A Non-Foster Matched Dipole For A Low-Vhf Mobile Transmitter System

A major bottleneck of low frequency communication applications is relatively low-data-rate transmissions due to narrow bandwidth with miniaturized antennas. To increase the bandwidth of small antennas, we propose a non-Foster matched antenna designed for a low-VHF transmitter system. A non-Foster element realized by a single negative impedance converter is applied to a passive-matched miniature dipole at 40 MHz. A rigorous stability analysis based on system sensitivity is performed via circuit simulation and measurement. A power transmission coefficient with a reference antenna in an indoor setting along with impedance bandwidth of the non-Foster matched dipole is measured and compared with those of the passive-matched one. The results show 3dB power bandwidth is improved by a factor of two with active matching and more than 80 % of the bandwidth has a power efficiency advantage, compared to passive matching.