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