S-Matrix and Bandpass Negative Group Delay Innovative Theory of Ti-Geometrical Shape Microstrip Structure

Abstract

A theoretical investigation of distributed microwave circuit built with Ti-shape topology is developed. The topology under study consists of neighbored T-and i-shape interconnect lines. The Titopology equivalent S-matrix is calculated as a function of crosstalk coupling coefficient and coupled line (CL) delay. To highlight the NGD modelling feasibility, parametric analyses with respect to the T-and ielement coupling and delay are introduced. More practical validation is carried out with designed, simulated and measured microstrip prototype. It is found that because of T-and i-crosstalk, the Ti topology can behave as a bandpass NGD function. A good NGD performance with NGD level of approximately-1 ns around the center frequencies 2.2 GHz with transmission coefficient of approximately-2.1 dB and reflection coefficient better than-14 dB. The measured results are in good agreement with calculated models and simulations. Two-cell Ti-NGD circuits were also investigated to illustrate the designability of the topology for multi-band and widened single band NGD responses.

Novel Bandstop Filter With Improved Flat NGD Characteristics and Signal Attenuation in Passband

“…Scholars from various countries have proposed different structures of NGD circuits to improve circuit performance, a theoretical study was conducted on distributed microwave circuits with "Ti" type topology in [3]. The circuit has good NGD performance, with an NGD level of approximately −1 ns near the center frequency of 2.2 GHz and a transmission coefficient of approximately 2.1 dB.…”

Robustness study of bandpass NGD behavior of ring-stub microstrip circuit under temperature variation

“…Innovative NGD circuits operating with low-pass and bandpass (BP) behaviors were designed. Thanks to the ambitious research work made by some research groups around the world, various topologies of typical BP NGD circuits were investigated [20][21][22][23][24][25][26][27][28][29]. The main challenges on the NGD microwave circuit of the last two decades were on the loss compensation [20,21], circuit operation understanding [22,23], the size reduction [24][25][26][27], and the implementation of low-attenuation passive circuits [28,29] susceptible to operate in the gigahertz frequency range.…”

“…Thanks to the ambitious research work made by some research groups around the world, various topologies of typical BP NGD circuits were investigated [20][21][22][23][24][25][26][27][28][29]. The main challenges on the NGD microwave circuit of the last two decades were on the loss compensation [20,21], circuit operation understanding [22,23], the size reduction [24][25][26][27], and the implementation of low-attenuation passive circuits [28,29] susceptible to operate in the gigahertz frequency range. An active NGD circuit designed with a microwave transversal filter approach was proposed [20].…”

“…Furthermore, different NGD compact circuits based on microstrip TLs were investigated [24][25][26][27]. Then, innovative geometrical shape topologies of low loss NGD passive microstrip circuits were proposed [28,29]. Some tentative applications of the NGD function targeted for the GD equalization were initiated [30,31].…”