Abstract:
Increasing performance of planar inductors used in broadband applications is described. In one implementation, an apparatus includes a high Quality factor (Q) value spiral planar inductor etched directly into a printed circuit board. A ferrite structure is attached to the printed circuit board and located in proximity to the high Q value spiral planar inductor. The ferrite structure increases the Q of spiral planar inductors, but without the inconvenience and expense of a wire wound terroidal inductors. Various shaped ferrite structures may be used in conjuction with the spiral planar inductors. Additionally, in certain implementations, the ferrite structures are configured to rotate about axis permitting the inductors to be tuned, even after components have been installed on a printed circuit board.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present patent application is a continuation-in-part of U.S. patent application Ser. No. 10/403343, (Attorney Docket No. 17833) entitled “Inductor Topologies and Decoupling Structures for Filters Used in Broadband Applications, and Design Methodology Thereof,” by Keeney, et al. having a filing date of Mar. 28, 2003, and is commonly assigned herewith. The contents of the aforementioned application are fully incorporated herein by reference. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to filters and other components used in broadband applications.  
         BACKGROUND  
         [0003]    “Broadband” generally refers to methodologies used to send and receive data over high-speed networks. Broadband, as opposed to narrowband, usually implies a bandwidth capability where there is voice quality movement of data. Broadband is commonly associated with, although not limited to, a way of connecting a local computer or other device to a high-speed network, such as the Internet.  
           [0004]    Broadband connections, whether through cable, digital subscriber lines, optical, wireless, or satellites, typically involve the use of some type of interface module, such as a modem, for handling bi-directional transmissions of data. Many interface modules use various types of filters to remove information content such as high and/or low frequencies, for example. These filters usually include one or more high quality factor (Q) torroidal inductors. “Q” represents the efficiency of an inductor in terms of storing a magnetic field.  
           [0005]    Torroidal inductors having high Q values are discreet parts typically fabricated by manually wrapping wires around ferromagnetic cores. Most automatic “pick-and-place” techniques are not available for torroidal inductors due to their fragile nature and the precision needed to wind and place wiring around ferromagnetic cores. Accordingly, the fabrication process is labor intensive and can lead to high manufacturing costs. There are also problems associated with correctly installing them on a printed circuit board, because automatic pick-and-place is not typically available. All these problems can lead to higher manufacturing costs.  
           [0006]    Once inductors have been installed on a printed circuit board, it is very difficult, if not impossible, to effectively tune operating characteristics associated with the inductor, such as flux, Q values, and reactance. Thus, tuning of torroidal inductors is extremely limited after they are installed on a printed circuit board.  
         SUMMARY  
         [0007]    Increasing performance of planar inductors used in broadband applications is described. In one implementation, an apparatus includes a high Quality factor (Q) value spiral planar inductor etched directly into a printed circuit board. A ferrite structure is attached to the printed circuit board and located in proximity to the high Q value spiral planar inductor.  
           [0008]    The ferrite structure increases the Q of spiral planar inductors, but without the inconvenience and expense of wire wound torroidal inductors. Various shaped ferrite structures may be used in conjunction with the spiral planar inductors. Additionally, in certain implementations, the ferrite structures are configured to rotate about an axis permitting the inductors to be tuned, even after the inductors have been installed (i.e. embedded) on a printed circuit board. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears.  
         [0010]    [0010]FIG. 1A shows an apparatus used in broadband applications.  
         [0011]    [0011]FIG. 1B shows two generally circular high Q value planar spiral inductors decoupled from one another by a decoupling structure.  
         [0012]    [0012]FIG. 2 is a method for making at least one high Q value spiral planar inductor and a decoupling structure such as the exemplary ones shown in FIG. 1.  
         [0013]    [0013]FIG. 3 shows an exemplary apparatus configured to operate as an interface module in a broadband environment.  
         [0014]    [0014]FIG. 4 shows an exemplary method for optimizing a design for making a filter used in a broadband application.  
         [0015]    [0015]FIG. 5 is top view of a generally circular high Q value spiral planar inductor etched into a printed circuit board, showing a hole inserted in the center of the inductor to receive a ferrite structure.  
         [0016]    [0016]FIG. 6 is a cross-sectional view of the printed circuit board shown in FIG. 5 and a ferrite structure attached thereto.  
         [0017]    [0017]FIG. 7 shows four top views of a pedestal structure as it is rotated over a generally circular high Q value spiral planar inductor (to affect tuning).  
         [0018]    [0018]FIG. 8 is a cross sectional view of a printed circuit board with a ferrite structure in the shape of a bobbin attached thereto.  
         [0019]    [0019]FIG. 9 is a cross sectional view of a printed circuit board and ferrite structure attached thereto, the ferrite structure configured to fully capture flux within a spiral planar inductor. 
     
    
     DETAILED DESCRIPTION  
       [0020]    Architecture  
         [0021]    [0021]FIG. 1A shows an apparatus  100  used in broadband applications. Apparatus  100  may be a broadband interface module used to connect two devices together in a broadband environment, such as subscriber device shown to the Internet. For example, apparatus  100  may be a set-top box, a cable television module, an optical modem, a DSL-based modem, and other related devices that operate in a broadband environment.  
         [0022]    Apparatus  100  typically includes one or more printed circuit boards containing various circuits. In the exemplary illustration, apparatus  100  includes a printed circuit board  102  being an FR 4  substrate circuit board. However, printed circuit board  102  may be another type of board used to connect circuits and chips. Printed circuit board  102  may be single sided, double sided, multi-level (layer), and capable of receiving other printed circuit boards. Additionally, the conductors used within the printed circuit board may contain copper, or other conductive materials.  
         [0023]    Typically, contained on printed circuit board  102  is one or more filters  104  used to perform some type of input/output filtering operation involving some type of broadband application. For instance, filter  104  may be a diplexer, a duplexer, a tri-plexer, a high pass filter, a low pass filter and so forth. For example, filter  104  may operate in a range from about 1-to-1000 MHz, however, other ranges, greater or smaller, are possible.  
         [0024]    Typically, contained within each filter  104  is one or more generally circular high Q value spiral planar inductors that are etched directly into the printed circuit board  102 , configured to operate in a broadband environment. In the exemplary illustration, filter  104  includes two generally circular high Q value spiral planar inductors  106 ( 1 ) and  106 ( 2 ), referred to generally as inductors  106 . As used herein, “generally circular” means a shape that is generally round such as a circle, rounded rectangles, racetrack shaped circles (e.g., an ellipse or oval), volute and other generally circular forms. Generally circular also includes objects that are planar, but deposed within the printed circuit board at different levels such as a helical spiral. Both inductors  106  used in this example are elliptical in shape.  
         [0025]    Each inductor  106  includes generally circular conductive traces, generally referred to as reference number  108 , that are etched directly into the printed circuit board  102 . The conductive traces  108  are conductive tracks etched into a conductive layer of the printed circuit board  102 . An outer most conductive trace (referred to generally as  110 ) for each inductor, wraps around inner conductive traces (referred to generally as  112 ) that form a spiral leading to an inner most conductive trace (referred to generally as  113 ). The inner most conductive trace  113  wraps around a center portion (referred to generally as  116 ) of the inductor, the center portion  116  having no conductive traces.  
         [0026]    Each track (e.g. trace  108 ) may be monolithically deposited within the printed circuit board through a wide range of printed circuit board processing techniques. In the exemplary illustration, traces  108  are photo-etched into the printed circuit board  102 , because photo-etching provides the capability to produce finer tracks and closer gaps. For example, it may be necessary to have gaps between the traces down to one 3000 th  of an inch, which generally involves some sort of photo-etching or equivalent process. Additionally, through photo-etching, it is possible to consistently and repetitively manufacture traces within strict dimensional tolerances.  
         [0027]    In the exemplary illustration, inductors  106 ( 1 ) and  106 ( 2 ) are coupled together via a trace  118 . Depending on the application, each inductor  106  may be connected to other components, such as capacitors (not shown in FIG. 1A), which may be discrete or parasitic. In such applications, each inductor may be configured to provide a self-resonant frequency for inductances of about 40 to 400 nH; however, other ranges greater or smaller are possible. Each inductor may be connected to ground or a current source through vias  114 ( 1 )- 114 ( 4 ) connected to the traces (i.e., winding)  108 .  
         [0028]    Generally circular high Q value planar spiral inductors are open structures, and therefore generate magnetic and electrical fields, which tend to travel through air and cross through conductive traces of adjacent spirals, modifying their inductances. Modification of inductances in turn effects the resonators (see FIG. 3 for an example of a resonator). This phenomena, referred to as “coupling” may significantly and adversely affect the performance of filters. Being able to compensate for these coupling effects is desirable.  
         [0029]    Decoupling structures, such as a decoupling structure  120  shown in FIG. 1 can be used to reduce inter-filter and intra-filter coupling once the coupling effects are quantified. Decoupling structure  120  can be etched into the printed circuit board in proximity to the inductors  106  to reduce coupling. That is, decoupling structure  120  is configured to reduce unwanted electromagnetic coupling between the inductors  106  when current flows through them. The decoupling structure may embody any shape or size, but is generally minimized to reduce “real estate” needed on the printed circuit board  102 . For example, decoupling structure  120  may be a narrow trace of conductive metal that is grounded or ungrounded. By positioning decoupling structure  120  near inductors  106 , inductors  106  cause a current to flow in the decoupling structure  120 , thereby generating a magnetic field having a sense of polarization opposite that of the magnetic fields generated by the inductors  106 . Because, the magnetic field generated by the decoupling structure  120  opposes the magnetic field generated by the spiral inductors  106 , the effects of intra-filter or inter-filter coupling are reduced.  
         [0030]    [0030]FIG. 1B shows two generally circular high Q value planar spiral inductors  106 ( 3 ) and  106 ( 4 ) decoupled from one another by a decoupling structure  120 . FIG. 1B also shows another view of conductive traces  108  that are etched directly into a printed circuit board  102 . Referring to inductor  106 ( 3 ) of FIG. 1B are circular conductive traces  108  that are etched directly into the printed circuit board  102 . An outer most conductive trace  110  wraps around inner conductive traces  112  that form a spiral leading to an inner most conductive trace  113 . The inner most conductive trace  113  wraps around a center portion  116  of inductor  106 ( 3 ), the center portion  116  having no conductive traces.  
         [0031]    Referring back to FIG. 1A, it is possible that other elements and components may be included in apparatus  100 , including discrete parts. Different quantities of each of the components (greater or smaller) described above may also be included, such as using only a single generally circular high Q value spiral inductor or using more than two of the generally circular high Q value spiral inductors.  
         [0032]    [0032]FIG. 2 is a method  200  for making at least one high Q value spiral planar inductor and a decoupling structure such as the exemplary ones shown in FIGS. 1A and 1B. Method  200  includes blocks  202  and  204 . The order in which the method is described is not intended to be construed as a limitation.  
         [0033]    In block  202 , a generally circular high Q value spiral planar inductor is etched into a printed circuit board. For example, an inductor  106  (FIGS. 1A and 1B) is etched into a printed circuit board  102  (FIG. 1A and 1B) using printed circuit board techniques, such as photo-etching. To further reduce the amount of space required by the inductors and optimize layout space, the generally circular inductors may be elliptical in shape, such as shown in FIG. 1A (as opposed to purely circular inductors as shown in FIG. 1B).  
         [0034]    In block  204 , a decoupling structure may be embedded in the printed circuit board in proximity to the spiral inductor to reduce magnetic coupling. For example, decoupling structure  120  may be etched into printed circuit board  102  in proximity to two inductors  106 ( 1 ) and  106 ( 2 ) (or  106 ( 3 ) and  106 ( 4 )) to reduce coupling when current flows through the inductors  106 . Quantifying coupling shall be described in greater detail below.  
         [0035]    [0035]FIG. 3 shows an exemplary apparatus  300  configured to operate as an interface module in a broadband environment. In particular, apparatus  300  is configured as a diplexer and includes a filter  302 . Filter  302  includes generally circular high Q value spiral planar inductors  304 ( 1 )- 304 ( 7 ), embedded within a printed circuit board  303 . Inductors  304 ( 1 ),  304 ( 2 ), and  304 ( 3 ), along with capacitors C 8 -C 14  make-up a high pass filter portion of the diplexer, whereas inductors  304 ( 4 )- 304 ( 7 ) along with capacitors C 1 -C 7  make up a low pass filter portion of the diplexer. Resonator pairs are established between various inductors  304  and capacitor pairs in both the high pass and low pass filter sections. For instance, a least wound inductor  304 ( 5 ), and capacitor C 2 , form a resonator pair, and inductor  304 ( 6 ) and capacitor C 4  form a resonator pair, and so forth. A metal cover (not shown) may also be included as a part of apparatus  300 .  
         [0036]    Design Methodology  
         [0037]    To better identify coupling between spiral inductors, it is important to understand how a circuit that utilizes generally circular high Q value spiral planar inductors operates in a simulated environment prior to being etched into a printed circuit board. Unlike devices that use discrete inductors, it is difficult to tweak couplings between inductors once components have been placed onto a printed circuit board. That is why a spiral based filter design process may be used in connection with the introduction of any new filter design.  
         [0038]    In one implementation, a design synthesis and optimization process includes synthesizing a particular filter design (such as the diplexer shown in FIG. 3) or other device/module either by hand or automatically by using software-based design synthesis package, such as the EAGLEWARE GENESYS design synthesis package. One or more generally circular high Q value spiral planar inductors are designed per the synthesized values as separate inductors in an electromagnetic (EM) simulator. Optionally, Z or S-parameter data blocks, which are generated by the EM simulator or manual measurement, may then be substituted into a lumped element model for subsequent simulation by the EM simulator.  
         [0039]    Next, a suitable printed circuit board layout may be completed and imported into the EM simulator. This layout (i.e., the circuit layout) may then be EM simulated and the coupling (K) factors between the generally circular high Q value spiral planar inductors are extracted.  
         [0040]    Next, the K factors are loaded into a new lumped element model and all of the inductive and capacitive elements of the filter or device are optimized. Thus, the design process allows the coupling between the generally circular high Q value spiral planar inductors to be quantified and compensated for.  
         [0041]    Next, the circuit layout is modified according to the lumped element simulation results and a new EM simulation is performed. Decoupling structures, such as decoupling structure  120  shown in FIG. 1, can then be applied in the EM simulator to modify the K factors. Finally the design synthesis and optimization process is repeated until desired performance characteristics are achieved.  
         [0042]    [0042]FIG. 4 shows an exemplary method  400  for optimizing a design for making a filter used in a broadband application. Method  400  exemplifies one embodiment of the design synthesis and optimization process described above. Method  400  is used in conjunction with the design of a filter that includes at least one generally circular high Q value spiral planar inductor. Method  400  includes blocks  402 - 410 . The order in which the method is described is not intended to be construed as a limitation.  
         [0043]    In block  402 , a design layout for a filter (or other device) used in a broadband application is created. The filter includes one or more generally circular high Q value spiral planar inductors. For example, the filter may be a diplexer such as the one shown in FIG. 3. The design layout may be created manually or through the use of synthesis tools as described above.  
         [0044]    In block  404 , the layout is simulated to ascertain operational characteristics of the layout. For example, the layout may be EM tested and/or radio frequency tested. Optionally, Z-parameter or S-parameter data blocks may be substituted in the lumped element model that is either generated by the EM simulator or by manual measurements.  
         [0045]    In block  406 , once the circuit board layout is completed and imported into a simulator, coupling (K factors) between inductors are quantified.  
         [0046]    In block  408 , the couplings are compensated for by (i) introducing decoupling structures into the layout, (ii) changing inductor values for at least one of the generally circular high Q value spiral planar inductors, and/or (iii) modifying the layout.  
         [0047]    In block  410 , operations performed in blocks  404 - 408  are repeated until the layout operates within desired performance targets. For example, the K factors may be reloaded into a new lumped element model and all inductive and capacitive elements re-optimized. Then the circuit layout is modified according to the simulation results and then a new EM simulation is performed. This process may continue iteratively until desired simulated performance is achieved.  
         [0048]    Higher Q Value Spiral Inductors  
         [0049]    It is possible to introduce a ferrite structure in combination with any of the spiral planar inductors described above including any of the filters that may utilize a spiral planar inductor as described above. The ferrite structure is composed of a ferromagnetic material that serves to increase flux density and inductive reactance within a planar spiral inductor. Accordingly, the combination of increased flux and inductive reactance causes a substantial potential increase in Q associated with spiral planar inductors. In some instances, it has been observed that the Q value increases 50-to-60 percent. For example a planar spiral inductor without a ferrite structure may provide a Q of about 80 compared to a planar inductor with a ferrite structure that may provide a Q of about 125.  
         [0050]    Accordingly, it may be advantageous to introduce a ferrite structure in conjunction with any of the inductors or devices described above to increase performance of such inductors/devices. The ferrite structure can be fastened to a printed circuit board using a wide variety of techniques currently used to attach components to printed circuit boards. For instance, in certain implementations it may be desirous to mount (i.e., glue, solder, screw, bolt, etc.) a ferrite structure on the printed circuit in proximity to the spiral planar inductors described above. As used herein “proximity to a spiral planar inductor” means adjacent to a spiral planar inductor, partially over a spiral planar inductor, partially under a spiral planar inductor, fully over a spiral planar inductor, fully under a spiral planar inductor, and/or encasing a spiral planar inductor in all three dimensions (through the center). Described in more detail below are several sample illustrations of how to implement a ferrite structure in combination with a spiral planar inductor.  
         [0051]    [0051]FIG. 5 is top view of a generally circular high Q value spiral planar inductor  500  etched into a printed circuit board  502 . Positioned in proximity to the generally circular high Q value spiral inductor is a hole  504 ( 1 ) in the printed circuit board  502 . As shall be explained, hole  504 ( 1 ) provides a means to attach and secure a ferrite structure (shown in FIGS. 6-9 below) to the printed circuit board  502 . In the ferrite that passes through the center of the spiral this is where the highest flux concentration occurs (center).  
         [0052]    In one implementation, the hole  504 ( 1 ) is positioned within a center portion  506  of the generally circular high Q value spiral inductor  500 , where there are no conductive traces. That is, hole  504 ( 1 ) is positioned within a non-conductive portion of generally circular high Q value spiral inductor  500  and passes completely through printed circuit board  502 .  
         [0053]    Alternatively, a hole  504 ( 2 ) may be positioned exterior to the outer most traces  512  of generally circular high Q value spiral inductor. In either implementation, holes referred to generally as  504  do not necessarily have to pass completely through printed circuit board  502  and may only pass partially through a printed circuit board i.e., one or more layers of the printed circuit board. Holes generally referred to reference number  504  are generally circular in shape, but may be other circular and non-circular shapes including, but not limited to, ovals, squares, triangles, and so forth.  
         [0054]    [0054]FIG. 6 is a cross-sectional view of printed circuit board  502  shown in FIG. 5, with a ferrite structure  602  attached thereto. According to this exemplary implantation, ferrite structure  602  is attached to printed circuit board  502  via hole  504 ( 1 ) (see also FIG. 5). Ferrite structure  602  is composed of a ferromagnetic material formulated to be low loss over a particular range of RF frequencies. For instance, the ferromagnetic material may be composed of ferrite or powdered iron material. In the exemplary illustration, ferrite structure  602  includes a post  604  and pedestal structure  606 . Post  604  is configured to fit inside hole  504 ( 1 ) and pedestal structure  606  is configured to reside outside hole  504 ( 1 ).  
         [0055]    In one implementation, post  604  is a column with a diameter slightly smaller than the diameter of hole  504 ( 1 ). Post  604  provides stability for pedestal structure  606 , and, serves as an axis point to rotate (i.e., turn in a clockwise or counter clockwise direction) pedestal structure  606 , as shall be explained below (again the ferrite in the center gives the highest flux density and provides best performance short of the “cup” ferrite in FIG. 9. Once post  604  is inserted into hole  504 ( 1 ), post  604 , and hence ferrite structure  602 , may be secured to printed circuit board  502  by glue, solder or other fastening means.  
         [0056]    In one implementation, post  604  has a length that is slightly smaller than the total depth of hole  504 ( 1 ). For instance if the total thickness of printed circuit board is 0.06 inches and hole  504 ( 1 ) is equal to the thickness of the printed circuit board, then post  604  may be 0.055 inches, i.e., slightly shorter than the total depth of the hole. By being slightly shorter than or equal to the total depth of hole  504 ( 1 ), post  604  is prevented from extending beyond the bottom side  608  of printed circuit board  502 . This allows a surface mount type application (SMT) It should be noted that the aforementioned dimensions are illustrated for example purposes only as the actual sizes and shapes of various devices will change depending on the implementations. It should also be noted that “bottom” only refers to the position of the printed circuit board as illustrated in the Figures, and could easily be interchanged for the top of the printed circuit board.  
         [0057]    Alternatively, post  604  may be shaped differently than a column and have various diameters capable of fitting into hole  504 ( 1 ). Additionally, post  604  may also be longer than the total depth of hole  504 ( 1 ) and extend beyond the bottom side  608  of printed circuit board  602 . The post  604  may also include notches (not shown) to secure the post to the printed circuit board  502 . For plug-in type applications  
         [0058]    In one implementation, pedestal structure  606  and post  604  are integral, meaning they are a single unitary structure. Post  604  is generally perpendicular to pedestal structure  606 . Alternatively, pedestal structure  606  and post  604  may be individual pieces connected together by some type of fastening means such as by inserting the post  604  into an optional hole  612  within pedestal structure  606 .  
         [0059]    Pedestal structure  606  is generally larger (but not necessarily) than holes  504 ( 1 ) or  504 ( 2 ) and is configured to fit over (i.e., cover) at least a portion of the generally circular high Q value spiral planar inductor  500 . The portion may range from less than one percent to one hundred percent (100%) of the total area the generally circular Q value spiral planar inductor  500 .  
         [0060]    Post  604  and pedestal structure  606  may be offset with respect to the center  610  of pedestal structure  606 . This offset enables a greater variance in area of the planar spiral inductor covered by pedestal structure  606  when pedestal structure is rotated/twisted about an axis. For instance, FIG. 7 shows four top views  700 ( 1 ),  700 ( 2 ),  700 ( 3 ) and  700 ( 4 ) of a pedestal structure  702  as it is rotated over a generally circular high Q value spiral planar inductor  704 . In the four views, pedestal structure  702  is implemented as a disk shaped object in the shape of an ellipse to compliment the elliptically shaped inductor  704 , but may be implemented as other shaped objects including, but not limited to, a square, triangle and other various objects capable of rotating about an axis (e.g., post  604 ). Hole  504 ( 1 ) is shown as the axis point for which pedestal structure  702  is rotated.  
         [0061]    View  700 ( 1 ) shows pedestal structure  702  covering one hundred percent (100%) of inductor  704 , providing maximum coverage over inductor  704 . View  700 ( 2 ) shows the pedestal structure  702  rotated in a clockwise direction from view  700 ( 1 ) and covering less than the entire inductor  700 . View  700 ( 3 ) shows pedestal structure  702  rotated further and now covering approximately fifty percent (50%) of inductor  700  or the minimum amount of coverage that pedestal structure can cover according to this implementation. It should be noted that if the hole in the printed circuit board was outside the inductor or a different shaped pedestal structure  702  was used, it might be possible to cover less than fifty percent of the inductor. Finally, view  700 ( 4 ) shows pedestal structure  702  covering a percentage of inductor  704 , somewhere between maximum coverage (view  700 ( 1 )) and minimum coverage (view  700 ( 3 )).  
         [0062]    Thus, by rotating a pedestal structure about an axis (e.g., hole  504 ( 1 )) it is possible to tune a generally circular high Q value spiral planar inductor and change its Q and inductance values. This is particularly useful after components comprising a broadband filter are surface mounted on a printed circuit board. As explained with reference to the Background section above, tuning is difficult to nearly impossible once conventional components (torroidal inductors and capacitors) have been mounted on a printed circuit board. The aforementioned implementations, therefore, provide the ability to dynamically tune inductive characteristics, such as inductor reactance and Q, after the inductor is designed and etched into a printed circuit board.  
         [0063]    It is appreciated that ferrite structures may be configured without a post as described above with reference to FIGS. 5-7. To reiterate, it is also appreciated that ferrite structures of various shapes and sized may be attached to the printed circuit board without the use of a hole in the printed circuit board. For example, a ferrite structure can be attached directly to the printed circuit board by glue or other fastening means.  
         [0064]    In certain implementations, it may be advantageous to increase Q values and reactance while simultaneously reducing coupling effects. This can be accomplished by enclosing more of a planar spiral inductor within a ferrite structure. For instance, FIG. 8 shows a cross sectional view of a printed circuit board  502  with a ferrite structure  802  in the shape of a bobbin attached thereto. Since an inductor  800  is essentially flat in this view, brackets represent the general location of the planar inductor  800 . Inductor  800  can be any of the planar inductors described above.  
         [0065]    In this implementation, ferrite structure  802  includes a post  804  and two pedestal structures  806 ( 1 ) and  806 ( 2 ) attached to post  804  at opposite ends  808 ( 1 ) and  808 ( 2 ). Post  804  passes completely through a hole  504 ( 1 ) within printed circuit board  502 . Either of pedestal structures  806 ( 1 ) or  806 ( 2 ) may be integrally connected to post  804  as a unitary structure or one or more of the structures may be attached to post  804 . For example, pedestal structures  806 ( 1 ) and/or  806 ( 2 ) may include a hole  814  capable of receiving post  804 . Pedestal structures  806 ( 1 ) and  806 ( 2 ) are positioned outside hole  504 ( 1 ) and are parallel to one another. Post  804  is generally perpendicular to the pedestal structures  806 ( 1 ) and  806 ( 2 ). Accordingly, pedestal structures referred to generally as  806  thereby sandwich at least a portion of the generally circular high Q value spiral planar inductor  800  between the pedestal structures  806 .  
         [0066]    By sandwiching the generally circular high Q value spiral planar inductor  800 , ferrite structure  802  concentrates greater flux within the inductor than ferrite structures shown in FIGS. 5-7. Additionally, ferrite structure  802  also provides greater protection against unwanted coupling from other components in proximity to the generally circular high Q value spiral planar inductor  800 . Ferrite structure  802  may be held in place on the printed circuit by depositing glue or solder  803  between the printed circuit board  502  and ferrite structure  802 .  
         [0067]    To provide even greater flux within a planar spiral inductor it is possible to completely enclose the inductor within a ferrite structure. For instance, FIG. 9 shows a cross section view of a printed circuit board  502  and ferrite structure  902  attached thereto, the ferrite structure  902  configured to fully capture flux within a spiral planar inductor  900  (since the inductor is planar in this view, brackets represent the general location of the planar inductor  900 ). Inductor  900  can be any of the planar inductors described above. Ferrite structure  902  includes ferrite structure  802  (shown in FIG. 8), but further includes end posts  904 ( 1 ) and  904 ( 2 ), which are also comprised of ferrite magnetic materials. End posts  904 ( 1 ) and  904 ( 2 ) are generally parallel to each other and are perpendicular to pedestal structures  806 ( 1 ) and  806 ( 2 ). In addition to hole  504 ( 1 ) in printed circuit board  502  there are two holes  906 ( 1 ) and  906 ( 2 ) through printed circuit board  502 . Holes  906 ( 1 ) and  906 ( 2 ) provide a means to receive and insert end posts  904 ( 1 ) and  904 ( 2 ), respectively. In this exemplary implementation, the generally circular spiral inductor  900  is sandwiched between pedestal structures  806 ( 1 ) and  806 ( 2 ) and end posts  904 ( 1 ) and  904 ( 2 ). Thus, the generally circular high Q value spiral planar inductor  900  is encased by ferrite structure  902 .  
         [0068]    Although some implementations of the various methods and arrangements of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the exemplary aspects disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.