中文摘要：

宽带超声衰减是反映松质骨中骨矿密度的一个重要参数，常用超声脉冲波进行测量。由于透过骨骼的超声波衰减严重，接收信号十分微弱并带有强噪声，从而限制了测量深度，并容易产生测量误差。编码信号发射技术是提高信噪比和增加超声透射深度的有效途径。本文提出一种新的编码方法，它用Chirp信号调制Golay互补码，产生称之为Golay-Chirp的编码信号。它相对于传统的Golay信号、Chirp信号等有更好的抗干扰能力，并可以进一步降低发射功率或增加超声透射深度。

英文摘要：

Broadband ultrasound attenuation （BUA） is an important parameter often used to reflect the cancellous bone mineral density and is measured by the way of ultrasonic pulse wave. Because the ultrasound attenuated heavily while propagating through bone, the received signal is very weak and accompanied with strong noise, the measuring depth is confined and measuring error is brought to some extent. Basically the technique of coded signal emission is a good way to improve the signal to noise ratio （SNR） and increase the depth of ultrasonic penetration. A new coding method is presented in the paper, which uses chirp signal to modulate Golay code and then produce a new coded signal named Golay-Chirp. Compared with traditional Golay or chirp signal, Golay-Chirp coded signal shows good performances with higher SNR, lower transmission power and longer transmission distance.