Microstrip antenna

To provide a microstrip antenna that can radiate electromagnetic waves in two or more different directions while suppressing an increase in manufacturing cost. The microstrip antenna is configured to include: a dielectric substrate 10 that is adapted to be of a folded flat plate shape; two or more radiating patterns 2 for radiating electromagnetic waves; and a connecting pattern 3 for mutually connecting the radiating patterns 2 and feeding electricity from a common feeding point 4 to each of the radiating patterns 2. The radiating patterns 2 and connecting pattern 3 are respectively adapted as microstrip lines formed on the dielectric substrate 10, and the dielectric substrate 10 is folded such that the connecting pattern 3 intersects with a ridge line 5, and has two or more radiating surfaces 10a to 10c of which normal directions are mutually different.

CROSS REFERENCE

This application claims the benefit of JP2013-086152 filed on Apr. 16, 2013 which is incorporated herein by reference in its entity.

TECHNICAL FIELD

The present invention relates to a microstrip antenna, and more particularly, to the improvement of a microstrip antenna in which a radiating pattern for radiating electromagnetic waves is formed on a dielectric substrate, such as a microstrip antenna usable for application such as communication using radio waves in a microwave or milliwave band.

BACKGROUND SECTION OF THE INVENTION

A microstrip antenna is a small-sized light-weight antenna that uses an MSL (microstrip line) formed on a dielectric substrate to transceive radio waves in a microwave or milliwave band, and used as a surveillance radar antenna or a communication antenna. For example, an MSL is configured to include a substantially linear feed line, a plurality of radiating elements arranged along the feed line, and a ground layer formed through a dielectric layer.

A conventional microstrip antenna is a planar antenna in which a radiating pattern and a feeding point constituting an MSL are formed on a front surface of a dielectric substrate and a ground layer is formed on a back surface side of the dielectric substrate, and can radiate electromagnetic waves only in one direction intersecting with the dielectric substrate (e.g., Patent Literature 1 (JP-A-2013-31064)). For this reason, in order to radiate electromagnetic waves in two or more different directions, it is necessary to arrange a plurality of microstrip antennas in mutually different directions, and feed high frequency signals to the microstrip antennas.

That is, in the case of attempting to radiate the electromagnetic waves in the two or more directions, it is necessary to fabricate a plurality of dielectric substrates, which gives rise to a problem of increased manufacturing costs. Also, in the case of distributing the high frequency signals to the respective dielectric substrates, and then feeding the high frequency signals to the respective microstrip antennas, there is a problem of a complicated configuration of transmission lines that connect a high frequency circuit and the microstrip antennas to each other.

On the other hand, in the case of distributing the high frequency signals on any of the dielectric substrates, and then feeding the high frequency signals to the respective microstrip antennas, MSLs should be connected between the dielectric substrates, and therefore connectors for MSL connection should be separately provided. For this reason, there are problems of increased manufacturing costs and also large power loss.

SUMMARY SECTION OF THE INVENTION

The present invention is made in consideration of the above-described situations, and intended to provide a microstrip antenna that can radiate electromagnetic waves in two or more different directions while suppressing manufacturing costs.

Also, the present invention is intended to provide a microstrip antenna that enables the connection with a high frequency circuit to be simplified and power loss to be suppressed.

A microstrip antenna according to a first aspect of the present invention is configured to be provided with: two or more radiating patterns for radiating electromagnetic waves; and a connecting pattern for mutually connecting the radiating patterns and feeding electricity from a common feeding point to each of the radiating patterns, wherein: the radiating patterns and the connecting pattern are adapted as microstrip lines formed on a dielectric substrate; and the dielectric substrate is adapted to be of a flat plate shape that is folded such that the connecting pattern intersects with a ridge line, and has two or more radiating surfaces of which normal directions are mutually different.

In the microstrip antenna, the two or more radiating surfaces of which the normal directions are mutually different are formed by folding the dielectric substrate, and on the radiating surfaces, the radiating patterns are respectively formed. For this reason, as compared with the case of forming two or more radiating surfaces respectively on different dielectric substrates, manufacturing cost can be suppressed, and also miniaturization can be realized. Also, it is not necessary to connect two or more dielectric substrate to a high frequency circuit, and therefore power loss can be suppressed. Further, by connecting the two or more radiating patterns to the common feeding point with use of the connecting pattern intersecting with the ridge line, as compared with the case of providing a feeding point for each radiating pattern to connect a high frequency circuit to two or more feeding points, manufacturing cost can be suppressed and power loss can be suppressed.

A microstrip antenna according to a second aspect of the present invention is, in addition to the above configuration, configured such that each of the radiating surfaces is adapted to be of an elongate shape; and each of the radiating patterns includes: a substantially linear feed line that extends in a longer direction of a corresponding one of the radiating surfaces; and two or more radiating elements that are arranged along the feed line.

According to such a configuration, while suppressing an area of each of the radiating surfaces, an array antenna including the two or more radiating elements on each of the radiating surfaces is formed, and therefore it is possible to form the antenna having sharp directivity in directions respectively intersecting with the radiating surfaces.

A microstrip antenna according to a third aspect of the present invention is, in addition to the above configuration, configured such that each of the radiating surfaces is adapted to be of an elongate shape of which a longer direction is a direction substantially parallel to the ridge line. According to such a configuration, a size of the dielectric substrate in a direction intersecting with the ridge line can be decreased.

A microstrip antenna according to a fourth aspect of the present invention is, in addition to the above configuration, configured such that each of the radiating surfaces is adapted to be of an elongate shape of which a longer direction is a direction intersecting with the ridge line. According to such a configuration, a size of the dielectric substrate in the ridge line direction can be decreased.

A microstrip antenna according to a fifth aspect of the present invention is, in addition to the above configuration, configured such that the dielectric substrate is made of fluorine resin containing inorganic fiber. According to such a configuration, it is possible to reduce dielectric loss while ensuring mechanical strength of the dielectric substrate.

A microstrip antenna according to a sixth aspect of the present invention is, in addition to the above configuration, configured such that on the dielectric substrate, a ground layer covering a back surface is formed, and a slit is formed in a location of the ground layer, which faces to the ridge line. According to such a configuration, a process for folding the dielectric substrate along the ridge line can be facilitated.

The microstrip antenna according to the present invention can radiate radio waves in two or more different directions while suppressing manufacturing costs. Also, it is not necessary to connect two or more dielectric substrates to a high frequency circuit, and therefore the connection with the high frequency circuit can be simplified to suppress power loss.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a perspective view illustrating a configuration example of a microstrip antenna1according to an embodiment of the present invention. The microstrip antenna1is a small-sized light-weight antenna suitable for transmitting or receiving radio waves in a frequency band of UHF (Ultra High Frequency) or high frequency, and can be used as a communication or radar antenna. In particular, the microstrip antenna1is preferable for transceiving radio waves in a milliwave band (frequency of 30 GHz to 300 GHz).

The microstrip antenna1is configured to include: a dielectric substrate10of a folded flat plate shape; two or more radiating patterns2formed on the dielectric substrate10; and a connecting pattern3.

The dielectric substrate10is an antenna substrate configured to include a dielectric layer11made of a dielectric having a small dielectric constant, and a ground layer12made of a conductor, and on the dielectric layer11, the radiating patterns2and the connecting pattern3are formed. The ground layer12is formed so as to cover the entire back surface of the dielectric substrate10, and forms an earth plate.

Each of the radiating patterns2is an electrode pattern for radiating the electromagnetic waves, and includes a feed line21for transmitting high frequency signals, and radiating elements22for radiating the high frequency signals to free space. The connecting pattern3is an electrode pattern for mutually connecting the radiating patterns2and feeding electricity from a common feeding point4to the respective radiating patterns2. In this embodiment, the connecting pattern3serves as a branching circuit that connects the feeding point4to the respective radiating patterns2, and when high frequency signals are inputted to the feeding point4, distributes the high frequency signals for the respective radiating patterns2to feed the high frequency signals to one ends of the radiating patterns.

The radiating patterns2and connecting pattern3are all arranged so as to face to the ground layer12through the dielectric layer11, and constitute a MSL. The feeding point4is connected to a high frequency circuit (not illustrated). To connect the feeding point4and the high frequency circuit to each other, a well-known method can be used. For example, by providing a matching element electromagnetically coupled to a waveguide or a strip line as the feeding point4, power can be transmitted between the microstrip antenna1and the high frequency circuit with low loss.

In the microstrip antenna1, by folding the dielectric substrate10such that the connecting pattern3intersects with ridge lines5, three radiating surfaces10ato10cand the two ridge lines5are formed. That is, a cross section formed in the case of cutting the dielectric substrate10along a plane intersecting with the ridge lines5is of a substantially U-shape. Considering dielectric loss, a thickness of the dielectric substrate10is preferably about 25 μm.

Each of the radiating surfaces10ato10cis a substrate surface having an elongate shape of which a longer direction is substantially parallel to the ridge lines5, and on each of the radiating surfaces10ato10c, at least one radiating pattern2is arranged. The respective radiating surfaces10ato10cface in mutually different directions, and are adjacent through the ridge lines5. That is, the radiating surfaces10aand10bare arranged so as to be adjacent to each other through a corresponding one of the ridge lines5, whereas the radiating surfaces10band10care arranged so as to be adjacent to each other through the other ridge line5. By mutually differentiating the directions normal to the respective radiating surfaces10ato10cradiating the electromagnetic waves, the electromagnetic waves can be radiated in the two or more different directions.

Also, a feed line21of each of the radiating patterns2is a substantially linear transmission line extending in a longer direction of a corresponding one of the radiating surfaces10ato10c, and along the feed line21, two or more radiating elements22are arranged. That is, a radiating pattern2on each of the radiating surfaces10ato10cforms a planar array antenna, and by arranging respective radiating elements22so as to utilize interference to mutually intensify the electromagnetic waves radiated from the plurality of radiating elements22, sharp directivity is realized in a predetermined direction intersecting with the radiating surface10ato10c.

Each of the feed lines21includes a linearly shaped area that extends with keeping a constant width, of which one end is connected to the connecting pattern3. Each of the radiating elements22includes an area of a shape formed by widening the line width of a feed line21, for example, an area of a rectangular shape formed by protruding parts of lateral sides of a feed line21outward. A length by which each of the parts of the lateral sides of the feed line21is protruded to form the radiating element22is determined depending on a wavelength of the electromagnetic waves to be resonated.

In this example, each of the radiating surfaces10ato10cis a substantially rectangular-shaped substrate surface of which one or both long sides serve as the ridge lines5, and any adjacent two of the radiating surfaces intersect with each other at a substantially right angle. By folding the dielectric substrate10so as to make an intersecting angle between any adjacent two of the radiating surfaces equal to the substantially right angle as described, the sharp directivity can be realized in each of the three directions any adjacent two of which are orthogonal to each other in a plane perpendicular to the longer directions of the radiating surfaces10ato10c.

Also, on each of the radiating surfaces10ato10c, one radiating pattern2is arranged, and one end of the radiating pattern2is connected to the connecting pattern3. That is, electricity is fed from the one end to the other end of the radiating pattern2, and feeding directions of the respective radiating patterns2are the same.

Also, the feeding point4is provided on the central radiating surface10b. Specifically, part of the connecting pattern3is formed so as to be extended toward one of short sides of the radiating surface10band exposed from an end surface on the short side of the dielectric substrate10, and near the short side, the feeding point4is arranged. Note that the connecting pattern3does not have to be exposed from the end surface of the dielectric substrate10.

<Folding Process of Dielectric Substrate10>

FIG. 2is a perspective view illustrating an example of a manufacturing process of the micro strip antenna1inFIG. 1, and illustrates a folding process of the dielectric substrate10formed with the radiating patterns2and connecting pattern3on the front surface. Also,FIG. 3is a cross-sectional view illustrating a configuration example of the dielectric substrate10inFIG. 2, and illustrates a cross section formed in the case of cutting the dielectric substrate10along an A-A cutting-plane line.

The microstrip antenna1is prepared by forming the radiating patterns2and connecting pattern3on the front surface of the dielectric substrate10and then folding the dielectric substrate10so as to form the ridge lines connecting between the opposite end surfaces of the dielectric substrate10on the front surface side.

The dielectric layer11of the dielectric substrate10is made of a resin member that has appropriate rigidity and is processable in a foldable manner. For example, the dielectric layer11is made of fluorine resin that has a small dielectric constant and can reduce dielectric loss. The fluorine resin herein means general fluorine-contained resin, and as the fluorine resin, various types of fluorine resins can be used. For example, polytetrafluoroethylene (PTFE) may be used to form the dielectric layer11.

In this embodiment, in order to ensure mechanical strength, the dielectric layer11is made of fluorine resin containing inorganic fiber. As the inorganic fiber, glass fiber or carbon fiber is available, and the dielectric layer11is made of a fluorine resin member reinforced by such inorganic fiber. In addition, as the resin member forming the dielectric layer11, polyimide resin (PI) or liquid crystal polymer (LCP) can also be used.

Such a dielectric substrate10is formed by stacking one or two prepregs and two copper foil sheets and then performing a press process of them under high temperature vacuum. A prepreg is a sheet-like member, and manufactured from a long glass cloth through an impregnation process, sintering process, and cutting process. The impregnation process is a process of impregnating the glass cloth with the fluorine resin. The sintering process is a process of melting or softening the fluorine resin by heating to cover the glass cloth. The cutting process is a process of cutting the glass cloth into sheets having an appropriate size and shape.

One of the copper foil sheets forms into the ground layer12, whereas the other copper foil sheet forms into the radiating patterns2and connecting pattern3. The radiating patterns2and connecting pattern3are formed by employing photo-etching to pattern a metal film made of the copper foil.

In this example, on the substantially rectangular-shaped dielectric substrate10, the three radiating patterns2and one connecting pattern3are formed. Parameters such as the line widths of the radiating and connecting patterns2and3, the shape and size of each of the radiating elements22, the number of, arrangement of, and interval between radiating elements22within each of the radiating patterns2, and a thickness of the dielectric layer11are determined depending on required radiation characteristics.

In the folding process of the dielectric substrate10after the formation of the radiating patterns2and connecting pattern3, the dielectric substrate10is folded so as to form the ridge lines on the front surface side, and form value lines on the back surface side. Adjusting the intersecting angle between any adjacent two of the radiating surfaces10ato10cat this time enables radiation directions of the radio waves to be arbitrarily controlled.

FIG. 4is a diagram illustrating an example of directional characteristics of the microstrip antenna1inFIG. 1, and illustrates vertical and horizontal distributions B1and B2of radiation gain that is measured in a state where the radiating surface10bin the center is verticalized, and the radiating surfaces10aand10bon the both sides are horizontalized. Curves in the diagram represent the vertical distribution B1and the horizontal distribution B2with the horizontal and vertical axes representing an angle (deg.) and the gain (dB), respectively. The gain is absolute gain with reference to an isotropic antenna.

The microstrip antenna1used for the measurement is an antenna of which the dielectric layer11has a thickness of 0.126 mm and a dielectric constant of 2.22, and the metal film forming the radiating patterns2and connecting pattern3has a thickness of 12 μm.

The vertical distribution B1is a gain distribution that is shown with, in a vertical plane perpendicular to the longer directions of the radiating surfaces10ato10c, a normal direction of the radiating surface10bbeing set as 0° and an elevation angle direction being set to the positive direction, in which peaks (peak values are approximately 10 dB) appear at positions of 0°, +90°, and −90°. That is, it turns out that the microstrip antenna1is an antenna of which radiation characteristics have, with respect to the vertical plane, sharp directivities in the front direction of the radiating surface10b, and upward and downward in the vertical direction.

The horizontal distribution B2is a gain distribution that is shown with, in the horizontal plane, the normal direction of the radiating surface10bbeing set as 0° and one of orientation directions being set to the positive direction, in which a peak (a peak value is approximately 10 dB) of a main lobe appears at a position of 0°, and at positions of +90° and −90°, asymptotes (gains are −40 dB or less) are present. That is, it turns out that the microstrip antenna1is an antenna of which the radiation characteristics have, with respect to the horizontal plane, sharp directivity in the front direction of the radiating surface10b.

FIG. 5Ais a perspective view illustrating an example of an electronic device100that, in a thin casing110, contains the microstrip antenna1inFIG. 1.FIG. 5Bis a cross-sectional view illustrating a cross section when cutting the electronic device100along a C-C cutting-plane line. In this diagram, a longer direction of the thin casing110is set to an x direction, and a direction perpendicular to a display screen is set to a z direction.

The electronic device100is a portable terminal device including the thin casing110, such as a mobile phone, PDA (Personal Digital Assistant), tablet terminal, or handheld game console, and the thin casing110is provided with a display device101having the display screen, and operation keys104. The thin casing110is of a vertically long and thin rectangular parallelepiped shape. The display device101and the operation keys104are provided on a front surface of the thin casing110.

Inside the thin casing110, a circuit board102provided with a high frequency circuit for communication, and the like, and a battery103for feeding power to the high frequency circuit, the display device101, and the like are contained. For example, by arranging the microstrip antenna1such that the radiating surfaces10aand10cface to a principal surface of a set of the stacked circuit board102and battery103, and the radiating surface10bfaces to an end surface of the set of the stacked circuit board102and battery103, the microstrip antenna1can be contained in a tiny space inside the thin casing110. Accordingly, the electronic device100capable of radiating the electromagnetic waves in two or more directions can be miniaturized.

In this example, the microstrip antenna1is arranged in an end part on the side opposite to the operation keys104in the longer direction of the thin casing110, is attached so as to surround the periphery of part of the stacked circuit board102and battery103, and can be made to have the sharp directivities in three directions. Also, the electronic device100can emit the radio waves in the x and z directions from the end part on the side opposite to the operation keys104in the longer direction of the thin casing110.

Further, by adjusting the number of radiating patterns2on each of the radiating surfaces10ato10c, and/or adjusting the number of radiating elements22in each of the radiating patterns2, a communicable distance can be made difference between the x and z directions. For example, setting the communicable distance in the x direction to approximately 5 to 10 m is preferable for emitting the radio waves toward a wireless access point while performing a display operation. Also, setting the communicable distance in the z direction to approximately 5 to 10 cm is preferable for communication with a reader/writer.

According to the present embodiment, as compared with the case of forming two or more radiating surfaces respectively on different dielectric substrates, manufacturing costs can be suppressed, and also miniaturization can be realized. Also, it is not necessary to connect the two or more dielectric substrates to a high frequency circuit, and therefore power loss can be suppressed. Further, by connecting the two or more radiating patterns2to the common feeding point4with use of the connecting pattern3intersecting with the ridge lines5, as compared with the case where a feeding point is provided for each radiating pattern, and a high frequency circuit is connected to the two or more feeding points, manufacturing cost can be suppressed, and also power loss can be suppressed.

FIG. 6A to 6Care perspective views illustrating other configuration examples of the microstrip antenna1, in which each ofFIG. 6A to 6Cillustrates the case where on a dielectric substrate10, two radiating surfaces10aand10bare formed.

InFIG. 6A, the radiating surfaces10aand10bare arranged so as to be adjacent to each other through a ridge line5that corresponds to long sides of the radiating surfaces10aand10b. Also, each of the radiating surfaces10aand10bis of an elongate shape of which a longer direction is a direction substantially parallel to the ridge line5, and on each of the radiating surfaces10aand10b, one radiating pattern2is formed. The dielectric substrate10is folded at substantially right angle along the ridge line5, and a cross section of the dielectric substrate10is of a substantially L-shape. Further, a connecting pattern3is formed at one ends of the radiating surfaces10aand10bin their longer directions, and connects a common feeding point4provided on the radiating surface10ato the two radiating patterns2. By employing such a configuration, the two radiating patterns2extending in substantially parallel can be used to radiate electromagnetic waves in mutually different directions.

For example, by arranging the microstrip antenna1inFIG. 6Asuch that the radiating surfaces10aand10brespectively face to the principle surface and end surface of the set of the stacked circuit board102and battery103inside the electronic device100, the microstrip antenna1can be contained in a tiny space inside the thin casing110of the electronic device100. Accordingly, the electronic device100capable of radiating electromagnetic waves in two or more directions can be miniaturized.

The radiating surfaces10aand10binFIG. 6Bare arranged so as to be adjacent to each other through a ridge line5that corresponds to short sides of the radiating surfaces10aand10b. Also, each of the radiating surfaces10aand10bis of an elongate shape of which a longer direction is a direction intersecting with the ridge line5, and on each of the radiating surfaces10aand10b, one radiating pattern2is formed. A connecting pattern3is formed near the ridge line5to connect a common feeding point4provided on the radiating surface10ato the two radiating patterns2. By employing such a configuration, the two radiating patterns2intersecting with each other can be used to radiate electromagnetic waves in mutually different directions. Also, the width of the microstrip antenna1in the ridge direction can be shortened.

For example, by arranging the microstrip antenna1inFIG. 6Balong the end surfaces of the set of the stacked circuit board102and battery103incorporated in the electronic device100around an apex angle of the set, the microstrip antenna1can be contained in a tiny space inside the thin casing110of the electronic device100in a state where the radiating surfaces10aand10bare made to face to the two mutually adjacent end surfaces. Accordingly, the electronic device100capable of radiating electromagnetic waves in two or more directions can be miniaturized.

FIG. 6Cillustrates the case where between the two radiating surfaces10aand10b, a non-radiating surface10dis present. Each of the radiating surfaces10aand10band non-radiating surface10dis of an elongate shape of which a longer direction is a direction substantially parallel to ridge lines5, and on the radiating surfaces10aand10b, radiating patterns2are respectively formed, whereas on the non-radiating surface10d, no radiating pattern2is formed. The radiating surface10aand the non-radiating surface10dare adjacent to each other through a corresponding one of the ridge lines5, and the non-radiating surface10dand the radiating surface10bare adjacent to each other through the other ridge line5.

A connecting pattern3is formed at one ends of the radiating surfaces10aand10band non-radiating surface10din their longer directions, and a feeding point4is arranged on the non-radiating surface10d. Even by employing such a configuration, electromagnetic waves can be radiated in two or more directions.

FIG. 7is a perspective view illustrating still another configuration example of the microstrip antenna1, and illustrates a dielectric substrate10on which one end of a radiating pattern2is connected with a feeding point4, and the other end of the radiating pattern2is connected with a connecting pattern3. In this microstrip antenna1, the dielectric substrate10has two mutually adjacent radiating surfaces10aand10b, and each of the radiating surfaces10aand10bis of an elongate shape of which a longer direction is a direction substantially parallel to a ridge line5.

On the radiating surface10a, the one radiating pattern2is arranged along the ridge line5, and the one end of the radiating pattern2is connected with the feeding point4, whereas the other end of the radiating pattern2is connected with the connecting pattern3. On the radiating surface10b, one radiating pattern2is arranged along the ridge line5.

The connecting pattern3connects the radiating patterns2on the respective radiating surfaces10aand10bto each other on the side opposite to the feeding point4. That is, between the radiating surfaces10aand10b, a feeding direction of a radiating pattern2is reversed. Even with such a configuration, in a plane perpendicular to the longer directions of the radiating surfaces10aand10b, sharp directivities can be realized in two different directions.

Note that in the present embodiment, described is an example where the one feeding point4is formed on the dielectric substrate10; however, the present invention can also be applied to the case of providing two or more feeding points4on the dielectric substrate10. Further, in the present embodiment, described is an example where on each of the radiating surfaces10ato10c, one radiating pattern2is formed; however, the present invention can also be applied to the case of providing two or more radiating patterns2on a radiating surface.

For example, the present invention may be configured to arrange two radiating patterns2on a radiating surface in parallel with each other, and connect one ends of feed lines21to each other through a connecting pattern3. Alternatively, the present invention may be configured to arrange two radiating patterns2on a radiating surface such that the two radiating patterns2extend in mutually opposite directions, and connect the two radiating patterns2to each other through a connecting pattern3.

Also, in the present embodiment, described is an example where by folding the dielectric substrate10formed with the radiating patterns2and connecting pattern3, the microstrip antenna1is prepared; however, the present invention does not limit a manufacturing method for the microstrip antenna1to this.

For example, the present invention may be configured to fold a dielectric substrate10, which is formed with a ground layer12on a back surface and formed with a metal film on a front surface, so as to form a ridge line on the front surface side, and then use photo-etching to pattern the metal film, and thereby form radiating patterns2and a connecting pattern3. Alternatively, the present invention may be configured to fold a dielectric substrate10, which is formed with a ground layer12on a back surface, then form a metal film on the dielectric substrate10, and pattern the metal film to form radiating patterns2and a connecting pattern3.

Further, in the present embodiment, described is an example where the ground layer12is formed so as to cover the entire back surface of the dielectric substrate10; however, the present invention does not limit the configuration of the ground layer12, which forms the earth plate for the radiating patterns2and connecting pattern3, to this. For example, in a ground layer12covering a back surface of a dielectric substrate10, a slit is formed along a ridge line5. The slit is formed in a location facing to the ridge line5, and of a shape that extends in parallel with the ridge line5with keeping a substantially uniform width. For example, the slit is formed from one end surface to the other end surface of the dielectric substrate10. By forming such a slit in the ground layer12, a process for folding the dielectric substrate10along the ridge line5can be facilitated. Note that the present invention may be configured to, instead of forming the one slit from the one end surface to the other end surface of the dielectric substrate10, form two or more slits with respect to the same ridge line5, and conduct pieces of the ground layer12separated by the slits. By configuring as described, it is possible to suppress the deterioration of radiation characteristics, while facilitating a process for folding the dielectric substrate10along the ridge line5.