Miniaturized Active Metamaterial Resonant Antenna With Improved Radiation Performance Based on Negative-Resistance-Enhanced CRLH Transmission Lines

In this letter, a miniaturized microstrip resonant antenna (MRA) based on the active metamaterial resonator is presented. Unlike the passive composite right/left-handed (CRLH) resonators, the presented active metamaterial resonators are realized using the negative-resistance-enhanced CRLH transmission line that incorporates active circuits for loss compensation. The active circuit uses bipolar junction transfer in its inverted-common-collector configuration to provide a negative resistance for the proposed active MRA. The presented passive and active antennas both operate in the negative-first-order resonance mode and thus have reduced dimensions compared to the conventional planar MRAs. The integration of the active elements delivers higher radiation gain compared to the passive negative-order CRLH resonator antenna. The passive and active antennas were fabricated, and the measured results are presented to validate the concept.