A phase shifter is a microwave network which provides a controllable phase shift of the RF signal. Phase shifters are used in phased arrays. Ideal phase shifters provide low insertion loss, and equal amplitude (or loss) in all phase states. Active phase shifters provide gain, while passive phase shifters are lossy.
Analog phase shifters provide a continuously variable phase shift or time delay. Digital phase shifters provide a discrete set of phase shifts or time delays.