Absorptive Bandstop Filter With Prescribed Negative Group Delay and Bandwidth

An absorptive bandstop filter is proposed and synthesized with prescribed negative group delay (NGD) and negative group delay bandwidth (NBW). It is realized with resistor-loaded coupled-line structures where the NGD can be controlled by the Q-factors of resonators. The resistor of the first section is determined for impedance matching, also providing a negative delay. A prototype is developed, following the proposed design procedure, with NGD = -6.5 ns and NBW= 105 MHz obtained. The proposed method is experimentally validated by the good agreement between the synthesized and measured results.