Method and apparatus to retrofit legacy global positioning satellite (gps) and other global navigation satellite system (gnss) receivers

Abstract

In one embodiment, the present invention includes a method of receiving and decoding military L2 or L1 P(Y) or M-Code signals and re-transmitting these in real-time as legacy L1-C/A signals. The decoding process of the P(Y) or M-code is done through the programming by the user of secret keys into an embodiment of this invention. These military code signals are then decoded into standard PVT/PNT information which are typically transmitted on an industry standard serial port and format, which are then re-encoded using a real-time GPS simulator sub-system as legacy L1-C/A code signals, and transmitted to the output of the embodiment of this invention as a standard antenna signal. This output signal could be made compatible with any commercial L1-C/A code GPS receiver, and may thus be decoded by the GPS receiver as if the signals had been received directly from the Satellites. In one application of this embodiment of this present invention the legacy GPS receiver does not know the difference and cannot differentiate between signals generated by this embodiment of the present invention versus true GPS satellite signals received by a real GPS antenna. This embodiment of the present invention allows efficient replacement of legacy GPS antennae without having to change any of the system, setup, cabling, or programming of the legacy GPS receiver system. Another embodiment of this present invention may receive Glonass, BeiDou, or Galileo signals, and output legacy GPS signals to allow a glueless retrofit of legacy GPS receivers to Glonass, BeiDou, or Galileo compatibility.