Abstract:
A radar system, such as a weather radar system, includes a radar antenna and a processor. The processor is configured to cause a first radar beam to be provided using a first portion of the radar antenna. The processor is configured to cause a second radar beam to be provided using a phase adjusted portion of the antenna and a remaining portion of the radar antenna. A radar method and system can allow multiple low-loss overlapping radar beams to be rapidly generated to support a sequential lobing process which may be used to generate intra-beam target angle estimates. The production of these overlapping beams does not require mechanical antenna movement but beam selection is controlled by a simple electronic switch in some embodiments.

Description:
BACKGROUND 
       [0001]    Embodiments of the inventive concepts disclosed herein generally relate to the field of radar systems, and more particularly, but not by way of limitation, to estimation of target angles within multiple overlapping radar beams within a radar system (e.g., a weather radar system). 
         [0002]    Efforts in the past have used multiple antenna azimuth sweeps at different antenna pointing elevations, sequential sub-aperture techniques, rapid repositioning of ESA radar beams, or multiple receiver monopulse techniques to perform this function. When the target angle estimates are needed, such as in a weather radar ground clutter to weather return discrimination process, any of these techniques may be used with various performance and/or cost tradeoffs. There is a need for a low cost, low complexity, and rapid radar beam repositioning technique to support both a target angle estimation processes and to more rapidly sample a 3D radar volume of space. 
       SUMMARY 
       [0003]    In one aspect, embodiments of the inventive concepts disclosed herein are directed to a method of using an airborne radar. The method includes providing a first radar beam using a full aperture of an antenna, sampling first returns using the full aperture of the antenna, and providing a second radar beam using the full aperture of the antenna. The second radar beam includes a first phase adjusted portion provided by a second portion of the radar antenna and a non-phase delayed portion provided by a third portion of the antenna. The full aperture includes the second portion and the third portion. The method also includes sampling second returns using the full aperture of the antenna. 
         [0004]    In a further aspect, embodiments of the inventive concepts disclosed herein are directed a radar system. The radar system includes an antenna and a processor. The processor is configured to cause a first radar beam to be provided using a first portion of the radar antenna and to cause a second radar beam to be provided using a phase adjusted portion of the antenna and a remaining portion of the radar antenna. In some embodiments, the second radar has a dip. 
         [0005]    In a further aspect, embodiments of the inventive concepts disclosed herein are directed to a radar system. The radar system includes a radar antenna having a first portion and a second portion, a feed circuit coupled to the radar antenna including a phase shifter in a path for the second portion, and a control circuit. The control circuit is configured to provide a first radar beam using the first portion and the second portion and provide a second radar beam using the first portion of the radar antenna and the second portion of the radar antenna. The second radar beam is provided using a phase adjustment provided by the phase shifter in the path for the second portion and has a response with a dip at an angle between negative and positive five degrees. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Implementations of the inventive concepts disclosed herein may be better understood when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, which are not necessarily to scale, and in which some features may be exaggerated and some features may be omitted or may be represented schematically in the interest of clarity. Like reference numerals in the figures may represent and refer to the same or similar element, feature, or function. In the drawings: 
           [0007]      FIG. 1  is a partial side view of a nose of an aircraft including a radar system according to some embodiments; 
           [0008]      FIG. 2  is a block diagram of the radar system illustrated in  FIG. 1 ; 
           [0009]      FIG. 3  is a more detailed block diagram of the radar system illustrated in  FIG. 2 ; 
           [0010]      FIG. 4  is a more detailed block diagram of an embodiment of a feed network and an antenna for the radar system illustrated in  FIG. 2 ; 
           [0011]      FIG. 5  is a more detailed block diagram of an embodiment of a network including waveguide and coaxial paths for the radar system illustrated in  FIG. 2 ; 
           [0012]      FIG. 6  is a graph showing beam power versus elevation angles for first, second and third drive states; 
           [0013]      FIG. 7  is a graph showing beam power versus elevation angles for a sum beam, a shifted beam, a difference between the sum beam and the shifted beam, and a derivative of the difference beam for the radar system illustrated in  FIG. 2  according to some embodiments; 
           [0014]      FIG. 8  is a schematic diagram showing an angle to target for the radar system illustrated in  FIG. 2  according to some embodiments; 
           [0015]      FIG. 9  is a flow diagram showing operations of the radar system illustrated in  FIG. 2  according to some embodiments; and 
           [0016]      FIG. 10  is a block diagram of a phase shifter for use in the feed network illustrated in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Before describing in detail the inventive concepts disclosed herein, it should be observed that the inventive concepts disclosed herein include, but are not limited to, a novel structural combination of one or more data/signal processing components, sensors, and communications circuits, and are not limited to the particular detailed configurations thereof. Accordingly, the structure, methods, functions, control and arrangement of components, modules, software, and circuits have, for the most part, been illustrated in the drawings by readily understandable block representations and schematic diagrams, in order not to obscure the disclosure with structural details which will be readily apparent to those skilled in the art, having the benefit of the description herein. Further, the inventive concepts disclosed herein are not limited to the particular embodiments depicted in the exemplary diagrams, but should be construed in accordance with the language in the claims. 
         [0018]    With reference to  FIG. 1 , an aircraft  10  includes a nose  12 . The nose  12  includes a radar antenna  16  which is part of a radar system  20 . According to some embodiments, the radar system  20  is located on the top of the aircraft  10 , on a wing pod, or on the tail of the aircraft  10 . In some embodiments, the radar system  20  is a weather radar system and provides radar beams  22  and  24  configured for accurate angle estimation, such as elevation angle estimation. In some embodiments, part of one of the radar beams  22  and  24  is phase shifted with respect to other (e.g., a spoiled) which allows for improved correlation. The radar beams  22  and  24  are provided by a MULTISCAN radar system configured as described herein in some embodiments. 
         [0019]    In some embodiments, the use of the spoiled beam provides improved elevation angle estimates which allow for improved identification and rejection of ground clutter and which allow for the use of smaller antennas to be used for wind shear detection. In some embodiments, one of radar beams  22  and  24  is configured as a spoiled beam which can be used for overflight detection and weather detection or wind shear detection, thereby reducing the number of beams required for overflight detection and weather or wind shear detection. In some embodiments, the spoiled beam has larger elevation coverage suitable for overflight detection. In some embodiments, the radar system  20  achieves higher loop gain relative to split aperture performance (e.g., a 4.5 decibel (dB) two way radar loop performance improvement). 
         [0020]    In some embodiments, the radar returns (e.g., weather radar returns) received by the radar antenna  16  associated with the radar beams  22  and  24  are combined and processed to determine an angle (elevation angle) to the target. The radar beams  22  and  24  are provided sequentially and the radar returns are received sequentially in some embodiments. In some embodiments, coding is utilized so that the radar beams  22  and  24  are provided simultaneously or near simultaneously and the radar returns are received simultaneously (e.g., using parallel transmit and receive channels) or near simultaneously. In some embodiments, the power associated with the returns are subtracted logarithmically (e.g., divided) from each other and the change in power per angle is compared to a profile to determine the angle to target to estimate elevation angle (e.g., within the beam). Although described below with respect to elevation angle estimates, similar techniques can be used or azimuth angle estimates in some embodiments. 
         [0021]    In some embodiments, the radar beam  22  is a full aperture or sum beam and the radar beam  24  is provided as a full aperture beam with half of the beam phase adjusted (e.g., 90 degree delay). The return for the radar beam  22  is received on the full aperture without a phase adjustment and the return for the radar beam  24  is received on the full aperture with or without the phase adjustment on half of the radar antenna  16  in some embodiments. Other phase adjustments and proportions of the radar antenna  16  can be used for the radar beam  24  and the return associated with the radar beam  24  in some embodiments. 
         [0022]    The radar antenna  16  can be of various sizes and types. The radar antenna  16  is mechanically and/or electronically steerable and the radar system  20  has the capability to make phase adjustments on portions of the radar antenna  16  in some embodiments. The radar antenna  16  is a small antenna having a radius of less than sixteen inches or less than twelve inches in some embodiments. In some embodiments, the radar antenna  16  is a passive electronically steered antenna array (PESA), an active electronically steered array AESA, a mechanically steerable slotted waveguide array, parabolic antenna, or other aperture. In some embodiments, phase can be adjusted on quarter or one half portions of the antenna  16  and is configured as an avionic weather radar antenna. Radar system  20  can use software systems and computer resources for processing radar beams  22  and  24  and returns therefrom compatible with various types of antennas including AESA products and mechanically steered antennas in some embodiments. 
         [0023]    Referring to  FIG. 2 , a block diagram of the radar system  20  is shown, according to an exemplary embodiment. The radar antenna  16  includes at least a portion  32  and a portion  34 . The radar system  20  includes the radar antenna  16 , a feed circuit  42 , a transmitter /receiver circuit  44 , and a processor  46 . The feed circuit  42  is coupled between the radar antenna  16  and the transmitter/receiver circuit  44 . The processor  46  is coupled to the transmitter/receiver circuit  44 , provides signals for providing the radar beams  22  and  24 , and receives data associated with the radar returns via the transmitter/receiver circuit  44 . The feed circuit  42  includes a phase adjustment circuit  48   
         [0024]    The radar antenna  16  under control of the processor  46  scans the terrain and/or atmosphere for targets (e.g., ground targets, aircraft targets, or weather targets). According to one exemplary embodiment, the scan is an azimuth scan at an elevation angle for estimating the terrain elevation at a specific location. Alternatively, the scans may be in one or multiple directions. Although only two portions  32  and  34  are shown, other numbers (e.g., 3, 4, 8, 16, 100, etc.) of portions  32  and  34  and various area sizes (half, quarter, thirds, tenths, hundredths, etc.) for the portions  32  and  34  are available and selectable for phase adjustments in some embodiments. 
         [0025]    In some embodiments, the processor  46  causes the radar antenna  16  to provide the radar beams  22  and  24  using the portions  32  and  34  (e.g., the full aperture of radar return data). The processor  46  causes the phase of one of the radar beams  22  and  24  to be spoiled by providing a phase adjustment to the portion  32  or  34  via the phase adjustment circuit  48  in some embodiments. The phase adjustment circuit  48  includes active or passive phase delay circuits, such as selectable phase delay paths. In some embodiments, the amount of the phase adjustment is programmable or selectable by the processor  46 . In some embodiments, the phase adjustment circuit  48  includes a switchable phase delay circuit for one of the portions  32  and  34  of the radar antenna  16 . Various criteria and system parameters can be considered when choosing an appropriate phase adjustment. The phase adjustment and the sizes of the portions  32  and  34  can be chosen to achieve a particular beam shape, power characteristic, side lobe characteristic, etc. 
         [0026]    In some embodiments, the radar return data associated with the radar beams  22  and  24  received from the transmitter/receiver circuit  44  are combined by the processor  46  and analyzed for targets (e.g., weather targets or terrain targets). The radar return data associated with the radar beams  22  and  24  are subtracted or divided from each other and the power to angle profile is compared to an expected power to angle profile. In some embodiments, changes in power versus angle of the difference are compared to a derivative of the difference profile. Other exemplary embodiments of the radar system  20  process the radar return data differently. 
         [0027]    In some embodiments, the spoiled beam includes a null pattern and is utilized to estimate the elevation of terrain. While sweeping the antenna  16  vertically to obtain the radar response from terrain, the null pattern produces a sharp dip in return power as the null is swept past ground clutter. This narrow dip is much narrower than data produced by a normal sum beam similarly being swept vertically. Advantageously, the radar system  20  estimates a location in the swept beam where the power change (as ground clutter is swept past) is easily identified even when weather is in view. 
         [0028]    The radar system  20  can use the split or sub-aperture techniques and components of the radar systems described in U.S. Pat. Nos. 6,741,208, 7,616,150, 7,843,380, 7,889,117, 8,558,731, and 8,773,301 incorporated herein by reference and assigned to the assignee of the present application. The type of the radar system  20  and data gathering techniques are not discussed in the specification in a limiting fashion. 
         [0029]    With reference to  FIG. 3 , the processor  46  includes a return memory  82 , a return memory  84 , a transmit control circuit  86 , a difference circuit  88 , a target processing circuit  92 , and an analysis circuit  94 . The processor  46  stores radar return data associated with the radar beam  22  in the return memory  82  and stores radar return data associated with the radar beam  24  in the return memory  84 . The radar return data from the return memories  82  and  84  are differenced in the difference circuit  88 . The difference circuit  88  includes software or hardware for correlating the radar return data from the return memories  82  and  84  and determining a difference. 
         [0030]    The target processing circuit  92  uses the difference from the difference circuit  88  to locate targets. The target processing circuit  92  can determine an elevation angle (within the beam) to each target. The analysis circuit  94  receives data from the target process circuit and determines type and presence of terrain and weather phenomena. For example, the analysis circuit  94  uses MULTISCAN radar system techniques to determine the presence of weather phenomena (e.g., analysis of power, spectral width, range, temperature, altitude, velocity, etc.). The transmit control circuit  86  provides signals to the transmitter/receiver circuit  44  and the phase adjustment circuit  48  so that the radar antenna  16  provides the radar beams  22  and  24 . 
         [0031]    The transmit control circuit  86  can provide a radar signal at the appropriate frequency, pulse repetition frequency to the antenna  16  through the feed circuit  42  and a phase control signal to the phase adjustment circuit  48 . The radar signals and radar returns are in the X-band S-band, W-band or C-band in some embodiments. 
         [0032]    The transmit control circuit  86 , the difference circuit  88 , the target processing circuit  92 , and the analysis circuit  94  are software modules, circuits, or combinations thereof in some embodiments. The processor  46  can be, or can include one or more microprocessors, an application specific integrated circuit (ASIC), a circuit containing one or more processing components, a group of distributed processing components, circuitry for supporting a microprocessor, or other hardware configured for processing. 
         [0033]    In some embodiments, the radar system  20  provides data representing a 120 degree field of view in accordance with a weather radar sweep. The sweep can be limited during approach to be a 30 azimuth degree sweep or be a 180 degree sweep in some embodiments. Various types of sweeps, sweep patterns, and sweep speeds can be utilized without departing from the scope of the embodiments disclosed herein. 
         [0034]    With reference to  FIG. 4 , the radar antenna  16  can be configured to include the portion  32  including top quarter portions  132  and  133  and the portion  34  including bottom quarter portions  134  and  135  in some embodiments. The portions  132 ,  133 ,  134 , and  135  receive radar signals from the feed circuit  42  via ports  142 ,  143 ,  144 , and  145 . In some embodiments, two additional phase shifters are added, so there are four phase shifters, one per quadrant, thereby allowing beam spoiling both in elevation and azimuth. The feed circuit  42  includes the phase adjustment circuit  48 , a splitter  152 , a splitter  154 , and a splitter  156 . The phase adjustment circuit  48  includes a phase splitter  162  and a phase splitter  164 . The feed circuit  42  include separate transmit and receive paths or bidirectional transmit/receive paths in some embodiments. The feed circuit  42  is described below as including a unidirectional transmit path. In some embodiments, where the radar antenna  16  includes the portions  32  and  34  without sub portions, two phase shifters can be reduced to one phase shifter against a fixed reference path. Phase shifters can similarly be reduce to two phase shifters against a fixed elevation reference path and a fixed azimuthal reference path. In some embodiments, the radar antenna  16  is configured for both azimuth and elevation phase shift based beam sharpening (e.g., configured to provide a phase shift to portions  132  and  134  without providing a phase shift to portions  133  and  135 ). 
         [0035]    The splitter  156  receives the radar signal for the radar beams  22  and  24  and provides two versions of the radar signal to the phase adjustment circuit  48 . The splitter  156  receives the radar signal for the radar beam  22  followed by the radar signal for the radar beam  24  from the transmitter/receiver circuit  44  ( FIG. 3 ) in some embodiments. Radar beams are created at the output of the splitter  156  by combining the returns from the top and bottom halves of the antenna  16 . One beam is for no differential phase shift and one beam is for the differential phase shift. Either in-phase or 90 hybrid splitters can be used The processor  46  sets the phase adjustment to a first setting using phase shifters  162  and  164  for the radar beam  22  and the radar antenna  16  transmits the radar beam  22  using all four portions  132 ,  133 ,  134 , and  135 . The portions  132 ,  133 ,  134 , and  135  receive four versions of the radar signals provided by the splitters  152  and  154  via ports  142 ,  143 ,  144 , and  145  in some embodiments. The radar antenna  16  can include switches controlled by the processor  46  for selecting portions  132 ,  133 ,  134 , and  135 . The processor  46  sets the phase adjustment to a first setting for receiving the radar return associated with radar beam  22  using all four portions  132 ,  133 ,  134 , and  135 . The processor  46  sets the phase adjustment to the first setting for portions  132  and  133  using the phase shifter  162  and sets the phase adjustment to a second setting for portions  134  and  135  using the phase shifter  164  for the radar beam  24 . The portions  132  and  133  receive two versions of the radar signal provided by the splitter  152  via ports  142  and  143 , and the portions  134  and  135  receive two versions of the radar signal provided by the splitter  154  via ports  144  and  145  in some embodiments. The radar antenna  16  transmits the radar beam  24  using all four portions  132 ,  133 ,  134 , and  135 . The processor  46  sets the phase adjustment to the first setting for receiving the radar return associated with radar beam  24  using all four portions  132 ,  133 ,  134 , and  135  in some embodiments. The processor  46  sets the phase adjustment to the first setting and sets the phase adjustment to the second setting for receiving the radar return associated with radar beam  24  using all four portions  132 ,  133 ,  134 , and  135  in some embodiments. 
         [0036]    With reference to  FIG. 5 , a waveguide feed circuit  200  can be used as feed circuit  42  and includes a waveguide to coaxial converter  202 , a 0/90/180 degree hybrid subminiature version A (SMA) splitter  206 , phase adjustment circuit  48  including phase splitters  162  and  164 , a SMA splitter  206 , a SMA splitter  208 , a coaxial to waveguide converter  212 , a coaxial to waveguide converter  214 , a coaxial to waveguide converter  216 , a coaxial to waveguide converter  218 . The SMA connectors are not required. Coaxial to waveguide converters  212 ,  214 ,  216 , and  218  are coupled to respective waveguide to ½ waveguide tapers  222 ,  224 ,  226 , and  228  which are coupled to respective ports  142 ,  143 ,  144 , and  145  of the radar antenna  16  ( FIG. 4 ) embodied as a waveguide aperture in some embodiments. The waveguide tapers are not required in some embodiments. The waveguide feed circuit  200  is implemented in waveguide technologies for minimal loss, in printed circuit board technologies for lowest cost, or in hybrid waveguide/printed circuit board technologies in some embodiments. 
         [0037]    With reference to  FIG. 6 , a chart  900  includes an X axis  904  representing elevation angle with respect to boresight of the antenna, a Y axis  906  representing amplitude in dB, a line  912  representing the antenna beam when the antenna  16  is unshifted, a line  914  representing the antenna beam when the antenna  16  is shifted in a top half (e.g., 90 degrees) and unshifted in a bottom half, and a line  916  representing the antenna beam when the antenna  16  is shifted in a bottom half (e.g., 90 degrees) and unshifted in a top half. The response represented by the line  916  is shifted up in elevation when compared to the unshifted response associated with the line  912 , and the response represented by the line  914  is shifted down in elevation when compared to the unshifted response associated with the line  912  according to some embodiments. The responses represented by the lines  912 ,  914 , and  916  are nearly frequency independent in a range between 9.43 GHz and 9.49 GHz in some embodiments. The line  912  has a beam peak at 0.57 degrees, the line  914  has a beam peak at −2.86 degrees, and the line  916  has a beam peak at 2.32 degrees in some embodiments. The responses associated with the lines  914  and  916  include dips at angles of approximately negative 5 (e.g., 2-3) degrees and positive 5 (e.g., 2-3) degrees, respectively. Different responses and beam skew are possible using different relative phase shifts. 
         [0038]    With reference to  FIG. 7 , a chart  1000  includes an X axis  1004  representing elevation angle with respect to boresight of the antenna, a Y axis  1006  representing amplitude in dB, a line  1012  representing the antenna beam when the antenna  16  is unshifted, a line  1014  representing the antenna beam when the antenna  16  is shifted in a top half (e.g., 90 degrees) and unshifted in a bottom half, a line  1016  representing a difference between the antenna beam of line  1012  and the antenna beam of line  1014 , and a line  1018  representing a derivative with respect to elevation angle of the difference between the antenna beam of line  1012  and the antenna beam of line  1014  in some embodiments. The large power to angle response of the derivative provides increased sensitivity for target elevation determinations as shown by the line  1018 . 
         [0039]    With reference to  FIG. 8 , a target  800  is disposed at an angle to target  802  associated with a boresight angle  804  of the antenna  16 . The bore sight angle  802  can be provided at various tilt angles associated with the antenna  16 . 
         [0040]    With reference to  FIG. 9 , the processor  46  or other computing platform can execute a flow  1100  to sense elevation of terrain, obstacles, runways, runway features, asphalt, or weather phenomena using the radar system  20  according to some embodiments. At an operation  1102 , the radar system  20  provides a full sum beam via the radar antenna  16 . At an operation  1104 , the radar system  20  receives a radar return associated with the full sum beam via the radar antenna  16  and stores radar return data associated with the full sum beam. The radar return data of the operation  1104  can include information about weather conditions, terrain, obstacles, or any combination thereof. 
         [0041]    At an operation  1106 , the radar system  20  provides a spoiled beam via the radar antenna  16 . The spoiled beam is provided by adjusting the phase (e.g., by 90 degrees) of a portion (one half) of the radar antenna  16  in some embodiments. The spoiled beam can be configured to either look downward or upward. At an operation  1108 , the radar system  20  receives a radar return associated with the spoiled beam via the radar antenna  16  and stores radar return data associated with the spoiled beam. The return path associated with the antenna  16  can include the phase adjustment of the operation  1106  in the operation  1108  or the phase adjustment can be removed or changed in the operation  1108 . The radar return data of the operation  1108  can include information about weather conditions, terrain, obstacles, or any combination thereof. 
         [0042]    At an operation  1110 , the radar system  20  takes a difference or divides the radar returns from the operation  1104  and  1108 . The radar returns can be differenced in a variety of ways. In some embodiments, the radar returns are spatially correlated with respect to each other and the power at each location or bin is logarithmically subtracted from each other to determine the difference. In some embodiments, the radar returns are represented by polynomial expressions. The radar system  20  uses the difference to determine the elevation (within the beam) to a target in an operation  1112 . If changes in elevation angle per angle are larger, it increases sensitivity to determine target elevation. 
         [0043]    The radar system  20  uses the difference (e.g., line  1016  in  FIG. 7 ) to determine the angle to target  802  ( FIG. 8 ) in the antenna plane of the spoiling of the beam in some embodiments. In some embodiments the radar system  20  can determine the elevation of the target taking into account the attitude of the antenna  16 . A coordinate transformation from antenna coordinates to the horizontal plane coordinates can be used. According to one example, the antenna  16  is spoiled in the vertical plane and the antenna  16  has no roll so the angle to target and the tilt angle of the antenna  16  can be added to determine the elevation angle to the target. The elevation angle to the target is the elevation angle with respect to the horizon, not to be confused with the elevation angle with respect to the boresight of the antenna. 
         [0044]    At an operation  1114 , the radar system  20  analyzes the radar return data to determine target location and perform weather detection and/or terrain detection. At an operation  1106 , the radar return data from the operation  1108  is used for overflight detection. The larger elevation coverage of the spoiled beam makes such radar return data appropriate for overflight detection without requiring additional beams in some embodiments. 
         [0045]    With reference to  FIG. 10 , a phase shifter  1200  can be utilized in the radar system  20  (e.g., as phase shifter  162  or  164  in  FIG. 4 ). In some embodiments, the phase shifter  1200  is embodied as a quadrature divider/combiner, a branch line 90 degree coupler, or a rat race coupler. The phase shifter  1200  includes an input  1202 , an output  1204 , and diode switches  1206  and  1208 . Diode switches  1206  and  1208  can be used to control the phase delay through the phase shifter  1200 . In some embodiments, the diode switches  1206  and  1208  are PIN diodes, switching transistors, MEMS switches, or any RF switching device. 
         [0046]    In some conventional phase shifters, when a switch experiences a catastrophic failure and is stuck in the off state, a full aperture mode of operation required for MULTISCAN modes of operation is not available, thus making the entire radar system fail. Advantageously, the phase shifter  1200  can be configured such that its failure mode provides a full aperture radiation pattern for traditional (dual-mechanical sweep) operation. This failure mode can be a back-up or go home mode for the radar system  20 . The back mode enables an extremely high mean time between failure (MTBF), reliability, availability, dispatchibility, etc. for the radar system  20  based on this disclosure. 
         [0047]    The radar system  20  using the processor  45  can sense a failure mode associate with the phase shifter  1200 . The most common failure modes for the switching diodes  1206  and  1208  are shorted junctions. When one of the switching diodes  1206  shorts, the other switching diode  1208  is protected. This creates an offset in the phase shifter  1200  that would result in higher insertion loss. 
         [0048]    This failure state is detectable during the reveres bias state on the power supply because current is drawn in the failure mode where in un-failed mode there is no current draw. When the current draw is detected during the reverse bias state, the power supply can hard forward bias the switching diodes  1206  and  1208 , blowing the switching diode  1208  to a short to match the state of the initially blown switching diode  1206 . This results in a failure mode which has a fixed phase shift with lowest possible insertion loss and would allow the radar system  20  to continue to operate as normal without phase shifting. 
         [0049]    For the dual phase shifter feed case, as shown in  FIG. 5 , the failure mode with the fixed phase state provides the same pattern that is used in normal weather and mechanically scanned MULTUISCAN modes(e.g., according to the methodology discussed with reference to  FIG. 10  (an antenna beam associated with the line  1012 )). The radiation pattern allows the radar system  20  to operate in a full-aperture mode during failure of the phase shifter  1200  which is adequate for normal MULTISCAN radar system modes of operation. Since the phase shifter&#39;s failure mode for both phase shifters is identical, each feed path will experience the same loss and phase shifter to the first order. This balance phase and amplitude scenario will result in a low side lobe radiation pattern. 
         [0050]    For the single phase sifter feed embodiment (similar to the feed of  FIG. 5 ) operation in this failure mode with the fixed phase state provides the same pattern that is used in the single sweep MULTUISCAN methodology discussed with reference to  FIG. 10  (an antenna beam associated with the line  1014 ). The radiation pattern is provided in a worst case scenario, thereby allowing the radar system  20  to operate in a full-aperture mode during failure of the phase shifter  1200  which is adequate for normal MULTISCAN radar system modes of operation 
         [0051]    In some embodiments, the amount of beam pointing squint is determined a priority and is stored as a motion control offset command for the radar antenna  16  during the failure mode. Beam dithering, and other radar processing algorithms can be used to mitigate the effects of the higher side lobe of the failure mode. 
         [0052]    Although specific steps are shown and described in a specific order, it is understood that the method may include more, fewer, different, and/or a different ordering of the steps to perform the function described herein. Flow  1100  can be implemented in software on a computing platform associated with a weather radar system, a TAS, or other aviation device. Flow  1100  is implemented on a weather radar computing platform such as an RDR 4000, MULTISCAN, or WXR-2100 system. 
         [0053]    The exemplary embodiments and representations illustrated in the figures and described herein are offered by way of example only. Accordingly, the present application is not limited to a particular embodiment, but extends to various modifications that nevertheless fall within the scope of the appended claims. The order or sequence of any processes or method steps may be varied or re-sequenced according to alternative embodiments. 
         [0054]    Embodiments of the inventive concepts disclosed herein have been described with reference to drawings. The drawings illustrate certain details of specific embodiments that implement the systems and methods and programs of the present disclosure. However, describing the embodiments with drawings should not be construed as imposing any limitations that may be present in the drawings. The present disclosure contemplates methods, systems and program products on any machine-readable media for accomplishing its operations. Embodiments of the inventive concepts disclosed herein may be implemented using a computer processor, or by a special purpose computer processor incorporated for this or another purpose or by a hardwired system. 
         [0055]    As noted above, embodiments within the scope of the inventive concepts disclosed herein include program products comprising non-transitory machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media may be any available media that may be accessed by a computer or other machine with a processor. By way of example, such machine-readable media may comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which may be used to carry or store desired program code in the form of machine-executable instructions or data structures and which may be accessed by a computer or other machine with a processor. Thus, any such a connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions comprise, for example, instructions and data which cause processor to perform a certain function or group of functions. 
         [0056]    Embodiments in the inventive concepts disclosed herein have been described in the general context of method steps which may be implemented in one embodiment by a program product including machine-executable instructions, such as program code, for example in the form of program modules executed by machines in networked environments. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular data types. Machine-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represent examples of corresponding acts for implementing the functions described in such steps. 
         [0057]    The foregoing description of embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the subject matter to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the subject matter disclosed herein. The embodiments were chosen and described in order to explain the principals of the disclosed subject matter and its practical application to enable one skilled in the art to utilize the disclosed subject matter in various embodiments and with various modifications as are suited to the particular use contemplated. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the embodiments without departing from the scope of the presently disclosed subject matter.