Design, Modeling and Synthesis of Negative Group Delay IL-Shape Topology

This paper introduces a negative group delay (NGD) theory of passive topology presenting “IL”-shape geometry. The two-port topology is comprised of a coupled line with an open- and stub-loaded terminations. After introduction of the electrical equivalent circuit, the S-parameter modeling of the IL topology is established. The transmission and reflection parameters are analytically expressed. The IL topology NGD characterization is developed in function of the design parameters. The relevance of the NGD theory is verified with fully distributed and compact prototypes implemented in microstrip technology. The tested results confirm the possibility to generate bandpass NGD function with IL topology. The calculated model, simulation and measurements are in very good correlation. Validation results showing center frequencies at about 1.55 GHz and 3.55 GHz with NGD level better than -1 ns over 30 MHz bandwidth. The IL NGD prototypes present transmission and reflection coefficients better than -3 dB and -10 dB, respectively.