In the digital broadcast modulating signal working preliminary

摘要

PROBLEM TO BE SOLVED: To enable current/spare digital broadcast modulation signals to be smoothly switched from one to another.;SOLUTION: Current and spare digital broadcast modulation signals are adjusted in amplitude to a prescribed value by amplitude adjusters 102 and 112 and delayed by a certain time respectively. After the current and spare digital broadcast modulation signals have passed through up-converters 104 and 114, a phase difference between the current and spare digital broadcast modulation signals is detected by a phase detector 121, the output signals of the phase detector 121 and reference frequency signals originated from a reference signal generator 124 are compared with each other by phase adjusters 122 and 123 to detect a frequency synchronous deviation, and a correction corresponding to the frequency synchronous shift and another correction corresponding to the phase difference are obtained and given to the up-converters 104 and 114, by which the current and spare digital broadcast modulation signals are made to synchronize with each other and made coincident with each other in phase. In this state, when a current/spare switching indication is inputted through a controller 132, a seamless switch 131 is switched from a current system to a spare system.;COPYRIGHT: (C)2002,JPO