Abstract:
A waveguide having a non-conductive material with a high permeability (μ, μ r  for relative permeability) and/or a high permittivity (∈, ∈ r  for relative permittivity) positioned within a housing. When compared to a hollow waveguide, the waveguide of this invention, reduces waveguide dimensions by 
             ∝         1       μ   r     *     ɛ   r           .           
The waveguide of this invention further includes ridges which further reduce the size and increases the usable frequency bandwidth.

Description:
GOVERNMENT RIGHTS 
     This invention was made with government support under Contract No. DE-AC05-00OR22725 awarded by the U.S. Department of Energy. The government has certain rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     This invention is directed to a ridge waveguide having a dispersive filling material with a high permeability (μ, μ r  for relative permeability) and/or a high permittivity (∈, ∈ r  for relative permittivity) material to reduce waveguide dimensions. 
     BACKGROUND OF THE INVENTION 
     A waveguide is a structure that guides waves, such as electromagnetic waves or sound waves. Commonly known waveguides include hollow metal tubes which allow high frequency radio waves to “bounce” off walls of the hollow metal tubes to propagate down the waveguide. Commonly known waveguides have cross sections in rectangular, circular, or elliptical shapes. These common waveguides generally have a limited bandwidth, usually around 30% of a center of an operating frequency range. 
     Electromagnetic and sound waves in open space propagate in all directions as a spherical wave. When propagating in open space, the waves lose power proportional to the square of the distance from a source. When propagating in a waveguide, a wave has very little power loss, generally a wall conductor loss and a dispersive medium loss which are generally negligible. Ideally, the dimensions of a waveguide are selected so that, for a particular frequency(s), the wave is not cutoff and higher-order modes are not excited to minimize power loss. 
     One disadvantage of hollow metallic waveguides is the size of the waveguide. In general, the width of the waveguide needs to be of the same order of magnitude as the free-space wavelength of the guided wave. Thus, waveguides for radio and microwave transmission can be relatively large and unwieldy, especially when designed for frequencies in several hundreds or thousands of MHz range. 
     Accordingly, there is a need for an improved waveguide having smaller dimensions than an equivalent hollow metal waveguide at a particular operating frequency. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to radio frequency components that are building blocks of various radio frequency circuits and systems. The components are built with waveguides which include a low loss dispersive material with a high-permeability and/or a high-permittivity. In one embodiment, the dispersive material comprises a dielectric material with a permittivity that is higher than the permittivity of air and permeability that is approximately equal to the permeability of air. The waveguides may further include a ridge for a broad frequency bandwidth and a further reduction in a dimension of the waveguide. 
     One advantage of the present invention is a reduction in component size in comparison to a similar prior art component for RF frequencies from approximately 100 to 1,000,000 MHz. Additionally, the present invention enables relatively high power capability and easier manufacturing and assembly in comparison to prior art components. 
     Filling a waveguide with a non-conductive material with a relative permeability greater than one and/or a relative permittivity greater than one can reduce waveguide dimensions over known waveguides by 
               ∝       1       μ   r     *     ɛ   r             ,         
for the same frequencies of operation. Introducing ridge(s) can further reduce the waveguide dimensions and increase the usable frequency bandwidth.
 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects and features of this invention will be better understood from the following detailed description taken in conjunction with the drawings, wherein: 
         FIG. 1  is a cross-sectional view of a waveguide according to one embodiment of this invention; 
         FIG. 2  is a cross-sectional side view of a waveguide according to another embodiment of this invention; 
         FIG. 3  is a cross-sectional view of a know waveguide showing vectors of an electric field; 
         FIG. 4  is the cross-sectional view of the waveguide of  FIG. 1  with vectors showing an electric field; 
         FIG. 5  is the cross-sectional view of the waveguide of  FIG. 2  with vectors showing an electric field; 
         FIG. 6   a  is a side view of a waveguide to coaxial transformer according to one embodiment of this invention; 
         FIG. 6   b  is a top view of the waveguide to coaxial transformer of  FIG. 6   a;    
         FIG. 6   c  is a computer simulated transmission response of a matching section of the waveguide to coaxial transformer of  FIG. 6   a;    
         FIG. 6   d  is a computer simulation of a field distribution in the waveguide to coaxial transformer of  FIG. 6   a;    
         FIG. 7   a  is a side view of a hybrid coupler according to one embodiment of this invention; 
         FIG. 7   b  is a top view of the hybrid coupler of  FIG. 7   a;    
         FIG. 7   c  is a computer simulation of a field distribution in the hybrid coupler of  FIG. 7   a;    
         FIG. 8   a  is a side view of a matched load termination according to one embodiment of this invention; 
         FIG. 8   b  is a top view of the matched load termination of  FIG. 8   a;    
         FIG. 8   c  is a computer simulation a field distribution in the matched load termination of  FIG. 8   a;    
         FIG. 9   a  is a side view of a miter bend according to one embodiment of this invention; 
         FIG. 9   b  is a top view of the miter bend of  FIG. 9   a;    
         FIG. 9   c  is a computer simulation of a field distribution in the miter bend of  FIG. 9   a;    
         FIG. 10   a  is a side view of a loaded phase shifter according to one embodiment of this invention; 
         FIG. 10   b  is a top view of the loaded phase shifter of  FIG. 10   a;    
         FIG. 10   c  is a computer simulation of a field distribution in the loaded phase shifter of  FIG. 10   a;    
         FIG. 11  is a block diagram of a vector modulator system according to one embodiment of this invention; and 
         FIG. 12  is the vector modulator system of  FIG. 11 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Waveguides are generally used in high power RF (radio frequency) or microwave transmission components and systems.  FIG. 1  shows a cross-sectional view of a single-ridge waveguide  10  according to one embodiment of this invention. The single-ridge waveguide  10  includes a housing  12  and a ridge  14 . In a preferred embodiment, the housing  12  is a metallic material for example, but not limited to, copper. 
     In a preferred embodiment, a volume  16  of the single-ridge waveguide  10  is filled with a non-conductive filling material  18  having a high permeability (μ, μ r  for relative permeability) and/or a high permittivity (∈, ∈ r  for relative permittivity). Filling the single-ridge waveguide  10  with the non-conductive material  18  can reduce waveguide dimensions by 
             ∝         1       μ   r     *     ɛ   r           .           
The non-conductive material can comprise, for example, alumina ceramic, Teflon, or any non-conductive material with a relative permeability greater than one and/or a relative permittivity greater than one.
 
       FIG. 2  shows a cross-sectional view of a double-ridge waveguide  20  according to one embodiment of this invention. The double-ridge waveguide  20  includes a housing  22  and a pair of oppositely positioned ridges  24 . In a preferred embodiment, a volume  26  of the double-ridge waveguide  10  is filled with a non-conductive material  28  having a high permeability (μ, μ r  for relative permeability) and/or a high permittivity (∈, ∈ r  for relative permittivity). Filling the double-ridge waveguide  20  with the non-conductive material  28  can reduce waveguide dimensions by 
     
       
         
           
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     In  FIGS. 1 and 2 , the housings  12 ,  22  are rectangular-shaped with a pair of broad walls and a pair of narrow walls. However, the housing of this invention can be any shape including, but not limited to, a circular shape or an elliptical shape. 
     In comparison to known waveguides without ridges, the ridges  14 ,  24  reduce the transverse dimensions of the waveguides  10 ,  20 . The ridges  14 ,  24  also increase an operational frequency range of the waveguide  10 ,  20 , in comparison to a similar waveguide without ridges. The operational frequency range of the ridged waveguide  10 ,  20  can be increased by 100% or more depending on ridge dimensions. 
     The addition of ridges  14 ,  20 , however, may increase the microwave loss and lower peak power handling capability.  FIG. 3  shows electric field (E-field) vectors  32  in a prior art waveguide  30 .  FIG. 4  shows electric field (E-field) vectors  42  in a single-ridge waveguide  40  and  FIG. 5  shows electric field (E-field) vectors  52  in a double-ridge waveguide  50 . The density of the electric field lines show the strength of the E-field and can also show that the voltage is integrated along a vector path V=∫E·dl. As shown in the figures, the E-field vectors  32 ,  42 ,  52  have a sinusoidal strength distribution in a horizontal direction. The highest voltage peaks appear between the two broad walls at the center. A voltage rating and a power rating of both the single-ridge waveguide  40  and the double-ridge waveguide  50  is less than the prior art waveguide  30  due to decreased gap distance at the voltage peak. 
     Filling the volume  16 ,  26  of the ridged waveguide  10 ,  20  completely with the non-conductive material  18 ,  28 , reduces a wavelength by 1/√{square root over (∈ r μ r )} (a ratio of the wavelength in free space (air or a vacuum) to the wavelength in the filling material is ≅1/√{square root over (∈ rμ   r )}). As a result, dimensions of the waveguide structure can be reduced by a similar amount. For reference, the permittivity of a vacuum is ∈ r =1.0 and thin air is approximately equal to 1.0. Non-conductive materials can have varying permittivity, for example: Teflon ∈ r =2.1, glass ∈ r =4, alumina ceramic ∈ r =10, water ∈ r =10−90, and some ceramic materials can have ∈ r  greater than 10 and even greater than 1,000. 
     With nonmagnetic dielectric materials, such as plastic or ceramic materials, the relative permeability is μ r =1. Thus, filing the waveguide with a nonmagnetic material reduces the waveguide dimensions by =1/√{square root over (∈ r )}. This relationship is more realistic for metallic hollow waveguides with an operating frequency in the hundreds of megahertz (MHz) or higher due to high magnetic loss of most magnetic materials. 
     Known waveguides and devices are often filled with compressed air or gas, having a ∈ r =1.0, to increase the power ratings. Some very high power applications, high vacuum (means actually low vacuum), provide a very high voltage rating, however, such waveguides are bulky and generally very expensive. Filling the volume  16 ,  26  with the non-conductive material  18 ,  28  also increases a power rating of the waveguide  10 ,  20 , without the high expense of known waveguides. 
     Using the properties discussed above, multiple radio frequency (RF)/microwave components can be designed. The following components are designed for an example operating frequency of approximately 400 MHz. The components can be scaled to any operating frequency. The components can also be modified for different non-conductive materials with different permeability and different permittivity. 
       FIGS. 6   a  and  6   b  show a waveguide to coaxial transformer  60  according to one embodiment of this invention. The waveguide to coaxial transformer  60  transforms RF energy in a transverse electric (TE) mode in the waveguide to a coaxial output in a transverse electric and magnetic mode (TEM). Similarly, the waveguide to coaxial transformer  60  can operate in the opposite direction from the coaxial portion to the waveguide. An example operating frequency of 400 MHz has been selected for this embodiment. The waveguide to coaxial transformer  60  comprises a waveguide  61  having a pair of ridges  62  and filled with a high dielectric constant material  63  that is joined at a matching section  64  to a coaxial connection section  65 . The coaxial connection  65  preferably extends generally perpendicular from the waveguide  61 . The coaxial section  65  in this embodiment comprises two conductors, a cylindrical outside conductor and a concentric inside conductor. The two conductors are separated by a cylindrical insulator. In a preferred embodiment the two conductors can comprise copper. The cylindrical insulator can comprise, for example but not limited to, alumina ceramic, Teflon, or any non-conductive material with a relative permeability greater than one and/or a relative permittivity greater than one.  FIG. 6   c  shows a computer simulated transmission response of an alumina matching section and  FIG. 6   d  shows a computer simulation of a field distribution in the waveguide to coaxial transformer  60 . 
       FIGS. 7   a  and  7   b  show a hybrid coupler  70  according to one embodiment of this invention. An example operating frequency of 400 MHz has been selected for this embodiment. The hybrid coupler  70  comprises a first waveguide section  71  joined to a second waveguide section  72  by a coupling channel  73 . The first waveguide section comprises a pair of ridges  74  and is filled with a first non-conductive material  75 . The second waveguide section comprises a pair of ridges  76  and is filled with a second non-conductive material  77  which may or may not be the same as first non-conductive material  75 .  FIG. 7   c  shows a computer simulation of the hybrid coupler  70 . 
       FIGS. 8   a  and  8   b  show a matched load termination  80  according to one embodiment of this invention. An example operating frequency of 400 MHz has been selected for this embodiment. The matched load termination includes a waveguide  81  having a pair of ridges  82  and is filled with a non-conductive material  83 . A RF absorbing material wedge  84  is placed at a terminating edge  85  of the waveguide  81 . An RF wave propagates through the RF absorbing material wedge  84  and is converted into heat.  FIG. 8   c  shows a computer simulation of a field distribution in the matched load termination  80 . 
       FIGS. 9   a  and  9   b  show a miter bend  90  according to one embodiment of this invention. An example operating frequency of 400 MHz has been selected for this embodiment.  FIG. 9   c  shows a computer simulation of the miter bend  90 . 
       FIGS. 10   a  and  10   b  show a Ferrite loaded phase shifter  100  according to one embodiment of this invention. An example operating frequency of 400 MHz has been selected for this embodiment. The Ferrite loaded phase shifter  100  comprises a waveguide  102  with a pair of ridges  104 . A Ferrite insert  106  is positioned inside on an edge of the waveguide  102 . The Ferrite insert  106  varies the external magnetic bias field which changes a phase of the RF wave propagating through the waveguide  102 . In one embodiment, the Ferrite insert  106  can be yttrium iron garnet (YIG). A  FIG. 10   c  shows a computer simulation of the Ferrite loaded phase shifter  100 . In an alternative embodiment, the Ferrite loaded phase shifter includes a pair of ferrite inserts, each ferrite insert is positioned on opposite sides of the waveguide. 
     The proposed components discussed above can be integrated to construct various systems for various applications. For example,  FIG. 11  shows a block diagram of a vector modulator system  110  which can be constructed from the components discussed above. The vector modulator system  110  includes an input  112  connected to a first hybrid coupler  114  connected to a pair of phase shifters  116 ,  118 , outputs of the phase shifters  116 ,  118  connect to a second hybrid coupler  120  connected to an output  122 . By adjusting the two phases through the phase shifters, φ1 and φ2, the amplitude and the phase of input voltage can be varied at the output voltage as: 
                 V   out     ⁡     (       ϕ   1     ,     ϕ   2       )       =       V   o     ⁢     cos   ⁡     (         ϕ   1     -     ϕ   2       2     )       ⁢     ⅇ     -     j   ⁡     (         ϕ   1     +     ϕ   2       2     )                     FIG. 12  shows the vector modulator system  110  constructed using the components discussed above.
 
     Thus, the invention provides radio frequency (RF) and microwave components which are smaller than known components by ≅1/√{square root over (∈ r μ r )}. 
     It will be appreciated that details of the foregoing embodiments, given for purposes of illustration, are not to be construed as limiting the scope of this invention. Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention, which is defined in the following claims and all equivalents thereto. Further, it is recognized that many embodiments may be conceived that do not achieve all of the advantages of some embodiments, particularly of the preferred embodiments, yet the absence of a particular advantage shall not be construed to necessarily mean that such an embodiment is outside the scope of the present invention.