Doppler shift compensation in elliptical-orbit satellite land mobile communications systems

One consequence of the use of elliptical orbits is the existence of Doppler shifts in all satellite/ground link signals due to the finite (varying) velocity of the satellite. These Doppler shifts, which occur on both the feeder links and the links with the land mobiles must be accurately compensated out in order to avoid band overlap, loss of available spectrum and other frequency management problems. The requirements for compensation of the Doppler frequency shift sustained in such land mobile communications systems using satellites in elliptical orbits are discussed. The frequency compensation requirements are defined and the fundamental implementation options for Doppler compensation discussed in detail. Conclusions are drawn concerning the most favourable means of implementation