An electronic phase sh ifter is a frequency-dependent electronic circuit that shifts the phases of signals. If the phase shift increases proportionally with frequency, then it is called non-dispersive phase shifting. It occurs with constant group delay. Electronic phase shifters can be passive components or circuits such as coaxial cables, delay lines, filters, low-pass or high-pass filters, RC elements, or some other frequency-dependent circuit. However, they can also be active electronic circuits that delay certain frequencies in negative feedback, thereby causing a phase shift.
Optical phase sh ifters are optical elements which change the polarization of the waves. In principle, an optical phase shifter delays the phase of one coherent wave with respect to another. When leaving the phase shifter, the waves then have a different phase than when they entered. The same applies to the polarization state.
Optical phase shifters can consist of several optical waveguides of different lengths, as in a phase array. The optical fibers of different lengths cause the light waves to experience a different delay, which acts as a phase shift. Other methods use beam splitters that divide a monochromatic wave into multiple beams. Still other methods use TN, twisted nematic, technology to polarize the light waves.
Continuous phase shifts can be produced by summing two waves that are out of phase. The amount of phase shift is determined by the ratio of the amplitudes of the two waves.