采用电容耦合式馈线的高温超导滤波器设计

Design of High-Temperature Superconducting Filter with Capacity-Coupled Feedlines

为了获得结构紧凑的滤波器,在设计中采用了螺旋形谐振器和电容耦合式馈线结构。利用集总元件等效电路给出了谐振器与电容耦合式馈线组成的电路的谐振频率和有载Q值的表达式。提出了馈线为电容耦合式时的集总元件带通滤波器等效电路。并基于上述电路在MgO基片上设计和实际制作了一个高性能的高温超导微带线滤波器。该滤波器的中心频率为2542 MHz,相对带宽为0.6%,尺寸仅为10 mm×15 mm。测试结果表明滤波器的带内插损小于0.1 dB,反射损耗为40.0 dB,验证了该等效电路设计方法的有效性。

A compact High-Temperature Superconducting （HTS） filter with spiral resonators and capacity-coupled feedlines is presented. The resonant frequency and the external Q factor of the capacity-coupled resonator are calculated. A lumped-element prototype bandpass filter is developed for the design of capacity-coupled microstrip filter. A 3-pole microstrip filter was designed based on the lumped-element prototype filter. The filter has a compact size of 10 mm×15 mm with a center frequency of 2542 MHz and a 0.6% bandwidth. The measured frequency response at 70 K shows that the insertion loss is less than 0.1 dB and the return loss is better than 40 dB. The excellent performance validates the design method.