JP4799238B2 - Aperture 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 aperture antenna that has a wide band and can be 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. A patch antenna is known as one of antennas that directly radiate electromagnetic waves from a planar circuit into 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 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, an aperture antenna using a cavity resonator having a large impedance as a resonator has been proposed. In this aperture antenna, a cavity resonator in which a dielectric is filled in a dielectric substrate forming a planar circuit is configured to realize a broadband antenna.
JP 2001-016027 A

  However, such a conventional aperture antenna has a problem in that resonance occurs on the radiation surface of the electromagnetic wave and radiation efficiency may be reduced. Further, the conventional aperture antenna has a problem that it is difficult to improve the radiation characteristics due to the influence of electronic components provided around the antenna on the radiation surface of the electromagnetic wave.

  Therefore, the present invention has been completed in view of the above-described conventional problems, and an object of the present invention is to provide an aperture antenna having high radiation efficiency and small variation in radiation characteristics. It is in.

An aperture antenna according to the present invention is formed on a dielectric layer having first and second surfaces, and the first surface of the dielectric layer, and includes a first that surrounds a line conductor and an end of the line conductor. A high-frequency line composed of a ground conductor layer, a slot formed in the first surface of the dielectric layer so as to intersect the line conductor, and formed in the dielectric layer. An internal grounding conductor layer having an opening facing it, and a second grounding conductor layer formed on the second surface of the dielectric layer and having an opening facing the slot, In the second ground conductor layer, a slit surrounding the opening of the second ground conductor layer is formed on the same plane as the opening in a state where the slit is exposed in a radiation space of a high-frequency signal radiated from the opening , The width of the slit is the opening of the second ground conductor layer. It is characterized in that it is 1/5 or more effective wavelength at the slit inside the high-frequency signal et radiation.

The aperture antenna of the present invention includes a second ground conductor layer formed on the second surface of the dielectric layer, and a slit surrounding the opening of the second ground conductor layer in the second ground conductor layer. Since the second ground conductor layer is separated and resonance in the second ground conductor layer affecting the radiation characteristics can be suppressed, radiation efficiency can be improved.

Also, by the inner region is separated from the slit of the second outside the slits of the ground conductor layer of the region and the second ground conductor layer, the slit than the inner region of the second ground conductor layer (openings Side region) is less susceptible to electromagnetic influences from the outside of the slit, and even when electronic components are arranged around the antenna, variations in the radiation characteristics of the antenna due to the surrounding electronic components can be reduced. .

  The aperture 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 an aperture antenna according to the present invention. FIG. 1A is a top view, and FIG. 1B is a cross-sectional view taken along line XX ′ of the configuration shown in FIG. (C) is a bottom view.

  The aperture antenna of the present invention includes a dielectric layer 1, a high-frequency line 2 and a slot 3 formed on the first surface (upper surface) 1 a of the dielectric layer 1, and an interior formed inside the dielectric layer 1. A ground conductor layer 4 and a second ground conductor layer (lower surface ground conductor layer) 5 formed on the second surface (lower surface) 1b of the dielectric layer 1 are provided.

  The dielectric layer 1 is made of a ceramic material mainly composed of aluminum oxide, aluminum nitride, silicon nitride, mullite, or the like, glass, or a glass ceramic material formed by firing a mixture of glass and ceramic filler, epoxy resin, polyimide It is made of a dielectric material such as a resin, an organic resin material such as a fluorine resin such as tetrafluoroethylene resin, and an organic resin-ceramic (including glass) composite material.

  In particular, when the aperture antenna is built in the wiring board, the dielectric material forming the dielectric layer 1 is preferably a dielectric material having a small dielectric loss tangent and capable of being hermetically sealed. Examples of such a dielectric material include at least one inorganic material selected from the group of aluminum oxide, aluminum nitride, and glass ceramic material. If the dielectric layer 1 is made of such a hard material, the dielectric loss tangent is small and the mounted high-frequency component can be hermetically sealed, so that the reliability of the mounted high-frequency component is improved. Can do.

  The high-frequency line 2 includes a line conductor 6 and a first ground conductor layer (coplanar ground conductor layer) 7 surrounding the end portion 6 a of the line conductor 6. In the embodiment shown in FIG. 1, the dielectric layer 1, the line conductor 6 disposed on the upper surface 1a of the dielectric layer 1, and the same surface (the upper surface 1a of the dielectric layer 1) of the line conductor 6 are disposed. A coplanar line is formed by the same grounded conductor layer 7 formed.

    The line conductor 6 is linearly formed between the end portion of the upper surface 1 a of the dielectric layer 1 and the central portion of the upper surface 1 a of the dielectric layer 1. The flush ground conductor layer 7 is formed on the upper surface 1a of the dielectric layer 1 with a predetermined gap so that the slot 3 is formed at the end 6a of the line conductor 6. The end 6a of the line conductor 6 and the same surface ground copper body layer 7 are short-circuited.

  The slot 3 is formed on the upper surface 1 a of the dielectric layer 1 so as to intersect the line conductor 6. In the embodiment shown in FIG. 1, the slot 3 is orthogonal to the line conductor 6. The slot 3 is electromagnetically coupled to the end 6a of the high frequency line 2. With this configuration, the high-frequency signal transmitted to the high-frequency line 2 is radiated as electromagnetic waves from the slot 3 to the lower surface 1 b side of the dielectric layer 1.

  The internal ground conductor layer 4 is formed inside the dielectric layer 1 and has an opening 4 a facing the slot 3. As shown in FIG. 1 (d), the opening 4 a of the internal ground conductor layer 4 is formed larger than the area of the slot 3. In the aperture antenna shown in FIG. 1, the internal ground conductor layer 4 has an aperture 4 a and is formed on the entire inner layer of the dielectric layer 1.

  The lower surface ground conductor layer 5 is formed on the lower surface 1 b of the dielectric layer 1 and has an opening 5 a facing the slot 3. As shown in FIG. 1C, the opening 5 a of the lower ground conductor layer 5 is formed larger than the area of the slot 3.

  The lower surface ground conductor layer 5 is formed with a slit 9 surrounding the opening 5a. In the aperture antenna shown in FIG. 1C, in the lower surface ground conductor layer 5, the inner region of the slit 9 and the outer region of the slit 9 are separated by the slit 9.

  In the aperture antenna according to the present invention, the lower surface ground conductor layer 5 is separated by such a configuration, so that resonance in the lower surface ground conductor layer 5 that affects the radiation characteristics can be reduced. Efficiency can be improved.

  Further, the aperture antenna of the present invention has a slit on the lower surface ground conductor layer 5 by separating the outer region from the slit 9 of the lower surface ground conductor layer 5 and the region inside the slit 9 of the lower surface ground conductor layer 5. Since the region inside 9 (the region on the opening 5a side) is less susceptible to electromagnetic influences from the outside of the slit 9, even when electronic components are arranged around the antenna, the radiation of the antenna by the surrounding electronic components Variations in characteristics can be reduced.

  In the embodiment shown in FIG. 1, a plurality of shield conductors 8 surrounding the region between the slot 3 and the opening 5 a of the lower surface ground conductor layer 5 are formed inside the dielectric layer 1. The plurality of shield conductors 8 are electrically connected to the same plane ground conductor layer 7 and are fixed to the ground potential.

  A shield conductor 8 is formed inside the dielectric layer 1 so as to surround the end portion 6a of the line conductor 6 and the slot 3, and a region between the slot 3 and the opening 5a of the lower surface ground conductor layer 5 is shielded. Thus, leakage of electromagnetic waves radiated from the slot 3 to the dielectric layer 1 and electromagnetic waves reflected at the boundary between the dielectric layer 1 and the external space can be reduced, and radiation efficiency can be improved. The shield conductor 8 is a plurality of shield through conductors or metal blocks.

  The plurality of shield conductors 8 may be constituted by a plurality of shield through conductors arranged inside the dielectric layer 1. When the shield conductor 8 is formed of a plurality of shield through conductors in this way, the shape of the region surrounded by the shield conductor 8 of the dielectric layer 1 can be arbitrarily designed. For example, the dielectric layer 1 When unnecessary resonance occurs in the region surrounded by the shield conductor 8, the arrangement of the shield conductor 8 can be adjusted to shift the unnecessary resonance out of the signal conversion band.

  The gap (indicated by G) between the shield through conductors is preferably less than ½ of the signal wavelength. This is because, by setting the signal wavelength to less than ½ of the signal wavelength, the electromagnetic wave is less likely to leak from between the plurality of shield through conductors, so that the shielding effect can be enhanced.

  The shield through conductor constituting the shield conductor 8 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.

  The inner ground conductor layer 4, the lower ground conductor layer 5, the line conductor 6, the same ground conductor layer 7, and the shield conductor 8 are metallized mainly of tungsten, molybdenum, gold, silver, copper, or the like, or gold, silver A metal foil mainly composed of copper, aluminum, or the like is used.

  The aperture 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 8 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 7 in which the slots 3 are formed. When the dielectric layer 1 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.). Further, nickel plating and gold plating are applied to the surface of the conductor exposed on the surface of the line conductor 6, the same-surface ground conductor layer 7, and the like.

  The shield conductor 8 is disposed on the side surface or the inside of the dielectric layer 1 so as to surround one end of the line conductor 6 and the slot 3, and is electrically connected to the same-surface ground conductor layer 7 and grounded.

  The shield conductor 8 may be composed of a plurality of shield through conductors arranged inside the dielectric layer 1. When the shield conductor 8 is formed of a plurality of shield through conductors in this way, the shape of the region surrounded by the shield conductor 8 of the dielectric layer 1 can be arbitrarily designed. For example, the shield conductor of the dielectric layer 1 When unnecessary resonance occurs in the region surrounded by 8, it is possible to adjust the arrangement of the shield conductor 8 to shift the unnecessary resonance out of the signal conversion band.

  The gap (indicated by G) between the shield through conductors is preferably less than ½ 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 ½ of the signal wavelength, so that the shielding effect can be enhanced.

  The shield through conductor constituting the shield conductor 8 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.

Further, as shown in FIG. 1, the width (indicated by W) of the slit 9 formed in the lower ground conductor layer 5 is 1/5 or more of the effective wavelength inside the slit 9 of the high-frequency signal radiated from the opening. Oh Ru.

  As a result, the inside and the outside of the slit 9 of the lower surface ground conductor layer 5 are completely separated in terms of high frequency, so that it is less likely to be affected by the outside of the slit 9. As a result, further improvement in radiation efficiency and radiation characteristics are achieved. Can be stabilized.

  Examples of the aperture antenna according to the present invention will be described below.

  A line conductor 6 and a coplanar ground conductor layer 7 having a characteristic impedance of 50Ω were formed as a high-frequency line 2 inside a dielectric layer 1 made of alumina ceramics having a relative dielectric constant of 8.6 and a thickness of 0.45 mm. Further, a slot 3 having a length in the line direction of the line conductor 6 of 0.12 mm and a length in the direction perpendicular to the line conductor 6 of 0.68 mm is formed in the ground contact conductor layer 7 so as to be orthogonal to the line conductor 6. .

  Here, a simulation of radiation characteristics at 76.5 GHz was performed under the following conditions using a high-frequency three-dimensional structure simulator (HFSS manufactured by Ansoft).

The diameter of the lower surface ground conductor layer 5 was 4 mm, and the width W of the slit 9 was changed in the range of 0.2 to 1 mm.

A simulation result of the radiation gain (dBi) with respect to the width W of the slit 9 is shown in FIG.

As a result, in FIG. 3, it was confirmed that the radiation gain was improved by providing the slit 9 as compared with the comparative example without the slit (slit width W = 0 mm).

In general, the difference from the peak value of radiation gain is within 3 dB due to the characteristics required in communication systems and radar systems using microwaves and millimeter waves, and the half-value width and bandwidth of antennas and filters. Is an effective radiation gain range. Thus, in this simulation result shall be the valid range width W of the slit 9 the difference between the radiation gain peak value that Do within 3 dB.

As shown in FIG. 3, the effective range of the width W of the slit 9 is from 0.25 mm to 1/5 times the effective wavelength (1.337 mm ) inside the dielectric of the high frequency signal (76.5 GHz). It corresponds to the above.

  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, the shape of the slit 9 is circular in FIG. 1, but it may be a rectangle as shown in FIG. 2 or a polygon.

  In FIG. 1, the width of the slit 9 is constant, but may be partially changed. However, in that case, the width of the slit 9 indicates the narrowest portion.

  Furthermore, although the example in the case where the shield conductor 8 is a plurality of through conductors is shown in FIG. 1, it may be a shield conductor portion made of a metal block or the like.

It is the schematic for demonstrating an example of the aperture surface antenna of this invention, (a) is a top view, (b) is sectional drawing in the XX 'line | wire of the structure shown to (a), (c) is A bottom view, (d) is a plan view of the layer on which the internal ground conductor layer 4 is formed. It is the schematic (lower surface) for demonstrating the other example of the aperture surface antenna of this invention. It is a simulation result which shows the relationship between the width W of a slit and the radiation gain in the Example and comparative example of an aperture antenna of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric layer 2 High frequency line 3 Slot 4 Internal grounding conductor layer 5 2nd grounding conductor layer (lower surface grounding conductor layer)
6 Line conductor 7 First ground conductor layer (coplanar ground conductor layer)
8 Shield conductor 9 Slit

Claims (1)

A dielectric layer having first and second surfaces;
A high-frequency line formed on the first surface of the dielectric layer and comprising a line conductor and a first grounding conductor layer surrounding an end of the line conductor;
A slot formed on the first surface of the dielectric layer so as to intersect the line conductor;
An internal ground conductor layer formed within the dielectric layer and having an opening facing the slot;
A second grounding conductor layer formed on the second surface of the dielectric layer and having an opening facing the slot;
In the second ground conductor layer, a slit surrounding the opening of the second ground conductor layer is formed on the same plane as the opening in a state where the slit is exposed to a radiation space of a high-frequency signal radiated from the opening. , the width of the slit, aperture antenna, wherein the at 1/5 or more effective wavelength at the slit inside the high-frequency signal radiated from the opening of the second ground conductor layer.

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