Patent ID: 8810308

Claim:
A filter for receiving an input signal and generating an output signal according to the input signal, comprising: a first input network connected to receive the input signal for providing a first normal path for the input signal to generate a first normal signal, wherein the first normal signal has the same frequency components as the input signal; a first high-pass network connected to receive the input signal for providing a first high-pass path for the input signal to generate a first high-pass signal; an operational circuit having a first input terminal and a second input terminal, wherein a polarity of the second input terminal is inverse to a polarity of the first input terminal; and a second input network providing a second normal path for the input signal to generate a second normal signal; and a second high-pass network providing a second high-pass path for the input signal to generate a second high-pass signal, wherein the operational circuit receives the first normal signal by the first input terminal and the first high-pass signal by the second input terminal such that a subtraction operation is performed on the first normal signal and the first high-pass signal to accomplish a filtering operation for generating the output signal; wherein the operational circuit receives the second normal signal by the second input terminal and the second high-pass signal by the first input terminal such that the subtraction operation is performed on the second normal signal and the second high-pass signal to accomplish the low-pass filtering operation for generating the output signal.