Amplitude detecting circuit

An automatic gain controller comprising:

• an amplifier for amplifying an input signal;
• an A/D converter for converting an output of the amplifier into a digital signal;
• a digital filter for processing the supplied digital signal;
• an amplitude detecting circuit for detecting an amplitude of an output signal from the digital filter, to which the digital signal from the A/D converter is supplied;
• a gain control circuit signal for generating a gain control signal on the basis of the amplitude of the detected output signal, and for supplying the gain control signal to the amplifier,
• wherein said amplitude detecting circuit comprises:
• a simple digital filter having a plurality of taps corresponding to a part where energy is concentrated in full impulse responses of a non-recursive signal processing digital filter;
• and
• wherein the same signal as a signal supplied to said signal processing digital filter to said simple digital filter is supplied, and an output amplitude of said signal processing digital filter as an output of said simple digital filter is approximately detected.

A peak suppression circuit comprising:

• a delay circuit for delaying an input signal;
• a digital filter for processing the supplied delayed input signal;
• an amplitude detecting circuit for detecting an amplitude of an output signal from the digital filter, to which the input signal is supplied;
• a peak suppression control circuit for generating a peak suppression control signal on the basis of the amplitude of the detected output signal, and for supplying the peak suppression control signal to the digital filter,
• wherein said amplitude detecting circuit comprises:
• a simple digital filter having a plurality of taps corresponding to a part where energy is concentrated in full impulse responses of a non-recursive signal processing digital filter;
• and
• wherein the same signal as a signal supplied to said signal processing digital filter to said simple digital filter is supplied, and an output amplitude of said signal processing digital filter as an output of said simple digital filter is approximately detected.