Patent Publication Number: US-8525616-B1

Title: Antenna feed network to produce both linear and circular polarizations

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Application Ser. No. 61/169,262 filed Apr. 14, 2009. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FIELD OF THE INVENTION 
     The present invention relates generally to an antenna. More particularly, the invention is directed to an antenna feed network for producing both linear and circular polarizations. 
     BACKGROUND OF THE INVENTION 
     Typically satellite antenna feeds are either circularly polarized or linearly polarized. However, some satellite antennas require a combination of linear and circular polarization. In applications that require both linear and circular polarization, standard feed design no longer meets customer requirements, and a novel configuration is needed to satisfy customer polarization diversity requirements at low risk. 
     Currently, antenna feeds split a received signal into two orthogonal linear components. Each of the orthogonal linear components is further separated based upon two pre-determined frequency bands. Finally, the band requiring circular polarization is created by adding the two linear components 90 degrees out of phase. For example, two conventional methods are described below: 
     In a first method, a signal is split into a horizontal and a vertical polarizations (Hpol and Vpol) using a turnstile junction and a pair of magic-T wave guides. The Hpol and Vpol are passed into the common port of a pair of diplexers, respectively. Two orthogonal linear polarizations are each received at a receive port of each of the diplexers, respectively. In transmission, each of the transmit ports of the diplexers must be summed 90 degrees out of phase to produce the circularly polarized transmit port by letting one polarization pass through one quarter wavelength more of waveguide and adding them using a magic-T. 
     In a second method, a six-port device separates the orthogonal linear components and frequency bands simultaneously. In the six-port configuration, the circularly polarized band, either transmit or receive, passes straight through the six-port device, and a filter is used to remove a pre-determined band from the signal. A polarizer can then be used to obtain dual-polarization circular polarization in the pre-determined band. Four ports on the walls of the 6-port device receive components of the linear polarized frequency band. Each opposite pair of the four ports receives one orthogonal polarization, and each pair is combined using a magic-T. 
     It would be desirable to develop an antenna feed network that provides a compact and lightweight solution to an application requiring the capability of both linear and circular polarization. 
     SUMMARY OF THE INVENTION 
     Concordant and consistent with the present invention, an antenna feed network that provides a compact and lightweight solution to an application requiring the capability of both linear and circular polarization, has surprisingly been discovered. 
     In one embodiment, an antenna feed network comprises: a septum polarizer including a waveguide defining a cavity, wherein a septum is disposed in the cavity to divide the cavity to form a first port and a second port; a diplexer in signal communication with at least one of the first port and the second port of the septum polarizer to route a signal based upon a frequency; and a wave coupler/splitter in signal communication with the diplexer to send and receive signals therebetween, the wave coupler/splitter including a first signal path and a second signal path, wherein the wave coupler/splitter controls a phase shift of a signal transmitted through at least one of the first signal path and the second signal path. 
     In another embodiment, an antenna feed network comprises: a septum polarizer including a waveguide defining a cavity, wherein a septum is disposed in the cavity to divide the cavity to form a first port and a second port; a first diplexer in signal communication with the first port of the septum polarizer to route a signal based upon a frequency; a second diplexer in signal communication with the second port of the septum polarizer to route a signal based upon a frequency; and a wave coupler/splitter in signal communication with the diplexer to send and receive signals therebetween, the wave coupler/splitter including a first signal path and a second signal path, wherein the wave coupler/splitter controls a phase shift of a signal transmitted through at least one of the first signal path and the second signal path. 
     In another embodiment, an antenna feed network comprises: a septum polarizer including a waveguide defining a cavity, wherein a septum is disposed in the cavity to divide the cavity to form a first port and as second port; a first diplexer including a common port in signal communication with the first port of the septum polarizer to route a signal based upon a frequency, wherein first diplexer further includes a first polarizer port having a first pre-determined passband frequency and a second polarizer port having a second pre-determined passband frequency, each of the first polarizer port and the second polarizer port of the first diplexer in signal communication with the first port of the septum polarizer; a second diplexer including a common port in signal communication with the second port of the septum polarizer to route a signal based upon a frequency, wherein second diplexer further includes a first polarizer port having a first pre-determined passband frequency and a second polarizer port having a second pre-determined passband frequency, each of the first polarizer port and the second polarizer port of the second diplexer in signal communication with the second port of the septum polarizer; and a wave coupler/splitter in signal communication with the diplexer to send and receive signals therebetween, the wave coupler/splitter including a first signal path and a second signal path, wherein the wave coupler/splitter controls a phase shift of a signal transmitted through at least one of the first signal path and the second signal path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiment when considered in the light of the accompanying drawings in which: 
         FIG. 1  is a schematic diagram of an antenna feed network according to an embodiment of the present invention; 
         FIG. 2  is a front perspective view of a three dimensional schematic model of a septum polarizer of the antenna feed network of  FIG. 1 ; 
         FIG. 3  is a schematic diagram of an antenna feed network according to another embodiment of the present invention; 
         FIG. 4  is a front perspective view of a three dimensional schematic model of a septum polarizer of the antenna feed network of  FIG. 3 , showing a polarization pattern at a horn of the septum polarizer; 
         FIG. 5  is a front perspective view of a three dimensional schematic model of a septum polarizer of the antenna feed network of  FIG. 3 , showing a polarization pattern at a horn of the septum polarizer; 
         FIG. 6  is a schematic diagram of an antenna feed network according to another embodiment of the present invention; 
         FIG. 7  is a front perspective view of a three dimensional schematic model of a septum polarizer of the antenna feed network of  FIG. 6 , showing a polarization pattern at a horn of the septum polarizer; 
         FIG. 8  is a front perspective view of a three dimensional schematic model of a septum polarizer of the antenna feed network of  FIG. 6 , showing a polarization pattern at a horn of the septum polarizer; 
         FIG. 9  is a schematic diagram of an antenna feed network according to another embodiment of the present invention; 
         FIG. 10  is a front perspective view of a three dimensional schematic model of a first septum polarizer of the antenna feed network of  FIG. 9 ; and 
         FIG. 11  is a front perspective view of a three dimensional schematic model of a second septum polarizer of the antenna feed network of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION 
     The following detailed description and appended drawings describe and illustrate various embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. 
       FIGS. 1-2  illustrate an antenna feed network  100  according to an embodiment of the present invention. As shown, the network  100  includes a septum polarizer  102 , a pair of diplexers  104 ,  106 , and a wave coupler/splitter  108 . 
     The septum polarizer  102  includes a wave guide  110  defining a cavity  112  therein. As shown, the waveguide  110  is a tapered waveguide. However, the waveguide  110  can have any shape, flare, and dimensions including a predetermined axial ratio in a circular polarization band. It is understood that an axial ratio requirement in the linear polarization band can be relaxed. 
     The waveguide  110  of the septum polarizer  102  includes a horn end  114  to receive and radiate electromagnetic waves in a desired direction. As a non-limiting example, the horn end  114  is an open end. However, the horn end  114  can be enclosed. As further a non-limiting example, the horn end  114  is un-flared and has a substantially square shaped cross-section. It is understood that the wave guide  110  may have one or more expansion curves, i.e. longitudinal cross sections such as elliptical, conical, hyperbolic, or parabolic curves, and not necessarily the same expansion curve in each cross section (i.e. E-plane and H-plane). It is further understood that a wide range of beam patterns may be formed by controlling the dimensions and shape of the waveguide  110 , as well as a shape and placement of a reflector (not shown) and a choke (not shown), for example. 
     A septum  116  is disposed in the cavity  112  to split a portion of the cavity  112  into a first waveguide portion  118  and a second waveguide portion  120 . As shown, the septum  116  is a wall having a stepped configuration to generate circular polarization as can be appreciated by one skilled in the art of antenna feed networks. However, other configurations and shapes can be used. It is understood that the septum  116  can be a gap or stepped channel formed in the waveguide  110  to split a portion of the cavity  112  into the first waveguide portion  118  and the second waveguide portion  120 . 
     In the embodiment shown, the septum  116  extends along a center line of the waveguide  110  and bisects a back end  122  of the waveguide  110  opposite the horn end  114  to form two ports  124 ,  126 . Each of the ports  124 ,  126  is disposed on a respective side of the septum wall  116  and has a generally rectangular shape. As a non-limiting example, the first port  124  is in signal communication with the first waveguide portion  118  and the second port  126  is in signal communication with the second waveguide portion  120 . It is understood that any number of the ports  124 ,  126  can be used. It is further understood that the ports  124 ,  126  can have any shape, size and orientation. 
     The first diplexer  104  includes a common port  128 , a first polarizer port  130 , and a second polarizer port  132 . As shown, the common port  128  is in signal communication with the first port  124  of the septum polarizer  102  for intercommunication of signals therebetween. The first polarizer port  130  has a pre-determined passband frequency and is typically associated with circular polarization. The second polarizer port  132  is in signal communication with the wave coupler/splitter  108 . The second polarizer port  132  has a pre-determined passband frequency that is typically different than a bandwidth associated with the first polarizer port  130 . It is understood that any passband frequency can be associated with the ports  130 ,  132 . It is further understood that any diplexer can be used such as a waveguide diplexer known in the art. 
     The second diplexer  106  includes a common port  134 , a first polarizer port  136 , and a second polarizer port  138 . As shown, the common port  134  is in signal communication with the second port  126  of the septum polarizer  102  for intercommunication of signals therebetween. The first polarizer port  136  has a pre-determined passband frequency and is typically associated with circular polarization. The second polarizer port  138  is in signal communication with the wave coupler/splitter  108 . The second polarizer port  138  has a pre-determined passband frequency that is typically different than a bandwidth associated with the first polarizer port  136 . It is understood that any passband frequency can be associated with the ports  136 ,  138 . It is further understood that any diplexer can be used such as a waveguide diplexer known in the art. 
     The wave coupler/splitter  108  includes a first signal port  140 , a second signal port  142 , a first signal path  144 , and a second signal path  146 . As shown, the first signal path  144  is in signal communication with the second polarizer port  132  of the first diplexer  104 . The first signal path  144  is split into a phase shift portion  148  and a non-shift portion  150 , wherein a variable phase shifter  152  is in signal communication with the phase shift portion  148  of the first signal path  144  to control a phase shift of a signal transmitted therethrough. It is understood that the phase shifting can be accomplished using other wave coupler configurations such as a magic-T, a branch line coupler, and the like, for example. 
     The second signal path  146  is in signal communication with the second port  138  of the second diplexer  106 . The second signal path  146  is split into a phase shift portion  154  and a non-shift portion  156 , wherein a variable phase shifter  158  is in signal communication with the phase shift portion  154  of the second signal path  146  to control a phase shift of a signal transmitted therethrough. 
     In use, a signal is received at the horn end  114  of the waveguide  110  and the septum  116  splits the signal into a left-hand circular polarization (LHCP) component and right-hand circular polarization (RHCP) component. As a non-limiting example, the RHCP component of the signal is received at the port  124  and the LHCP component of the signal is received at the port  126 . Each of the ports  124 ,  126  routes a received component of the signal to the respective common ports  128 ,  134  of the diplexers  104 ,  106 . Each of the diplexers  104 ,  106  routes a received component of the signal to at least one of the polarizer ports  130 ,  132 ,  136 ,  138  based on a frequency of the received signal. In certain embodiments, at least a portion of the signal is routed to the wave coupler/splitter  108  through at least one of the second polarizer ports  132 ,  138  of at least one of the diplexers  104 ,  106 . 
     A signal transmitted through the first signal path  144  of the wave coupler/splitter  108  is divided and transmitted through the phase shift portion  148  and the non-shift portion  150 . Likewise, a signal transmitted through the second signal path  146  of the wave coupler/splitter  108  is divided and transmitted through the phase shift portion  154  and the non-shift portion  156 . 
     The phase shift portion  148  of the first signal path  144  is coupled to the non-shift portion  156  of the second signal path  146  and a combined signal is routed to the first signal port  140 . The phase shift portion  154  of the second signal path  146  is coupled to the non-shift portion  150  of the first signal path  144  and a combined signal is routed to the second signal port  142 . It is understood that relative setting of the phase shifters  152 ,  158  determines the polarization of the combined signal received at the signal ports  140 ,  142 . 
     In certain embodiments, the phase shifters  152 ,  158  are 180 degrees out of phase and the signal ports  140 ,  142  are linearly polarized, the polarization of each of the single ports  140 ,  142  orthogonal to the other. It is understood that the phase shifters  152 ,  158  can be modified to provide various linear polarizations at the signal ports  140 ,  142 . It is further understood that the antenna feed network  100  can be used to transmit polarized signals. 
     As a non-limiting example, the first polarizer ports  130 ,  136  of each of the diplexers  104 ,  106  can be selectively fed with a signal to transmit a RHCP signal and a LHCP signal at the horn end  114 . As a further non-limiting example, each of the signal ports  140 ,  142  of the wave coupler/splitter  108  can be selectively fed with a signal to transmit a linear polarized signal at the horn end  114 . It is understood that relative setting of the phase shifters  152 ,  158  determines the polarization of a transmitted signal at the horn end  114 . As a non-limiting example, where the phase shifters  152 ,  158  are configured to feed each of the ports  124 ,  126  of the septum polarizer  102  with in-phase signals having equal amplitude, the transmitted signal at the horn end  114  is horizontally polarized. As a further non-limiting example, where the phase shifters  152 ,  158  are configured to feed each of the ports  124 ,  126  of the septum polarizer  102  with signals having equal amplitude and 180 degrees out-of-phase, the transmitted signal at the horn end  114  is vertically polarized. As a further non-limiting example, where the phase shifters  152 ,  158  are configured to feed each of the ports  124 ,  126  of the septum polarizer  102  with signals having equal amplitude and 90 degrees out-of-phase, the transmitted signal at the horn end  114  is polarized at 45 degrees from vertical rotated toward one of the ports  124 ,  126  having the leading signal. It is understood that other configurations can be used to generate various linear and circular polarizations for receiving and transmitting signals. 
       FIG. 3  illustrates an antenna feed network  200  according to an embodiment of the present invention similar to the network  100  except as described herein below. As shown, the network  200  includes a septum polarizer  202 , a pair of diplexers  204 ,  206 , and a wave coupler/splitter  208 . 
     The septum polarizer  202  includes a wave guide  210  defining a cavity  212  therein, as shown in  FIGS. 4 and 5 . As shown, the waveguide  210  is a tapered waveguide. However, the waveguide  210  can have any shape, flare, and dimensions. The waveguide  210  includes a horn end  214  to receive and radiate electromagnetic waves in a desired direction. As a non-limiting example, the horn end  214  is an open end. However, the horn end  214  can be enclosed. As further a non-limiting example, the horn end  214  is un-flared and has a substantially square shaped cross-section. It is understood that the wave guide  210  may have one or more expansion curves, i.e. longitudinal cross sections such as elliptical, conical, hyperbolic, or parabolic curves, and not necessarily the same expansion curve in each cross section (i.e. E-plane and H-plane). It is further understood that a wide range of beam patterns may be formed by controlling the dimensions and shape of the waveguide  210 , as well as a shape and placement of a reflector (not shown) and a choke (not shown), for example. 
     A septum  216  is disposed in the cavity  212  to split a portion of the cavity  212  into a first waveguide portion  218  and a second waveguide portion  220 . As shown, the septum  216  has a stepped configuration to generate circular polarization as can be appreciated by one skilled in the art of antenna feed networks. However, other configurations and shapes can be used. 
     In the embodiment shown, the septum  216  extends along a center line of the waveguide  210  and bisects a back end  222  of the waveguide  210  opposite the horn end  214  to form two ports  224 ,  226 . As a non-limiting example, the ports  224 ,  226  can have any size and shape and can be substantially the same or different. Each of the ports  224 ,  226  is disposed on a respective side of the septum  216  and has a generally rectangular shape. As a non-limiting example, the first port  224  is in signal communication with the first waveguide portion  218  and the second port  226  is in signal communication with the second waveguide portion  220 . It is understood that any number of the ports  224 ,  226  can be used. It is further understood that the ports  224 ,  226  can have any shape, size and orientation. 
     The first diplexer  204  includes a common port  228 , a first polarizer port  230 , and a second polarizer port  232 . As shown, the common port  228  is in signal communication with the first port  224  of the septum polarizer  202  for intercommunication of signals therebetween. The first polarizer port  230  has a pre-determined passband frequency and is typically associated with circular polarization. The second polarizer port  232  is in signal communication with the wave coupler/splitter  208 . The second polarizer port  232  has a pre-determined passband frequency that is typically different than a bandwidth associated with the first polarizer port  230 . It is understood that any passband frequency can be associated with the ports  230 ,  232 . It is further understood that any diplexer can be used such as a waveguide diplexer known in the art. 
     The second diplexer  206  includes a common port  234 , a first polarizer port  236 , and a second polarizer port  238 . As shown, the common port  234  is in signal communication with the second port  226  of the septum polarizer  202  for intercommunication of signals therebetween. The first polarizer port  236  has a pre-determined passband frequency and is typically associated with circular polarization. The second polarizer port  238  is in signal communication with the wave coupler/splitter  208 . The second polarizer port  238  has a pre-determined passband frequency that is typically different than a bandwidth associated with the first polarizer port  236 . It is understood that any passband frequency can be associated with the ports  236 ,  238 . It is further understood that any diplexer can be used such as a waveguide diplexer known in the art. 
     The wave coupler/splitter  208  is a magic-T waveguide having a first signal port  240 , a second signal port  242 , a first signal path  244 , and a second signal path  246 . As a non-limiting example, the first signal port  240  is a sum port, wherein a signal incident on the first signal port  240  splits equally between the first signal path  244  and the second signal path  246  with the resulting split signals being in phase. As a further non-limiting example, the second signal port  242  is a delta port or a difference port, wherein a signal incident on the second signal port  242  splits equally between the first signal path  244  and the second signal path  246  with the resulting split signals being 180 degrees out of phase. It is understood that other arrangements of the ports  240 ,  242  can be made. It is further understood that other waveguide coupler/splitters can be used to function as the wave coupler/splitter  208 , as appreciated by one skilled din the art of waveguides. 
     As shown, the first signal path  244  is in signal communication with the second polarizer port  232  of the first diplexer  204 . The second signal path  246  is in signal communication with the second port  238  of the second diplexer  206 . However, any signal routing configuration can be used. 
     In use, a signal is received at the horn end  214  of the waveguide  210  and the septum  216  splits the signal into a left-hand circular polarization (LHCP) component and right-hand circular polarization (RHCP) component. As a non-limiting example, the RHCP component of the signal is received at the port  224  and the LHCP component of the signal is received at the port  226 . Each of the ports  224 ,  226  routes a received component of the signal to the respective common ports  228 ,  234  of the diplexers  204 ,  206 . Each of the diplexers  204 ,  206  routes a received component of the signal to at least one of the polarizer ports  230 ,  232 ,  236 ,  238  based on a frequency of the received signal. In certain embodiments, at least a portion of the signal is routed to the wave coupler/splitter  208  through at least one of the second polarizer ports  232 ,  238  of at least one of the diplexers  204 ,  206 . 
     In certain embodiments, a linear polarized signal received at the horn end  214  is passed through at least one of the second polarizer ports  232 ,  238  of at least one of the diplexers  204 ,  206  based upon a pre-determined linear polarization bandwidth. As a non-limiting example, the signal ports  240 ,  242  are linearly polarized, the polarization of each of the signal ports  240 ,  242  orthogonal to the other. 
     The antenna feed network  200  can be used to transmit polarized signals. As a non-limiting example, the first polarizer ports  230 ,  236  of each of the diplexers  204 ,  206  can be selectively fed with a signal to transmit a RHCP signal and a LHCP signal at the horn end  214 . As a further non-limiting example, each of the signal ports  240 ,  242  of the wave coupler/splitter  208  can be selectively fed with a signal to transmit a linear polarized signal at the horn end  214 . As more clearly shown in  FIG. 4 , where the first signal port  240  (i.e. sum port) of the wave coupler/splitter  208  is fed with a signal, the transmitted signal at the horn end  214  is horizontally polarized. As more clearly shown in  FIG. 5 , where the second signal port  242  (i.e. delta port, difference port) of the wave coupler/splitter  208  is fed with a signal, the transmitted signal at the horn end  214  is vertically polarized. It is understood that in certain embodiments, during transmit or receive, a polarization purity of a linear signal remains constant even if a frequency operation is outside an axial ratio bandwidth of the septum polarizer  202 . 
       FIG. 6  illustrates an antenna feed network  300  according to an embodiment of the present invention similar to the network  100  except as described herein below. As shown, the network  100  includes a septum polarizer  302 , a pair of diplexers  304 ,  306 , and a wave coupler/splitter  308 . 
     The septum polarizer  302  includes a wave guide  310  defining a cavity  312  therein, as shown in  FIGS. 7 and 8 . The waveguide  310  includes a horn end  314  to receive and radiate electromagnetic waves in a desired direction. As a non-limiting example, the horn end  314  is an open end. However, the horn end  314  can be enclosed. As further a non-limiting example, the horn end  314  is un-flared and has a substantially square shaped cross-section. It is understood that the wave guide  310  may have one or more expansion curves, i.e. longitudinal cross sections such as elliptical, conical, hyperbolic, or parabolic curves, and not necessarily the same expansion curve in each cross section (i.e. E-plane and H-plane). It is further understood that a wide range of beam patterns may be formed by controlling the dimensions and shape of the waveguide  310  as well as a shape and placement of a reflector (not shown) and a choke (not shown), for example. The waveguide  310  can have any shape, flare, and dimensions. 
     A septum  316  is disposed in the cavity  312  to split a portion of the cavity  312  into a first waveguide portion  318  and a second waveguide portion  320 . As shown, the septum  316  has a stepped configuration to generate circular polarization as can be appreciated by one skilled in the art of antenna feed networks. However, other configurations and shapes can be used. 
     In the embodiment shown, the septum  316  extends along a center line of the waveguide  310  and bisects a back end  322  of the waveguide  310  opposite the horn end  314  to form two ports  324 ,  326 . As a non-limiting example, the ports  324 ,  326  can have any size and shape and can be substantially the same or different. Each of the ports  324 ,  326  is disposed on a respective side of the septum  316  and has a generally rectangular shape. As a non-limiting example, the first port  324  is in signal communication with the first waveguide portion  318  and the second port  326  is in signal communication with the second waveguide portion  320 . It is understood that any number of the ports  324 ,  326  can be used. It is further understood that the ports  324 ,  326  can have any shape, size and orientation. 
     The first diplexer  304  includes a common port  328 , a first polarizer port  330 , and a second polarizer port  332 . As shown, the common port  328  is in signal communication with the first port  324  of the septum polarizer  302  for intercommunication of signals therebetween. The first polarizer port  330  has a pre-determined passband frequency and is typically associated with circular polarization. The second polarizer port  332  is in signal communication with the wave coupler/splitter  308 . The second polarizer port  332  has a pre-determined passband frequency that is typically different than a bandwidth associated with the first polarizer port  330 . It is understood that any passband frequency can be associated with the ports  330 ,  332 . It is further understood that any diplexer can be used such as a waveguide diplexer known in the art. 
     The second diplexer  306  includes a common port  334 , a first polarizer port  336 , and a second polarizer port  338 . As shown, the common port  334  is in signal communication with the second port  326  of the septum polarizer  302  for intercommunication of signals therebetween. The first polarizer port  336  has a pre-determined passband frequency and is typically associated with circular polarization. The second polarizer port  338  is in signal communication with the wave coupler/splitter  308 . The second polarizer port  338  has a pre-determined passband frequency that is typically different than a bandwidth associated with the first polarizer port  336 . It is understood that any passband frequency can be associated with the ports  336 ,  338 . It is further understood that any diplexer can be used such as a waveguide diplexer known in the art. 
     The wavecoupler/splitter  308  is a branch-line coupler having a first signal port  340 , a second signal port  342 , a first signal path  344 , and a second signal path  346 . As a non-limiting example, the first signal port  340  is an input port, wherein a signal incident on the first signal port  340  splits equally between the first signal path  344  and the second signal path  346  with the resulting split signals being 90 degrees out-of-phase with the second signal path  346  leading. As a further non-limiting example, the second signal port  342  is an isolated port, wherein a signal incident on the second signal port  342  splits equally between the first signal path  342  and the second signal path  344  with the resulting split signals being 90 degrees out of phase with the first signal path  344  leading. It is understood that other arrangements can be used to vary the phase comparison between a signal transmitted along the first single path  344  and the second signal path  346 . It is further understood that other waveguide coupler/splitters can be used to function as a magic-T and a second septum polarizer, as appreciated by one skilled in the art of waveguides. 
     As shown, the first signal path  344  is in signal communication with the second polarizer port  332  of the first diplexer  304 . The second signal path  346  is in signal communication with the second port  338  of the second diplexer  306 . However, any signal routing configuration can be used. 
     In use, a signal is received at the horn end  314  of the waveguide  310  and the septum  316  splits the signal into a left-hand circular polarization (LHCP) component and right-hand circular polarization (RHCP) component. As a non-limiting example, the RHCP component of the signal is received at the port  324  and the LHCP component of the signal is received at the port  326 . Each of the ports  324 ,  326  routes a received component of the signal to the respective common ports  328 ,  334  of the diplexers  304 ,  306 . Each of the diplexers  304 ,  306  routes a received component of the signal to at least one of the polarizer ports  330 ,  332 ,  336 ,  338  based on a frequency of the received signal. In certain embodiments, at least a portion of the signal is routed to the wave coupler/splitter  308  through at least one of the second polarizer ports  332 ,  338  of at least one of the diplexers  304 ,  306 . 
     In certain embodiments, a linear polarized signal received at the horn end  314  is passed through at least one of the second polarizer port  332 ,  338  of at least one of the diplexers  304 ,  306  based upon a pre-determined linear polarization bandwidth. As a non-limiting example, the signal ports  340 ,  342  are linearly polarized, the polarization of each of the signal ports  340 ,  342  orthogonal to the other and rotated 45 degrees from the polarizations that would be received using a magic-T waveguide. 
     The antenna feed network  300  can be used to transmit polarized signals. As a non-limiting example, the first polarizer ports  330 ,  336  of each of the diplexers  304 ,  306  can be selectively fed with a signal to transmit a RHCP signal and a LHCP signal at the horn end  314 . As a further non-limiting example, each of the signal ports  340 ,  342  of the wave coupler/splitter  208  can be selectively fed with a signal to transmit a linear polarized signal at the horn end  314 . As more clearly shown in  FIG. 7 , where the first signal port  340  (i.e. input port) of the wave coupler/splitter  308  is fed with a signal, the transmitted signal at the horn end  314  is polarized at 45° from vertical and rotated towards the port  326 . As more clearly shown in  FIG. 8 , where the second signal port  342  (i.e. isolated port) of the wave coupler/splitter  308  is fed with a signal, the transmitted signal at the horn end  314  is polarized at 45° from vertical and rotated towards the port  324 . 
       FIGS. 9-11  illustrate an antenna feed network  400  according to an embodiment of the present invention similar to the network  100  except as described herein below. As shown, the network  400  includes a first septum polarizer  402 , a pair of diplexers  404 ,  406 , a wave coupler/splitter  408 . 
     As more clearly shown in  FIG. 10 , the first septum polarizer  402  includes a wave guide  410  defining a cavity  412  therein. As shown, the waveguide  410  has a substantially square cross section. The waveguide  410  includes a horn end  414  to receive and radiate electromagnetic waves in a desired direction. As a non-limiting example, the horn end  414  is an open end. However, the horn end  414  can be enclosed. As further a non-limiting example, the horn end  414  is un-flared and has a substantially square shaped cross-section. It is understood that the wave guide  410  may have one or more expansion curves, i.e. longitudinal cross sections such as elliptical, conical, hyperbolic, or parabolic curves, and not necessarily the same expansion curve in each cross section (i.e. E-plane and H-plane). It is further understood that a wide range of beam patterns may be formed by controlling the dimensions and shape of the waveguide  410  as well as a shape and placement of a reflector (not shown) and a choke (not shown), for example. The waveguide  410  can have any shape, flare, and dimensions. 
     A septum  416  is disposed in the cavity  412  to split a portion of the cavity  412  into a first waveguide portion  418  and a second waveguide portion  420 . As shown, the septum  416  has a stepped configuration to generate circular polarization as can be appreciated by one skilled in the art of antenna feed networks. However, other configurations and shapes can be used. 
     In the embodiment shown, the septum  416  extends along a center line of the waveguide  410  and bisects a back end  422  of the waveguide  410  opposite the horn end  414  to form two ports  424 ,  426 . As a non-limiting example, the ports  424 ,  426  can have any size and shape and can be substantially the same or different. Each of the ports  424 ,  426  is disposed on a respective side of the septum  416  and has a generally rectangular shape. As a non-limiting example, the first port  424  is in signal communication with the first waveguide portion  418  and the second port  426  is in signal communication with the second waveguide portion  420 . It is understood that any number of the ports  424 ,  426  can be used. It is further understood that the ports  424 ,  426  can have any shape, size and orientation. 
     The first diplexer  404  includes a common port  428 , a first polarizer port  430 , and a second polarizer port  432 . As shown, the common port  428  is in signal communication with the first port  424  of the septum polarizer  402  for intercommunication of signals therebetween. The first polarizer port  430  has a pre-determined passband frequency and is typically associated with circular polarization. The second polarizer port  432  is in signal communication with the wave coupler/splitter  408 . The second polarizer port  432  has a pre-determined passband frequency that is typically different than a bandwidth associated with the first polarizer port  430 . It is understood that any passband frequency can be associated with the ports  430 ,  432 . It is further understood that any diplexer can be used such as a waveguide diplexer known in the art. 
     The second diplexer  406  includes a common port  434 , a first polarizer port  436 , and a second polarizer port  438 . As shown, the common port  434  is in signal communication with the second port  426  of the septum polarizer  402  for intercommunication of signals therebetween. The first polarizer port  436  has a pre-determined passband frequency and is typically associated with circular polarization. The second polarizer port  438  is in signal communication with the wave coupler/splitter  408 . The second polarizer port  438  has a pre-determined passband frequency that is typically different than a bandwidth associated with the first polarizer port  436 . It is understood that any passband frequency can be associated with the ports  436 ,  438 . It is further understood that any diplexer can be used such as a waveguide diplexer known in the art. 
     As more clearly shown in  FIG. 11 , the wave coupler/splitter  408  is a second septum polarizer including a wave guide  440  defining a cavity  442  therein. As shown, the waveguide is tapered. However, the waveguide  440  can have any shape, flare, and dimensions. The waveguide  440  includes a horn end  444  to receive and radiate electromagnetic waves in a desired direction. As a non-limiting example, the horn end  444  is an open end. However, the horn end  444  can be enclosed. As further a non-limiting example, the horn end  444  is un-flared and has a substantially square shaped cross-section. It is understood that the wave guide  440  may have one or more expansion curves, i.e., longitudinal cross sections, such as elliptical, conical, hyperbolic, or parabolic curves, and not necessarily the same expansion curve in each cross section (i.e. E-plane and H-plane). It is further understood that a wide range of beam patterns may be formed by controlling the dimensions and shape of the waveguide  440  as well as a shape and placement of a reflector (not shown) and a choke (not shown), for example. 
     A septum  446  is disposed in the cavity  442  to split a portion of the cavity  442  into a first waveguide portion  448  (i.e. a first signal path) and a second waveguide portion  450  (i.e. a second signal path). As shown, the septum  446  has a stepped configuration to generate circular polarization as can be appreciated by one skilled in the art of antenna feed networks. It is understood that other configurations can be used. 
     In the embodiment shown, the septum  446  extends along a center line of the waveguide  440  and bisects a back end  452  of the waveguide  440  opposite the horn end  444  to form two ports  454 ,  456 . As a non-limiting example, the ports  454 ,  456  can have any size and shape and can be substantially the same or different. Each of the ports  454 ,  456  is disposed on a respective side of the septum  446  and has a generally rectangular shape. As a non-limiting example, the first port  454  is in signal communication with the first waveguide portion  448  and the second port  456  is in signal communication with the second waveguide portion  450 . It is understood that any number of the ports  454 ,  456  can be used. It is further understood that the ports  454 ,  456  can have any shape, size and orientation. 
     As shown, the port  454  is in signal communication with the second polarizer port  432  of the first diplexer  404 . The port  456  is in signal communication with the second port  438  of the second diplexer  406 . However, any signal routing configuration can be used. 
     In use, a signal is received at the horn end  414  of the waveguide  410  and the septum  416  splits the signal into a left-hand circular polarization (LHCP) component and right-hand circular polarization (RHCP) component. As a non-limiting example, the RHCP component of the signal is received at the port  424  and the LHCP component of the signal is received at the port  426 . Each of the ports  424 ,  426  routes a received component of the signal to the respective common ports  428 ,  434  of the diplexers  404 ,  406 . Each of the diplexers  404 ,  406  routes a received component of the signal to at least one of the polarizer ports  430 ,  432 ,  436 ,  438  based on a frequency of the received signal. In certain embodiments, at least a portion of the signal is routed to the wave coupler/splitter  408  through at least one of the second polarizer ports  432 ,  438  of at least one of the diplexers  404 ,  406 . 
     In certain embodiments, a linear polarized signal received at the horn end  414  is passed through at least one of the second polarizer ports  432 ,  438  of at least one of the diplexers  404 ,  406  based upon a pre-determined linear polarization bandwidth. As a non-limiting example, the horn end  444  of the wave coupler/splitter  408  is linearly polarized. 
     The antenna feed network  400  can be used to transmit polarized signals. As a non-limiting example, the first polarizer ports  430 ,  436  of each of the diplexers  404 ,  406  can be selectively fed with a signal to transmit a RHCP signal and a LHCP signal at the horn end  414 . As a further non-limiting example, the horn end  444  of the wave coupler/splitter  408  can be selectively fed with a signal to transmit a linear polarized signal at the horn end  414  of the first septum polarizer  402 . 
     The antenna feed networks  100 ,  200 ,  300 ,  400  provide a compact and light weight solution to an application requiring the capability of both linear and circular polarization. 
     It is understood that the antenna feed networks  100 ,  200 ,  300 ,  400  can be operated as an independent antenna or as a feed for a reflector system. The reflector system can be a parabolic reflector, a shaped reflector or any other surface requiring to be illuminated by the feed system. In addition, those familiar with the art will understand that the feed can also be used in (but not limited to) other antenna configurations such as the Cassegrain, Gregorian or a multitude of other systems. 
     It is further understood that in certain embodiments, the antenna feed networks  100 ,  200 ,  300 ,  400  uses a corrugated feed horn. Those familiar with the art will understand that the feed horn can be of any kind and not limited to the one described herein. The other types of feed horn which can be used are, for example, (but not limited to) potter horns, broad band horns, multimode horns of several types, horns with stepped junctions, horns with sloped or profiled walls and horns utilizing meta-materials. The antenna feed can be used with any radiating horn which has the required RF bandwidth compatible with the bandwidth of the antenna feed described. 
     From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, make various changes and modifications to the invention to adapt it to various usages and conditions.