Abstract:
An assembly and method relates to stabilizing a radio frequency (RF) filter with respect to a housing. The assembly can include a filter component; a housing having a groove to receive the filter component; a cover mounted to the housing to cover the groove; and an elastomeric element disposed between the cover and the filter. The elastomeric element may be one or more tubular pieces.

Description:
TECHNICAL FIELD 
       [0001]    The invention pertains to transmission of radio frequency signals and to filters used in transmission of radio frequency signals. 
       BACKGROUND 
       [0002]    In-line filters are well known for use in radio frequency transmission lines. Examples of radio frequency filters include low pass filters. Further examples of low pass filters include generally cylindrical conductive structures, which may have changing outer diameters, and which may be surrounded by a dielectric material. Such filters have been known to be supported by a housing block having a channel into which the filter is placed, with a flat cover mounted over the top of the channel and the filter. 
       SUMMARY 
       [0003]    A brief summary of various exemplary embodiments is presented in this section. 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 a 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. 
         [0004]    Various exemplary embodiments relate to a radio frequency (RF) filter assembly, comprising: a filter component; a housing having a groove to receive the filter component; a cover mounted to the housing to cover the groove; and an elastomeric element disposed between the cover and the filter. 
         [0005]    The elastomeric member can include two elastomeric members each in the shape of a rod, and may be made of silicone. The groove can define a semi-circular u-shaped surface and two side wall surfaces, each being on one side of the u-shaped surface. The tubular elastomeric member can be in contact with an outer surface of the filter, an inner surface of the channel, and an inner surface of the plate. The elastomeric member may have two parallel rod portions, connected to each other by a plurality of cross bar portions. The assembly may also have an extension block disposed in between the elastomeric member and the filter, having a lower surface having a concave curved portion. 
         [0006]    Other exemplary embodiments relate to a method of stabilizing a radio frequency (RF) filter assembly, comprising: providing a filter component, a housing having a groove to receive the filter component, and a cover mounted to the housing to cover the groove; and compressing an elastomeric element disposed between the cover and the filter. 
         [0007]    Other exemplary embodiments relate to a radio frequency (RF) filter assembly, comprising: a filter component; a housing having a groove to receive the filter component; a cover mounted to the housing to cover the groove; and stabilizing means, such as an elastomeric member, disposed between the cover and the filter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    In order to better understand various exemplary embodiments, reference is made to the accompanying drawings, wherein: 
           [0009]      FIG. 1  is an exploded perspective view of a filter and housing assembly. 
           [0010]      FIG. 2  is a partially assembled perspective view of the arrangement of  FIG. 1  with a cover removed. 
           [0011]      FIG. 3  is a view corresponding to  FIG. 2  with a cover in place. 
           [0012]      FIG. 4  is a cross-sectional perspective view of the arrangement of  FIG. 1 . 
           [0013]      FIG. 5  is a cross-sectional side view of the arrangement of  FIG. 1 . 
           [0014]      FIG. 6  is an end view of the arrangement of  FIG. 1 . 
           [0015]      FIG. 7  is a partially assembled perspective view similar to  FIG. 2 , showing an alternative embodiment. 
           [0016]      FIG. 8  is an end view similar to  FIG. 6 , showing another alternative embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Various embodiments will now be described with reference to the drawing figures, including reference numerals relating to the various parts. 
         [0018]      FIG. 1  is an exploded view depicting a first embodiment 1. A radio frequency (RF) filter  10  is provided. In this example, the RF filter  10  is a low pass filter having a first transmission line connector  12  at one end and a second transmission line connector  14  at the other end. As will be explained in further detail below, (with reference to  FIGS. 4 and 5 ), the filter  10  is a low pass filter that has a main filter component  16  that has changing outer diameters. In this example, the main filter component  16  includes large diameter portions  18 , which may be of varying lengths, and small diameter portions  20 , which also may be of varying lengths as desired according to the low pass filter design. The filter  10  may be made of any suitable transmissive material, such as by way of example, brass or copper. Although a low pass filter is illustrated, various embodiments can be used with other types of filters or similarly shaped RF components. 
         [0019]    The main filter component  16  is surrounded by a dielectric material  22 . In the illustrated example, the dielectric material may be any suitable material such as, for example, a melt-porcessible flouropolymer such as a heat shrink applied FEP (fluorinated ethylene propylene) material, in some cases with the dielectric outer material having been applied around the main filter component  16  using a heat gun. Alternatively, other dielectric surrounding materials may be used, and may be implemented or applied in different methods. 
         [0020]    Returning to  FIG. 1 , the filter  10  may be supported by a main housing  24 . The housing  24  can be constructed of any suitably rigid material, and in the illustrated example may be made of a metal such as aluminum, which may be unplated or may be plated with either copper or silver. 
         [0021]    The housing  24  has sides  26  and a bottom surface  28 , but may be any external shape and can be surrounded by and be a part of a cavity filter. The housing  24  also has two flat top mounting surfaces  30  which will be described in more detail below. The housing  24  further includes a channel  32  (also referred to herein as a groove) which is configured to receive and support the filter  10 . In the illustrated example, the channel  32  has a lower surface  33  which is a semi-circle when viewed as an end view, and has two flat side surfaces  34 . The radius of the semi-circular lower surface  33  may be selected to be dimensionally close to the largest outer radius of the filter  10 . This can provide an advantage in some examples by which the largest outer surface of the filter  10  rests with the desired closeness to the housing  24 , around approximately 180° of the 360° circumference of the filter  10 . In other embodiments, the lower portion of the channel  32  may be square, in which case only three substantially tangential contact points with the filter  10  are provided between the filter  10  and the housing  24 . 
         [0022]    The assembly of  FIG. 1  also includes a cover  36  which may be mounted to the top surfaces  30  of the housing  24  by any suitable attachment arrangement such as, for example, the provision of a plurality of screw-type fasteners  38 . Screw-type fasteners  38  in an example may pass through mounting holes  40  in the cover  36  and into mounting holes  42  in the housing  24 . The cover  36  may be made of any suitable material, for example, aluminum. The fasteners  38  may be any suitable fasteners, such as, for example, stainless steel screws. 
         [0023]      FIG. 1  also illustrates that the filter arrangement includes two elastomeric elements  44 . The elastomeric elements  44  in this example are in the form of elongated elastomeric rods, and are shown in an incompressed state in  FIGS. 1 and 2 .  FIGS. 3-6  show the elastomeric elements  44  in a compressed condition. The elastomeric elements  44  may be made of any suitable material, and in one example may be made of silicone. In selecting the material for the elastomeric elements  44 , various considerations may be employed, such as, for example, the mechanical properties of the material, the temperature range characteristics of the material, and the electric loss and/or dielectric properties of the material. The embodiment of  FIGS. 1-6  uses two parallel elastomeric elements  44 , each formed as elongated tubes, but other cross-sectional shapes or number of elements may be used, including a single elastomeric element  44 . 
         [0024]    As will be described in further detail below, the elastomeric elements  44  in some embodiments may provide a benefit of being compressed between the cover  36  and the filter  10  in such a way as to resiliently position the filter  10  against the lower surface  32  of the channel. Although two parallel elastomeric elements  44  are shown, with each elastomeric element spanning essentially the entire length of the housing  24 , a single elastomeric element  44 , or a larger number of elastomeric elements, may be employed and may run for a shorter portion of the housing. 
         [0025]    In  FIG. 2 , the elastomeric elements  44  have been laid into position above the filter  10 .  FIG. 3  depicts the configuration after the cover  36  has been installed and tightened and the fasteners  38  have been tightened.  FIGS. 4-6  show further details of the installed configuration. In particular,  FIG. 6  depicts that the elastomeric elements  44  have been deformed by installation of the cover  36 . Arrows A, B and C show reaction forces on the elastomeric elements. In this case, the reaction forces are applied at an area A by the cover  36 , at an area B by the side  34  of the channel, and at an area C by the filter  10 . The filter  10  transfers this load to a reaction force D applied onto the housing  26  generally along the entire lower region  33  of the channel  32 . These reaction forces can in some instances provide certain benefits. For example, the forces will tend to create a desirable quality of contact between the filter  10  and the housing  24 . Further, if the filter  10  and the housing  24  are subjected to different degrees of thermal expansion, the filter  10  and the housing  24  can move longitudinally and radially relative to each other while still maintaining a relatively close contact. This may be desirable because in some instances it may reduce or eliminate the need to weld or otherwise affix the filter  10  to the housing  24 ; or in some instances may facilitate the attachment of the filter  10  to the housing  24  at a single location, while permitting for longitudinal and radial expansion and yet restraining the filter  10  in the channel. 
         [0026]      FIG. 7  shows an alternative embodiment. In  FIG. 7  the components are similar to that of  FIG. 1  except that the elastomeric rods  44  are connected in a ladder type configuration by elastomeric cross bars  50  form of a single elastomeric component  52 . In this embodiment, the elastomeric component feature is provided by a single elastomeric component  32  having a ladder configuration that includes as a unitary structure parallel rods  44  and cross bars  50 . The provision of a relatively wide single piece elastomeric element  52  in some instances may provide for greater ease of installation and/or manufacture.  FIG. 7  shows the cover  36  removed for clarity, but illustrates the elastomeric element  52  in a compressed state. 
         [0027]      FIG. 8  shows another alternative embodiment. In the embodiment of  FIG. 8 , a dielectric extension block  54  is provided. The dielectric extension block  54  includes a lower curved surface  56  that compresses against the filter  10 . In the illustrated embodiment, the lower surface  56  has a concave circular curved profile portion to extend around approximately 120° of the top surface of the circumference of the filter  10 . Alternatively, the extension block  54  may have a flat lower surface that contacts the filter  10  at a tangential point, or have a concave curved surface portion that may extend around greater than 120° of the top surface of the filter  10 . The extension block  54  also has a top groove  58  which is sized generally to receive one or more elastomeric elements  60 . The elastomeric element  60  in this example is shown in  FIG. 8  in a compressed configuration having reaction force E pressing on the cover  36  and reaction forces F, G and H pressing on the extension block  54 . The extension block  54  thus provides these reaction forces as forces K and L onto the filter  10  thus seating the filter  10  against the lower channel portion  33  via reaction force M, the reaction force M being similar to reaction force E in  FIG. 6 . A benefit of the embodiment of  FIG. 8  may be that only a single elastomeric component  60  is needed. Further, in the case of the housing  24  having relatively deep vertical side walls  34 , the extension block  54  can occupy this vertical space without the need for a large piece of elastomeric material. In an example, the material at the elastomeric component  60  in  FIG. 8  may be silicone, and the extension block  54  may be made of polypropylene. The elastomeric component  60  in this example has a circular cylindrical shape when uncompressed, but other cross-sectional shapes may be used, as with the other embodiments. 
         [0028]    The reaction forces described above are by way of examples in some embodiments only. The materials and geometries are also examples and can be selected to provide a desirable degree of compression force. In some instances, it may be desirable to select the compression force so that it is low enough so that the cover  36  is not unduly deflected upwards away from the housing  24 . In some instances, it may be desirable to avoid undue upward deflection of the cover  36  so that the lower surface of the cover  36  remains flush or flat against the upper surface  30  of the housing  24 , thus providing a desired degree of electrical contact between the cover  36  and the housing  24 . 
         [0029]    Due to the compressive forces, the filter  10  is stabilized with respect to the housing  24 , and in some cases will thus tend to remain in place to a desired degree when subjected to vibrations or thermal dimensional changes of the filter  10  and/or housing  24  with respect to each other. 
         [0030]    In the illustrated embodiments, the elastomeric members  44  have a cylindrical tube shape with a circular outer profile. However, the outer profile of the elastomeric members may be any other shape including, for example, triangular, square, hexagonal or other shapes which may have uneven outer surfaces. 
         [0031]    In the illustrated embodiments, the elastomeric members  44  are shown as being a separate component from the filter. However, in some other embodiments the elastomeric components may be permanently or semi-permanently attached to the outside of the filter, for example, by being adhesively attached on pre-manufactured onto the filter. For example, elastomeric components may be pre-molded onto an outer surface of the filter along with or after the application of the dielectric layer. 
         [0032]    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.