Abstract:
Various exemplary embodiments relate to a tuning element assembly and method for tuning an a radio frequency (RF) component, where the component has one or more walls defining a cavity, with at least one wall having at least one bore hole. A bushing is mounted in the bore hole in the wall, and a tuning element is slidably mounted and received in the bushing so that the tuning element projects inwardly through the bushing and into the cavity and is axially adjustable. A method of tuning an RF component also includes providing a bushing mounted in a bore in a wall of the RF component, sliding a tuning element that is slidably mounted and received in the bushing so that the tuning element projects inwardly through the bushing and into the cavity by a distance varying according to the sliding of the tuning element, monitoring a performance characteristic of the RF component, and releasing the tuning element so that a desired performance characteristic is achieved.

Description:
TECHNICAL FIELD 
     Various exemplary embodiments disclosed herein relate generally to radio-frequency (RF) components and tuning elements therefor. More particularly, some various embodiments relate to moveable tuning elements that are moved relative to a cavity of the component order to provide tuning adjustment. 
     BACKGROUND 
     Various radio-frequency (RF) components are known that utilize a cavity as well as other features, such as for example one or more resonators, in the cavity. Some of these components may be used as filters. Often, it is desirable to adjust the characteristics of the cavity via a moveable tuning element that projects at least partially into the cavity. In the past, these moveable tuning elements have taken the form, for example, of a bendable plate placed inside the cavity, or a threaded screw that projects through a threaded bore in an outside wall of the cavity. Bending of the plate, or turning of the screw in order to cause the screw to be advanced into or retracted from the cavity, have been performed in order to change the configuration of the tuning element within the cavity. 
     While the known devices and methods have proved generally satisfactory, they each have certain disadvantages in practice, and it is desired to provide an improved tuning element and method that can be used to efficiently and conveniently tune a RF component having a cavity. 
     SUMMARY 
     In light of the present need for an improved tuning element assembly and method that can be used to efficiently and conveniently tune an RF component having a cavity, a brief summary of various exemplary embodiments is presented. Some simplifications and omissions may be made in the following summary, which is intended to highlight and introduce some aspects of the various exemplary embodiments, but not to limit the scope of the invention. Detailed descriptions of at least one preferred exemplary embodiment adequate to allow those of ordinary skill in the art to make and use the inventive concepts will follow in later sections. 
     Various exemplary embodiments relate to an improved tuning element assembly and method that can be used to efficiently and conveniently tune an RF component having a cavity. 
     One embodiment relates to an apparatus for tuning a radio frequency (RF) component having a wall with a bore through the wall, and a cavity, comprising a bushing adapted to be fit into the bore in the wall, and a tuning element slidably mounted and received in the bushing. 
     Another embodiment relates to a radio frequency (RF) component, comprising one or more walls defining a cavity, with at least one wall having at least one bore therethrough, a bushing mounted in a bore in the wall, and a tuning element slidably mounted and received in the bushing so that the tuning element projects inwardly through the bushing and into the cavity. 
     Yet another embodiment relates to a method of tuning an RF component, comprising steps of providing a bushing mounted in a bore in a wall of the RF component, sliding a tuning element that is slidably mounted and received in the bushing so that the tuning element projects inwardly through the bushing and into the cavity by a distance varying according to the sliding of the tuning element, monitoring a performance characteristic of the RF component, and releasing the tuning element when a desired performance characteristic is achieved. 
     It should be apparent that, in this manner, various exemplary embodiments enable convenient tuning adjustment. In a particular example, by sliding a tuning element held by a bushing, the cavity can be tuned in a simple and cost-effective manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to better understand various exemplary embodiments, reference is made to the accompanying drawings, wherein: 
         FIG. 1  illustrates a view of a tuning element assembly according to a first embodiment. 
         FIG. 2  is a perspective view of the assembly of  FIG. 1 . 
         FIG. 3  is another perspective view of the assembly of  FIG. 1   
         FIG. 4  is a cutaway side view showing the assembly of  FIG. 1  installed in the wall of a RF component. 
         FIG. 5  is a view similar to  FIG. 1  showing an alternative embodiment of a tuning assembly. 
         FIG. 6  is a perspective view of the alternative embodiment of  FIG. 5 . 
         FIG. 7  is another perspective view of the alternative embodiment of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, in which like numerals refer to like components or steps, there are disclosed broad aspects of various exemplary embodiments. 
       FIGS. 1 through 3  illustrate an embodiment of a tuning assembly  1 . The tuning assembly  1  has a movable tuning element  10  that is adapted for installation to project through a bore hole  12  in a wall  14  of a RF component defining a cavity  16 . In the example shown in  FIG. 4 , the RF component  14  is a filter having one or more tuning assemblies  1  and one or more resonators  18  disposed in the cavity. The wall  14  in the example if  FIG. 4  is a top plate of a housing  19 , with the top plate being removable from the remainder of the housing  19 , and the cavity  16  being an space enclosed by the top plate and the housing  19 . However, the RF component can be any RF component having a cavity. 
     Turning now to  FIGS. 1-3 , the tuning assembly  10  includes a movable element  10  having a main shaft  20 . The shaft  20  is an elongated member, having a least a middle portion  22  of the shaft  20  being cylindrical. In the illustrated example, the shaft  20  is in the shape of a circular cylinder along its length. However, the shaft  20  may also take the form of a square, or hexagonal cylinder, or any other elongated shape. Moreover, the shaft  20  does not need to be cylindrical or constant diameter along its entire length. 
     The shaft  20  is disposed to project through and be supported by a bushing  24 . The bushing  24  has at least at a middle portion  26  thereof an internal busing diameter  28  which is complimentary to an external shaft diameter  30  of at least the middle portion  22  of the shaft  20 . These diameters provide an axial sliding relationship between the shaft  20  and the bushing  24 . A lubricating material may be provided at this location if desired. 
     The bushing  24  also has a portion, in this case the middle portion  22 , having an external middle portion outer diameter  32  that is configured to be received within the bore hole  12  projecting through the wall  14  of the RF component. In the example shown in  FIGS. 1 through 3 , the middle portion  26  of the bushing  24  has a knurled, grooved or roughened surface. Depending on the overall geometry of the bushing  24 , this can provide some frictional press fit retaining force between the bushing  20  and the bore hole  12  when the bushing is installed in the bore hole  12 . 
     An example of the bushing  24  will now be described in more detail. The bushing  24  has at its first end a mounting flange  36 . The mounting flange  36  projects radially outward from the end of the middle portion  22 . The mounting flange  36  provides a stop surface abutting the adjacent surface of the wall  12 . In some embodiments, the mounting flange  36  may be soldered or affixed by adhesive to the wall  12 , thus affixing the bushing  24  to the wall  14 . Alternatively, the middle portion  26  may be press fit into the bore  11  of the wall  14  and the flange  36  serves mainly as a stop. 
     The middle portion  26  of the bushing  24  extends axially through a length generally equal to or greater than the thickness of the wall  12  at the mounting location. Also although described as a middle portion, the middle portion  26  in some embodiments may extend along any part of, or entirely along, the entire axial length of the bushing  24 . In the example shown in the drawings herein, the bushing  24  has, at its second end opposite to the flange end, a skirt portion  40  which will be described in more detail below. 
     In the illustrated embodiment, the skirt portion  40  generally is tapered so that it flares outwardly towards the bushing  24  second end, but also has three inwardly bent regions  42 . The inwardly bent regions  42  are particularly visible in  FIG. 3 , which has crease or bend lines to illustrate the inward bends. The inwardly bent regions  42  are each are angled radially inward such that the inward most points of the inwardly bent regions  42  form a triangle shape so that the inward most points have an interference fit with the shaft  20  and frictionally contact the outer surface of the shaft  20 . 
     In this illustrated embodiment, a frictionally retained shaft  20  is thus disposed for sliding movement within the bushing  24 , with some frictional resistance to the sliding movement being provided. The frictional resistance is provided to some degree at one or both of two locations. First, frictional resistance can be provided by contact of the inner diameter  28  of the middle portion  26  of the bushing  24  with the outer diameter  30  of the middle portion  22  of the shaft  20 . Second, frictional resistance can be provided by the contact of the three inwardly bent regions  42  at the lower end of the skirt portion  40  of the bushing  24 . The largest outer diameter of the skirt portion  40  is in this example the terminal end  44  of the skirt portion  40 , which is of an outer diameter that is smaller than the inner diameter of the bore hole  12  in the wall  14  to permit the bushing  24  to be inserted into the bore hole  12 . 
     The frictional resistance can be selected according to the application, but generally will be such that the tuning element can be moved either manually by a person or mechanically by an external tuning machine when desired. However, the frictional force is great enough that when no manual or machine manipulation is present, the shaft  20  will tend to stay in place with no axial movement during normal use of the RF component. For example, the force may selected to be great enough such that normal vibration such as occurs during use of the RF component will be sufficiently resisted by the frictional force. 
     Although the skirt portion  40  is illustrated as having three inwardly bent regions  42  for the convenience of manufacturing, the skirt portion  40  may feature more or less bent regions and/or other friction-providing designs. For example, the skirt  40  may be deformed to have simply one radially inwardly bent region, two inwardly bent regions, or a number greater than three. Also the reference to bent regions refers to the illustrated shape, but encompasses other shapes. The bent region shape may be manufactured by any forming process, adapted for the material used, such as for example by crushing an originally conical or cylindrical skirt region or by bending with a forming tool. If the bushing  24  is molded from a plastic material, the bent shape may be molded in the original molding process or the plastic material may be bent or crushed after molding. Further, instead of, or in addition to, one or more inwardly bent regions, one or more fingers or tabs can project inwardly from the skirt portion  40  to provide the interference with the shaft  20 . Besides a conical taper, the skirt portion  40  can have other shapes. Also, one or more additional friction elements, such as an O-ring, may be provided at the skirt portion  40 , in addition to or instead of the illustrated bent regions  42 . For example, an O-ring or other bushing ring having a smaller diameter than the shaft  20  may reside within an interior channel provided on the skirt portion  40 , or be clipped on to the end of the skirt portion  40  to provide a selected degree of interference and frictional resistance to axial movement of the shaft  20 . 
     In addition, in some embodiments where the frictional contact between the cylindrical region of the shaft  20  and the interior diameter  28  of the bushing  24  is great enough, the skirt portion  42  and/or its associated friction interference features may be omitted. 
     The tuning element illustrated in the drawings includes an optional handle or cap  50  provided at a first end of the shaft  20 . The handle or cap  50  maybe integral with the shaft  20  or may be a separate component that is affixed to the end of the shaft  20 , for example by a threaded connector, a pressed fit, solder, welding, adhesive, or other affixing methods. The cap  50  can have an outer diameter greater than the diameter of the shaft  20 . The cap  50  may be generally flat and disc shaped or may be spherical or hemispherical or another shape. In some cases the cap  50  may be designed to be easily gripped by a person&#39;s fingers, or by a manipulator component of a mechanical adjusting device. 
     Also, as shown in the alternative embodiment of  FIGS. 5 through 7 , the tuning element  10  may include a supplemental tuning body  52  as shown.  FIGS. 5 through 7  illustrate an alternative embodiment, having the supplemental tuning body  52  and a variation of the geometry of the skirt  40  and middle portion  26  of the bushing  24 . In the illustrated example, the supplemental tuning body  52  is an element affixed to the interior cavity end of the shaft  20 . The supplemental tuning body  52  may be affixed to the shaft  20  by for example by a threaded connector, a pressed fit, solder, welding, adhesive, or other affixing methods. The supplemental tuning body  52  can in some applications enhance the sensitivity or effectiveness of the tuning assembly  1  and enhance adjustment motions of the tuning element  10 , and can be applied to the embodiment of  FIGS. 1 through 3 .  FIGS. 5 through 7  also illustrate that the middle portion  26  the knurled or ribbed outside diameter feature of the bushing  24  can be omitted and it can have a smooth outer diameter. 
     The tuning assembly  1  may be manufactured from any of a wide variety of materials. In some examples, the movable tuning element  10  and the bushing  24  are manufactured wholly or partially from metal, or a metalized plastic. If a supplemental tuning body  52  is present, it too in some examples will be manufactured from a metal or metalized plastic. Also, while the bushing  24  in the illustrated examples is a separate component from the wall  14  of the RF component, the bushing  24  can be implemented as an integral aspect of the wall  14 . 
     One example of a method of installing and utilizing the illustrated tuning apparatus will now be described. 
     Initially, the bushing  24  is installed in the bore hole  12  of the cavity wall  14 . 
     After the bushing  24  is inserted such that the mounting flange  36  is abutting the outside of the wall  12 , it can be affixed if desired by soldering, gluing or other attachment methods. Next, the tuning element  10  is inserted through the bushing  24 . Generally, the insertion of the tuning element  10  will be done from outside the wall  14  that is defining the cavity  16 . However, in some instances the wall  14  may be in the form of a plate that is removable from the remainder of the housing  19  defining the cavity  16 . In such instances, both sides of the plate are accessible and therefore the tuning element  10  may be inserted from either direction. Also, in embodiments where the cap  50 , and/or a supplement tuning body  52  are provided, one of the other may be affixed to the shaft  20  after the shaft  20  has been installed through the bushing  24 . 
     Next, with the RF component now having the tuning assembly  1  installed in its operative configuration, the tuning element  10  may be manipulated manually, or via a machine, such that it is translated inwardly and outwardly relative to the cavity  16  to effect a tuning process. Manipulation can be done by grasping and moving the cap  50  if one is provided, or by moving the shaft  20  directly if no cap  50  is provided. In some examples, an operator or tuning machine may be performing tuning while RF energy is being supplied to the cavity  16  and the operator or tuning machines is electronically monitoring the performance of the RF component. When the desired performance is achieved, the tuning assembly  1  can be left in place and thus the RF component will function as desired. 
     Although the various exemplary embodiments have been described in detail with particular reference to certain exemplary aspects thereof, it should be understood that the invention is capable of other embodiments and its details are capable of modifications in various obvious respects. As is readily apparent to those skilled in the art, variations and modifications can be affected while remaining within the spirit and scope of the invention. Accordingly, the foregoing disclosure, description, and figures are for illustrative purposes only and do not in any way limit the invention, which is defined only by the claims.