Converter and antenna device

Abstract

Converter (1, 1A, 1B) comprising the following: a waveguide (2); a dielectric substrate (3) coupled to one end of the waveguide on a back surface of the dielectric substrate; a conductor pattern (4, 7) provided on a front surface of the dielectric substrate and having a signal input / output connection (4b, 7b) at one end of the conductor pattern and an electrical opening (4a, 7a) which is electrically open at another end of the conductor pattern; a ground conductor (6) provided on the rear surface of the dielectric substrate; and one or more slots (5, 5A) formed in an area that is covered by one end of the waveguide in the ground conductor, wherein part of the conductor pattern is located directly above one end of the waveguide, wherein the dielectric substrate is placed between the part of the conductor pattern and one end of the waveguide, and the electrical opening is a loop pattern wherein the conductor pattern is a belt-like pattern extending from the electrical opening to the input / output terminal, and The belt-like pattern has several pattern widths, each with a different characteristic impedance.

Description

TECHNICAL FIELD

[0001] The present invention relates to a converter that performs conversion between a signal propagating in a waveguide and a signal propagating in a planar circuit, and an antenna device incorporating the converter. STATE OF THE ART

[0002] Converters are known in the art that convert a signal propagating in a waveguide to a signal propagating in a planar circuit. For example, in a converter in which a waveguide and a microstrip line are coupled, a signal propagates from the waveguide to the microstrip line, or a signal propagates from the microstrip line to the waveguide. Such a converter is widely used in an antenna device that transmits a high-frequency signal in a microwave band or a millimeter-wave band.

[0003] For example, Patent Literature 1 describes a converter including a waveguide and a multilayer substrate including a dielectric substrate and a conductor substrate. A ground plane is provided on a surface of the multilayer substrate to which the waveguide is coupled, and a conductor pattern is formed on the surface opposite the ground plane. A portion of the ground plane is opened, and a loop conductor pattern is formed on an inner layer of the multilayer substrate so as to surround the opening. By setting the width of the loop conductor pattern to a width that is an odd multiple of a quarter wavelength of the (wave)guide wavelength from one end of the opening, the loop conductor pattern functions as a choke that prevents radio waves from leaking.

[0004] A prior art converter generally prevents radio wave leakage by forming a large number of through holes that electrically couple a conductor pattern provided on the front surface of a dielectric substrate and a ground conductor provided on the back surface of the dielectric substrate. Therefore, in the converter described in Patent Literature 1, it is possible to prevent radio wave leakage without forming through holes by forming a loop conductor pattern that functions as a choke. REFERENCE LISTPATENT LITERATURE

[0005] Patent Literature 1: JP 2017-85420 A

[0006] US 20040041651 A1 provides a waveguide / planar line converter comprising a housing having a waveguide and a waveguide / planar line conversion substrate having a signal line propagating high-frequency signals formed on one main surface side and a ground formed on the other main surface side, wherein an end portion of the signal line of the waveguide / planar line conversion substrate is arranged to protrude into the waveguide.

[0007] CN 106549203 A discloses a conversion circuit from a coupled microstrip line to a rectangular waveguide. The conversion circuit is a coupling probe, and the coupling probe is a rectangular metal strip with a circular groove in the center. The circular groove communicates with a rectangular groove between two conductors of a coupled microstrip line. The rectangular metal strip at the edge of the circular groove communicates with the two conductors of the coupled microstrip line. The circular groove and the rectangular metal strip outside the circular groove form a groove ring and a metal strip ring of the coupling probe. The operating frequency is determined by the resonant frequency of the microstrip ring and the resonant frequency of the groove ring. The coupling probe extends vertically into a rectangular waveguide to realize the coupling. SUMMARY OF THE INVENTIONTECHNICAL PROBLEM

[0008] In the converter described in Patent Literature 1, there is a disadvantage that miniaturization is limited because the conductor pattern having a width set to an odd multiple of a quarter wavelength of the (wave)guide wavelength from one end of the opening is formed so as to surround the opening of the ground plate.

[0009] Furthermore, in the converter described in Patent Literature 1, when the loop conductor pattern is removed for miniaturization, a conductor pattern remains that has a length of a quarter wavelength of the guide wavelength immediately above the waveguide. Since this conductor pattern has an open end, unwanted radio waves are emitted from the open end.

[0010] This invention solves the above disadvantages, and it is an object of the invention to obtain a converter which is miniaturized and suppresses unwanted emission of radio waves, and to obtain an antenna device incorporating the converter. SOLUTION TO THE PROBLEM

[0011] The invention is defined in independent claim 1.

[0012] A converter according to the present invention specifically includes a waveguide, a dielectric substrate, a conductor pattern, a ground conductor, and one or more slots. The dielectric substrate is coupled to one end of the waveguide on a back surface of the dielectric substrate. The conductor pattern is provided on a front surface of the dielectric substrate and has a signal input / output terminal at one end of the conductor pattern and an electrical opening electrically opened at another end of the conductor pattern. The ground conductor is provided on the back surface of the dielectric substrate. The slots are formed in an area covered by one end of the waveguide in the ground conductor.In this embodiment, a portion of the conductor pattern is located immediately above one end of the waveguide, the dielectric substrate is disposed between the portion of the conductor pattern and one end of the waveguide, and the electrical opening is a loop pattern. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0013] According to the present invention, which includes the electrical opening, which is a loop pattern, at one end of the conductor pattern located immediately above one end of the waveguide, with the dielectric substrate interposed therebetween, there is no need to provide the choke structure described in Patent Literature 1, and thus it is possible to implement a smaller converter. Furthermore, since the electrical opening is the loop pattern, it is possible to prevent radio wave leakage even without a choke. This enables miniaturization and suppression of unexpected radio wave emission. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view illustrating a configuration of a converter according to a first embodiment of the invention. Fig. Fig. 2 is a cross-sectional arrow view showing a cross section of the converter according to the first embodiment along a line AA in Fig. 1 illustrates. Fig. 3 is a perspective view illustrating a waveguide in the first embodiment. Fig. 4 is a view illustrating a conductor pattern in the first embodiment. Fig. 5 is a view illustrating a ground conductor with a rectangular slot in the first embodiment. Fig. 6 is a view illustrating a ground conductor having an H-shaped slot in the first embodiment. Fig. 7 is a graph illustrating an analysis result of an electromagnetic field of undesirable emission characteristics of the converter. Fig. 8 is a plan view illustrating a configuration of a converter according to a second embodiment of the invention. Fig. 9 is a view illustrating the front side of the converter according to the second embodiment. Fig. 10 is a plan view illustrating a configuration of a converter according to a third embodiment of the invention. Fig. 11 is a view illustrating the front side of the converter according to the third embodiment. Fig. 12 is a view illustrating the front side of a modification of the converter according to the third embodiment. Fig. 13 is a view illustrating the front side of another modification of the converter according to the third embodiment. Fig. 14 is a graph illustrating analysis results of an electromagnetic field of undesired emission characteristic of the converter according to the second embodiment and the converter according to the third embodiment. DESCRIPTION OF EMBODIMENTS

[0014] In order to further describe the present invention in detail, embodiments for carrying out the invention will be described below with reference to the accompanying drawings. First embodiment

[0015] Fig. 1 is a plan view illustrating a configuration of a converter 1 according to a first embodiment of the invention. Fig. 2 is a cross-sectional arrow view showing a cross section of the converter 1 along a line AA in Fig. 1. The x-axis, y-axis, and z-axis illustrated in the drawings are three mutually orthogonal axes. A direction parallel to the x-axis is called an x-axis direction, a direction parallel to the y-axis is called a y-axis direction, and a direction parallel to the z-axis is called a z-axis direction. In an x-axis direction, an arrow direction is called a positive x-direction, and a direction opposite to the positive x-direction is called a negative x-direction. In a y-axis direction, an arrow direction is called a positive y-direction, and a direction opposite to the positive y-direction is called a negative y-direction. In a z-axis direction, an arrow direction is called a positive z-direction, and a direction opposite to the positive z-direction is called a negative z-direction.A rotation angle in the xy-plane from the x-axis to the y-axis around the z-axis is called Φ and a rotation angle in the zx-plane from the z-axis to the x-axis around the y-axis is called θ.

[0016] The converter 1 performs a conversion between a signal propagating in a waveguide 2 and a signal propagating in a planar circuit containing a conductor pattern 4. As shown in Fig. 1 and Fig. 2, the converter 1 includes the waveguide 2, a dielectric substrate 3, a conductor pattern 4, a slot 5, and a ground conductor 6.

[0017] The waveguide 2 is a hollow waveguide, one end of which is coupled to the dielectric substrate 3. In the dielectric substrate 3, the waveguide 2 is coupled to the back surface, and the conductor pattern 4 is formed on the front surface. The dielectric substrate 3 is a flat plate member made of a resin material. The dielectric substrate 3 may be a single-layer substrate, but may be a multilayer dielectric substrate in which multiple dielectric substrates and a conductor substrate are laminated.

[0018] The conductor pattern 4 is a belt-like pattern in which an input / output terminal 4b is provided at one end and an electrical opening 4a is provided at the other end. The conductor pattern 4 is formed, for example, by pressure-bonding a conductive metal foil (such as a copper foil) to the front surface of the dielectric substrate 3, thereby patterning the metal foil. The conductor pattern 4 can be formed by attaching a patterned metal plate to the front surface of the dielectric substrate 3. A signal is input to or output from the input / output terminal 4b. The electrical opening 4a is a loop conductor pattern and is electrically open.

[0019] A part of the conductor pattern 4 is located directly above one end of the waveguide 2, with the dielectric substrate 3 sandwiched therebetween, as shown in Fig. 1. On the back surface of the dielectric substrate 3, the ground conductor 6 is formed on the entire surface, as shown in Fig. 2. The slot 5 is formed in an area covered by one end of the waveguide 2 in the ground conductor 6.

[0020] A part of the conductor pattern 4 is located directly above the slot 5, with the dielectric substrate 3 sandwiched therebetween.

[0021] It should be noted that, in Fig. 1 and Fig. 2, the conductor pattern 4 provided on the front surface of the dielectric substrate 3, together with the ground conductor 6, forms a microstrip line. However, the conductor pattern 4, together with the ground conductor 6, can form any stripline, a coplanar line, or a coplanar line with an attached ground conductor.

[0022] Fig. 3 is a perspective view illustrating the waveguide 2. As shown in Fig. 3, the waveguide 2 is a hollow metal tube having metallic tube walls. An xy-cross section of the waveguide 2 is a rectangle having a long side parallel to the y-axis and a short side parallel to the x-axis, as indicated by a dashed line in Fig. 1. The waveguide 2 is connected to the ground conductor 6 at an opening edge b, in Fig. 2, and is electrically short-circuited.

[0023] It should be noted that the waveguide 2 can have any desired configuration. For example, the waveguide 2 can be a tube filled with a dielectric. The waveguide 2 can be a tube having a tubular wall in which, instead of a metallic tube wall, several through-holes are formed, the tube being filled with a dielectric. The waveguide 2 can have a shape in which the corners of a rectangle, i.e., an xy cross-section, are rounded, or it can be a ridge waveguide.

[0024] The position at which the electrical opening 4a is formed is 0 times or an integer multiple, greater than or equal to 1, a half-wavelength of a (wave)guide wavelength away from a position a immediately above the waveguide 2 with the dielectric substrate 3 interposed therebetween in the negative x-direction. It should be noted that the position a is immediately above the center of the opening of the waveguide 2 with the dielectric substrate 3 interposed therebetween. In the example of Fig. 1, the electrical opening 4a is formed from a position immediately above the waveguide 2 with the dielectric substrate 3 sandwiched therebetween in the negative x-direction (on the side opposite to the input / output terminal 4b) by 0 times a half wavelength of the (wave)guide wavelength, that is, the electrical opening 4a is formed from the position a.

[0025] The electrical opening 4a is a loop pattern whose total circumferential length is obtained by multiplying a half-wavelength of the conductor wavelength by a natural number greater than or equal to 1. Since the electrical opening 4a is a loop pattern and there is no opening at the end, it is possible to suppress emission of unwanted radio waves.

[0026] In order to suppress leakage of unwanted radio waves without forming a large number of through holes, the loop conductor pattern in the converter described in Patent Literature 1, which has a width set to an odd multiple of a conductor wavelength, is provided from one end of the slot as a choke.

[0027] Therefore, in the converter 1 according to the first embodiment, a loop conductor pattern acting as a choke is unnecessary because the electrical opening 4a is included. For example, the conductor pattern 4 does not include a portion surrounding the slot 5, and thus the dimension in the y-direction is reduced compared to the converter described in Patent Literature 1. As a result, the converter 1 can be miniaturized compared to prior art converters as described above.

[0028] In the example of Fig. 1, the electrical opening 4a is a loop pattern of an equilateral triangle, including a bent portion 4a-1 and a bent portion 4a-2. The triangle has a loop shape whose total circumference is three-half the conductor wavelength; in other words, one side has a length of half a wavelength of the conductor wavelength. The bent portion 4a-1 and the bent portion 4a-2 are formed by bending the conductor pattern at positions each having a length of half a wavelength of the conductor wavelength. As a result, each of the bent portion 4a-1 and the bent portion 4a-2 is a node of the electric field and basically has no energy, and thus unwanted radio wave emission is unlikely to occur.

[0029] It should be noted that the electrical opening 4a, which is a triangular loop pattern, is merely an example and may be a polygonal loop pattern having four or more sides or a smoothly curved loop pattern.

[0030] It should be noted that although a part of the pattern width of the electrical opening 4a in Fig. 1 has a so-called tapered shape in which the pattern width decreases from the position a to the bent portions 4a-1 and 4a-2, wherein the pattern width of the electrical opening 4a may be of any type.

[0031] Fig. 4 is a view illustrating the conductor pattern 4. As shown in Fig. As illustrated in FIG. 4, the conductor pattern 4 includes stubs 4c, a conversion section 4d, and impedance conversion sections 4e to 4g, in addition to the electrical opening 4a and the input / output terminal 4b. The stubs 4c and the impedance conversion sections 4e to 4g function as a matching element that matches the impedance of the conversion section 4d and the impedance of the waveguide 2, that is, as a matching element that performs reflection matching.

[0032] The stub lines 4c are a conductor pattern extending in the positive y-direction of the conversion section 4d and a conductor pattern extending in the negative y-direction of the conversion section 4d, and are provided immediately above the slot 5 with the dielectric substrate 3 sandwiched therebetween, as shown in Fig. 1. The length of each of the stub lines 4c, which extend linearly from the conversion section 4d in the positive y-direction and the negative y-direction, corresponds to the length of a quarter wavelength of the waveguide wavelength. Note that the end of the stub lines 4c is open.

[0033] The conversion section 4d and the impedance conversion sections 4e to 4g each have a characteristic impedance corresponding to their pattern width. The conversion section 4d has a characteristic impedance Z 4d corresponding to the pattern width, and the impedance conversion section 4e has a characteristic impedance Z 4e which corresponds to the pattern width. The conversion section 4f has a characteristic impedance Z 4f corresponding to the pattern width, and the impedance conversion section 4g has a characteristic impedance Z 4gcorresponding to the pattern width. The input / output terminal 4b has a characteristic impedance Z 4b which corresponds to the pattern width.

[0034] If the input / output terminal 4b and the conversion section 4d are formed close to each other, unwanted emission of radio waves increases due to mismatch between the characteristic impedance Z 4b of the input / output terminal 4b and the characteristic impedance Z 4d of the conversion section 4d, thereby increasing the power loss. Therefore, in the conductor pattern 4 in the first embodiment, the impedance conversion sections 4e to 4g perform impedance matching between the conversion section 4d and the input / output terminal 4b.

[0035] The characteristic impedance Z 4e of the impedance conversion section 4e is smaller than the characteristic impedance Z 4bof the input / output terminal 4b and greater than the characteristic impedance Z 4d of the conversion section 4d. This means that a relationship Z 4d < Z 4e < Z 4b applies.

[0036] The characteristic impedance Z 4f of the impedance conversion section 4f is equal to the characteristic impedance Z 4b of the input / output terminal 4b and greater than the characteristic impedance Z 4e of the impedance conversion section 4e. and thus a relationship Z 4e < Z 4f < Z 4b .

[0037] The characteristic impedance Z 4g of the impedance conversion section 4g is smaller than each of the characteristic impedance Z 4f of the impedance conversion section 4f and the characteristic impedance Z 4b of the input / output terminal 4b and greater than the characteristic impedance Z 4eof the impedance conversion section 4e. A relationship Z applies 4e < Z 4g < Z 4f = Z 4b .

[0038] The converter 1 according to the first embodiment includes the impedance conversion section 4e and the impedance conversion section 4g, which have larger pattern widths than that of the input / output terminal 4b. With this configuration, impedance matching is performed between the conversion section 4d and the input / output terminal 4b, thereby reducing power loss. Note that the stubs 4c, the conversion section 4d, and the impedance conversion sections 4e to 4g illustrated in Fig. 4, examples are and the number of stubs 4c and the number of stages of the impedance conversion sections can be modified depending on the reflection matching conditions.

[0039] Fig. Fig. 5 is a view illustrating the ground conductor 6 having the slot 5 with a rectangular shape. The slot 5 is formed in an area covered by one end of the waveguide 2 in the ground conductor 6, that is, the area is surrounded by the opening edge b. The case is in Fig. 1 to Fig. 5 illustrates a circuit in which only one slot 5 is formed in the area surrounded by the opening edge b; however, multiple slots 5 may be formed in the area surrounded by the opening edge b. The ground conductor 6 is formed, for example, by pressure-bonding a conductive metal foil (such as a copper foil) to the back surface of the dielectric substrate 3. The ground conductor 6 may be formed by attaching a metal plate to the back surface of the dielectric substrate 3.

[0040] Fig. Fig. 6 is a view illustrating the ground conductor 6 with an H-shaped slot 5A. The rectangular slot 5 has been described; however, the H-shaped slot 5A may be provided in the ground conductor 6 instead of the slot 5A shown in Fig. 6. Also, in this case, the slot 5A is formed in the area covered by one end of the waveguide 2 in the ground conductor 6, that is, the area surrounded by the opening edge b.

[0041] Next, the operation is described.

[0042] For example, when a fundamental mode signal is input from the waveguide 2, the input signal is coupled into the slot 5 formed in the ground conductor 6. The signal coupled to the slot 5 is coupled to the conductor pattern 4. The electrical opening 4a is a loop pattern whose total circumferential length is obtained by multiplying half the guide wavelength by a natural number greater than or equal to 1 (in Fig. 2 a total circumferential length of three-half the conductor wavelength). For this reason, the signal coupled to the conductor pattern 4 is completely reflected by the electrical opening 4a and propagates toward the input / output terminal 4b.

[0043] Next, the effectiveness of the structure of the converter 1 according to the first embodiment will be described.

[0044] Fig. Figure 7 is a graph illustrating analysis results of an electromagnetic field with undesired emission characteristics of the converter 1 and a conventional converter. Fig. 7, the horizontal axis represents the angle of rotation θ from the z-axis to the x-axis around the y-axis in the zx-plane, and the vertical axis represents the emission strength (gain) of unwanted radio waves as a function of the angle of rotation Φ from the x-axis to the y-axis around the z-axis in the xy-plane. Fig. Figure 7 shows the emission intensity of unwanted radio waves between θ = -90 (degrees) and +90 (degrees) for Φ = 0 (degrees).

[0045] Data D1 indicated by a solid line indicate undesirable emission characteristics obtained by analyzing the electromagnetic field of the structure of the converter 1, illustrated in Fig. 1 and Fig. 2. Data D2 indicated by a broken line indicate unwanted emission characteristics obtained by analyzing the electromagnetic field of the conventional converter, which does not include the electrical opening 4a or the stub lines 4c among the components of the converter 1. As shown in Fig. As shown in Figure 7, the maximum emission intensity of unwanted radio waves in the conventional converter at Φ = 0 (degrees) is -2 (dB) for θ = -60 (degrees). On the other hand, the maximum emission intensity of unwanted radio waves in the converter 1 at Φ = 0 (degrees) is -6.54 (dB) for θ = -60 (degrees). The emission intensity of unwanted radio waves is improved by ΔG = 4.54 (dB). Note that this efficiency is similar to that of a converter of a second embodiment and a third embodiment described later.

[0046] As described above, the converter 1 according to the first embodiment includes the electrical opening 4a, which is a loop pattern, at one end of the conductor pattern 4 located immediately above one end of the waveguide 2, with the dielectric substrate 3 sandwiched between one end of the conductor pattern 4 and one end of the waveguide 2. Therefore, the converter 1 does not require the choke structure described in Patent Literature 1 and can thus be miniaturized. Since the electrical opening 4a is the loop pattern, it is possible to prevent radio wave leakage even without a choke. As a result, the converter 1 can be miniaturized and suppresses unwanted radio wave emission.

[0047] In the converter 1 according to the first embodiment, the conductor pattern 4 is a belt-like pattern extending from the electrical opening 4a to the input / output terminal 4b. The belt-like pattern has multiple pattern widths, each with a different characteristic impedance. This allows the impedance in the belt-like pattern to be adjusted, thereby mitigating power loss.

[0048] In the converter 1 according to the first embodiment, the electrical opening 4a is a loop pattern whose total circumferential length is obtained by multiplying a half-wavelength of the guide wavelength by a natural number greater than or equal to 1. For example, the electrical opening 4a is a loop pattern in the shape of an equilateral triangle, each side of which has a length of a half-wavelength of the guide wavelength, and is a loop pattern having the same pattern width or a loop pattern having partially different pattern widths. Since there is no opening at the end of the electrical opening 4a, it is possible to suppress emission of unwanted radio waves. Since the choke having a length that is an odd multiple of a quarter-wavelength of the guide wavelength is not required, the converter 1 can be further miniaturized. Second embodiment

[0049] Fig. Fig. 8 is a plan view illustrating a configuration of a converter 1A according to a second embodiment of the invention. Fig. Fig. 9 is a view illustrating the front side of the converter 1A according to the second embodiment. The converter 1A performs conversion between a signal propagating in a waveguide 2 and a signal propagating in a planar circuit including a conductor pattern 7.

[0050] Signal through. As in Fig. 8 and Fig. 9, the converter 1A includes the waveguide 2, a dielectric substrate 3, a slot 5, the conductor pattern 7, a floating conductor 8a and a floating conductor 8b; and a ground conductor 6 is provided on the back surface of the dielectric substrate 3, as shown in Fig. 2. As in Fig. 8, a position a is located directly above the center of an opening of the waveguide 2 with the dielectric substrate 3 sandwiched therebetween. As shown in Fig. As illustrated in Figure 9, c denotes the pattern width of a conversion section 7c. The floating conductor 8a and the floating conductor 8b are rectangular conductor patterns, each having a length of L2 in the y-axis direction and a length of L3 in the x-axis direction.

[0051] The conductor pattern 7 includes the conversion section 7c and an impedance conversion section 7d, in addition to an electrical opening 7a and an input / output terminal 7b. Portions of the floating conductor 8a and the floating conductor 8b are located immediately above one end of the waveguide 2 with the dielectric substrate 3 sandwiched therebetween, and are also located immediately above the slot 5 with the dielectric substrate 3 sandwiched therebetween. Each of the floating conductor 8a and the floating conductor 8b is separated from the conversion section 7c by a distance L1, as shown in Fig. 9. The potential-free conductor 8a and the potential-free conductor 8b are in a symmetrical positional relationship with respect to the x-axis, which passes through position a. Furthermore, L3 is longer than L2, and L2 is longer than L1.

[0052] The electrical opening 7a is a loop pattern whose total circumferential length is obtained by multiplying a half-wavelength of the guide wavelength by a natural number greater than or equal to 1. Furthermore, since the electrical opening 7a is a loop pattern and there is no opening at the end, it is possible to suppress the emission of unwanted radio waves. By providing the electrical opening 7a, a reactor described in Patent Literature 1, which has a pattern width that is an odd multiple of a quarter-wavelength of the guide wavelength, is unnecessary. For this reason, the converter 1A can be miniaturized compared with converters in the prior art.

[0053] In Fig. 8 and Fig. 9, the electrical opening 7a is a loop pattern of an equilateral triangle, including a bent portion 7a-1 and a bent portion 7a-2. In this triangle, one side has a length of one half wavelength of the conductor wavelength, and the entire circumference has a length of three halves of the conductor wavelength. The bent portion 7a-1 and the bent portion 7a-2 are formed by bending the conductor pattern at positions each having a length of half wavelength of the conductor wavelength. As a result, each of the bent portion 7a-1 and the bent portion 7a-2 is a node of the electric field and basically has no energy, and thus, unwanted radio wave emission is unlikely to occur.

[0054] It should be noted that the electrical opening 7a, which is a triangular loop pattern, is merely an example and may be a polygonal loop pattern having four or more sides or a smoothly curved loop pattern.

[0055] Although a pattern in which a part of the pattern width of the electric opening 7a is tapered has been illustrated as an example, the pattern width of the electric opening 7a may be set arbitrarily.

[0056] In the converter 1 according to the first embodiment, the position of the electrical opening 4a is spaced from the position a immediately above the waveguide 2 with the dielectric substrate 3 sandwiched therebetween by 0 times a half-wavelength of the (wave)guide wavelength. Therefore, in the converter 1A according to the second embodiment, the position of the electrical opening 7a is formed at a position away from the position a immediately above the waveguide 2 with the dielectric substrate 3 sandwiched therebetween by a half-wavelength of the (wave)guide wavelength.

[0057] In the converter 1 according to the first embodiment, the stub lines 4c and the impedance conversion sections 4e to 4g equalize the characteristic impedance Z 4d of the conversion section 4d and the characteristic impedance Z 4bof the input / output terminal 4b. In contrast, in the converter 1A according to the second embodiment, the impedance conversion section 7d, the floating conductor 8a, and the floating conductor 8b equalize the characteristic impedance of the conversion section 7c and the characteristic impedance of the input / output terminal 7b.

[0058] Since the floating conductor 8a and the floating conductor 8b are separated from the conversion section 7c by a distance L1, a parasitic capacitance or parasitic inductance is introduced into the conversion section 7c. This makes it possible to mitigate a rapid change in impedance between the conversion section 7c and the input / output terminal 7b, thereby allowing the converter 1A to effectively reduce power loss.

[0059] It should be noted that the converter 1A according to the second embodiment can mitigate a rapid change in impedance between the converting section 7c and the input / output terminal 7b and thus can handle a wideband signal.

[0060] The shape of the potential-free conductors 8a and 8b, illustrated in Fig. 8 and Fig. 9, is an example and can be a polygonal shape of any polygon having five or more sides or a gently curved shape.

[0061] As described above, the converter 1A according to the second embodiment includes the floating conductor 8a and the floating conductor 8b provided on the front surface of the dielectric substrate 3. A part of each of the floating conductor 8a and the floating conductor 8b is located immediately above one end of the waveguide 2 with the dielectric substrate 3 sandwiched therebetween. With this configuration, effects similar to those of the first embodiment can be obtained. Furthermore, since a sudden change in impedance between the converting section 7c and the input / output terminal 7b in the conductor pattern 7 is mitigated, it is possible to handle a broadband signal. Third embodiment

[0062] Fig. 10 is a plan view illustrating a configuration of a converter 1B according to a third embodiment of the invention. Fig. Figure 11 is a view illustrating the front side of the converter 1B according to the third embodiment. The converter 1B performs conversion between a signal propagating in a waveguide 2 and a signal propagating in a planar circuit including a conductor pattern 7. As shown in Fig. 10 and Fig. 11, the converter 1B includes the waveguide 2, a dielectric substrate 3, a slot 5, the conductor pattern 7, a floating conductor 8a and a floating conductor 8b; and a ground conductor 6 is provided on the back surface of the dielectric substrate 3, as in the embodiment shown in Fig. 2 illustrated converter 1. As in Fig. 10, a position a is located directly above the center of an opening of the waveguide 2 with the dielectric substrate 3 sandwiched therebetween. In Fig. 11, c denotes the pattern width of a conversion section 7c. The potential-free conductor 8a and the potential-free conductor 8b are rectangular conductor patterns, each having a length of L2 in the y-axis direction and a length of L3 in the x-axis direction.

[0063] In the converter 1A according to the second embodiment, as shown in Fig. As illustrated in Figure 9, the floating conductor 8a and the floating conductor 8b are rectangular conductor patterns, each having a length of L2 in the y-axis direction and a length of L3 in the x-axis direction. In contrast, the floating conductor 8a and the floating conductor 8b included in the converter 1B according to the third embodiment include rectangular cutout portions 9a and cutout portions 9b as parts thereof, as shown in Figure 9. Fig. 11. Each of the two cutout portions 9a and the two cutout portions 9b is arranged on the same straight line along the longitudinal direction (y-axis direction) of the slot 5 with the dielectric substrate 3 sandwiched therebetween.

[0064] The conductor pattern 7 includes the conversion section 7c and an impedance conversion section 7d, in addition to an electrical opening 7a and an input / output terminal 7b. Portions of the floating conductor 8a and the floating conductor 8b are located immediately above one end of the waveguide 2 with the dielectric substrate 3 sandwiched therebetween, and are also located immediately above the slot 5 with the dielectric substrate 3 sandwiched therebetween. Each of the floating conductor 8a and the floating conductor 8b is separated from the conversion section 7c by a distance L1, as shown in Fig. 11. The potential-free conductor 8a and the potential-free conductor 8b are in a symmetrical positional relationship with respect to the x-axis, which passes through position a. Furthermore, L3 is longer than L2, and L2 is longer than L1.

[0065] The electrical opening 7a is a loop pattern whose total circumferential length is obtained by multiplying a half-wavelength of the guide wavelength by a natural number greater than or equal to 1. Furthermore, since the electrical opening 7a is a loop pattern and there is no opening at the end, it is possible to suppress the emission of unwanted radio waves. By providing the electrical opening 7a, a reactor described in Patent Literature 1, which has a pattern width that is an odd multiple of a quarter-wavelength of the guide wavelength, is unnecessary. For this reason, the converter 1A can be miniaturized compared with converters in the prior art.

[0066] In Fig. 10 and Fig. 11, the electrical opening 7a is a loop pattern of an equilateral triangle, including a bent portion 7a-1 and a bent portion 7a-2. In this triangle, one side has a length of one half wavelength of the conductor wavelength, and the entire circumference has a length of three halves of the conductor wavelength. The bent portion 7a-1 and the bent portion 7a-2 are formed by bending the conductor pattern at positions each having a length of half wavelength of the conductor wavelength. As a result, each of the bent portion 7a-1 and the bent portion 7a-2 is a node of the electric field and basically has no energy, and thus, unwanted radio wave emission is unlikely to occur.

[0067] Note that although the structure in which the electrical opening 7a is a triangular loop pattern is illustrated, this is an example, and the electrical opening 7a may be a polygonal loop pattern composed of any polygon having four or more sides or a smoothly curved loop pattern. Furthermore, although a pattern in which a portion of the pattern width of the electrical opening 7a is tapered was illustrated as an example, the pattern width of the electrical opening 7a may be set arbitrarily.

[0068] In the converter 1 according to the first embodiment, the position of the electrical opening 4a is spaced from the position a immediately above the waveguide 2, with the dielectric substrate 3 sandwiched therebetween, by 0 times a half-wavelength of the (wave)guide wavelength. Therefore, in the converter 1B according to the third embodiment, the position of the electrical opening 7a is formed at a position a immediately above the waveguide 2, with the dielectric substrate 3 sandwiched therebetween, by a half-wavelength of the (wave)guide wavelength.

[0069] In the converter 1 according to the first embodiment, the stub lines 4c and the impedance conversion sections 4e to 4g equalize the characteristic impedance Z 4d of the conversion section 4d and the characteristic impedance Z 4bof the input / output terminal 4b. In contrast, in the converter 1B according to the third embodiment, the impedance conversion section 7d, the floating conductor 8a, and the floating conductor 8b equalize the characteristic impedance of the conversion section 7c and the characteristic impedance of the input / output terminal 7b.

[0070] Each of the cutout portions 9a included in the floating conductor 8a and the cutout portions 9b included in the floating conductor 8b is arranged at a position where the electric field is a node on the floating conductor. With the cutout portions 9a and 9b, the current that has been widely distributed around the ends of the floating conductor 8a and 8b is concentrated at the cutout portions 9a and 9b. Since a current flows in opposite directions along the two sides in the y-axis direction in each of the rectangular cutout portions 9a and 9b, and the distance between the two sides is shorter than the wavelength, much of the emission caused by the current is extinguished.Furthermore, the current flowing along one side in the x-axis direction of each of the rectangular cutout sections 9a and cutout sections 9b is not efficiently emitted into space because that side is shorter than the wavelength. Based on the above principles, the cutout sections 9a and cutout sections 9b included in the floating conductor 8a and the floating conductor 8b can suppress unwanted emissions.

[0071] The shape of the potential-free conductor 8a and the potential-free conductor 8b, shown in Fig. 10 and Fig. 11, is an example of a potential-free conductor in which rectangular cutouts are included in parts of the rectangular conductor. Fig. 12 and Fig. 13 are views illustrating the front side of a modification of the converter 1B according to the third embodiment. The floating conductor 8a and the floating conductor 8b may have a polygonal shape of a polygon having five or more sides, as shown in Fig. 12, or may have a shape that partially has a softly curved contour, as in Fig. 13. Furthermore, the shape of the cutout sections 9a and the cutout sections 9b, illustrated in Fig. 10 to Fig. 13, also an example and may have a shape of a polygon having three or more sides or a shape with a gently curved contour.

[0072] Next, the effectiveness of the structure of the converter 1B according to the third embodiment will be described.

[0073] Fig. 14 is a graph illustrating analysis results of an electromagnetic field of undesirable emission characteristics of the converter 1A according to the second embodiment and the converter 1B according to the third embodiment. In Fig. 14, the horizontal axis represents the angle of rotation θ from the z-axis to the x-axis around the y-axis in the zx-plane, and the vertical axis represents the emission strength (gain) of unwanted radio waves as a function of the angle of rotation Φ from the x-axis to the y-axis around the z-axis in the xy-plane. Fig. Figure 14 shows the emission intensity of unwanted radio waves between θ = -90 (degrees) and +90 (degrees) for Φ = 0 (degrees).

[0074] In Fig. 14, data D4 indicated by a solid line indicate undesired emission characteristics obtained by analyzing the electromagnetic field of the structure of the converter 1B, illustrated in Fig. 10 and Fig. 11. Data D3 indicated by a broken line indicate undesired emission characteristics obtained by analyzing the electromagnetic field of the structure of the converter 1A, illustrated in Fig. 8 and Fig. 9. In converter 1A, the maximum emission intensity of unwanted radio waves at Φ = 0 (degrees) is -5.13 (dB) for θ = 0 (degrees). On the other hand, the maximum emission intensity of unwanted radio waves in converter 1B at Φ = 0 (degrees) is -8.10 (dB) for θ = 0 (degrees). The emission intensity of unwanted radio waves is improved by ΔG1 = 2.97 (dB) in converter 1B.

[0075] As described above, the converter 1B according to the third embodiment includes the rectangular cutout portions 9a and 9b provided in respective parts of the floating conductor 8a and the floating conductor 8b provided on the front surface of the dielectric substrate 3. The cutout portions 9a and 9b are arranged on the same straight line along the longitudinal direction (y-axis direction) of the slot 5 with the dielectric substrate 3 sandwiched therebetween. With this configuration, similar effects to those of the first embodiment can be obtained, and emission from the floating conductor 8a and the floating conductor 8b can be further reduced.

[0076] The converter 1 according to the first embodiment, the converter 1A of the second embodiment, and the converter 1B according to the third embodiment can be mounted on one antenna device. Since each of the converter 1, the converter 1A, and the converter 1B can be miniaturized, it is also possible to miniaturize an antenna device including any one of them.

[0077] It should be noted that the present invention is not limited to the above embodiments, and the present invention may include a flexible combination of the individual embodiments, a modification of any component of the individual embodiments, or an omission of any component in the individual embodiments within the scope of the present invention. INDUSTRIAL APPLICABILITY

[0078] A converter according to the present invention is miniaturized and can suppress unwanted emissions of radio waves and thus can be used, for example, in an in-vehicle antenna device. LIST OF REFERENCE SYMBOLS

[0079] 1, 1A, 1B: Converter, 2: Waveguide, 3: Dielectric substrate, 4, 7: Conductor pattern, 4a, 7a: Electrical opening, 4a-1, 4a-2, 7a-1, 7a-2: Bent section, 4b, 7b: Input / output terminal, 4c: Stub line, 4d, 7c: Converter section, 4e to 4g, 7d: Impedance conversion section, 5, 5A: Slot, 6: Ground conductor, 8a, 8b: Floating conductor, 9a, 9b: Cutout section

Claims

[1] Converter (1, 1A, 1B) comprising: a waveguide (2); a dielectric substrate (3) coupled to one end of the waveguide on a back surface of the dielectric substrate; a conductor pattern (4, 7) provided on a front surface of the dielectric substrate and having a signal input / output terminal (4b, 7b) at one end of the conductor pattern and an electrical opening (4a, 7a) electrically opened at another end of the conductor pattern; a ground conductor (6) provided on the back surface of the dielectric substrate; and one or more slots (5, 5A) formed in an area covered by one end of the waveguide in the ground conductor, wherein a part of the conductor pattern is located immediately above one end of the waveguide, the dielectric substrate being sandwiched between the part of the conductor pattern and one end of the waveguide, and the electrical opening is a loop pattern, wherein the conductor pattern is a belt-like pattern extending from the electrical opening to the input / output terminal, and the belt-like pattern has several pattern widths, each with a different characteristic impedance. [2] The converter of claim 1, further comprising: at least one potential-free conductor (8a, 8b) provided on the front surface of the dielectric substrate, wherein a portion of the potential-free conductor is located immediately above one end of the waveguide, wherein the dielectric substrate is sandwiched between the portion of the potential-free conductor and one end of the waveguide. [3] The converter according to claim 1, wherein the conductor pattern forms a microstrip line or a stripline or a coplanar line or a coplanar line with the ground conductor. [4] A converter according to claim 1, wherein the electrical opening is positioned from a position (a) immediately above the one end of the waveguide, the dielectric substrate being sandwiched between the position and the one end of the waveguide, to a side opposite the input / output terminal by 0 times or an integer multiple, greater than or equal to 1, of a half wavelength of a guide wavelength. [5] The converter according to claim 1, wherein the electrical opening is a loop pattern whose total circumferential length is obtained by multiplying a half wavelength of a guide wavelength by a natural number greater than or equal to 1. [6] The converter of claim 1, wherein the electrical opening is a triangular loop pattern, at least one side of which has a length of a half wavelength of a guide wavelength. [7] The converter according to claim 1, wherein the electrical opening is a loop pattern having a same pattern width or a loop pattern having different pattern widths. [8] The converter according to claim 2, wherein the floating conductor is a rectangular pattern or a polygonal pattern. [9] Converter according to claim 2 or 8, wherein the potential-free conductor includes at least one or more cutout sections (9a, 9b), and the cutout portions are arranged on a straight line along a longitudinal direction of the slot, wherein the dielectric substrate is interposed between the cutout portions and the slot. [10] A converter according to claim 1, wherein the slot has a rectangular shape (5) or is H-shaped (5A). [11] The converter according to claim 1, wherein the dielectric substrate is a multilayer dielectric substrate comprising a plurality of substrates. [12] A converter according to claim 1, wherein the waveguide is a hollow waveguide having a metallic tube wall. [13] A converter according to claim 1, wherein the waveguide comprises a metallic tube wall and is partially filled with a dielectric or comprises a tube wall in which a plurality of through-holes are formed and is partially filled with a dielectric. [14] An antenna device comprising the converter according to any one of claims 1 to 13.

Images