Patent Application
20130222171
The disclosure relates to a radar systems, such as a device for generating a three dimensional null region between an electromagnetic source and a target.
The rapidly expanding development of wind-based energy across the world (most notably in the U.S. and Europe) has resulted in the deployment of thousands of radar-reflecting wind-turbines that interfere with Air Defense, Air Traffic Control (ATC), and Doppler Weather radars, and other airborne or ground based systems. The proliferation of wind turbines has created large volumes of airspace where radar coverage is negatively impacted, with potentially severe impact to homeland defense, storm alert/prediction capability, and flight tracking systems.
In the U.S., efforts are underway to allow for the development of more wind farms while also reducing or eliminating the adverse effects wind turbines can have on radar coverage, in areas such as homeland defense storms alert/prediction capability, and flight tracking systems. For example, one proposed solution manages the development requests from windfarm developers to assess, and mitigate if required, windfarm developments. Moreover, impact studies are prepared by the U.S. government, research organizations, and educational institutions in an effort to determine solutions for mitigating the effects of wind farms.
Known wind-turbine interference mitigation efforts to date are processor-based solutions focusing primarily upon developing hardware and software modifications, which employ advanced digital signal processing techniques to compensate for radar interference produced by the wind-turbines.
An exemplary interference nulling system is disclosed, comprising: a EM based (e.g., radar) system for transmitting EM signals and receiving return signals reflected from a target; and a nulling device having a surface for diffracting/blocking the transmitted radar signals to electromagnetically obscure the target, wherein the nulling device is sited between the EM transmitter system and the target, e.g., in a blanking range of a radar system, and the nulling device per se. In this way, the 2-way energy path between a radar system and a wind turbine, for instance, can be effectively blocked, by creating a 3-D dead zone.
The exemplary embodiments of the disclosed systems and methods can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of exemplary embodiments of the disclosed system. Moreover, in the figures, like reference numerals designate corresponding parts through the different views.
The system for producing a null region, which can be viewed as an electromagnetic (EM) shadow, between an electromagnetic source and a target will now be described by reference to the accompanying drawings in which like elements are described with like figure numbers. It should be noted that the claimed invention is not limited to these particular embodiments but rather fully encompasses variations and modifications, which may occur to those skilled in the art.
The exemplary nulling device can be configured to use a combination of obstructive and destructive interference techniques of diffraction theory, and in particular Fresnel-Zone Diffraction Theory, which has the potential to establish a precisely-structured three-dimensional (3D) null region, if desired. The null region produced by the nulling device electromagnetically obscures a target at a specified distance. For example, using the obstructive and destructive properties, the nulling device diffracts (e.g., blocks) and cancels the transmitted radar signals, thereby preventing radar waves from illuminating or reaching the target.
As shown in
In accordance with an exemplary embodiment, the nulling device can include one or more metal plates, such as aluminum or any other suitable material as desired. The metal plate can be covered in radar-absorbing material to obtain a specified level of attenuation as desired. For example, the metal plate may be covered with X-hand radar absorbing material which can provide approximately 20 dB attenuation of the incident radar signals. The height and width of the metal plate can be determined by a geometry of the target and/or a geometry of the site at which the nulling device is located. This determination is based on a specified or desired effective attenuation of a main beam radiated by the radar system. The metal plate should be large enough to completely block the optical line-of-sight between the radar system and the target.
As shown in
In another exemplary embodiment, the singular nulling device concept can be expanded to include an array of nulling devices or a system of nulling devices that incorporates the precision-nulling properties exhibited by the singular nulling device. A system of nulling devices can be used to selectively eliminate radar returns from a plurality of distant targets, such as a plurality of wind-turbines simultaneously.
In addition to the static placement of a nulling device as described above, other exemplary embodiments include a nulling device or system of nulling devices for creating 3D EM (e.g., RF) null regions between objects and/or EM sources that are in motion, and in environments requiring temporary EM obscuration. For example, a single nulling device can be attached to a vehicle or other moving object so that at any moment it generates the location of the nulling device satisfies the two conditions for establishing the null region. In addition, an exemplary system of nulling devices can be strategically disposed between a radar system and target, where either of the radar system and target can be in motion. The siting of the system of nulling devices can be arranged such that at point in time of operation of the radar system, at least one of the nulling devices in the system can generate a null region with respect to an associated target.
Exemplary nulling devices as disclosed herein, can be stand-alone devices and/or systems that are external to the radar system, and can advantageously produced at low-cost when compared to known designs, which specify modifications the hardware and/or software of the radar system.
Though not necessarily a benefit of all embodiments, compared to conventional mitigation techniques, the present nulling system can selectively blank only Line-of-Sight (LOS) returns, whereas other techniques can eliminate radar returns from all resolution cells with the same range-azimuth as a wind-turbine, for instance, thereby creating potential blind spots in useful airspace. Further, the nulling system allows full-use of navigable airspace, can be set up to affect only unimportant, low-altitude/clutter returns, is comparatively easy to develop and quick to install, does not require modification of radar or wind-turbine systems or site restrictions, is dependable, low cost and scalable.
While the invention has been described with reference to specific embodiments, this description is merely representative of the invention and not to be construed as limiting the invention. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims. For instance, the exemplary embodiment is a radar system, but other EM based systems could benefit from this technology, such as protecting an RF antenna from a particular RF noise source.
| Number | Date | Country | |
|---|---|---|---|
| 61586011 | Jan 2012 | US |
