Abstract:
An oven may include a radio frequency (RF) source, a cooking chamber into which RF energy is providable via the RF source, and a door that is configured to hingedly operate to alternately allow access to the cooking chamber and close the cooking chamber for cooking The door may include a choke assembly disposed to seal a region between the door and a cooking chamber from RF leakage responsive to closure of the door. The choke assembly may include a plurality of tuned chokes, each of which is configured to shield relative to a different predefined frequency.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/606,112, filed Mar. 2, 2012, the contents of each of which are incorporated herein in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    Example embodiments generally relate to ovens and, more particularly, relate to provision of cookware appliances for an oven that is enabled to cook using radio frequency (RF). 
       BACKGROUND 
       [0003]    Combination ovens that are capable of cooking using more than one heating source (e.g., convection, steam, microwave, etc.) have been in use for decades. Each cooking source comes with its own distinct set of characteristics. Thus, a combination oven can typically leverage the advantages of each different cooking source to attempt to provide a cooking process that is improved in terms of time and/or quality. 
         [0004]    Recently, ovens employing RF cooking as at least one mechanism by which a combination oven may cook food product have been developed. However, these ovens also have unique characteristics by virtue of the features made available in connection with the application of the heat sources involved. Such unique characteristics may create challenges relative to previously employed techniques and designs. 
       BRIEF SUMMARY OF SOME EXAMPLES 
       [0005]    Some example embodiments may provide an oven that employs multiple cooking sources, or at least a wide range frequency band RF energy source. Moreover, some example embodiments may further provide for the provision of a choke system that is capable of inhibiting or preventing RF leakage over a relatively broad range of frequencies. 
         [0006]    In an example embodiment, an oven is provided. The oven may include a radio frequency (RF) source, a cooking chamber into which RF energy is providable via the RF source, and a door that is configured to hingedly operate to alternately allow access to the cooking chamber and close the cooking chamber for cooking. The door may include a choke assembly disposed to seal a region between the door and a cooking chamber from RF leakage responsive to closure of the door. The choke assembly may include a plurality of tuned chokes, each of which is configured to shield relative to a different predefined frequency. 
         [0007]    In another alternative embodiment, a choke assembly is provided. The choke assembly may be for provision onto an oven door to seal radio frequency (RF) energy within the oven when the door is closed. The choke assembly may include a plurality of tuned chokes that are concentrically arranged adjacent to each other. Each tuned choke may be configured to shield relative to a different predefined frequency. 
         [0008]    In another example embodiment, an oven may include a radio frequency (RF) source, a cooking chamber into which RF energy is providable via the RF source, and a door that is configured to hingedly operate to alternately allow access to the cooking chamber and close the cooking chamber for cooking. The door may include a at least a double choke disposed to seal a region between the door and a cooking chamber of the oven from RF leakage responsive to closure of the door. The at least double choke may include an outer tuned choke and an inner tuned choke, each of which is configured to shield relative to a same predefined frequency. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0009]    Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
           [0010]      FIG. 1  illustrates a perspective view of an oven capable of employing at least two energy sources according to an example embodiment; 
           [0011]      FIG. 2  illustrates a functional block diagram of the oven of  FIG. 1  according to an example embodiment; 
           [0012]      FIG. 3  illustrates a single tuned choke disposed around an RF screen that may be disposed in a window portion of a door; 
           [0013]      FIG. 4  illustrates a perspective view of a choke assembly including two concentrically disposed chokes according to an example embodiment; 
           [0014]      FIG. 5  illustrates a perspective view of a choke assembly including two concentrically disposed chokes according to an example embodiment; 
           [0015]      FIG. 6 , which includes  FIGS. 6A and 6B , illustrates cross sectional views of a portion of the choke assembly of  FIG. 5  according to an example embodiment; 
           [0016]      FIG. 7  illustrates a perspective view of an internal corner portion of the door to illustrate the choke assembly according to an example embodiment; 
           [0017]      FIG. 8  illustrates an external perspective view of a door according to an example embodiment; 
           [0018]      FIG. 9  illustrates an internal perspective view of the door according to an example embodiment; 
           [0019]      FIG. 10  illustrates a perspective view of a cross section of a choke assembly employing inner chokes associated with each respective tuned choke in accordance with an example embodiment; and 
           [0020]      FIG. 11 , which includes  FIGS. 11A and 11B , illustrates another example embodiment of a tuned choke having a single frequency, double choke according to an example embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Some example embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all example embodiments are shown. Indeed, the examples described and pictured herein should not be construed as being limiting as to the scope, applicability or configuration of the present disclosure. Rather, these example embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout. Furthermore, as used herein, the term “or” is to be interpreted as a logical operator that results in true whenever one or more of its operands are true. As used herein, operable coupling should be understood to relate to direct or indirect connection that, in either case, enables functional interconnection of components that are operably coupled to each other. 
         [0022]    Some example embodiments may improve the performance of an oven employing an example embodiment relative to inhibition or prevention of RF leakage. In this regard, since some example embodiments may implement RF cooking over a wide range of frequencies, a conventional RF choke that would be positioned around the door of the oven to prevent RF leakage may not be sufficient. Such chokes are typically tuned to a single frequency and thus, extensive leakage outside of the single frequency for which the choke was tuned would be expected. Example embodiments may therefore incorporate a multiple choke system so that the wide range of frequencies can be effectively contained. 
         [0023]      FIG. 1  illustrates a perspective view of an oven  10  according to an example embodiment. The oven  10  may be a heating device of any type for heating food products, thawing frozen materials and/or the like. Thus, the oven need not necessarily be embodied only as a combination oven or a microwave oven, but could alternatively be a thawing, warming, sterilizing or other device that applies RF energy. As shown in  FIG. 1 , the oven  10  may include a cooking chamber  12  into which a food product may be placed for the application of heat by any of at least two energy sources that may be employed by the oven  10 . The cooking chamber  12  may include a door  14  and an interface panel  16 , which may sit proximate to the door  14  when the door  14  is closed. In an example embodiment, the interface panel  16  may include a touch screen display capable of providing visual indications to an operator and further capable of receiving touch inputs from the operator. The interface panel  16  may be the mechanism by which instructions are provided to the operator, and the mechanism by which feedback is provided to the operator regarding cooking process status, options and/or the like. 
         [0024]    In an example embodiment, the door  14  may be provided with a choke assembly  15  to prevent leakage of RF energy generated within the cooking chamber  12  to areas external to the oven  10 . The choke assembly  15 , which only conceptually shown in  FIG. 1 , may extend around a window portion of the door  12  to coincide with sidewalls and the top and bottom walls defining the cooking chamber  12 . Thus, when the door  14  is closed, the walls of the cooking chamber  12 , the window portion of the door  12  (if employed), and the choke assembly  15  may combine to contain RF energy and inhibit or prevent RF leakage. The choke assembly  15  will be described in greater detail below. 
         [0025]    In some embodiments, the oven  10  may include multiple racks or may include rack (or pan) supports  18  or guide slots in order to facilitate the insertion of one or more racks or pans holding food product that is to be cooked. In an example embodiment, airflow slots  19  may be positioned proximate to the rack supports  18  (e.g., above the rack supports in one embodiment) to enable air to be forced over a surface of food product placed in a pan or rack associated with the corresponding rack supports  18 . Food product placed on any one of the racks (or simply on a base of the cooking chamber  12  in embodiments where multiple racks are not employed) may be heated at least partially using radio frequency (RF) energy. Meanwhile, the airflow that may be provided may be heated to enable browning to be accomplished. 
         [0026]      FIG. 2  illustrates a functional block diagram of the oven  10  according to an example embodiment. As shown in  FIG. 2 , the oven  10  may include at least a first energy source  20  and a second energy source  30 . The first and second energy sources  20  and  30  may each correspond to respective different cooking methods. However, it should be appreciated that additional energy sources may also be provided in some embodiments. 
         [0027]    In an example embodiment, the first energy source  20  may be an RF energy source configured to generate relatively broad spectrum RF energy to cook food product placed in the cooking chamber  12  of the oven  10 . Thus, for example, the first energy source  20  may include an antenna assembly  22  and an RF generator  24 . The RF generator  24  of one example embodiment may be configured to generate RF energy at selected levels over a range of about 800 MHz to about 1 GHz. The antenna assembly  22  may be configured to transmit the RF energy into the cooking chamber  12  and receive feedback to indicate absorption levels of respective different frequencies in the food product. The absorption levels may then be used, at least in part, to control the generation of RF energy to provide balanced cooking of the food product. 
         [0028]    In some example embodiments, the second energy source  30  may be an energy source capable of inducing browning of the food product. Thus, for example, the second energy source  30  may include an airflow generator  32  and an air heater  34 . However, in some cases, the second energy source  30  may be an infrared energy source, or some other energy source. In examples where the second energy source  30  includes the airflow generator  32 , the airflow generator  32  may include a fan or other device capable of driving airflow through the cooking chamber  12  and over a surface of the food product (e.g., via the airflow slots). The air heater  34  may be an electrical heating element or other type of heater that heats air to be driven over the surface of the food product by the airflow generator  32 . Both the temperature of the air and the speed of airflow will impact browning times that are achieved using the second energy source  30 . 
         [0029]    In an example embodiment, the first and second energy sources  20  and  30  may be controlled, either directly or indirectly, by a cooking controller  40 . Moreover, it should be appreciated that either or both of the first and second energy sources  20  and  30  may be operated responsive to settings or control inputs that may be provided at the beginning, during or at the end of a program cooking cycle. Furthermore, energy delivered via either or both of the first and second energy sources  20  and  30  may be displayable via operation of the cooking controller  40 . The cooking controller  40  may be configured to receive inputs descriptive of the food product and/or cooking conditions in order to provide instructions or controls to the first and second energy sources  20  and  30  to control the cooking process. The first energy source  20  may be said to provide primary heating of the food product, while the second energy source  30  provides secondary heating of the food product. However, it should be appreciated that the terms primary and secondary in this context do not necessarily provide any indication of the relative amounts of energy added by each source. Thus, for example, the secondary heating provided by the second energy source  30  may represent a larger total amount of energy than the primary heating provided by the first energy source  20 . Thus, the term “primary” may indicate a temporal relationship and/or may be indicative of the fact that the first energy source is an energy source that can be directly measured, monitored and displayed. In some embodiments, the cooking controller  40  may be configured to receive both static and dynamic inputs regarding the food product and/or cooking conditions. Dynamic inputs may include feedback data regarding absorption of RF spectrum, as described above. In some cases, dynamic inputs may include adjustments made by the operator during the cooking process (e.g., to control the first energy source  20  or the second energy source  30 ), or changing (or changeable) cooking parameters that may be measured via a sensor network. The static inputs may include parameters that are input by the operator as initial conditions. For example, the static inputs may include a description of the food type, initial state or temperature, final desired state or temperature, a number and/or size of portions to be cooked, a location of the item to be cooked (e.g., when multiple trays or levels are employed), and/or the like. 
         [0030]    In some embodiments, the cooking controller  40  may be configured to access data tables that define RF cooking parameters used to drive the RF generator  34  to generate RF energy at corresponding levels and/or frequencies for corresponding times determined by the data tables based on initial condition information descriptive of the food product. As such, the cooking controller  40  may be configured to employ RF cooking as a primary energy source for cooking the food product. However, other energy sources (e.g., secondary and tertiary or other energy sources) may also be employed in the cooking process. In some cases, programs or recipes may be provided to define the cooking parameters to be employed for each of multiple potential cooking stages that may be defined for the food product and the cooking controller  40  may be configured to access and/or execute the programs or recipes. In some embodiments, the cooking controller  40  may be configured to determine which program to execute based on inputs provided by the user. In an example embodiment, an input to the cooking controller  40  may also include browning instructions or other instructions that relate to the application of energy from a secondary energy source (e.g., the second energy source  30 ). In this regard, for example, the browning instructions may include instructions regarding the air speed, air temperature and/or time of application of a set air speed and temperature combination. The browning instructions may be provided via a user interface as described in greater detail below, or may be provided via instructions associated with a program or recipe. Furthermore, in some cases, initial browning instructions may be provided via a program or recipe, and the operator may make adjustments to the energy added by the second energy source  30  in order to adjust the amount of browning to be applied. In such a case, an example embodiment may employ the cooking controller  40  to account for changes made to the amount of energy to be added by the second energy source  30 , by adjusting the amount of energy to be added via the first energy source  20 . 
         [0031]    A choke configuration may typically include a single tuned choke configured to attenuate RF in a specific and relatively limited frequency range.  FIG. 3  illustrates a single tuned choke  100  disposed around an RF screen  110  that may be disposed in a window portion of a door. In some situations, a choke configuration could be employed in connection with provision of the choke assembly  15  of  FIG. 1  that was achieved by providing adjacent tuned chokes. In this regard, a first tuned choke and a second tuned choke may each be configured to block RF frequencies in specific bands that are determined based on the dimensions of the respective chokes. Thus, for example, the first tuned choke may be configured to block frequencies in the 800-900 MHz range and the second tuned choke may be configured to block frequencies in the 900 MHz to 1 GHz range. The first and second tuned chokes may be welded together, or may be co-extruded together using a single die. In some embodiments, the first and second tuned chokes may be made from an Aluminum extrusion process. 
         [0032]    The choke stock may be extruded in any length and with any desirable tuning characteristics. The choke stock may then be cut and arranged to be disposed around a window portion of the door  14  to form the choke assembly  15  of  FIG. 1 . For example, a choke assembly may be formed by arranging cut pieces of the choke stock to define a window opening for the window portion of the door  14 . The choke assembly may formed by welding together each portion of the choke stock. Thus, after cutting and arranging the choke stock, a plurality of precise welds would need to be formed between each discrete portion of choke stock that forms the choke (e.g., items  200  and  300  of  FIGS. 4 and 5 , respectively). Such welding may be difficult and/or expensive in some cases. 
         [0033]    Accordingly,  FIGS. 4 and 5  illustrate alternative embodiments of choke assemblies that may be utilized to form the choke assembly  15  of  FIG. 1 . However, it should be appreciated that in each of the example embodiments of  FIGS. 4 and 5 , the choke assemblies formed include a plurality of chokes that are tuned to different frequencies and arranged proximate to each other. Furthermore, in these examples, the proximately located chokes can be concentrically arranged around the window portion and around the entrance to the cooking chamber  12 . 
         [0034]    Referring now to  FIG. 4 , a choke assembly  200  is provided that may include a first tuned choke  210 , a second tuned choke  220  and a metallic seal  230 . The first and second tuned chokes  210  and  220  may each be formed structures that are generated from bending, or otherwise forming a metallic structure such that the resultant structure is tuned to attenuate a specific frequency or band of frequencies. For example, the first and second tuned chokes  210  and  220  may each be formed from sheet metal that is folded accordingly. The first tuned choke  210 , which happens to be also the outer tuned choke, may be tuned to choke about 900 MHz to about 1 GHz. Meanwhile, the second tuned choke  220 , which is also the inner choke, may be tuned to choke about 800 MHz to about 900 MHz. However, it should be appreciated that the inner and outer chokes could be reversed and other frequency ranges could be substituted. 
         [0035]    In some embodiments, the first and second tuned chokes  210  and  220  may include a plurality of segmented portions having lengths and gaps therebetween that are selected to tune the corresponding chokes to seal relative to a corresponding selected wavelength of RF energy. In some embodiments, one or both of the chokes may have slots cut into the corner portions of the choke (e.g., see the first tuned choke  210 ). However, one or both of the chokes may instead have a corner portion without any slot provided therein (e.g., see the second tuned choke  220 ). 
         [0036]    The first and second tuned chokes  210  and  220  may be disposed concentrically round the metallic seal  230  and the window portion  240 . In an example embodiment, the metallic seal  230  may be spring loaded or otherwise extend slightly into the cooking chamber  12 . In this regard, for example, the metallic seal  230  may include a plurality of metallic fingers that extend into the cooking chamber  12  to form a seal with the door  14  when the door  14  is closed. In an example embodiment, the first and second tuned chokes  210  and  220  may be covered by a high temperature plastic, Formica®, plastic laminate, resin material or other thin layer of material that actually contacts the face of the oven  10  proximate to the opening into the cooking chamber  12  when the door  14  is closed. In some cases, the allowable gap between the door  14  (i.e., the chokes) and the face of the oven when the door is closed may be less than about 1 mm. 
         [0037]      FIG. 5  illustrates an alternative embodiment in which a choke assembly  300  is provided that includes a first tuned choke  310 , a second tuned choke  320  and a third tuned choke  330 . The first, second and third tuned chokes  310 ,  320  and  330  may each be formed structures that are generated from bending, or otherwise forming a metallic structure such that the resultant structure is tuned to attenuate a specific frequency or band of frequencies. For example, the first, second and third tuned chokes  310 ,  320  and  330  may each be formed from sheet metal that is folded accordingly. The first tuned choke  310 , which happens to be also the outer tuned choke, may be tuned to choke about 1 GHz. Meanwhile, the second tuned choke  320 , which is also the middle choke, may be tuned to choke about 900 MHz. The third tuned choke  330 , which is the inner choke, may be tuned to choke about 800 MHz. However, it should be appreciated that the inner, middle and outer chokes could be rearranged in their orders and other frequency ranges could be substituted. According to this embodiment, leakage may be prevented over a desired frequency band (e.g., 800 to 1000 MHz) by providing a plurality of tuned chokes (e.g., three) with tuned center frequencies that are equidistantly spaced apart over the range of the desired frequency band. Thus, overall attenuation over the range of frequencies that are desired for shielding may be relatively strong. 
         [0038]    In some embodiments, the first, second and third tuned chokes  310 ,  320  and  330  may include a plurality of segmented portions having lengths and gaps there between (e.g., to define fingerlike projections) that are selected to tune the corresponding chokes to seal relative to a corresponding selected wavelength of RF energy. In some embodiments, one, some or all of the chokes may have slots cut into the corner portions of the choke (e.g., see the first tuned choke  310  and the third tuned choke  330 ). However, one, some or all of the chokes may instead have a corner portion without any slot provided therein (e.g., see the second tuned choke  320 ). In some embodiments, chokes with and without slots cut in the corner portions may be alternated (as shown in  FIG. 5 ). 
         [0039]    The first, second and third tuned chokes  310 ,  320  and  330  may be disposed adjacent to one another concentrically round the window portion  340 . In an example embodiment, the first, second and third tuned chokes  310 ,  320  and  330  may be covered by a plastic, Formica, or other thin layer of material that actually contacts the face of the oven  10  proximate to the opening into the cooking chamber  12  when the door  14  is closed. In some cases, the allowable gap between the door  14  (i.e., the chokes) and the face of the oven when the door is closed may be less than about 1 mm. 
         [0040]    In some embodiments, the first, second and third tuned chokes  310 ,  320  and  330  may be attached to one another via a welding process or any other suitable joining mechanism.  FIG. 6 , which includes  FIGS. 6A and 6B , illustrates cross sectional views of a portion of the choke assembly  300  of  FIG. 5 . In this regard,  FIG. 6A  illustrates a side view of the cross section of the choke assembly  300  and  FIG. 6B  illustrates a perspective view of the cross section of the choke assembly  300 . As can be seen in  FIG. 6 , the size of each choke assembly  300  may be different. While the tuned chokes may be arranged such that the largest sized chokes are internally disposed and smaller sized chokes are on the outside, it should be appreciated that some designs may depart from that arrangement and institute an opposite ordering or even an ordering that is not dependent upon size. Each of the chokes of the choke assembly  300  may be configured to define a cavity that is tuned to reject or reflect a corresponding nominal frequency (e.g., 800 MHz, 900 MHz and 1000 MHz) based on arranging the corresponding conductive path lengths to be less than or equal to ¼λ where λ is wavelength of the nominal frequency in question. Thus, for example, the shortest cavity wall (i.e., the wall tuned to 1000 MHz) may include three component walls that measure 40 mm, 20 mm and 15 mm, respectively, for a total conductive path length of 75 mm. The speed of light is about 3.0×10 8  m/s, so the quarter wavelength at 1000 MHz is about 75 mm. Similar calculations may be used to provide the total conductive path lengths to be used for the larger cavities of the 900 MHz and 800 MHz chokes. 
         [0041]      FIG. 6  also illustrates a layer of material forming a cover  350  that may be easy to clean and maintain, while still providing for a relatively small gap between the choke assembly  300  and the face of the oven  10  when the door  14  is closed. The cover  350  may be made of high temperature plastic, Formica®, plastic laminate, resin material or other thin layer of material that is relatively smooth and easy to clean. As shown in  FIG. 6 , the side of the door that faces the oven may be constructed such that each of the tuned chokes is aligned so that when the cover  350  is applied, a smooth face is presented to provide a relatively tight fit with the face of the oven  10  when the door is closed. As such, the uneven portions of the tuned chokes may be outwardly disposed and an external door covering, or door frame may be provided to give an aesthetically pleasing view of the door  14  from the outside.  FIG. 7  illustrates a perspective view of an internal corner portion of the door to illustrate the choke assembly  300  and the alternating disposal of tuned chokes having corner slots as described above.  FIG. 7  also shows how the interior faces of the tuned chokes may be aligned so that the cover  350  may be applied to provide a smooth surface for cleaning and providing a tight fit with a face of the oven  10 . 
         [0042]      FIG. 8  illustrates an external perspective view of a door according to an example embodiment. Meanwhile,  FIG. 9  illustrates an internal perspective view of the door. As can be seen in  FIGS. 8 and 9 , the door includes a window portion  400  surrounded by a door frame  410 . The outer choke  420  is then shown on a back portion of the door  14 . The window portion  400  may include glass, RF screens, combinations thereof, or other screening mechanisms. The outer choke  420  is covered by the cover  430 . The door may be mounted on a hinge assembly  440  and may include a latch assembly  450  to enable opening and closing of the door in addition to latching of the door when the door is closed. 
         [0043]    Although some example embodiments may be tuned only to center frequencies of 800 MHz, 900 MHz and 1000 MHz in order to provide attenuation in the range from about 800 MHz to 1000 MHz, it may be possible to further configure some embodiments to include partial chokes that are defined as inner chokes within the other tuned chokes.  FIG. 10  illustrates an example embodiment of a choke assembly  500  including first, second and third tuned chokes  510 ,  520  and  530  that may be disposed proximate to each other to prevent RF energy leakage from an oven door over the range of about 800 MHz to about 1000 MHz. In some cases, the first, second and third tuned chokes  510 ,  520  and  530  may be affixed to one another via a welding process, may be co-extruded or may be joined via any other suitable joining mechanism.  FIG. 10  illustrates a cross sectional view of a portion of the choke assembly  500  of  FIG. 10 . However, it should be appreciated that the first, second and third tuned chokes  510 ,  520  and  530  may extend around a window portion of an oven door to coincide with sidewalls and the top and bottom walls defining the cooking chamber of the oven. Thus, when the door is closed, the walls of the cooking chamber, any window portion of the door (if employed), and the choke assembly  500  may combine to contain RF energy and inhibit or prevent RF leakage from the oven. 
         [0044]    The first, second and third tuned chokes  510 ,  520  and  530  may be concentrically arranged such that each of the first, second and third tuned chokes  510 ,  520  and  530  lie substantially in a same plane (e.g., a plane substantially parallel to a plane in which the door lies). The first, second and third tuned chokes  510 ,  520  and  530  could be provided concentrically in any order. Thus, for example, the tuned choke having the largest conductive path length could be the largest concentrically arranged tuned choke (i.e., having the largest perimeter length), or could be the smallest concentrically arranged tuned choke (i.e., having the smallest perimeter length), or could be in between the other tuned chokes. 
         [0045]    As shown in  FIG. 10 , the first tuned choke  510  may include a first primary choke portion (defined by a first wall  540 , a second wall  542  and a third wall  544 ) and a first inner choke portion  546 . The first inner choke portion  546  may further include at least three component walls that define portions of the conductive path length of the first inner choke  546 . As shown in  FIG. 10 , the second tuned choke  520  may include a second primary choke portion (defined by a first wall  550 , a second wall  552  and a third wall  554 ) and a second inner choke  556 . Similar to the first tuned choke  510 , the second inner choke  556  of the second tuned choke  520  may also include at least three component walls that define portions of the conductive path length of the second inner choke  556 . Likewise, the third tuned choke  530  may include a third primary choke portion (defined by a first wall  560 , a second wall  562  and a third wall  564 ) and a third inner choke  566 . Similar to the first and second tuned chokes  510  and  520 , the third inner choke  566  of the third tuned choke  530  may also include at least three component walls that define portions of the conductive path length of the third inner choke  566 . 
         [0046]    In an example embodiment, the first walls  540 ,  550  and  560  of each of the first, second and third tuned chokes  510 ,  520  and  530  may have lengths that are wavelength dependent. Similarly, the second walls  542 ,  552  and  562  of the first, second and third tuned chokes  510 ,  520  and  530  may also be substantially the same length (although the length of the second walls may be different than the lengths of the first walls). The third walls  544 ,  554  and  564  of each of the first, second and third tuned chokes  510 ,  520  and  530  may also be substantially the same length (although the length may be different than that of the first walls and/or second walls). Thus, tuning differences between the first, second and third tuned chokes  510 ,  520  and  530  may be provided based on the placement and/or path lengths defined by the respective inner chokes (e.g., the first inner choke  546 , the second inner choke  556  and the third inner choke  566 ). In some embodiments, the first, second and third inner chokes  546 ,  556  and  566  may be formed of consecutively arranged “fingers” that extend parallel to one another. In other words, there may be slots or relatively small spaces formed between each of the fingers (similar to the slots formed between fingers of the walls of the first, second and third tuned chokes  510 ,  520 ,  530 ). In an example embodiment, each of the fingers may have a length of less than or equal to a quarter wavelength relative to the tuned frequency for each respective choke. 
         [0047]    In the example shown in  FIG. 10 , the first inner choke  546  may extend away from the first wall  550  of the second tuned choke  520  toward the first wall  540  of the first tuned choke  510 . The second inner choke  556  may extend away from the first wall  560  of the third tuned choke  530  toward the first wall  550  of the second tuned choke  520 . The third inner choke  566  may extend toward the first wall  560  of the third tuned choke. The secondary choke geometries defined by the inclusion of the inner chokes ( 546 ,  556  and  566 ) within each primary choke to define the first, second and third tuned chokes  510 ,  520  and  530  may be selected to also meet the quarter wavelength criteria mentioned above. However, for the same frequency range (e.g., 800 MHz to 1000 MHz), some example embodiments have shown an increase in the attenuation provided relative to embodiments that do not employ the inner chokes. 
         [0048]    Although  FIG. 10  shows multiple adjacently disposed tuned chokes with each tuned choke having a respective inner choke, it should be appreciated that a multiple layer choke could alternatively be provided to be tuned to a single frequency rather than to multiple different frequencies.  FIG. 11 , which includes  FIGS. 11A and 11B , illustrates another example embodiment of a tuned choke having a single frequency, double choke according to an example embodiment. In this regard,  FIG. 11A  illustrates a cross section view of a portion of a double choke  600 . The double choke  600  includes an outer tuned choke  610  and an inner tuned choke  620 . The outer tuned choke  610  and the inner tuned choke  620  may each be tuned to the same frequency. In one example embodiment, the outer tuned choke  610  and the inner tuned choke  620  may each be tuned to a frequency of about 915 MHz+/−13 MHz. However, the double choke  600  may further assist in preventing leakage responsive to phase changes made at the tuned frequency. 
         [0049]    As shown in  FIG. 11 , the outer tuned choke  610  may include a first wall  612 , a second wall  614  and a third wall  616 . Meanwhile, the inner tuned choke  620  may include a first wall  622 , a second wall  624  and a third wall  626 . Lengths of the first, second and third walls of each of the first and second tuned chokes  610  and  620  may be selected to be less than or equal to a quarter wavelength relative to the tuned frequency of the double choke  600 . 
         [0050]    In an example embodiment, the first wall  612  of the outer tuned choke  610  may extend substantially perpendicular to a cover  630  (e.g., similar to cover  350 ) that may define a portion of the door that meets up with the oven and extends around the front opening of the oven that is sealed by the double choke  600  to prevent leakage of RF energy out of the oven. The second wall  614  of the outer tuned choke  610  may extend adjacent and substantially parallel to the cover  630 . The third wall  616  of the outer tuned choke  610  may extend substantially perpendicular to the second wall  614  and substantially parallel to the first wall  612 . As such, for example, the first wall  612  and the third wall  616  may extend parallel to each other from opposite ends of the second wall  614 . 
         [0051]    In an example embodiment, the first wall  622  of the inner tuned choke  620  may extend substantially perpendicular to the second wall  624  of the inner tuned choke  620 . Meanwhile, the second wall  624  of the inner tuned choke  620  may extend substantially parallel to the first wall  612  of the outer tuned choke  610 . The first wall  622  of the inner tuned choke  620  may also extend substantially parallel to the second wall  614  of the outer tuned choke  610 . The third wall  626  of the inner tuned choke  620  may extend substantially perpendicular to the second wall  624  and substantially parallel to the first wall  622 . As such, for example, the first wall  622  and the third wall  626  may extend parallel to each other from opposite ends of the second wall  624 . In an example embodiment, the third wall  616  of the outer tuned choke  610  may extend toward the first wall  622  of the inner tuned choke  620 . Meanwhile, the third wall  626  of the inner tuned choke  620  may extend away from the first wall  612  of the outer tuned choke  610 . 
         [0052]    In some embodiment, slots  640  may be formed between fingers of the inner and outer tuned chokes  610  and  620  as described above. The inner tuned choke  620  may be proximate to a window in the door, while the outer tuned choke  610  extends around a periphery of the door. Thus, the inner tuned choke  620  may be “inwardly” disposed relative to the periphery of the door. However, the inner tuned choke  620  may also be considered to be an “inner” choke based on the fact that the second and third walls  624  and  626  of the inner tuned choke  620  may be disposed to fit substantially within the length and width dimensions defined by the walls of the outer tuned choke  610 . As such, the inner tuned choke  620  may appear to be disposed within the outer tuned choke  610 . 
         [0053]    Example embodiments may provide a multiple layer choke system instead of a single choke and may therefore provide an ability to provide coverage over a wider range of frequencies instead of over just a single frequency. Some example embodiments may also provide a choke system that has a reduced fabrication cost while still providing a robust attenuation capability relative to welded structures. 
         [0054]    Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe exemplary embodiments in the context of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. In cases where advantages, benefits or solutions to problems are described herein, it should be appreciated that such advantages, benefits and/or solutions may be applicable to some example embodiments, but not necessarily all example embodiments. Thus, any advantages, benefits or solutions described herein should not be thought of as being critical, required or essential to all embodiments or to that which is claimed herein. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.