Rapid Acquisition/Reacquisition Capability in a Tactical AJ Modem

For a spread spectrum modem, achieving rapid acquisition and reacquisition under heavy jamming requires accurate knowledge of time and frequency and of satellite range and range rate. The lack of such information in mobile terminals during wartime conditions results in severe limitations in acquistion capability. This paper describes how the Harris AJ/Control Modem for the Ground Mobile Forces network uses the satellite beacon PN code state and carrier frequency as network time and frequency standards, respectively. The paper explains the use of satellite ephemeris data, normally unavailable to tactical terminals, to provide fixed-terminal acquisition capability in a low-cost mobile terminal.