Design and Test of Crab-Shape Negative Group Delay Circuit

This paper presents the design and the test of distributed planar microwave circuit with crab-shape topology. The circuit topology consists of transmission lines (TLs) associated in feedback with two cascaded coupled lines (CLs). The proposed topology behaves as 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 NGD analysis of the 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. The bandpass NGD behavior is observed around 3 GHz with NGD of approximately -4.8 ns.