Patent Description:
A traditional airborne weather radar system antenna beam may be tilted toward the ground to attempt to illuminate display doppler returns from hazardous weather near the ground and intended landing airfield. However, while tilted downward, these traditional radars also display strong ground clutter which may preclude display of an actual weather threat.

For autonomous operation, detecting hazardous weather without flight disruption may be useful. Without further information, most operational directives may mandate discontinuing the landing to avoid any microburst threat. This may include a false microburst warning causing increased fuel consumption for additional flight time. For an electronically scanned array, ground clutter echoes may be exacerbated due to the higher sidelobe content.

Some methods of ground clutter suppression may be computationally extensive and require heavy, expensive computational assets carried on board the aircraft which may be cost prohibitive. Some systems may compute a ground clutter position via a space time adaptive processing but require extensive processing power and assets to perform the task.

Therefore, a need remains for a system and related method which may overcome these limitations and provide a lightweight novel solution onboard the aircraft enabling the weather radar to function as a sensor to minimize ground clutter and accurately display hazardous microburst weather phenomena. <CIT> relates to ground clutter rejection in weather radar.

In one aspect, embodiments of the inventive concepts disclosed herein are directed to a system for discriminating a ground clutter return from a weather return, as defined in claim <NUM>. The system may comprise a weather radar onboard an aircraft, the weather radar including an electronically scanned array (ESA) antenna, the weather radar configured for reception of a weather radar data, the ESA having a plurality of elements. The system may further include a weather communication interface configured for receiving the weather radar data and configuring the weather radar data for recognition by an operator of the aircraft and a controller operatively coupled with each of the ESA and the weather radar.

For control, the system may include a tangible, non-transitory memory configured to communicate with the controller, the tangible, non-transitory memory having instructions stored therein that, in response to execution by the controller, cause the controller to carry out each task of the system for discriminating a ground clutter return from a weather return.

In function, the controller may receive the weather radar data and identify a ground clutter return within the received weather radar data based on a characteristic of the weather radar data associated with the ground clutter return. The system may determine a location relative to the aircraft of the ground clutter return based on the identification and command the ESA to adaptively adjust an amplitude and a phase of an element of the plurality of elements to manipulate <NUM>) a far field radiation pattern and <NUM>) a side lobe associated with the ESA, the adaptive adjustment creates a null associated with the ground clutter return, the adaptive adjustment maintains a signal to noise ratio (SNR) sensitivity of the weather radar to receive a weather return. The system may receive the weather return and display the weather return to the operator of the aircraft.

A further embodiment of the inventive concepts disclosed herein may include a method for discriminating a weather radar return from a surface return, as defined in claim <NUM>. The method may comprise receiving a weather radar data from an electronically scanned array (ESA) associated with a weather radar onboard an aircraft, the ESA having a plurality of elements and identifying a ground clutter return within the received weather radar data based on a characteristic of the weather radar data associated with the ground clutter return.

The method may further include determining a location relative to the aircraft of the ground clutter return based on the identification and adaptively adjusting an amplitude and a phase of an element of the plurality of elements of the ESA to manipulate a far field radiation pattern and a side lobe associated with the ESA, the adaptive adjusting creates a null associated with the ground clutter return, the adaptive adjusting maintains a signal to noise ratio (SNR) sensitivity of the weather radar to receive a weather return. The method may also include receiving the weather return and displaying the weather return to the operator of the aircraft.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the inventive concepts as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the inventive concepts and together with the general description, serve to explain the principles of the inventive concepts disclosed herein.

In the drawings in which.

This is done merely for convenience and to give a general sense of the inventive concepts, thus "a" and "an" are intended to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

Broadly, embodiments of the inventive concepts disclosed herein are directed to a system and related method for applying an adaptive adjustment or taper to an electronically scanned array (ESA) weather radar based on feedback from the weather radar. To minimize ground clutter and enable the ESA to display hazardous weather phenomena, the system adaptively adjusts amplitude and phase of ESA elements to adjust the far field pattern shape and sidelobes to maintain a desirable signal to clutter ratio. The system identifies ground clutter as a strong ground return over several azimuths depending on the radar beamwidth. Once the system IDs the ground clutter, it adaptively adjusts on receive for for the upcoming azimuths. This system selectively suppresses sidelobe echoes while maintaining the signal to noise (SNR) for weather targets. The system adaptively adjusts in real time as well as adjusting using precomputed historically accurate tapers stored in memory.

Referring to <FIG>, a diagram of a system for discriminating a ground clutter return from a weather return in accordance with an embodiment of the inventive concepts disclosed herein is shown. Generally, a system overview <NUM> for the system for discriminating a ground clutter return from a weather return may include a weather radar <NUM> onboard an aircraft, the weather radar <NUM> may include an electronically scanned array (ESA) antenna <NUM>. Here, the weather radar <NUM> may be configured for reception of weather radar data via a plurality of elements incorporated within the ESA <NUM>.

In one embodiment of the inventive concepts disclosed herein, the system for discriminating a ground clutter return from a weather return <NUM> may be useful for receiving weather radar data associated with weather <NUM> but also may receive weather radar data which includes returns from ground clutter <NUM>.

In one embodiment of the inventive concepts disclosed herein, to properly format the weather radar data for a variety of users, a weather communication interface <NUM> may be configured for receiving the weather radar data and configuring the weather radar data for recognition by an operator of the aircraft. Here, some operators may include a manned aircraft wherein a flight deck display <NUM> may be appropriate, an unmanned aircraft system (UAS) where a mission processor <NUM> and an autonomous flight control computer (FCC) may be appropriate end use operators of the weather radar data.

In one embodiment of the inventive concepts disclosed herein, for control, the system for discriminating a ground clutter return from a weather return <NUM> may incorporate a controller <NUM> operatively coupled with each of the ESA <NUM> and the weather radar <NUM>. A tangible, non-transitory memory <NUM> may be configured to communicate with the controller <NUM>, the tangible, non-transitory memory <NUM> may have instructions stored therein that, in response to execution by the controller <NUM>, may cause the controller <NUM> to carry out each function of the system for discriminating a ground clutter return from a weather return <NUM>.

In general terms, one function of the system for discriminating a ground clutter return from a weather return <NUM> may include use of the ESA <NUM> and the weather radar <NUM> as a sensor enabling the controller <NUM> to discern ground clutter returns from actual hazardous weather returns (e.g., microburst, windshear, etc.). The controller <NUM> may dynamically adjust the amplitude and phase on the ESA <NUM> aperture thereby dynamically adjusting the far field radiation pattern to minimize the ground clutter and receive the desired returns from the target of weather of interest (microburst).

The system for discriminating a ground clutter return from a weather return <NUM> may operate to minimize an impact from strong sidelobes while maintaining a detectability of the weather radar <NUM> to accurately display actual weather and in particular, the relatively small signal associated with a microburst. Employing a closed loop feedback from the ESA <NUM> to the controller <NUM>, the controller <NUM> may identify a strong ground return and actively apply a taper (see below) on the ESA <NUM> for a subsequent scan angle to minimize the strong signal from that ground target.

In one embodiment of the inventive concepts disclosed herein, in function, the controller <NUM> may receive the weather radar data from the ESA <NUM> and identify a ground clutter return within the received weather radar data based on characteristics of the weather radar data associated with the at least one ground clutter return. Here, one characteristic of a ground clutter return may include a radar return of greater strength than a surrounding radar return over a sequence of azimuths. Unlike actual weather radar returns which may be isolated in azimuth (e.g., approximately four degrees), ground clutter <NUM> may present as a very strong radar return over multiple azimuths. Here, the controller <NUM> may identify the ground clutter from set of rules stored within the memory <NUM> to accurately ID the ground clutter.

In one embodiment of the inventive concepts disclosed herein, the controller <NUM> may determine a location relative to the aircraft of the ground clutter return based on the identification. The relative position of the ground clutter may aid the controller <NUM> in follow on steps to adjust the ESA based on the position of the identified ground clutter <NUM>.

To eliminate the ground clutter (e.g., partially as well as over a plurality of azimuths), the controller <NUM> may command the ESA to adaptively adjust an amplitude and a phase of the individual elements incorporated within the ESA. As a well-known spatial relationship may exist between the amplitude and phase on a radar aperture and a far field radiation pattern of the radar, in controlling or applying a taper to the amplitude and phase of each element, the controller <NUM> may also actively control the far field radiation pattern of the ESA <NUM>.

In one embodiment of the inventive concepts disclosed herein, the controller <NUM> may command a non-uniform amplitude excitation stronger in the center of the ESA <NUM> then gradually reducing in strength toward the edges of the array to taper the ESA <NUM> and affect the far field radiation pattern as well as the side lobes. In embodiments, the excitation may be on the order of approximately <NUM> to <NUM> dB that significantly reduces the side lobe levels in the far field. Ignoring any error, a uniform illumination of a rectangular aperture may have approximately a <NUM> dB peak side lobe where the controller <NUM> may suppress a side lobe down past <NUM> dB by employing the non-uniform amplitude on the aperture.

In other embodiments, the controller <NUM> may affect the far field radiation pattern by adjusting the phase. In one embodiment, in response to the weather radar data, the controller <NUM> may position a null based on a non-uniform phase excitation of elements within the ESA <NUM>. Here, the controller may dynamically adjust the amplitude and phase as a function of scan and as function of radar response to a stimulus to minimize the return of the ground clutter.

Those skilled in the art of radar performance may comprehend an amplitude taper as a textbook antenna modification for various performance. Various parameters to perform a taper may include adjustment of typically peak to edge illumination differences in dB may be from approximately <NUM> dB to approximately <NUM> dB, as a tradeoff may exist between the side lobe level and desired beamwidth.

In embodiments, the controller <NUM> may vary each of the amplitude and phase to attain a desired performance. Here, one exemplary taper of the ESA may include an illumination difference of approximately uniform to a <NUM> dB illumination difference with <NUM> states across the ESA <NUM> from the center to the edge of the ESA <NUM>.

In controlling the ESA <NUM> via adaptively adjustments, the controller <NUM> may manipulate the far field radiation pattern of the ESA as well as one or more side lobes associated with the ESA. The adaptive adjustment may create and steer one or more nulls associated with the ground clutter return to maintain a signal to noise ratio (SNR) sensitivity of the weather radar <NUM> enabling it to receive actual weather return.

In one embodiment of the inventive concepts disclosed herein, the controller <NUM> may command a plurality of nulls to discern an associated plurality of ground clutter returns <NUM>. Limited by element configuration of the ESA <NUM>, the controller <NUM> may steer the plurality of nulls to any azimuth capable by the ESA <NUM>.

The controller <NUM> may then command a reception of the actual weather return and display the at least one weather return in a format desired by the operator of the aircraft.

Referring now to <FIG>, diagrams of before and after ESA adaptive adjustment in accordance with an embodiment of the inventive concepts disclosed herein is shown. A diagram <NUM> of a weather radar display <NUM> configured for human recognition may detail a result of the system for discriminating a ground clutter return from a weather return <NUM> function.

In one embodiment of the inventive concepts disclosed herein, the controller <NUM> may identify a series of ground clutter returns <NUM> and function to suppress the ground clutter returns to display actual weather returns <NUM>. In this manner, the weather radar display <NUM> may present to the human operator accurate weather data. Similarly, should the system for discriminating a ground clutter return from a weather return <NUM> be incorporated within the UAS, the controller <NUM> may command the interface <NUM> to configure the actual weather returns <NUM> for machine consumption and avail the data to, for example, the UAS autonomous FCC <NUM>.

Referring now to <FIG>, a diagram of a logic flow exemplary of an embodiment of the inventive concepts disclosed herein is shown. One logic flow <NUM> may indicate a function the controller <NUM> may incorporate to accurately discern actual weather <NUM> from the ground clutter <NUM>.

A step <NUM> may include receive weather radar data from the weather radar <NUM> while a query <NUM> may inquire if the controller <NUM> may identify ground clutter within the received weather radar data. A step <NUM> may include a determination of a relative location of the ground clutter relative from the aircraft. A step <NUM> may include the controller <NUM> commanding a non-uniform weights taper of the amplitude control of one or more elements of the ESA <NUM> while a next query <NUM> may inquire if the ground clutter has been eliminated. If not, the logic may pass to a step <NUM> in which the controller <NUM> may command a non-uniform weights taper of the phase of the ESA <NUM> followed by another query <NUM> if the ground clutter has been eliminated.

Should the ground clutter remain, the logic may pass to a step <NUM> wherein the controller <NUM> may command a taper of non-uniform weights in both amplitude and phase to suppress side lobes below the main beam (see <FIG>). Conversely, should one of these tapers be successful at eliminating the ground clutter, or if ground clutter was not present at the query <NUM>, the logic may pass to steps <NUM> to receive, step <NUM> to format, and a step <NUM> to display the received weather radar data.

Referring now to <FIG>, a diagram of an exemplary antenna pattern prior to ESA adaptive adjustment in accordance with one embodiment of the inventive concepts disclosed herein is shown. One exemplary ESA radiation pattern <NUM> may result from a <NUM> element ESA <NUM> with <NUM> dB taylor weights. The pattern <NUM> may indicate a main lobe <NUM> and one or more side lobes <NUM> Here, a highest sidelobe level of <NUM> dB below the main lobe may be realized with a normal operation of the weather radar <NUM>.

Referring now to <FIG>, a diagram of an exemplary antenna pattern after steering a null in accordance with one embodiment of the inventive concepts disclosed herein is shown. One pattern <NUM> may indicate an antenna pattern after the controller <NUM> may function to steer a null using non-uniform complex weights. As can be seen, the suppressed sidelobes <NUM> in the area of interest (within <NUM> degrees of the main beam <NUM>) are now at least <NUM> dB below the main lobe <NUM>. This suppression may eliminate the return power from any undesired ground clutter <NUM>.

Here, the relationship is clear between the peak of the main beam <NUM> and the suppressed side lobes <NUM> proximal with a perimeter of the main beam <NUM> compared with unchanged side lobes <NUM> oppositely proximal with the main beam <NUM>. Embodiments herein may function to reduce side lobes <NUM> adjacent to the main beam <NUM> to suppress identified ground clutter returns <NUM>. Minimizing the adjacent side lobes <NUM> may enable the controller <NUM> to accurately display the hazardous weather to the operator.

In one embodiment of the inventive concepts disclosed herein, the controller <NUM> may employ a Taylor taper stored within the memory <NUM> to enable the overall system to efficiently perform. The controller <NUM> may command an adaptive adjustment selected from a list of precomputed historically successful tapers stored within the memory <NUM> as well as determined by the controller <NUM> upon reception of the weather radar data. The pre-stored asymmetrical beams may be used as a starting point for a dynamically optimized beam from that starting point, if required.

For example, the controller <NUM> (or a previous controller <NUM>) may determine a taper pattern which may be able to successfully suppress a majority of look down ground clutter situations. Where the controller <NUM> may experience and identify a similar ground clutter pattern, the controller <NUM> may reference the stored Taylor within the memory <NUM> and taper the ESA <NUM> based on the stored Taylor. In this manner, the controller <NUM> may be able to handle a majority of cases of down looking wind shear detection based on the a priori stored information.

In this manner, the controller <NUM> may increase control speed with stored information with less calculation during operation. In one example, a plurality of beam states may be stored within the memory <NUM> allowing for nearly instantaneous access.

Conversely, should the radar detect no ground clutter <NUM> and detect heavy weather with great doppler signature, the controller <NUM> may command a standard beam width without steering any nulls. Here, the controller <NUM> may command a default state of the ESA <NUM> using a desired signal to noise beamwidth which may yield accurate weather return and display.

In commanding one or more tapers or steering one or more nulls, the controller <NUM> may cause a reduction in weather detection performance. In commanding an asymmetric or windshear taper, the ESA <NUM> may be optimized for that radar mode which may not be the best mode for weather radar detection. Here, the controller <NUM> may command a symmetric taper that the weather radar <NUM> may employ for a majority of operations while incorporating asymmetric tapers as the radar identifies the undesirable ground clutter <NUM>.

Referring now to <FIG>, a diagram of an exemplary horizontal plane adjustment in accordance with one embodiment of the inventive concepts disclosed herein is shown. A tapered ESA side view <NUM> may detail one embodiment herein.

In one embodiment of the inventive concepts disclosed herein, the controller <NUM> may function to adaptively adjust the ESA <NUM> to suppress a side lobe radiating vertically below a main lobe of the ESA, a side lobe radiating horizontally from the main lobe of the ESA, and a side lobe radiating omnidirectionally from the main lobe of the ESA.

As microburst action may be primarily in a downward elevation, weather radar <NUM> performance in a look down situation may be advantageous to flight safety. The controller <NUM> may command a taper to allow increased upper side lobes <NUM> resulting in decreased lower side lobes <NUM> to realize a deeper null looking low toward the area of greatest microburst doppler. The controller <NUM> may command a reduction in an ESA <NUM> sensitivity in an area vertically above the main lobe <NUM> to increase an ESA sensitivity in an area vertically below the main lobe <NUM>.

Here, the controller <NUM> may taper in this manner to effect a a positive trade because of the location of the aircraft descending on a glideslope near the surface. Here as well, a radar range may be relatively short since distant weather (e.g., on the far side of the landing runway) may not be a factor.

This positive trade in upper versus lower performance may be a compromise in order to perform a specific task critical to this specific radar mode. This positive trade may be beneficial to the overall safety of the aircraft given the possible consequence of flying through a microburst.

The system for discriminating a ground clutter return from a weather return <NUM> may function to steer one or more of the null in a specific direction using a relatively architecturally simple low pulse repetition frequency (PRF) system radar. Systems herein may exploit a fast adaptability of the ESA <NUM> to perform the desired task. Here, some operators may require as simple a solution as possible due to cost and weight requirements of a weather radar <NUM> incorporated within a commercial aircraft versus the cost and performance of a sophisticated radar designed for a fighter aircraft.

Embodiments herein may extend the performance envelope of the weather radar <NUM> in a very cost-effective way. As the ESA <NUM> may be able to quickly change the beam on the order of <NUM> of microseconds, changing the characteristics of the beam to fit the desired performance may benefit an operator.

Referring now to <FIG>, a diagram of a method flow associated with one embodiment of the inventive concepts disclosed herein is shown. A method flow <NUM> for discriminating a weather radar return from a surface return may include, at a step <NUM>, receiving weather radar data from an electronically scanned array (ESA) associated with a weather radar onboard an aircraft, the ESA having a plurality of elements and, at a step <NUM>, identifying a ground clutter return within the received weather radar data based on a characteristic of the weather radar data associated with the ground clutter return.

A step <NUM> may include determining a location relative to the aircraft of the ground clutter return based on the identification and a step <NUM> may include adaptively adjusting one of: an amplitude and a phase of an element of the plurality of elements of the ESA to manipulate a far field radiation pattern and a side lobe associated with the ESA, the adaptive adjusting creates a null associated with the ground clutter return, the adaptive adjusting maintains a signal to noise ratio (SNR) sensitivity of the weather radar to receive a weather return. A step <NUM> may include receiving the weather return, and a step <NUM> may include displaying the weather return to the operator of the aircraft.

As will be appreciated from the above description, embodiments of the inventive concepts disclosed herein may provide a lightweight novel solution onboard the aircraft enabling the weather radar to function as a sensor to minimize ground clutter and accurately display hazardous microburst weather phenomena.

Claim 1:
A system for discriminating a ground clutter return from a weather return, comprising:
a weather radar (<NUM>) onboard an aircraft, the weather radar including an electronically scanned array, ESA (<NUM>), antenna, the weather radar configured for reception of a weather radar data, the ESA having a plurality of elements;
a weather communication interface (<NUM>) configured for receiving the weather radar data and configuring the weather radar data for recognition by an operator of the aircraft;
a controller (<NUM>) operatively coupled with each of the ESA and the weather radar;
a tangible, non-transitory memory (<NUM>) configured to communicate with the controller, the tangible, non-transitory memory having instructions stored therein that, in response to execution by the controller, cause the controller to:
receive the weather radar data;
identify at least one ground clutter return within the received weather radar data based on at least one characteristic of the weather radar data associated with the at least one ground clutter return;
determine a location relative to the aircraft of the at least one ground clutter return based on the identification;
command the ESA to adaptively adjust at least one of: an amplitude and a phase of at least one element of the plurality of elements to manipulate <NUM>) a far field radiation pattern and <NUM>) at least one side lobe associated with the ESA, the adaptive adjustment creates at least one null associated with the at least one ground clutter return, the adaptive adjustment maintains a signal to noise ratio (SNR) sensitivity of the weather radar to receive at least one weather return, the adaptive adjustment being a non-uniform amplitude and/or phase excitation of each element of the plurality of elements;
receive the at least one weather return; and
display the at least one weather return to the operator of the aircraft.