GPS receiver with extended security

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) FIG.
1 is an overview illustration of the operation of secure GPS receiver system 10 according to the present invention in which SAASM GPS Receiver 12 processes signals received from satellites via antenna 14 to produce point position solution 16.
The signals and data within SAASM GPS Receiver 12 may be secure while point position solution 16 may be non-secured data.
SAASM GPS Receiver 12 may be of any convenient configuration suitable for protecting the data to be secured and may in particular be a receiver configured in accordance with the SAASM specification.
A generally conventional GPS receiver would include an RF processing section 28, responsive to signals received from satellites by antenna 14, to apply signals to multiple satellite tracking channels, such as satellite tracking channels 30, 32, 34 and 36 each of which tracks signals from actual satellites using secured data including modulation codes and satellite position information.
The satellite tracking channels typically provide range and satellite position information to a processing unit, such as Position Computation 38, which produces point position solution 16 by determining what position on earth would have those ranges to satellites in those positions, by for example, providing a least squares solution.
Point position solution 16 is applied to Converter 18 which processes point position solution 16 to produce a plurality of synthetic satellite data such as synthetic satellite position and range information 20, 22, 24 and 26 for synthetic satellites SSV#1, SSV#2, SSV#3 and SSV#4.
The synthetic satellite position and range information is unclassified data which carries all the navigation information and accuracy inherent in the processing provided by SAASM GPS Receiver 12 but does not compromise the security of the satellite position, codes or other data secured within SAASM GPS Receiver 12.
The synthetic satellite position and range information from Converter 18 is applied to user equipment 40 which may for example be an inertial navigation system or other equipment typically tightly coupled to the GPS receiver and therefore to be used with satellite position and range information