DC offset suppression circuit for a complex filter

A DC offset suppression circuit of a complex filter transiting outputs of the complex filter to the DC feedback unit to feed back to suppress a DC offset occurring in self-mixing of a mixer;

• the complex filter comprising:
• a first filter unit for generating a first output and a second output after filtering a first input and a second input outputted by a mixing circuit;
• a second filter unit for generating a third output and a fourth output after filtering a third input Vqinm and a fourth input Vqinp output by a mixing circuit;
• a frequency-changing unit for feeding back the outputs from the first filter unit to an input of the second filter unit and the outputs from the second filter unit to an input of the first filter unit, respectively, via frequency-changing resistors;
• the DC offset suppression circuit comprising a first suppression circuit and a second offset suppression circuit, each offset suppression circuit comprising:
• a phase compensation unit for compensating output signals input to the first and the second filters for phase of altered frequencies;
• and
• DC feedback unit for reversing phase of compensated signals in the phase compensation unit and feeding back the compensated signals to inputs of the first and second filter units.