Abstract:
Multi-beam antenna array for anti jam and anti-spoof protection of GPS satellite data using multiple directional antennas disposed in various orientations jamming or spoofing signals from any direction cannot damage all said directional antennas simultaneously. Each said directional antenna connected to filtering amplifier and to multiple GPS processors for calculating direction of signal arrival. An anti-jam/anti-spoof processor comparing directions of signals arrival with real satellites positions for arrival time from data storage filters signals from jamming or spoofing signals, which are not corresponding to the correct positions stored for each satellite at the transmit time.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field 
         [0003]    The present invention relates generally to anti jam and anti-spoof protection of a receiver and transmitter system, receiving data from multiple directions and transmitting data in multiple directions. More particularly, the present invention relates to a method for anti jamming and anti-spoofing Global Positioning Systems (GPS) satellites including calculating the direction of a satellite signal arrival utilizing a multi-beam directional antenna array and excluding sources not corresponding to the stored data of satellites position at the time of signal arrival. 
         [0004]    2. Background 
         [0005]    The reliability of navigation data is a key element in many situations today. Therefore, a key principle for receiving devices, in particular, GPS receivers, is providing accurate navigation information relating to position and timing. In order to provide accurate information, GPS receivers commonly use broad antenna gain patterns so that all of the satellites above the horizon can be tracked. Unfortunately, a broad antenna gain pattern, increases the susceptibility of GPS receivers to receive jamming signals or spoofing signals. 
         [0006]    A jamming signal transmitted to a GPS receiver is intended to disrupt the receiving capabilities of the receiver and further interrupt the availability of a valid signal at the receiver. A jammed receiver will not be able to decode any signal, nor be able to provide accurate position or time data. Similarly, the transmission of data from a GPS transmitter is inhibited in the presence of a jamming signal. 
         [0007]    On the other hand, spoofing occurs when a signal provides incorrect or misleading information to the receiver. The receiver, in turn, utilizes this signal to calculate inaccurate position and time data. A misleading position results from the successful transmission of a spoofing signal. 
         [0008]    In general, electromagnetic signals have the ability to be recorded. Since these signals can be recorded, a spoofing signal may be the retransmission of a previously recorded signal. This retransmission of a recorded signal makes it difficult to differentiate from a properly transmitted signal. 
         [0009]    Overall, jamming and spoofing, together or separately, can force a GPS system below a pre-determined reliability threshold. Certain scenarios, both from a navigational or military perspective require an extremely high level of accuracy. Examples of such scenarios could include those within the area of aircraft navigation. GPS systems are use in many phases of aircraft navigation, specifically in aircraft positioning, approach and departure paths, course timing as well as vertical positioning. Any interference that reduces from this high level of accuracy could endanger public safety, military actions or government systems. 
         [0010]    Current Controlled Reception Pattern Antenna (CRPA) systems are being used with GPS receivers for electronic protection in electromagnetically-challenged environments. These environments may contain signal interference from natural electromagnetic signals as well as generated electromagnetic signals. These systems are based on simple null steering that adapts antenna weights to steer nulls along the interfering signal direction with no constraint on the antenna response in the direction of a satellite signal. In these systems interfering signals are nulled while the antenna response is constrained in the direction of individual satellite directions. 
         [0011]    CRPA systems have a few main disadvantages when applied to GPS systems: 
         [0012]    1. Every antenna element in planar omni-directional antenna array will be exposed to a jamming signal and each filtering low noise amplifier (FLNA) can be damaged or reaches a certain level of saturation ( FIG. 1 ). Null forming algorithms cannot help in avoiding this because an FLNA can be damaged before a feedback signal will change a receivers element weight. 
         [0013]    2. A planar phased array cannot have a high level gain at low azimuth angles or when a GPS satellite is near the horizon from the perspective of the array. 
         [0014]    3. Omni-directional antennas are very susceptible to jamming or spoofing. With respect to jamming, any positioning of a jamming signal will enter the receiver area of a phased array or single antenna. Similarly, with spoofing, such as with military encryption schemes, a spoofing signal can be recorded and repeat real satellite signals with a delay. Receivers receiving the spoofed signal will calculate improper location and time data. 
         [0015]    With respect to current GPS systems, in light of jamming and spoofing signals, the reliance on GPS data can be compromised under this approach. 
       BRIEF SUMMARY OF THE INVENTION 
       [0016]    Broadly conceptualized, a preferred embodiment of the present invention provides a method and apparatus for identifying, recording and ignoring electromagnetic signal interference. In one advantageous embodiment, a method is provided for an anti-jamming and anti-spoofing protection solution. A protection solution is provided by eliminating jamming and spoofing signals using a signal processor. A protection solution is provided by calculating signals received from a multi-beam, directional antenna array. The multi-beam directional antenna array, comprise of any number of antenna elements greater than or equal to 2, receives all signals, including known signals with predetermined frequency and encryption codes, and those signals that will later be identified as interference. A protection system of a global positioning system signal compares signals using a repository of information storing data of known position, frequency, encryption, and time data. The known data is compared against signals received by the protection system. A matching list of known and desired signals is extracted from all signals received by a protection system. Signals not matching the data stored in an informational repository are identified by the protection system. 
         [0017]    A particular area of applicability for a preferred embodiment of the present invention is a method relating to Global Positioning Systems, (GPS). The multi-beam directional antenna array receives signals from a directed field of view, or collection of GPS satellites, with each satellite having a known navigational position and time position in relation to the multi-beam directional antenna. This directed view allows each antenna within the multi-beam directional antenna array to ignore signals outside said antennas focus. With each antenna focused in a particular direction, the collection of all signals received from a determined field of coverage is divided into subsets for ease of processing. 
         [0018]    A preferred embodiment of the present invention provides a method for calculating aspects of interference signals to identify said signals as jamming signals or spoofing signals. This preferred method comprises: 
         [0019]    receiving electromagnetic signals using a multi-beam directional antenna array; 
         [0020]    identifying characteristics of said electromagnetic signals for classification in categories further comprising jamming signals, spoofing signals and accepted signals; 
         [0021]    calculating the amplitude of each signal within the collection of signals collected by each antenna within a multi-beam directional antenna array; storing electromagnetic signal data of desirable amplitudes for further processing; storing location, amplitude, frequency, encryption and time data of signals outside a desirable amplitude range for further processing as jamming signals; calculating location data and direction of arrival (DOA) data from each signal that succeeded from prior comparison to desirable amplitudes; 
         [0022]    comparing location data and direction of arrival (DOA) data from each remaining electromagnetic signal to a known repository of location data for said signal; processing electromagnetic signals that match location data and direction of arrival (DOA) from of known locations and directions for delivery of accurate position data; and identifying location, direction of arrival (DOA) and time data of electromagnetic signals that do not match known locations from a known repository and identifying said electromagnetic signals as spoofing signals to further identify positional data of sources of spoofing signals. 
         [0023]    In another advantageous embodiment, an apparatus comprising a navigational protection system, a multi-beam directional antenna array, a global positioning system signal processing unit, and an anti jamming signal processor, an anti-spoofing signal processor, an array support structure is disclosed. 
         [0024]    In yet another advantageous embodiment, an apparatus comprising a navigational protection system, a multi-beam directional antenna array, a global positioning system signal processing unit, an anti jamming signal processor, an anti-spoofing signal processor and a dielectric lens layer. 
         [0025]    In yet another advantageous embodiment, an apparatus comprising a navigational protection system, a multi-beam directional antenna array, a global positioning system signal processing unit, an anti jamming signal processor, an anti-spoofing signal processor and a dielectric lens layer wherein the orientation of said multi-beam directional antenna array is hemispherical, extending coverage by way of directional antennas in a spherical form around a set of GPS receivers. Said hemispherical orientation provides multi-beam directional antenna coverage in all directions regardless of the orientation of the device or support structure containing said GPS receivers. This advantageous embodiment may be applicable in area where GPS receivers do not maintain a constant orientation such as in wireless transmit/receive units (WTRUs), cell phones, tablets, PDAs and other devices that are mobile in nature. 
         [0026]    In yet another advantageous embodiment, a method of transmitting data from a multi-beam directional antenna array by identifying antennas within said array which are receiving jamming signals and/or spoofing signals. With the presence of n jamming units, any multi-beam directional antenna array could transmit data with n+1 antenna elements. 
         [0027]    The preferred embodiments are fully disclosed below, albeit without placing limitations thereon and with this in mind, different advantageous embodiments may provide different advantages as compared to other advantageous embodiments. The principles of the present invention are described in detail, through drawing and description in order to best describe the advantageous embodiments, the utility of said present invention and to enable others of ordinary skill in the art to understand the disclosure so as to be able to apply the various embodiments to a particular contemplated use. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0028]    1.  FIG. 1  is a diagram illustrating the electromagnetic signal gain advantage of a directional antenna over that of an omni-directional antenna. 
           [0029]    2.  FIG. 2  represents a diagram illustrating a disadvantageous scenario where each and every antenna of a phased omni-directional antenna array is receiving a jamming signal or a spoofing signal from a single jamming or spoofing unit. 
           [0030]    3.  FIG. 3  represents the advantage of a preferred embodiment of the present invention over the prior art. 
           [0031]    4.  FIG. 4  represents a multi-beam, directional antenna array disposed in a concave surface and the behavior of an advantageous embodiment of the present invention. 
           [0032]    5.  FIG. 5  represents a multi-beam, directional antenna array disposed in a convex surface and the behavior of an advantageous embodiment of the present invention. 
           [0033]    6.  FIG. 6 . represents a flowchart of a process for generating a protection solution in accordance with an advantageous embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    With reference now to the figures, beginning in kind with  FIG. 1 , a diagram illustrating the electromagnetic signal gain advantage of a directional antenna  0104  over that of an omni-directional antenna  0105  is depicted in the context of a global positioning system (GPS)  0101  to demonstrate the advantage over the prior art. Omni-directional antennas  0103  are advantageous in scenarios where a spherical receiving pattern is desirable. However, with the directional antennas  0102  a significant advantage in terms of gain can be achieved. 
         [0035]      FIG. 2  depicts a omni-directional phased array of null steering antennas  0209 . With a system of GPS satellites  0201 ,  0202 , and  0203 , for example, delivering electromagnetic signals of location and time data in signals  0204 ,  0205 , and  0206  respectively, a jamming or spoofing unit  0207  broadcasting a jamming or spoofing signal  208  can effectively saturate each element  0210 ,  0211 ,  0212  of the omni-directional phased array  0209 . A saturation of the omni-directional phased array could cause damage to each element of the omni-directional phased array and subsequently causing damage to the filtering low-noise amplifiers  0213 ,  0214  and  0215 , listening to the broadcast of said signal. Said saturation is highly undesirable and a major disadvantage of the prior art. 
         [0036]    In quantifying the difference between an omni-directional phased array and a multi-beam directional antenna array,  FIG. 3 . offers a comparison of an overall gain advantage by using a multi-beam directional antenna array  0311  over using an omni-directional phased array  0312 . Further,  FIG. 3  depicts an arrangement of GPS satellites  0301 ,  0302  and  0303  transmitting electromagnetic signals  0304 ,  0305  and  0306  respectively. The pattern of gain range of each directional antenna element of the multi-beam directional antenna array is depicted and further describes two separate scenarios for said array. Jamming or Spoofing units  0307 ,  0309  are simultaneously transmitting jamming or spoofing signals  0308 ,  0310  respectively. Said signals are directed toward the multi-beam directional antenna array. Jamming and Spoofing signals are identified by the protection system of the present invention and the multi-beam directional antenna array is still not affected  0315  entirely even if two elements of the multi-beam directional antenna array are affected  0313 . 
         [0037]    In  FIG. 4  a convex support structure arrangement  0419  is depicted utilizing three directional antenna elements  0411 ,  0414 ,  0417  within the multi-beam directional antenna array. A dielectric lens  0410 ,  0413 ,  0416  provides an additional layer of complexity to the reception of the electromagnetic signals. The dielectric lens is constructed of a material that converges or diverges a beam of an electromagnetic signal. The dielectric lens allows an electromagnetic signal that is too great in amplitude for the receiver element to be focused upon said element. This focused electromagnetic signal data is aided by a filtering low-noise amplifier  0412 ,  0415 ,  0418  to provide a sufficient signal for processing to the GPS signal processor and hence the anti jam and anti-spoofing processor of the present invention. A jamming or spoofing unit  0407  which emits an electromagnetic signal  0408  will be unable to affect the receiving abilities of multiple members of the multi-beam directional antenna array  0409  since the directional nature of elements  0414  and  0417  do not receive signals in the direction of the jamming or spoofing signal  0408 . The GPS satellites  0401 ,  0402 ,  0403 , may continue to communicate with the elements of the multi-beam directional antenna array by transmitting signals  0404 ,  0405 ,  0406 . The advantage of the concave structure support element provides a wide coverage angle for the array and receives signals in an expansive direction. An advantage of said coverage is that the low azimuth angle limitation of an omni-directional antenna is overcome by directing an element of said multi-beam directional array in the direction of the horizon. The pattern of coverage  509  of an element of said array could better cover the delivery of a GPS satellite signal from the horizon in relation to the position of said array. 
         [0038]    In  FIG. 5  a convex support structure arrangement  0520  is depicted utilizing three directional antenna elements  0511 ,  0514 ,  0517  within the multi-beam directional antenna array. A dielectric lens  0510 ,  0513 ,  0516  provides an additional layer of complexity to the reception of the electromagnetic signals. The dielectric lens is constructed of a material that converges or diverges a beam of an electromagnetic signal. The dielectric lens allows an electromagnetic signal that is too great in amplitude for the receiver element to be focused upon said element. This focused electromagnetic signal data is aided by a filtering low-noise amplifier  0512 ,  0515 ,  0518  to provide a sufficient signal for processing to the GPS signal processor and hence the anti jam and anti-spoofing processor of the present invention. A jamming or spoofing unit  0507  which emits an electromagnetic signal  0508  will be unable to affect the receiving abilities of multiple members of the multi-beam directional antenna array  0509  since the directional nature of elements  0514  and  0517  do not receive signals in the direction of the jamming or spoofing signal  0508 . The GPS satellites  0501 ,  0502 ,  0503 , may continue to communicate with the elements of the multi-beam directional antenna array by transmitting signals  0504 ,  0505 ,  0506 . 
         [0039]    In  FIG. 6 , a dielectric lens  0601  receives is the first receiving element of an electromagnetic signal which, as described above, focuses said signal upon the antenna element  0602  at a known angle. With a known value focusing said signal upon the antenna element, signals outside the focus of said element can be ignored. A filtering low-noise amplifier  0603  amplifies the gain of a received electromagnetic signal and act to reduce the noise contained within said signal. The signal detector  0604  processes the direction of arrival (DOA), location data and amplitude of the received electromagnetic signal for further processing by the anti jamming decision process  0606  and  0608 . If a signal has a correct amplitude as has been predetermined by a threshold within the system, the signal is identified for further processing  0611 . If a signal does not have a proper amplitude, the signal is identified for further processing as a jamming signal or a spoofing signal  0607 . Once a signal has been properly filtered for correct amplitude, a comparison of the received signal  0608  is conducted against known location data from a repository of information  0605  relating to the correct location of the signal that has been provided. Elements such as direction of location (DOA), location, and time data are compared against known positions. If a received signal matches a known signal  0612 , the signal is processed  0609  for delivery to a GPS receiver. If the comparison of the data in the known repository and the received signal is not a match, the signal is identified as a spoofing signal  0607  and is stored for further processing to determine the location of said spoofing signal.