A novel design for monopole antennas with wideband operation and stable radiation patterns is described. The proposed monopole antenna has a three-dimensional ring-shaped ground plane, and it can be treated as a monopole-loop composite antenna. Two pure resonant modes are simultaneously excited in the antenna structure, and their resonant frequencies are respectively at 2.45 and 5.4 GHz. By introducing a pair of shorting posts into the ground plane, the two resonant modes can be coupled together. The resultant impedance bandwidth (VSWR < 2) is about 70% with respect to the center frequency 4.5 GHz. Moreover, a stable bi-directional radiation pattern with a peak gain of 5 dBi and a cross polarization level of less than −15 dB is obtained within the impedance bandwidth. For the proposed antenna, parametric analyses are performed and an antenna prototype is also constructed. Both measured and simulated results are given.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Electrical and Electronic Engineering