Abstract:
A high bandwidth, low signal error, compact waveguide includes a conductive body including a waveguide input portion and a plurality of waveguide output portions disposed coplanar with the input waveguide portion. The waveguide further includes a common junction joining the input waveguide portion and the plurality of output waveguide portions. A septum is disposed proximate the common junction collinear with a centerline of the input waveguide portion. The waveguide further includes a plurality of iris elements disposed proximate the common junction transverse to the centerline of the input waveguide portion. The septum and the plurality of iris elements changes an impedance of the common junction to match the impedance across the entire waveguide bandwidth.

Description:
RIGHTS OF THE GOVERNMENT 
     The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates generally to RF power distribution apparatus, and specifically to combiners or dividers in radio frequency (RF) systems for radar and communication applications. 
     BACKGROUND OF THE INVENTION 
     Radio frequency (RF) and microwave circuits and systems typically require power distribution networks to divide an RF input signal at a single input into N quantity RF output signals at N outputs, where N may be defined as any regular number of powers two (N=2, 4, 8, 16, 32, . . . ). Likewise, the power distribution networks can also be used to combine N quantity RF input signals at N inputs into a single RF output signal at a single output. For antenna arrays, the RF power distribution network size is constrained by the antenna feed and power handling requirements. 
     RF rectangular waveguide technology can be used to implement the power distribution networks due to inherent advantages in power handling capacity and signal integrity. RF rectangular waveguides have the benefit of very low power loss at high frequencies. Unfortunately, the existing art of RF waveguide power distribution devices have very limited frequency bandwidth, generate unacceptable amplitude and phase errors, and can be too large for many aerospace applications. 
     Therefore, a need exits for a new waveguide RF power distribution technology that can provide wide RF bandwidth operation with low amplitude errors and phase errors in a compact structure for a two way and a four way power combiner/divider. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the foregoing problems and other shortcomings, drawbacks, and challenges of accommodating relatively high operational bandwidths, with low signal error, in a compact waveguide footprint. While the invention will be described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. To the contrary, this invention includes all alternatives, modifications, and equivalents as may be included within the spirit and scope of the present invention. 
     According to one embodiment of the present invention, a high bandwidth, low signal error, compact waveguide is provided. The waveguide includes a conductive body including a waveguide input portion and a plurality of waveguide output portions disposed coplanar with the input waveguide portion. The waveguide further includes a common junction joining the input waveguide portion and the plurality of output waveguide portions. A septum is disposed proximate the common junction collinear with a centerline of the input waveguide portion. The waveguide further includes a plurality of iris elements disposed proximate the common junction transverse to the centerline of the input waveguide portion. The septum and the plurality of iris elements changes an impedance of the common junction to match the impedance across the entire waveguide bandwidth. 
     Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be leaned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention. 
         FIG. 1  is a perspective illustration of a folded Y-junction two way power combiner/divider in accordance with an embodiment of the disclosed invention. 
         FIG. 2  is a top cutaway illustration of a folded Y-junction two way power combiner/divider in accordance with an embodiment of the disclosed invention. 
         FIG. 3  is a perspective illustration of an example compact, H-plane T-junction two way (N=2) power combiner/divider in accordance with an embodiment of the disclosed invention. 
         FIG. 4  is a top cutaway illustration of an example compact, H-plane T-junction two way (N=2) power combiner/divider in accordance with an embodiment of the disclosed invention. 
         FIG. 5  is a perspective illustration of an example compact four way (N=4) power combiner/divider in accordance with an embodiment of the disclosed invention. 
         FIG. 6  is a top cutaway illustration of an example compact four way (N=4) power combiner/divider in accordance with an embodiment of the disclosed invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the sequence of operations as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes of various illustrated components, will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others to facilitate visualization and clear understanding. In particular, thin features may be thickened, for example, for clarity or illustration. 
     DETAILED DESCRIPTION OF THE INVENTION 
     As a preliminary matter, embodiments of the disclosed invention may operate in either a power combining or dividing mode of a waveguide distribution network. Thus, in one exemplary embodiment, the distribution network, or waveguide combiner/divider, is considered to be a passive reciprocal structure. A reciprocal network may be defined as one in which the power losses are the same between any two ports regardless of the direction of propagation. Therefore, for sake of clarity in discussing the embodiments that follow, the examples disclosed herein are generally discussed from a power divider perspective. Stated another way, examples discussed herein are generally with reference to a single signal that is distributed as described herein from an input port (or waveguide portions) a to two or more outputs (N≧2) (waveguide portions). Nevertheless, the use of such language to identify the components of the device is not intended to limit the scope of the description of the invention to only a power divider type device. It will be understood by one of ordinary skill in the art that the same distribution network may be used in a power combiner context, with element nomenclature reconfigured to fit the respective use. 
     With reference to  FIG. 1 , in an example embodiment, a compact in-line two way (N=2) power combiner/divider is realized in a waveguide structure. The waveguide  10  comprises a single waveguide input  12  and a first and second waveguide output,  14  and  16 , respectively. The waveguide input  12  and a first and second waveguide output,  14  and  16 , may be referred to as “waveguide portions” of the larger waveguide  10 . Additionally, the outer shell of the waveguide  10  may described as having a conductive body  11 . The waveguide input  12  and two waveguide outputs  14  and  16  are connected via a common junction  18 . The two waveguide outputs  14  and  16  are on opposite sides of the common junction  18  and parallel with the centerline  20  of the waveguide  10 . The resulting layout and geometry, as illustrated in this embodiment, is a folded Y-junction power divider; where a single signal incident into waveguide input  12  is split equally into two signals at two waveguide outputs  14  and  16 . 
     In the example embodiment, the waveguide input  12  and waveguide outputs  14  and  16  (as well as other inputs and outputs as will be described in additional embodiments) can be sized for dominant mode signal transmission where the width and height of the waveguide can have a dimension (width “a” and height “b”) where “a” is greater than λL/2 and less than λH, where λL is the free-space wavelength at the lowest operational frequency and λH is the free-space wavelength at the highest operational frequency. Waveguide height “b” can be selected to be less than “a” to avoid a degenerate or higher order mode of signal transmission. For example, the lower frequency limit can establish a lower limit to the waveguide size as it is the “waveguide cutoff” where signal transmission effectively ceases. Conventional or standard rectangular waveguide interior has a 2:1 aspect ratio for most cases; though exceptions exist for particular sets of operational frequency bands such as WR-90 waveguide (WR is defined as waveguide rectangular and 90 designates the waveguide standard size). 
     In the illustrated embodiments of  FIG. 1 , and in additional embodiments that follow, the waveguide  10  is implemented in WR-90 waveguide, though other embodiments may be optimized for additional applications. The waveguide  10  may be constructed by machining the waveguide channels and impedance matching features in a block of aluminum. Aluminum offers high conductivity and overall good performance to weight metrics. Aluminum can be a good substrate for high speed machining and can also be dimensionally stable. It is possible to use any highly conductive material, such as copper, brass, and silver, to construct the device. For example, the waveguide device can be formed in a copper substrate. Copper can offers high performance and, in the case of manufacturing by electroforming, can offer high performance and precision at the expense of higher cost and manufacturing time. 
     With reference to  FIG. 2  shunt inductive irises consisting of a first element  30 , second element  32 , and third element  34 , are placed symmetrically about the centerline  20 . The first element  30 , second element  32 , and third element  34  have corresponding first distance  38  and first width  44 , second distance  40  and second width  46 , and third distance  42  and third width  48 , respectively. The first element  30 , second element  32 , and third element  34  result in a shunt inductive reactance placed across the common junction  18 . 
     In this exemplary embodiment, the waveguide  10  is divided at the common junction  18  by an inductive H-plane septum  50  that serves to partially match the impedance of the common junction  18  to that of the waveguide input  12  and waveguide outputs  14  and  16 ; as well equalize the power division between the first waveguide output  14  and second waveguide output  16 . The septum  50  extends the full height of the waveguide H-plane folded Y-junction. The septum  50  is placed offset from the common junction  18  end of the waveguide input by cumulative first distance  38 , second distance  40 , and third distance  42 . The septum  50  has a septum thickness  52  equal to the standard or conventional waveguide wall thickness  54 . 
     In the exemplary embodiment, it should be noted that the simultaneous application of the inductive first element  30 , second element  32 , third element  34 , and septum  50  at the common junction  18  produces beneficial unexpected results (as will be demonstrated in greater detail, below). The septum  50  and elements  30 ,  32 , and  34  work in concert to match the impedance of the structure across the entire bandwidth of the rectangular waveguide  10 . The respective dimensions and relative placement of elements  30 ,  32 , and  34 , as well as the septum  50 , result in very low levels of reflected power from an input signal across the entire operational frequency band of the rectangular waveguide  10 ; serving also to minimize amplitude and phase errors in a compact structure for a two way power combiner/divider. 
     As further illustrated in  FIG. 2 , impedance matching elements  30 ,  32 , and  34 , as well as the septum  50 , include first through seventh fillets,  56 ,  58 ,  60 ,  62 ,  64 ,  66 ,  68 , respectively, along corners of the waveguide walls. Fillets,  56 ,  58 ,  60 ,  62 ,  64 ,  66 ,  68  may be employed on both interior and exterior corners of impedance matching structures and at intersecting walls of the conducting body  11 . Rectangular waveguides exhibit very low loss and high power capacity over other RF and microwave transmission. For high power systems, it is important to further suppress the peak electric field to avoid dielectric breakdown. The smooth corners allow for maximum power transmission through the waveguide device by softening the discontinuities in the waveguide walls; thereby minimizing associated charge buildup and standing waves which cause breakdown. 
     The following examples illustrate particular properties and advantages of some of the embodiments of the present invention. Furthermore, these are examples of reduction to practice of the present invention and confirmation that the principles described in the present invention are therefore valid but should not be construed as in any way limiting the scope of the invention. 
     The dimensions noted in Table 1 have been found to produce acceptable results when applied to the disclosed waveguide  10 . All values noted in Table 1 are proportions, with dimensions normalized to the center frequency of the waveguide, λ center . 
     
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Name 
                 Normalized Values 
               
               
                   
                   
               
             
             
               
                   
                 a 
                 0.762 
               
               
                   
                 b 
                 0.338667 
               
               
                   
                 38 
                 0.010583 
               
               
                   
                 40 
                 0.356293 
               
               
                   
                 42 
                 0.033867 
               
               
                   
                 44 
                 0.61193 
               
               
                   
                 46 
                 1.566333 
               
               
                   
                 48 
                 1.314124 
               
               
                   
                 52 
                 0.042333 
               
               
                   
                 56 
                 0.01905 
               
               
                   
                 58 
                 0.02523 
               
               
                   
                 60 
                 0.009617 
               
               
                   
                 62 
                 0.016933 
               
               
                   
                 64 
                 0.071967 
               
               
                   
                 66 
                 0.005699 
               
               
                   
                 68 
                 0.025523 
               
               
                   
                   
               
             
          
         
       
     
     The experimental performance of the illustrative embodiment of the waveguide  10  exhibits a minimum return loss across the waveguide  10  operational frequency band (8.2-12.4 GHz) of approximately −22 dB. That is, the return loss exceeds −20 dB over 100% of the rectangular waveguide operation frequency band. The maximum difference in the coupling to each of waveguide outputs  14  and  16  across the entire frequency band (8.2-12.4 GHz) is approximately 0.05 dB. An ideal two-way power divider would have a coupling of −3 dB to each of waveguide output  14  and  16 . The worst-case coupling across the entire frequency band is approximately −3.05 dB. 
     Turning attention to  FIG. 3 ., in accordance with another embodiment of the disclosed invention, a compact two way (N=2) power combiner/divider T-junction waveguide  10   a  is illustrated. The exemplary waveguide  10   a  includes a single waveguide input  12   a  and first and second waveguide outputs  14   a  and  16   a , respectively. The input waveguide  12   a  and two output waveguides  14   a  and  16   a  are connected via a common junction  18 . The two output waveguides  14   a  and  16   a  are disposed on opposite sides of the common junction  18  and perpendicular with the centerline  20  of the waveguide  10   a . The resulting layout and geometry, as illustrated in the embodiment, is a standard H-plane T-junction power divider; where a single signal incident into waveguide input  12   a  is split equally into two signals at waveguide outputs  14   a  and  16   a.    
     With reference to  FIG. 4 , shunt inductive irises consisting of a first element  30   a , second element  32   a , third element  34   a , and fourth element  35   a , are placed symmetrically about the centerline  20 . The elements  30   a ,  32   a ,  34   a , and  35   a  are comprised of corresponding first distance  38 , second distance  40   a , third distance  42   a , and fourth distance  43   a  and corresponding first width  44   a , second width  46   a , third width  48   a , and fourth width  49   a , respectively. The elements  30   a ,  32   a ,  34   a , and  35   a  result in a shunt inductive reactance placed across the common junction  18  that is proportional to the opening size. 
     In this exemplary embodiment, the waveguide  10   a  is divided at the common junction  18  by an inductive H-plane septum  50  that serves to partially match the impedance of the common junction  18  to that of the waveguide input  12   a  and waveguide outputs  14   a  and  16   a ; as well equalize the power division between the first waveguide output  14   a  and second waveguide output  16   a . The septum  50  extends the full height of the waveguide H-plane folded Y-junction. The septum  50  protrudes into the common junction  18  of the waveguide input  12  by a septum length  51   a  with a septum thickness  52   a  less than the standard or conventional waveguide wall thickness  54   a    
     In the exemplary embodiment, it should be noted that the simultaneous application of the inductive first element  30   a , second element  32   a , third element  34   a , fourth element  35   a , and septum  50  at the common junction  18  produces beneficial unexpected results (as will be demonstrated in greater detail, below). The septum  50  and elements  30   a ,  32   a ,  34   a , and  35   a  work in concert to match the impedance of the structure across the entire bandwidth of the rectangular waveguide  10   a . The respective dimensions and relative placement of elements  30   a ,  32   a ,  34   a , and  35   a , as well as the septum  50 , result in very low levels of reflected power from an input signal across the entire operational frequency band of the rectangular waveguide  10   a ; serving also to minimize amplitude and phase errors in a compact structure for a two way power combiner/divider. 
     As further illustrated in  FIG. 4 , impedance matching elements  30   a ,  32   a ,  34   a  and  35   a , as well as the septum  50 , include first through seventh fillets,  56   a ,  58   a ,  60   a ,  62   a ,  64   a ,  66   a ,  68   a , respectively, along corners of the waveguide walls. Fillets,  56   a ,  58   a ,  60   a ,  62   a ,  64   a ,  66   a ,  68   a  may be employed on both interior and exterior corners of impedance matching structures and at intersecting walls of the conducting body  11 . Generally, rectangular waveguides exhibit very low loss and high power capacity over other RF and microwave transmission. For high power systems, it is important to further suppress the peak electric field to avoid dielectric breakdown. The smooth corners allow for maximum power transmission through the waveguide device by softening the discontinuities in the waveguide walls; thereby minimizing associated charge buildup and standing waves which cause breakdown. 
     The dimensions noted in Table 2 have been found to produce acceptable results when applied to the disclosed waveguide  10   a . All values noted in Table 2 are proportions, with dimensions normalized to the center frequency of the waveguide, λ center . 
     
       
         
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Name 
                 Normalized Values 
               
               
                   
                   
               
             
             
               
                   
                 b 
                 0.338666667 
               
               
                   
                 a 
                 0.762 
               
               
                   
                 38a 
                 0.042983388 
               
               
                   
                 40a 
                 0.057819449 
               
               
                   
                 42a 
                 0.166524168 
               
               
                   
                 43a 
                 0.008966959 
               
               
                   
                 44a 
                 1.163467619 
               
               
                   
                 46a 
                 1.229195056 
               
               
                   
                 48a 
                 1.130172981 
               
               
                   
                 49a 
                 0.677769406 
               
               
                   
                 51a 
                 0.340314372 
               
               
                   
                 52a 
                 0.008466667 
               
               
                   
                 56a 
                 0.001671131 
               
               
                   
                 58a 
                 0.042333333 
               
               
                   
                 60a 
                 0.002780448 
               
               
                   
                 62a 
                 0.018684269 
               
               
                   
                 64a 
                 0.008466667 
               
               
                   
                 66a 
                 0.0254 
               
               
                   
                 68a 
                 0.030939035 
               
               
                   
                   
               
             
          
         
       
     
     The experimental performance of the illustrative embodiment of the waveguide  10   a  exhibits a minimum return loss across the waveguide  10   a  operational frequency band (8.2-12.4 GHz) of approximately −25 dB. That is, the return loss exceeds −20 dB over 100% of the rectangular waveguide  10   a  operation frequency band. The maximum difference in the coupling to the first waveguide output  14   a  and second waveguide output  16   a  across the entire frequency band (8.2-12.4 GHz) is approximately 0.04 dB. An ideal two-way power divider would have a coupling of −3 dB to each of output waveguides  14   a  and  16   a . In the example embodiment, the worst-case coupling across the entire frequency band is approximately −3.04 dB. 
     With reference to  FIG. 5 , in an example embodiment, a compact four way (N=4) power combiner/divider is realized in a combination waveguide  10   b  folded Y- and T-junction structure. The example waveguide  10   b  comprises a single waveguide input  12   b  and first through fourth waveguide outputs  14   b - 17   b , respectively. The waveguide input  12   b , and waveguide outputs  14   b - 17   b , may be referred to as “waveguide portions” of the larger waveguide  10   b . Additionally, the outer shell of the waveguide  10   b  may be described as having a conductive body  11 . The single waveguide input  12   b  and four output waveguides  14   b - 17   b  are connected via first through third common junctions  18   b - 18   d , respectively. The common junctions  18   c  and  18   d  include the impedance matching features specified in  FIG. 1-2 . The resulting layout and geometry, as illustrated in the embodiment of  FIG. 5 , is a compact H-plane 1:4 power divider; where a single signal incident into waveguide input  12   b  is split equally into four signals at waveguide outputs  14   b - 17   b.    
     With reference to  FIG. 6 , the waveguide  10   b  T-junction wall  80  is offset from the folded Y-junction iris element  82  by length  84 . The waveguide  10   b  arms connecting the H-plane first common junction  18   b  and folded Y third common junction  18   d  include a substantial fillet  86  beginning at the inductive iris first element  30   b  and extending to the onset of the folded Y third common junction  18   d . A similar structure is reflected about the centerline  20 . Shunt inductive irises consisting of first through fourth elements  30   b ,  32   b ,  34   b , and  35   b  are place symmetrically about the centerline  20 . The elements  30   b ,  32   b ,  34   b , and  35   b  are comprised of corresponding first distance  38   b , second distance  40   b , third distance  42   b , and fourth distance  43   b  and corresponding first width  44   b , second width  46   b , third width  48   b , and fourth width  49   b , respectively. The elements  30   b ,  32   b ,  34   b , and  35   b  result in a shunt inductive reactance placed across the waveguide  10   b  common junction  18   b.    
     In the example embodiment, the waveguide  10   b  is divided at the first common junction  18   b  by an inductive H-plane septum  50  that serves to partially match the impedance of the first common junction  18   b  to that of the waveguide input  12   b  and output waveguides  14   b - 17   b ; as well equalize the power division between the four waveguide outputs  14   b - 17   b . The septum  50  extends the full height of the waveguide H-plane T-junction. The septum  50  protrudes into the first common junction  18   b  of the input waveguide by septum length  51   b  with a septum thickness  52   b  less than the standard or conventional waveguide wall thickness  54   b.    
     In the exemplary embodiment, it should be noted that the simultaneous application of the inductive first element  30   b , second element  32   b , third element  34   b , fourth element  35   b , and septum  50  at the first common junction  18   b  produce beneficial unexpected results. The septum  50  and elements  30   b ,  32   b ,  34   b , and  35   b  work in concert to match the impedance of the structure across the entire bandwidth of the rectangular waveguide  10 . The respective dimensions and relative placement of elements  30   b ,  32   b ,  34   b , and  35   b , as well as the septum  50 , result in very low levels of reflected power from an input signal across the entire operational frequency band of the rectangular waveguide  10   b ; serving also to minimize amplitude and phase errors in a compact structure for a 4 way power combiner/divider. 
     As illustrated in  FIG. 6 , impedance matching features  30   b ,  32   b ,  34   b , and  35   b  include first through seventh fillets  56   b ,  58   b ,  60   b ,  62   b ,  64   b ,  56   b , and  58   b  along corners of impedance matching structures and along intersecting walls of the conductive body  11 . Rectangular waveguides exhibit very low loss and high power capacity over other RF and microwave transmission. For high power systems, it is important to further suppress the peak electric field to avoid dielectric breakdown. The smooth corners allow for maximum power transmission through the waveguide  10   b  device by softening the discontinuities in the waveguide  10   b  walls; thereby minimizing associated charge buildup and standing waves which cause breakdown. 
     The dimensions noted in Table 3 have been found to produce acceptable results when applied to the disclosed waveguide  10   b . All values noted in Table 3 are proportions, with dimensions normalized to the center frequency of the waveguide, λ center . 
     
       
         
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Name 
                 Normalized Values 
               
               
                   
                   
               
             
             
               
                   
                 b 
                 0.338666667 
               
               
                   
                 a 
                 0.762 
               
               
                   
                 38b 
                 0.010822063 
               
               
                   
                 40b 
                 0.117119906 
               
               
                   
                 42b 
                 0.078404096 
               
               
                   
                 43b 
                 0.051318922 
               
               
                   
                 44b 
                 0.646261897 
               
               
                   
                 46b 
                 1.064025644 
               
               
                   
                 48b 
                 1.059366616 
               
               
                   
                 49b 
                 1.086216117 
               
               
                   
                 51b 
                 0.373444747 
               
               
                   
                 52b 
                 0.008466667 
               
               
                   
                 54b 
                 0.042333333 
               
               
                   
                 56b 
                 0.001671131 
               
               
                   
                 58b 
                 0.067359803 
               
               
                   
                 60b 
                 0.002780448 
               
               
                   
                 62b 
                 0.018684269 
               
               
                   
                 64b 
                 0.008466667 
               
               
                   
                 66b 
                 0.0254 
               
               
                   
                 68b 
                 0.005974251 
               
               
                   
                 84 
                 0.474142848 
               
               
                   
                 86 
                 0.858521639 
               
               
                   
                   
               
             
          
         
       
     
     The experimental performance of the illustrative embodiment of the waveguide  10   b  exhibits a minimum return loss across the waveguide operational frequency band (8.2-12.4 GHz) of approximately −22 dB. That is, the return loss exceeds −20 dB over 100% of the rectangular waveguide operation frequency band. The maximum difference in the coupling to different output waveguides across the entire frequency band (8.2-12.4 GHz) is approximately 0.05 dB. An ideal two-way power divider would have a coupling of −3 dB to each output waveguide. In the example embodiment, the worst-case coupling across the entire frequency band is approximately −3.05 dB. 
     Each of the embodiments described above may be used in an antenna array, such as antenna arrays for X band monopulse radar or Ku and Ka band satellite communications applications. It is noted that a combination of two-way folded-Y junction waveguide power can be used to form higher order (N=8, 16, 32 . . . ) power combiner/divider structures. Moreover, the antenna array can be configured to be mechanically pointed, rotating about one or more axis of rotation. Thus, the antenna array can be a non-electrically scanning array for aerospace applications. 
     In summary, a compact waveguide power divider is comprised of an input waveguide that terminates at a common junction with two output waveguides, on opposite sides of the junction and collinear with the centerline of input waveguide. A combination of symmetrical irises with a bifurcating inductive septum serves to impedance match the structure across the entire operational frequency band of the rectangular waveguide. The embodiment may operate in either a power combiner or divider mode of operation. As one skilled in the art will appreciate, the mechanism of the present invention may be suitably configured in any of several ways. It should be understood that the mechanism described herein with reference to the figures is but one exemplary embodiment of the invention and is not intended to limit the scope of the invention as described above. 
     While the present invention has been illustrated by a description of one or more embodiments thereof and while these embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept.