A New Automatic Frequency Correction Technique for Narrow Band Satellite Communication Systems

Abstract

A new approach of an automatic frequency correction technique for narrow band systems in satellite communication is presented. The proposed technique uses a digital frequency discriminator, quite different from the conventional one which uses the well known phase locked loop (PLL). This technique can be employed in the user terminals of the half/full duplex satellite network to obtain a stable transmit frequency without the need of a continuous frequency reference by locking the transmit frequency to that received from the master station through the satellite. The principle of operation and corresponding equipment configuration are described. The maximum theoretical error possible in this approach is derived through analysis of the loop performance. This technique is applied to an operational low bit rate communication system and the experimental results are in close proximity with the theoretical values.

Indexing terms:

• Automatic frequency correction (AFC)
• Narrowband
• Satellite communications
• Digital frequency discriminator