VARIABLE-THROUGHPUT DIGITAL MODULATOR, AND ITS UTILIZATION IN FM RADIO BROADCASTING

摘要

PURPOSE: To promote new service such as the broadcasting of fixed images and news information in FM radio broadcasting by utilizing the digital modulation device of a variable flow rate and introducing the transmission channel of completely interchangeable supplementary data. ;CONSTITUTION: A demultiplexer 1 demultiplexes transmission digital signals e(t) to first and second elementary signals on time-base. Thereafter, by transmission filter circuits 21 and 22, the respective types of modulation is performed by the respective flow rates of the first and second elementary signals and filtered first and second elementary signals are sent out. Then, a flow rate changeover control circuit 20 for switching from a first filter mode to a second filter mode or vice versa based on flow rate control signals is provided. A 4-phase modulation circuit 3 receives the first and second filtered elementary signals at a modulation input end, an addition circuit 4 receives the first and second signals of modulated carrier waves and the obtained signals of the modulated carrier waves are sent out.;COPYRIGHT: (C)1995,JPO