Abstract: Research method to achieve large bandwidth pulses for detecting neural weak signal is given. Much larger survey depth, better resolution ratio, more powerful image capability and recognition capability can be achieved by using UWB electromagnetic pulse as survey signal than using harmonic wave. However, transmit power of search-and-rescue radar, whose transmit signal is UWB electromagnetic pulse, is much restricted. In this paper, it is discussed in detail that pseudo-random code can be used to modulate UWB short pulse. Encoded signal can keep the bandwidth of the sub pulse signal and have high energy. So that the search-and-rescue radar can transmit noise-like long seriary pulses signal at a low power and improve the survey distance. Based on the fundamental research and computer simulati