In this article, a dynamically reconfigurable dual-layer ultra-wideband (UWB) antenna integrated with an energy harvesting (EH) system for powering a GaAs FET switch is presented. The UWB antenna dynamically creates a notch band in the presence of an interfering signal at 5.6 GHz and it goes back to normal UWB operation when the interferer is removed. For the switching operation, the FET switch is powered using only harvested energy carried by the interfering signals. The UWB antenna on the front layer is a microstrip-fed monopole with an embedded elliptical slot. A quarter wavelength linear stub acts as a resonator inside the slot, which is connected and disconnected using the low-power FET switch. The UWB antenna shares the RF ground with a very compact EH system that consists of a planar inverted-F antenna, a very compact voltage-doubler rectifier, and a passive direct-current (dc)-to-dc boost converter. The boost converter elevates the rectified voltage to above the 3.3 V threshold, which is the minimum voltage needed for the actuation of the FET switch. The dynamic notch-band reconfiguration of the UWB antenna without the need for an external dc power source is made possible when the collected power at the input of the rectifier is higher than −12 dBm.