Performance evaluation on transmit polarization diversity for implant UWB-IR communications

An ultra wideband impulse radio (UWB-IR) technology is a potential candidate for implant body area networks (BANs), where wireless communications are established between inside and outside of a human body. The UWB-IR technology can accomplish low power consumption and high data rate with an extremely short pulse. However, due to its high frequencies, UWB-IR signals suffer from quite large attenuation in the implant communication link, which makes it difficult to achieve reliable communications. For achieving reliable communication, it is well known that a spatial diversity technique is efficient without any frequency extension. In the related works, several spatial receive diversity techniques for the implant communications have been so far discussed. In contrast, the diversity technique at transmitter side has been rarely discussed because of difficulty of the antenna miniaturization. In this paper, we pay attention to the fact that it is possible to further miniaturize the UWB antenna due to its high frequency, so that, we aim to develop a transmit polarization diversity antenna for implant UWB communications. Then, we investigate the performances of the developed transmit diversity antenna, including the S-parameters and correlation coefficient between each polarization, based on a finite difference time domain (FDTD) method. Finally, we evaluate the bit error rate (BER) performance for the transmit polarization diversity. The computer simulation results demonstrate the feasibility and effectiveness of the transmit diversity for the UWB-IR communications.