The present invention relates to a differential space-time coding of blocks of 2, 4 or 8 information symbols belonging to a 2-PPM modulation alphabet, for a pulse UWB MIMO system with 2, 4 or 8 transmitter antennas. The proposed differential space-time code does not introduce an inversion of the polarity of the pulses, whilst offering maximum diversity and a unit rate.The invention also relates to a pulse UWB transmitter system with 2, 4, or 8 antennas which uses this differential space-time coding, as well as an associated receiver system which does not require channel estimation.