摘要
本文研究了一款基于非对称耦合阶跃阻抗谐振器SIR(stepped-impedance resonator)设计的6阶窄带超导平衡式带通滤波器,该滤波器具有高的频率选择性以及宽阻带特性.本文首先研究了3种具有不同耦合特性的SIR耦合对,分析了其差模DM(differential mode)相位移、耦合系数,以及共模CM(common mode)抑制水平.通过适当选取SIR的阻抗比以及使用具有分散谐波分量的不同尺寸的SIR,其高次频得以远离基频,从而拓宽阻带.同时,由于其DM和CM等效电路具有不同的谐振频率,其带内的共模噪声可以得到天然的抑制.研究表明,电磁耦合对可在不增加电路面积的情况下获得小的耦合系数以利于窄带设计,电耦合对结构有利于高阶电路的互连,而磁耦合对具有最佳的CM抑制水平.此外,3类SIR对的弱耦合特性均可用于窄带设计.为了验证,本文采用所述3类SIR对设计了一款6阶平衡式带通滤波器,并在此基础上引入交叉耦合结构产生传输零点以提高通带选择性.其零点的产生机理通过传输路径的幅度及相位移分析进行了说明.最终,本文利用高温超导HTS(high-temperature superconducting)技术实现了所设计的具有交叉耦合结构的滤波器,以降低插入损耗.该电路在77 K温度下进行了测量,测试结果表明:通带的相对带宽FBW(fractional bandwidth)为1.6%,带内插损约为0.37 dB,带内CM抑制度优于40 dB.其-60 dB带宽/-3 dB带宽的矩形系数小于1.45,同时-20 dB DM阻带达到约5倍f_(0)^(d)(f_(0)^(d)代表DM基波频率).
This study investigates a sixth-order narrowband superconducting balanced filter with high frequency selectivity and wide stopband based on asymmetrically coupled stepped-impedance resonators(SIRs).Three types of coupled SIR pairs with different characteristics are investigated.The differential-mode(DM)phase shifts,coupling coefficients,and common-mode(CM)levels of the three SIR pairs are then analyzed.The spurious frequencies of DM responses can be pushed far away from the fundamental frequency to widen the stopband by properly choosing the impedance ratio of the SIR and using dissimilar SIRs with dispersed harmonics.Moreover,an inherent CM suppression can also be obtained because of the different resonant frequencies in DM and CM equivalent circuits.Results also show that the electromagnetic coupling pair can contribute a weak coupling coefficient for narrowband design without increasing the circuit size.The structure of the electric coupling pair is beneficial for high-order circuit interconnection.The magnetic coupling pair possesses the highest CM rejection.Moreover,the weak coupling properties are well-utilized for narrowband design.For validation,a sixthorder balanced bandpass filter is designed using the three coupled SIR pairs,and a cross-coupling structure is further introduced to produce transmission zeros(TZs)and enhance the passband selectivity.The magnitude and phase delay of the DM transmission paths are analytically illustrated to explain the TZ production.Eventually,the proposed balanced filter is implemented by a high-temperature superconducting technique to reduce the insertion losses and is measured at the temperature of 77 K.The measured results show that the fractional bandwidth of the passband is 1.6% with less than 0.37 d B in-band insertion loss.The-60 dB bandwidth/-3 dB bandwidth rectangle ratio is less than 1.45 while the in-band CM suppression is better than 40 dB.The -20 dB stopband is up to about 5 f_(0)^(d)(f_(0)^(d)is the DM fundamental frequency).
作者
刘海文
唐嘉铭
Haiwen LIU;Jiaming TANG(School of Information and Communications Engineering,Xi'an Jiaotong University,Xi'an 710049,China;School of Electronic Science and Engineering,Xiamen University,Xiamen 361005,China)
出处
《中国科学：信息科学》
CSCD
北大核心
2021年第1期157-170,共14页
Scientia Sinica(Informationis)
基金
国家自然科学基金重点项目(批准号:U1831201)
国家重点研发计划(批准号:2017YFE0128200)
陕西省国际科技合作计划项目(批准号:2019KW-003)
江西省自然科学基金重点项目(批准号:2017ACB20019)资助。
关键词
平衡式滤波器
阶跃阻抗谐振器
高阶
窄带
高温超导
balanced filter
stepped-impedance resonator(SIR)
high order
narrowband
high-temperature superconductor(HTS)
