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 0.387λ_L × 0.023λ_L × 0.0093λ_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 |S₁₁| ≤ −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.