A method of signal detection includes receiving an input voltage signal; using AC (alternate current) coupling to couple the input voltage signal into a coupled voltage signal; establishing a DC (direct current) value of the coupled voltage signal using a resistor; generating a self-mixed voltage signal by performing a self-mixing of the coupled voltage signal using a pair of cross-coupling MOS (metal oxide semiconductor) transistors; generating an output voltage by applying low-pass filtering on the self-mixed voltage signal; generating a reference voltage using a reference current terminated with a reference load; and determining a logical signal by comparing the output voltage with the reference voltage.