Study on UWB Channel Characteristics and Modeling in Human Body

超宽带(UWB)系统具有低功耗和多径补偿的特点，是一种很有前途的体上和体内通信系统。在这项研究中，我们首先利用频域有限差分法(FD^2TD)结合一个基于解剖学的人体模型分析了人体的声道特性。我们通过测量确定了人体的频率相关介电特性，并通过德拜近似将其融入到FD^2TD算法中。基于Fd^2TD的结果，我们推导出了人体的信道特性(幅度和群延迟)。我们发现100 MHz以下的频率比在体通信更好，因此提出了一种带宽为10-70 MHz的超宽带脉冲传输系统。我们进一步研究了UWB脉冲传输系统的UWB-IR性能，结果表明，由于在体传输，误码率(BER)仅有0.1dB的下降。另一方面，我们还设计了一种用于3-5 GHz频段的体内通信的超宽带植入天线，并显示了其在医疗应用中的应用。我们进一步发展了一种评估UWB脉冲的比能量吸收(SA)和比吸收速率(SAR)的方法，并证明了UWB在体内和体内通信中应用的安全性。

The ultra wide band (UWB) system is a promising candidate for the on-body and intra-body communications in view of its features of small power and multi-path compensation. In this study, we have first analyzed the on-body channel characteristics by using the frequency-dependent finite difference time domain (FD^2TD) method together with an anatomically based human model. We have determined the frequency-dependent dielectric properties of human body by measurements, and have incorporated them into the FD^2TD algorithm via Debye approximation. Based on the FD^2TD results, we have derived the channel characteristics (both amplitude and group delay) on human body. We have found that the frequencies below 100 MHz are preferable to the on-body communications, and therefore have proposed a UWB pulse transmission system with a bandwidth of 10-70 MHz. We have further investigated the UWB-IR performance for the UWB pulse transmission system, and have demonstrated that the degradation on the bit error rate (BER) is only 0.1 dB due to the on-body transmission. On the other hand, we have also designed a UWB implanted antenna for intra-body communication at 3-5 GHz band, and have shown its usefulness for medical applications. We have further developed a method for the specific energy absorption (SA) and specific absorption rate (SAR) evaluation of UWB pulses, and have demonstrated the safety of the UWB applications in on-body and intra-body communications.