Abstract: A high isolation broadband switching circuit includes a plurality of switching elements coupled in series alternatingly with transmission line segments. Each switching element has a low or very high impedance between first and second points responsive to first and second values of a control voltage, respectively. In a first embodiment, the switching element includes a PIN diode having a cathode coupled to a first transmission line and an anode coupled to a second transmission line. In a second embodiment, the switching element includes a field effect transistor (FET) having a drain coupled to a first transmission line and a source coupled to a second transmission line. A first resistor is coupled between the drain and the source for DC continuity between the drain and the source, and a second resistor coupled between a gate of the FET and ground for DC continuity. A bias voltage source is coupled through a resistor to one of a source and a drain of one of the FETs.