Low loss negative group delay circuit using self-packaged suspended line

A matched negative group delay (NGD) circuit with ultra-low insertion loss by using self-packaged multi-layer suspended line is proposed. Two transmission paths with different electric-lengths are used to produce positive phase slope, which would bring a negative group delay, while a coupled line is used for matching, and the commonly applied absorption resistors are not required. The NGD circuit has been fabricated and measured, and the design has been demonstrated with a measured NGD time of -2.84 ns, a NGD bandwidth of 34 MHz, a low insertion loss/signal attenuation (S-21) of no more than 2.73 dB, and a S-11 attenuation of about 27.8 dB. Both self-packaging and metallized air cavities are used to reduce the wave leakage, and the multiple via holes usually used for electromagnetic shielding are saved, which greatly reduce the fabrication complexity.