JP2016184831A - Inductive iris coupled waveguide filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture at low cost an inductive iris coupled waveguide filter having high frequency characteristics.SOLUTION: The inductive iris coupled waveguide filter is so configured that a plurality of cavity resonators are coupled through a plurality of irises. N (N≥2) cavity resonators 111 to 113 are provided. A first irises (irises 121, 124), which are disposed on an input side and an output side of a waveguide and have an equal thickness of h1, and a second irises (irises 122, 123), which are disposed inside the first irises and have an equal thickness of h2, are at least provided. When a signal wavelength in the waveguide is denoted as λg, normalized susceptance is denoted as B/Y0, a predetermined function is denoted as f(), and H2=f(λg, B/Y0, h1) is defined, a thickness h2 of the second irises is set at a value greater than or equal to H2 obtained by the formula.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inductive iris coupled waveguide filter.

  In a device using a high-frequency signal, various filters are used in order to remove unnecessary frequency component signals. In particular, in the frequency band of millimeter waves or more, a waveguide filter is often used from the viewpoint of passage loss. One such waveguide filter is an inductive iris coupled waveguide filter.

  FIG. 16 is a diagram illustrating a configuration of an inductive iris coupling waveguide filter. As shown in FIG. 16, the inductive iris coupling waveguide filter 100 has three cavity resonators 111 to 113 arranged in this example inside a waveguide 101 having a rectangular cross section. The cavity resonators 111 to 113 are provided with irises 121 to 124 extending inward from the wall surface.

  FIG. 17 shows an equivalent circuit of the inductive iris coupling waveguide filter 100 shown in FIG. As shown in FIG. 17, the inductive iris coupling waveguide filter 100 shown in FIG. 16 includes inductive components L1 to L4 and capacitive components C1 to C3 connected in a ladder shape, and allows a predetermined frequency band to pass. Operates as a bandpass filter.

  FIG. 18 is a diagram showing the characteristics of the inductive iris coupling waveguide filter 100 shown in FIG. In this figure, the horizontal axis indicates the frequency [GHz], and the vertical axis indicates the reflection characteristic S11 and the transmission characteristic S21. As shown in FIG. 18, the inductive iris coupling waveguide filter 100 shown in FIG. 16 has a band-pass characteristic that passes through a predetermined frequency band and attenuates (or reflects) other than that.

  By the way, in the inductive iris coupling waveguide filter 100 shown in FIG. 16, the iris thickness h tends to decrease as the passing frequency increases.

  FIG. 19 shows the pass characteristic S21 when the iris thickness of the inductive iris coupling waveguide filter is set to 0.1 mm, 0.5 mm, and 1 mm, FIG. 20 shows the reflection characteristic S11, and FIG. A part of FIG. 19 is enlarged. As shown in these figures, the characteristics change greatly as the iris thickness changes. In general, inductive iris coupled waveguide filters are manufactured by cutting, and as the thickness of the iris decreases, it becomes difficult to ensure accuracy during manufacturing. It becomes difficult. In order to ensure the accuracy of cutting, the thickness is desirably 0.5 mm or more.

  Further, as shown in FIG. 22, the inductive iris coupling waveguide filter is formed as a portion divided by the E plane or the H plane, and the filter is completed by fitting these portions after the formation. When the iris is thin, it is necessary to accurately position the iris when fitting, but when the positioning is not successful and an offset occurs, the characteristics change. FIG. 23 is a diagram illustrating a change in characteristics due to an offset. In FIG. 23, the solid line indicates the transmission characteristic (S21) and the reflection characteristic (S11) when no offset occurs, and the broken line indicates the transmission characteristic (S21) and the reflection characteristic (S11) when the offset is 0.5 mm. ). From the comparison of these graphs, it can be seen that the characteristics greatly change due to the occurrence of the offset.

  Therefore, in order to solve such a problem, Patent Document 1 discloses a technique for manufacturing an inductive iris coupling waveguide filter by etching instead of cutting.

JP2013-141125A

  In the technique disclosed in Patent Document 1, an inductive iris coupled waveguide filter can be manufactured with high accuracy even when the iris is thin, but there is a problem that the manufacturing cost increases.

  The present invention has been made in view of the above points, and an object thereof is to make it possible to inexpensively manufacture an inductive iris coupling waveguide filter having high frequency characteristics.

In order to solve the above problems, the present invention provides N (N ≧ 2) cavity resonances in an inductive iris coupled waveguide filter configured by coupling a plurality of cavity resonators via a plurality of irises. A first iris having the same thickness h1 disposed on the input side and the output side of the waveguide, and a second iris having the same thickness h2 disposed on the inner side of the first iris. H2 = f (λg, B / Y0) where the wavelength of the signal in the waveguide of the waveguide is λg, the normalized susceptance is B / Y0, and the predetermined function is f () , H1), and the thickness h2 of the second iris is set to be equal to or larger than H2 obtained by the above formula.
According to such a configuration, an inductive iris coupling waveguide filter having high frequency characteristics can be manufactured at low cost.

Further, the present invention is characterized in that the predetermined function f () is represented by the following equation: H2 = λg / 4 + λg / 2π · tan ⁻¹ (2 / B / Y0) + h1.
According to such a configuration, the second iris can be formed while maintaining sufficient accuracy by cutting.

Further, the present invention is characterized in that the thickness h2 of the second iris is set so as to satisfy a relationship of 1.05 ≦ h2 / H2 ≦ 1.3.
According to such a configuration, an inductive iris coupling waveguide filter having desired characteristics can be configured.

In addition, the present invention includes N (N ≧ 4) cavity resonators, and third to i-th irises having thicknesses h2 to hi respectively disposed inside the second iris. The thicknesses h (i-1) and hi of the (i-1) th iris and the ith iris adjacent to each other are set so as to satisfy the following relationship: 1.1 ≦ h (i -1) /hi≦1.16.
According to such a structure, even if it has three or more types of irises, it can be formed while maintaining sufficient accuracy by cutting.

Further, the present invention is characterized in that the waveguide is constituted by a portion divided by an E plane or an H plane, and the waveguide is constituted by fitting these divided portions.
According to such a configuration, even if the inductive iris coupled waveguide filter is configured by fitting, it is possible to prevent the characteristic from being shifted due to the offset.

  According to the present invention, an inductive iris coupling waveguide filter having high frequency characteristics can be manufactured at low cost.

It is a perspective view which shows the structural example of the inductive iris coupling waveguide filter which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the structural example of the inductive iris coupling waveguide filter which concerns on 1st Embodiment of this invention. It is a figure which shows the range from which S11 becomes -15 dB or less. It is a figure which shows the range from which a pass bandwidth becomes 1 GHz. It is a figure which shows the simulation result of the passage characteristic S21. It is a figure which shows the simulation result of reflection characteristic S11. It is sectional drawing which shows the structural example of the inductive iris coupling waveguide filter which concerns on 2nd Embodiment of this invention. It is a figure which shows the result of having calculated | required the relationship between ratio of h3 / h2 and reflection characteristic S11 by simulation. It is a figure which shows the simulation result of 2nd Embodiment shown in FIG. It is a figure which expands and shows a part of passage characteristic S21 shown in FIG. It is sectional drawing which shows the structural example of the inductive iris coupling waveguide filter which concerns on 3rd Embodiment of this invention. It is a figure which shows the simulation result of 3rd Embodiment shown in FIG. It is a figure which expands and shows a part of passage characteristic S21 shown in FIG. It is a figure which shows the structural example in the case of having N iris. It is a figure which shows the characteristic which makes the range of 58.5-59.5 GHz pass band. It is a perspective view which shows the structural example of the conventional inductive iris coupling waveguide filter. It is a figure which shows the equivalent circuit of the inductive iris coupling waveguide filter shown in FIG. It is a figure which shows the characteristic of the inductive iris coupling waveguide filter shown in FIG. It is a figure which shows the change of the passage characteristic at the time of changing the thickness of an iris. It is a figure which shows the change of the reflective characteristic at the time of changing the thickness of an iris. It is a figure which expands and shows a part of FIG. It is a figure which shows the case where the embodiment shown in FIG. 16 is divided into two. It is a figure which shows the change of the characteristic by the offset at the time of the fitting of iris.

  Next, an embodiment of the present invention will be described.

(A) Description of First Embodiment of the Present Invention FIG. 1 is a perspective view of an external appearance of an example of the internal structure of an inductive iris coupling waveguide filter 100 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the inductive iris coupling waveguide filter 100 shown in FIG. As shown in FIGS. 1 and 2, the inductive iris coupling waveguide filter 100 of the first embodiment has one opening of a waveguide 101 having a rectangular cross section as an input port 102. The other is the output port 103. In addition, three cavity resonators 111 to 113 are provided inside the waveguide 101, and irises 121 to 124 are provided in these three cavity resonators 111 to 113. As shown in FIG. 2, the width of the input port 102 and the output port 103 in the X direction is a, the width of the cavity resonators 111 to 113 in the Y direction is S, and the iris 121 to 124 in the Y direction. The widths are h1, h2, h2, and h1, respectively, and the distance between the facing irises is W. The target characteristics of the inductive iris coupling waveguide filter 100 shown in FIGS. 1 and 2 are a center frequency of 41.5 GHz and a pass characteristic (S21) at 41 to 42 GHz of −0.7 dB or more. The return loss (S11) is assumed to be −15 dB or less.

  In the first embodiment, the relationship between the thickness h1 of the irises 121 and 124 and the thickness h2 of the irises 122 and 123 is as follows. First, H2 is obtained using the following equation (1), and the obtained H2 is represented by the following equation ( Substituting into 2), the thickness h2 of the irises 122 and 123 is determined so as to satisfy the expression (2). Here, λg is the wavelength of the signal in the waveguide, B / Y0 is the normalized susceptance, and h1 is the thickness of the iris 121,124. Note that the thickness h1 of the irises 121 and 124 is desirably 0.5 mm or more in consideration of the accuracy of the cutting process. With respect to h2, since h2> h1 is satisfied according to the equation (1), the thickness of only h1 may be considered.

・・・（１）

... (1)

1.05 ≦ h2 / H2 ≦ 1.3 (2)

  In addition, with respect to Expression (2), the pass bandwidth (in the range of S21> −0.7 dB) in the inductive iris coupling waveguide filter using three cavity resonators is 1 GHz or more, and the reflection S11 is −15 dB It is obtained by specifying parameters that fall within the following ranges. More specifically, 1.05 ≦ h2 / H2 ≦ 1.3 is specified as a range in which S11 is −15 dB or less as shown in FIG. 3, and the passband width is 1 GHz as shown in FIG. Since h2 / H2 ≦ 1.4 is specified as the range, 1.05 ≦ h2 / H2 ≦ 1.3 shown in Formula (2) is specified as a range satisfying both.

  By the above method, for example, the dimensions of each part of the inductive iris coupling waveguide filter 100 shown in FIG. 1 are h1 = 1.00 mm, W = 2.98 mm, S = 3.725 mm, and h2 = 3. 04mm is obtained. 5 and 6 are diagrams showing simulation results using such parameters. More specifically, FIG. 5 shows the transmission characteristic S21, and FIG. 6 shows the reflection characteristic S11. As shown in FIG. 5, the range of S21> −0.7 dB is in the range of 41 to 42 GHz, and the reflection is −15 dB or less in the range of 41 to 42 GHz as shown in FIG. It can be seen that the design goal has been achieved.

  As described above, in the first embodiment of the present invention, the irises 121 and 124 existing on the input / output side of the inductive iris coupled waveguide filter 100 having the three cavity resonators 111 to 113 are not shown. The thickness h1 is set to, for example, 1 mm or more in consideration of the accuracy of cutting, for example, and the thickness h2 of the irises 122 and 123 existing inside these is set to the formulas (1) and (2). I asked to see. In Expression (1), terms other than h1 take positive values, so that H2> h1. In addition, since h2> H2 in equation (2), the value of h2 obtained from equations (1) and (2) is h2> h1, so that h2 can be 1 mm or more in thickness. Thereby, the thickness of all the irises can be 1 mm or more in consideration of the accuracy of the cutting process. Further, even when the configuration is divided as shown in FIG. 22, it is possible to prevent the deviation of the characteristics due to the offset of the iris.

(B) Description of Configuration of Second Embodiment of the Present Invention Next, a second embodiment of the present invention will be described. In the second embodiment, as shown in a sectional view in FIG. 7, the inductive iris coupling waveguide filter 200 includes a waveguide 201 having a rectangular cross section. The inductive iris coupling waveguide filter 200 has an input port 202 and an output port 203. The waveguide 201 includes four cavity resonators 211 to 214 each having a width in the Y direction of S, and five irises 221 to 225 are provided in the four cavity resonators 211 to 214. . The width of the input port 202 and the output port 203 in the X direction is a, and the distance between the facing irises is W. Further, the width of the irises 221 and 225 is h1, the width of the irises 222 and 224 is h2, and the width of the iris 223 is h3.

  In the second embodiment, the width h1 of the irises 221 and 225 is set to 1 mm, for example, in consideration of cutting accuracy. Further, the widths h2 of the irises 222 and 224 are determined based on the above-described expressions (1) and (2). Further, the width h3 of the iris 223 is determined based on the following equation (3).

1.1 ≦ h3 / h2 ≦ 1.16 (3)

  Here, Equation (3) can be obtained as follows. FIG. 8 is a diagram showing a result of obtaining a relationship between the ratio h3 / h2 and the reflection characteristic S11 by simulation. In FIG. 8, the reflection characteristic S11 <−15 dB, which is the design target value, is in the range of 1.1 ≦ h3 / h2 ≦ 1.16. Therefore, this range is used as an equation for obtaining the range of h3 as shown in Equation (3).

  FIG. 9 is a diagram showing the reflection characteristic S11 and the transmission characteristic S21 of the second embodiment shown in FIG. 7, and FIG. 10 is an enlarged view showing a part of the transmission characteristic S21 shown in FIG. Note that the setting values of each parameter when obtaining FIG. 9 and FIG. 10 are a = 4.775 mm, λg = 11.044 mm, W = 2.98 mm, S = 3.73 mm, h1 = 1.00 mm, h2 = 3.10 mm and h3 = 3.50 mm. As shown in FIG. 9 and FIG. 10, in the range of 41 to 42 GHz, the transmission characteristic S21> −0.6 dB, and the reflection characteristic S11 <−15 dB, so that the design target value is achieved.

  As described above, in the second embodiment of the present invention, in the inductive iris coupled waveguide filter 200 having the four cavity resonators 211 to 214, the irises 221 and 225 arranged on the input side and the output side are used. In consideration of the accuracy of cutting, the thickness h1 is set to about 1 mm, and the thickness h2 of the irises 222 and 224 disposed inside the irises 221 and 225 is expressed by the formula (1). Since the thickness h2 is determined based on the equation (2), the thickness h2 can be set to h2> h1 for the same reason as described above. Further, since the thickness h3 of the iris 223 is determined based on the expression (3), it is possible to satisfy h3> h2> h1. For this reason, by setting h1 ≧ 1 mm, h2 and h3 can also be set to h2, h3 ≧ 1 mm, so that high-precision characteristics can be realized by cutting. Further, as shown in FIG. 22, even when the inductive iris coupling waveguide filter 200 is divided and configured, it is possible to prevent the characteristic from being shifted due to the offset.

(C) Description of Configuration of Third Embodiment of the Present Invention Next, a third embodiment of the present invention will be described. In the third embodiment, as shown in the sectional view of FIG. 11, the inductive iris coupling waveguide filter 300 includes a waveguide 301 having a rectangular cross section. The inductive iris coupling waveguide filter 300 has an input port 302 and an output port 303. The waveguide 301 has five cavity resonators 311 to 315 each having a width in the Y direction of S, and six irises 321 to 326 are provided in these five cavity resonators 311 to 315. ing. The width in the X direction of the input port 302 and the output port 303 is a, and the distance between the facing irises is W. Further, the width of the irises 321 and 326 is h1, the width of the irises 322 and 325 is h2, and the width of the irises 323 and 324 is h3.

  In the third embodiment, the width h1 of the irises 321 and 326 is set to 1 mm, for example, in consideration of cutting accuracy. Further, the width h2 of the irises 322 and 325 is determined based on the above-described equations (1) and (2). Further, the width h3 of the irises 323 and 324 is determined based on the above-described equation (3).

  12 is a diagram showing the reflection characteristic S11 and the transmission characteristic S21 of the third embodiment shown in FIG. 11, and FIG. 13 is an enlarged view of a part of the transmission characteristic S21 shown in FIG. In addition, as setting values of each parameter when obtaining FIG. 12 and FIG. 13, a = 4.775 mm, λg = 11.044 mm, W = 2.98 mm, S = 3.745 mm, h1 = 1.00 mm, h2 = 3.10 mm and h3 = 3.55 mm. As shown in FIGS. 12 and 13, in the range of 41 to 42 GHz, the transmission characteristic S21> −0.7 dB is satisfied, and the reflection characteristic S11 <−15 dB, so that the design target value is achieved. .

  As described above, in the third embodiment of the present invention, in the inductive iris coupled waveguide filter 300 having the five cavity resonators 311 to 315, the irises 321 and 326 arranged on the input side and the output side are provided. In consideration of the accuracy of the cutting process, the thickness h1 is set to about 1 mm, and the thickness h2 of the irises 322 and 325 arranged inside the irises 321 and 326 is expressed by Equation (1). Since the thickness h2 is determined based on the equation (2), the thickness h2 can be set to h2> h1 for the same reason as described above. Furthermore, since the thickness h3 of the irises 323 and 324 is determined based on the equation (3), it is possible to satisfy h3> h2> h1. For this reason, by setting h1 ≧ 1 mm, h2 and h3 can also be set to h2, h3 ≧ 1 mm, so that high-precision characteristics can be realized by cutting. Further, as shown in FIG. 22, even when the inductive iris coupling waveguide filter 300 is divided and configured, it is possible to prevent the characteristic from being shifted due to the offset.

(D) Description of Modified Embodiment The above embodiment is an example, and it is needless to say that the present invention is not limited to the case described above. For example, in the above embodiments, the width h1 of the iris provided on the input port and output port sides is set to 1 mm, but may be set to other values. For example, you may set to about 0.5 mm which is a value close | similar to the minimum which can maintain an precision in cutting.

  Further, the above-described formulas (1) to (3) are examples, and other formulas may be used.

  In each of the above embodiments, an embodiment (third embodiment) having a maximum of five cavity resonators has been described. However, six or more cavity resonators may be included. For example, as shown in FIG. 14, there are N (N ≧ 4) irises of h1 to hN, h1 = hN, h2 = h (N−1), h3 = h (N−2),. When the iris has a symmetric structure, the relationship between h1 and h2 is obtained by the above-mentioned formulas (1) and (2), and h2 and h3 are given by the above-described formula (3). The relationship between h (i−1) and hi (i ≧ 4) can be obtained by the following equation (4) similar to equation (3).

  1.1 ≦ h (i−1) /hi≦1.16 (4)

  Even with such a configuration, it is possible to obtain the performance to achieve the design purpose, and it is possible to make all the irises thick enough to maintain the cutting accuracy.

  In the first embodiment, the three cavity resonators 111 to 113 are provided. However, two cavity resonators may be provided. In that case, the two cavity resonators are coupled to each other via three irises, the thickness of the iris on the input / output side is h1, and the thickness of the inner iris is h2, so The thickness can be obtained by the above-described equations (1) and (2).

  Moreover, in each above embodiment, although the pass band was set to 41-42 GHz, you may set to a frequency other than this. For example, when the frequency is set lower than this, since the iris becomes thicker than when the frequency is set to 41 to 42 GHz, it can be manufactured without any problem. On the other hand, the same effect can be expected even when the frequency is set higher than 41 to 42 GHz. For example, in the inductive iris coupling waveguide filter 100 having the three cavity resonators 111 to 113 shown in FIG. 1, W = 2.2 mm, S = 2.0 mm, h1 = 1.00 mm, h2 = 3.29 mm. FIG. 15 shows the characteristics when set to. In FIG. 15, relatively good bandpass characteristics are obtained in the range of 59 to 60 GHz. From the above, even in a frequency band close to 60 GHz, the same effect as in the case described above can be expected.

  In the first embodiment shown in FIGS. 1 and 2, the four corners of the cavity resonator are perpendicular, but for example, rounding may be applied to the four corners as shown in FIGS. Good. For the iris, for example, the cross section may have a trapezoidal shape as shown in FIG. That is, the structure of the cavity resonator and the structure of the iris are not limited to those illustrated.

100, 200, 300 Inductive Iris Coupled Waveguide Filter 101, 201, 301 Waveguide 102, 202, 302 Input Port 103, 203, 303 Output Port 111-113, 211-214, 311-315 Cavity Resonator 121 -124, 221-125, 321-326 Iris

Claims (5)

In an inductive iris coupling waveguide filter configured by coupling a plurality of cavity resonators via a plurality of irises,
N (N ≧ 2) cavity resonators are disposed on the input side and the output side of the waveguide, the first iris having the same thickness h1 and the inner side of the first iris, respectively. And at least a second iris having a thickness equal to h2.
When the wavelength of the signal in the waveguide of the waveguide is λg, the normalized susceptance is B / Y0, and the predetermined function is f (),
H2 = f (λg, B / Y0, h1)
A thickness h2 of the second iris is set to be equal to or larger than H2 obtained by the above equation. The predetermined function f () is expressed by the following equation: H2 = λg / 4 + λg / 2π · tan ⁻¹ (2 / B / Y0) + h1
The inductive iris coupling waveguide filter according to claim 1.   3. The inductive iris coupling waveguide according to claim 1, wherein a thickness h <b> 2 of the second iris is set so as to satisfy a relationship of 1.05 ≦ h2 / H2 ≦ 1.3. filter. N (N ≧ 4) cavity resonators, and third to i-th irises having a thickness of h2 to hi, which are arranged inside the second iris, respectively, are adjacent to each other. The thicknesses h (i-1) and hi of the (i-1) th iris and the i-th iris are set so as to satisfy the following relationship,
1.1 ≦ h (i−1) /hi≦1.16
The inductive iris coupling waveguide filter according to any one of claims 1 to 3.   The said waveguide is comprised from the part divided | segmented by E surface or H surface, The said waveguide is comprised by fitting these divided | segmented parts. An inductive iris coupled waveguide filter as described.

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