Design and Test of Crab-Shaped Negative Group Delay Circuit

This paper presents the design and test of a distributed planar microwave circuit presenting a crab-shape topology. The circuit’s topology consists of transmission lines (TLs) associated in feedback with two cascaded coupled lines (CLs). This topology has the characteristics of a bandpass negative group delay (NGD) function. The analytical model allowing to determine the group delay (GD) is established from S-parameter approach and the analysis of NGD crab topology is described. The NGD existence condition as a function of the topological parameters is presented. The NGD circuit proof-of-concept (PoC) is designed, simulated, and fabricated to understand and validate the proposed NGD functions. The measured, simulated, and theoretical results are in good agreement. As designed, the band pass NGD behavior is observed around 3 GHz with NGD of approximately -4.8 ns.