中文摘要：

左手传输线加载偶极子（简称左手偶极子）可以有效实现天线的小型化，但是这种天线通常带宽窄、效率低。通过采用一种渐变的梯形网络结构代替传统的非渐变的结构形式来改善天线的阻抗特性，设计了四单元的左手偶极子天线，进而拓展了天线的带宽，天线总长度为0．2五。仿真和实物测试结果显示：天线同时工作在-1阶和-3阶谐振模式，│S11│≤-10dB的阻抗带宽达到6．5％，在工作频段内（571-610MHz），天线的增益不小于-4．25dBi，效率大于25％。

英文摘要：

Dipole loaded with left-handed transmission lines （LH dipole） can effectively achieve the miniaturization of antennas. However, this type of antennas usually possess the narrow bandwidth and the low radiation efficiency. A four-cells LH dipole antenna with extended bandwidth was designed using a gradual changing ladder network structure to replace traditional non-gradual changing structure. The length of the antenna was 0.2 ,~. The simulating and measure results show that the antenna simultaneously works at both -1 order and -3 order resonant modes, and the impedance bandwidth for │S11│≤-10 dB achives 6.5%. Besides, in the working frequency range of 571-610 MHz, the gain of the prepared antenna is greater than -4.25 dBi, and the efficiency is higher than 25%.