A mixer includes a transduction circuit, a first and a second switch circuit, and a first and a second load circuit. The transconductor circuit is for generating a differential current signal according to a differential voltage signal. The first switch circuit and the first load circuit are connected in series, and the first switch circuit is used to regulate the differential current signal in response to a first oscillator signal. The second switch circuit and a second load circuit are connected in series, and the second switch circuit is used to regulate the differential current signal in response to a second oscillator signal. The first load circuit and the second load circuit are connected at a common node to reduce harmonic interferences.