Considerable size reduction of dipole antenna with a compact and broadband balun

A compact and broadband balun is designed using a conventional right-handed transmission line (RHTL) and a left-handed transmission line (LHTL) with lumped elements only. The proposed balun maintains a phase difference of 180° ± 12° at the output ports for the frequency range of 1.27 GHz–2.69 GHz. Nevertheless, the circuit size is merely 9.5 mm × 12.7 mm. To verify the performance of the proposed balun, we attached it to a dipole-type antenna and observed that the return loss is greater than 10 dB for the frequency range between 1.86 GHz and 2.57 GHz. The radiation pattern and peak gain are similar to those of the dipole antenna with a conventional balun.