Efficient Electrically Small Antenna Facilitated by a Near-Field Resonant Parasitic

An electrically small electric-based metamaterial-inspired antenna system that is designed for narrow bandwidth operation near 300 MHz is presented. It consists of a lumped element-based resonant parasitic element that is introduced into the very near field of a coax-fed monopole. It is demonstrated that several idealized lossless versions are capable of achieving a near perfect impedance match to the source and, thus, have overall efficiencies near 100% without an external matching circuit. It is established that the entire system makes effective use of the radiansphere volume it occupies. The overall efficiencies are shown to remain high even when conductor losses are introduced. Potential frequency agility is also demonstrated.