A low-cost invasive microwave ablation antenna with a directional heating pattern

Microwave ablation (MWA) is a cancer treatment method. The tumor tissue absorbs electromagnetic energy, which heats and kills it. A microwave ablation antenna plays a critical role in this process. Its radiation field must completely cover the tumor but not the healthy tissue. At present, the radiation pattern of most invasive ablation antennas is spherical. However, in the clinic, the shape of some tumors may be asymmetrical or the antenna cannot be inserted into the center of the tumor for some other reason. In order to solve these problems, a directional heating antenna for microwave ablation is proposed in this paper. The proposed antenna, operating at 2.45 GHz, consists of a monopole and a reflector. The feed is given by a substrate integrated coaxial line (SICL) and coplanar waveguide (CPW). The omnidirectional radiation field of the monopole is reflected by a reflector that is extended from the outer conductors of the SICL to form a directional radiation field. The impedance matching network is designed on SICL to match the antenna to 50 Ω . The antenna is fabricated using a mature printed circuit board (PCB). The reflection coefficient of the antenna in porcine liver tissue measured by a vector network analyzer shows good agreement with the simulations. Then, an ablation experiment in porcine liver is conducted with power of 10 W for 10 min, and the experimental results confirm the validity of the design.     

基于反馈技术的宽带低噪声放大器的设计

介绍了宽带放大器的设计方法和负反馈技术。选用增益高、噪声小的高电子迁移率晶体管（HEMT）ATF54143,利用负反馈和宽带匹配技术,设计制作了一个高增益低噪声放大器,并借助于安捷伦公司的微波电路仿真软件ADS进行仿真和优化。测试表明,在50-300 MHz的频率范围内,低噪声放大器的增益大于22 dB,平坦度小于±0.3 dB,噪声系数小于1.25,输入驻波小于1.4,输出驻波小于1.3。     

电调谐滤波器的研究与设计

介绍了可调谐滤波器的电路结构,解释了设计中采用电感耦合并联谐振电路的具体原因。给出了变容二极管的等效电路,并对由变容二极管构成的滤波器的最大频率可调范围进行了分析。设计制作了一个VHF频段的电调谐滤波器,并使用安捷伦公司的微波电路仿真软件ADS进行仿真,测试表明,此滤波器的频率可调范围为100～260 MHz,插入损耗小于3.8 dB,驻波系数小于1.65。同时在频率的可调范围内对滤波器的插入损耗和矩形系数的变化进行了分析,实验结果和理论分析吻合较好。     

平面左手结构在微波器件及天线设计中的应用

自从2001年首次实现人工左手媒质以来，人们一直致力于制作大带宽、低损耗、易集成且具有左手特性的微波器件与天线．本文着重介绍两种基本的左手结构在平面微波电路中的应用，其一是左右手复合结构，其二为互补开口谐振环结构．近年来，这两种结构在微波器件及天线设计中得到广泛研究与应用．本文总结了国内外在这两个方面的研究进展，并结合我们在这方面所取得的成果，对平面左手电路的原理和应用进行了详细分析和说明。