A Negative Group Delay Microwave Circuit Based on Signal Interference Techniques

A novel self-matched negative group delay (NGD) microwave circuit based on the signal interference technique is proposed to eliminate the performance degradation due to the temperature-dependent resistance variation. The proposed circuit consists of unequal power dividing/combining structures and coupled-line phase shifter, which can be directly synthesized with prescribed NGD time and insertion loss (IL). To verify the proposed method, an NGD circuit with a size of 0.41λg× 0.41λgis designed and fabricated. From the measured results, NGD time of -2.09 ns at the center frequency of 1.016 GHz is obtained with NGD bandwidth of 14.2% (0.944-1.088 GHz), in which the IL is less than 18.1 dB and the return loss is greater than 33 dB.