Abstract:
An alignment frame for a passive radio frequency ferrite isolator or circulator aligns ferrite discs with the circuit and the housing in which these components are encased. The fragile leads of the circuit are supported by the alignment frame, thereby creating a more durable and robust package design for handling and customer product interfacing. No adhesive is used, thereby reducing manufacturing time and increasing reliability of the device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     N/A 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     BACKGROUND OF THE INVENTION 
     Ferrite isolators and circulators are passive devices that allow transmission of radio frequency energy in one direction, but prevent or isolate transmission in the opposite direction. Such devices are located, for example, at the output of components such as power amplifiers to protect them from damage from reverse power transmission such as from a loss of a downstream component. Thus, for example, reverse flow into the isolator may be safely dissipated as heat rather than flow back into the upstream component. 
     In assembly of a typical ferrite isolator or circulator, illustrated in FIGS. 1-4, two ferrite discs  10 ,  12  are aligned above and below a center conductor or circuit  14  within an enclosing housing  16 . In assembly, referring to FIG. 1, the ferrite discs and the circuit are secured with an adhesive  18  into a sandwich structure  20  and aligned in a mechanical fixturing device  22  that clamps the circuit/ferrite sandwiches together to minimize the gap between the circuit and the ferrite discs. The fixturing device, which can hold several sandwiches, is placed in an oven for curing. After curing, the circuit/ferrite sandwiches and any further necessary components (illustrated in FIG. 3) are placed in the housing  16  and aligned in an alignment fixture  24  (FIG.  4 ). The complete assembly is secured with a snap-on cover  26  that has a built in spring force. 
     The handling and manipulating of the required fixtures and the application of adhesive, however, is not an efficient method of manufacturing such a device. Also, the adhesive necessarily introduces a gap between the ferrite discs and the circuit that may negatively impact the electrical performance of the device throughout the effective useful temperature range. Further, because the leads of the circuit are typically made of thin, soft copper and protrude without protection from the housing, the leads are susceptible to damage. Additionally, once removed from the fixture, the circuit/ferrite assembly is held in the housing by friction and the spring force of the cover. Any excessive force on the circuit/ferrite assembly could overcome this retention force and shift the circuit/ferrite assembly. Mechanical stresses on the circuit and/or the ferrite discs may also overcome the sheer strength of the adhesive and thereby disable the device. 
     A support frame  28  for triangular ferrite discs  30  is known, illustrated in FIG.  5 . This frame, however, does not protect the fragile circuit leads from external forces. 
     SUMMARY OF THE INVENTION 
     In the present invention, an alignment frame is provided that aligns the ferrite discs with the circuit and the housing in which these components are encased. Direct or indirect external forces on the circuit and/or the ferrite discs are directed to the alignment frame. No adhesive is used, thereby reducing manufacturing time and increasing reliability of the device. Additionally, the fragile leads of the circuit may be integrated or directly supported by the alignment frame, thereby creating a more durable and robust package design for handling and customer product interfacing. 
     More particularly, the alignment frame comprises a non-conductive peripheral member having an exterior upstanding wall comprising wall portions separated by spaces disposed to receive the leads of the circuit. Bridging pieces join the wall portions and extend across the spaces to support associated ones of the leads of the circuit. Nonconductive leg members extend radially outwardly from each bridging piece to support the fragile circuit leads. In one embodiment, a conductive member is disposed proximate the tip of each leg member for electrical connection with an associated circuit lead. The conductive member may be a pin in a through-hole or a wrap-around tab member. Alternatively, the leads of the circuit may themselves be wrapped around the conductive legs. 
     The alignment frame may also include interior upstanding wall portions in spaced alignment with the exterior wall portions to provide flexibility to accommodate ferrite discs having larger dimensional tolerances. The interior wall portions may be split at a midpoint to provide further flexibility. The bridging pieces may include projections to space the circuit away from the alignment frame. The wall portions may also include projections disposed to contact and retain notched edges of associated ones of the leads of the circuit. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is an isometric view of steps in manufacturing a prior art ferrite circulator; 
     FIG. 2 is an isometric view of a prior art ferrite circulator; 
     FIG. 3 is an exploded isometric view of a prior art ferrite circulator; 
     FIG. 4 is an isometric view of further steps in manufacturing a prior art ferrite circulator; 
     FIG. 5 is an exploded view of a prior art triangular ferrite disc and support frame; 
     FIG. 6 is an exploded isometric view of a ferrite circulator according to the present invention; 
     FIG. 7 is a plan view of an alignment frame according to the invention; 
     FIG. 8 is a cross-sectional view along line  8 — 8  of the alignment frame of FIG. 7; 
     FIG. 9 is an enlarged cross-sectional view of the circled portion of FIG. 8; 
     FIG. 10 is a plan view of a still further embodiment of an alignment frame of the present invention; 
     FIG. 11 is a cross sectional view along line  11 — 11  of the alignment frame of FIG. 10; 
     FIG. 12 is an enlarged cross-sectional view of the circled portion of FIG. 11; 
     FIG. 13 is an isometric view of a further embodiment of an alignment frame of the present invention; 
     FIG. 14 is an isometric view of a still further embodiment of an alignment frame of the present invention; 
     FIG. 15 is a plan view of a still further embodiment of an alignment frame of the present invention; and 
     FIG. 16 is a plan view of the alignment frame of FIG. 15 in partial assembly with a circuit, ferrite disc, and base housing; and 
     FIG. 17 is an exploded isometric view of multiple alignment frames used in a multiple junction application. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A circulator  30  incorporating an alignment frame  32  according to the present invention is illustrated in FIG.  6 . The circulator incorporates a center conductor or circuit  34  having three leads or ports  36 . An upper ferrite disc  38  is disposed above the circuit and a lower ferrite disc  40  is disposed below the circuit. The ferrite discs and the circuit are freely contacting, with no adhesive therebetween. Other typical components of the circulator, such as a pole piece  42 , ground plane  44 , pole piece disc  46 , magnet  48 , and cover return  50  are also included in the assembly. The components are assembled and encased in a housing assembly. The housing assembly is typically formed in two pieces: a base housing  52  and a cover  54 . The base housing includes upstanding walls  56  that define an interior region  58  in which the ferrite discs, the circuit, and the other components are located. The walls include cut away sections  59  through which the leads  36  of the circuit protrude. 
     A preferred embodiment of an alignment frame according to the invention is illustrated more particularly in FIGS. 7-9. The alignment frame comprises a nonconductive peripheral member  70  configured to fit within the interior region  58  of the base housing  52 . In the embodiment illustrated, the peripheral member  70  is circular or ring-shaped, although the peripheral member may be provided in other shapes, such as square, rectangular or triangular, if desired, to accommodate the shape of the particular device. The peripheral member includes an exterior upstanding wall  72  divided into three exterior upstanding wall portions  74  separated by spaces  76  through which the leads  36  of the circuit  34  pass. The spaces are aligned with the cutaway sections  59  of the base housing  52  when the alignment frame is placed in the base housing. The upstanding wall portions  74  are preferably sized and configured to provide a slip fit with the interior of the walls  56  of the base housing. A tighter friction fit may be provided if desired. The wall portions  74  are also preferably sized and configured to provide a mechanical friction or interference fit with the ferrite discs. In this way, the discs and circuit are retained by the alignment frame in the housing with no adhesive. 
     The peripheral member  70  of the alignment frame  65  also includes bridging pieces  78  between each exterior upstanding wall portion  74  for supporting the circuit leads. Legs  80  extend radially outwardly from the bridging pieces  78  of the alignment frame. Each leg includes a conductive member  82  formed at or near the tip. The legs underlie and support the fragile circuit leads, and the conductive members provide a good electrical connection between a component below the legs (not shown) and the circuit leads. In this manner, the legs support the leads such that direct and indirect forces on the leads are transmitted to the alignment frame, which is retained in the housing. The alignment frame  65  is preferably configured to support the circuit sufficiently to withstand a pull test of 5 N on each leg. This test is typically performed during manufacturing. 
     The conductive members may be in any suitable form. For example, in FIGS. 7-9, the conductive members are in the form of pins  82  that extend through openings in the legs  80 . In another embodiment of the alignment frame illustrated in FIGS. 10-12, the conductive members are in the form of tabs  84  that wrap around the tips of the legs  80 . The conductive members may be formed in any suitable manner, such as by insert molding or over molding with the frame. Alternatively, the conductive members may be formed as snap fit pieces that are attached to the alignment frame after the frame has been manufactured. In a further alternative, illustrated in FIG. 13, the conductive members may be omitted from the legs, and the circuit leads may themselves be wrapped around the tips of the legs. In these embodiments, like reference numerals have been used to designate like elements. 
     A further embodiment of an alignment frame suitable for use with ferrite discs manufactured with larger tolerances is illustrated with more particularity in FIG.  14 . The alignment frame includes three interior upstanding wall sections  90  in curved alignment with the three exterior upstanding wall portions  74 . Each of the interior wall sections includes a split or space  92 , generally at the midpoint of each section  90 , that divides the section into two halves. The opposite ends of each interior wall section  90  are joined to opposed wall members  94  attached to the ends of each exterior wall portion  74 . The split wall sections  90  are disposed such that the ferrite discs  38 ,  40  fit within the alignment frame with a mechanical friction or interference fit and are aligned by the frame. The sections are sufficiently flexible to allow them to accommodate ferrite discs having larger dimensional tolerances. The diameter of the ferrite discs may vary by 0.002 to 0.004 inch depending on the manufacturing process. Allowing the ferrite discs to be manufactured with larger tolerances reduces manufacturing costs. Although omitted from the embodiment illustrated in FIG. 14, the legs  80  that support the circuit leads may be provided if the additional support they provide for the circuit leads is desired, as illustrated, for example, in FIG.  13 . 
     In another embodiment of an alignment frame  132 , illustrated in FIGS. 15 and 16, the interior upstanding wall sections  90  are continuous between the opposed wall members  94 , not split. The interior wall sections are also in curved alignment with the three exterior wall portions  74 . The continuous interior wall sections provide some flexibility, although not as much as the split wall sections. However, depending on the tolerances with which the ferrite discs are manufactured, this amount of flexibility may be sufficient. 
     Referring to FIGS. 14-16, the end walls  94  of the upstanding wall portions  74  preferably include opposed projections  96  that extend circumferentially inwardly toward the spaces  76  to contact corresponding notches  98  in the leads  36 . The projections may take any suitable configuration, such as the rounded ribs shown. The bridging pieces  78  may also include upstanding projections  100 , preferably point projections, in the center, illustrated in FIGS. 15-16. These projections space the circuit  34  away from the material of the alignment frame, thereby increasing the air space around the circuit, to minimize any effect from dielectric differences between the circuit and the frame. It will be appreciated that the projections  96  and/or the projections  100  may be provided with other embodiments, such as those of FIGS. 7-12, if desired. 
     FIG. 17 illustrates an example of multiple alignment frames  32  of the present invention used in a multiple junction application. In this application, two or more circuits  36  are joined at attached link  37 . Any number of junctions can be provided, depending on the application. 
     The peripheral member  70  of the alignment frame may be made from any suitable nonconductive material. Preferably a material that can withstand solder reflow temperatures (typically greater than 230° C.) is used, because the device is typically passed through a solder reflow oven during manufacture. Liquid crystal polymers or high temperature plastics, which may be strengthened with glass reinforcing fibers or particles, are suitable. If the alignment frame is not intended for exposure to high temperature environments, other materials, such as polyesters, polypropylenes, or paper/epoxy materials, may be used. The alignment frame may be made by any suitable process. For example, an injection molding process that provides a one-piece assembly is suitable. Alternatively, a machining process may be more suitable depending on the choice of materials. The alignment frame preferably has a neutral rotational orientation. 
     The invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.