JP2005341491A - Filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter of having a structure as discharge or leakage of electromagnetic waves will not take place, even when the filter is used for high power, and passband center frequency can be regulated. <P>SOLUTION: The filter has a structure with at least one movable metal wall 4 provided on one wall face 1 of a cavity resonator 10, one end 5b of a support 5 for supporting the movable metal wall 4 led out from the one wall face 1 of the cavity resonator 10 to the outside of the cavity resonator 10, and a means 7 for moving the support 5 provided on one end side 5b of the support 5 so that the passband center frequency can be varied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a filter using a cavity resonator for microwaves or millimeter waves that passes a desired frequency band and blocks unnecessary frequency bands. More specifically, the present invention relates to a filter having a structure provided with means for adjusting the passband center frequency while suppressing troubles such as discharge.

  Conventionally, a band-pass filter using a cavity resonator has a structure shown in a conceptual diagram in FIG. This is a structure in which a window member 32 is inserted into a rectangular waveguide 31, and the window member 32 acts as an inductive resonance window (reactance element). Arranged at intervals. A cavity is formed by a space surrounded by the two resonance windows adjacent to each other in the longitudinal direction and the tube wall of the rectangular waveguide 31. The space between the resonance windows adjacent in the longitudinal direction and the size of the resonance window ( The window member 32 is provided so that a desired band characteristic can be obtained by the distance between the pair of window members). In the example shown in FIG. 8, three-stage cavity resonators are connected. In FIG. 8, 33 is a stub for adjusting the passband center frequency. By configuring a filter by connecting a plurality of cavity resonators in this manner, the attenuation amount of the stop band is drastically increased, that is, in the pass band, compared to configuring a filter with a single cavity resonator. It is possible to configure a filter that can obtain a large attenuation at a close stop frequency (see, for example, Patent Document 1).

  As described above, such a cavity resonator has a resonance frequency (passage) depending on the interval between the resonance windows adjacent in the longitudinal direction, the size of the resonance window, the width and height of the waveguide constituting the cavity, and the like. In some cases, it is necessary to adjust the passband center frequency depending on a change in temperature during operation, an environmental temperature at which a circuit including a filter is installed, or the like. The adjustment of the passband center frequency due to variations at the time of manufacturing is performed by changing the insertion length of the stub 33 in the cavity of FIG. As shown in FIG. 9 or FIG. 10, there is known a configuration in which the insertion length of the stub 33 is automatically made variable in accordance with a temperature change.

  The structure shown in FIG. 9 is such that the tip of the stub 33 fixed to the bimetal 36 is inserted into a cavity resonator 37 from one wall surface (cavity wall) of the waveguide 35 (for example, a patent). Reference 2). With this structure, if the insertion length of the stub 33 is adjusted so that the desired passband center frequency is obtained at room temperature, when the temperature of the waveguide rises, for example, the waveguide expands due to a temperature rise of a metal or the like. If the bimetal 36 is formed so as to warp outward, the stub 33 is pulled out from the cavity resonator 37, the capacity with the facing surface is reduced, and the temperature rises. Thus, the member constituting the cavity resonator 37 functions to cancel the action of expanding due to thermal expansion and lowering the passband center frequency.

Further, the structure shown in FIG. 10 is a stub through a driving material 38 having a constant change amount larger than the thermal expansion of the waveguide with respect to a temperature change, such as a material having a large thermal expansion coefficient or a shape memory alloy. By fixing 33, it is a structure which compensates the change of the band center frequency by a temperature change (for example, refer patent document 3).
JP 2001-230603 A JP-A-8-148903 (FIG. 1) JP-A-9-275304 (FIG. 1)

  As described above, in the waveguide type filter using the cavity resonator, in order to adjust the passband center frequency, a stub is inserted into the cavity from the center of the wide surface of the waveguide, This is done by adjusting the insertion length, and also when compensating for changes in the passband center frequency due to temperature changes, a method is used that automatically changes the insertion length of the stub in response to temperature changes. It has been. However, this stub is inserted by inserting it into the central portion of the wide surface of the waveguide where the change in the passband center frequency is most remarkable with respect to the change in the insertion length. Therefore, the place where the stub is inserted is the place where the electric field of the waveguide is the largest, and there is a problem that electric discharge tends to occur at the tip of the stub. Moreover, since the tip of the stub is sharp or formed like a protrusion with a screw, the electric field is concentrated and discharge tends to occur. In order to concentrate more, there exists a problem that a power-proof characteristic falls.

  On the other hand, in a filter used for high power ranging from 2 kW to 100 kW in a radar device or the like, not only is it easy to discharge at the tip of the stub, but also a stub as shown in FIG. 9 or FIG. In order to make it slide, it is necessary to form a gap between the waveguide wall and the stub, and it is easy for discharge to occur in the gap, and damage to the inner wall surface of the waveguide if discharge is caused by high power There is. Furthermore, if there is such a gap, electromagnetic waves leak from the gap, causing problems such as noise to surrounding electrical equipment, and increasing insertion loss. However, when used in a radar apparatus, the usage environment ranges from a low temperature of about −30 ° C. to a high temperature of 100 ° C. or more. For example, the filter having the structure shown in FIG. 8 in the X band has a negative temperature characteristic of −50 to −300 kHz / ° C. as shown in FIG. Note that the difference between the two characteristics shown in FIG. 11 is based on the difference in the expansion coefficient of the filter material. When a filter having such a negative temperature characteristic is used in a place having a different temperature as described above, it will also vary by −6.5 to −39 MHz, and the filter characteristic due to the change of the band center frequency will be changed. It is indispensable to provide an automatic temperature compensation means because a decrease cannot be avoided.

  The present invention has been made to solve such a problem, and is a structure that can adjust the passband center frequency without causing discharge or electromagnetic wave leakage even when used for high power. An object of the present invention is to provide a filter.

  Another object of the present invention is to provide a filter having a structure capable of compensating for fluctuations in the passband center frequency even when temperature changes occur.

  The filter according to the present invention is a filter that allows a desired frequency band to pass through a cavity resonator and blocks an unnecessary frequency band. At least one movable metal wall is provided on one wall surface of the cavity resonator. One end portion of the support member that supports the metal wall is led out of the cavity resonator from one wall surface of the cavity resonator, and moving means for moving the support member is provided on one end portion side of the support member. Thus, the structure is such that the passband center frequency can be varied.

  Here, the support that supports the movable metal wall includes not only the case where the movable metal wall and the support are fixed, but also the case where the support supports the movable metal wall while rotating without being fixed. Meaning. When not fixed, the movable metal wall has a certain degree of elasticity, and when the insertion length of the support is reduced, the movable metal wall returns to and contacts the tip of the support due to the elasticity of the movable metal wall. Formed as follows. In addition, the metal wall of the movable metal wall does not need to be a complete metal plate, but only needs to have a metal surface on the cavity side, and includes, for example, a metal plate or metal plating on one surface such as a resin plate. Meaning. Further, the moving means means means for fixing the support so that the support can be moved relative to one wall surface of the cavity resonator.

  The moving means is a means for automatically changing the position of the movable metal wall in accordance with the temperature change so as to compensate for the change in the passband center frequency due to the temperature change. Is preferable because the passband center frequency can be automatically adjusted.

  According to the filter of the present invention, even if there is a convex portion, by moving the plate-shaped metal wall, the center frequency of the passband is adjusted, so even if the metal wall moves where the electric field is strong, Even with high power, there is no sharp point and no discharge occurs. In addition, since the support that supports the moving metal wall exists outside the cavity with respect to the metal wall, it is not exposed to electromagnetic waves, and there is a gap for sliding between one wall surface of the cavity. However, no electromagnetic wave leaks or discharges in the gap. In addition, since the metal wall moves, it moves over a wide range, and even a slight change allows a relatively large frequency adjustment, and sufficiently compensates for a frequency change due to a temperature change. Can do.

  Next, the filter of the present invention will be described with reference to the drawings. The filter according to the present invention has one wall surface of the cavity resonator 10 as shown in FIGS. 1 (a) and 1 (b). 1, at least one movable metal wall 4 is provided, and one end portion 5b of the support 5 supporting the movable metal wall 4 is led out of the cavity resonator 10 from one wall surface 1 of the cavity resonator 10, A moving means 7 for moving the support 5 is provided on one end side 5b of the support 5 so that the passband center frequency can be varied.

  In the example shown in FIG. 1, the cavity resonator 10 is a waveguide type resonator formed by a window member and a waveguide provided in the waveguide as shown in FIG. However, the present invention is not limited to the waveguide type, and may have a resonator structure. In the example shown in FIG. 1, a structure in which window members provided at a predetermined interval are omitted is shown. Further, FIG. 1 (b) is shown in a view in which the support 5 is located on the lower side by reversing the top and bottom of FIG. 1 (a) in order to make it easy to understand the convex portion 4a of the movable metal wall 4. However, one wall surface 1 of the resonator 10 is one of the wide surfaces of the waveguide. As described with reference to FIG. 8, the window member (not shown) has a resonance frequency that changes depending on the interval between the window members adjacent to each other in the axial direction (the propagation direction of the electromagnetic wave), the interval between the pair of window members, and the like. Designed to have a band center frequency. Further, the window member is not limited to a structure extending from both ends of the wide surface of the waveguide to the center side as shown in FIG. 8, and may be a structure provided only on one end side, or a wide surface. It is also possible to use a structure that narrows the distance between the first and second resonators.

  Such a waveguide and window member are made of, for example, a metal material such as aluminum or an alloy thereof, which is manufactured by die casting or the like with a structure in which the one wall surface 1 side is opened and the movable metal wall 4 is joined. The window member and the movable metal wall 4 can be formed on a waveguide formed by drawing or the like.

  The movable metal wall 4 is preferably flexible and elastic because it is easily deformable and has a restoring force. For example, the same metal plate as aluminum such as a waveguide has a thickness of about 1 mm or less. By making it thin, flexibility can be provided. Also, not only a metal plate, but also a metal plate or metal plating on one surface such as a resin plate can be used as a movable metal wall as long as the metal foil side faces the cavity side, A material having a small thermal expansion coefficient is preferred. By using an elastic material, the movable metal wall 4 is automatically attached to the support 5 when the support 5 is retracted without bonding the support 5 and the movable metal wall 4 described later. Since it returns until it contacts, it is preferable.

  Further, when the amount of deformation of the movable metal wall 4 is large, as shown in FIG. 1 (b), a convex portion 4a is formed in advance so as to protrude into the resonator without being deformed. Since it is close to the center of the cavity, the frequency can be adjusted greatly even for a slight amount of deformation. Even if such a convex portion 4a is formed, unlike insertion of a stub such as a screw, it does not stand vertically with respect to one wall surface 1, but becomes a smooth convex portion, so that discharge and the like are unlikely to occur. Furthermore, the amount of change in frequency can be increased. Furthermore, in the example shown in FIG. 1, the movable metal wall 4 is attached to almost the entire surface of the one wall surface 1 of the cavity resonator 10, but the support body 5 may be covered even if it is not the entire surface. It may be provided in the vicinity thereof.

  As for the support body 5, the front-end | tip part 5a contacts the back surface side of the movable metal wall 4, and the one end part 5b is derived | led-out outside the resonator. The tip 5a of the support 5 and the movable metal wall 4 may be bonded and fixed, and the support 5 slides while contacting the movable metal wall 4 as in the example shown in FIG. For example, it can also comprise so that the support body 5 can rotate with a screw | thread etc. FIG. The support 5 is inserted so as to be able to slide in the through hole 1 a of the one wall surface 1 of the cavity resonator 10. On the side of the one end portion 5b of the support body 5, there is provided a moving means 7 for moving the support body 5 while sliding in the through hole 1a.

  The moving means 7 means means for fixing the support so that the support can be moved relative to the one wall surface. In the example shown in FIG. 1, the nut 7 a is fixed to the outer surface of the one wall surface 1. The example of the structure which consists of a thing and moves the support body 5 to the orthogonal | vertical direction by rotating the support body 5 comprised with the bis | screw is shown. In the case of this structure, when the movable metal wall 4 is elastic and the support body 5 is retracted, the movable metal wall 4 returns to the distal end portion 5a side of the support body 5 due to the elasticity, and the distal end portion The structure needs to be in contact with 5a. That is, by rotating the support 5, the insertion length is changed, and the movable metal wall 4 is moved accordingly. However, the moving means 7 is not limited to such a structure. For example, the supporting means 5 and the movable metal wall 4 are bonded and fixed, and the supporting means is obtained by rotating the nut while preventing the nut from moving up and down. 5 may be moved up and down, or a means that can be moved up and down while holding the support 5 such as a configuration in which the support 5 can be moved up and down mechanically without using a screw. Can be used.

  According to the present invention, since the center frequency of the pass frequency band is adjusted by moving the movable metal wall 4, the stub is inserted into the cavity resonator and the insertion length is changed. Unlike the above, the wall surface of the resonator cavity moves. For this reason, the sharp part like the insertion of a stub is inserted into the resonator and the electric field is not disturbed locally. A filter is obtained. Moreover, the moving means of the movable metal wall 4 can be performed with a simple structure of screws and nuts as in the prior art, and the frequency characteristics can be adjusted very easily.

  Furthermore, according to the present invention, even if a gap for sliding is formed between one wall surface 1 of the cavity resonator 10 and the support body, the support body 5 is outside the movable metal wall 4. Because it is electrically isolated from the resonator, discharge occurs in the gap, part of the electromagnetic wave leaks from the gap, or high-frequency current is blocked by a through hole provided on one wall surface, increasing insertion loss That doesn't happen either. In other words, one wall surface of the resonator is constituted by the movable metal wall 4 instead of the waveguide wall, and the movable metal wall 4 has neither a through hole nor a slit. There is nothing to cut off and insertion loss can be greatly reduced.

  FIG. 2 is an explanatory view similar to FIG. 1 showing an example in which the moving means 7 is configured so that the movable metal wall 4 automatically moves according to a change in temperature. That is, in the example shown in FIG. 2, the moving means 7 is formed by forming one wall surface of the waveguide (resonance cavity) by the elastic member 7 b having a larger coefficient of thermal expansion than the other wall surface of the waveguide. The front end 5a of the support 5 is bonded and fixed to the back side of the movable metal wall 4, and the other end 5b is bonded and fixed to the outer surface of the elastic member 7b. The expansion / contraction member 7b may be any member that has a large coefficient of thermal expansion and is more rigid than the movable metal wall 4, and may be non-metallic as long as the movable metal wall 4 is provided on the entire surface of one wall surface. As the elastic member 7b, for example, Teflon (registered trademark) having a large coefficient of thermal expansion can be used. In addition, since the temperature coefficient of the resonant cavity 1 is known in advance, the elastic member 7b cancels the change in frequency due to the temperature of the resonant cavity by adjusting its thermal expansion coefficient and thickness. Can be formed.

  With the structure shown in FIG. 2, when the temperature of the filter rises due to conduction of heat generated by the operation of a magnetron or when the temperature of the filter rises, such as when used in a high temperature atmosphere, The entire resonator is uniformly increased due to thermal expansion, the resonance frequency is lowered, and the passband center frequency is also lowered. However, when the temperature rises, the elastic member 7b expands further than the expansion of the resonator, so that the support body 5 fixed to the outer surface of the elastic member 7b is pulled outward. As a result, the support 5 moves in the direction in which it is pulled out of the resonator, and the movable metal wall 4 is also pulled outwards accordingly. As a result, the capacitance formed between the convex portion of the movable metal wall 4 and the opposing surface is reduced, and the resonance frequency (passband center frequency) is increased. That is, the operation of compensating for the effect of lowering the passband center frequency due to temperature rise is performed.

  FIG. 3 is a cross-sectional explanatory view similar to FIG. 2 showing a modification of FIG. That is, in FIG. 3, the resonator 10 is formed of a waveguide as in the example shown in FIG. 1, the movable metal wall 4 is provided on the inner surface of the one wall surface 1, and the cylinder is formed on the outer surface of the one wall surface 1. The one end 5b side of the support 5 is led out of the resonator 10 through the through hole 71 of the elastic member 7c and the through hole 1a formed in the one wall surface 1, and one end thereof is provided. The moving means 7 is formed by bonding and fixing the portion 5b to the outer surface of the elastic member 7c. The distal end portion 5a of the support 5 is bonded and fixed to the back surface of the movable metal wall 4 as in the example shown in FIG.

  Even in such a structure, as with the structure shown in FIG. 2 described above, when the temperature changes, the change in the elastic member 7c is larger than the deformation due to the temperature change of the cavity resonator 10, and the cavity resonator 10 The movable metal wall 4 is moved by the deformation due to the temperature change of the expansion / contraction member 7c with respect to the change in the passband center frequency due to the temperature change, and the frequency change can be offset. That is, the example shown in FIG. 3 is the same as the example shown in FIG. 2 except that the elastic member 7c is provided, but according to this example, the elastic member 7c is a resonator. Since it is not necessary to form one wall surface, there is no restriction on the size and shape, and the material can be selected only from the viewpoint that it is more rigid than the movable metal wall 4 and has a large thermal expansion coefficient. Furthermore, the frequency can be corrected more sensitively by increasing the length of the cylindrical portion. Also in this case, the amount of deformation is adjusted so that the amount of change due to temperature substantially matches the amount of change in the resonance frequency of the resonator.

  The above-described examples shown in FIGS. 2 and 3 are shown as examples of frequency adjustment by temperature compensation, but it goes without saying that frequency adjustment by temperature compensation can be performed while adjusting the frequency by variation during manufacturing. . An example is shown in FIG. That is, the example shown in FIG. 4 is a structure in which the structures of FIGS. 1 and 3 are combined, and the support body 5 is made of screws by fixing the nut 7a to the upper surface of the elastic member 7c of FIG. By adopting this structure, for example, by adjusting the insertion length of the support 5 at room temperature to adjust the desired frequency to be the passband center frequency, when the temperature subsequently changes The expansion / contraction member 7c expands / contracts according to the temperature change to compensate for the change in the passband center frequency, and functions as a filter that allows a desired passband center frequency to pass and blocks other frequency bands.

  The example shown in FIG. 5 is a diagram similar to the above-described examples showing still other examples of the moving means for performing temperature compensation. That is, in the example shown in FIGS. 2 to 4, the support 5 is moved by the elastic member that expands and contracts according to the temperature change, but the example shown in FIG. 5 is an example using a bimetal. In FIG. 5, 7d is a bimetal used as the moving means 7, and it has an arc shape in which members having different temperature coefficients are joined so that when the temperature rises, it extends upward in the figure and contracts downward in the figure when the temperature decreases. One end 5b of the support 5 is fixed to the upper surface of the bimetal 7d. As a result, the warp of the bimetal 7d changes according to the temperature change, and the support body 5 moves up and down accordingly, and the wall surface of the movable metal wall 4 moves. Also in this case, the amount of deformation is adjusted so that the amount of change due to temperature substantially matches the amount of change in the resonance frequency of the resonator. In FIG. 5, the same parts as those in FIG. Further, even in this case, it goes without saying that adjustment means other than temperature compensation can be used together as shown in FIG.

  The measurement result of the insertion loss A with respect to the frequency of the filter having the structure shown in FIG. 1 is compared with the insertion loss B of the filter having the same passband center frequency formed by the filter having the structure shown in FIG. As shown in FIG. As is apparent from FIG. 6, the insertion loss in the passband of the conventional filter is -0.4 dB, but according to the filter of the present invention, the insertion loss is improved to -0.25 dB. I understand. In FIG. 6, the insertion loss due to the present invention and the insertion loss due to the filter having the conventional structure overlap each other at the attenuation frequency portion.

  Further, FIG. 7 shows the result of examining the change in the passband center frequency when the filter temperature is changed from −20 ° C. to 100 ° C. using the filter having the structure shown in FIG. As is apparent from FIG. 7, the change in the frequency with the temperature rise is −20 kHz / ° C., which is very stable compared to −50 to −300 kHz / ° C. when temperature compensation is not performed. .

  As described above, according to the present invention, the frequency adjusting mechanism can be provided without causing an increase in insertion loss and a problem of discharge, and a very high performance filter can be obtained. As a result, even with a filter used for high power, temperature compensation can be performed, and the filter is very stable with respect to temperature.

It is a figure explaining one Embodiment of the filter by this invention. It is a figure explaining other embodiment of the filter by the present invention. It is a figure which shows the modification of the structure shown by FIG. It is a figure explaining other embodiment of the filter by the present invention. It is a figure which shows the modification of the structure shown by FIG. It is a figure which shows the insertion loss of the filter shown by FIG. 1 of this invention in contrast with the insertion loss of the filter of a conventional structure. It is a figure of the result of having measured the change of the passband center frequency with respect to the temperature change of the filter shown by FIG. It is a figure which shows the structural example of the conventional filter. It is a figure which shows the structural example which performs the temperature compensation of the conventional filter. It is a figure which shows the other structural example which performs the temperature compensation of the conventional filter. It is a figure of the result of having measured the change of the passband center frequency with respect to the temperature change by the conventional filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 One wall surface 4 Movable metal wall 5 Support body 7 Moving means 7a Nut 7b, 7c Elastic member 7d Bimetal 10 Cavity resonator

Claims (2)

  In a filter that allows a desired frequency band to pass through a cavity resonator and blocks unnecessary frequency bands, at least one movable metal wall is provided on one wall surface of the cavity resonator, and supports the movable metal wall One end portion of the body is led out of the cavity resonator from one wall surface of the cavity resonator, and a moving means for moving the support body is provided on the one end portion side of the support body, thereby providing a passband center frequency. A filter with a structure that can be varied.   2. The filter according to claim 1, wherein the moving means is means for automatically changing a position of the movable metal wall in accordance with the temperature change so as to compensate for a change in the passband center frequency due to a temperature change.

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