an improved method and system for generating quadrature phase shift keying signals for use in data transmission is provided . a pair of oscillators are slaved to the transmit frequency and produce two quadrature signal components with the same frequency but 90 degrees out of phase . the two signal components are carried to separate bi - phase switches by mirrored waveguides . each bi - phase switch has a reflective waveguide coupler which directs the received signal into a waveguide terminated by a hard short and has a controllable shorting plane spaced approximately one - quarter wavelength from the termination point . the shorting planes are controlled by the output data signals and each introduces a 180 degree phase shift in the respective signal component when activated . the reflective couplers direct the selectively phase shifted signal components to an in - phase combiner , where they are combined to produce the quadrature phase shift keyed output signal .