A Design of Reconfigurable Negative Group Delay Circuit Without External Resonators

In this letter, we present the novel design and implementation of a microstirp line reconfigurable negative group delay circuit (NGDC) using a branch-line. Theoretical analysis shows that reconfigurable characteristics in the proposed circuit can be obtained by properly choosing the characteristic impedances of the branch-line and tuning only the termination resistance. Therefore, the proposed reconfigurable NGDC does not require any extra resonators. For experimental validation, the proposed circuit was designed and fabricated for a wideband code division multiple access downlink frequency operating at a center frequency ( f₀) of 2.14 GHz. Measurement results show the group delays variation of -2 ns to -10 ns with signal attenuation variation of -25 dB to -36.6 dB at f₀. For enhancement of the negative group delay bandwidth, two NGDCs operating at slightly different center frequencies are cascaded and measured.