An UWB low power active transmitter operating in the European UWB band (6-8.5 GHz) is presented, which may find applications in RFID transponders with asymmetric downlink and uplink communication, as well as in others communication devices. It is based on a 7.25 GHz oscillator driven by a base-band pulse generator, and connected to a small size UWB antenna. The oscillator is turned on and off by the base-band pulsed control voltage, according to a modulation scheme, and it consumes power only when the 7.25 GHz pulse is generated. The RF pulse waveform exhibits a peak amplitude of about 2.2 Vpp and a width of about 2 ns. The power spectral density of the single UWB pulse is in accordance with the European UWB mask. A planar compact UWB antenna is also proposed as the load of the transmitter. It shows a return loss lower than -14 dB in the operating frequency band.