A Small and Bandwidth-Extended Dipole Antenna With Nonperiodic Left-Handed Transmission Line Loading

A miniaturized and bandwidth-extended dipole antenna using a nonperiodic left-handed (LH) transmission line is proposed. The LH transmission-line structure is composed of a ladder network of unit cells having different series capacitors and shunt inductors. The radiation performance of a four-cell nonperiodic LH dipole antenna is compared to the periodically loaded antenna with the same size. Simulated and measured results show that, when the length of the antenna is about 0.2λ
₀
, a 4.8% impedance bandwidth for | S
₁₁
| ≤ - 10 dB can be obtained through appropriately nonperiodic LC loading without any additional matching network, and well-behaved radiation patterns have been displayed.