Bandpass NGD Time-Domain Experimental Test of Double-li Microstrip Circuit

This paper details a time-domain (TD) test to visualize impacts on the double-li microstrip circuit behavior of its bandpass (BP) negative group delay (NGD). To determine the central frequency and the bandwidth of the input signal to use during the TD test, a frequency domain (FD) S-parameter analysis of the circuit has been done. This preliminary analysis, carried out first with the aid of simulations and then with the aid of measurements, shows a NGD for a frequency band of 15 MHz (resp. 8 MHz) around 2.345 GHz (resp. 2.364 GHz). To observe in the TD the NGD impact around 2.345 GHz, TD experimentations have been performed using a 2.345 GHz sine carrier shaped by Gaussian pulses. During these TD tests, the BP NGD signature was verified thanks to the output envelopes which presents rising and falling edges in time-advance compared to the input ones. It was also experimentally shown that the output is normally delayed when the input sine carrier is outside of the li-circuit NGD frequency bands.