I/Q modulators and I/Q demodulators change the amplitude, frequency, or phase of a carrier signal in order to transmit information. I/Q modulators split an incoming data stream into its in-phase (I) and quadrature (Q) components, mix the resulting signals with local oscillators that are 90º apart in phase, and then combine the outputs vectorially in a 0º mixer. There are three basic types of modulation: amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM). For each type of modulation, I/Q demodulators apply an RF signal to a 0º splitter. The resulting signals are then mixed with two local oscillators (LO) that are 90º apart in phase. Both output signals are in phase and quadrature.