| 摘要 |
A feedback controller, in an FM audio processor, controls the "integrated multiplex power" to the requirements of ITU-R 412. This regulation specifies the maximum power that is equal to the power of a sinewave modulatinmg the carrier +/-19kHz /where +/-75kHz. The controller applies the square (190) of the multiplex signal (220) to an integrator (220). A constant (180) is removed from the integrator, representing the maximum power threshold. The output (230) of the integrator is sampled periodically with a sample-and-hold circuit (240). A second integrator (280) receives the output (250) of the sample-and-hold. The output (290) of the second integrator circuit is added to the threshold setting (330) of a compressor (110), which determines the average power output of the compressor. The output (120) of the compressor is applied through a peak controller (130) to the input of the multiplex coder (150), closing a feedback loop, which controls the integrated multiplex power to a preset threshold. |
