此函数用于产生脉冲超宽带系统的训练序列的波形。输出参数有三个：bits--发送的数据,stx--发送的信号,ref--参考信号

发送端调制方式为TH-PAM-The emerging ultra-wideband (UWB) system offers a great potential

for high data rate wireless multimedia applications of the home

entertainment and industry, as well as for low data rate sensor

networks involving low power devices~\cite{paragraph1}. One of the

most acute challenges in realizing these potentials of the UWB

systems is the timing acquisition. Timing errors as small as

fractions of a nanosecond could seriously degrade the system

performance~\cite{paragraph21}. The difficulty in UWB

synchronization arises from UWB signals being the ultrashort

low-duty-cycle pulses operating at very low power density.