A frequency-mixing device performing voltage multiplying and low-pass filtering operations in addition to the frequency mixing is provided. The three operations may be carried out with the same components by designing the frequency mixer appropriately. The frequency mixer comprises a balanced input port to receive a balanced input signal, an oscillator signal input port to receive a first and a second oscillator signal and a first, a second, and a third capacitance. First switching means are arranged to connect, in response to the first oscillator signal, the first and the second capacitance between a first and a second input port of the balanced input port. Second switching means are arranged to connect, in response to the second oscillator signal, the first capacitance between the first input port and the third capacitance and the second capacitance between the second input port and the third capacitance. An output port is connected to terminals of the third capacitance.