Three‐dimensional folded antenna with ultra‐wideband performance, directional radiation and compact size

A compact ultra‐wideband (UWB) antenna with directional radiation is presented. The antenna has a low profile and does not need a large ground for its performance. The antenna is based on using a three‐dimensional folded structure that is modified using semi‐circular slots on bowtie‐shaped elements. The antenna's mechanism, its design guidelines and its optimisation are described thoroughly. A prototype of the antenna is fabricated and measured for performance verification. The prototype shows 77% fractional bandwidth (centred at 2 GHz) based on 10 dB return loss reference. The equivalent overall size of the prototype is ( λ eff /3) × ( λ eff /4) × 0.07 λ eff ( λ eff = effective wavelength at the lowest resonant frequency), which proves the compactness of the antenna. The antenna shows unidirectional radiation pattern with around 15 dB front‐to‐back ratio, −20 dB cross‐polarisation in the two principle planes and around 5 dBi gain. The antenna is prescribed for compact UWB applications that use the low 1–3 GHz frequency band.