A mixer for direct conversion transmitters and receivers using four phase-shifted local oscillation signals that are orthogonal each other to control a plurality of switches for outputting signals that are orthogonal each other. Two output signals that are orthogonal to each other do not mutually interfere and have a predetermined small signal gain. Further, a mixer may include four or eight switches controlled by four phase-shifted local oscillation signals that are orthogonal each other for outputting signals that are orthogonal to each other on an I-Q plot. The signals outputted from the switches controlled by four phase-shifted local oscillation signals remove I-Q mismatch and a DC component, and improve IP2 characteristics.
