A microwave Isolator is a two-port device that acts as a unidirectional trap, protecting sensitive components in a system from signal reflection. It is analogous to the diode in a DC circuit or the check valve in a fluid-flow system. Isolators are commonplace in power amplifier, radar, antenna, and transceiver systems, making them essential in laboratory, commercial, military, and even space applications. Commercial isolators are offered as discrete devices in shield metal cans with limited isolation (10-25 dB, the larger, the better protection).