JP2006258762A - Radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar device capable of detecting precisely an azimuth of a detection object in a space. <P>SOLUTION: In this radar device 1, a transmission antenna 13 emits a pulse wave into the space, and a reflected wave from the detection object gets incident into two reception antennas 14. Tilt angles of the respective reception antennas 14 are different each other. A processing circuit 16 draws out the azimuth from a value where an amplitude difference of the incident reflected waves into the respective reception antennas 14 is normalized with an amplitude sum thereof. A circular-polarized wave antenna is arranged on a main face of a dielectric substrate in each of the transmission antenna 13 and the reception antennas 14, a strip conductor is formed on the main face to surround an antenna element. The plurality of through holes is formed in the dielectric substrate to be penetrated from a formation area on the main face to a reverse face of the dielectric substrate and to be arrayed with a prescribed interval, a plurality of connection conductors connects a ground layer formed on the reverse face electrically to the strip conductor via the each through hole. An inner edge of the strip conductor is protruded to an antenna element side more than an inner wall of the through hole. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radar apparatus, and more particularly, to a radar apparatus that emits a pulsed radio wave to a space and receives and processes a reflected wave reflected by a detection target existing in the space.

  In recent years, it has been proposed to use UWB (Ultra Wide Band), which is a quasi-millimeter wave band of 22 to 29 GHz, for short-range radar devices such as in-vehicle applications.

  The antenna of a radar device using UWB is required to have a small and thin planar structure in consideration of being installed in the gap between the vehicle body and the bumper in addition to having a wide radiation characteristic. The

  As one having a broadband radiation characteristic as described above, a spiral antenna element is provided on a relatively thick dielectric substrate (see, for example, Non-Patent Document 1). A spiral antenna is generally a balanced antenna having a pair of spiral elements. However, the antenna element according to Non-Patent Document 1 is composed of a single spiral element, enabling unbalanced power supply that does not require a balun. Yes.

  In addition to the above-described requirements, the radar device may be required to obtain an azimuth angle where the detection target exists with reference to the radar device. In order to meet this demand, the following three methods have been proposed.

  In the first method, an antenna that has an antenna lobe that converges sharply in the plane of the search angle and mechanically rotates is used. By using such an antenna, the azimuth angle of the detection target can be specified from the direction of the antenna when the reflected wave from the detection target is incident. In the second method, a phased array antenna that electronically rotates the antenna lobe is used. Even in the second method, the azimuth angle of the detection target is specified based on the direction of the antenna lobe. However, the first method has a problem that a mechanism for rotating the antenna becomes very expensive if the direction in which the detection target exists is specified with high accuracy. The second method also requires a large number of phase-controlled active elements to sharply converge the antenna lobe, so that it is very expensive to realize the above phased array antenna. There is a problem.

Therefore, a monopulse method is known as a method for specifying the detection target azimuth at a low cost (see, for example, Non-Patent Document 2). In the monopulse method, a reflected wave is received by each of a plurality of receiving antennas whose tilt angles with respect to the main radiation direction of the transmitting antenna are set to different values. In the monopulse method, the direction in which the reflected wave arrives, that is, the azimuth angle of the detection target, is determined from the value obtained by normalizing the difference in amplitude between the two received signals (reflected waves) with the sum of the two amplitude values. In addition, in order to obtain the azimuth angle of the detection target with such a monopulse method with high accuracy, it is required that the transmitting antenna and the receiving antenna have good beam characteristics.
Nakano et al., “Tilted and Axial Beam Formation by A Single Beam Rectanglar Spiral Antenna with Compact De-Electric Substrate and Conducting Plane” and Conducting Plane) ", iTriple E Trans. AP (IEEE Trans. AP), vol. 50, no. 1, pp. 17-23 January 2002 M. Skolnik, “Radar Handbook”

  However, in the case of the antenna according to Non-Patent Document 1, the thickness of the dielectric block needs to be about ½ of the wavelength (known) of the surface wave propagating on the dielectric substrate. This value is as thick as several millimeters. In particular, when an array structure is realized using this antenna, a plurality of dielectric blocks must be arranged at regular intervals. Since the antenna array thus realized has a very large thickness, there is a problem that it is not suitable for in-vehicle use or portable use where a small and thin planar structure is required.

  In the antenna according to Non-Patent Document 1, a plurality of spiral elements can be arranged on a common dielectric substrate. However, as described above, the thickness of the dielectric substrate is the wavelength of the surface wave. If it is so large that it cannot be ignored, surface waves propagating along the substrate surface are excited. In such a situation, there is a problem that each spiral element is affected by the excited surface wave, and the beam characteristics as an antenna are greatly violated. Moreover, even if such an antenna is applied to the monopulse system described in Non-Patent Document 2, the monopulse system requires an antenna with good beam characteristics as described above. There is a problem that it is difficult to detect with high accuracy.

  Therefore, an object of the present invention is to provide a radar apparatus that can detect the azimuth angle of a detection target in space with high accuracy.

  In order to achieve the above object, a first aspect of the present invention is directed to a radar device that emits radio waves to a space and receives and processes a reflected wave reflected by a detection target existing in the space. The radar apparatus includes a transmitting antenna that radiates radio waves toward a space and at least two receiving antennas each receiving reflected waves. Further, the tilt angles of the receiving antennas with respect to the main radiation direction of the transmitting antenna are set to different values.

  In the first aspect, the radar apparatus further uses the radar apparatus as a reference based on a value obtained by normalizing the amplitude difference of the reflected waves incident on the at least two receiving antennas by the sum of the amplitudes of the reflected waves. And a processing circuit for deriving a direction in which the detection target is located.

  Here, in the first aspect, the transmitting antenna and the plurality of receiving antennas are formed on a dielectric substrate, a circularly polarized antenna element disposed on a main surface of the substrate, and a back surface of the substrate. A plurality of ground layers surrounding the antenna element and disposed on the main surface of the substrate, and a plurality of strip conductors penetrating from the region where the strip conductor is formed on the main surface of the substrate to the back surface of the substrate and arranged at predetermined intervals A through hole is formed, and includes a plurality of connecting conductors that electrically connect the ground layer and the strip conductor through the through holes. The inner edge of the strip conductor protrudes closer to the antenna element than the inner wall of each through hole.

  When the antenna element according to the first aspect has a square or circular spiral shape, the distribution wiring that penetrates the ground layer and the substrate and is connected to the end on the spiral center side is connected to the transmission antenna and the plurality of reception elements. The antenna further includes.

  When there are a plurality of circularly polarized antenna elements, the strip conductor has a lattice shape, and each lattice surrounds at least one antenna element. The transmission antenna and the plurality of reception antennas further include a feed line that is formed on the back side of the substrate and provides an AC signal to each antenna element.

  The transmission antenna and the plurality of reception antennas are further provided with a distribution wiring board on which a distribution wiring is formed on the surface of the ground antenna. Further, the distribution wiring consists of strip lines.

  The transmission antenna and the plurality of reception antennas are configured with a sequential rotation array including a plurality of antenna elements. In this case, for example, the tilt angle is set by making the angles of the main surfaces of the substrates included in each receiving antenna different from the main surfaces of the substrates included in the transmitting antenna. Alternatively, the tilt angle can be changed by changing the beam direction of each receiving antenna from each other by arranging the antenna elements included in each receiving antenna and / or controlling the phase of the AC signal to be applied to the distribution wiring. The corner is set.

  The second aspect of the present invention is used in a radar apparatus and is directed to a method for detecting a direction in which a detection target in space exists. The method includes a radiation step of radiating a radio wave toward a space from a transmission antenna, a first reception step of receiving a reflected wave reflected by a detection target existing in the space by a first reception antenna, The amplitude difference between the two reception signals in the second reception step of receiving the reflected wave by the second reception antenna different from the reception antenna and the first and second reception steps is the sum of the amplitudes of the two reception signals. And a deriving step for deriving a direction in which the detection target is located based on the normalized value with respect to the radar apparatus. Here, the tilt angles of the first and second receiving antennas with respect to the radiation direction of the transmitting antenna are set to different values.

  Further, in the second aspect, the transmitting antenna, and the first and second receiving antennas are provided on a dielectric substrate, a circularly polarized antenna element disposed on a main surface of the substrate, and a back surface of the substrate. A ground layer to be formed, a strip conductor surrounding the antenna element and disposed on the main surface of the substrate, and a region penetrating from the region where the strip conductor is formed on the main surface of the substrate to the back surface of the substrate and arranged at a predetermined interval A plurality of through holes are formed, and include a plurality of connection conductors that electrically connect the ground layer and the strip conductors through the respective through holes. Here, the inner edge of the strip conductor protrudes closer to the antenna element than the inner wall of each through hole.

  According to each aspect described above, each antenna element is surrounded by a strip conductor in the transmission antenna or each reception antenna. The plurality of connection conductors formed in the substrate also surround the antenna element, and the ground layer and the strip conductor are electrically connected through each through hole. Here, the inner edge of the strip conductor protrudes closer to the antenna element than the inner wall of each through hole. With such a configuration, the generation of surface waves on the substrate main surfaces of the transmission antenna and the reception antenna can be suppressed, and the radiation characteristics of each antenna can have a desired and stable shape. By using such a transmission antenna and reception antenna, it becomes possible to accurately detect the azimuth angle by the monopulse method.

  Further, by using the resonance phenomenon of the strip conductor and the connection conductor, the frequency characteristics of the gains of the transmission antenna and the reception antenna can be sharply dropped (notched) in a predetermined radio wave emission prohibited band.

  In addition, by applying a sequential rotation array and setting the tilt angle of the receiving antenna as described above, the cross polarization component of each antenna element is canceled out, and the transmitting antenna or the receiving antenna as a whole is almost perfect. A circular polarization characteristic. As a result, a radar apparatus capable of deriving the azimuth angle of the detection target with higher accuracy can be realized.

  The above and other objects, features, aspects and advantages of the present invention will become more apparent when the detailed description of the present invention described below is understood in conjunction with the accompanying drawings.

(Embodiment)
FIG. 1 is a block diagram showing a configuration of a radar apparatus 1 according to an embodiment of the present invention. Since FIG. 1 is also used in the following two modified examples, “1a” and “1b” are shown as reference symbols of the radar apparatus in addition to the reference symbol “1”.

  In FIG. 1, a radar apparatus 1 includes a control circuit 11, a transmission circuit 12, a transmission antenna 13, at least two reception antennas 14 (two reception antennas 14L and 14R are shown), and at least one reception circuit 15 ( In the figure, two receiving circuits 15L and 15R) and a processing circuit 16 are provided.

  The control circuit 11 provides timing signals to at least the transmission circuit 12, the two reception circuits 15L and 15R, and the processing circuit 16. Each of the transmission circuit 12, the reception circuit 15L, the reception circuit 15R, and the processing circuit 16 operates according to a timing signal from the control circuit 11.

  The transmission circuit 12 generates a pulse-shaped radio wave as a radiated wave St by a known method, and gives it to the transmission antenna 13.

  The transmission antenna 13 is installed so as to be able to radiate radio waves in a predetermined main radiation direction, and radiates the radiation wave St given from the transmission circuit 12 into space. Here, when the detection target G such as an object and a human body exists in the detection area of the radar apparatus 1, the radiation wave St hits the detection target and is reflected. In the present embodiment, a reference sign “Sr” is given to such a reflected wave.

  Reflected waves Sra and Srb from the same detection target G are incident on the receiving antennas 14L and 14R, respectively. The receiving antenna 14L gives the incident reflected wave Sra to the receiving circuit 15L, and the receiving antenna 14R gives the incident reflected wave Srb to the receiving circuit 15R.

  The receiving circuits 15L and 15R perform necessary processing (for example, amplification and / or noise removal) on the given reflected waves Sra and Srb and pass them to the processing circuit 16.

  The processing circuit 16 is provided with the reflected wave Sra processed by the receiving circuit 15L and the reflected wave Srb processed by the receiving circuit 15R. The processing circuit 16 derives a difference signal Δ representing the amplitude difference between the given reflected waves Sra and Srb and a sum signal Σ representing the sum of the two amplitude values. Thereafter, the processing circuit 16 determines that the detection target G is detected with respect to the main radiation direction of the radar apparatus 1 based on a value obtained by normalizing the derived difference signal Δ with the sum signal Σ (hereinafter referred to as an angle error voltage ε). An azimuth angle Δθ representing the existing direction is derived.

  Next, the configuration of each of the transmission antenna 13, the reception antenna 14L, and the reception antenna 14R shown in FIG. 1 will be described in detail with reference to FIGS. First, FIG. 2 is a perspective view showing the appearance of each of the transmission antenna 13, the reception antenna 14L, and the reception antenna 14R. FIG. 3 is a front view showing the appearance of each of the transmission antenna 13, the reception antenna 14L, and the reception antenna 14R. FIG. 4 is an enlarged view of the antenna element 22 shown in FIG. FIG. 5 is a rear view showing the appearance of each of the transmission antenna 13, the reception antenna 14L, and the reception antenna 14R. 6 is an enlarged view of a cross section when the transmitting antenna 13, the receiving antenna 14L, and the receiving antenna 14R shown in FIG. 3 are cut along the vertical plane AA shown in FIG. 7 is an enlarged view of a cross section when the transmitting antenna 13, the receiving antenna 14L, and the receiving antenna 14R shown in FIG. 3 are cut along the vertical plane BB shown in FIG. 2 to 7 show the x axis, the y axis, and the z axis orthogonal to each other for convenience of explanation. The x axis indicates the horizontal direction, and the y axis indicates the vertical direction. The z axis indicates the normal direction of the xy plane.

  In addition, as mentioned first, in the present embodiment, the transmission antenna 13, the reception antenna 14L, and the reception antenna 14R have the same configuration. Therefore, in the following description, the configuration of the transmission antenna 13 will be described in detail on behalf of the transmission antenna 13, the reception antenna 14L, and the reception antenna 14R. Regarding the receiving antennas 14L and 14R, only differences from the transmitting antenna 13 will be described.

  2 to 7, the transmission antenna 13 mainly includes a substrate 21, an antenna element 22, a ground layer 23, a strip conductor 24, a connection conductor 25, and a feeder line 26.

  The substrate 21 is a support material on which each component of the transmission antenna 13 is formed or attached. Further, the material selected as the substrate 21 has a low dielectric constant (for example, about 3.5). The thickness of the substrate 21, that is, the length of the side parallel to the z direction is illustratively about 1.2 mm.

  The antenna element 22 is an unbalanced circularly polarized antenna that is formed on the main surface α of the substrate 21 and has a square spiral structure that extends rightward (clockwise) outward from the center of the antenna element 22. Specifically, in the rectangular spiral of the antenna element 22 shown in FIG. 4, the basic length a0 is 0.45 mm, the conductor width W is 0.25 mm, the number of turns is 2, and the final length is 3 · a0.

  The ground layer 23 is made of a conductive material, and is formed over almost the entire back surface β facing the main surface α. However, a through hole Ha is formed in the center portion of the ground layer 23 as shown in FIGS.

  The strip conductor 24 is made of a strip-like conductive material disposed on the main surface α of the substrate 21 and surrounds the antenna element 22 formed on the main surface α. Illustratively in this embodiment, the strip conductor 24 surrounds 360 ° around the antenna element 22.

  The connection conductor 25 is formed in each of the plurality of through holes Hb formed at predetermined positions on the substrate 21 and electrically connects the ground layer 23 and the strip conductor 24 described above. 3 and 5, three connection conductors are indicated using the reference symbol “25”, and in FIG. 6, two connection conductors are indicated using the reference symbol “25”. In FIG. 7, eleven connecting conductors are indicated using the reference sign “25”.

  In the present embodiment, the plurality of through holes Hb are formed in a frame-like region where the strip conductors 24 are formed on the main surface α. More specifically, the plurality of through holes Hb are arranged at predetermined intervals in parallel with the sides of the main surface α, and each of the through holes Hb penetrates the substrate 21 in the z-axis direction.

  Each connection conductor 25 is realized, for example, by plating (through-hole plating) the inner wall of each through hole Hb as described above. The diameter of each connection conductor 25 formed in this way is exemplarily 0.3 mm, and the interval between two connection conductors 25 adjacent in each side direction is exemplarily 0.9 mm. Each connection conductor 25 may be realized by filling each through hole Hb as described above with a conductive material.

  With the above-described configuration, each connection conductor 25 electrically connects the ground layer 23 and the strip conductor 24. In other words, all the connection conductors 25 are electrically short-circuited by the strip conductors 24.

Further, as shown in FIG. 6, from the viewpoint of suppressing surface waves (details will be described later), it is preferable that the inner wall of all the through holes Hb be stripped more than the virtual plane γ in contact with the most central portion of the substrate 21. inner edge length of the conductor 24 (hereinafter, referred to as rim width) L _R only, protruding antenna element 22 side.

For example, the outer shape of the main surface α is assumed to be a square whose center is the spiral center of the antenna element 22 and whose length of each side is L, as shown in FIGS. 3 and 6. Further, a virtual plane γ (one point in FIGS. 3 and 6) having a width of L _W in the x-axis and y-axis directions, a rectangular cylindrical shape, and the center axis of the imaginary plane including the center of the main surface α. It is assumed that the through holes Hb are arranged so as to be in contact with the outside of the chain line (see the chain line). Under this assumption, the rim width L _R is the shortest distance from the inner edge of the strip conductor 24 to the virtual plane γ.

Here, the optimum value of the rim width L _R depends on the frequency band of the radio wave used in the radar apparatus 1, more specifically, on the wavelength of the surface wave propagating on the principal surface α of the substrate 21. For example, when the radar apparatus 1 is applied to UWB, the rim width L _R is selected to be 1.2 mm, which is a value of about ¼ of the surface wave wavelength. Therefore, when the inner wall of each through-hole Hb is viewed from the inner edge of the strip conductor 24, the rim portion of the strip conductor 24 forms a π / 4 transmission line having an infinite impedance with respect to the wavelength of the surface wave. Accordingly, the surface wave does not propagate outside the strip conductor 24. Such a current blocking action suppresses the surface wave and can prevent the radiation characteristics from deteriorating.

  The feed line 26 is realized by an unbalanced feed line, for example, a coaxial cable, a coplanar line using the ground layer 23 as an earth line, or a microstrip line. Such a feeder line 26 passes through the through hole Ha so as not to come into contact with the ground layer 23, further penetrates the substrate 21, and is connected to the end of the antenna element 22 on the spiral center side.

  In the transmission antenna 13 configured as described above, except for the strip conductor 24 and the connection conductor 25, the structure thereof is almost the same as that of Non-Patent Document 1 described above. In such a conventional antenna, power is fed from the other end side of the feed line, whereby a radiation wave that is counterclockwise circularly polarized is radiated from the antenna element. However, in the transmission antenna having the structure according to Non-Patent Document 1, surface waves along the main surface of the substrate are excited, and good radiation characteristics cannot be obtained due to the influence of the surface waves. Therefore, by providing the transmission antenna 13 with the strip conductor 24 and the connection conductor 25 as in the present embodiment, it is possible to prevent the deterioration of the radiation characteristics due to the surface wave as described above.

  In order to explain the technical effects as described above, the applicant of the present application has changed some parameters and performed a simulation. Hereinafter, the results of this simulation will be described. In the simulation, the radar apparatus 1 uses a frequency of 26 GHz defined by UWB. The shape of the antenna element 22 is as shown in FIG.

  FIG. 8 is a diagram showing radiation characteristics on the yz plane in a conventional (non-patent document 1) transmission antenna. In FIG. 8, curves F1 and F1 ′ show the characteristics of the main polarization (left-handed polarization) and cross-polarization (right-handed polarization) when the length L shown in FIG. F2 ′ indicates the characteristics of main polarization and cross polarization when L shown in FIG. 3 is 24 mm.

  Here, as a general theory, the radiation characteristics required for an antenna are symmetric and broad single-peak characteristics with respect to the main polarization about the 0 ° direction. ), The radiation intensity needs to be sufficiently lower than that of the main polarization in a wide angle range. On the other hand, the characteristic curves F1 and F2 of the main polarization in FIG. 8 are both asymmetric and have a large gain fluctuation, and the cross polarization characteristics are apparent from the characteristic curves F1 ′ and F2 ′. It can be seen that the radiation level is equal to or close to that of the main polarization in the vicinity of −60 ° and −40 °. Such a fluctuation in radiation characteristics is caused by the influence of the surface wave as described above.

FIG. 9 is a diagram showing the radiation characteristics on the yz plane of the transmission antenna 13 (L _W = 9 mm, L _R = 1.2 mm). In FIG. 9, curves F3 and F3 ′ indicate the characteristics of the main polarization (left-handed polarization) and cross-polarization (right-handed polarization) when the length L shown in FIG. F4 ′ indicates the characteristics of main polarization and cross polarization when L shown in FIG. 3 is 24 mm.

  As is clear from FIG. 9, the characteristic curves F3 and F4 of the main polarization are symmetric with respect to the 0 ° direction and become broad single-peak characteristics, and the characteristic curves F3 ′ and F4 ′ of the cross polarization are also wide. In the angle range, the change is slow with a sufficiently lower radiation intensity than the main polarizations F3 and F4. That is, it can be seen that the transmission antenna 13 has much better radiation characteristics than the antenna shown in Non-Patent Document 1.

In addition, as a result of various experiments, the radiation characteristic in the absence of the strip conductor 24 depends on the length L of each side of the substrate 21 and the width L _{W of the} virtual plane. When L is large (L is 24 mm or 18 mm), as the width L _W increases within the range of 3 to 10 mm, the main polarization characteristic approaches a single peak from the three peaks. In addition, when L is relatively small (L = 12 mm), the main polarization characteristics approach from a bimodal to a single peak as the width L _W increases within a range of 3 to 10 mm. However, regardless of the size of L, the cross-polarized wave is greatly fluctuated, and the difference between the cross-polarized wave component and the main polarized wave component becomes small at any angle. Therefore, the polarization selectivity of the conventional transmission antenna is low, and the desired characteristics as shown in FIG. 9 cannot be obtained with the conventional antenna.

  In the above description, the antenna element 22 has been described as having a square spiral shape. However, the present invention is not limited to this, and the antenna element 22 may have a circular spiral shape as shown in FIG. For example, according to the simulation results of the applicant, the initial radius SR from the reference point P is 0.2 mm, the conductor width W is 0.35 mm, the spiral interval d is 0.2 mm, and the number of turns is 2.125. When the antenna element 22 having a circular spiral shape is used, characteristics substantially equivalent to those of the rectangular spiral antenna element 22 shown in FIG. 4 are obtained.

  In the receiving antennas 14L and 14R shown in FIG. 1, the antenna element 22 is different from the antenna element 22 of the transmitting antenna 13 in that the antenna element 22 spreads outward from the center of the antenna element 22 counterclockwise (counterclockwise). Other than that, there is no difference between the transmitting antenna 13 and the receiving antennas 14L and 14R, and therefore, description of other configurations is omitted. Further, in the following description, the same reference numerals as the corresponding components in the transmission antenna 13 are attached to the respective components that are not described.

  In the above description, the transmitting antenna 13 is clockwise and the receiving antennas 14L and 14R are counterclockwise, but each may be reversely wound.

  The main surfaces α of the receiving antennas 14L and 14R as described above are installed at different tilt angles θa and θb with respect to the main surface α of the substrate 21 of the transmitting antenna 13, as shown in FIG. Here, θa and θb may satisfy the condition of θa ≠ θb and the condition that the monitoring areas of the receiving antennas 14L and 14b partially overlap. Here, a portion where each monitoring area overlaps is a detection area of the radar apparatus 1 itself. By setting the tilt angles θa and θb as described above, the azimuth angle Δθ of the detection target G can be detected by the monopulse method using the reflected wave Sr. In this embodiment, for example, as shown in FIG. 11, the reception antenna 14L is connected to one side surface of the transmission antenna 13 so that the tilt angle is θa, and the reception antenna 14R is connected to the transmission antenna 13. The other side surface is connected so that the tilt angle is θb. Further, θa is illustratively selected to be about −20 °, and θb is illustratively selected to be about 20 °.

  As described above, in the present embodiment, the antenna element 22 of the transmission antenna 13 is right-handed (left-handed polarization), and the antenna elements 22 of the receiving antennas 14L and 14R are left-handed (right-handed polarization). Since circularly polarized radio waves have the property that the direction of polarization rotation is reversed by reflection, the direction of polarization rotation is reversed between the transmitting antenna 13 and the receiving antennas 14L and 14R. The second-order reflection component (more strictly speaking, the even-order reflection component) can be suppressed, and the selectivity with respect to the primary reflection component (more strictly speaking, the odd-order reflection component) can be increased. As a result, it is possible to reduce false images generated by secondary reflection.

  As shown in FIG. 11, when the transmitting antenna 13 and the receiving antennas 14L and 14R are arranged close to each other, the radiated wave St of the transmitting antenna 13 is directly input to the receiving antennas 14L and 14R without hitting the detection target G. However, since the rotation direction of the polarization of the receiving antennas 14L and 14R is opposite to that of the transmitting antenna 13, the direct wave can be greatly attenuated.

  Next, a detailed processing procedure of the processing circuit 16 shown in FIG. 1 will be described with reference to FIG. The processing circuit 16 first acquires the reflected wave Sra processed by the receiving circuit 15L (step S1301) and holds it. Next, the processing circuit 16 acquires the reflected wave Srb processed by the receiving circuit 15R (step S1302) and holds it. Here, as shown in FIG. 13A, the gains of the receiving antennas 14L and 14R are different from each other depending on the azimuth angle Δθ at which the detection target G exists with reference to the main radiation direction of the radar device 1, for example, the transmitting antenna 13. Have Accordingly, the amplitude values of the reflected waves Sra and Srb supplied to the processing circuit 16 change according to the azimuth angle Δθ.

  Next, the processing circuit 16 generates a sum signal Σ of both amplitude values as shown in FIG. 13B from the given reflected waves Sra and Srb (step S1303), and further, both of them as shown in FIG. 13B. An amplitude difference signal Δ is generated (step S1304). The sum signal Σ and the difference signal Δ are generated by, for example, converting the reflected waves Sra and Srb, which are analog signals, into digital signals, and digitally processing the two digital signals obtained thereby, The reflected waves Sra and Srb themselves are generated by passing them through a pre-comparator (pre-comparator).

  Thereafter, the processing circuit 16 normalizes the generated difference signal Δ with the sum signal Σ to generate an angle error voltage ε. Here, the angle error voltage ε is derived according to the following equation (1).

ε = Δ / Σ (1)
Here, FIG. 13C is a diagram illustrating a relationship between the angle error voltage ε and the angle D. As shown in FIG. 13C, the angle error voltage ε is substantially S-shaped, and the angle error voltage ε and the azimuth angle Δθ have a unique relationship in the range of most azimuth angles Δθ. Therefore, by using the relationship shown in FIG. 13C, the azimuth angle Δθ can be uniquely obtained from the reflected waves Sra and Srb. Note that only the difference signal Δ is normalized by the sum signal Σ. When the angle D is to be measured, the reflected waves Sra and Sb depend on the size of the detection target G and / or the distance to the detection target G. This is because each of the amplitude values changes greatly. That is, although the direction of the detection target G is the same, the value of the difference signal Δ varies greatly depending on the size of the detection target G and / or the distance to the detection target G.

  The processing circuit 16 holds a table describing the relationship as shown in FIG. 13C in an internal memory (not shown), and the azimuth angle Δθ uniquely corresponding to the angular error voltage ε derived in step S1305. Is acquired (step S1306).

  As described above, according to the radar apparatus 1 according to the present embodiment, as described above, the radiated wave St (left-handed) having a clean beam shape without the influence of the surface wave is transmitted from the transmitting antenna 13 having the above-described structure. The reception antennas 14L and 14R having a similar structure receive the primary reflected waves Sra and Srb with respect to the counterclockwise circular polarization with high sensitivity. The radar apparatus 1 increases the azimuth angle Δθ by using the transmission antenna 13 and the reception antennas 14L and 14R having good beam characteristics, and the processing circuit 16 derives the azimuth angle Δθ of the detection target G in a monopulse method. It can be detected with accuracy.

(First modification)
Next, a first modification of the above embodiment (hereinafter referred to as a radar device 1a) will be described with reference to FIG. In FIG. 1, the radar device 1a is different from the radar device 1 in that the transmission antenna 13, the reception antenna 14L, and the reception antenna 14R are replaced with the transmission antenna 13a, the reception antenna 14La, and the reception antenna 14Ra. Since there is no difference between the two radar devices 1 and 1a, the description of the radar device 1a corresponding to the configuration of the radar device 1 is omitted.

  Here, FIG. 14 is a schematic diagram showing a schematic configuration of the transmission antenna 13a, the reception antenna 14La, and the reception antenna 14Ra shown in FIG. In FIG. 14, the transmission antenna 13a is largely different from the transmission antenna 13 described above in that it has an array structure. As a result, the antenna gain can be improved, and a radiation wave St having a more preferable beam shape can be radiated into the space.

  When arraying a plurality of circularly polarized antenna elements, a sequential rotating array can be employed. A sequential rotation array is an antenna array that satisfies the following conditions. First, N antenna elements having the same shape (N is an even number of 2 or more) are arranged in a matrix on the same plane. In the transmission antenna 13a illustrated in FIG. 14, eight antenna elements having the same shape are arranged.

  As a second condition, when each antenna element is viewed along the x-axis direction and / or the y-axis direction, the antenna element is sequentially rotated by p · π / N radians around the axis in the radial direction of the spiral. It is a point that is placed on the target plane. In the illustration of FIG. 14, the two antenna elements arranged along the x-axis direction satisfy the second condition.

  Third, the phase of the AC signal supplied to each antenna element differs by p · π / N radians depending on the rotation angle of each antenna element. Here, p is an integer of 1 to N-1.

  By adopting the array structure as described above, even if the polarization characteristics of each antenna element are incompletely circularly polarized (that is, elliptically polarized), the cross-polarized wave component is not obtained as a whole in the transmission antenna 13a. As a result, the transmitting antenna 13a can obtain almost perfect circular polarization characteristics.

  Hereinafter, with reference to FIG. 15, the principle of the sequential rotation array when p is 1 and N is 2 will be described. As shown in FIG. 15, it is assumed that the first antenna element has an elliptical polarization characteristic A1 in which the intensity in the horizontal axis direction is a + b and the intensity in the vertical axis direction is a−b. This elliptical polarization characteristic A1 includes a main polarization component B1 (circular polarization) counterclockwise (counterclockwise) at intensity a and a cross-polarization component C1 (circular polarization) clockwise (clockwise) of intensity b. Wave).

  In addition, the second antenna element arranged with the first antenna element rotated by π / 2 radians has a vertically long intensity a + b and a horizontal axis intensity ab. It has an elliptical polarization characteristic A2. This vertically elliptical polarization characteristic A2 is a combination of a counterclockwise main polarization component B2 (circular polarization) with intensity a and a clockwise cross polarization component C2 (circular polarization) with intensity b. Can be considered.

  However, when in-phase AC signals are fed to the first and second antenna elements, the polarization directions of both are shifted by π / 2 radians from each other in both the main polarization and the cross polarization.

  Therefore, if the phase of the AC signal fed to the second antenna element is delayed by π / 2 radians with respect to the phase of the AC signal fed to the first antenna element, the main bias of the second antenna element is reduced. The wave component B2 ′ is in phase with the main polarization component B1 of the first antenna element, and is synthesized so that both are emphasized.

  On the other hand, when an AC signal delayed in phase as described above is given to the second antenna element, a cross polarization component C2 ′ is obtained. Therefore, when the cross polarization components C2 ′ and C1 are combined, they are canceled out.

  From the above, the polarization characteristics of the transmission antenna 13a as a whole are almost complete circular polarization characteristics in which the counterclockwise main polarization components B1 and B2 'are combined.

  In this modification, applying the above principle, the transmission antenna 13a has a two-row, four-stage array structure in which p is 2 and N is 8, as shown in FIG.

Further, as shown in FIG. 14, the receiving antennas 14La and 14Ra are common in that they have an array structure of two rows and four stages like the transmitting antenna 13a. However, the two-row, four-stage antenna array constituting the receiving antenna 14La is obtained by inverting the antenna array of the transmitting antenna 13a by 180 ° around the y-axis. That is, for example, in FIG. 14, the antenna element 22 ₁₁ of the receiving antenna 14La has a spiral shape Turn the antenna element 22 ₂₁ of the transmitting antenna 13a. The receiving antennas 14La and 14Ra have the same array structure.

  These transmitting antenna 13a and receiving antennas 14La and 14Ra are arranged in the same manner as the transmitting antenna 13 and receiving antennas 14L and 14R (see FIG. 11) of the above-described embodiment, as shown in the lower part of FIG.

Hereinafter, the configurations of the receiving antennas 14La and 14Ra shown in FIG. 14 will be described in detail with reference to FIGS. First, FIG. 16 is a front view showing the appearance of the receiving antennas 14La and 14Ra. FIG. 17 is a side view showing the appearance of the receiving antennas 14La and 14Ra. FIG. 18 is a rear view showing the appearance of the receiving antennas 14La and 14Ra.
16 to 18 show the x axis, the y axis, and the z axis orthogonal to each other for convenience of explanation. The x axis indicates the horizontal direction, and the y axis indicates the vertical direction. The z axis indicates the normal direction of the xy plane.

  Further, as described above, since both the receiving antennas 14La and 14Ra are the same, in the following description, the configuration of the receiving antenna 14La will be described in detail on behalf of both.

16-18, the receiving antenna 14La includes a vertically long rectangular common substrate 21a and eight antenna elements 22a (22 ₁₁ , 22 ₁₂ , 22 ₁₃ , 22 ₁₄ , 22 ₂₁₎ arrayed in two rows and four stages. 22 ₂₂ , 22 ₂₃ and 22 ₂₄ ), a common ground layer 23a, a strip conductor 24a, a plurality of connection conductors 25a, eight feeders 26a, a distribution line 27a, and a distribution line substrate 28a. including.

  The common substrate 21a is a support material having a low dielectric constant on which each component of the reception antenna 14La is formed or attached.

Each antenna element 22a is arranged on the main surface α of the common substrate 21a in the manner described above, thereby forming a two-row, four-stage antenna array. Specifically, the four antenna elements 22 _{11 to} 22 ₁₄ positioned in the left column have the same axis rotation angle along the radial direction of the spiral, and the four antenna elements 22 _{21 to} 22 in the right column are the same. ₂₄ are arranged in a state where the angles around the axis along the radial direction of the spiral are the same, but are rotated counterclockwise by π / 2 radians from the adjacent antenna elements 22 _{11 to} 22 _{14 in} the x-axis direction. The

  The ground layer 23a is made of a conductive material, and is formed over almost the entire back surface β of the common substrate 21a. Further, as shown in FIG. 18, in the ground device 23 a, eight through holes Ha are opened at necessary positions in the same manner as in the above-described embodiment in order to pass the eight power supply lines 26 a.

  The strip conductor 24a is made of a lattice-like conductive material disposed on the main surface α of the common substrate 21a. In this modification, one antenna element 22a is arranged in each lattice. However, a plurality of antenna elements 22a may be arranged in one grating under the condition that the polarization characteristics of the receiving antenna 14La are not impaired.

  The connection conductor 25a is formed in each of a plurality of through-holes Hb (for convenience, only two are shown in FIG. 18) formed at predetermined positions on the common substrate 21a, and electrically connects the ground layer 23a and the strip conductor 24a. Connect to. In FIG. 16 and FIG. 18, 21 connection conductors are indicated by using the reference sign “25a”. Further, the plurality of through holes Hb are formed in a lattice-like region where the strip conductors 24a are formed on the main surface α, as in the above-described embodiment. More specifically, the plurality of through holes Hb are arranged at predetermined intervals in parallel with the sides of the main surface α, and each of the through holes Hb penetrates the common substrate 21a in the z-axis direction.

In the strip conductor 24a and the connection conductor 25a, as in the case of the strip conductor 24 and the connection conductor 25 in the above-described embodiment, the inner edge of each grid included in the strip conductor 24a is a rim with respect to the connection conductor 25a. The width L _R protrudes toward the antenna element 22 in the lattice. As a result, the generation of surface waves propagating through the common substrate α is suppressed.

  Each feeder 26a is realized by an unbalanced feeder, for example, a coaxial cable, a coplanar line using the ground layer 23a as an earth line, or a microstrip line. One end of each power supply line 26a passes through the corresponding through hole Ha and further passes through the common substrate 21a so as not to contact the ground layer 23a, and is connected to the end of the antenna element 22a on the spiral center side. Further, another end of each power supply line 26a is connected to the distribution wiring 27a.

The distribution wiring 27a is formed on the substrate 28a stacked on the ground layer 23a, and the input / output line 271a connected to the transmission circuit 13a, the reception circuit 14La or the reception circuit 14Ra, and a line extending in the negative direction of the x axis therefrom. 272La and a line 272Ra extending from the input / output line 271a in the positive direction of the x-axis. Also, distribution wire 27a is a line 273La extending from the end of the line 272La in the positive direction of the y-axis, and two-branch from the end of the line 273La, line 274La connected to the feed line 26a of the antenna element 22 ₁₁ and 22 ₁₂ And 275 La.

  The distribution wiring 27a further includes lines 276La, 277La, and 278La having a shape symmetrical to the line 272La with respect to the lines 273La, 274La, and 275La.

Furthermore, distribution wire 27a is a line 273Ra extending from the end of the line 272Ra in the positive direction of the y-axis, and two-branch from the end of the line 273Ra, line 274Ra which is connected to the feed line 26a of the antenna element 22 ₂₁ and 22 ₂₂ And 275Ra.

  The distribution wiring 27a further includes lines 276Ra, 277Ra, and 278Ra having a shape symmetrical to the line 272Ra with respect to the lines 273Ra, 274Ra, and 275Ra.

Here, when viewed from the input / output line 271a, the line lengths La to the respective feeding lines 26a of the antenna elements 22 _{11 to} 22 ₁₄ are set to be equal to each other. Further, when viewed from the input / output line 271a, the line lengths Lb to the feed lines 26a of the antenna elements 22 _{21 to} 22 ₂₄ are set to be equal to each other. However, in order to configure the sequential rotation array, the line length La is set shorter than the line length Lb by a length corresponding to π / 2 radians of the propagation wavelength of the signal at the use frequency (for example, 26 GHz). In the example of FIG. 18, the phase delay of the AC signal applied to the receiving antenna 14La is realized by changing the path length difference between the line lengths La and Lb and the lengths of the lines 272La and 272Ra. The phase delay as described above may be realized by using other lines constituting the wiring 27a.

In the reception antenna 14La configured as described above, the generation of surface waves is suppressed by the connection conductor 25a and the strip conductor 24a, and the polarization characteristics of each antenna element 22a have a single peak directivity. 14La as a whole, due to the configuration of the above-described sequential rotation array, the cross polarization components of the four antenna elements 22 _{21 to} 22 ₂₄ depicted on the right side in FIG. 16 and the four antenna elements 22 ₁₁ to 22 on the left side 22 ₁₄ and cross-polarization components are canceled out as a result, the main polarized wave component of the eight antenna elements 22a are combined. As a result, the receiving antenna 14La has almost perfect circular polarization characteristics, so that it is possible to realize the high-gain receiving antenna 14La.

  Further, since the four antenna elements 22a are arranged on the main surface α along the y-axis direction, the beam spread on the vertical plane can be appropriately narrowed, and the radiated wave St (see FIG. 1) can be reduced in the UWB band. Even in the case where a component in the prohibited frequency band is included, the transmitting antenna 13a can suppress the radiation in the high elevation direction, which is a problem, and prevents substantial interference in the prohibited frequency band. be able to.

  In the present modification, the distribution wiring 27a is constituted by a microstrip line formed on the substrate 28a. However, the present invention is not limited to this, and the distribution wiring 27a may be configured by a coplanar line. In this case, a coplanar line may be formed on the substrate 28a, or a coplanar line may be formed directly on the ground layer 23a.

In this modification, all the antenna elements 22a arranged along the y-axis direction, for example, the antenna elements 22 _{11 to} 22 ₁₄ have the same rotation angle and are adjacent to each other in the x-axis direction. For example, the antenna elements 22 ₁₁ and 22 ₂₁ have been described as having different rotation angles by π / 2 radians. However, a sequential rotation array can be realized by arranging the antenna element 22a in another manner.

For example, the following sequential rotating array. First, the rotation angles of the four antenna elements 22 _{11 to} 22 ₁₄ arranged in the y-axis direction are shifted by π / 2 radians sequentially from the top, and the rotation angles of the four antenna elements 22 _{21 to} 22 ₂₄ are , Shifted by π / 2 radians sequentially from the top. Furthermore, adjacent antenna elements 22a along the x-axis have rotation angles different from each other by π / 2 radians.

In addition, as shown in FIG. 19, it is also possible to form a sequential rotation array with only two antenna elements 22 ₁₁ and 22 ₁₂ arranged in the y-axis direction. The same applies to the combination of antenna elements 22 ₁₃ and 22 _14, the combination of antenna elements 22 ₂₁ and 22 ₂₂ , and the combination of antenna elements 22 ₂₃ and 22 ₂₄ . That is, the rotation angle of the antenna element 22 ₁₂ is shifted by π / 2 radians with respect to the antenna element 22 ₁₁ , the antenna element 22 ₁₃ is arranged at the same rotation angle as the antenna element 22 _11, and the antenna element 22 ₁₄ is They are arranged at the same rotational angle and the antenna element 22 _12. Further, the antenna elements 22 _{21 to} 22 ₂₄ are arranged with the rotation angle shifted by π / 2 radians from the adjacent antenna elements 22 _{11 to} 22 ₁₄ along the x-axis direction.

A sequential rotating array as shown in FIG. 20 can also be configured. That is, in FIG. 20, the rotation angles of the four antenna elements 22 _{11 to} 22 ₁₄ arranged in the y-axis direction are shifted by π / 4 radians sequentially from the top, and the four antenna elements 22 _{21 to} 22 ₂₄ Are rotated by π / 4 radians sequentially from the top. Furthermore, adjacent antenna elements 22a along the x-axis have rotation angles different from each other by π / 2 radians.

A sequential rotating array as shown in FIGS. 21 and 22 can also be configured. That is, in FIG. 21 and FIG. 22, the transmission antenna 13a and the reception antennas 14La and 14Ra may be configured by four antenna elements 22 _{11 to} 22 ₁₄ arranged in the y-axis direction. Specifically, in FIG. 21, a sequential rotation array is configured by shifting the rotation angle of the upper two antenna elements 22 ₁₁ and 22 ₁₂ by π / 2 radians, and the lower two antenna elements 22 are further formed. Similar sequential rotating arrays are constructed using ₁₃ and 22 ₁₄ . FIG. 22 shows a case where the rotational angle deviation is π / 4.

  Although not shown in particular, in any of the cases shown in FIGS. 19 to 22, the distribution wiring 27 a as described above causes the antenna elements 22 a having a reference rotation angle to be in-phase with each other. To the antenna elements 22a arranged at other rotation angles, an AC signal having a phase difference according to the rotation angle is given, so that the main polarization components are in phase and the cross polarization components are It becomes possible to set it as a reverse phase.

  Further, in order to narrow the beam width in the horizontal direction, in the transmission antenna 13a and the reception antennas 14La and 14Rax shown in FIGS. good.

  By the way, in the transmitting antenna according to the above-described embodiment or modification, a resonator is formed by connecting conductors and strip conductors arranged on a substrate, and a signal having a resonance frequency is excited by a circularly polarized antenna element. Can be considered. Here, the resonance frequency is determined by the circuit constant of the resonator and / or the structural parameter of the circularly polarized antenna element. At such a resonance frequency, the input impedance of the antenna element becomes very large and the radiation wave St is not radiated. Therefore, the frequency characteristic of the antenna gain has a sudden deep drop (notch) near the resonance frequency. If this resonance frequency is matched with, for example, a radio wave emission prohibition band (23.6 to 24.0 GHz) defined by UWB, interference with the earth exploration satellite can be significantly reduced by using only the antenna.

  In consideration of the above, the applicant made a prototype of a circularly polarized antenna having the configuration shown in FIG. 19, and further measured the frequency characteristics of the gain of such a circularly polarized antenna. FIG. 23 is a diagram showing a gain characteristic curve with respect to frequency for the circularly polarized antenna having the configuration shown in FIG. As shown in FIG. 23, it can be seen that the gain of the circularly polarized antenna is maintained at 14 dBi from 24 to 30 GHz, and that a sharp notch is generated in the vicinity of 23.2 GHz, which is approximately 20 dB lower than the peak level. .

(Second modification)
Next, a second modification (hereinafter referred to as a radar device 1b) of the above-described embodiment will be described with reference to FIG. In FIG. 1, the radar apparatus 1b is different from the radar apparatus 1 in that the transmission antenna 13, the reception antenna 14L, and the reception antenna 14R are replaced with the transmission antenna 13b, the reception antenna 14Lb, and the reception antenna 14Rb. Since there is no difference between the two radar apparatuses 1 and 1b, the description of the radar apparatus 1b corresponding to the configuration of the radar apparatus 1 is omitted.

  Here, FIG. 24 is a schematic diagram showing a schematic configuration of the transmission antenna 13b, the reception antenna 14Lb, and the reception antenna 14Rb shown in FIG. In FIG. 24, the transmission antenna 13b, the reception antenna 14Lb, and the reception antenna 14Rb are formed or attached on the common substrate 21b.

  The common substrate 21b is made of a material having a low dielectric constant (for example, about 3.5) and includes a flat main surface α and a back surface β. A ground layer is formed on the back surface β in the same manner as in the first modification, and a distribution wiring board is laminated on the ground layer. Refrain.

  The transmission antenna 13b is the above-described sequential rotation array. In the transmission antenna 13b, the four antenna elements 22a arranged in the y-axis direction are shifted by π / 2 radians sequentially from the top. Similarly to the first modification, the transmission antenna 13b includes a strip conductor, a plurality of connection conductors, a feeder line corresponding to the number of elements of the antenna element 22a, and a distribution wiring. Since it is the same as that of an example, illustration and description are omitted.

Next, the configuration of the reception antenna 14Lb shown in FIG. 24 will be described in detail with reference to FIGS. FIG. 25 is a front view showing the appearance of the receiving antenna 14Lb, and FIG. 26 is a rear view showing the appearance of the receiving antenna 14Lb. 25 and 26, the receiving antenna 14Lb includes eight antenna elements 22a (22 ₁₁ , 22 ₁₂ , 22 ₁₃ , 22 ₁₄₎ arrayed in two rows and four stages, each formed on the main surface α. 22 ₂₁ , 22 ₂₂ , 22 ₂₃ and 22 ₂₄ ) and a strip conductor 24b similar to the aforementioned strip conductor 24a (see FIG. 25), and further, a distribution wiring 27b (see FIG. 26 (see the hatched area). The reception antenna 14Lb includes a plurality of connection conductors and feeders corresponding to the number of elements of the antenna element 22a, as in the first modification, but these are the same as in the first modification. Therefore, illustration and description are omitted.

As shown in FIG. 25, the two antenna elements 22a adjacent in the y-axis direction (e.g., a combination of the antenna elements 22 ₁₁ and 22 ₁₂₎ are offset from each other by the same angle of rotation. Further, the two antenna elements 22a adjacent in the x-axis direction (e.g., a combination of the antenna elements 22 ₁₁ and 22 ₂₁₎ are arranged in a state of being offset by the angle of rotation of [pi / 2 radians from one another.

  In addition, as shown in FIG. 24, in this modification, the transmission antenna 13b and the reception antenna 14Lb are formed on the same plane. Therefore, in order to obtain the technical effect as in the first modification, It is necessary to control the phase of the AC signal applied to the receiving antenna 14Lb and tilt the beam direction of the receiving antenna 14Lb with respect to the main radiation direction of the transmitting antenna 13b in the positive direction of the x axis.

Due to the tilt as described above, in this modification, as shown in FIG. 26, the distribution wiring 27b is formed on a substrate stacked on the ground layer and is connected to the input / output line 271b connected to the receiving circuit 14Lb. And a line 272Lb extending in the negative direction of the x-axis and a line 272Rb extending in the positive direction of the x-axis from the input / output line 271b. Also, distribution wire 27b is a line 273Lb extending from the end of the line 272Lb the positive direction of the y-axis, and split into two from the end of the line 273Lb, line 274Lb are connected to the feed line of the antenna elements 22 ₂₁ and 22 ₂₂ and 275Lb. Also, distribution wire 27b is a line 276Lb extending from the end of the line 272Lb in the negative direction of the y-axis, and two-branch from the end of the line 276Lb, line 277Lb are connected to the feed line of the antenna elements 22 ₂₃ and 22 ₂₄ and 278Lb.

  The distribution wiring 27b includes a central axis parallel to the yz plane and parallel to the y-axis direction of the strip conductor 24b (see the dotted line portion) with respect to the lines 273Lb, 274Lb, 275Lb, 276Lb, 277Lb, and 278Lb. Further included are 273Rb, 274Rb, 275Rb, 276Rb, 277Rb and 278Rb having a shape symmetrical to the reference plane ν.

Here, viewed from the input-output line 271b, the line length to the feed line of the antenna element 22 ₂₁ is set to La. Also, as viewed from the input and output lines 271b, the line length to the feed line of the antenna element 22 ₂₂ is set to Lb. However, in order to configure the sequential rotation array, the line length Lb is set longer than the line length La by a length corresponding to π / 2 radians of the propagation wavelength of the signal at the use frequency (for example, 26 GHz). . Similarly, the line lengths to the respective feed lines of the antenna elements 22 ₂₃ and 22 ₂₄ have the same relationship as the line lengths to the respective feed lines of the antenna elements 22 ₂₁ and 22 ₂₂ . The line length to the feed line of the antenna elements 22 _{11 to} 22 ₁₄ is selected in the same manner. A phase delay is realized by setting the line length represented by the above, and a sequential rotation array is realized.

Also, as viewed from the input and output lines 271b, with respect to the line length La to the feed line of the antenna elements 22 _21, line length Lc to the feed line of the antenna element 22 _11, the propagation wavelength of signals usable frequency (e.g. 26 GHz) The lengths of the lines 272Lb and 272Rb are selected so as to increase by a length corresponding to π / 2 radians. Specifically, the line 272Lb is selected to be longer than the line 272Rb by a length corresponding to π / 2 radians of the propagation wavelength. Such line length setting, the same relationship, and the line length Lb to the feed line of the antenna elements 22 _22, line length difference between the line length Ld to the feed line of the antenna elements 22 _12, the antenna element 22 ₂₃ and the line length Le to the feed line, the line length difference between the line length Lf to the feed line of the antenna elements 22 _13, and the line length Lg to the feed line of the antenna elements 22 _24, the feed line of the antenna elements 22 ₁₄ The present invention is also applied to the line length difference with the line length Lh.

  By setting the line length as described above, phase control of the AC signal applied to the reception antenna 14Lb is realized, and the beam direction of the reception antenna 14Lb with respect to the main radiation direction of the transmission antenna 13b is set to an angle θa in the positive direction of the x axis. Can be tilted only.

  Next, the receiving antenna 14Rb is different from the receiving antenna Lb in that the receiving antenna 14Rb has a distribution wiring having a shape symmetrical with respect to the reference plane ν. Other than that, there is no difference between the two receiving antennas 14Rb and Lb, and therefore the description of the receiving antenna 14Rb is omitted. With such a distribution wiring, phase control of the AC signal applied to the receiving antenna 14Rb is realized, and the beam direction of the receiving antenna 14Rb with respect to the main radiation direction of the transmitting antenna 13b is set to the positive direction of the x axis by an angle θb. It can be tilted.

  With the configuration as described above, the radar apparatus 1b also has the same technical effect as the radar apparatus 1a.

In the radar apparatus 1b, the eight antenna elements 22 _{11 to} 22 ₂₄ included in the reception antenna 14Lb may be arranged as shown in FIG. Specifically, the two antenna elements 22a adjacent in the y-axis direction (e.g., a combination of the antenna elements 22 ₁₁ and 22 ₁₂₎ only [pi / 2 radians with each other, are arranged in a state of being rotated in a spiral around the center . Further, the two antenna elements 22a adjacent in the x-axis direction (e.g., the antenna combination of the elements 22 ₁₁ and 22 ₂₁₎ also only [pi / 2 radians with each other, are arranged in a state of being rotated in a spiral around the center.

In the case of the arrangement as described above, the eight antenna elements 22 _{11 to} 22 ₂₄ included in the reception antenna 14Rb are plane-symmetric with the eight antenna elements 22 _{11 to} 22 ₂₄ included in the reception antenna 14Lb with respect to the reference plane ν. It is arranged to become.

  Further, in the case of the arrangement as described above, the distribution wiring 27b provided in the receiving antennas 14Lb and 14Rb has a symmetrical shape with respect to the reference plane ν as shown in FIG. 28 as compared with that shown in FIG. Is different. Specifically, the lines 272Lb and 272Rb are set to the same length.

  The radar apparatus 1b also exhibits the same technical effect as the radar apparatus 1a even with the configuration shown in FIGS.

  FIGS. 29A to 29C are schematic diagrams showing the utility when the above-described radar devices 1, 1 a and 1 b are mounted on the vehicle V. FIGS. As described above, the radar devices 1, 1 a and 1 b can detect the azimuth angle Δθ with high accuracy. Further, as is well known, an alarm device for deriving a predicted travel locus of the vehicle V (see the dotted lines in FIGS. 29A to 29C) and warning that the vehicle V will collide with the surrounding obstacle G if it proceeds as it is. is there. When the radar devices 1, 1 a and 1 b are incorporated in such an alarm device, even if an obstacle (that is, a detection target) G exists behind the vehicle V, the vehicle V Only when it can be determined that a collision has occurred with the detection target G (see FIG. 29A), the alarm device can issue an alarm. In other words, the alarm device does not issue an alarm when it can be determined that it does not collide with the detection target G according to the current predicted travel locus (see FIGS. 29B and 29C).

  As described above, when any one of the radar devices 1, 1 a, and 1 b is combined with an alarm device, a more detailed alarm can be performed.

  Further, the radar devices 1, 1 a and 1 b can be applied in addition to the on-vehicle use. For example, if it is installed inside or outside a building, it can also be used for security purposes, for example, counting the number of people entering and leaving a room.

  As mentioned above, although this invention was demonstrated in detail, the said description is an illustration in all the meanings, and is not restrictive. It will be appreciated that many other modifications and variations are possible without departing from the scope of the invention.

  The radar apparatus according to the present invention is suitable for in-vehicle applications, security applications, and the like that are required to detect a detection target with high accuracy.

The block diagram which shows the structure of the radar apparatus 1-1d which concerns on each embodiment of this invention. The perspective view which shows the external appearance of the transmitting antenna 13, the receiving antenna 14L, and the receiving antenna 14R which are shown in FIG. Front view of transmitting antenna 13, receiving antenna 14L, and receiving antenna 14R shown in FIG. 3 is an enlarged view of the antenna element 22 shown in FIG. 3 as viewed from above. Rear view of transmitting antenna 13, receiving antenna 14L, and receiving antenna 14R shown in FIG. The figure which expanded the cross section when the transmitting antenna 13, receiving antenna 14L, and receiving antenna 14R shown in FIG. 3 are cut | disconnected by plane A-A 'shown in FIG. The figure which expanded the cross section when the transmitting antenna 13, receiving antenna 14L, and receiving antenna 14R shown in FIG. 3 are cut | disconnected by plane B-B 'shown in FIG. The figure which shows the radiation characteristic of the yz surface in the transmission antenna of the past (nonpatent literature 1) The figure which shows the radiation characteristic of yz surface of the transmission antenna 13 shown in FIG. Schematic diagram showing an alternative example of the antenna element 22 shown in FIG. Schematic diagram illustrating an arrangement example of the transmission antenna 13, the reception antenna 14L, and the reception antenna 14R illustrated in FIG. The flowchart which shows the process sequence of the processing circuit 16 shown in FIG. Schematic diagram showing characteristics of gain with respect to the existence direction Δθ for each of the receiving antennas 14L and 14R shown in FIG. Schematic diagram showing sum signal Σ and difference signal Δ obtained by processing circuit 16 shown in FIG. Schematic diagram showing characteristics of the angle error voltage ε obtained by the processing circuit 16 shown in FIG. Schematic diagram showing a schematic configuration of the transmitting antenna 13a, the receiving antenna 14La, and the receiving antenna 14Ra according to the first modification of the present invention. External view of the antenna unit of the radar apparatus according to the second embodiment of the present invention. Schematic diagram for explaining the principle of an example where p is 1 and N is 2 for a sequential rotating array Front view showing the appearance of the receiving antennas 14La and 14Ra shown in FIG. Side view showing the appearance of the receiving antennas 14La and 14Ra shown in FIG. The rear view which shows the external appearance of receiving antenna 14La and 14Ra shown in FIG. Schematic diagram showing a first alternative example of the receiving antennas 14La and 14Ra shown in FIG. Schematic diagram showing a second alternative example of the receiving antennas 14La and 14Ra shown in FIG. Schematic diagram showing a third alternative example of the receiving antennas 14La and 14Ra shown in FIG. Schematic diagram showing a fourth alternative example of the receiving antennas 14La and 14Ra shown in FIG. The figure which shows the frequency characteristic of the gain of the resonator comprised by the connection conductor and strip conductor in a 1st modification. The schematic diagram which shows schematic structure of the transmission antenna 13b, the receiving antenna 14Lb, and the receiving antenna 14Rb which concern on the 2nd modification of this invention. Front view of the receiving antenna 14Lb shown in FIG. Rear view of the receiving antenna 14Lb shown in FIG. Front view of an alternative example of the receiving antenna 14Lb shown in FIG. Rear view of an alternative example of the receiving antenna 14Lb shown in FIG. FIG. 1 is a first schematic diagram showing usefulness when the radar apparatuses 1, 1 a and 1 b shown in FIG. Second schematic diagram showing usefulness when the radar apparatus 1, 1a and 1b shown in FIG. FIG. 3 is a third schematic diagram showing usefulness when the radar apparatuses 1, 1 a and 1 b shown in FIG.

Explanation of symbols

1, 1a, 1b Radar device 11 Control circuit 12 Transmission circuit 13, 13a, 13b Transmission antenna 21 Substrate 21a Common substrate 22, 22a Antenna element 23 Ground layer 23a Common ground layer 24, 24a Strip conductors 25, 25a Connection conductors 26, 26a Feed line 27a Distribution wiring 28a Distribution wiring board α Main surface β Back surface Ha, Hb Through holes 14L, 14R, 14La, 14Ra, 14Lb, 14Rb Reception antennas 15L, 15R Reception circuit 16 Processing circuit

Claims (7)

A radar device that emits radio waves into space and receives and processes reflected waves reflected by a detection target existing in space,
The radar device is
A transmitting antenna that radiates the radio waves toward space;
And at least two receiving antennas each receiving the reflected wave,
The tilt angle of each receiving antenna with respect to the main radiation direction of the transmitting antenna is set to a value different from each other,
The radar device further includes
A process of deriving a direction in which the detection target is located with reference to the radar apparatus, based on a value obtained by normalizing a difference in amplitude of reflected waves incident on the at least two receiving antennas with a sum of amplitudes of reflected waves. With a circuit,
The transmitting antenna and the plurality of receiving antennas are:
A dielectric substrate;
A circularly polarized antenna element disposed on the main surface of the substrate;
A ground layer formed on the back surface of the substrate;
A strip conductor surrounding the antenna element and disposed on a main surface of the substrate;
A plurality of through holes penetrating from the region where the strip conductor is formed on the main surface of the substrate to the back surface of the substrate and arranged at a predetermined interval are formed, and the ground layer and the strip conductor are connected to each other. Including a plurality of connecting conductors electrically connected through the through holes,
A radar device, wherein an inner edge of the strip conductor protrudes closer to the antenna element than an inner wall of each through hole.   In the case where the antenna element has a square or circular spiral shape, distribution wiring that penetrates the ground layer and the substrate and is connected to the end portion on the spiral center side is connected to the transmission antenna and the plurality of reception antennas. The radar apparatus according to claim 1, further comprising: The circularly polarized antenna elements are plural,
The strip conductor has a grid-like shape, each grid surrounding at least one antenna element;
The transmitting antenna and the plurality of receiving antennas are further
The radar apparatus according to claim 1, further comprising a feeder line formed on a back surface side of the substrate and supplying an AC signal to each of the antenna elements. The transmitting antenna and the plurality of receiving antennas are further
A distribution wiring board that is laminated on the ground layer and on which the distribution wiring is formed;
The radar apparatus according to claim 3, wherein the distribution wiring is a strip line. The transmitting antenna and the plurality of receiving antennas are configured with a sequential rotating array composed of the plurality of antenna elements,
The radar apparatus according to claim 3, wherein the tilt angle is set by making an angle of a main surface of a substrate included in each reception antenna different from a main surface of a substrate included in the transmission antenna. The transmitting antenna and the plurality of receiving antennas are configured with a sequential rotating array composed of the plurality of antenna elements,
The tilt angle is obtained by making the beam directions of the reception antennas different from each other by arranging the antenna elements included in the reception antennas and / or controlling the phase of an AC signal to be applied to the distribution wiring. The radar apparatus according to claim 3, wherein the angle is set. A method of detecting a direction in which a detection target in space is present, used in a radar device,
The method
A radiation step for radiating radio waves from the transmitting antenna toward the space;
A first receiving step of receiving a reflected wave reflected by a detection target existing in space by a first receiving antenna;
A second receiving step of receiving the reflected wave by a second receiving antenna different from the first receiving antenna;
Based on the value obtained by normalizing the amplitude difference between the two received signals in the first and second receiving steps with the sum of the amplitudes of the two received signals, the direction in which the detection target is located is derived with reference to the radar device. A derivation step to
The tilt angles based on the radiation direction of the transmitting antenna, which are parameters of the first and second receiving antennas, are set to different values.
The transmitting antenna, and the first and second receiving antennas are
A dielectric substrate;
A circularly polarized antenna element disposed on the main surface of the substrate;
A ground layer formed on the back surface of the substrate;
A strip conductor surrounding the antenna element and disposed on a main surface of the substrate;
A plurality of through holes penetrating from the region where the strip conductor is formed on the main surface of the substrate to the back surface of the substrate and arranged at a predetermined interval are formed, and the ground layer and the strip conductor are connected to each other. Including a plurality of connecting conductors electrically connected through the through holes,
The direction detection method, wherein an inner edge of the strip conductor protrudes closer to the antenna element than an inner wall of each through hole.

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