Planar Coupled-Line-Based Flat Negative Group Delay Microwave Circuit With Size Reduced and Bandwidth Enhanced

A novel planar coupled-line-based flat negative group delay circuit (NGDC) is proposed with size reduced and bandwidth enhanced. The proposed planar NGDC is composed of three coupled-line sections and two resistors with advantages like low cost, simplicity to integrate, simple design procedure, and compact circuit size. The effects of circuit physical variables on
${S}$
-parameters, flatness and bandwidth of NGDC are explained by parametric study. To verify the proposed method, a planar coupled-line-based flat NGDC with a size of
$0.043 {\lambda }_{g}^{2}$
is designed, fabricated, and measured at the center frequency of 0.94 GHz. A very good agreement is confirmed by simulation and experimentation results. The measured results show that the flat negative group delay bandwidth of the proposed NGDC reaches 330 MHz (35.1% from 770 MHz to 1100 MHz) with 14% group delay ripple and insertion and reflection losses better than 14 dB and 19 dB, respectively.