JP4753981B2 - Waveguide / stripline converter - Google Patents

Description

  The present invention relates to a waveguide / strip line converter, and more particularly to a waveguide for transmitting microwaves and millimeter waves and a waveguide / strip line converter for performing power conversion between the strip lines. .

  When connecting a waveguide and a strip line, a waveguide / strip line converter capable of mutually converting the transmission power of the waveguide and the strip line is used (for example, Patent Document 1). In a general waveguide / stripline converter, a short-circuited waveguide block is required to make the distance from the stripline to the short-circuit plane ¼ of the guide wavelength λ. For this reason, it is difficult to reduce the size of the waveguide / strip line converter for microwaves and millimeter waves, and it is necessary to position the short-circuit surface with high accuracy during manufacturing. An improved waveguide / stripline converter is known in order to solve such problems (for example, Patent Document 2).

  8 and 9 are diagrams showing a configuration of a conventional waveguide / stripline converter described in Patent Document 2. FIG. 8 is a perspective view, and FIG. 9 is a plan view of the dielectric substrate 1 of FIG. 8. In FIG. 8, (a) shows the upper surface of the dielectric substrate 1, and (b) shows the lower surface of the dielectric substrate 1. ing. In this waveguide / stripline converter 109, the opening of the waveguide 2 is closely fixed to the lower surface of the dielectric substrate 1, and the short-circuit plate 3 is formed on the upper surface of the dielectric substrate 1, A strip line 5 is formed in the cut 11. On the other hand, a rectangular matching element 7 is formed on the lower surface of the dielectric substrate 1. The strip line 5 and the matching element 7 are electromagnetically coupled to each other by being disposed close to each other with the dielectric substrate 1 interposed therebetween, and power conversion is performed by this electromagnetic coupling. Therefore, a waveguide / stripline converter that does not require a short-circuited waveguide block can be realized. In addition, since the high-frequency circuit can be formed on the dielectric substrate 1, the entire apparatus can be further reduced in size.

FIG. 10 is a diagram showing an example of the frequency characteristics of the waveguide / stripline converter 109. In the figure, the transmission amount is maximum and the reflection amount is minimum at the frequency fa, and the frequency width at which the reflection amount is -20 dB or less is W2, that is, the waveguide / strip line conversion. As for the frequency characteristics of the device 109, the center frequency is fa and the bandwidth is W2. Since this frequency characteristic is determined by the shape of the matching element 7, the matching frequency is set so that the resonance frequency fa can match the in-tube wavelength of the waveguide 2 and the strip line 5 and the propagation wavelength in the dielectric substrate 1. The shape of 7 is determined.
JP-A-10-126114 JP 2002-359508 A

  However, the waveguide / stripline converter 109 described in Patent Document 2 has a narrow bandwidth W2, and thus a slight error occurs in the shape of the matching element 7 and the resonance frequency is slightly shifted. However, the conversion efficiency of the waveguide / stripline converter 109 is significantly reduced. As a result, there is a problem that the characteristics are likely to vary and the manufacturing yield is lowered. Further, if the processing accuracy of the matching element 7 is further improved, there arises a problem that the manufacturing cost increases.

  As described above, the frequency characteristic of the waveguide / strip line converter 109 can be adjusted by the size of the matching element 109. Specifically, the center frequency fa is adjusted by the length of the side (matching element length) parallel to the short side of the opening. The bandwidth W2 is adjusted by the length of the side parallel to the long side of the opening 21 (the width of the matching element). However, even if the width of the matching element 7 is adjusted, the bandwidth W2 cannot be sufficiently widened, and there is a limit to widening the bandwidth W2 by such a method.

  The present invention has been made in view of the above circumstances, and an object thereof is to realize a wide band of a waveguide / strip line converter in which a matching element and a strip line are electromagnetically coupled. Another object of the present invention is to facilitate the design of a waveguide / stripline converter having a desired frequency characteristic.

A waveguide / stripline converter according to a first aspect of the present invention is formed on a dielectric substrate having a first surface that closes a rectangular opening of the waveguide, and a second surface of the dielectric substrate, A short-circuit plate for short-circuiting the waveguide, a matching element formed on the first surface of the dielectric substrate, and a strip line formed in a cut in the short-circuit plate and electromagnetically coupled to the matching element. And the matching element is formed by deforming a part of the outer edge or the inner edge of the side parallel to the short side of the opening among the four sides of the rectangular frame composed of four sides parallel to the sides of the opening. And it has an asymmetrical shape in the direction parallel to the long side of the opening.

By making the matching element a shape surrounding the non-formation region, two or more resonance paths can be formed in one matching element. By making this matching element asymmetrical in the direction parallel to the long side of the opening, the resonance length of the resonance path can be made different. That is, a matching element having two or more different resonance lengths can be realized. By using such a matching element as a matching element that electromagnetically couples to the strip line, a small-sized waveguide / strip line converter can be widened. In addition, while determining the center frequency according to the size of the rectangular frame, the bandwidth can be widened by deforming a part thereof into an asymmetric shape. This makes it possible to easily design a waveguide / strip line converter having a desired center frequency and bandwidth.

In the waveguide / stripline converter according to the second aspect of the invention, in addition to the above configuration, the rectangular frame has an outer edge whose length substantially matches the waveguide wavelength of the waveguide . Of the four sides of the rectangular frame, a part of the outer edge of the side parallel to the short side of the opening is deformed.

  In the waveguide / stripline converter according to the present invention, the matching element that is electromagnetically coupled to the stripline has a shape that surrounds the non-formation region, and has an asymmetric shape in a direction parallel to the long side of the opening. Have. With such a configuration, since one matching element can resonate at two or more different frequencies, the width of the frequency band in which power can be converted by the waveguide / strip line converter can be expanded.

  Therefore, the bandwidth can be expanded compared to conventional broadband waveguide / stripline converters, so that even if errors occur in the shape of the matching elements, etc., the desired conversion frequency can be covered. Can do. Therefore, it is possible to suppress a decrease in manufacturing yield and reduce manufacturing costs without using a high-precision processing technique.

  In particular, a desired center frequency and bandwidth can be obtained by forming the matching element by deforming the outer edge or part of the inner edge of the rectangular frame whose sum of lengths of the four sides substantially matches the guide wavelength of the waveguide 2. Therefore, it is possible to easily design a matching element that provides the above.

  1 to 3 are diagrams showing a configuration example of a waveguide / stripline converter according to an embodiment of the present invention. FIG. 1 is a developed perspective view, FIG. 2 is a plan view, and FIG. 3 is a sectional view taken along the line AA in FIG.

  The waveguide / stripline converter 100 is constituted by a dielectric substrate 1 on which a stripline 5 is formed. The dielectric substrate 1 is disposed in the opening 21 of the waveguide 2 and can convert the transmission power of the waveguide 2 and the strip line 5 to each other.

  The waveguide 2 has a hollow portion 23 surrounded by a tube wall 22 made of a conductive material, and radio waves propagate through the hollow portion 23. This waveguide 2 is a rectangular waveguide in which the tube wall 22 is composed of two narrow walls and two wide walls, and the cross section of the hollow portion 23 orthogonal to the propagation direction is a long side 2L corresponding to the wide wall. It is a rectangle composed of a short side 2S corresponding to a narrow wall. Further, an opening 21 is formed at one end of the waveguide 2. The opening 21 is formed by cutting the waveguide 2 with a cut surface orthogonal to the propagation direction, and has the same shape as the hollow portion 23.

  The dielectric substrate 1 is disposed such that the lower surface thereof closes the opening 21 of the waveguide 2. The dielectric substrate 1 is wider than the opening 21, the opening 21 is closed by the closed region 12 on the dielectric substrate 1, and the end surface of the tube wall 22 is tightly fixed on the dielectric substrate 1 around the closed region 12. ing. Further, a conductive metal thin film is formed on both surfaces of the dielectric substrate 1. A short-circuit plate 3 and a strip line 5 are provided on the upper surface of the dielectric substrate 1, and a ground plate 6 and a matching element 7 are provided on the lower surface. These thin films are formed on the dielectric substrate 1 by a method such as vapor deposition or sputtering, and are patterned by a method such as photoetching as necessary.

  The short-circuit plate 3 is formed so as to cover most of the closed region 12 of the dielectric substrate 1 and constitutes a short-circuit surface of the waveguide 2. The short-circuit plate 3 is formed with a strip-shaped cut 11 reaching the closed region 12, and the strip line 5 is formed in the cut 11.

  The strip line 5 is disposed at a certain distance from the short-circuit plate 3 and forms a coplanar line together with the short-circuit plate 3. The notch 11 of the short-circuit plate 3 extends in parallel with the short side 2S of the opening 21 and intersects with one of the long sides 2L. The strip line 5 is formed on the dielectric substrate 1 in the closed region 12. It is drawn from the inside to the longitudinal side of the waveguide 2.

  The ground plate 6 is formed so as to surround the closed region 12, leaving the closed region 12. The ground plate 6 and the waveguide 2 are made conductive by bringing the end face of the waveguide 2 into close contact with the ground plate 6.

  The matching element 7 is formed in the closed region 12 so as not to conduct with the ground plate 6. The matching element 7 is disposed so that a part thereof overlaps the strip line 5 with the dielectric substrate 1 interposed therebetween, and is electromagnetically coupled to the strip line 5. That is, an electromagnetic wave can be propagated between the strip line 5 and the matching element 7 through the dielectric substrate 1, and the wavelength is determined by the dielectric constant and thickness of the dielectric substrate 1. For this reason, it is easier to process than a conventional structure using a short-circuited waveguide block, and is also suitable for miniaturization.

  The through hole 8 is formed by filling the through hole of the dielectric substrate 1 with a conductive material. Through this through hole 8, the short-circuit plate 3 and the ground plate 6 are conducted, and the short-circuit plate 3 is held at the same potential as the waveguide 2. Further, by disposing a plurality of through holes 8 around the closed region 12 and surrounding the closed region 12 with a conductive material, power loss in the dielectric substrate 1 is suppressed. At this time, the closed region 12 of the dielectric substrate 1 functions as a kind of waveguide in which a dielectric is filled.

  FIG. 4 is a diagram showing an example of the arrangement of the strip line 5, the matching element 7 and the opening 21 in FIG. In this drawing, the long side of the opening 21 is shown to extend in the left-right direction and the short side in the up-down direction. The matching element 7 has a left-right asymmetric shape obtained by deforming a part of a rectangular frame. The rectangular frame has four sides parallel to each side of the opening 21 and has a shape surrounding a rectangular non-formation region 7h where no conductive thin film is formed. The matching element 7 has a shape that is deformed asymmetrically by adding a convex part to a part of a symmetrical rectangular frame. The strip line 5 is disposed so as to overlap a part of the lower side or the upper side of the matching element 7.

  Theoretically, it is known that only an electric field parallel to the short side 2S exists in the waveguide 2. For this reason, there are two resonance paths P1 and P2 in the matching element 7 having a substantially rectangular frame shape. One resonance path P1 is a path passing through the right side of the non-formation area 7h, and the other resonance path P2 is a path passing through the left side of the non-formation area 7h. If the lengths of the two sides of the rectangular frame are L1 and L2, when the matching element 7 is a complete rectangular frame, the lengths of the resonance paths P1 and P2 are both (L1 + L2). However, the matching element 7 having two different resonance lengths can be formed by making the shape of the matching element 7 asymmetric and making the lengths of the two resonance paths P1 and P2 different.

  Since the electric field in the waveguide 2 is maximum at the longitudinal center, the matching element 7 is disposed so as to pass through the center line 2C that bisects the long side 2L of the waveguide 2 vertically. Is desirable. Impedance matching can be performed by adjusting the insertion length ρ of the strip line 5 into the matching element 7.

FIG. 5 is a diagram showing the frequency characteristics of the transmission amount and the reflection amount of the waveguide / stripline converter 100 of FIG. The transmission amount and the reflection amount are values obtained as the scattering parameters S ₂₁ and S ₁₁ , and are shown along with the characteristics of the conventional apparatus, with the frequency on the horizontal axis. Solid lines T1 and R1 in the figure are characteristic curves showing the amount of transmission and reflection of the waveguide / stripline converter 100 of FIG. On the other hand, broken lines T2 and R2 represent the transmission amount and reflection amount of the conventional waveguide / stripline converter 109 shown in FIG.

  Generally, the frequency characteristics of the waveguide / strip line converter are such that the transmission amount is maximum and the reflection amount is minimum at the resonance frequency of the matching element 7. Further, the width of the frequency at which the reflection amount is −20 dB or less is the bandwidth.

  Since the reflection amount R2 of the conventional waveguide / stripline converter 109 has one downward peak (valley) that sharply decreases in the vicinity of the resonance frequency fa, the bandwidth W2 is narrow. On the other hand, since the waveguide / stripline converter 100 according to the present embodiment has two different resonance frequencies fa and fb, the reflection amount R1 has two downward peaks. Since the downward peaks are connected without exceeding −20 dB, the bandwidth W1 is wider than the conventional bandwidth W2.

  As described above, since the matching element 7 has a substantially rectangular frame shape, the lengths of the two resonance paths P1 and P2 are both approximately (L1 + L2). Since the resonance frequency of the matching element 7 is a frequency whose resonance length corresponds to ½ wavelength, the center frequency of the waveguide / stripline converter 100 is a frequency corresponding to the wavelength (L1 + L2) × 2. . That is, when the matching element 7 has a substantially rectangular frame shape, the center frequency of the waveguide / strip line converter 100 can be controlled by the sum of the lengths of the four sides of the rectangular frame. In order to perform power conversion by the waveguide / stripline converter 100, the in-tube wavelengths of the waveguide 2 and the stripline 5, and the propagation wavelength in the dielectric substrate 1 between the stripline 5 and the matching element 7 are used. However, it is necessary to match this center frequency.

  On the other hand, the difference between the two resonance paths P1 and P2 corresponds to the frequency difference of the downward peak of the reflection amount. For this reason, by adding a convex part or a concave part to a part of the rectangular frame to form a left-right asymmetric shape, the bandwidth W1 can be widened by providing a slight difference between the two resonance paths P1 and P2. . Note that the difference between the discontinuous resonance frequencies fa and fb needs to be a value within a range in which the distance between the two corresponding downward peaks is connected without the reflection amount R1 exceeding −20 dB.

  Moreover, the conversion rate of two frequencies can be adjusted by moving the position which forms the stripline 5 in parallel with the long side of the opening part 21. FIG. That is, by providing the overlapping region of the strip line 5 and the matching element 7 on the resonance path P1 side, the frequency conversion rate corresponding to the resonance path P1 is increased, and the frequency conversion rate corresponding to the resonance path P2 is decreased. be able to. On the contrary, by providing more on the resonance path P2 side, the frequency conversion rate corresponding to the resonance path P2 can be increased, and the frequency conversion rate corresponding to the resonance path P1 can be decreased.

  FIG. 6 is a diagram showing an example of a matching element 7 that can be applied to the waveguide / stripline converter 100 of FIG. (A)-(c) in a figure is shown so that the long side of the opening part 21 may become a left-right direction and a short side may become an up-down direction similarly to the case of FIG. The matching element 7a of (a) is formed asymmetrically by projecting a part of the inner edge of the right side of the rectangular frame. This protrusion is for forming a shortened resonance path, and is preferably formed so as to include the apex angle of the inner edge. The matching element 7b of (b) is formed asymmetrically left and right by protruding a part of the outer edge of the right side of the rectangular frame. The projecting portion is for forming an extended resonance path, and is preferably formed so as to include the center of the side.

  In both (a) and (b), examples of the matching elements 7a and 7b in which only the right side of the rectangular frame is deformed are shown, but it is possible to obtain the same effect even if only the left side is deformed. Needless to say. Further, both the left side and the right side may be deformed. For example, the bandwidth can be effectively expanded by projecting the inner edge of one of the left and right sides and projecting the other outer edge. Moreover, in (a) and (b), the example which provides a convex part in a part of a rectangular frame and deform | transforms was shown, However, It can also be made to deform | transform asymmetrically by providing a recessed part.

  (C) shows an example of the matching element 7c that is deformed into an asymmetric shape by adding a shape corresponding to a diagonal line of the rectangular frame so as to divide the non-formed region 7h in the rectangular frame. Has been. It has been confirmed by experiments that the bandwidth is widened even when this matching element 7c is used. That is, the matching element 7 according to the present embodiment may have a shape surrounding two or more non-formed regions 7h as long as the shape is asymmetrical.

  FIG. 7 is a diagram showing an example of the shape of the conventional matching element 7 as a comparative example. (A)-(c) in a figure is shown so that the long side of the opening part 21 may become a left-right direction and a short side may become an up-down direction similarly to the case of FIG. The matching element 7d of (a) is formed as a rectangle that does not include a non-formation region. The matching element 7e of (b) is formed in a circular shape that does not include a non-formation region. The matching element 7f in (c) has a ring shape surrounding the circular nonlinear region 7h.

  In the case of the matching element 7d of (a), the resonance length is the length of the resonance path P1 indicated by the solid line, that is, the length of the matching element 7d parallel to the short side 2S of the opening 21. By expanding the width of the matching element 7d, the resonance path P2 indicated by the broken line contributes, and the bandwidth can be increased somewhat, but a sufficient effect cannot be obtained.

  Since the matching element 7e of (b) is circular, the lengths of the resonance paths P1 and P2 corresponding to the diameter are the same. For this reason, the downward peak of the reflection characteristic becomes steeper and the bandwidth becomes narrower than in the case of (a). In the case of the matching element 7f in (c), the matching element 7f is formed so as to surround the non-formation region 7h, but has a symmetrical shape. Its bandwidth is narrowing.

  In the waveguide / stripline converter 100 according to the present embodiment, the matching element 7 is formed on the first surface of the dielectric substrate 1 that closes the opening 21 of the waveguide 2, and is formed on the second surface. The strip line 5 is electromagnetically coupled. If such a matching element 7 has a shape that surrounds the non-formation region 7h and is asymmetric in the direction parallel to the long side 2S of the opening 21, the waveguide / stripline converter 100 is doubled. Broadband can be achieved by resonance. Therefore, it is possible to manufacture a small waveguide / stripline converter that performs power conversion at a desired frequency without using a high-precision processing technique.

  In particular, the shape of the matching element 7 is a rectangular frame composed of four sides parallel to each side of the opening 21, and the sum of the lengths of the four sides substantially matches the in-tube wavelength of the waveguide 2. By adopting a shape in which a part of the outer edge or inner edge of the frame is deformed, it is possible to easily design a waveguide / stripline converter that performs power conversion for a desired frequency.

  In the above embodiment, the case where the matching element 7 has a shape obtained by asymmetrically deforming a rectangular frame has been described. However, the present invention is not limited to such a case. For example, the ring shape may be modified so as to be asymmetric with respect to the direction parallel to the long side of the opening.

1 is a perspective view showing a waveguide / stripline converter 100 according to a first embodiment of the present invention. It is a top view of the dielectric substrate 1 of FIG. A sectional view taken along the line AA in FIG. 2 is shown. It is the figure which showed an example of arrangement | positioning of the stripline 5, the matching element 7, and the opening part 21 of FIG. It is the figure which showed the frequency characteristic of the transmission amount and reflection amount of the waveguide / stripline converter 100 of FIG. It is the figure which showed an example of the matching element 7 which can be applied to the waveguide and stripline converter 100 of FIG. It is the figure which showed an example of the shape of the conventional matching element 7 as a comparative example. It is the perspective view which showed the structure of the conventional waveguide / stripline converter 109. FIG. It is a top view of the dielectric substrate 1 of FIG. It is the figure which showed the frequency characteristic of the conventional waveguide / stripline converter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric board | substrate 2 Waveguide 2C Center line 2L Long side 2S Short side 3 Short circuit board 5 Strip line 6 Grounding board 7, 7a-7f Matching element 8 Through hole 12 Closed region 21 Opening part 22 Wall 23 Hollow part 100 Conduction Wave tube / strip line converter fa, fb Resonant frequency P1, P2 Resonant path R1, R2 Reflected amount T1, T2 Transmitted amount W1, W2 Bandwidth

Claims (2)

A dielectric substrate having a first surface that closes the rectangular opening of the waveguide;
A short-circuit plate formed on the second surface of the dielectric substrate and short-circuiting the waveguide;
A matching element formed on the first surface of the dielectric substrate;
A strip line formed in the notch of the short-circuit plate and electromagnetically coupled to the matching element;
The matching element has a shape obtained by deforming a part of the outer edge or the inner edge of a side parallel to the short side of the opening among the four sides of a rectangular frame having four sides parallel to the sides of the opening. Te, a waveguide-stripline transducer and having an asymmetrical shape about a direction parallel to the long sides of the opening. In the rectangular frame, the length of the outer edge thereof substantially matches the guide wavelength of the waveguide,
2. The waveguide according to claim 1, wherein the matching element has a shape obtained by deforming a part of an outer edge of a side parallel to the short side of the opening among the four sides of the rectangular frame. Stripline converter.

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