Microstrip antenna

Abstract

This microstrip antenna comprises: a first dielectric layer; a first conductor layer that is a ground surface disposed on the lower surface of the first dielectric layer; and a second conductor layer that is a power feeding surface disposed on the upper surface of the first dielectric layer. The second conductor layer includes a plurality of power feeding patches and a transmission line that transmits a signal between the plurality of power feeding patches and a terminal. The entire outer periphery of the transmission line has an arc shape in a connection region connected to the plurality of power feeding patches.

Description

Microstrip Antenna

[0001] The present invention relates to a microstrip antenna.

[0002] For example, as disclosed in Non-Patent Document 1, various studies have been conducted on microstrip antennas.

[0003] Cahya Edi Santosa et al. , "Broadband Circularly Polarized Microstrip Array Antenna With Curved-Truncation and Circle-Slotted Parasitic", IEEE Transactions on Antennas and Propagation (USA), September 2021, Vol. 69, No. 9, p. 5524-5533

[0004] For example, electromagnetic waves are irradiated onto an object to be measured from a microstrip antenna, and the shape, condition, etc. of the object are measured based on the received data obtained by receiving the reflected waves from the object. When measuring the condition, etc. of the object, modulated electromagnetic waves such as chirp pulse waves are used from the viewpoint of increasing resolution, and a microstrip antenna with a wide frequency bandwidth is required to eliminate the effects of multiple scattering.

[0005] Therefore, one aspect of the present invention has an object to provide a microstrip antenna with a wide frequency bandwidth.

[0006] In order to solve the above problem, one aspect of the present invention provides a microstrip antenna having: a first dielectric layer; a first conductor layer which is a ground plane arranged on the lower surface of the first dielectric layer; and a second conductor layer which is a feed plane arranged on the upper surface of the first dielectric layer, wherein the second conductor layer has a plurality of feed patches; and a transmission line which transmits signals between the plurality of feed patches and a terminal, and the transmission line has an outer periphery which is all arc-shaped in a connection region where it is connected to the plurality of feed patches.

[0007] According to one aspect of the present invention, a microstrip antenna with a wide frequency bandwidth can be provided.

[0008] FIG. 1 is a cross-sectional view of a microstrip antenna according to one embodiment of the present disclosure. FIG. 2 is a top view of a second conductor layer included in the microstrip antenna according to one embodiment of the present disclosure. FIG. 3 is a cross-sectional view of a microstrip antenna according to one embodiment of the present disclosure. FIG. 4 is a top view of a third conductor layer included in the microstrip antenna according to one embodiment of the present disclosure. FIG. 5 shows measurement results and simulation results for the return loss of the antenna fabricated in Example 1. FIG. 6 shows measurement results and simulation results for the axial ratio and gain of the antenna fabricated in Example 1. FIG. 7 shows measurement results and simulation results for the return loss of the antenna fabricated in Example 2. FIG. 8 shows measurement results and simulation results for the axial ratio and gain of the antenna fabricated in Example 2.

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and substitutions can be made to the following embodiments without departing from the scope of the present invention. [Microstrip Antenna] (1) Structure of Microstrip Antenna (1-1) First Embodiment A cross-sectional view of a microstrip antenna (hereinafter also simply referred to as "antenna") according to a first embodiment is shown in FIG. 1. As will be described below, the second conductor layer 122 is patterned, and therefore may include portions in the cross section where the second conductor layer 122 is not disposed. However, since FIG. 1 is a schematic diagram, the second conductor layer 122 is shown as a continuous layer.

[0010] As shown in FIG. 1, the antenna 10 of this embodiment includes a first dielectric layer 111, a first conductor layer 121, and a second conductor layer 122.

[0011] The first conductor layer 121 is a ground plane disposed on the lower surface 111B of the first dielectric layer 111 .

[0012] The second conductor layer 122 is a power supply surface disposed on the upper surface 111A of the first dielectric layer 111 .

[0013] The antenna 10 according to the first embodiment is a direct power feeding type antenna. (1-1-1) Structure of the First Dielectric Layer The first dielectric layer 111 can have a plate-like shape. For example, as shown in FIG. 2, it can have a quadrangular shape when viewed from above, and a rectangular shape is preferable. When the first dielectric layer 111 has a rectangular shape when viewed from above, it may be either a square or a rectangle, but a square shape is preferable.

[0014] The thickness T111 of the first dielectric layer 111 is not particularly limited, but is preferably 0.5 mm or more and 10 mm or less, and more preferably 1 mm or more and 3 mm or less. (1-1-2) Structure of the First Conductor Layer Since the first conductor layer 121 is a ground plane, it can be arranged to cover the entire lower surface 111B of the first dielectric layer 111.

[0015] The thickness T121 of the first conductor layer 121 is not particularly limited, but is preferably 0.0001 mm or more and 0.1 mm or less, and more preferably 0.0003 mm or more and 0.01 mm or less. (1-1-3) Structure of the Second Conductive Layer Figure 2 shows a top view of the second conductor layer 122 as viewed from above.

[0016] 2, the second conductor layer 122 has a plurality of feed patches 21 and a transmission line 23 that transmits signals between the plurality of feed patches 21 and the terminal 22. (Transmission Line) According to the study by the inventors of the present invention, the shape of the transmission line 23 affects the frequency bandwidth of the antenna 10. For this reason, further study was conducted on the shape of the transmission line 23.

[0017] As a result, they found that the frequency bandwidth can be expanded by making the outer periphery of the connection area of ​​the transmission line 23 connected to the multiple feed patches 21 into an arc shape, and completed the present invention.

[0018] In this specification, the frequency bandwidth means the axial ratio bandwidth.

[0019] Therefore, in the antenna 10 of this embodiment, the transmission line 23 of the second conductor layer 122 can have the entire outer periphery 23A in the connection region A where it is connected to the multiple feed patches 21, having an arc shape.

[0020] The transmission line 23 does not include the connection lines 24 that connect the transmission line 23 to each feed patch 21 and extend radially from the transmission line 23 to each feed patch 21. The connection area A refers to the area from the intersection of the transmission line 23 with the connection line 24 connected to the feed patch 21 closest to the terminal 22 to the intersection of the connection line 24 connected to the feed patch 21 farthest from the terminal 22. The intersection with the connection line 24 refers to the intersection of the transmission line 23 and the connection line 24 on the side of the connection line 24 farthest from the terminal 22.

[0021] The outer periphery 23A of the transmission line 23 does not need to be a continuous arc shape. The width of the transmission line 23 may vary depending on the location, so the position of the outer periphery 23A may be shifted at the point where it is connected to the connection line 24, as shown in Fig. 2, for example. Furthermore, the radius of curvature of the outer periphery of the transmission line 23 may vary depending on the location.

[0022] 2, the transmission line 23 may have a structure in which a plurality of annular sector-shaped members are connected together. Therefore, the inner periphery 23B of the transmission line 23 may also be arc-shaped.

[0023] The transmission line 23 may have different widths depending on the location.

[0024] An end portion of the transmission line 23 in the connection region A along the length thereof, which is closer to the terminal 22, is defined as a first end portion 231, and an end portion opposite the first end portion 231 is defined as a second end portion 232. In this case, the width W3 of the transmission line 23 at the second end portion 232 can be made shorter than the width W1 at the first end portion 231, for example.

[0025] By making the width W3 at the second end 232 shorter than the width W1 at the first end 231, electromagnetic waves can be transmitted and received uniformly from the entire feeding patch 21.

[0026] The transmission line 23 may be configured so that its width changes in multiple steps from the first end 231 toward the second end 232. For example, as shown in FIG. 2 , the width W1 at the first end 231, the width W2 at a point between the first end 231 and the second end 232, and the width W3 at the second end 232 may have a relationship of W3<W2<W1. That is, the width may be configured so that it becomes smaller in steps from the first end 231 toward the second end. Note that the width of the transmission line 23 refers to the length of the transmission line 23 in a direction perpendicular to the longitudinal direction.

[0027] 2, the width of the transmission line 23 may be constant in the region sandwiched between the connection lines 24, and the width of the transmission line 23 may be changed at the point where the connection lines 24 are connected. (Feed Patch) The feed patch 21 may be arranged along the outer periphery 23A of the transmission line 23.

[0028] The shape of the feed patch 21 is not particularly limited. For example, as shown in FIG. 2 , the feed patch 21 may have a contour line formed by connecting a pair of opposing vertices of a rectangle 25, vertices 25A and 25B, with curves 211 and 212. The feed patch 21 may have, for example, a prolate spheroid (oblong ellipse) with angular ends located at vertices 25A and 25B, i.e., a lanceolate shape. The curves 211 and 212 are preferably curves that include one inflection point, and may be conic sections, for example. The curves 211 and 212 may also include straight line segments along the contour line of the rectangle 25 near vertices 25A and 25B of the rectangle 25.

[0029] The rectangle 25 is an auxiliary line provided to define the contour of the feed patch 21, and does not directly constitute the contour of the feed patch 21. The size of the rectangle 25 can be selected depending on the size of the feed patch 21, such as its area, and may be either a rectangle or a square.

[0030] It is preferable that the multiple feeding patches 21 have the same shape and area.

[0031] The area of ​​the power supply patch 21 is not particularly limited, and can be selected based on the center frequency selected according to the object to be measured by the antenna 10, etc.

[0032] The number of feeding patches 21 is not particularly limited and can be selected depending on the characteristics required of the antenna 10. For example, when the antenna 10 is used to radiate electromagnetic waves, increasing the number of feeding patches 21 can narrow the gain range and radiation angle.

[0033] The thickness T122 of the second conductor layer 122 is not particularly limited, but is preferably 0.0001 mm or more and 0.1 mm or less, and more preferably 0.0003 mm or more and 0.01 mm or less. (1-2) Second Embodiment FIG. 3 shows a cross-sectional view of a microstrip antenna according to a second embodiment. Because the second conductor layer 122 and the third conductor layer 123 are patterned, the cross section may include portions where the second conductor layer 122 and the third conductor layer 123 are not arranged. However, because FIG. 3 is a schematic diagram, the second conductor layer 122 and the third conductor layer 123 are shown as continuous layers.

[0034] The antenna 30 of this embodiment may have a second dielectric layer 112 disposed on the upper surface 122A of the second conductor layer 122. The antenna 30 of this embodiment may further have a third conductor layer 123 that is a radiation surface disposed on the upper surface 112A of the second dielectric layer 112.

[0035] In the antenna 30 according to the second embodiment, the third conductor layer 123, which serves as a radiation patch, and the second conductor layer 122 are formed on separate dielectric layers (dielectric substrates). The antenna 30 is an electromagnetically coupled power feeding antenna in which the second conductor layer 122 is sandwiched between the dielectric layers.

[0036] By using an antenna of the electromagnetic coupling feeding type, it is possible to use a dielectric layer with an appropriate dielectric constant for the radiation patch and the feeding patch, which makes it easier to achieve the desired radiation characteristics.

[0037] The first conductor layer 121, the second conductor layer 122, and the first dielectric layer 111 can have the same configuration as in the first embodiment, and therefore a description thereof will be omitted. (1-2-1) Structure of the Second Dielectric Layer The second dielectric layer 112 can have a plate-like shape. For example, as shown in FIG. 4, the second dielectric layer 112 can have a quadrangular shape when viewed from above, and a rectangular shape is preferable. When the second dielectric layer 112 has a rectangular shape when viewed from above, it may be either a square or a rectangle, but a square shape is preferable.

[0038] However, since the second dielectric layer 112 is stacked on the first dielectric layer 111 to form the antenna 30, it is preferable that the first dielectric layer 111 and the second dielectric layer 112 have overlapping shapes, i.e., have the same contour lines, when viewed from above along the stacking direction.

[0039] The thickness T112 of the second dielectric layer 112 is not particularly limited, but is preferably 0.5 mm or more and 10 mm or less, and more preferably 1 mm or more and 3 mm or less. (1-2-2) Structure of the Third Conductive Layer Figure 4 shows a top view of the third conductor layer 123 as viewed from above.

[0040] 4, the third conductor layer 123 can have a plurality of radiating patches 41. (Radiating Patches) The radiating patches 41 can be arranged at locations corresponding to the feed patches 21 of the laminated second conductor layer 122. The radiating patches 41 and the feed patches 21 can be configured to have different shapes.

[0041] By making the radiation patch 41 and the feeding patch 21 have different shapes, the bandwidth of the antenna 30 can be further widened.

[0042] There is no particular limitation on the shape of the radiation patch 41. For example, the radiation patch 41 may have a shape surrounded by a contour line including a curve 421, a curve 422, a curve 423, and a curve 424, as shown in FIG.

[0043] Curves 421 and 422 are curves that connect a pair of opposing vertices 42A and 42B of rectangle 42. Curves 423 and 424 are curves that connect curves 421 and 422 near vertices 42A and 42B.

[0044] Therefore, the radiation patch 41 may have, for example, a rugby ball shape, i.e., a prolate spheroid shape (an oblong shape). Each of the curves 421, 422, 423, and 424 is preferably a curve that includes one inflection point, and may be, for example, a conic section. The shape of each curve is preferably selected so that the sides of the rectangle 42 are tangent to the contour line of the radiation patch 41.

[0045] The rectangle 42 is an auxiliary line provided to define the contour line of the radiation patch 41, and does not directly constitute the contour line, etc., of the radiation patch 41. The size of the rectangle 42 can be selected depending on the size, such as the area, of the radiation patch 41, and may be either a rectangle or a square.

[0046] The radiating patch 41 may have a shape that is curved, for example, near the vertices 25A and 25B of the rectangle 25 in the feed patch 21 shown in Figure 2. This allows the radiating patch 41 to have a longer perimeter, i.e., a longer curved portion of the contour line, than the feed patch 21. By making the curved portion of the radiating patch 41 longer than that of the feed patch 21, the bandwidth of the antenna 30 can be further expanded.

[0047] The radiation patches 41 preferably have the same shape and area.

[0048] The area of ​​the radiation patch 41 is not particularly limited, and can be selected based on the center frequency selected according to the object to be measured by the antenna 10, etc.

[0049] The number of radiation patches 41 is not particularly limited and can be selected depending on the characteristics required of the antenna 10. For example, when the antenna 10 is used to radiate electromagnetic waves, increasing the number of radiation patches 41 can narrow the gain range and radiation angle.

[0050] The thickness T123 of the third conductor layer 123 is not particularly limited, but is preferably 0.0001 mm or more and 0.1 mm or less, and more preferably 0.0003 mm or more and 0.01 mm or less. (2) Materials of Each Component (2-1) Dielectric Layer The materials of the first dielectric layer 111 and the second dielectric layer 112 are not particularly limited, and can be selected to include a dielectric having a predetermined relative dielectric constant depending on the characteristics required of the antennas 10 and 30, such as the size of the frequency bandwidth.

[0051] In addition, when the antenna 30 has two dielectric layers, a first dielectric layer 111 and a second dielectric layer 112, the first dielectric layer 111 and the second dielectric layer 112 may be made of different materials.

[0052] For example, the antenna of this embodiment can be used in fields such as monitoring volcanic activity, planetary exploration, etc. However, when monitoring volcanic activity by approaching an object to be measured in a closed space, the antenna may become hot due to the heat of the object to be measured, so a heat-resistant antenna may be required.

[0053] Therefore, from the viewpoint of making the antenna of this embodiment a heat-resistant antenna that can perform measurements near an object to be measured at a high temperature of, for example, 1000° C. or higher, it is preferable that the first dielectric layer 111 is made of ceramics, for example.

[0054] Alumina, an aluminum oxide, has traditionally been used as a material for ceramic dielectric layers. However, when an antenna using alumina as the dielectric layer material is heated to about 1000°C, the thermal expansion of the alumina causes significant dimensional changes in the antenna, resulting in the antenna exhibiting radiation characteristics different from those designed.

[0055] Therefore, the inventors of the present invention conducted further studies and found that by using cordierite or quartz glass as the material for the dielectric layer, the linear expansion of the antenna can be suppressed to about 0.2% or less in terms of dimensional ratio to room temperature, even when heated to about 1000° C. Therefore, by using cordierite or quartz glass as the material for the dielectric layer, a heat-resistant antenna can be obtained that exhibits the same radiation characteristics as at room temperature, even when heated to about 1000° C.

[0056] Furthermore, the relative dielectric constants of cordierite and quartz glass are relatively low among ceramics. By using a material with a low relative dielectric constant for the dielectric layer, the antenna bandwidth can be particularly widened.

[0057] For the above reasons, it is preferable that the first dielectric layer 111 contains cordierite or quartz glass. It is more preferable that the first dielectric layer 111 contains cordierite or quartz glass as a main component. "Contained as a main component" means that it is contained in the largest amount by mass, and it is preferable that it is contained in a proportion of 90 mass% or more. In the following explanation, "contained as a main component" has the same meaning as explained above.

[0058] Cordierite is 2MgO.2Al ２ O ３ 5SiO ２ It can be expressed by the chemical formula as follows and is composed of three components: magnesium oxide, aluminum oxide, and silicon dioxide.

[0059] The first dielectric layer 111 may be made of only cordierite or quartz glass, but even in this case, it is not excluded that the first dielectric layer 111 may contain components that are mixed in during the manufacturing process.

[0060] Furthermore, when the antenna has the second dielectric layer 112, the second dielectric layer 112 preferably contains cordierite or quartz glass. More preferably, the second dielectric layer 112 contains cordierite or quartz glass as a main component.

[0061] The second dielectric layer 112 may be made of only cordierite or quartz glass. However, even in this case, it is not excluded that the second dielectric layer 112 may contain components that are mixed in during the manufacturing process. (2-2) Conductor Layer There is no particular limitation on the material of the conductor layer.

[0062] However, as explained in connection with the dielectric layer, it is preferable that the antenna of this embodiment is a heat-resistant antenna that can be used even when heated to about 1000°C.

[0063] Therefore, the inventors of the present invention have investigated materials for the conductor layer. As a result, it has been confirmed that platinum is a material with a high melting point, corrosion resistance at high temperatures, and excellent shape and chemical stability in an environment of 1000°C. Furthermore, it has high electrical conductivity among metals with thermal stability such as stainless steel.

[0064] For this reason, it is preferable that the first conductor layer 121 and the second conductor layer 122 of the antenna of this embodiment contain platinum.

[0065] More preferably, the first conductor layer 121 and the second conductor layer 122 contain platinum as a main component.

[0066] The first conductor layer 121 and the second conductor layer 122 may be made of only platinum, but even in this case, this does not exclude the first conductor layer 121 and the second conductor layer 122 from containing components that are mixed in during the manufacturing process.

[0067] Furthermore, when the antenna of this embodiment has the third conductor layer 123, the third conductor layer 123 preferably contains platinum.

[0068] More preferably, the third conductor layer 123 contains platinum as a main component.

[0069] The third conductor layer 123 may be made of only platinum, but even in this case, it is not excluded that the third conductor layer 123 may contain components that are mixed in during the manufacturing process.

[0070] The material of each of the first conductor layer 121, the second conductor layer 122, and the third conductor layer 123 is not limited to platinum as described above. For example, the conductor layers may contain conductive powder formed by ceramic-coating metal powder. By ceramic-coating the metal powder, the conductor layers can acquire sufficient oxidation resistance. In other words, a heat-resistant antenna that can be used even when heated to approximately 1000°C can be obtained.

[0071] The material of the metal powder in the conductive powder obtained by ceramic coating a metal powder is not particularly limited, but may be one or more selected from, for example, silver, copper, and platinum. The particle size of the metal powder is also not particularly limited, and can be selected depending on the thickness of the conductor layer, etc.

[0072] The conductor layer can also be fabricated by, for example, ceramic-coating metal powder, applying a conductive paste containing conductive powder to the dielectric layer in a desired pattern, and then heat-treating the dielectric layer. The conductive paste can also be applied to the dielectric layer in a desired pattern by using, for example, a mask material.

[0073] The material of the conductor layers of the antenna of this embodiment may be different depending on the layer. For example, the material may be different between the first conductor layer 121 and the second conductor layer 122. (3) Regarding the Type of Antenna The type of the antenna of this embodiment is not particularly limited, but it is preferably a circularly polarized antenna.

[0074] When measuring an object by irradiating it with electromagnetic waves using a circularly polarized antenna, analyzing the backscattered information from the object makes it possible to obtain information about the surface roughness and dielectric constant of the object, and to estimate the phase transformation of the material and the phase fraction of the compound.In addition, since the polarization of circularly polarized waves reverses each time they are scattered, it is possible in principle to distinguish between signals scattered even times and odd times, which reduces the effects of multiple scattering when used in a closed space.

[0075] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples. [Example 1] An antenna having the cross-sectional structure shown in FIG. 3, in which the second conductor layer 122 serving as the power feed surface has the pattern shown in FIG. 2, and the third conductor layer 123 serving as the radiation surface has the pattern shown in FIG. 4, was fabricated and evaluated. (1) About the Fabricated Antenna The fabricated antenna 30 includes a first dielectric layer 111, a first conductor layer 121 serving as the ground surface disposed on the lower surface 111B of the first dielectric layer 111, and a second conductor layer 122 serving as the power feed surface disposed on the upper surface of the first dielectric layer 111. The antenna 30 further includes a second dielectric layer 112 disposed on the upper surface 122A of the second conductor layer 122, and a third conductor layer 123 disposed on the upper surface 112A of the second dielectric layer 112. The fabricated antenna 30 is a circularly polarized antenna. (1-1) First Dielectric Layer and Second Dielectric Layer A cordierite substrate made of cordierite measuring 50 mm in length, 50 mm in width, and 2 mm in thickness was used as the first dielectric layer 111 and the second dielectric layer 112. (1-2) First Conductor Layer, Second Conductor Layer, and Third Conductor Layer The first conductor layer 121, the second conductor layer 122, and the third conductor layer 123 were each a platinum layer with a thickness of 0.5 μm, and were formed by sputtering.

[0076] The second conductor layer 122 and the third conductor layer 123 were formed into the desired shapes by placing a mask based on 3D CAD data on the surface of the dielectric layer on which each conductor layer was to be formed, and then performing sputtering. The mask was removed after the conductor layers were formed. (First Conductor Layer) The first conductor layer 121 was formed over the entire lower surface 111B of the first dielectric layer 111. (Second Conductor Layer) As shown in FIG. 2 , the second conductor layer 122 has four feed patches 21, a transmission line 23, and a connection line 24 connecting the transmission line 23 and the feed patch 21.

[0077] In connection region A, transmission line 23 has a shape formed by connecting three annular sectors, with arc-shaped outer peripheries 23A and inner peripheries 23B. Transmission line 23 has width W3 at second end 232 which is shorter than width W1 at first end 231, so that W3<W2<W1.

[0078] The feed patch 21 has a shape surrounded by a contour line formed by connecting a pair of opposing vertices, vertices 25A and 25B, of a rectangle 25, specifically a square with a side length of 11.4 mm, with curves 211 and 212 connecting them. As shown in Fig. 2, the curves 211 and 212 are conic sections including one inflection point, and also include straight line portions along the contour line of the rectangle 25 near the vertices 25A and 25B of the rectangle 25. (Third Conductive Layer) The third conductor layer 123 has four radiation patches 41 as shown in Fig. 4.

[0079] The radiation patch 41 may have a shape surrounded by a contour line including a curve 421, a curve 422, a curve 423, and a curve 424, as shown in FIG.

[0080] Curves 421 and 422 are curves that connect vertices 42A and 42B, which are a pair of opposing vertices of rectangle 42, specifically a square with a side length of 11.4 mm. Curves 423 and 424 are curves that connect curves 421 and 422 near vertices 42A and 42B.

[0081] The curves 421, 422, 423, and 424 are each a conic section including one inflection point, and the sides of the rectangle 42 are tangents to the contour line of the radiation patch 41. (1-3) Regarding Connectors, etc. A 50Ω-K connector, which is a terminal 22 for external connection, was soldered to the end of the transmission line 23 of the second conductor layer 122 and to the first conductor layer 121. Next, the substrate of the second dielectric layer 112 having the third conductor layer 123 and the substrate of the first dielectric layer 111 having the first conductor layer 121 and the second conductor layer were laminated and fixed with cordierite screws and bolts to fabricate the antenna 30. (2) Regarding Evaluation (2-1) Return Loss The return loss (S １１ The parameters were measured using a network analyzer (Agilent Technologies E8364C).

[0082] FIG. 5 shows a comparison of the measurement results of the return loss and the simulation results.

[0083] S in the frequency band 51 between 4.9 GHz and 5.7 GHz １１It was confirmed that the values ​​ranged from -73.5 dB to -19.1 dB in the simulation, and from -25.9 dB to -16.5 dB in the actual measurements. That is, in the frequency band 51, in both the simulation and actual measurement results, the values ​​were below -10 dB shown by the line 52, and it was confirmed that reflections were suppressed. In addition, according to the actual measurement, that is, the result of measuring the fabricated antenna, it was confirmed that the value was -20.4 dB at the design center frequency of 5.3 GHz.

[0084] The difference between the simulation results and the actual measurements is thought to be due to factors such as the accuracy of the conductor layer deposition. However, even in the actual measurements, it was confirmed that the impedance bandwidth (IBW) was sufficiently wide at 1.73 GHz (the value obtained by dividing IBW by the center frequency is 32.6%, and it ranges from 4.74 GHz to 6.47 GHz). It was also confirmed that the impedance bandwidth of the actual measurements met the target value of 800 MHz (the value obtained by dividing IBW by the center frequency is 15.1%, and it ranges from 4.9 GHz to 5.7 GHz).

[0085] The center frequency of the actual measurement was 5.394 GHz, which was shifted to the high frequency side by about 100 MHz from the designed center frequency of 5.3 GHz. １１ The values ​​were also good, confirming that there were no problems with use at 5.3 GHz. (2-2) Axial Ratio and Gain The fabricated antenna was attached to a network analyzer, and the gain and axial ratio were measured in an anechoic chamber. In addition to the fabricated antenna, a standard dipole antenna (Candox Systems 44Sa21) with a center frequency of 5.3 GHz and a circularly polarized conical log spiral antenna (ETS-Lindgren 3102) were used to calculate the gain of the fabricated antenna using the three-antenna method. The gain was determined by comparison with an isotropic antenna.

[0086] Figure 6 shows a comparison of the measured gain and axial ratio of the fabricated antenna with the simulated results. In the frequency band 61 between 4.9 GHz and 5.7 GHz, the maximum gain was 12.0 dBic in the actual measurement and 12.8 dBic in the simulation, which were similar to the simulation results and met the target characteristic of 10 dBic or more.

[0087] In the frequency band 61 of 4.9 GHz or more and 5.7 GHz or less, the axial ratio was found to be less than 3 dB, as indicated by the straight line 62, in both the actual measurement and the simulation. Furthermore, in the actual measurement, it was confirmed that the axial ratio bandwidth (ARBW) was 1.26 GHz (the value obtained by dividing the ARBW by the center frequency was 23.7%, and the range was 4.60 GHz or more and 5.86 GHz or less). It was also confirmed that the axial ratio bandwidth in the actual measurement fully satisfied the target value of 800 MHz (the value obtained by dividing the ARBW by the center frequency was 15.1%, and the range was 4.9 GHz or more and 5.7 GHz or less).

[0088] [Example 2] An antenna was fabricated and evaluated, having the cross-sectional structure shown in Fig. 3, with the second conductor layer 122 serving as the power feeding surface having the pattern shown in Fig. 2, and the third conductor layer 123 serving as the radiation surface having the pattern shown in Fig. 4. (1) Regarding the fabricated antenna An antenna was fabricated and evaluated under the same conditions as in Example 1, except that the conductor layers, namely the first conductor layer 121, the second conductor layer 122, and the third conductor layer 123, were formed by screen printing using a conductive paste.

[0089] The conductor layer was formed by screen printing in the following manner.

[0090] Taking the first conductor layer 121 as an example, a conductive paste and a polyimide mask material were used to transfer the pattern of the first conductor layer 121 to a cordierite substrate, which is the first dielectric layer 111. The pattern was then subjected to a heat treatment process in which heat treatment was performed using an atmospheric furnace, and the first conductor layer 121 was produced.

[0091] The conductive paste used was a paste containing conductive powder made of ceramic-coated silver powder. Forming the conductive layer using a paste containing conductive powder made of ceramic-coated silver powder ensures that the conductive layer is resistant to oxidation at high temperatures, such as in a 1000°C environment. In this example, conductive powder with silver as the matrix was used as the paste material, but the ceramic coating ensured that the conductive layer had sufficient oxidation resistance at least below the sintering temperature. Because heat treatment was performed after applying the paste, screen printing allows for the inclusion of organic contaminants from the atmosphere.

[0092] The second conductor layer 122 and the third conductor layer 123 were formed into the desired shape by placing a mask based on 3D CAD data on the surface of the dielectric layer on which each conductor layer was to be formed, and then screen printing was performed using the same conductive paste as in the case of the first conductor layer 121. The mask was removed after the pattern for each conductor layer was formed. After the pattern for each conductor layer was formed, a heat treatment process was further performed in which heat treatment was performed using an atmospheric furnace.

[0093] The shapes of the first conductor layer 121, the second conductor layer 122, and the third conductor layer 123 and the sizes of each part are the same as those in Example 1, so the description will be omitted. (2) Evaluation (2-1) Return Loss The return loss (S １１ The parameters were measured using a network analyzer (Agilent Technologies E8364C).

[0094] Fig. 7 shows a comparison between the measurement results of the return loss and the simulation results. Fig. 7 also shows the results of Example 1. In Fig. 7, "Measuremento (Pt)" is the measurement result of Example 1, and "Measuremento (AgPaste)" is the measurement result of Example 2.

[0095] S in the frequency band 51 between 4.9 GHz and 5.7 GHz １１It was confirmed that the values ​​ranged from -73.5 dB to -19.1 dB in the simulation, and from -23.2 dB to -12.9 dB in the actual measurements. That is, in the frequency band 51, in both the simulation and the actual measurement results, the values ​​were below -10 dB shown by the line 52, and it was confirmed that reflections were suppressed. In addition, according to the actual measurement, that is, the result of measuring the fabricated antenna, it was confirmed that the value was -19.6 dB at the design center frequency of 5.3 GHz.

[0096] The difference between the simulation results and the actual measurements is thought to be due to factors such as the accuracy of the conductor layer deposition. However, even in the actual measurements, it was confirmed that the impedance bandwidth (IBW) was sufficiently wide at 2.02 GHz (the value obtained by dividing IBW by the center frequency is 38.1%, and it ranges from 4.66 GHz to 6.68 GHz). It was also confirmed that the impedance bandwidth of the actual measurements met the target value of 800 MHz (the value obtained by dividing IBW by the center frequency is 15.1%, and it ranges from 4.9 GHz to 5.7 GHz).

[0097] The center frequency of the actual measurement was 5.45 GHz, which was shifted to the high frequency side by about 150 MHz from the designed center frequency of 5.3 GHz. １１ The values ​​were also good, and it was confirmed that there were no problems with use at 5.3 GHz. (2-2) Axial ratio, gain

[0098] The fabricated antenna was attached to a network analyzer, and the gain and axial ratio were measured in an anechoic chamber. In addition to the fabricated antenna, a standard dipole antenna (Candox Systems 44Sa21) with a center frequency of 5.3 GHz and a circularly polarized conical log spiral antenna (ETS-Lindgren 3102) were used to calculate the gain of the fabricated antenna using the three-antenna method. The gain was determined by comparison with an isotropic antenna.

[0099] Figure 8 shows a comparison of the measurement results of the gain and axial ratio of the fabricated antenna with the simulation results. Figure 8 also shows the results of Example 1. In Figure 8, "Gain Measurement (Pt)" and "AR Measurement (Pt)" are the measurement results of Example 1 for the gain and axial ratio, respectively, and "Gain Measurement (AgPaste)" and "AR Measurement (AgPaste)" are the measurement results of Example 2 for the gain and axial ratio, respectively.

[0100] In the frequency band 61 of 4.9 GHz or more and 5.7 GHz or less, the maximum gain value was 12.4 dBic in actual measurement and 12.8 dBic in simulation, which was the same value as the simulation and satisfied the target characteristic of 10 dBic or more.

[0101] In the frequency band 61 of 4.9 GHz or more and 5.7 GHz or less, the axial ratio was found to be less than 3 dB, as indicated by the straight line 62, in both the actual measurement and the simulation. Furthermore, in the actual measurement, it was confirmed that the axial ratio bandwidth (ARBW) was 1.64 GHz (the value obtained by dividing the ARBW by the center frequency was 30.9%, and the range was 4.04 GHz or more and 5.68 GHz or less). It was also confirmed that the axial ratio bandwidth in the actual measurement fully satisfied the target value of 800 MHz (the value obtained by dividing the ARBW by the center frequency was 15.1%, and the range was 4.9 GHz or more and 5.7 GHz or less).

[0102] Although the microstrip antenna has been described above in terms of the embodiments, the present invention is not limited to the above embodiments, etc. Various modifications and changes are possible within the scope of the gist of the present invention as set forth in the claims.

[0103] This application claims priority based on Japanese Patent Application No. 2023-174164, filed with the Japan Patent Office on October 6, 2023, the entire contents of which are incorporated herein by reference.

[0104] 10 Antenna 111 First dielectric layer T111 Thickness 111A Top surface 111B Bottom surface 112 Second dielectric layer 112A Top surface 121 First conductor layer T121 Thickness 122 Second conductor layer 122A Top surface T122 Thickness 123 Third conductor layer T123 Thickness 21 Feed patch 211 Curve 212 Curve 22 Terminal 23 Transmission line 231 First end 232 Second end 23A Outer circumference 23B Inner circumference W1 Width W2 Width W3 Width 24 Connection line 25 Rectangle 25A Vertex 25B Vertex 41 Radiation patch 42 Rectangle 42A Vertex 42B Vertex 421 Curve 422 Curve 423 Curve 424 Curve A Connection area 51 Frequency band 52 Straight line 61 Frequency band 62 Straight line

Claims

1. A microstrip antenna comprising: a first dielectric layer; a first conductor layer which is a ground plane arranged on the lower surface of the first dielectric layer; and a second conductor layer which is a feed plane arranged on the upper surface of the first dielectric layer, the second conductor layer having a plurality of feed patches; and a transmission line which transmits signals between the plurality of feed patches and a terminal, the transmission line having an outer periphery which is all arc-shaped in a connection region where it is connected to the plurality of feed patches.

2. The microstrip antenna as claimed in claim 1, wherein, when an end of said transmission line along its length that is close to said terminal in said connection region is defined as a first end, and an end opposite to said first end is defined as a second end, said transmission line has a width that is shorter at said second end than at said first end.

3. A microstrip antenna as described in claim 1 or claim 2, further comprising: a second dielectric layer arranged on the upper surface of the second conductor layer; and a third conductor layer which is a radiating surface arranged on the upper surface of the second dielectric layer, the third conductor layer having a plurality of radiating patches, the radiating patches and the feeding patch having different shapes.

4. A microstrip antenna according to claim 3, wherein the length of the curved portion of the periphery of said radiation patch is longer than that of said feed patch.

5. A microstrip antenna as claimed in claim 1 or 2, wherein the first dielectric layer comprises cordierite or quartz glass, and the first conductor layer and the second conductor layer comprise platinum.

6. The microstrip antenna according to claim 1 or 2, which is a circularly polarized antenna.

Images