Carrier phase synchronisation for a burst mode digital modem
N.I. Tsabieris · 1995
This paper is concerned with the carrier phase synchronisation aspect of a digital modem. The modem is a burst-mode digital modem, and as such it requires some form of `acquisition' or `locking on' system. At the start of a message burst, phase reversals (training sequence) are sent in groups of two resulting in two pairs of in-phase and quadrature components received in 16 μsec in one quadrant and then two pairs in the opposite quadrant. This 32 kHz signal lasts for 12 cycles before a unique word (UW) is sent to identify the start of the message. For a message to be considered the UW must be detected with a close match and since the total burst length is between 2 K and 10 K, the phase tracking algorithm must be effective very early in the burst (first 2048 data symbols), because at this period the system is at its most vulnerable state, since the UW must be correctly detected. A novel carrier phase synchronisation technique has been developed employing the expanding-memory polynomial filter algorithm. (11 pages)