A particular implantable device may include one or more antennas configured to receive a first far field radiative signal and a second far field radiative signal. The one or more antennas may be configured to receive the first far field radiative signal in a first frequency band and to receive the second far field radiative signal in a second frequency band. The implantable device may include a voltage rectifier configured to rectify the received first far field radiative signal and the received second far field radiative signal to provide a rectified voltage signal. The implantable device may further include a charge storage element operative to receive the rectified voltage signal and to store charge responsive to the rectified voltage signal. The implantable device may also include a therapy delivery unit powered by the charge storage element. The therapy delivery unit may be operative to deliver a therapy to a patient.