A system includes a controller module, which includes a storage device, a controller, a modulator, and one or more antennas. The storage device is stored with parameters defining a stimulation waveform. The controller is configured to generate, based on the stored parameters, an output signal that includes the stimulation waveform, wherein the output signal additionally includes polarity assignments for electrodes in an implantable, passive stimulation device. The modulator modulates a stimulus carrier signal with the output signal to generate a transmission signal. The one or more antennas transmit the transmission signal to the implantable, passive stimulation device such that the implantable, passive stimulation device uses energy in the transmission signal for operation, sets the polarities for the electrodes in the implantable, passive stimulation device based on the encoded polarity assignments, generates electrical pulses using the stimulation waveform, and applies the electrical pulses to excitable tissue.