Method and apparatus for establishing and maintaining frame synchronization in a satellite communication system

An apparatus for establishing frame synchronization in a satellite communication system which receives a modulated signal having frames, a unique word and data being multiplexed in each of said frames, said apparatus comprising:

• means for demodulating said modulated signal and providing a demodulated signal, said demodulated signal including said unique word;
• signal detecting means for comparing the signal power of said demodulated signal with a threshold signal and providing a detection signal;
• means for detecting said unique word from said demodulated signal and providing a unique word signal;
• inhibiting means for providing, in accordance with said detection signal, one of said unique word signal and an inhibited signal when an actual communication signal is not detected as an output signal;
• and
• means for establishing frame synchronization in accordance with said output signal when said unique word signal is provided as said output signal by said inhibiting means.

An apparatus for establishing frame synchronization in a satellite communication system which receives a modulated signal having frames, a unique word and data being multiplexed in each of said frames, said apparatus comprising:

• a demodulator for demodulating said modulated signal and providing a demodulated signal, said demodulated signal including said unique word;
• a signal detector for comparing the signal power of said demodulated signal with a threshold signal and providing a detection signal;
• a selector for providing, in accordance with said detection signal, one of said demodulated signal and fixed data as a selected signal;
• and
• a frame synchronizing circuit for detecting said unique word from said selected signal when said demodulated signal is provided as said selected signal by said selector, and establishing frame synchronization based on said unique word.

An apparatus for establishing frame synchronization in a satellite communication system which receives a modulated signal having frames, a unique word and data being multiplexed in each of said frames, said apparatus comprising:

• a demodulator for demodulating said modulated communication signal and providing a demodulated signal, said demodulated signal including said unique word;
• a signal detector for comparing the signal power of said demodulated signal with a threshold signal and providing a detection signal;
• a circuit for detecting said unique word from said demodulated signal and providing a unique word signal;
• an inhibiting circuit for providing, in accordance with said detection signal, one of said unique word signal and an inhibited signal as an output signal;
• and
• a frame synchronizing circuit for establishing frame synchronization in accordance with said output signal when said unique word signal is provided as said output signal by said inhibiting circuit.

A method for establishing frame synchronization in a satellite communication system which receives a modulated signal having frames, a unique word and data being multiplexed in each of said frames, said method comprising the steps of:

• demodulating said modulated signal which has been received to provide a demodulated signal;
• comparing the signal power of said demodulated signal with a threshold signal and providing a comparison signal;
• detecting said unique word and, in accordance with said comparison signal, establishing and maintaining frame synchronization based on said unique word;
• and
• discontinuing frame synchronization in accordance with said comparison signal.

A method for establishing frame synchronization in a satellite communication system which receives a modulated signal having frames, a unique word and data being multiplexed in each of said frames, said method comprising the steps of:

• demodulating said modulated signal which has been received to provide a demodulated signal;
• comparing the signal power of said demodulated signals with a threshold and providing a comparison signal;
• detecting said unique word;
• providing, in accordance with said comparison signal, one of said unique word and an inhibited signal as a first signal;
• establishing and maintaining frame synchronization in accordance with said unique word when said unique word is provided as said first signal;
• and
• discontinuing frame synchronization when said inhibited signal is provided as said first signal.