Abstract:
A waveguide structure for a dual polarization waveguide includes a first flange member, a second flange member, and a waveguide member disposed in each of the first flange member and second flange member. The first flange member and the second flange member are configured to be coupled together in a spaced-apart relationship separated by a gap. The first flange member has a substantially smooth surface, and the second flange member has an array of two-dimensional pillar structures formed therein.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to, and the benefit of, U.S. Provisional Patent Application Ser. No. 61/333,395, filed on May 11, 2010, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     GOVERNMENT LICENSE RIGHTS 
       [0002]    This invention was made with government support under ROSS/APRA proposal number 06-APRA06-11, awarded by the National Aeronautics and Space Administration. The government has certain rights in the invention. 
     
    
     BACKGROUND 
       [0003]    The present disclosure generally relates to waveguide joints, and more particularly, to a photonic choke joint structure for dual-polarization single-mode waveguides. 
         [0004]    A waveguide joint is the location where two waveguides are connected or coupled to produce a reliable contact between two waveguide components, and typically provides an interface for a variety of modularized waveguide components. In general, two waveguides must be accurately aligned and have a low impedance electrical contact at the joint. Typically, this is done by having the two flat metallic waveguide flange surfaces make physical contact at the interface. 
         [0005]    Ideally, a waveguide joint is lossless and reflectionless. In practice, it is sometimes necessary and/or desirable to realize this property with a non-contacting waveguide joint interface. For example, in some applications that require thermal isolation at the joint, the physical contact interface cannot be achieved. Without good electrical contact between two waveguide flanges, a few key problems arise. One problem is that the spacing between the mating or coupling surfaces of the two waveguides produces power leakage and reduces the efficiency of the joint. Another is that the spacing or gap between the two waveguides, also referred to as the flange interface, can produce spurious responses that interfere with the transmission in the waveguide. These spurious responses are highly dependent on the gap spacing and the shape of the waveguide. Finally, the gap also sets the limit in the waveguide breakdown voltage and its maximum operating power. 
         [0006]    A half-wave choke structure at the flange interface requires good electrical contact and allows the joint to handle high power. One example of such a structure for a single-mode waveguide is the hexagonal tiling of metallic square pillars. The hexagonal tiling has been used for a standard 2.000:1 rectangular waveguide. However, this hexagonal tiling structure does not support dual polarization signal transmission. The half-wave choke structure also has a limited operating bandwidth and does not provide thermal isolation between the two waveguides. A hexagonal tiling photonic choke flange produces a broadband response and a low loss contact interface. However, the hexagonal tiling photonic choke flange structure does not have four-fold symmetry and produces spurious responses when this interface is used in a waveguide with dual polarization. 
         [0007]    Accordingly, it would be desirable to provide a system that addresses at least some of the problems identified above. 
       BRIEF DESCRIPTION 
       [0008]    As described herein, the exemplary embodiments overcome one or more of the above or other disadvantages known in the art. 
         [0009]    One aspect of the exemplary embodiments relates to a waveguide structure for a dual polarization waveguide. In one exemplary embodiment, the waveguide structure includes a first flange member, a second flange member, and a waveguide member disposed in each of the first flange member and second flange member. The first flange member and the second flange member are configured to be coupled together in a spaced-apart relationship separated by a gap. The first flange member has a substantially smooth surface, and the second flange member has an array of two-dimensional pillar structures formed therein. 
         [0010]    Another aspect of the exemplary embodiments relates to a photonic choke joint. In one exemplary embodiment, the photonic choke joint includes a first flange member having a substantially flat surface, a second flange member having a plurality of pillar structures formed therein and a square dual-polarization waveguide disposed in each of the first and second flange members. The plurality of pillar structures are arranged in a Cartesian tiling pattern. 
         [0011]    A further aspect of the exemplary embodiments relates to a photonic choke joint. In one exemplary embodiment, the photonic choke joint includes a first flange member having a substantially flat surface and a second flange member having a plurality of pillar structures formed therein. The pillar structures are arranged in an Archimedean tiling pattern. A dual-polarization waveguide is disposed in each of the first and second flange members. 
         [0012]    These and other aspects and advantages of the exemplary embodiments will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. Moreover, the drawings are not necessarily drawn to scale and unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein. In addition, any suitable size, shape or type of elements or materials could be used. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    In the drawings: 
           [0014]      FIG. 1  is a perspective view of a waveguide structure incorporating aspects of the exemplary embodiments. 
           [0015]      FIG. 2(   a ) is an assembly view,  FIG. 2(   b ) is a plan view, and  FIG. 2(   c ) is a side cross-sectional view of the waveguide structure of  FIG. 1 . 
           [0016]      FIG. 3  is a plan view of one embodiment of a Cartesian tiling configuration of pillars in a photonic choke joint incorporating aspects of the exemplary embodiments. 
           [0017]      FIG. 4  is a plan view of an Archimedean tiling configuration of pillars in a photonic choke joint incorporating aspects of the exemplary embodiments. 
           [0018]      FIGS. 5(   a ),  5 ( b ), and  5 ( c ) illustrate plan views of exemplary pillar configurations,  FIGS. 5(   d ),  5 ( e ), and  5 ( f ) are cross-sectional views of each pillar configuration, respectively, and  FIG. 5(   g ) illustrates the simulated input impedance effectiveness of each respective pillar configuration in a photonic choke joint incorporating aspects of the exemplary embodiments. 
           [0019]      FIGS. 6(   a ) and  6 ( b ) illustrate the simulated power leakage, transmission, and reflection for an exemplary Cartesian tiling configuration in a photonic choke joint incorporating aspects of the exemplary embodiments. 
           [0020]      FIG. 7  illustrates an exemplary layout of pillars for an Archimedean tiling configuration for a photonic choke joint incorporating aspects of the exemplary embodiments. 
           [0021]      FIGS. 8(   a ) and  8 ( b ) illustrate simulated power leakage, transmission, and reflection for an exemplary Cartesian tiling configuration in a photonic choke joint incorporating aspects of the exemplary embodiments. 
           [0022]      FIGS. 9(   a ) and  9 ( b ) illustrate the modeled frequency response of the power leakage for exemplary photonic choke joints incorporating Cartesian and Archimedean tiling configurations, respectively, with different numbers of rows of pillars. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Referring to  FIG. 1 , an exemplary waveguide interface structure incorporating aspects of the exemplary embodiments is generally designated by reference numeral  10 . The aspects of the exemplary embodiments are directed to a reliable, highly efficient, and non-contact joint for waveguides with dual-polarizations. Common examples of dual-polarization waveguides include waveguide structures with square, round and quad-ridge cross-sectional geometries. The aspects of the exemplary embodiments will generally be described with respect to a square waveguide, although waveguides of other cross-sectional geometries are contemplated within the scope of the exemplary embodiments. In one exemplary embodiment, the waveguide interface structure  10  will also be referred to as a “photonic choke joint” (PCJ). 
         [0024]    The aspects of the exemplary embodiments generally provide a dual-mode waveguide interface structure  10  that includes two flanges  100 ,  200 .  FIG. 2   a  illustrates a plan view of the waveguide interface structure  10  prior to assembly, while  FIG. 2   b  illustrates a plan view of the assembled waveguide interface structure  10 .  FIG. 2   c  illustrates a cross-sectional view of the waveguide interface structure  10  shown in  FIG. 2   b , taken along the line A-A′. 
         [0025]    As shown in  FIGS. 2(   a )- 2 ( c ), a waveguide  12  is disposed in each of the flanges  100 ,  200 . The portions of the waveguide  12  in each of the flanges  100 ,  200  are generally referred to as waveguide ports  22 ,  24 , respectively. The first waveguide flange  100 , also referred to as flange  100 , generally includes a substantially flat or smooth surface  102 , which may also be referred to as electrically reflective. The surface  102  of the first waveguide flange  100  generally includes the equivalent of a perfect electrical conductor wall. The surface  102  is substantially perpendicular to the wall  18  of the waveguide  12 . The second waveguide flange  200 , also referred to as flange  200 , generally includes a surface  202  comprising an infinite period two-dimensional array  204  of metallic structures. As is illustrated in the example of  FIG. 1 , the array  204  generally includes rows  206  of pillars  208 . In one exemplary embodiment, the rows  206  of pillars  208  can be tiled in either Cartesian or Archimedean patterns, as will be further described herein. 
         [0026]    When combined with the substantially flat surface  102  of the first flange  100 , the electrical model of the waveguide structure  10  becomes an infinite three-dimensional tiling of pillars due to the self-mirroring of the structure. This produces a reflective response to an excited wave at certain frequency ranges that can be dependent on factors such as the pillar shape, and spacing among and between the pillars, for example. 
         [0027]    In one exemplary embodiment, the waveguide structure  10  produces a highly reflective band-stop filter at the wave guide flange interface or joint  14 , shown, for example, in  FIG. 2 . The waves that are introduced into the interface  14  will see a highly reflective surface and see the joint  14  as an electrical short circuit in the operating frequency band. The signal therefore continues to propagate along its path in and through the waveguide  12  rather than into the joint  14 . The Cartesian and Archimedean tiling patterns have four-fold and eight-fold symmetry, respectively, and two polarized signals in the dual-polarized waveguide structure  10  realizes the same impedance characteristics at the joint  14 . The tiling patterns need to have four-fold or higher symmetry for dual polarization guiding structures. With four-fold or higher symmetry, each of the polarizations encounters the same boundary conditions upon interacting with the joint  14 . As a result, the frequency response of the waveguide structure  10 , when excited by signals in two polarizations, is substantially identical. In addition, the size of the pillars array  204  determines the level of leakage around the center of the operating band. 
         [0028]    Referring to  FIGS. 3 and 4 , the aspects of the exemplary embodiments use tiling arrangements that are suitable for waveguide implementation in terms of ease of fabrication and design. For fabrication simplicity, the pillars  208  are metallic, with either a square cross-section arranged in four-fold translation symmetry, as illustrated in  FIG. 3 , or a circular cross-section arranged in eight-fold rotational symmetry, as illustrated in  FIG. 4 . The configuration shown in  FIG. 3  is referred to herein as “Cartesian” PCJ tiling, while the configuration shown in  FIG. 4  is referred to herein as “Archimedean” or “octagonal” tiling. 
         [0029]    Referring to  FIG. 2(   b ), the parallelism of the flanges  100 ,  200  is controlled, as is the size of the separation or gap  16  between the two flanges  100 ,  200  at the interface  14 . The gap  16  generally includes a spacing between a top surface of the pillar  208 , generally referred to as  202  and the upper metal reflective plane, generally referred to as  102 . 
         [0030]    Referring to  FIG. 3 , in this exemplary embodiment, the flange  200  includes a Cartesian tiling scheme  210  of square pillars  208  that are rotated relative to orientation of the walls  18  of waveguide  12 . Each pillar  208  has a width generally indicated by  212 . A spacing or distance between adjacent pillars  208  is generally indicated by  214 . The width  212  and spacing  214  are tuned relative to a width  216  of the waveguide  12 , also referred to herein as “waveguide width  216 .” The term “waveguide width” is generally understood in the art as referring to the guide&#39;s broadwall width (e.g., for a standard WR22.4 rectangular waveguide the width “a” of the guide is 0.224 inches, and the height “b” is 0.112 inches). The aspects of the exemplary embodiments allow the waveguide structure to be scaled to operate in any waveguide band. 
         [0031]    The orientation of the pillars  208  with respect to the laterally-propagating waves is configured to provide the maximum confinement. Where the waveguide  12  is square, as shown in the example of  FIG. 3 , the majority of the constituent transmission modes propagate in a direction that is generally perpendicular to the walls  18  of the waveguide  12 . 
         [0032]      FIGS. 5(   a )- 5 ( c ) illustrate plan views of exemplary pillar configurations. In  FIG. 5   a , the pillars  208  are shown in in “in-line” configuration  500 , each pillar  208  having a width  504  and a spacing  506  between each pillar  208 . Lines  501  and  503  illustrate the magnetic wall of the flange  200 , while lines  505  and  507  illustrate the plane wave excitation port.  FIG. 5(   d ) is a cross-sectional view of the inline configuration  500  taken along the line A-A′. 
         [0033]    In  FIG. 5(   b ), the each pillar  208  is arranged in an “alternating” configuration  510 , each pillar  208  having a width  516  and a spacing  516  between each pillar  208 .  FIG. 5(   e ) is a cross-sectional view of the alternating configuration  510  taken along the line B-B′. 
         [0034]    In  FIG. 5(   c ), the pillars  208  of  FIGS. 5(   a ) and  5 ( b ) are rotated approximately 45 degrees relative to the orientation of the walls  18  of the square waveguide  12  shown in  FIG. 3 . The pillars  208  form a 45-degree rotated pillar configuration  520 . Each pillar  208  in this exemplary embodiment has a width  212 , with a spacing  214  between each.  FIG. 5(   f ) is a cross-sectional view of the 45-degree pillar configuration  520  taken along the line C-C′. 
         [0035]    Referring to  FIG. 5(   a ), it was observed during modeling, that a Cartesian tiling arrangement of five rows of pillars  208  in an inline configuration  500 , relative to the walls  18  of the waveguide  12  shown in  FIG. 3 , produces the highest input impedance with numerous in-band spurious responses, as is illustrated by line  530  in the graph shown in  FIG. 5(   g ). The graph in  FIG. 5(   g ) illustrates the input impedance effectiveness of each of the configurations shown in  FIGS. 5(   a )- 5 ( c ). In the example of  FIG. 5(   a ), the width  504  of each pillar  208  in the inline configuration  500  is approximately 0.6a, where “a” represents the waveguide width  216  described above, and shown in  FIG. 3 , for the particular waveguide design being used. In this example, the spacing  506  between adjacent pillars  208  is approximately 1.12a. With an offset or alternating arrangement  510  of pillars  208 , the lowest input impedance is produced, as illustrated by line  532  in the graph, corresponding to the alternating pillar arrangement  516 . The width  514  of each pillar  208  in the alternating configuration  510  is approximately 0.75a, while the spacing  516  between adjacent pillars  208  is approximately 1.12a. However, the alternating tiling configuration  510  of pillars  208  does not produce the desired symmetrical response in the square waveguide  12  due to the lack of four-fold symmetry. The exemplary 45-degree rotated pillar configuration  520  shown in  FIGS. 3 and 5(   c ) provides the maximum confinement of the laterally-propagating waves and provides the lowest input impedance, shown by line  534 , compared to the characteristic impedance of free space in order to create the stop band over a large bandwidth. In the rotated configuration example shown in  FIG. 5(   c ), the width  212  of each rotated pillar  208  is approximately 0.4a, while the spacing  214  between adjacent rotated pillars  208  is approximately 0.68a. It is noted that a height  220  of the rotated pillars  208  and the flange spacing  216  has a substantially insignificant effect on the input impedance response. In one exemplary embodiment, the height  220  of each rotated pillar  208  is approximately 0.037a, while the spacing  216  between the flanges  100 ,  200  is simulated in this example to be approximately 0.0088a, for each of the inline  500 , alternating  510  and rotated 520 arrangements. 
         [0036]    To achieve the desired field confinement for the waveguide structure  10  to function nearly ideally, at least three rows of pillars  208  must be used in the 45-degree rotated pillar configuration  520 .  FIGS. 6(   a ) and  6 ( b ) illustrate the simulated power leakage, transmission and reflection of a waveguide structure  10  incorporating Cartesian tiling in accordance with the aspects of the exemplary embodiments, having three rows  206  of rotated pillars  208 .  FIG. 6(   a ) illustrates the total power lost, the total power less the power reflected and transmitted by the structure  10  incorporating Cartesian tiling. In  FIG. 6(   b ), the set of curves  601  illustrates the power transmission loss in [dB], with reference to the right axis, while the set of curves  603  illustrate the power reflection from the joint  14 , with reference to the left axis. 
         [0037]    In the example of  FIGS. 6(   a ) and  6 ( b ), the width  212  of each pillar  208  is approximately 0.68a, while the spacing  214  between adjacent pillars  208  is approximately 0.4a. The parameter that is varied, represented by the lines  602 - 630  on the graphs, is the gap  16  between the non-contacting surfaces of the flanges  100 ,  200 , which is varied in the range of approximately 0.0088a to 0.0439a. Lines  602 ,  612  and  622  are for a gap spacing of 0.0088a. Lines  604 ,  614  and  624  are for a gap spacing of 0.0176a. Lines  606 ,  616  and  626  are for a gap spacing of 0.0264a. Lines  608 ,  618  and  628  are for a gap spacing of 0.0352a. Lines  610 ,  620  and  630  are for a gap spacing of 0.0439a. The results show that the waveguide structure  10  in this embodiment produces a leakage of less than 0.001 up to 1.61 f c , where f c  is the cutoff frequency of the parent waveguide structure, when the spacing  16  between the flanges  100 ,  200  is below 0.0088a. The cutoff frequency f c  is the frequency at which the fields are “cutoff” and do not propagate down the waveguide  12 . This frequency f c  is related to the width  216 , the guide broadwall width “a”, by f c =co/(2a), where co is the speed of light in freespace.  FIGS. 6(   a ) and  6 ( b ) are plotted in these units because one can convert the x-axis to physical units (e.g., GHz) by suitably multiplying by the cutoff frequency f c  for the waveguide in use. In so called “full” waveguide band applications, where 1&lt;f c &lt;2, strictly speaking for a square guide, the waveguide is only single mode over a smaller range; however, with appropriate care, steps can be taken to use the commonly used language for a 2.000:1 rectangular guide. The power leakage is determined by the S-parameter relationship: 1−|S 21 | 2 −|S 11 | 2 , since the signals at both waveguide ports  22 ,  24  are highly symmetric. The Cartesian configuration of pillars  208  provides reflections that are less than −24 dB without in-band spurious response to approximately 1.82 f c . The power leakage of less than 1% can be maintained when the gap spacing  214  is less than approximately 0.035a. Generally, the gap spacing  16  between the flanges  100 ,  200 , can vary from approximately 0.0088a to 0.0352a, inclusive of endpoints. When the gap spacing  16  is substantially zero, a constant loss is observed across the measurement band. As the gap spacing  16  is increased, the high frequency response is degraded. Low in-band power leakage of less than approximately 3% is realized when the gap spacing  16  is smaller than 0.028a (e.g. 0.16 mm). 
         [0038]    Referring to  FIG. 4 , in one exemplary embodiment, the second flange  200  includes an arrangement  402  of circular pillars  408 . As is shown in  FIG. 7 , in this example, a quasi-crystal arrangement  402  of circular pillars  408 , also referred to as an Archimedean tiling arrangement of circular pillars, is used that provides an eight-fold symmetry and a suitable placement of the waveguide  12  at the center  702  of the arrangement  402 . In this example, four rows  704 ,  706 ,  708  and  710  of circular pillars  408  are placed at the vertices of the quasi-crystal configuration  402 . To achieve the desired field confinement, three or more rows of circular pillars  408  need to be used. Generally, an improvement in performance of the waveguide structure  10  will be realized with an increasing number of rows. However, for purposes of the description herein, and the test structures, the aspects of the exemplary embodiments will generally be described with respect to the use of arrays having three to five rows, inclusive of end points. 
         [0039]    The optimized dimensions of the Archimedean structure  402  shown in  FIGS. 4 and 7  yield a waveguide transition with low power leakage when the spacing  406  between adjacent pillars  408  is less than or below approximately 0.0088a.  FIGS. 8(   a ) and  8 ( b ) illustrate the simulated power leakage, transmission and reflection of the Archimedean tiling structure  402 . It is noted that, for this simulation, three rows of pillars  408  are used where a diameter  404  of each pillar  408  is approximately 0.18a. The spacing  406  between adjacent pillars  408  in this example is approximately 0.68a. The parameter that is varied in  FIGS. 8(   a ) and  8 ( b ) is the gap  16  between the non-contacting surfaces of the flanges  100 ,  200 , which is in the range of approximately 0.0088a to 0.0439a.  FIG. 8(   a ) illustrates the total power lost, which is the total power less the power reflected and transmitted by the structure  402 . In  FIG. 8(   b ), the set of curves  801  illustrates the power transmission loss in [dB], with reference to the right axis, while the set of curves  803  illustrate the power reflection from the joint  14 , with reference to the left axis. Lines  802 ,  812  and  822  are for a gap spacing of 0.0088a. Lines  804 ,  814  and  824  are for a gap spacing of 0.0176a. Lines  806 ,  816  and  826  are for a gap spacing of 0.0264a. Lines  808 ,  818  and  828  are for a gap spacing of 0.0352a. Lines  810 ,  820  and  830  are for a gap spacing of 0.0439a.  FIGS. 8(   a ) and  8 ( b ), as well as  FIGS. 6(   a ) and  6 ( b ), illustrate the sensitivity that is needed to ensure proper operation of the waveguide structure  10 . If the surfaces of the flanges  100 ,  200  that make up the waveguide structure  10  touch, that is ideal. However, as performance gradually degrades with finite and realizable separations between the two flanges  100 ,  200 , as is shown in  FIGS. 6(   a ),  6 ( b ),  8 ( a ), and  8 ( b ). 
         [0040]    As noted above, the power leakage of the waveguide structure  10  is generally dependent on the number of rows  206  of pillars  208 . As the number of rows  206  increases, for both the Cartesian and Archimedean tiling configurations, the power leakage is substantially reduced around the center of the operating band. However, the number of rows has little effect near the upper and lower end of the operating bandwidth. An example of this is illustrated in  FIGS. 9(   a ) and  9 ( b ), which illustrates the frequency response of power leakage for the Cartesian and Archimedean waveguide structures described herein, having different numbers of rows  206  of pillars  208 . In  FIG. 9(   a ), lines  902 ,  904 ,  906 , and  908  represent the frequency response for one, two, three, and four rows, respectively, in a Cartesian tiling configuration of a waveguide structure  10  incorporating aspects of the exemplary embodiments. In  FIG. 9(   b ), lines  910 ,  912 ,  914 ,  916  represent the frequency response for one, two, three, and four rows, respectively, in an Archimedean tiling configuration in a waveguide structure  10  incorporating aspects of the exemplary embodiments. For practical purposes, a finite number of rows  206  of pillars  208  can be used in the waveguide structure  10 , while maintaining a low loss interface. 
         [0041]    In one exemplary embodiment, the waveguide structure  10  is fabricated from oxygen free copper. The square waveguide  12  is realized via electroforming. Generally, the designs for the waveguide structure  10  incorporating aspects of the exemplary embodiments are based on the WR22.4 waveguide standard, where f c =26.35 GHz, although in alternate embodiments, other applicable waveguide standards are contemplated as well. 
         [0042]    The pillars  208  are reflective and depending upon the frequency band of interest, can be realized in a variety of different methods. For example, for low frequency applications, i.e., microwave, one fabrication technique would be direct machining from metal. At higher frequencies, such as millimeter wave, submillimeter wave and higher, micro-machined silicon that is subsequently coated with an optically thick low loss metal layer via evaporation or electroplating can additionally be used. At the highest frequencies, micro-machining would be a preferred approach. Alternatively, the pillars  208  can be formed by making a mandrel and electroforming, forming a metal surface under high pressure with a mold, or three-dimensional printing techniques. In alternate embodiments, any suitable pillar fabrication technique can be used depending on the required feature size and subsequent tolerance requirements. 
         [0043]    The aspects of the exemplary embodiments provide a photonic choke joint structure for waveguides. The photonic choke joint structure of the exemplary embodiments suppresses power leakage at the waveguide joint while reducing the joint&#39;s mechanical stress. The optimal designs, which include both Cartesian and Archimedean tiling of pillars structures, exhibit very low loss and have broadband responses that cover the full square waveguide band up to approximately 2f c . 
         [0044]    The aspects of the exemplary embodiments have several commercial applications and the waveguide structure exemplary herein can be used as a thermal break for telecommunication equipment and instruments. The aspects of the exemplary embodiments can also be used for non-destructive testing for thin film materials. Additionally, the aspects of the exemplary embodiments can be used in waveguide switches, phase shifters and rotating feed networks, since these applications require reliable and low-loss rotatable joints. The leakage due to the finite gap at the waveguide joint can be suppressed. The measured power leakage through the waveguide structure of the exemplary embodiments is typically less than 3% in the operating bandwidth. 
         [0045]    The aspects of the exemplary embodiments provide a four-fold and eight-fold symmetry photonic choke structure as a dual-polarization waveguide interface that is scalable, can be used in various waveguide standards and provides several advantages over the existing arts. First, it can be used to provide a thermal break for a waveguide interface. In addition, the spacing between the two flanges of the waveguide PCJ does not significantly affect the waveguide response, as long as the spacing is controlled below a certain value. The waveguide structure of the exemplary embodiments can also preserve the symmetry of the dual-polarized waveguide response. The waveguide structure of the exemplary embodiments can also be used as a housing for planar circuits that enhance the functionality of the waveguide. Examples of waveguide applications that incorporate planar circuits include, for example, filters and dual-polarized antenna feeds. 
         [0046]    Thus, while there have been shown, described and pointed out, fundamental novel features of the invention as applied to the exemplary embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. Moreover, it is expressly intended that all combinations of those elements and/or method steps, which perform substantially the same function in substantially the same way to achieve the same results, are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any exemplary form or embodiment of the invention may be incorporated in any other exemplary or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.