073] When distance detection is performed based on multiple reflected waves that make two round trips, if the difference between the detected distance and the reference value is within twice the acceptable range, the product is considered acceptable; if it exceeds twice the acceptable range, the product is considered unacceptable. Users of the radar sensor 100 can easily determine whether the object to be measured 1 is within the acceptable range.

[0074] Alternatively, the average value of distance D1 and half of distance D2 (D2 / 2) may be calculated, and based on this average value, it may be determined whether the deformation and shape variation of the object being measured are within the acceptable range.

[0075] Alternatively, the system may be configured to determine whether a product is acceptable or unacceptable using the detection results of the radar sensor 100, and to display the determination result on a display device (not shown), etc.

[0076] <First Modification> Figures 7A and 7B show an example of the configuration of the radar sensor 100M1 in the first modification of the embodiment.

[0077] The radar sensor 100M1 has a configuration in which a retroreflector 150M1 is provided in the center of the upper surface 101A of the base 101, and the end of the electromagnetic horn 130 on the +Y direction side and the radio wave lens 140 are arranged in the center of the bottom of the retroreflector 150M1 on the -Y direction side.

[0078] The retroreflector 150M1 has a configuration in which the right-angled isosceles triangular reflective surface 151 of the retroreflector 150 shown in Figures 1A to 1C is replaced with a trapezoidal reflective surface 151, and an equilateral triangular base surface 152 is provided on the -Y direction side. There is an opening in the center of the base surface 152, which is aligned with the opening (not shown) of the base 101.

[0079] The electromagnetic horn 130 passes through the central opening of the bottom surface 152 and the opening of the base 101. As shown in Figure 7B, approximately half of the electromagnetic horn 130 on the -Y direction side is located on the -Y direction side of the base 101.

[0080] Furthermore, the substrate 110 is fixed to the -Y direction end of the electromagnetic horn 130, and the transmitting / receiving unit 120, which is not shown in Figures 7A and 7B, is mounted on the +Y direction surface of the substrate 110. In a plan view, the transmitting / receiving unit 120 is located on the -Y direction side of the radio wave lens 140.

[0081] Figure 7C illustrates an example of distance detection using the radar sensor 100M1. Figure 7C shows a simplified representation of the object to be measured 1, the transmitting antenna 121Tx, the receiving antenna 121Rx, the radio lens 140, and the retroreflector 150M1.

[0082] In the radar sensor 100M1, as an example, as shown by the solid arrow, radio waves emitted from the transmitting antenna 121Tx are reflected by the object to be measured 1, reflected by the retroreflector 150M1, and then reflected again by the object to be measured 1 as shown by the dashed arrow, and the distance D from the reference point 140A to the object to be measured 1 is detected based on the multiple reflected waves that reach the receiving antenna 121Rx.

[0083] In other words, as shown in Figure 7C, the radar sensor 100M1 makes two round trips between the transmitting / receiving unit 120 (transmitting antenna 121Tx, receiving antenna 121Rx) and the retroreflector 150M1 and the object to be measured 1, and detects the distance D from the reference point 140A to the object to be measured 1 based on the multiple reflected waves received by the receiving antenna 121Rx. The distance D is synonymous with the distance from the radar sensor 100M1 to the object to be measured 1.

[0084] <Second Modification> Figure 8A shows an example of the configuration of the radar sensor 100M2 in the second modification of the embodiment.

[0085] The radar sensor 100M2 has a configuration in which a specular reflector 160 is provided between the electromagnetic horn 130 and the retroreflector 150 of the radar sensor 100 shown in Figures 1A to 1C. The specular reflector 160 is an example of a second reflector. The specular reflector 160 is fixed to the upper surface of the base 101 and, as an example, is rectangular in plan view.

[0086] The specular reflector 160 is a reflector that reflects the incident wave in the direction of specular reflection. As an example, a metal plate such as aluminum can be used as the specular reflector 160.

[0087] In the radar sensor 100M2, the specular reflector 160 is positioned between the electromagnetic horn 130 and the retroreflector 150 in the X direction, and the number of round trips of radio waves can be increased by increasing the number of reflections between the transmitting / receiving unit 120 and the object to be measured 1.

[0088] Figure 8B illustrates an example of distance detection using the radar sensor 100M2. Figure 8B shows a simplified representation of the object to be measured 1, the transmitting antenna 121Tx, the receiving antenna 121Rx, the radio lens 140, the retroreflector 150, and the specular reflector 160.

[0089] In the radar sensor 100M2, as an example, as shown by the solid arrow, radio waves emitted from the transmitting antenna 121Tx are reflected by the object to be measured 1, reflected back towards the object to be measured 1 by the specular reflector 160, and reflected back towards the retroreflector 150 by the object to be measured 1. The path of the radio waves shown by the solid arrow is the first path from the transmitting antenna 121Tx, reflected by the object to be measured 1, to the retroreflector 150. The specular reflector 160 is inserted between the object to be measured 1 and the retroreflector 150 in the first path, and reflects the radio waves reflected by the object to be measured 1 back towards the object to be measured 1.

[0090] Then, after being reflected by the retroreflector 150, as shown by the dashed arrow, the radio waves are reflected by the object to be measured 1, reflected by the object to be measured 1 towards the specular reflector 160, reflected by the specular reflector 160 towards the object to be measured 1, reflected by the object to be measured 1, and received by the receiving antenna 121Rx. The path of the radio waves shown by this dashed arrow is the second path through which the radio waves are reflected from the retroreflector 150 to the object to be measured 1 and then towards the receiving antenna 121Rx. The specular reflector 160 is inserted between the object to be measured 1 and the receiving antenna 121Rx in the second path and reflects the radio waves reflected by the object to be measured 1 back towards the object to be measured 1.

[0091] The detection unit 122 detects the distance D from the reference point 140A to the object to be measured 1 based on the multiple reflected waves that reach the receiving antenna 121Rx.

[0092] In other words, as shown in Figure 8B, the radar sensor 100M2 makes four round trips between the transmitting / receiving unit 120 (transmitting antenna 121Tx, receiving antenna 121Rx), retroreflector 150, and specular reflector 160 and the object to be measured 1, and detects the distance D from the reference point 140A to the object to be measured 1 based on the multiple reflected waves received by the receiving antenna 121Rx. The distance D is synonymous with the distance from the radar sensor 100M2 to the object to be measured 1.

[0093] When distance detection is performed based on multiple reflected waves that make four round trips, peak search should be performed in a distance range that is approximately four times the distance from the radar sensor 100 to the object to be measured 1 (for example, if the distance D is 240 mm, the range should be 960 mm ± 100 mm).

[0094] When distance detection is performed based on multiple reflected waves that make four round trips, if the difference between the detected distance and the reference value is within four times the acceptable range, the product is considered acceptable; if it exceeds four times the acceptable range, the product is considered unacceptable. Users of the radar sensor 100 can easily determine whether the object to be measured 1 is within the acceptable range.

[0095] <Effects> The radar sensor 100 of this disclosure includes a transmitting antenna 121Tx capable of transmitting radio waves toward the object to be measured 1, a receiving antenna 121Rx capable of receiving radio waves reflected by the object to be measured 1, a retroreflector 150 capable of reflecting the radio waves reflected by the object to be measured 1 toward the object to be measured 1, and a detection unit 122 that detects the distance to the object to be measured 1 based on a multiple reflected wave, which is a radio wave transmitted from the transmitting antenna 121Tx, reflected by the object to be measured 1, reflected at least once by the retroreflector 150, and then received by the receiving antenna 121Rx. As a result, the degree of deformation and shape variation of the object to be measured 1 included in the multiple reflected wave can be increased by an amount corresponding to the number of round trips, making it possible to determine whether or not it is deformation or shape variation.

[0096] Therefore, it is possible to provide a radar sensor 100 that can accurately determine the degree of deformation and shape variation of the object to be measured 1.

[0097] Furthermore, the detection unit 122 may also detect the distance to the object to be measured 1 based on the reflected wave, which is a radio wave transmitted from the transmitting antenna 121Tx, reflected by the object to be measured 1, and then received by the receiving antenna 121Rx without being reflected by the retroreflector 150. Even without using multiple reflected waves, if it is possible to determine from the reflected wave that the deformation or shape variation of the object to be measured 1 is present, the distance can be detected based on the reflected wave.

[0098] Furthermore, the first reflector may be a retroreflector 150. By using a retroreflector 150, multiple reflected waves are more likely to return to the receiving antenna 121Rx, making it easier to obtain multiple reflected waves that travel back and forth two or more times between the radar sensor 100 and the object to be measured 1.

[0099] Furthermore, the detection unit 122 may be included in the transmitting / receiving unit 120, and the transmitting antenna 121Tx and receiving antenna 121Rx may be mounted on the transmitting / receiving unit 120. A single transmitting / receiving unit 120 can perform both radio wave transmission / reception and distance detection.

[0100] The system may also further include a circuit board 110 on which the transmitting / receiving unit 120 is mounted. The transmitting / receiving unit 120 mounted on the circuit board 110 can perform radio wave transmission and reception, as well as distance detection.

[0101] The system may also further include a waveguide (electromagnetic horn 130) positioned in front of the transmitting antenna 121Tx, the receiving antenna 121Rx, and the retroreflector 150. This allows for efficient propagation of radio waves toward the object to be measured 1.

[0102] The waveguide may be an electromagnetic horn 130. The electromagnetic horn 130 allows for efficient propagation of radio waves toward the object to be measured 1, and also allows for efficient propagation of radio waves reflected by the object to be measured 1 to the transmitting / receiving unit 120.

[0103] The electromagnetic horn 130 may also include a radio wave lens 140, which is provided on the electromagnetic horn 130 and positioned in front of the transmitting antenna 121Tx, the receiving antenna 121Rx, and the retroreflector 150. The radio wave lens 140 can focus radio waves and propagate them to the object to be measured 1, and the radio waves reflected by the object to be measured 1 can also be focused by the radio wave lens 140 and propagated to the transmitting / receiving unit 120, thereby enabling more efficient distance detection.

[0104] Furthermore, the system may also include a specular reflector 160, which is inserted between the object to be measured 1 and the retroreflector 150 in the first path where the radio waves are reflected from the transmitting antenna 121Tx by the object to be measured 1 and head toward the retroreflector 150, and between the object to be measured 1 and the receiving antenna 121Rx in the second path where the radio waves are reflected from the retroreflector 150 by the object to be measured 1 and head toward the receiving antenna 121Rx, and which reflects the radio waves reflected by the object to be measured 1 toward the object to be measured 1 in the first path and toward the object to be measured 1 in the second path. Since the number of round trips of radio waves between the transmitting / receiving unit 120 and the object to be measured 1 can be increased to four or more, the degree of deformation and shape variation of the object to be measured 1 included in the multiple reflected waves can be further increased, and it becomes possible to determine whether or not it is deformation or shape variation.

[0105] While exemplary embodiments of radar sensors of this disclosure have been described above, this disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0106] This international application claims priority based on Japanese Patent Application No. 2025-008704, filed on 21 January 2025, the entire contents of which are incorporated herein by reference.

[0107] 1. Object to be measured (Example of object) 100, 100M1, 100M2 Radar sensor 101 Base 110 Circuit board 120 Transmitting / receiving unit 121Rx Receiving antenna 121Tx Transmitting antenna 122 Detection unit 130 Electromagnetic horn (Example of waveguide) 140 Radio wave lens 140A Reference point 150, 150M1 Retroreflective reflector (Example of first reflector) 160 Specular reflector (Example of second reflector)

Claims

1. A radar sensor comprising: a transmitting antenna capable of transmitting radio waves toward an object; a receiving antenna capable of receiving radio waves reflected by the object; a first reflector capable of reflecting the radio waves reflected by the object toward the object; and a detection unit that detects the distance to the object based on a multiple reflected wave, which is a radio wave transmitted from the transmitting antenna, reflected by the object, reflected at least once by the first reflector, and then received by the receiving antenna.

2. The radar sensor according to claim 1, wherein the detection unit further detects the distance to the object based on the reflected wave, which is a radio wave transmitted from the transmitting antenna, reflected by the object, and then received by the receiving antenna without being reflected by the first reflector.

3. The radar sensor according to claim 1 or 2, wherein the first reflector is a retroreflector.

4. The radar sensor according to claim 1, wherein the detection unit is included in an integrated circuit chip, and the transmitting antenna and the receiving antenna are mounted on the integrated circuit chip.

5. The radar sensor according to claim 4, further comprising a substrate on which the integrated circuit chip is mounted.

6. The radar sensor according to claim 1, further comprising a waveguide disposed on the front side of the transmitting antenna, the receiving antenna, and the first reflector.

7. The radar sensor according to claim 6, wherein the waveguide is an electromagnetic horn.

8. The radar sensor according to claim 6, further comprising a radio wave lens provided in the waveguide and positioned in front of the transmitting antenna, the receiving antenna, and the first reflector.

9. The radar sensor according to claim 1, further comprising a second reflector, which is inserted between the object and the first reflector in a first path in which the radio waves travel from the transmitting antenna, reflected by the object, and toward the first reflector, and which is inserted between the object and the receiving antenna in a second path in which the radio waves travel from the first reflector, reflected by the object, toward the object in the first path, and reflected by the object, toward the object in the second path.

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