Investigation into a Folded Wideband Monopole Antenna for Use in Portable Devices

This paper presents investigations into a compact antenna for use in portable devices to access almost all modern wireless services from about 800MHz to 6GHz. Initially, a microstrip-fed planar monopole of quarter-elliptical shape on FR-4 substrate is designed to generate a wide impedance bandwidth. This radiating element is augmented with a parasitic microstrip stub and a ground-plane cut to improve wideband performance. To reduce its projection area, the planar monopole is folded. The folded antenna occupies a volume of 13mm x 50mm x 5.6mm. It operates over two wide bands between 0.85 and 3.8GHz, and 4.9 and 6GHz, with reference to 6dB return loss (VSWR 3:1). Its radiation patterns are omnidirectional in the lower band and deteriorate at higher frequencies. The corresponding gain varies between 1.5 and 7dBi.