Frequency-division multiplexing arrangement for preventing interference between a main television signal and a helper signal thereof

摘要

A main signal as the existing television signal and a helper signal for high definition are prepared in a transmitter. The energy of the main signal for a plurality of pixels is sequentially detected by an energy detector constituted by an absolute value circuit and an accumulator. The helper signal is controlled by a level controller, constituted by an adder and a divider, in such a way that its level follows according to the level of the detected energy. The level-controlled helper signal is frequency-multiplexed with the main signal having a frequency band of a removed region by a frequency multiplexer. A frequency-multiplexed signal separator of a receiver separates the mutiplexed signal into the main signal and the helper signal. The energy of the separated main signal for a plurality of pixels is sequentially detected by an energy detector constituted by an absolute value circuit and an accumulator. The separated helper signal has its frequency band restored to the original band from the removed region by a frequency domain restoring circuit. The restored helper signal is subjected to level control by a level controller, constituted by an adder and a multiplier, in the opposite characteristic to that of the sender side in accordance with the level of the detected energy.