Miniaturized tunable Meanderline loaded antenna with Q-factor approaching the lower bound

Realizing a high-efficiency tunable antenna to cover a wide band with a good matching is an interesting topic, especially in the case when the physical size of the antenna has to be very small. A novel spherical monopole antenna which has been miniaturized through a couple of Meanderline sections is presented in this paper. This antenna, with maximum dimension of 0.05λ, has dual band operation with independent frequency-tuning capability in the 30-88 MHz frequency band. Thanks to the antenna geometry and the Meanderline miniaturization technique, the exact Q-factor of the antenna approaches the Thal lower bound.