INVESTIGATION ON THE MICROWAVE PULSE SIGNAL COMPRESSION WITH NGD CIRCUIT

This paper demonstrates the exhibition of pulse compres- sion from an electronic circuit with negative group delay (NGD). This circuit consists of a fleld efiect transistor (FET) cascaded with shunt RLC network. Theoretic and experimental investigations have proved that, at its resonance frequency, the group delay of this circuit is al- ways negative. The present study shows that around this resonance, it presents a gain form enabling to generate pulse compression. To validate this concept, as proof-of-principle, devices with one- and two- stages FET were implemented and tested. Measurements of the one- stage test device evidenced an NGD of about i2:5ns and simulta- neously with 2dB ampliflcation operating at 622MHz resonance fre- quency. In the frequency domain, in the case of a Gaussian input pulse with 40MHz frequency standard deviation, this resulted in 125% ex- pansion of pulse width compared to the input one. In time domain, simulations showed that the compression was about 80% in the case of an input Gaussian pulse with 4ns standard deviation. With the other prototype comprised of two-stage NGD cell, the use of a sine carrier of about 1.03GHz allowed to achieve 87% pulse width compression.