Abstract: The ultra wideband (UWB) radio models have been introduced with pulse-position-modulation (PPM), on-off-keying (OOK) and pulse-amplitude-modulation (PAM). The advantages of UWB communication have been set forth such as very high transformation rates, excellent security, fading against multi-path, and so on. The closed form expression of the time domain and power spectrum density has been derived, and the power spectrum has been analyzed for the signal of UWB communication, and the power spectrum of the real signal of UWB communication has been simulated by computer.