JP2005094537A - Antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the radiation of leakage radio waves in an antenna device used to a radar or radio communication by solving the problem that a conventional antenna device is disabled to sufficiently suppress leakage radio waves that are radiated along with a substrate with an antenna mounted thereon or a surface of a casing surrounding the antenna. <P>SOLUTION: The antenna device including a planar antenna on a substrate comprises a distribution constant type leakage prevention structure around the antenna. In this antenna device, a projecting wire or a recessed wire formed from a conductive body is set to a predetermined width or height as an example of the distribution constant type leakage prevention structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an antenna device for a radio transceiver that can suppress leaked radio waves. In particular, the present invention relates to a radar antenna apparatus that requires sharp directivity for transmission and reception.

  The transmission wave radiated from the antenna device generally includes a main rope with the strongest radiated power, a side rope that appears beside the main rope, and a leaked radio wave that propagates from the antenna to the housing of the antenna device. This leaked radio wave becomes unnecessary radiation for the antenna. If the radiation power of unnecessary radiation is strong, if it is a radar, it will cause reflections from other than the target reflector. In addition, the radiated power is divided into leaked radio waves, and the ratio of the radiated power of the main rope is reduced.

  In the field of radar and wireless communication, an antenna device with sharp directivity is required to concentrate radiated power. In order to prevent leaking radio waves from being emitted in unnecessary directions, there is a method of absorbing leaked radio waves by attaching a radio wave absorber to the surface of the housing. FIG. 1 shows an example in which a radio wave absorber is attached to an antenna device. 1A is a front view of the antenna device, and FIG. 1B is a cross-sectional view taken along line D-D ′ in FIG.

  In FIG. 1, 21 is an antenna, 22 is a substrate, 23 is a housing, 51 is a leaked radio wave, 60 is a conventional antenna device, and 61 is a radio wave absorber. The antenna 21 provided on the substrate 22 is supported by a housing 23. When the antenna 21 is a transmission antenna, the main rope spreads in a direction perpendicular to the surface of the antenna 21, and at the same time, a leaked radio wave 51 is radiated along the surface of the housing 23.

  FIG. 2 shows a radiation pattern viewed from the horizontal direction with respect to the surface of the antenna. In FIG. 2, 51 is a leaked radio wave, 52 is a main rope pattern, 53 is a side rope pattern, and 60 is a conventional antenna device. As shown in FIG. 2, the main rope 52 spreads in the direction perpendicular to the antenna surface of the antenna device 60, and the side rope 53 spreads beside it. The leaked radio wave 51 is radiated almost horizontally on the antenna surface. If the ratio of the leaked radio wave 51 with respect to the main rope 52 becomes large, for example, if it is a radar antenna, it will measure other than the object.

  Therefore, in order to absorb the leaked radio wave, the radio wave absorber 61 is pasted on the casing 23 around the antenna 21 as shown in FIG. When the leaked radio wave 51 from the antenna 21 is radiated in the plane direction of the antenna 21, the radio wave absorber 60 absorbs the leaked radio wave 51, and the ratio of the radiation radiated outside the antenna device 60 is suppressed. However, in this method, the size of the antenna device 60 is increased by attaching the radio wave absorber 61. Moreover, since the magnetic permeability of the ferrite used as a radio wave absorber changes with temperature, the absorption rate also changes accordingly.

  As an antenna device that sharpens directivity, a planar antenna device that reduces the level of unnecessary radiation such as a side rope is known (see, for example, Patent Document 1). This planar antenna device reduces the level of unnecessary radiation by appropriately setting the positional relationship between a radiation circuit board provided with a plurality of slots and a plurality of corresponding power supply probes provided on the power supply circuit board. .

  In such a configuration, since the antenna and its periphery have a laminated structure, a fine assembly process is required for manufacturing. That is, it is necessary to drill a plurality of slots in the radiation circuit board and precisely align the radiation circuit board and the power supply circuit board.

Furthermore, unnecessary radiation from the antenna device is radiated not only from the antenna body but also through the substrate to which the antenna is attached, the substrate surrounding the antenna, the surface of the housing, or the like. With such a configuration, there is no reduction effect on the leaked radio waves radiated along the substrate and the housing surface.
JP-A-6-61735

  In the conventional antenna device, the leaked radio wave radiated through the surface of the substrate to which the antenna is attached or the casing surrounding the antenna cannot be sufficiently suppressed. Therefore, an object of the present invention is to suppress the emission of leaked radio waves in an antenna device used for radar and wireless communication.

  In order to achieve such an object, the present invention is an antenna device having a planar antenna on a substrate, and is provided with a distributed constant leakage prevention structure around the antenna. By providing the distributed constant type leakage prevention structure, it is possible to suppress leaked radio waves. The invention of the present application capable of suppressing leaked radio waves includes an invention of an antenna device having the following distributed constant type leakage prevention structure.

  In the present invention, the distributed constant type leakage prevention structure is at least one ridge formed of a conductor around the antenna, and the width of the ridge is a center wavelength λ of a radio wave used in the antenna. Is substantially (n−3 / 4) λ (where n is a positive integer).

  In the present invention, the distributed constant leakage prevention structure is at least one ridge formed of a conductor around the antenna, and the height of the ridge is the center wavelength of the radio wave used in the antenna. It is also included that it is approximately (n−3 / 4) λ with respect to λ (where n is a positive integer).

  In the present invention, the distributed constant type leakage preventing structure is at least one concave line formed of a conductor around the antenna, and the width of the concave line is a center wavelength λ of a radio wave used in the antenna. Is substantially (n−3 / 4) λ (where n is a positive integer).

  In the present invention, the distributed constant type leakage prevention structure is at least one concave strip formed of a conductor around the antenna, and the depth of the concave strip is the center wavelength of the radio wave used in the antenna. It is also included that it is approximately (n−3 / 4) λ with respect to λ (where n is a positive integer).

  In the invention of the present application, the distributed constant type leakage prevention structure is a plurality of concavo-convex ridges formed of a conductor around the antenna, and the width of either the ridges or ridges of the concavo-convex ridges is the antenna. It is also included that it is approximately (n−3 / 4) λ with respect to the center wavelength λ of the radio wave used in (where n is a positive integer).

  In the present invention, the distributed constant type leakage prevention structure is a plurality of uneven ridges formed of a conductor around the antenna, and the height difference between the ridges and ridges of the uneven ridges is the antenna. It also includes being approximately (n−3 / 4) λ with respect to the center wavelength λ of the radio wave used (where n is a positive integer).

  In the invention of the present application, the distributed constant type leakage prevention structure is a plurality of concavo-convex ridges formed of a conductor around the antenna, and the width of either the ridges or ridges of the concavo-convex ridges is the antenna. The logarithmic period distribution is included in a range including (n−3 / 4) λ with respect to the center wavelength λ of the radio wave used in (where n is a positive integer).

  In the present invention, the distributed constant type leakage prevention structure is a plurality of uneven ridges formed of a conductor around the antenna, and the height difference between the ridges and ridges of the uneven ridges is the antenna. It also includes a logarithmic period distribution in a range including (n−3 / 4) λ with respect to the center wavelength λ of the radio wave used (where n is a positive integer).

  The present invention includes that the antenna is a transmitting antenna.

  The present invention includes that the antenna is a receiving antenna.

  The antenna device of the present invention suppresses leakage radio waves radiated along the surface of the substrate on which the antenna is attached or the casing surrounding the antenna in the transmitting antenna, and further on the main rope and side rope. Transmission power can be concentrated. In the reception antenna, unnecessary radio waves incident through the surface of the substrate on which the antenna is attached or the housing surrounding the antenna can be suppressed.

(Embodiment 1)
The present embodiment is an antenna device having a planar antenna on a substrate, and is provided with a distributed constant leakage prevention structure around the antenna. Specifically, the distributed constant type leakage prevention structure is at least one ridge formed of a conductor around the antenna, and the width or height of the ridge is the center of the radio wave used in the antenna. The antenna device is set to approximately (n−3 / 4) λ with respect to the wavelength λ.

  The configuration of the antenna device is shown in FIG. FIG. 3A is a front view of the antenna device, and FIG. 3B is a cross-sectional view taken along line A-A ′ in FIG. 3 (1) and 3 (2), 10 is an antenna device of the present invention, 21 is an antenna, 22 is a substrate, 23 is a housing, 31 is a ridge, and 51 is a leaked radio wave. The antenna 21 is a planar antenna and is formed on the substrate 22. The periphery of the substrate 22 is protected by a housing 23. The housing 23 may be structured to cover up to the back surface of the substrate 22, and the material may be a conductor or a dielectric. The leaked radio wave 51 propagates from the antenna 21 through the surface of the substrate 22 and the surface of the housing 23.

  In the present embodiment, the ridges 31 are formed on the surface of the housing 23, but are not limited to the surface of the housing 23, and may be disposed around the antenna 21. The ridges 31 in FIG. 3 are continuous so as to surround the periphery of the antenna 21, but need not be continuous in the longitudinal direction of the ridges, and may be disposed so as to surround the antenna 21. The shape surrounding the antenna 21 of the ridge 31 is not limited to a square as shown in FIG. The material of the ridges 31 must be a conductor. For example, a metal is preferable. When the material of the housing 23 is a metal, the same material may be used. Alternatively, the surface of the dielectric may be coated with conductive plating, a film, paint, or the like. The thickness of the coating is preferably greater than or equal to the skin depth for the radio wave used in the antenna 21. Moreover, although it is set as one protruding item | line in FIG. 3, it is good also as a several protruding item | line. In this case, the plurality of protruding conductors need not be electrically connected.

Here, the skin depth δ (m) is given by the following equation.
δ = (1 / 2π) (ρ / f) ^1/2 (1)
In the equation (1), ρ is resistance (Ωm), and f is the center frequency (Hz) of the radio wave used in the antenna 21.

  FIG. 4 shows an example of the cross section of the ridge. FIG. 4 is an enlarged view of the ridge portion in FIG. In FIG. 4, 31 is a ridge, and λ is the center wavelength of the radio wave used in the antenna. As shown in FIG. 4, the width of the ridges 31 is set to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21. If it sets to such a width | variety, the interruption | blocking characteristic will be exhibited with respect to the leaked electromagnetic wave which crosses the protruding item | line 31. That is, since the phase of the radio wave used in the antenna 21 is reversed due to reflection in the width direction of the ridge 31, the leaked radio wave that travels and the leaked radio wave that is reflected cancel each other out. Shut off.

  The width of the ridge 31 is not limited to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21, and may be approximately (n−3 / 4) λ. However, n is a positive integer. FIG. 4 shows an example in which n = 1, but if n is a positive integer, the characteristic of blocking leaked radio waves is exhibited. The height of the ridge 31 may be arbitrary as long as it is equal to or higher than the skin depth represented by the formula (1) with respect to the frequency of the radio wave used in the antenna. When forming a some protruding item | line, each width | variety may differ.

  FIG. 5 shows another example of the cross section of the ridge. In FIG. 5, 31 is a protrusion, and λ is the center wavelength of the radio wave used in the antenna. As shown in FIG. 5, the height of the ridges 31 is set to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21. When set to such a height, a blocking characteristic is exhibited against leakage radio waves in the height direction of the ridges 31. That is, since the phase is inverted due to reflection in the height direction of the ridge 31 with respect to the wavelength of the radio wave used by the antenna 21, the traveling leaked radio wave and the reflected leaked radio wave cancel each other. Block radio waves.

  The height of the ridges 31 is not limited to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21, but may be approximately (n−3 / 4) λ. However, n is a positive integer. FIG. 5 shows an example in which n = 1, but if n is a positive integer, the characteristic of blocking leaked radio waves is exhibited. Further, when not only the height of the ridge 31 but also the width is set to substantially (n−3 / 4) λ at the same time, the blocking characteristic is further improved. When forming a some protruding item | line, each height may differ.

  4 or 5 is formed of a conductor around the antenna, and if the antenna is a receiving antenna, unnecessary radio waves from the lateral direction with respect to the front of the receiving antenna can be suppressed. Can do. If the antenna is a transmission antenna, unnecessary radiation can be suppressed, and further, transmission power to the main rope and the side rope can be increased by suppressing unnecessary radiation.

  3 has only one antenna on the substrate, it may be an antenna device having two antennas, a transmitting antenna and a receiving antenna, on the substrate. In the case of having two antennas, a common ridge formed of a conductor may be provided around the two antennas, or a ridge formed of a conductor may be provided around each antenna. Providing protrusions formed of a conductor around each antenna is effective in securing isolation between the transmitting antenna and the receiving antenna.

(Embodiment 2)
The present embodiment is an antenna device having a planar antenna on a substrate, and is provided with a distributed constant leakage prevention structure around the antenna. Specifically, the distributed constant type leakage prevention structure is at least one groove formed of a conductor around the antenna, and the width or depth of the groove is the center of the radio wave used by the antenna. The antenna device is set to approximately (n−3 / 4) λ with respect to the wavelength λ.

  The configuration of the antenna device is shown in FIG. 6A is a front view of the antenna device, and FIG. 6B is a cross-sectional view taken along line B-B ′ in FIG. 6 (1) and 6 (2), 10 is an antenna device of the present invention, 21 is an antenna, 22 is a substrate, 23 is a housing, 33 is a recess, and 51 is a leaked radio wave. The antenna 21 is a planar antenna and is formed on the substrate 22. The periphery of the substrate 22 is protected by a housing 23. The housing 23 may be structured to cover up to the back surface of the substrate 22, and the material may be a conductor or a dielectric. The leaked radio wave 51 propagates from the antenna 21 through the surface of the substrate 22 and the surface of the housing 23.

  In the present embodiment, the recess 33 is formed on the surface of the housing 23, but is not limited to the surface of the housing 23, and may be disposed around the antenna 21. 6 is continuous so as to surround the periphery of the antenna 21, but does not need to be continuous in the longitudinal direction of the recess, and may be disposed so as to surround the antenna 21. The shape surrounding the antenna 21 of the recess 33 is not limited to a square as shown in FIG. The material of the recess 33 must be a conductor. For example, a metal is preferable. When the material of the housing 23 is a metal, the same material may be used. Alternatively, the dielectric surface may be coated with a conductor such as plating. However, the thickness of the coating is preferably greater than or equal to the skin depth represented by the formula (1) with respect to the radio wave used in the antenna 21. Moreover, although it is set as one concave strip in FIG. 6, it is good also as a several concave strip. In this case, the plurality of concave conductors need not be electrically connected.

  FIG. 7 shows an example of the cross section of the concave stripe. FIG. 7 is an enlarged view of the concave stripe portion in FIG. In FIG. 7, 33 is a concave stripe, and λ is the center wavelength of the radio wave used in the antenna. As shown in FIG. 7, the width of the concave stripe 33 is set to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21. When such a width is set, a blocking characteristic is exhibited with respect to a leaked radio wave traversing the concave stripe 33. That is, since the phase of the radio wave used by the antenna 21 is reversed due to reflection in the width direction of the groove 33, the leaked radio wave that travels and the leaked radio wave that is reflected cancel each other out. Shut off.

  The width of the concave stripe 33 is not limited to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21 and may be approximately (n−3 / 4) λ. However, n is a positive integer. FIG. 7 shows an example where n = 1, but if n is a positive integer, the characteristic of blocking leaked radio waves is exhibited. When forming a plurality of concave stripes, the respective widths may be different.

  FIG. 8 shows another example of the cross section of the groove. In FIG. 8, 33 is a groove, and λ is the center wavelength of the radio wave used in the antenna. As shown in FIG. 8, the depth of the concave stripe 33 is set to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21. When the depth is set to such a depth, a blocking characteristic is exhibited with respect to leaked radio waves in the depth direction of the concave stripes 33. That is, since the phase of the radio wave used by the antenna 21 is inverted due to reflection in the depth direction of the groove 33, the leaked radio wave that travels and the leaked radio wave that is reflected cancel each other. Block radio waves.

  The depth of the concave stripe 33 is not limited to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21, but may be approximately (n−3 / 4) λ. However, n is a positive integer. FIG. 8 shows an example in which n = 1, but if n is a positive integer, the characteristic of blocking leaked radio waves is exhibited. Moreover, not only the depth of the recess 33 but also the width is set to substantially (n−3 / 4) λ at the same time, the blocking characteristic is further improved. When forming a plurality of concave stripes, each depth may be different.

  If a concave strip as shown in FIG. 7 or FIG. 8 is formed of a conductor around the antenna, if the antenna is a receiving antenna, it suppresses unwanted radio waves from the side of the front of the receiving antenna. Can do. If the antenna is a transmission antenna, unnecessary radiation can be suppressed, and further, transmission power to the main rope and the side rope can be increased by suppressing unnecessary radiation.

  6 has only one antenna on the substrate, it may be an antenna device having two antennas, a transmitting antenna and a receiving antenna, on the substrate. When two antennas are provided, a common groove formed of a conductor around the two antennas may be provided, or a groove formed of a conductor may be provided around each antenna. Providing recesses formed of a conductor around each antenna is effective in securing isolation between the transmitting antenna and the receiving antenna.

(Embodiment 3)
The present embodiment is an antenna device having a planar antenna on a substrate, and is provided with a distributed constant leakage prevention structure around the antenna. Specifically, the distributed constant type leakage prevention structure is a plurality of concavo-convex ridges formed of a conductor around the antenna, and the width or ridge of either the ridges or ridges of the ridges or ridges. In the antenna device, the height difference from the concave stripe is set to approximately (n−3 / 4) λ with respect to the center wavelength λ of the radio wave used in the antenna.

  The configuration of the antenna device is shown in FIG. FIG. 9A is a front view of the antenna device, and FIG. 9B is a cross-sectional view taken along line C-C ′ in FIG. 9 (1) and 9 (2), 10 is an antenna device according to the present invention, 21 is an antenna, 22 is a substrate, 23 is a housing, 35 is an uneven strip, and 51 is a leaked radio wave. The antenna 21 is a planar antenna and is formed on the substrate 22. The periphery of the substrate 22 is protected by a housing 23. The housing 23 may be structured to cover up to the back surface of the substrate 22, and the material may be a conductor or a dielectric. The leaked radio wave 51 propagates from the antenna 21 through the surface of the substrate 22 and the surface of the housing 23.

  In the present embodiment, the projections and recesses 35 are formed on the surface of the housing 23, but are not limited to the surface of the housing 23 and may be disposed around the antenna 21. 9 is continuous so as to surround the periphery of the antenna 21, but does not have to be continuous in the longitudinal direction of the uneven strip, and may be disposed so as to surround the antenna 21. The shape surrounding the antenna 21 of the uneven stripe 35 is not limited to a square as shown in FIG. 9, and may be a circle. The material of the projections and depressions 35 must be a conductor. For example, a metal is preferable. When the material of the housing 23 is a metal, the same material may be used. Alternatively, the dielectric surface may be coated with a conductor such as plating. However, the thickness of the coating is preferably greater than or equal to the skin depth represented by the formula (1) with respect to the radio wave used in the antenna 21. Further, in FIG. 9, three sets of concavo-convex ridges are provided, but the number of concavo-convex ridges is not limited to three.

  FIG. 10 shows an example of the cross section of the ridges. FIG. 10 is an enlarged view of the uneven stripe portion in FIG. In FIG. 10, 35 is a concave and convex strip, 36 is a concave strip of the concave and convex strip 35, 37 is a convex strip of the concave and convex strip 35, and λ is the center wavelength of the radio wave used in the antenna. As shown in FIG. 10, the width of the concave stripes and the convex stripes of the concave and convex stripes 35 is set to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21. When such a width is set, a blocking characteristic is exhibited with respect to a leaked radio wave traversing the ridges 35. That is, since the phase of the radio wave used in the antenna 21 is reversed due to reflection in the width direction of the ridges 35, the leaked radio wave that travels and the leaked radio wave that is reflected cancel each other out. Shut off.

  The width of the projections and recesses 35 is not limited to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21 and may be approximately (n−3 / 4) λ. However, n is a positive integer. FIG. 10 shows an example in which n = 1, but if n is a positive integer, the characteristic of blocking leaked radio waves is exhibited. Further, the width of the ridges and the width of the ridges may be different. Either one of the widths may be approximately (n−3 / 4) λ. The height difference between the concave stripe and the convex stripe may be arbitrary as long as it is equal to or higher than the skin depth expressed by the expression (1) with respect to the frequency of the radio wave used in the antenna.

  FIG. 11 shows another example of the cross-section of the uneven strip. In FIG. 11, 35 is a concave and convex strip, 36 is a concave strip of the concave and convex strip 35, 37 is a convex strip of the concave and convex strip 35, and λ is the center wavelength of the radio wave used in the antenna. As shown in FIG. 11, the height difference between the ridges 36 and the ridges 37 of the concavo-convex ridge 35 is set to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21. When such a height difference is set, a blocking characteristic is exhibited with respect to leaking radio waves in the height direction of the ridges 35. That is, since the phase of the radio wave used by the antenna 21 is inverted due to reflection in the height direction of the projections and recesses 35, the leaked radio wave that travels and the leaked radio wave that is reflected cancel each other. Block radio waves.

  The height difference of the concavo-convex strip 35 is not limited to approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21, but may be approximately (n−3 / 4) λ. However, n is a positive integer. FIG. 11 shows an example of n = 1, but if n is a positive integer, the characteristic of blocking leaked radio waves is exhibited. Moreover, not only the height difference of the ridges but also the width of the ridges or ridges is set to approximately (n−3 / 4) λ at the same time, the blocking characteristics are further improved.

  When the concave and convex strips as shown in FIG. 10 or FIG. 11 are formed of a conductor around the antenna, if the antenna is a receiving antenna, unnecessary radio waves from the lateral direction with respect to the front of the receiving antenna are further attenuated. be able to. If the antenna is a transmitting antenna, unnecessary radiation can be further suppressed, and further, transmission power to the main rope and side rope can be further increased by suppressing unnecessary radiation.

  9 has only one antenna on the substrate, it may be an antenna device having two antennas, a transmitting antenna and a receiving antenna, on the substrate. When two antennas are provided, a common uneven strip formed of a conductor may be provided around the two antennas, or an uneven strip formed of a conductor may be provided around each antenna. Providing an uneven strip formed of a conductor around each antenna is effective in securing isolation between the transmitting antenna and the receiving antenna.

(Embodiment 4)
The present embodiment is an antenna device having a planar antenna on a substrate, and is provided with a distributed constant leakage prevention structure around the antenna. Specifically, the distributed constant type leakage prevention structure is a plurality of concavo-convex ridges formed of a conductor around the antenna, and the width or ridge of either the ridges or ridges of the ridges or ridges. The antenna device has a logarithmic period distribution in a range in which the height difference from the concave stripe includes (n−3 / 4) λ with respect to the center wavelength λ of the radio wave used in the antenna.

  The configuration of the antenna device of the present embodiment is the same as that of the third embodiment. The difference is that either the width of the ridges or ridges of the ridges or the height difference between the ridges and the ridges has a logarithmic period distribution.

FIG. 12 shows an example of the cross-section of the uneven stripe. FIG. 12 is an enlarged view of the ridge portion in FIG. In FIG. 12, reference numeral 38 denotes a concave and convex strip, 36 denotes a concave strip of the concave and convex strip 38, 37 denotes a convex strip of the concave and convex strip 38, and λ denotes a center wavelength of a radio wave used in the antenna. As shown in FIG. 12, the width of the concave and convex strips of the concave and convex strip 38 is set such that the width of the concave and convex strips adjacent to the center wavelength of the radio wave used in the antenna 21 is a quarter wavelength. It is set to change by ^Sa times. When the width of such distribution is set, a blocking characteristic is exhibited with respect to a leaked radio wave that traverses the uneven stripe 35. That is, when the radio wave used by the antenna is pulse-modulated, a wide sideband is generated around the center frequency of the radio wave. Therefore, the cutoff characteristic can be improved by blocking not only the center frequency but also the sideband component of the leaked radio wave. The leaked radio wave having such a spectrum is a radio wave whose phase is inverted by reflection in the width direction of the ridges and valleys 38, so that the leaked radio wave that travels and the leaked radio wave that is reflected cancel each other out. Cut off.

  The width of the projections and depressions 38 is not limited to a width having a logarithmic period distribution centered on approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21, and is a logarithm centered on approximately (n−3 / 4) λ. Any device having a period distribution may be used. However, n is a positive integer. Here, an example of n = 1 is shown, but if n is a positive integer, the characteristic of blocking leaked radio waves is exhibited. Further, the width of the ridges and the width of the ridges may be different. Any one of them may have a logarithmic period distribution centered around (n−3 / 4) λ. Further, the width of the projections and recesses 38 includes a quarter wavelength of the center wavelength of the radio wave used in the antenna 21 even if it is not centered on approximately a quarter wavelength of the center wavelength of the radio wave used in the antenna 21. Any logarithmic period distribution may be used. The height difference between the concave stripes and the convex stripes may be arbitrary as long as it is equal to or higher than the skin depth represented by the formula (1) with respect to the frequency of the radio wave used in the antenna.

FIG. 13 shows another example of the cross section of the ridges. In FIG. 13, reference numeral 38 denotes a concave and convex stripe, 36 denotes a concave and convex stripe 8, 37 denotes a convex stripe of the concave and convex stripe 38, and λ denotes a center wavelength of a radio wave used in the antenna. As shown in FIG. 13, the height difference between the concave stripes 36 and the convex stripes 37 of the concave and convex stripes 38 is determined based on the concave stripes and the convex stripes that are adjacent to each other around the center wavelength of the center wavelength of the radio wave used in the antenna 21. It is set so that the difference in height from the height changes by ^Ta times. When the height difference of the distribution is set as described above, a blocking characteristic is exhibited with respect to leaked radio waves in the height direction of the uneven stripes 38. That is, when the radio wave used by the antenna is pulse-modulated, a wide sideband is generated around the center frequency of the radio wave. Therefore, the cutoff characteristic can be improved by blocking not only the center frequency but also the sideband component of the leaked radio wave. The leaked radio wave having such a spectrum is a radio wave whose phase is inverted by reflection in the height direction of the projections and recesses 38, so that the leaked radio wave traveling and the reflected leaked radio wave cancel each other. Shut off.

  The height difference of the uneven stripe 38 is not limited to the height difference distributed in a logarithmic cycle centered on approximately one quarter wavelength of the center wavelength of the radio wave used in the antenna 21, but centered on approximately (n-3 / 4) λ. Any distribution having a logarithmic period may be used. However, n is a positive integer. FIG. 13 shows an example of n = 1, but if n is a positive integer, it exhibits the characteristic of blocking leaked radio waves. Further, not only the height difference of the ridges but also the widths of the ridges or ridges are set so as to be distributed in a logarithmic cycle centered at about (n−3 / 4) λ, thereby further improving the blocking characteristics.

  When a plurality of concave and convex strips as shown in FIG. 12 or FIG. 13 are formed of a conductor around the antenna, if the antenna is a receiving antenna, a wide frequency range from the lateral direction to the front of the receiving antenna. Can attenuate unwanted radio waves. If the antenna is a transmitting antenna, unnecessary radiation can be suppressed in a wide frequency range, and transmission power to the main rope and side rope can be increased by suppressing unnecessary radiation.

  The antenna device of the present invention can be applied not only to radar but also to an antenna for wireless communication.

FIG. 1A is a front view of a conventional antenna device. FIG. 1B is a cross-sectional view taken along line D-D ′ in FIG. It is a figure which shows the radiation pattern seen from the horizontal direction with respect to the surface of an antenna. FIG. 3A is a front view of the antenna device of the present invention. FIG. 3B is a cross-sectional view taken along line A-A ′ in FIG. It is an enlarged view of the protruding item | line part in FIG. 3 (2). It is an enlarged view of the protruding item | line part in FIG. 3 (2). FIG. 6A is a front view of the antenna device of the present invention. FIG. 6B is a cross-sectional view taken along line B-B ′ in FIG. It is an enlarged view of the groove part in FIG. 6 (2). It is an enlarged view of the groove part in FIG. 6 (2). FIG. 9A is a front view of the antenna device of the present invention. FIG. 9B is a cross-sectional view taken along line C-C ′ in FIG. It is an enlarged view of the uneven | corrugated strip part in FIG.9 (2). It is an enlarged view of the uneven | corrugated strip part in FIG.9 (2). It is an enlarged view of the uneven | corrugated strip part in FIG.9 (2). It is an enlarged view of the uneven | corrugated strip part in FIG.9 (2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Antenna apparatus 21 of this invention Antenna 22 Board | substrate 23 Case 31 Convex line 33 Concave line 35 Concave line 51 Leaked electric wave 52 Main rope pattern 53 Side rope pattern 60 Conventional antenna apparatus 61 Wave absorber

Claims (11)

  An antenna device having a planar antenna on a substrate, the antenna device comprising a distributed constant leakage prevention structure around the antenna.   The distributed constant type leakage preventing structure is at least one ridge formed of a conductor around the antenna, and the width of the ridge is substantially equal to a center wavelength λ of a radio wave used in the antenna ( 2. The antenna device according to claim 1, wherein n-3 / 4) [lambda] (where n is a positive integer).   The distributed constant type leakage prevention structure is at least one ridge formed of a conductor around the antenna, and the height of the ridge is approximately the center wavelength λ of a radio wave used in the antenna. 2. The antenna device according to claim 1, wherein (n−3 / 4) λ (where n is a positive integer).   The distributed constant type leakage preventing structure is at least one groove formed of a conductor around the antenna, and the width of the groove is substantially equal to a center wavelength λ of a radio wave used in the antenna ( 2. The antenna device according to claim 1, wherein n-3 / 4) [lambda] (where n is a positive integer).   The distributed constant type leakage preventing structure is at least one concave strip formed of a conductor around the antenna, and the depth of the concave strip is approximately the center wavelength λ of the radio wave used in the antenna. 2. The antenna device according to claim 1, wherein (n−3 / 4) λ (where n is a positive integer).   The distributed constant type leakage prevention structure is a plurality of concave and convex strips formed of a conductor around the antenna, and the width of either the convex strips or the concave strips of the concave and convex strips of radio waves used in the antenna 2. The antenna device according to claim 1, wherein the antenna device is approximately (n−3 / 4) λ with respect to the center wavelength λ (where n is a positive integer).   The distributed constant type leakage prevention structure is a plurality of concave and convex strips formed of a conductor around the antenna, and the height difference between the convex strips and the concave strips of the concave and convex strips is the center of the radio wave used in the antenna. The antenna device according to claim 1, wherein the antenna device is approximately (n-3 / 4) λ with respect to the wavelength λ (where n is a positive integer).   The distributed constant type leakage prevention structure is a plurality of concave and convex strips formed of a conductor around the antenna, and the width of either the convex strips or the concave strips of the concave and convex strips of radio waves used in the antenna 2. The antenna device according to claim 1, wherein a logarithmic period is distributed in a range including (n−3 / 4) λ with respect to the center wavelength λ (where n is a positive integer).   The distributed constant type leakage prevention structure is a plurality of concave and convex strips formed of a conductor around the antenna, and the height difference between the convex strips and the concave strips of the concave and convex strips is the center of the radio wave used in the antenna. 2. The antenna device according to claim 1, wherein logarithmic periods are distributed in a range including (n−3 / 4) λ with respect to the wavelength λ (where n is a positive integer).   The antenna apparatus according to claim 1, wherein the antenna is a transmitting antenna.   The antenna device according to claim 1, wherein the antenna is a receiving antenna.

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