A PIN-diode modulator utilizes the property of a PIN diode which is placed across a waveguide.If the PIN-diode is reverse biased, the insertion loss of the diode is so small that it does not affect the energy flow inside the waveguide. However, when the reverse bias is removed, either fully or partially, the diode begins to control the energy flow, thus creating an amplitude or pluse modulation effect. Impedance matching is required to obtain the maximum power output. Leaving the diode unbiased could be destructive to the diode when is a signal flow in the system.