中文摘要：

在前向链路，为使标签获得更多能量，结合ASK调制提出了一种新的用于无源RFID系统的能量有效的数据编码方法．通过在一个码元周期内采用可调的非对等的高低电平持续时间，使高电平持续时间更长．分析结果表明，在40kbps的典型速率下，该编码使前向链路的基带信号所携带的能量最多可高于Manchester编码的84％．同时该编码可以提高系统性能．测试结果与理论分析相符合．在反向链路，提出了编码的OOK和编码的BPSK调制．采用截止速率研究编码对系统性能的影响．分析结果表明，编码调制更为能量有效．在几乎不增加芯片复杂度的前提下，提升了系统性能．分析并估算了不同截止速率时编码对系统信息速率和通信距离所带来的增益．

英文摘要：

In forward link, to cooperate with ASK modulation, a new data coding method for carrying out more energy to passive tag is presented for passive RFID system in this paper. The basic idea of the coding is to set adjustable and asymmetric high and low level duration within a symbol cycle, and a longer duration for high level. The performance analysis results show the energy of baseband data transmitted from reader to tags increased by 84% at most, compared with that of Manchester coding at typical 40kbps. The system performance can be increased by using this coding. The same results are showed by the testbed and theoretical analysis. In return link, the scheme of coded OOK and coded BPSK is proposed. The cutoff rate is used to study the influence of encoding on system performances. Analysis results show that coded modulation is more energy efficient than uncoded modulation in Passive RFID return link and the system performance is improved with almost no increase in chip complexity. The gains of encoding in system information rates and communication range for different cutoff rate is analyzed and evaluated.