Bandwidth and directivity enhancement of an internal folded monopole antenna loaded by interdigital capacitor for ultra‐high‐definition television applications

An internal antenna with bandwidth and directivity enhancement was developed for operation in ultra‐high‐frequency bands (UHF: 470‐771 MHz, bandwidth: 48.5%) for ultra‐high‐definition television (UHD‐TV) applications. The antenna is integrated into a 49‐in. TV model, which is surrounded by a bezel frame made of polycarbonate‐acrylonitrile butadiene styrene (PC‐ABS) plastic. This material was also used as a substrate in fabricating the antenna. The antenna has a compact size of 0.387 λ L  × 0.023 λ L  × 0.0093 λ L (where λ L is the wavelength at the lowest operating frequency) and is fed by a 50 Ω coplanar waveguide (CPW) feedline. To achieve wideband operation and directional radiation, the proposed internal antenna was designed on the basis of a folded monopole antenna loaded with parasitic strips and an interdigital capacitor. The experimental results showed that the antenna exhibits a wide impedance bandwidth of 86% (400‐1000 MHz) under the criterion | S 11 | ≤ −6 dB (Voltage Standing Wave Ratio (VSWR) ≤ 3), a directional radiation pattern with a maximum realized gain of 5.2 dBi, and a radiation efficiency of more than 68%. These findings indicate that the antenna is suitable for UHD‐TV applications.