JP4439423B2 - antenna - Google Patents

Description

  The present invention relates to an antenna used for communication and radar using microwaves and millimeter waves, and relates to an antenna having a wide band and capable of being thinned.

  A horn antenna using a waveguide is known as an antenna that efficiently radiates electromagnetic waves such as microwaves and millimeter waves. A horn antenna is an antenna that radiates a high-frequency signal transmitted through a waveguide into space. The inside of the waveguide has the same dielectric constant as that of space (generally, the dielectric constant of air), and its impedance is close to that of space. The electromagnetic field mode of the high-frequency signal transmitted through the waveguide is similar to the electromagnetic field mode of the high-frequency signal transmitted through the space. The electromagnetic field mode of the high-frequency signal transmitted through the waveguide can be easily It can change to the electromagnetic field mode of the high-frequency signal to be transmitted. For these reasons, it is known that the horn antenna has low reflection due to impedance and mode mismatch, and is highly efficient and relatively wide in bandwidth.

  On the other hand, circuits generally used for communication and radar using microwaves and millimeter waves are planar circuits using microstrip lines and coplanar lines. In this case, in order to connect the circuit and the horn antenna, a converter for converting the planar circuit into the waveguide is required, and the use of the converter may cause an increase in cost and performance degradation such as reflection.

  Also, a patch antenna is known as one of antennas that directly radiate electromagnetic waves from a planar circuit to space. In the patch antenna, a planar circuit having a relatively small impedance and a space having a relatively large impedance are matched using the resonance of the patch.

  In such matching by resonance, the impedance of the resonator affects the band. In order to increase the impedance of the patch in order to widen the band, it is necessary to reduce the patch width, and the radiation efficiency decreases. Increasing the patch width to increase the radiation efficiency tends to reduce the patch impedance and narrow the band. In the design of a patch antenna, the first condition is to efficiently radiate a high-frequency signal into the space. Therefore, the band is often narrowed at the expense of the band.

In order to solve this problem, a laminated aperture antenna using a cavity resonator having a large impedance as a resonator has been proposed. In this laminated aperture antenna, a cavity resonator in which a dielectric is filled inside a dielectric substrate forming a planar circuit is configured to realize a broadband antenna.
JP 2001-016027 A

  However, the laminated aperture antenna has a problem that the cavity substrate needs to be formed inside the dielectric substrate, so that the dielectric substrate becomes thicker than the patch antenna. In particular, when a feed line such as a laminated waveguide or a microstrip line is used to feed the slot which is the primary radiator of this antenna, a dielectric layer is further provided on the slot to form the feed line. Therefore, there is a problem that the thickness of the dielectric substrate is further thicker than the thickness of the cavity resonator and the size of the device is increased.

  Therefore, the present invention has been completed in view of the above-described conventional problems, and the object of the present invention is to form a feeder line without increasing the thickness of the dielectric substrate in a broadband antenna, and the radiation efficiency is improved. An object of the present invention is to provide an antenna that is high and has a small variation in radiation characteristics.

The antenna of the present invention includes a line conductor formed on an upper surface of a dielectric layer, a high-frequency line including a coplanar grounding conductor layer formed so as to surround one end of the line conductor, and the coplanar grounding conductor layer including the high frequency line. It is formed so as to be perpendicular to the line conductor, the line and the slot having one end connected to the same plane ground conductor layer of the conductor, a plurality of shield conductors formed inside the dielectric layer so as to surround the slot The line conductor has a line width that is increased from a connection portion with the same-surface ground conductor layer to the one end portion in the slot, and the line conductor and the same-surface ground conductor layer apart, it is characterized in that it has narrowed in near the junction between the slot relative to the outer peripheral side of the dielectric layer.

The antenna of the present invention is preferably λ / 8 ≦ L ≦ λ / 4, where L is the length near the junction and λ is the effective wavelength of the high-frequency signal transmitted by the line conductor. It is characterized by this .

According to the antenna of the present invention, the line conductor formed on the upper surface of the dielectric layer and the high-frequency line composed of the same-surface ground conductor layer formed so as to surround one end of the line conductor, and the line on the same-surface ground conductor layer A slot formed so as to be orthogonal to the conductor and having one end of the line conductor connected to the same grounded conductor layer, and a plurality of shield conductors formed inside the dielectric layer so as to surround the slot Therefore, since the line conductor and the slot are electromagnetically coupled in the same plane, the feeder line can be configured without increasing the thickness of the dielectric substrate, and a thin antenna can be provided.

In addition, the line width of the line conductor is increased from the connection portion of the slot with the same-surface ground conductor layer to one end, and the distance between the line conductor and the same-surface ground conductor layer is larger than that of the outer periphery of the dielectric layer. Therefore, the vicinity of the junction acts as an impedance matching portion between the high-frequency line and the slot, and the difference in impedance between the high-frequency line and the slot can be reduced. Therefore, reflection loss between the high-frequency line and the slot can be suppressed, and the radiation efficiency of the antenna can be increased.

  In the antenna of the present invention, preferably, λ / 8 ≦ L ≦ λ / 4, where L is the length near the junction and λ is the effective wavelength of the high-frequency signal transmitted by the line conductor. In the frequency band of the transmitted high frequency signal, reflection loss between the high frequency line and the slot can be effectively suppressed, and the conversion efficiency of the antenna can be further increased.

  The antenna of the present invention will be described in detail with reference to the drawings. 1A and 1B are schematic views for explaining an example of the antenna of the present invention. FIG. 1A is a plan perspective view, and FIG. 1B is a cross-sectional view taken along line A-AA.

  In FIG. 1, 1 is a high-frequency line, 2 is a dielectric layer, 3 is a line conductor, 4 is a ground conductor layer on the same plane, 5 is a slot formed in the ground conductor layer 4 on the same plane, 6 is a shield conductor, and 8 is an interior. This is a ground conductor layer.

In the example of the antenna of the present invention, the dielectric layer 2, the line conductor 3 disposed on the upper surface of the dielectric layer 2, and the same surface so as to surround one end of the line conductor 3 (the upper surface of the dielectric layer 2) A coplanar line as the high-frequency line 1 is formed by the same-surface ground conductor layer 4 disposed on the surface. A slot 5 is formed in the same-surface ground conductor layer 4 on the upper surface of the dielectric layer 2 so as to be orthogonal to one end of the line conductor 3, and one end of the line conductor 3 is connected to the same-surface ground conductor layer 4. Is arranged and is electromagnetically coupled to one end of the high-frequency line 1. As a result, the high frequency signal transmitted to the high frequency line 1 is radiated as electromagnetic waves from the slot 5 to the lower surface side of the dielectric layer 2.

  The side surface direction of the dielectric layer 2 is shielded by a shield conductor 6 disposed inside the dielectric layer 2 as shown in the example of FIG. 1 so as to surround one end of the line conductor 3 and the slot 5. The electromagnetic wave radiated from the slot 5 to the dielectric layer 2 and the electromagnetic wave reflected at the boundary between the dielectric layer 2 and the external space are prevented from leaking, and the radiation efficiency is prevented from decreasing.

In addition, the high-frequency line 1 and the slot 5 are formed in the same plane, and as a result, the relative positional relationship between the two is less likely to vary, and the length of the stub that is the protruding portion of the high-frequency line 1 with respect to the slot 5 Therefore, the variation in electromagnetic coupling characteristics can be reduced, and the feeder line can be configured without increasing the thickness of the dielectric layer 2, thereby providing a thin antenna.

Furthermore, at a site located outside the slot 5 at one end of the line conductor 3, and thick line width of the line conductor 3 toward the one end portion from the connecting portion of the same plane ground conductor layer 4 in the slot 5, line conductors 3 is made narrower in the vicinity of the junction 7 with the slot 5 than the outer peripheral side of the dielectric layer 2, thereby providing an impedance matching portion between the high-frequency line 1 and the slot 5. it allows the reflection loss between the high-frequency line 1 and slot 5 can be suppressed, it is possible to enhance the radiation efficiency of the antenna.

  As a dielectric material for forming the dielectric layer 2, ceramic material mainly composed of aluminum oxide, aluminum nitride, silicon nitride, mullite, glass, or glass formed by firing a mixture of glass and ceramic filler Ceramic materials, epoxy resins, polyimide resins, organic resin materials such as fluorine resins such as tetrafluoroethylene resin, and organic resin-ceramic (including glass) composite materials are used.

  The conductor material for forming the shield conductor 6 composed of the line conductor 3, the same grounded conductor layer 4, the through conductor, etc. is metallized mainly composed of tungsten, molybdenum, gold, silver, copper, etc., or gold, silver, copper A metal foil or the like mainly composed of aluminum or the like is used.

  In particular, when the antenna is incorporated in a wiring board on which high-frequency components are mounted, it is desirable that the dielectric material forming the dielectric layer 2 has a small dielectric loss tangent and can be hermetically sealed. A particularly desirable dielectric material includes at least one inorganic material selected from the group of aluminum oxide, aluminum nitride, and glass ceramic material. Such a hard material is preferable in terms of improving the reliability of the mounted high-frequency component because the dielectric loss tangent is small and the mounted high-frequency component can be hermetically sealed. In this case, it is desirable to use a metallized conductor that can be fired simultaneously with the dielectric material as the conductor material in terms of hermetic sealing and productivity.

  The antenna of the present invention is manufactured as follows. For example, when an aluminum oxide sintered body is used as a dielectric material, first, an appropriate organic solvent or solvent is added to and mixed with raw material powders such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide to form a slurry. This is formed into a sheet shape by a conventionally known doctor blade method or calendar roll method to produce a ceramic green sheet. Further, a metallized paste is prepared by adding and mixing an appropriate organic solvent and solvent to a raw material powder such as a high melting point metal such as tungsten or molybdenum, aluminum oxide, silicon oxide, magnesium oxide, calcium oxide or the like.

  Next, a through hole for forming a through conductor as the shield conductor 6 is formed in the ceramic green sheet by, for example, a punching method, and a metallized paste is embedded in the through hole by, for example, a printing method. A metallized paste is printed in the shape of the same-surface grounded conductor layer 4 having the slots 5. When the dielectric layer 2 has a laminated structure of a plurality of dielectric layers, ceramic green sheets embedded and printed with these conductors are laminated, pressed and pressed, and fired at a high temperature (about 1600 ° C.). Furthermore, nickel plating and gold plating are applied to the surface of the conductor exposed on the surface of the line conductor 3, the same-surface ground conductor layer 4, and the like.

  The shield conductor 6 is disposed on the side surface or inside of the dielectric layer 2 so as to surround one end portion of the line conductor 3 and the slot 5, and is electrically connected to the same-surface ground conductor layer 4 and grounded.

  The shield conductor 6 may be composed of a plurality of shield through conductors arranged inside the dielectric layer 2. When the shield conductor 6 is formed of a plurality of shield through conductors in this way, the shape of the region surrounded by the shield conductor 6 of the dielectric layer 2 can be arbitrarily designed. For example, the shield conductor of the dielectric layer 2 When unnecessary resonance occurs in the region surrounded by 6, it is possible to adjust the arrangement of the shield conductor 6 to shift the unnecessary resonance out of the signal conversion band.

  The gap between the shield through conductors (indicated by G in FIG. 1) is preferably less than ¼ of the signal wavelength. This is because the electromagnetic wave is less likely to leak from the gap between the shielding through conductors by setting it to less than ¼ of the signal wavelength, so that the shielding effect can be enhanced.

  The shield through conductor constituting the shield conductor 6 may be a so-called through-hole conductor in which a conductor layer is attached to the inner wall of the through-hole, or a so-called via conductor in which the inside of the through-hole is filled with a conductor. There may be.

  Preferably, as shown in FIG. 1, an internal grounding conductor layer 8 is formed which overlaps with the slot 5 in a plan view through the inner layer of the dielectric layer 2 and has an opening that is the same as or larger than the slot 5. May be. Thereby, the ground potential of the line conductor 3 can be further strengthened, and the transmission property can be further improved.

  Further, as shown in FIG. 1, the antenna of the present invention preferably has a length of λ / when the length of the junction vicinity 7 is L and the effective wavelength of the high-frequency signal transmitted by the line conductor 3 is λ. It is preferable that 8 ≦ L ≦ λ / 4. Thereby, in the frequency band of the high frequency signal transmitted, the reflection loss between the high frequency line 1 and the slot 5 can be effectively suppressed, and the conversion efficiency of the antenna can be further increased.

If the length L of the junction vicinity 7 is less than λ / 8, it is difficult to function as an impedance matching portion between the high-frequency line 1 and the slot 5 because the length L is too short with respect to the wavelength. If the length L of the vicinity 7 of the junction exceeds λ / 4, the junction has frequency characteristics, and the conversion from the high-frequency line 1 to the slot 5 is likely to be hindered.

  Further, the gap between the vicinity 7 of the junction and the ground conductor layer 4 on the same plane is determined by the outer peripheral side of the dielectric layer 2 (the junction of the line conductor 3 at the portion located outside the slot 5 at one end of the line conductor 3 in FIG. It is preferable that it is 0.2 to 0.8 times the distance between the same-surface grounding conductor layer 4 and the portion other than the portion vicinity 7. If it is less than 0.2 times, the interval changes rapidly, thereby disturbing the propagation mode of the high-frequency signal and easily preventing the conversion from the high-frequency line 1 to the slot 5. On the other hand, if it exceeds 0.8 times, the change in the interval is small, so that it becomes difficult to function as an impedance matching unit.

  Preferably, one end of the line conductor 3 and the vicinity 7 of the joint of the slot 5 are formed so that the distance from the same-surface ground conductor layer 4 becomes narrower as the slot 5 is approached. As a result, the impedance between the high-frequency line 1 and the slot 5 can be gradually brought close, and a sudden change in impedance between the high-frequency line 1 and the slot 5 can be effectively suppressed.

  Examples of the antenna of the present invention will be described below.

  First, the line conductor 3 having a line width of 0.34 mm and the same surface contact so that the characteristic impedance is 50Ω as the high frequency line 1 is formed on the upper surface of the dielectric layer 2 having a relative dielectric constant of 8.6 and having a thickness of 1.52 mm. The ground conductor layer 4 was formed. Further, a slot 5 having a length in the line direction of the line conductor 3 of 0.1 mm and a length in the direction perpendicular to the line conductor 3 of 3.0 mm is formed in the ground conductor layer 4 so as to be orthogonal to the line conductor 3. .

Further, the line at the junction near near 7 between the conductor 3 and the slot 5, the impedance matching section line width is 0.45 mm (one end and the junction near 7 in slot 5 of the line conductor 3) the length L of the 0.68mm It formed so that it might become.

  Here, a high frequency three-dimensional structure simulator (HFSS manufactured by Ansoft) was used to design 24 GHz as a center frequency.

  As a result, the reflection loss S11 at 24 GHz was −20 dB or less, and it was confirmed that the reflection loss was sufficiently small as a practical antenna.

  Next, the reflection loss S11 when the length L of the impedance matching portion was changed in the range of 0.3 mm to 1.2 mm was simulated using a high-frequency three-dimensional structure simulator (HFSS manufactured by Ansoft).

  As a result, when the length of the impedance matching portion in the vicinity of the junction 7 is L and the effective wavelength of the high-frequency signal transmitted by the line conductor 3 is λ, 0.5 mm corresponding to λ / 8 ≦ L ≦ λ / 4. In the range of ˜1 mm, it was confirmed that a reflection loss S11 ≦ −10 dB and a reflection loss sufficiently practical as an antenna can be obtained.

  Note that the present invention is not limited to the above-described embodiments and examples, and various modifications may be made without departing from the scope of the present invention.

  For example, FIG. 1 shows an example in which the high-frequency line 1 has a coplanar line structure, but a dielectric layer is further laminated on the dielectric layer 2 so that the line conductor 3 is covered on the upper surface of the dielectric layer. A coplanar line structure with a ground provided with an upper surface ground conductor layer may be used, and in any case, the positional relationship among the dielectric layer 2, the line conductor 3, the coplanar ground conductor layer 4, the slot 5, and the shield conductor 6 is shown in FIG. The same effect can be obtained by performing the same as the example shown in FIG.

  1 shows an example in which the shield conductor 6 is a plurality of through conductors, the shield conductor 6 may be formed as a shield conductor by reducing the dielectric layer 2 and forming a conductor layer on the side surface.

(A) is a plane perspective view which shows an example of embodiment of the antenna of this invention, (b) is sectional drawing in the AA of the antenna of (a).

Explanation of symbols

1: High-frequency line 2: Dielectric layer 3: Line conductor 4: Coplanar ground conductor layer 5: Slot 6: Shield conductor 7: Near one end and slot junction

Claims (2)

A high-frequency line comprising a line conductor formed on the upper surface of the dielectric layer and a coplanar grounding conductor layer formed so as to surround one end of the line conductor, and the coplanar grounding conductor layer orthogonal to the line conductor an antenna that is formed comprises a slot having one end connected to the same plane ground conductor layer of said line conductors, and a plurality of shield conductors formed inside the dielectric layer so as to surround the slot The line conductor has a line width increased from a connection portion with the same-surface ground conductor layer to the one end portion in the slot, and an interval between the line conductor and the same-surface ground conductor layer is set to the dielectric. An antenna characterized in that it is narrower in the vicinity of the junction with the slot than on the outer peripheral side of the layer.   2. The length of the vicinity of the joint is L, and λ / 8 ≦ L ≦ λ / 4, where L is the effective wavelength of the high-frequency signal transmitted by the line conductor. Antenna.

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