High order filter circuit

A high order filter circuit including:

• a plurality of second order filter units for filtering inputted signals;
• a plurality of switch units for connecting the plurality of second order filter units in a cascade to form a high order filter unit when the switch units are closed, and for restoring the high order filter unit to the plurality of second order filter units when the switch units are opened;
• an analog-to-digital converter (ADC) having a first working status and a second working status, for detecting peaks of predetermined band signals outputted from the second order filter units and digitalizing the peaks when the ADC is in the first working status, and for detecting and converting the predetermined band signals from the second order filter units to digital signals and outputting the digital signals when the ADC is in the second working status;
• and
• a digital correction unit for comparing the digitalized peaks with a default value and generating comparison results, and according to the comparison results, the digital correction unit generating frequency control signals and working status control signals and sending them as feedbacks respectively to the second order filter units for adjusting their working frequencies and to the ADC for switching its working status.