Variable Attenuator

Abstract

To provide a variable attenuator which is capable of easily performing the creation and dimensional management of a mechanism that movably holds a post, while reducing the leakage of electromagnetic waves in the mechanism, and which is also adaptable even to a higher frequency band.SOLUTION: A variable attenuator 1 includes: a waveguide block 2 in which a transmission groove 21 having an opening is formed; a laminated plate part 3 in which the opening is closed with a part of the opening unclosed, to form a waveguide 21a, and which covers the waveguide block 2 such that through holes 35, 36 of a plurality of sets of choke plates 31, 32 are stacked to form an insertion / extraction hole from the outside via the part of the opening with respect to the inside of the waveguide 21a; and a variable post 5 made of a conductor, the variable post being driven to be inserted into / extracted from the waveguide 21a through the insertion / extraction hole. In the laminated plate part 3, the insertion / extraction hole functions as a post movable holding part 8, and a colgate-like choke structure is formed where the through hole 35 with a predetermined hole diameter and the through hole 36 with a hole diameter larger than the predetermined hole diameter are alternately joined in the stacking direction such that the hole diameter changes step by step.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a variable attenuator having a variable post, and more particularly to a variable attenuator in which a mechanism for removably holding a variable post has a choke structure for reducing leakage of electromagnetic waves. [Background technology]

[0002] In recent years, for example, with the spread and progress of so-called 5G communication technology that communicates according to the 5G NR standard, expectations are also rising for the realization of communication terminals that handle signals in higher frequency bands, for example, the millimeter wave band (30 to 300 GHz) or higher bands, or signal analysis devices that perform signal analysis processing of the millimeter wave band or higher bands output by the communication terminals.

[0003] To avoid the adverse effects of excessive input, communication terminals and signal analysis devices (millimeter wave communication devices) that handle millimeter wave signals are now equipped with variable attenuators that variably set the amount of attenuation and attenuate the level of the input signal (modulated signal) to a set level.

[0004] In the microwave band (including millimeter wave band and lower frequency bands), when configuring an element with variable characteristics within a waveguide, there is a method of adjusting the distributed constant by changing the aperture shape. With this method, an aperture with a continuously variable constant can be provided and used as a variable attenuator. This change in aperture shape is often based on mechanical shape changes, and several methods are known. One example is a shape in which a member called a post is inserted into, for example, a rectangular cross-section waveguide (hereinafter referred to as a variable post).

[0005] A conventional variable attenuator using a rectangular cross-section waveguide is one in which an adjustment rod with a small outer diameter made of an electromagnetic wave resistor or electromagnetic wave absorber is inserted into a protective tube provided across the opposing inner walls of a rectangular cross-section waveguide (waveguide), and the electromagnetic power is changed depending on the insertion position of the adjustment rod (Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-140811 Summary of the Invention [Problem to be solved by the invention]

[0007] The waveguide-type variable attenuator described in Patent Document 1 has an adjustment rod inserted into a protective tube, but has a mechanism that allows the insertion position of the adjustment rod to be changed, and can be said to adopt a type of adjustment rod, i.e., a variable post, that is inserted into and removed from the waveguide.

[0008] In this type of variable attenuator, in order to hold the post so that it can be inserted and removed (moved), it is necessary to provide a small gap between the post and the holding hole that holds the post so that it can be moved. Unintentional leakage of electromagnetic waves from this gap causes crosstalk and isolation degradation due to the leakage signal's wraparound, or signal distortion due to the multiple reflection process. In order to improve such signal degradation or distortion, it is sufficient to make the gap of the holding hole very small, but in high frequency bands such as the millimeter wave band, this requires precision below the lower limit of the machining tolerance, which is not realistic. For example, in the millimeter wave band over 100 GHz, the wavelength is short at several millimeters (mm), so the gap in the moving part due to the manufacturing tolerance cannot be ignored. This leakage of electromagnetic waves hinders the application of existing attenuation aperture shapes developed in the microwave band.

[0009] In order to prevent electromagnetic waves from leaking from the mechanism that movably holds the post, such as the above-mentioned retaining hole, it is effective to provide an appropriate choke structure and provide a propagation blocking band through electromagnetic coupling. However, existing choke structures have not been satisfactory in terms of either structure (ease of creating the shape) or performance (function to prevent electromagnetic wave leakage) when providing the above-mentioned propagation blocking band. Furthermore, while there are expectations in recent years for compatibility with the millimeter wave band, it has become difficult to maintain the fine machining precision required to realize this, and dimensional control has also become difficult.

[0010] In the microwave band, especially the higher frequency millimeter wave band, for example the 300 GHz band, the operating wavelength is about 1 mm, and even if the gaps in the post holding parts and split surfaces are kept to 10 micrometers (um), the leakage of electromagnetic waves cannot be ignored. From this perspective, there is a demand for a choke structure that is easy to fabricate and easy to manage dimensions and is suitable for the millimeter wave band.

[0011] The present invention has been made to solve such conventional problems, and has as its object to provide a variable attenuator that reduces electromagnetic wave leakage from the mechanism that movably holds the post, while allowing for easy construction and dimensional control of the mechanism, and is also compatible with higher frequency bands. [Means for solving the problem]

[0012] In order to solve the above problems, a variable attenuator according to claim 1 of the present invention is configured by laminating a waveguide block (2) in which a transmission line groove (21) that opens toward the surface is formed, and a plurality of unit plates (31, 32) made of a conductor, the openings being closed except for a partial opening to form a waveguide (21a) by the transmission line groove, and a laminated plate portion (3) that covers the entire surface so as to form an insertion hole from the outside through the partial opening that penetrates the plurality of unit plates in the lamination direction, and a variable attenuator that protrudes into the waveguide through the insertion hole and protrudes into the waveguide so that the amount of protrusion changes continuously. singleand a variable post (5) made of a conductive material that is driven to reciprocate in the lamination direction of the position plate, and the variable attenuator (1) continuously variably attenuates a high-frequency signal transmitted through the waveguide by continuously changing the protrusion amount, and the lamination plate portion has a structure in which the insertion hole functions as a post movable holding portion (8) that holds the variable post in a movable state in which the variable post can be driven to reciprocate, and the cross-sectional shape of the insertion hole in the central axis direction changes stepwise in the lamination direction. The waveguide block is formed of a rectangular parallelepiped block body in which the transmission line groove having the opening is formed on one side surface (2c), and the stacking plate portion is provided with a through hole (35) of a predetermined hole diameter or a through hole (36) of a hole diameter larger than the predetermined hole diameter for each unit plate, and the through holes provided for each unit plate are stacked in a state in which all the unit plates are stacked to form the insertion hole, and the through holes of the predetermined hole diameter and the through holes of a hole diameter larger than the predetermined hole diameter are alternately arranged in the stacking direction to form a corrugated choke structure in which the hole diameter changes stepwise. The present invention is characterized by the above.

[0013] With this configuration, the variable attenuator according to claim 1 of the present invention has a structure in which the cross-sectional shape in the direction of the central axis of the insertion hole of the variable post from the outside into the waveguide changes stepwise in the stacking direction of the unit plates, and while improving the effect of preventing electromagnetic waves from leaking out from the gap between the post movable holding part and the variable post, it is possible to easily create the post movable holding part simply by stacking the unit plates. The ease of fabrication also makes it easy to manage dimensions, and it is possible to handle attenuation processing of signals in higher frequency bands, for example, millimeter wave bands, by increasing the precision of machining.

[0015] Also, Claims of the invention 1 In the variable attenuator of the present invention, the post movable holding part has a corrugated structure in which through holes of a predetermined hole diameter and through holes of a hole diameter larger than the predetermined hole diameter are arranged alternately in the stacking direction, so that the variable attenuator can enhance the function of preventing electromagnetic wave leakage while having a simple structure in which unit plates having through holes of different hole diameters are stacked and a corrugated choke structure is formed by stacking the through holes formed in each unit plate.

[0016] The plate can be easily manufactured by forming through holes of a predetermined diameter or larger in each unit plate and stacking them. The machining precision of the through holes can be easily maintained even when machining with fine dimensions, and the dimensions can be easily controlled. The easy dimension control makes it possible to handle attenuation processing of higher frequency bands, such as millimeter wave band signals, due to high-definition machining without reducing accuracy. With this configuration, the mechanism for movably holding the post (post movable holding part) can be easily manufactured and dimensionally controlled while reducing electromagnetic wave leakage from the mechanism, and higher frequency bands can be handled.

[0017] In addition, the claims of the present invention 2 In the variable attenuator according to the above aspect, the variable post may be formed of a cylindrical member, and the through hole may have a circular shape.

[0018] With this configuration, the present invention 2 The variable attenuator according to the present invention is easy to process with high precision because the main process for forming the through holes in each unit plate is to drill a circular hole. This makes it possible to maintain machining precision and, for example, makes it easier to handle attenuation processing of millimeter wave band signals.

[0019] In addition, the claims of the present invention 3 In the variable attenuator according to the above, the stacked plate portion may be configured by stacking a unit plate A (31) having a through hole with a diameter capable of holding the variable post in the movable state and a unit plate B (32) having a through hole with a diameter larger than the diameter of the through hole of the unit plate A in multiple stages.

[0020] With this configuration, the present invention 3In the variable attenuator according to the present invention, when making the laminated plate portion, it is sufficient to prepare the required number of unit plates A and B, each having a through hole of a different diameter, and stack the unit plates A and B so that an insertion hole is formed, and arrange them so that the position of the variable post corresponds to the position of the insertion hole. This makes it possible to realize a highly precise post movable holding portion that has a simple structure and is easy to make, yet has excellent ability to prevent electromagnetic wave leakage, and can also be used for attenuation processing of millimeter wave band signals.

[0021] In addition, the claims of the present invention 4 In the variable attenuator according to the above, the stacked plate portion may have a configuration in which a unit plate A1 (31A) having a through hole formed therein with a diameter capable of holding the variable post in the movable state, and a unit plate B1 (32A) having a two-stage through hole (36A) formed therein in which a lower through hole portion (36Ab) having a diameter equal to the diameter of the through hole of the unit plate A1 and an upper through hole portion (36Aa) having a diameter larger than the diameter of the through hole of the unit plate A1 are connected in the stacking direction, the unit plate B1 (32A) being stacked in multiple stages.

[0022] With this configuration, the present invention 4 In the variable attenuator according to the present invention, the laminated plate portion has a structure in which a unit plate A1 and a unit plate B1 in which a two-stage through hole consisting of a lower through hole portion and an upper through hole portion having different diameters are formed are laminated, and therefore the thickness of the unit plate B1 is increased, and the strength of the laminated plate portion can be increased.

[0023] In addition, the claims of the present invention 5 In the variable attenuator according to the above, the stacked plate portion may have a plurality of sets of a plurality of types of unit plates A2, B2, C2, D2, E2, F2 (37A, 37B, 37C, 37D, 37E, 37F) in which the through holes (38A, 38B, 38C, 38D, 38E, 38F) having different diameters capable of holding the variable post in the movable state are formed, and the plurality of types of unit plates may be periodically stacked in the stacking direction in the same order for each set.

[0024] With this configuration, the present invention 5 In the variable attenuator according to the present invention, the stacked plate section has a structure in which a plurality of types of unit plates A2, B2, C2, D2, E2, F2, each of which has a through hole with a different diameter, are grouped together, and the plurality of sets of unit plates A2, B2, C2, D2, E2, F2 are periodically stacked in the same order for each set, so that the degree of freedom in design is improved and the leakage of electromagnetic waves from the gap with the variable post can be more reliably reduced. Even in this case, the manufacturing and assembly processes such as the processing of the through holes in the unit plates A2, B2, C2, D2, E2, F2 and the stacking of the unit plates A2, B2, C2, D2, E2, F2 are not significantly complicated, and the advantage of being easy to manufacture while maintaining the machining accuracy is not lost. Effect of the Invention

[0025] The present invention can provide a variable attenuator that can reduce leakage of electromagnetic waves from a mechanism for movably holding a post, while easily fabricating the mechanism and controlling its dimensions, and that can also accommodate higher frequency bands. [Brief description of the drawings]

[0026] [Figure 1] 1 is a conceptual diagram showing an overall configuration of a variable attenuator according to an embodiment of the present invention; [Diagram 2] 2A and 2B are cross-sectional views of a variable attenuator according to an embodiment of the present invention, where FIG. 2A shows a cross-sectional view taken along the AA plane in FIG. 1, and FIG. 2B shows a cross-sectional view taken along the BB plane in FIG. [Diagram 3] 2 is a perspective view showing a cross-sectional configuration of a variable attenuator according to an embodiment of the present invention taken along the AA plane of FIG. 1. [Figure 4] 1A and 1B are enlarged views showing the main configuration of the post movable holding part of a variable attenuator according to one embodiment of the present invention, in which (a) is a cross-section of the main configuration of the post movable holding part, (b) is a plan view of the through hole provided in unit plate A of the post movable holding part, and (c) is a plan view of the through hole provided in unit plate B of the same part. [Diagram 5]1A to 1C are schematic diagrams showing examples of the configuration of a model for verifying the effectiveness of the electromagnetic wave leakage prevention function, in which (a) shows a comparison model 1, (b) shows a comparison model 2, and (c) shows the configuration of the model of the present invention corresponding to the post movable holding part in this embodiment. [Figure 6] 5(a) is a graph showing the electromagnetic wave characteristics of the comparison model 1, where (a) shows the reflection characteristics, (b) shows the transmission characteristics, and (c) shows the characteristics when the transmission attenuation is continuously adjusted by changing the post height. [Figure 7] 5(b) is a graph showing the electromagnetic wave characteristics of the comparison model 2 shown in FIG. 5(b), where (a) shows the reflection characteristics, (b) shows the transmission characteristics, and (c) shows the characteristics when the transmission attenuation is continuously adjusted by changing the post height. [Figure 8] 5(c) is a graph showing the electromagnetic wave characteristics of the model of the present invention shown in FIG. 5(c), where (a) shows the reflection characteristics, (b) shows the transmission characteristics, and (c) shows the characteristics when the transmission attenuation is continuously adjusted by changing the post height. [Figure 9] 10A to 10C are diagrams comparing the electric field strength distribution of the post support portion for each model, where (a) shows the electric field strength distribution of comparative model 1, (b) shows the electric field strength distribution of comparative model 2, and (c) shows the electric field strength distribution of the model of the present invention. [Figure 10] 1A and 1B are enlarged views showing the main configuration of the post movable holding part relating to variant example 1 of the present invention, in which (a) is a cross-section of the main configuration of the post movable holding part, (b) is a plan view of the through hole provided in unit plate A1 of the post movable holding part, and (c) is a plan view of the two-stage through hole having different hole diameters provided in unit plate B1 of the post movable holding part. [Figure 11] FIG. 11 is an enlarged view showing the main configuration of the post movable holding part relating to variant example 2 of the present invention, where (a) shows a cross-section of the main configuration of the post movable holding part, and (b), (c), (d), (e), (f), and (g) show the planar configurations of the through holes provided in unit plates A2, B2, C2, D2, E2, and F2 of the post movable holding part, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, a variable attenuator according to the present invention will be described with reference to the drawings.

[0028] In the present invention, among the waveguide-type variable attenuators that change the electromagnetic wave transmission characteristics or reflection characteristics by changing the aperture shape, those that have a movable post that can be inserted from the outside of the waveguide and protrude into the inside, and have the function of changing the aperture shape by changing the insertion amount of the post into the waveguide are assumed. Among them, in particular, a low leakage waveguide type variable attenuator is assumed in which a mechanism (see "post movable holding part 8" described later) that holds the variable post so that it can be inserted and removed from the outside to the inside of the waveguide has a choke structure to reduce leakage of electromagnetic waves from the gap with the variable post, and this choke structure suppresses leakage of electromagnetic waves while performing signal attenuation processing.

[0029] This low leaky waveguide type variable attenuator (hereinafter, variable attenuator) can be adopted, for example, in 5G terminals that communicate according to the 5G NR standard, signal analysis devices (signal analyzers and spectrum analyzers) that perform analysis processing of radio signals output by 5G terminals, and also in various millimeter wave band communication devices (millimeter wave band communication terminals, millimeter wave band signal analysis devices, etc.) that handle signals in a frequency band (millimeter wave band) higher than the 5G band (for example, 26.5 GHz). Hereinafter, one embodiment of the variable attenuator according to the present invention, which is assumed to be mounted on a millimeter wave band communication device, will be described.

[0030] First, the configuration of a variable attenuator 1 according to an embodiment of the present invention will be described with reference to FIGS. As shown in Fig. 1, a variable attenuator 1 according to an embodiment of the present invention is configured to include a waveguide block 2, a stacking plate section 3, a coupling block 4, a variable post 5, a post driving section 6, and a coupling support section 7. The waveguide block 2, the stacking plate section 3, and the coupling block 4 each have, for example, a rectangular parallelepiped shape, and are stacked vertically to form a block body having a rectangular parallelepiped shape as a whole. In Fig. 1 to Fig. 3, orthogonal three-dimensional coordinate indices are added, and the directions of three sides that meet at one corner of the block body are defined as the x (left-right) direction, the y (front-back) direction, and the z (up-down: vertical) direction, respectively.

[0031] The waveguide block 2 is composed of a conductive block body having a rectangular parallelepiped shape, and as shown in Figures 1 to 3, for example, in the center in the front-to-rear direction of the lower side surface 2c (hereinafter, bottom surface) out of the six side surfaces 2a, 2b, 2c, 2d, 2e, and 2f, a transmission line groove 21 with a rectangular cross section that opens downward is formed across the left and right side surfaces 2e and 2f.

[0032] The laminated plate section 3 has a rectangular plane of the same shape as the bottom surface of the waveguide block 2, and is configured as a block body of a rectangular parallelepiped shape by laminating a plurality of unit plates A (hereinafter referred to as choke plates 31) and unit plates B (hereinafter referred to as choke plates 32) made of a conductor having an appropriate thickness in the thickness direction. In this embodiment, for example, three choke plates 31 and two choke plates 32 are alternately laminated in the order of choke plates 31, 32, 31, 32, 31 from the top (see Figs. 2 and 3). Choke plates 31 and 32, which will be described later, together with choke plates 31A and 32A and choke plates 31B, 32B, 33B, and 34B, which will be described later, constitute the unit plates of the present invention.

[0033] The laminated plate portion 3 is attached as the above-mentioned block body in a stacked state on the bottom surface of the waveguide block 2 (see FIG. 1). In this stacked state, the topmost choke plate 31 covers the entire bottom surface of the waveguide block 2 so as to close all openings other than the remaining opening (partial opening) of the transmission line groove 21 formed on the bottom surface of the waveguide block 2 (see FIGS. 2 and 3).

[0034] More specifically, in the laminated plate section 3, the choke plates 31, 32, 31, 32, 31 have through holes 35, 36, 35, 36, 35, respectively, and the through holes 35, 36, 35, 36, 35 form a series (one) of through holes continuing in the lamination direction of the choke plates 31, 32, 31, 32, 31 (see Figs. 2 and 3). As described above, when the laminated plate section 3 is attached so as to cover the entire bottom surface of the waveguide block 2, in the unit plate A of the uppermost stage of the laminated plate section 3, as shown in Figs. 2 and 3, the portion other than the through hole 35 covers the opening of the transmission line groove 21, thereby forming a waveguide 21a whose longitudinal direction is the direction between the side surfaces 2e-2f of the transmission line groove 21, while the through hole 35 facing the opening of the transmission line groove 21 forms a partial opening of the transmission line groove 21. As a result, the series of through holes formed by laminating the above-mentioned through holes 35, 36, 35, 36, 35 in the laminated plate portion 3 functions as an insertion hole for inserting and removing the waveguide 21a from the outside via the partial opening.

[0035] As will be described in detail later, the object that is inserted into and removed from the waveguide 21a from the outside via the partial opening is the variable post 5. That is, in the laminated plate portion 3, a series of through holes formed by laminating the respective through holes 35, 36, 35, 36, 35 in the choke plates 31, 32, 31, 32, 31 specifically functions as an insertion / removal hole for the variable post 5 from the outside via a partial opening in the waveguide 21a.

[0036] In order to enable the insertion and removal of the variable post 5, the insertion and removal hole also has a function of movably holding the variable post 5 so that it can be driven (up and down movement) in the direction shown by the arrow C in Fig. 2 and Fig. 3. A single through hole (insertion and removal hole) formed by stacking two types of choke plates 31, 32 in the order of choke plates 31, 32, 31, 32, 31 and arranging the through holes 35, 36, 35, 36, 35 in the stacking direction (depth direction of the insertion and removal hole) is hereinafter referred to as the post movable holding part 8 (see Figs. 2 to 4). Also, among the through holes 35, 36 constituting the post movable holding part 8, the through hole 35 with the smaller hole diameter is sometimes referred to as the holding hole of the variable post 5, and the through hole 36A with the larger hole diameter is sometimes referred to as the choke hole.

[0037] The coupling block 4 is attached so as to abut against the lower surface of the choke plate 31 on the bottom surface of the laminated plate section 3, and stably holds the laminated plate section 3. The coupling block 4, like the laminated plate section 3, is made of a plate material having a rectangular plane of the same shape as the bottom surface of the waveguide block 2, and a through hole 41 having a diameter larger than the hole diameter formed by vertically arranging the through holes 35, 36, 35, 36, 35 of the post movable holding section 8 along the stacking direction is formed at a required position on the rectangular plane of the plate material. The coupling block 4 is stacked on the laminated plate section 3 so that the through hole 41 is arranged at a position that does not interfere with the advancement and retreat (linear drive) of the variable post 5 relative to the vertically arranged through holes 35, 36, 35, 36, 35 of the post movable holding section 8 described above.

[0038] The variable post 5 is a conductive member that is held so as to be able to reciprocate vertically by the through holes 35, 36, 35, 36, 35 that constitute the post movable holding part 8 formed in the laminated plate part 3, i.e., the insertion hole, and protrudes into the waveguide 21a formed by closing the waveguide block 2 except for a part of the opening as described above, and changes the opening shape according to the amount of protrusion. The variable post 5 is, for example, a rod-shaped body (cylindrical member) having a cylindrical shape, for example a cylindrical post, and has a circular cross-sectional shape in a direction perpendicular to the axial direction. The through holes 35, 36 also have a circular hole shape (cross-sectional shape in a direction perpendicular to the central axis of the hole) (see Figs. 4(b) and (c)).

[0039] The post driver 6 is a drive mechanism for linearly driving the variable post 5 in a direction (direction of arrow C) to advance or retreat the variable post 5 into the waveguide 21a via a partial opening (see Figs. 2 and 3). The post driver 6 may be, for example, an actuator such as an electric motor, an electromagnetic solenoid, or a hydraulic cylinder. The post driver 6 is not limited to automatically driving the variable post 5 to advance or retreat, and may be provided with a function for manual operation.

[0040] The connecting support portion 7 is a functional portion for connecting the connecting block 4 and the post driving portion 6 so that the variable post 5 is in a positional relationship that allows it to be linearly driven in the direction of arrow C as described above with respect to the through hole 41 provided in the connecting block 4 and each of the through holes 35, 36, 35, 36, 35 (insertion / removal holes) that constitute the post movable holding portion 8, and for maintaining that positional relationship.

[0041] Next, the configuration of the post movable holding portion 8 (see Figs. 2 and 3) in the laminated plate portion 3 will be described in more detail. Fig. 4 is an enlarged view showing the configuration of the main parts of the laminated plate portion 3 of the variable attenuator 1 according to this embodiment, and in particular Fig. 4(a) shows the cross-sectional configuration of the main parts of the post movable holding portion 8. As shown in Fig. 4(a), the laminated plate portion 3 of the variable attenuator 1 according to this embodiment has a laminated structure in which two types of unit plates, unit plate A (choke plate 31) and unit plate B (choke plate 33), are stacked in five stages.

[0042] In the post movable holding part 8 shown in Fig. 4(a), the first, third and fifth choke plates 31 and the second and fourth choke plates 32 have the same planar shape and plate thickness, but differ only in the diameter of the through holes. More specifically, the choke plate 31 has a through hole 35 with a predetermined hole diameter (diameter in this example) X1, as shown in Fig. 4(b), while the choke plate 32 has a through hole 36 with a hole diameter X2 (X2>X1), as shown in Fig. 4(c). The through holes 35 and 36 are arranged so as to be concentric circles with the same center on a plane (see Figs. 4(b) and (c)).

[0043] With this structure, in the stacked plate section 3 of the variable attenuator 1 according to this embodiment, when three choke plates 31 and two choke plates 32 are stacked in the order shown in Fig. 4(a), the hole diameter of the post movable holding section 8 as a whole changes stepwise in the choke plate stacking direction (depth direction of the insertion / removal holes) from a predetermined hole diameter X1 to a larger hole diameter X2, followed by hole diameter X1, hole diameter X2, and hole diameter X1. In this way, the post movable holding section 8 has a shape in which the hole diameter changes in a wavy, i.e. corrugated, shape in the choke plate stacking direction (depth direction).

[0044] In the movable post holder 8 having one through hole that changes in a corrugated shape in the depth direction, each of the through holes 35 located in the first, third and fifth stages has a hole diameter X1 slightly larger than the diameter of the variable post 5, and is capable of moving the variable post 5 up and down while holding it. In other words, each of the through holes 35 in the first, third and fifth stages functions as a holding hole that holds the variable post 5 so that it can move up and down. It cannot be said with certainty that each of the through holes 35 can completely block electromagnetic waves from leaking out from the gap between the variable post 5, which has a diameter slightly smaller than the hole diameter X1.

[0045] In this embodiment, as shown in Fig. 4(a), the second and fourth stages of the post movable holding portion 8 are further configured to have through holes 36 having a hole diameter X2 larger than the hole diameter X1. According to the corrugated through holes having through holes 36 having a hole diameter X2 larger than the through holes 35 having a small hole diameter X1 interposed between the through holes 35 having a small hole diameter X1 (in the stacking direction) as shown in Fig. 4(a), the through holes 35 having the hole diameter X1 function as holding holes that hold the variable post 5 so that it can be driven in the vertical direction (moved up and down), while the through holes 36 having the hole diameter X2 function as choke holes that block (clog) a small amount of electromagnetic waves leaking from the gap with the variable post 5 at the through hole 35 above it so as not to leak out to the outside (see Fig. 9(c)). In this way, the post movable holding portion 8 realizes a corrugated choke structure that prevents electromagnetic waves from leaking to the outside by stacking multiple choke plates 31 having through holes 35 with a hole diameter X1 and multiple choke plates 32 having through holes 36 with a hole diameter X2.

[0046] The operating principle of the corrugated choke structure for preventing electromagnetic wave leakage is that when variable posts 5 are inserted into a series of holes formed in the depth direction of a choke plate laminate (see laminated plate portion 3) having the choke structure, a corrugated coaxial line-like structure with a cross-sectional area that varies in a λ / 2 period is formed in the longitudinal direction along the variable posts 5. The characteristic impedance of this line shows a very low value centered on the wavelength λ. As a result, the choke portion (for example, in the laminated plate portion 3, the through hole 36 formed in the choke plate 32, i.e., the choke hole portion) viewed from the rectangular waveguide (transmission line groove 21) looks like a nearly conductive electric wall, making it possible to minimize the leakage of electromagnetic waves from the choke portion.

[0047] In the post movable holding section 8 of the laminated plate section 3 according to this embodiment, the choke plates 31, 32 are each composed of one or more laminated sheets, and the laminated surfaces are in contact (or are so close that they can be considered to be in electromagnetic contact) to form a corrugated laminated structure. This allows the individual choke plates 31, 32 to be manufactured simply by drilling through holes (35, 36), simplifying manufacturing and facilitating precision control.

[0048] The diameter of the through hole 36 formed in the choke plate 32 is determined by the λ / 4 phase matching condition. For example, when broadband operation is the objective, the hole should be made with a diameter λ / 2 larger than the hole diameter of the choke plate 31.

[0049] In this embodiment, it is assumed that the choke structure in the post movable holding portion 8 is realized by stacking multiple unit plates (choke plates), and several stacking methods are assumed in this case (see Figs. 4, 10, and 11). One example of a simple configuration is a method of stacking choke plates with through holes (see Fig. 4). A structure that functions as a choke can be constructed by simply setting the plate thickness to λ / 4 based on the λ / 4 phase matching condition, and stacking choke plates with different hole sizes alternately.

[0050] On the other hand, if it is desired to thicken the choke plate in consideration of strength, a structure in which two stages of through holes are opened in one choke plate and stacked (see FIG. 10) may be used. Also, a structure in which choke plates are stacked such that the change from a portion in which the hole diameter continuously increases to a portion in which the hole diameter continuously decreases is repeated multiple times (see FIG. 11). In this case, it is possible to more reliably reduce the leakage of electromagnetic waves. The structure in which a single plate is stacked with through holes having a two-stage structure of an upper and lower stage of through holes, and the structure in which plates in which the hole size continuously changes from large to small and small to large multiple times are stacked will be described in detail later as modified examples 1 and 2.

[0051] For the variable post 5, a cylindrical shape having a diameter slightly smaller than the diameter of the through hole (support hole) 35 having a smaller hole diameter is adopted among the through holes 35, 36 forming the choke structure in the post movable holding part 8. That is, the variable post 5 is supported (movably held) in a state in which it can slide relative to the support hole. As a result, in the choke structure of the post movable holding part 8 according to this embodiment, the holding hole and the variable post 5 may be partially in contact with each other or may not be in contact at all. Here, as long as the diameter of the support hole is appropriately controlled so that it is not too large compared to the diameter of the variable post 5, reflection suppression by phase matching can be achieved regardless of the presence or absence of contact. As described above, in this embodiment, the cross-sectional shape of the variable post 5 and the hole shapes of the holding hole (see the through hole 35) and the choke hole (see the through hole 36) that hold the variable post 5 are basically assumed to be circular.

[0052] The reason is that in the development stage of the variable attenuator 1 according to the present invention, there are severe limitations on the processing method for the hole shapes of the above-mentioned retaining hole (see through hole 35) and choke hole (see through hole 36). At present, good processing efficiency can be obtained by drilling a circular hole using a micro drill, and therefore the combination of a cylindrical post and a circular hole is the most promising, and for that reason a circular shape is exemplified.

[0053] However, in the present invention, the hole shapes of the adjustable post 5, the retaining hole (see through hole 35), and the choke hole are not necessarily limited to a circle. In other words, the cross-sectional shapes of the adjustable post 5, the retaining hole (see through hole 35), and the choke hole (see through hole 36) may be, for example, a square or star shape, as long as the hole shape can be processed, and the same effect can be expected in any case.

[0054] Furthermore, in the future, if hole shapes that can be machined more efficiently emerge with the advent of new machining methods such as laser machining, electric discharge machining, and ultrasonic machining, the present invention does not prevent their adoption.

[0055] In the variable attenuator 1 of this embodiment having the above-mentioned configuration, the variable post 5 protrudes into the waveguide 21a having a rectangular cross section, which is composed of the transmission line groove 21 provided on the underside of the waveguide block 2 and the choke plate 31 on the uppermost surface of the laminated plate portion 3 covering it, and by continuously changing the amount of protrusion, a continuously variable attenuation operation can be performed in which the reflectance and transmittance are continuously changed.

[0056] 3 discloses the configuration of the variable attenuator 1 as well as the configuration of a control system for the variable attenuator 1. The configuration of the control system disclosed here is an image of the continuous variable attenuation control operation of the variable attenuator 1 during communication by millimeter wave band signals in a millimeter wave communication device equipped with the variable attenuator 1. The millimeter wave communication device includes the variable attenuator 1 having the above-mentioned functional configuration, and is configured to include a setting unit 11 that sets the amount of attenuation, and an attenuation amount variable control unit 12 that performs continuous variable attenuation control of the amount of attenuation.

[0057] In this millimeter wave band communication device, the attenuation variable control unit 12 drives the variable post 5 back and forth (linearly) to continuously change the amount of protrusion of the variable post 5 into the waveguide 21 a while a millimeter wave band signal is being input to the waveguide 21 a of the variable attenuator 1, thereby controlling the signal output from the waveguide 21 a to have the attenuation amount set by the setting unit 11.

[0058] Here, the post movable holding part 8 (corresponding to the above-mentioned insertion hole) that holds the variable post 5 of the variable attenuator 1 so that it can be reciprocated has a corrugated choke structure formed by alternately stacking a plurality of choke plates 31, 32 having holding holes (through holes 35) and choke holes (through holes 36) with different hole diameters. The corrugated choke structure makes it possible to accurately and efficiently prevent leakage of electromagnetic waves from gaps between the holding holes (through holes 35) and choke holes (through holes 36) in the post movable holding part 8 and the variable post 5. The electromagnetic wave leakage reduction capability of the corrugated choke structure of the variable attenuator 1 is also reflected in the millimeter wave band communication device, making it possible to efficiently perform continuous variable attenuation operation of millimeter wave band signals.

[0059] The inventors of the present application have conducted a study on the effectiveness of the post movable holder 8 having the above-mentioned configuration as a function for preventing electromagnetic wave leakage from the post support portion. The implementation method and the results of the study will be described with reference to Figs. 5 to 9.

[0060] In examining the "effectiveness of the post support part as a function for preventing electromagnetic wave leakage," as verification models, for example, a model of the present invention having a structure equivalent to the post movable holding part 8 of this embodiment as shown in FIG. 5(c), a comparison model 1 having the structure shown in FIG. 5(a), and a comparison model 2 having the structure shown in FIG. 5(b) were prepared.

[0061] For all three models mentioned above, the structure was captured by dividing them into the parts shown on the left side of Figure 5(a), namely, the rectangular waveguide part P1, the post support part P2, and the open space part P3, and the structural characteristics of each part were defined as follows.

[0062] As for the uppermost rectangular waveguide section P1, a waveguide 21a was provided in a waveguide block 2, and each model had the same structure.

[0063] The post support parts P2 in the middle are each structured to have a retaining hole that penetrates the plate and movably holds the adjustable post 5. Here, the post support part P2 of the comparative model 1 (see FIG. 5(a)) is structured so that there is absolutely no gap between the retaining hole 310 penetrating the plate 300 and the adjustable post 5. The post support part P2 of the comparative model 2 (see FIG. 5(b)) is structured so that a certain gap is provided between the retaining hole 311 penetrating the plate 300 and the adjustable post 5, with no choke structure between them.

[0064] Moreover, the post support part P2 (see FIG. 5(c)) of the present invention model is structured so that there is a certain gap between the retaining hole (insertion / removal hole) provided in the laminated plate part 3 and the variable post 5, and there is a two-stage choke structure between the two. Specifically, the above-mentioned corrugated choke structure (see FIG. 4) is formed between the insertion / removal hole formed by the lamination of the through holes 35, 36, 35, 36, 35 of the choke plates 31, 32, 31, 32, 31 constituting the laminated plate part 3, and the variable post 5, and the insertion / removal hole functions as the post movable holding part 8 that movably holds the variable post 5.

[0065] An open space P3 was provided at the bottom, so that it was possible to check whether or not there was leakage of electromagnetic waves from the electric field intensity distribution in the open space P3.

[0066] In the above verification, the effectiveness of the present invention was examined by comparing three different structures, that is, a comparison model 1, a comparison model 2, and a model of the present invention, through numerical calculations. Specifically, for each structure of the comparison model 1, the comparison model 2, and the model of the present invention, numerical electromagnetic field analysis based on the finite element method was performed to calculate the reflection characteristics and transmission characteristics with respect to the change in height h of the variable post 5 in the waveguide 21a.

[0067] As a specific example of the conditions applied in the calculation, for example, the analysis frequency range was set to 150 to 400 GHz. The waveguide (rectangular waveguide) 21a had a width x height of 750 x 375 um. The diameter of the variable post 5 was set to 0.25 mm. The dimensions of the support hole were set to 0.25 mm, which is equal to the diameter of the variable post 5, for the support hole 310 of the comparative model 1 (see FIG. 5(a)), and 0.28 mm, which is larger than the diameter of the support hole 310 of the comparative model 2 (see FIG. 5(b)). In the present invention model, the hole diameter of the through hole 35 of the choke plate (unit plate A) 31 of the first, third, and fifth stages was set to 0.28 mm, and the hole diameter of the through hole 36 of the choke plate (unit plate B) 32 of the third and fourth stages was set to 0.9 mm. In addition, the plate thickness of both the choke plates 31 and 32 was set to 0.25 mm.

[0068] The calculation results of the reflection characteristics and transmission characteristics of each of the comparative model 1, the comparative model 2, and the model of the present invention will be described with reference to FIGS.

[0069] FIG. 6 is a graph showing the electromagnetic wave characteristics of the comparative model 1 (see FIG. 5(a)), where (a) shows the reflection characteristics, (b) shows the transmission characteristics, and (c) shows the characteristics during continuous adjustment of the transmission attenuation due to changes in post height. FIG. 7 is a graph showing the electromagnetic wave characteristics of the comparative model 2 (see FIG. 5(b)), where (a) shows the reflection characteristics, (b) shows the transmission characteristics, and (c) shows the characteristics during continuous adjustment of the transmission attenuation due to changes in post height. FIG. 8 is a graph showing the electromagnetic wave characteristics of the model of the present invention (see FIG. 5(c)), where (a) shows the reflection characteristics, (b) shows the transmission characteristics, and (c) shows the characteristics during continuous adjustment of the transmission attenuation due to changes in post height.

[0070] For the comparison model 1, as shown in Figures 6(a) and (b), both the transmission and reflection characteristics are flat from 200 to 350 GHz. As shown in Figure 6(c), the attenuation with respect to the change in height of the variable post 5 changes continuously in the range of 0.2 to 22 dB, and has little frequency dependency.

[0071] On the other hand, for the comparative model 2, as shown in Figures 7(a) and (b), a steep peak is observed due to multiple reflections caused by the leakage of electromagnetic waves from the support holes 311, and flatness is impaired. As for the amount of attenuation with respect to the change in height of the variable post 5, as shown in Figure 7(c), frequency dependence due to the loss of flatness is observed. Also, at 240 GHz, the attenuation range is narrowed to 0.2 to 17 dB, which indicates that loss is occurring due to leakage.

[0072] Furthermore, when a laminated choke structure is provided as in the present invention model, distortion is reduced and flatness is improved, as shown in FIG. 8(a). Similarly, in the present invention model, the attenuation with respect to the change in height of the variable post 5 is in the attenuation range of 0.2 to 20 dB, as shown in FIG. 8(c), with only a slight reduction in the maximum attenuation. By reducing leakage, a wide variable range is obtained, as in FIG. 6(c), and frequency dependency is also reduced.

[0073] Figure 9 shows the electric field intensity distribution in the central cross section parallel to the H plane, obtained from the calculation results of the characteristics shown in Figures 6 to 8. All of the electric field intensity distributions shown in Figure 9 are calculation results when the analysis frequency is 300 GHz, and the height h of the variable post 5 is 0.3 mm.

[0074] The following points can be inferred from the electric field intensity distribution shown in Fig. 9. In the structure of post support part P2 of comparative model 1, electromagnetic waves do not leak out into the open space part P3 below (see Fig. 9(a)), but in the structure of post support part P2 of comparative model 2, electromagnetic waves (represented by a cloud-like shape) leak out into the lower part (open space part P3) through the choke structure (see Fig. 9(b)).

[0075] Furthermore, in the structure of the post support part P3 (post movable holding part 8) of the model of the present invention, although there is some leakage of electromagnetic waves in the upper stacked part of the laminated plate part 3, the leakage of electromagnetic waves is suppressed as it moves to the lower stacked part, and the leakage of electromagnetic waves into the open space part P3 is greatly reduced, confirming that the corrugated choke structure is effectively functioning as a choke (see FIG. 9(c)).From the above, it can be understood that the choke structure based on the laminated structure of the unit plates of the present invention (laminated choke structure) is able to prevent the leakage of electromagnetic waves.

[0076] In the above embodiment (see Figs. 1 to 9), the waveguide block 2 is shaped like a rectangular parallelepiped, but in the present invention, the waveguide block 2 may have a shape other than a rectangular parallelepiped. In essence, the present invention comprises a waveguide block 2 in which a transmission line groove 21 is formed and opens toward the surface, a laminated plate portion 3 which is constructed by laminating a plurality of unit plates made of a conductor, in which a waveguide 21a is formed by the transmission line groove 23 and which covers the entire surface so that an insertion hole from the outside is formed, and a plate portion 3 which protrudes into the waveguide 21a via the insertion hole and protrudes into the insertion hole so that the amount of protrusion changes continuously. single As long as the waveguide block 2 has a configuration including a variable post 5 made of a conductive material that is driven to reciprocate in the stacking direction of the position plates 31 and 32, the shape of the waveguide block 2 is not limited.

[0077] When using a waveguide block 2 having a shape other than a rectangular parallelepiped, the shape of the laminated plate portion 3 will also be different, but even in this case, it is necessary to maintain the structure in which the cross-sectional shape of the insertion / removal hole in the post movable holding portion 8 changes gradually (as if drawing an envelope).

[0078] Furthermore, in the above embodiment, a configuration in which only one adjustable post 5 is provided is exemplified, but there may be a plurality of adjustable posts 5. In this case, the adjustable posts 5 may be provided so as to intersect with each other.

[0079] Thus, the variable attenuator 1 according to one embodiment of the present invention is configured by stacking a waveguide block 2 in which a transmission line groove 21 that opens toward the surface is formed, and a plurality of unit plates 31, 32 made of a conductor, the openings of which are closed except for a partial opening to form a waveguide 21a by the transmission line groove 23, and the laminated plate portion 3 that covers the entire surface so as to form an insertion hole from the outside that passes through the partial opening into the waveguide 21a by penetrating the plurality of unit plates 31, 32 in the stacking direction, and a plate portion 3 that protrudes into the waveguide 21a through the insertion hole and is inserted into the insertion hole so that the amount of protrusion changes continuously. singleand a variable post 5 made of a conductor that is driven to reciprocate in the stacking direction of the position plates 31, 32, and by continuously changing the amount of protrusion, the high-frequency signal transmitted through the waveguide 21a is continuously variably attenuated. The stacking plate portion 3 has an insertion hole that functions as a post movable holding portion 8 that holds the variable post 5 in a movable state in which it can be driven to reciprocate, and the cross-sectional shape of the insertion hole in the direction of the central axis changes in stages in the stacking direction.

[0080] With this configuration, the variable attenuator 1 according to this embodiment can easily fabricate the post movable holding part 8 simply by stacking the unit plates 31, 32 while improving the effect of preventing electromagnetic waves from leaking out from the gap between the post movable holding part 8 and the variable post 5 due to the structure of the post movable holding part 8 in which the cross-sectional shape in the central axis direction of the insertion / removal hole of the variable post 5 from the outside into the waveguide 21a changes stepwise in the stacking direction of the unit plates 31, 32. The ease of fabrication also makes it easy to manage dimensions, and it becomes possible to handle attenuation processing of signals in higher frequency bands, for example, millimeter wave bands or higher bands, by increasing the precision of machining.

[0081] Moreover, in the variable attenuator 1 according to this embodiment, the waveguide block 2 is formed of a rectangular parallelepiped block body in which a transmission line groove 21 having an opening is formed on one side surface 2c, and the stacking plate portion 3 is provided with a through hole 35 of a predetermined hole diameter or a through hole 36 of a hole diameter larger than the predetermined hole diameter for each unit plate 31, 32, and when all the unit plates 31, 32 are stacked, the through holes 35, 36 provided for each unit plate 31, 32 are stacked to form an insertion hole, and the insertion hole has a configuration in which the through holes 35 of the predetermined hole diameter and the through holes 36 of a hole diameter larger than the predetermined hole diameter are alternately arranged in the stacking direction to form a corrugated choke structure in which the hole diameter changes in stages.

[0082] With this configuration, the variable attenuator 1 of this embodiment has a post movable holding portion 8 which has a corrugated structure in which through holes 35 of a predetermined hole diameter and through holes 36 of a larger hole diameter are arranged alternately in the stacking direction, so that the required number of choke plates 31, 32 having through holes 35, 36 of different hole diameters are stacked to form a corrugated choke structure by stacking the through holes 35, 36 formed in each choke plate 31, 32, thereby enhancing the function of preventing electromagnetic wave leakage.

[0083] The movable post holder 8 having the above structure can be easily manufactured by forming through holes 35 of a predetermined diameter or through holes 36 of a larger diameter in each of the choke plates 31, 32 and stacking them. The machining precision of the through holes 35, 36 can be easily maintained even when machining with fine dimensions, and dimensional control is easy. The easy dimensional control makes it possible to handle attenuation processing of higher frequency bands, such as millimeter wave band signals, due to high-definition machining without reducing accuracy. With this configuration, while reducing leakage of electromagnetic waves from the movable post holder 8 that movably holds the variable post 5, the mechanism can be easily manufactured and dimensional control can be easily performed, and higher frequency bands can be handled.

[0084] Moreover, in the variable attenuator 1 according to this embodiment, the variable post 5 is configured as a member having a circular cross section, i.e., a cylindrical member, and the through holes 35, 36 are configured as circular holes. With this configuration, the variable attenuator 1 according to this embodiment is easily processed with high precision because the main task in forming the through holes in each unit plate is to make a circular hole. This makes it possible to maintain the machining accuracy and, for example, makes it easier to handle the attenuation process of millimeter wave band signals.

[0085] Moreover, in the variable attenuator 1 of this embodiment, the stacked plate portion 3 has a configuration in which a unit plate A (choke plate 31) having a through hole 35 of diameter X1 capable of holding the variable post 5 in a movable state and a unit plate B (choke plate 32) having a through hole 36 of diameter X2 larger than diameter X1 are stacked in multiple stages.

[0086] With this configuration, in the variable attenuator 1 of this embodiment, the laminated plate portion 3 is prepared by preparing the required number of choke plates 31, 32, each having through holes 35, 36 with different hole diameters, stacking each choke plate 31, 32 so that an insertion hole is formed, and arranging the variable post 5 so that the position of the insertion hole corresponds to the position of the variable post 5.This makes it possible to realize a highly precise post movable holding portion 8 that is simple in structure and easy to fabricate, yet has excellent ability to prevent electromagnetic wave leakage, and can also be used for attenuation processing of millimeter wave band signals.

[0087] In the above embodiment (see Figs. 1 to 9), the laminated plate section 3 is configured to have three choke plates 31 and two choke plates 32 stacked in five layers. In the present invention, the stacking form of the choke plates 31 and 32 in the laminated plate section 3 is not limited to the above-mentioned five layers, and it is also possible to have a structure in which more layers are stacked starting from one or more layers. In addition, in the laminated plate section 3, each choke plate 31 and 32 is not limited to one having one type of through hole, and may have two or more through holes with different hole diameters formed in multiple layers in the stacking direction (depth direction). In addition, as long as phase matching is satisfied, the thicknesses of the choke plates 31 and 32 do not have to be the same.

[0088] In light of the above, the configuration of the laminated plate portions 3A and 3B according to the modified example of the present invention will be described in detail below.

[0089] (Variation 1) The configuration of the laminated plate portion 3A according to the first modified example of the present invention is shown in Fig. 10. In Fig. 10, (a) shows the configuration of a cross section of a main part of the laminated plate portion 3A. As shown in Fig. 10(a), the laminated plate portion 3A according to the first modified example has a laminated structure in which two types of unit plates, a unit plate A1 (hereinafter referred to as a choke plate 31A) and a unit plate B1 (hereinafter referred to as a choke plate 32A), are stacked in three layers.

[0090] In the laminated plate section 3A shown in Fig. 10(a), the top choke plate 31A and the second and third choke plates 32A have the same planar shape, but are different in plate thickness and diameter and shape of the through hole. Choke plate 31A is, for example, the same as choke plate 31 (see Fig. 4(a)) constituting the post movable holding section 8 described in the above embodiment, and through hole 35A is also the same as through hole 35 of choke plate 31.

[0091] On the other hand, choke plate 32A has a plate thickness, for example, twice that of choke plate 31A, and is provided with through hole 36A penetrating in the thickness direction. Here, through hole 36A of choke plate 32A is composed of through hole lower step portion 36Ab having the same shape as through hole 35A of choke plate 31A and through hole upper step portion 36Aa having a larger diameter than through hole lower step portion 36Ab, and has a configuration in which through hole upper step portion 36Aa and through hole lower step portion 36Ab are connected in a stepped manner in the depth direction. More specifically, in the laminated plate portion 3A according to the first modification, the hole diameter (diameter in this example) of the through hole 35A of the choke plate 31A is X1 (see FIG. 10(b)) as illustrated in the above embodiment (see FIG. 4(b)), and the through hole 36A of the choke plate 32A has a two-stage structure of a through hole lower stage 36Ab having a diameter of X1 and a through hole upper stage 36Aa having a diameter of X2 (X2>X1). These through holes 35A, 36A (through hole upper stage 36Aa, through hole lower stage 36Ab) are arranged so as to be concentric circles centered at the same position on a plane (see FIGS. 10(b) and (c)).

[0092] As a result, in the stacked plate section 3A according to the first modification, when one choke plate 31A and two choke plates 32A are stacked as shown in Fig. 10(a), the through holes 35A, 36A (through hole upper stage 36Aa, through hole lower stage 36Ab) and 36A (through hole upper stage 36Aa, through hole lower stage 36Ab) of the choke plates 31A, 32A, 32A are arranged stepwise in the depth direction to form a post movable holding section 8A. Here, the through hole 35A of the choke plate 31A and the through hole lower stage 36Ab of each of the through holes 36A of the second and third choke plates 32A function as holding holes for the variable post 5, and the through hole upper stage 36Aa of each of the through holes 36A of the second and third choke plates 32A function as choke holes. The one through-hole of the post movable holding portion 8A as a whole is configured so that the hole diameters X1, X2, X1, X2, X1 change stepwise, that is, in a corrugated (wave) shape, in that order downward.

[0093] Here, if the plate thickness of the second and third choke plates 32A is, for example, twice that of the top choke plate 31A, and the through hole upper part 36Aa and the through hole lower part 36Ab are stepped at a position corresponding to, for example, half the plate thickness of the choke plate 32A, the laminated plate part 3A will realize a post movable holding part 8A having a laminated choke structure equivalent to the post movable holding part 8 consisting of five layers of the choke plates 31 and 32 in the laminated plate part 3 (see FIG. 4(a)) according to the above-mentioned embodiment. Therefore, the electromagnetic wave leakage prevention effect can be expected to be equivalent to the post movable holding part 8 in the laminated plate part 3 according to the above-mentioned embodiment.

[0094] According to the structure of the post movable holding part 8A of the laminated plate part 3A according to this modification 1, the choke plate 31A and the choke plate 32A in which the through hole 36A having a two-stage structure consisting of the through hole lower stage 36Ab and the through hole upper stage 36Aa, which have different diameters in the lamination direction, are laminated, so that the thickness of the unit plate B1 is increased and the strength of the laminated plate part 3A can be increased. In addition, the total number of plates is only three, which has the effect of reducing the number of plates.

[0095] In the first modification, a configuration example is given in which two choke plates 32A having through holes 36A consisting of two stages (upper through hole portion 36Aa and lower through hole portion 36Ab) are stacked, but in the present invention, the number of through holes of different diameters provided in one choke plate (unit plate) is not limited to two stages, and may be more than two stages. In addition, the number of stacked choke plates having multiple stages of through holes of different diameters may be two or more. In addition, as long as phase matching is satisfied, the thickness of each choke plate 31A and 32A can be set freely as appropriate, and further, the positional relationship between the upper through hole portion 36Aa and the lower through hole portion 36Ab of the two-stage through hole 36 may be set freely as appropriate.

[0096] In this way, the laminated plate portion 3A of the first modified example has a configuration in which a unit plate A1 (choke plate 31A) having a through hole 35A of diameter X1 capable of holding the adjustable post 5 in a movable state is stacked in multiple stages, and a unit plate B1 (choke plate 32A) having a two-stage through hole 36A in which a lower through hole portion 36Ab of diameter X1 and an upper through hole portion 36Aa of diameter X2 larger than diameter X1 are connected in the stacking direction.

[0097] According to the configuration of the laminated plate part 3A of variant example 1, in which a choke plate 31A (unit plate A1) and a choke plate 32A (unit plate B1) are stacked, in which a two-stage through hole 36A is formed, consisting of a lower through hole portion 36Ab and an upper through hole portion 36Aa whose diameters differ in the stacking direction, the thickness of the choke plate 32A is increased, thereby increasing the strength of the laminated plate part 3.

[0098] (Variation 2) The configuration of the laminated plate portion 3B according to the second modified example of the present invention is shown in Fig. 11. In Fig. 11, (a) shows the configuration of the main part of the laminated plate portion 3B in cross section. As shown in Fig. 11(a), the laminated plate portion 3B according to the second modified example has a laminated structure in which six types of unit plates, namely, unit plate A2 (hereinafter, referred to as choke plate 37A), unit plate B2 (hereinafter, referred to as choke plate 37B), unit plate C2 (hereinafter, referred to as choke plate 37C), unit plate D2 (hereinafter, referred to as choke plate 37D), unit plate E2 (hereinafter, referred to as choke plate 37E), and unit plate F2 (hereinafter, referred to as choke plate 37E), are stacked in 13 layers using two sets (three unit plates A2 only).

[0099] Here, the six types of choke plates 37A, 37B, 37C, 37D, 37E, and 37F have the same planar shape and plate thickness, and only the hole diameters (diameters in this example) of the through holes 38A, 38B, 38C, 38D, 38E, and 38F are different. The diameters of the through holes 38A, 38B, 38C, 38D, 38E, and 38F of the choke plates 37A, 37B, 37C, 37D, 37E, and 37F are X11, X12, X13, X14, X15, and X16 (X11<12), respectively, as shown in Figures 11(b), (c), (d), (e), (f), and (g). <X13<X14<X15<X16)である。

[0100] The diameters of the through holes 38A, 38B, 38C, 38D, 38E, and 38F may be set to appropriate values ​​in consideration of the stepped cross-sectional shape (corrugated pattern) of the through holes realized by laminating the six types of choke plates 37A, 37B, 37C, 37D, 37E, and 37F. The through holes 38A, 38B, 38C, 38D, 38E, and 38F are arranged in a concentric circle with the same center on a plane (see Figs. 11(b), (c), (d), (e), (f), and (g)).

[0101] In the laminated plate section 3B according to the second modification, for example, as shown in FIG. 11(a), the set of six types of choke plates 37A, 37B, 37C, 37D, 37E, 37F from the top choke plate 37A to the sixth choke plate 37F from the top are laminated on the premise that the diameters increase in sequence. Similarly, another set of six types of choke plates 37A, 37B, 37C, 37D, 37E, 37F from the seventh choke plate 37A from the top to the second choke plate 37F from the bottom are laminated on the premise that the diameters increase in sequence in the same pattern as the set of six types of choke plates 37A, 37B, 37C, 37D, 37E, 37F above. At the bottom of the laminated plate section 3B, the same choke plate 37A as the top and seventh from the top is laminated.

[0102] As a result, in the laminated plate portion 3B of variant example 2 shown in Figure 11(a), the cross-sectional shape of a single through hole in the post movable holding portion 8B as a whole has a diameter that increases in six stages downward, from X11, X12, X13, X14, X15, and X16, and after the diameter reaches X16, the diameter suddenly decreases to X11, and then the diameter increases in six stages downward, from X11, X12, X13, X14, X15, and X16, and finally, the diameter suddenly decreases from X16 to X11.

[0103] In this way, the stacked plate portion 3B of the second modified example has two sets of six types of choke plates 37A, 37B, 37C, 37D, 37E, 37F, each of which has a different diameter of through holes 38A, 38B, 38C, 38D, 38E, 38F that can hold the adjustable post 5 in a movable state, and the two sets of six types of choke plates 37A, 37B, 37C, 37D, 37E, 37F are stacked periodically in the stacking direction in the same order for each set (the order in which the diameters of the through holes 38A, 38B, 38C, 38D, 38E, 38F increase in order).

[0104] The configuration of the laminated plate part 3B according to the second modification allows for more minute and gradual changes in the cross-sectional shape of the corrugated pattern, and increases the degree of freedom in design, compared to the configurations of the laminated plate part 3 according to the above embodiment (see FIG. 4) and the laminated plate part 3A according to the first modification (see FIG. 10). This makes it easier to realize a cross-sectional shape that is more effective in reducing the leakage of electromagnetic waves, and as a result, it becomes possible to further reduce the leakage of electromagnetic waves.

[0105] Figure 11 shows an example of the configuration of the stacked plate portion 3B in variant example 2, in which six types of two sets of choke plates 37A, 37B, 37C, 37D, 37E, 37F are used, and a stacked state in which the diameters of the through holes 38A, 38B, 38C, 38D, 38E, 38F increase in order for each set is repeated twice (two periods).

[0106] The configuration of the laminated plate portion 3B according to the modified example 2 is not limited to that shown in FIG. 11. For example, the number of types (planar shape, thickness, diameter of through hole, etc.) and the number of sets of choke plates can be appropriately set according to the desired cross-sectional shape (corrugated pattern), etc. In the example of FIG. 11, an example is given in which a laminated state in which the diameter of the through hole increases in sequence for each set is repeated twice (two periods), but conversely, a configuration in which a laminated state in which the diameter of the through hole decreases in sequence for each set is repeated multiple times (multiple periods) may be used. Furthermore, a corrugated pattern in which a pattern in which the diameter gradually increases and then decreases (a sinusoidal wave-shaped change pattern) is repeated multiple times may be adopted. In any corrugated pattern, the thickness of the choke plate is not limited to a uniform configuration, and the change in the diameter is not limited to a pattern in which the change in diameter changes sequentially. In addition, the present invention may be a structure in which the laminated choke structure of the laminated plate portion 3B is a combination of the modified examples 2 and 3 described above, and various other modifications or applications are possible.

[0107] In this way, the stacked plate portion 3B of the second modified example has two sets of six types of choke plates 37A, 37B, 37C, 37D, 37E, 37F (choke plate 37A has three plates only), each of which has through holes 38A, 38B, 38C, 38D, 38E, 38F with different diameters that can hold the adjustable post 5 in a movable state, and has a configuration in which the two sets of six types of choke plates 37A, 37B, 37C, 37D, 37E, 37F are stacked periodically in the stacking direction in the same order for each set.

[0108] According to the configuration of the laminated plate portion 3B of the second modification, six types of choke plates 37A, 37B, 37C, 37D, 37E, 37F, each having a different diameter of through holes 38A, 38B, 38C, 38D, 38E, 38F, are grouped together, and two sets of choke plates 37A, 37B, 37C, 37D, 37E, 37F are periodically stacked in the same order for each set. This allows for a more finely gradated change in the cross-sectional shape, increases the freedom of design, and makes it possible to further reduce the leakage of electromagnetic waves. [Industrial Applicability]

[0109] As described above, the variable attenuator according to the present invention has the advantage that it is easy to create and manage the dimensions of the mechanism that movably holds the post while reducing electromagnetic wave leakage, and is also compatible with higher frequency bands, and is useful as a variable attenuator in general for use in communication terminals, signal analysis devices, etc. that handle millimeter wave band signals. [Explanation of symbols]

[0110] 1 Variable Attenuator 2 Waveguide Block 2c One side (bottom) of the waveguide block 3. Laminated plate section 5 Adjustable Post 8 Post movable holding part (insertion hole) 21 Transmission line groove 21a waveguide 31 Choke plate (unit plate, unit plate A) 31A Choke plate (unit plate, unit plate A1) 32 Choke plate (unit plate, unit plate B) 32A Choke plate (unit plate, unit plate B1) 35, 35A through hole 36 Through hole 36A through hole 36Aa Upper part of through hole 36Ab Lower part of through hole 37A, 37B, 37C, 37D, 37E, 37F Choke Plates (Unit Plates A2, B2, C2, D2, E2, F2) 38A, 38B, 38C, 38D, 38E, 38F through hole

Claims

1. A waveguide block (2) in which a transmission line groove (21) is formed and opens toward the front surface; a laminated plate portion (3) configured by laminating a plurality of unit plates (31, 32) made of a conductor, the openings being closed except for a partial opening to form a waveguide (21a) using the groove for the transmission line, and covering the entire surface so that an insertion hole is formed from the outside through the partial opening to the inside of the waveguide, penetrating the plurality of unit plates in the lamination direction; a variable post (5) made of a conductive material that protrudes into the waveguide through the insertion hole and is driven to reciprocate within the insertion hole in the stacking direction of the unit plates so that the amount of protrusion is continuously changed; A variable attenuator (1) for continuously attenuating a high-frequency signal transmitted through the waveguide by continuously changing the protrusion amount, The stacking plate portion has a structure in which the insertion hole functions as a post movable holding portion (8) that holds the variable post in a movable state capable of the reciprocating drive, and the cross-sectional shape of the insertion hole in the central axis direction changes stepwise in the stacking direction, the waveguide block is formed of a rectangular parallelepiped block body having the transmission line groove with the opening on one side surface (2c); The stacking plate portion has a through hole (35) having a predetermined hole diameter or a through hole (36) having a hole diameter larger than the predetermined hole diameter provided for each unit plate, When all the unit plates are stacked, the through holes provided in each of the unit plates are stacked to form the insertion hole, The variable attenuator is characterized in that the insertion holes are arranged alternately in the stacking direction, with the through holes having the specified hole diameter and the through holes having a hole diameter larger than the specified hole diameter, to form a corrugated choke structure in which the hole diameter changes in stages.

2. The variable post is formed of a cylindrical member, 2. The variable attenuator according to claim 1, wherein the through hole has a circular shape.

3. The variable attenuator according to claim 2, characterized in that the laminated plate portion has a configuration in which a unit plate A (31) having a through hole with a diameter capable of holding the variable post in the movable state and a unit plate B (32) having a through hole with a diameter larger than the diameter of the through hole of the unit plate A are laminated in multiple stages.

4. The variable attenuator of claim 2, characterized in that the laminated plate portion has a configuration in which a unit plate A1 (31A) having a through hole with a diameter capable of holding the variable post in the movable state, and a unit plate B1 (32A) having a two-stage through hole (36A) formed therein, in which a lower through hole portion (36Ab) having a diameter equal to the diameter of the through hole of the unit plate A1 and an upper through hole portion (36Aa) having a diameter larger than the diameter of the through hole of the unit plate A1 are connected in the stacking direction, and the laminated plate portion is configured to be stacked in multiple stages.

5. The variable attenuator of claim 2, characterized in that the stacked plate portion has multiple sets of multiple types of unit plates A2, B2, C2, D2, E2, F2 (37A, 37B, 37C, 37D, 37E, 37F) in which through holes (38A, 38B, 38C, 38D, 38E, 38F) having different diameters that can maintain the variable post in the movable state are formed, and the multiple types of unit plates are periodically stacked in the stacking direction in the same order for each set.

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