A Broadband Pifa with Zeroth-Order Resonator Loading

A printed broadband planar inverted-F antenna (PIFA) with zeroth-order resonator (ZOR) loaded is proposed whose shorting strip of the PIFA is replaced by an inter-digital capacitor and thin inductive strip in series. The loaded inter-digital capacitor and thin inductive strip act as a shorting strip at the 3.1 GHz, which allows the antenna to maintain its regular performance. Around 2.0 GHz, the antenna with the inter-digital capacitor and thin inductive strip works on the zeroth-order resonance mode, which makes the physical size be independent of the wavelength. By merging the two modes, a broadband performance can be achieved. The size of the antenna is only 12.5 mm×7.81 mm×1.6 mm with single layer. The measured antenna bandwidth is 1.63 GHz (about 65%), total gain is above 2.5 dBi and the simulated radiation efficiency is over 90% in the working band. Especially the antenna has same direction of the radiation patterns in the broadband. In the end, the antenna with lumped elements loading is also discussed.