In this paper an ultra wideband RFID tag is demonstrated which is manufactured on a tiny piece of silicon. The system on chip, with two on-chip antennas has an overall size of 3mm × 1mm. An asymmetric communication scheme is implemented to power the system, allowing the chip to send an UWB Impulse Radio Pulse Position Modulated signal, once enough power has been harvested. We present measurements which show the transmitted pulses over a distance of 50 mm as well as the pulse burst repetition rate versus input power.