Active resonator using comb-shaped defected ground structure with negative resistance

A design for a new active resonator with gain using a comb-shaped defected ground structure (DGS) with a negative resistance is presented. The negative resistance is realized using a single transistor coupled between two separated parts of the DGS. This negative resistance is realized on a separate circuit-board layer that is attached to the DGS. It is used to compensate for the insertion loss of the resonator. An HFSS-ADS co-simulation is used to combine the electromagnetic structure as well as all parasitic effects along with the behavior of the active circuitry. The design consists of a single resonating element with a center frequency of 2.93 GHz, 3-dB bandwidth of 137 MHz, simulated noise figure of 4.9 dB, and 3.48 dB of gain. The results from the simulation are presented along with the measured response. A good agreement is observed between the results.