Signal Space Solutions for GPS Interference

The goal of beamforming is to allow desired signals to be received and unwanted signals to be rejected. Conventional array processing methods are based on constructing a beampattern that has good reception in the direction of the desired signal and good rejection in the direction of the undesired signal. These methods, commonly called Controlled Radiation Reception Pattern (CRPA) offer some mitigation but are not able to satisfy 10 USC §2281, since main lobe and sidelobe leakage is problematic with small arrays and high-powered interference.  This is called the GPS denial problem. An alternative approach is presented in this proposal where all signals are accounted for in a signal space. An attractive feature of this approach is that all the signals are in their own dimension and are naturally separated or decoupled in this space.  The mathematical basis of this approach is that the signal vector is mapped onto the array vector due to various time delays.  Inverting this process using the Moore-Penrose inverse yields the signal vector from the measured array vector.  The valid GPS signals are now separated from the interference signal.  Examples of separated signals are given in this proposal. The proposed Phase I work involves applying this approach to various geometry and interference simulations.  7-element antenna arrays are common and best.  However, 4-element and 3-element antenna arrays are also used and will be simulated.  These smaller arrays are more susceptible to interference using CRPA methods, but signal space methods can provide complete separation of valid GPS signals from high power interference.