An apparatus, system, and method are disclosed for phase shifting and amplitude control. A two-phase local oscillator generates an in-phase sinusoidal signal of a fixed frequency and a quadrature sinusoidal signal of the fixed frequency having a ninety degree phase shift from the in-phase sinusoidal signal. A signal generator receives the in-phase sinusoidal signal and the quadrature sinusoidal signal and generates a controllable sinusoidal signal of the fixed frequency. The controllable sinusoidal signal has a variable amplitude and a shiftable phase. A mixer varies the amplitude and shifts the phase of an input signal by mixing the input signal with the controllable sinusoidal signal to generate an output signal. The input signal and the output signal carry phase and amplitude information required for phased array signal processing. Either a receiver or a transmitter may be implemented using the present invention.