| 摘要 |
IN A RECEIVER FOR PROCESSING A VESTIGIAL SIDEBAND (VSB) MODULATED SIGNAL CONTAINING TERRESTRIAL BROADCAST HIGH DEFINITION TELEVISION INFORMATION AND A PILOT COMPONENT, AND FOR WHICH MULTIPATH INTERFERENCE CAN LEAD TO SIGNIFICANT ATTENUATION WITHIN NARROW BANDS OF THE RECEIVED SIGNAL SPECTRUM CONTAINING THE PILOT TONE OF AN ADVANCED TELEVISION SYSTEMS COMMITTEE (ATSC0 HIGH DEFINITION TELEVISION (HDTV) BROADCAST SIGNAL, IT HAS BEEN FOUND DESIREABLE TO AMPLIFY THE INPUT SIGNAL IN ORDER TO ACHIEVE SYNCHRONIZATION OF THE RECEIVER''S PHASE-LOCKED LOOP TO THE RECEIVED PILOT TONE. ONCE THIS INITIAL ACQUISITION HAS BEEN ESTABLISHED, THE AMPLIFICATION APPLIED TO THE RECEIVED SIGNAL CAN BE REDUCED TO A LEVEL APPROPRIATE FOR REMAINING BLOCKS IN THE DEMODULATION CHAIN WITHOUT UPSETTING THE PILOT TONE SYNCRONIZATION. THUS, ACCORDING TO THE PRESENT INVENTION, THE GAIN APPLIED TO THE RECEIVED ATSV VSB SIGNAL IS SET HIGHER DURING PILOT TONE ACQUISITION THAT IT IS DURING THE REMAINING STAGES OF DEMODULATION.(FIG 1) |
