Tuning system for achieving quick acquisition times for a digital satellite receiver

A method of controlling a tuner which receives a plurality of RF signals associated with respective transponders of a satellite and provided by a frequency conversion unit and which produces a carrier signal bearing information corresponding to a tuned one of said RF signals, said RF signals having frequencies with nominal values but being susceptible of being offset from the nominal values, said tuner including a local oscillator (911) having a frequency controlled in accordance with digital tuning representative digital words to tune one of said RF signals;

• said method comprising the steps of:
• storing digital nominal frequency representative words corresponding to the nominal frequency values of respective ones of said RF signals;
• storing digital offset representative words corresponding to respective ones of said RF signals;
• when a RF is selected for tuning, combining the nominal frequency representative word and the offset representative word for said selected RF signal to derive said tuning word for said selected RF signal;
• determining a frequency offset of said carrier signal;
• and
• updating said offset representative words for all of said RF signals in a first mode of operation and updating said frequency representative word for only said selected RF signal in a second mode of operation.

Apparatus comprising:

• a tuner (9) which receives a plurality of RF signals and which produces a carrier signal bearing information corresponding to a tuned one of said RF signals, said tuner (9) including a local oscillator (911) having a frequency controlled in accordance with digital tuning representative words to tune respective ones of said RF signals;
• and
• a controller (921, 923, 11, 19, 13) for controlling the frequency of said local oscillator (911);
• said controller storing digital nominal frequency representative words for respective ones of said RF signals, storing digital offset representative words for respective ones of said RF signals, determining a frequency offset of said carrier signal after a RF signal has been tuned, updating all of said digital offset representative words in accordance with said frequency offset of said carrier, deriving the tuning representative word for an RF signal selected to be tuned by combining said nominal frequency representative word for said RF signal selected to be tuned with said previously updated offset representative word for said RF signal selected to be tuned, and updating the respective digital offset representative word for an individual RF signal presently being tuned if correct tuning is not achieved with the previously updated offset representative word.