Reconfigurable negative group delay circuit with tunable group delay flatness

A reconfigurable negative group delay circuit (NGDC) with tunable group delay flatness is presented. The proposed NGDC is composed of an amplifier, three series resistors connecting with two transmission lines, two varactors, and a diode. By shorting different resistors through the diode, different negative group delay (NGD) times can be obtained. Two varactors are utilized to tune the flatness of the group delay. For verification, an NGDC is designed, fabricated, and measured at the center frequency of 1.0 GHz. The measured NGD time is tuned from -2.0 to -5.8 ns. The flat-NGD bandwidth varies from 2.2% to 8.8% with +/- 8% group-delay fluctuation. And the insertion loss varies from 6.5 to 13.8 dB.