CHARACTERISTIC MODES ANALYSIS OF CPW-FED UWB MONOPOLE ANTENNA FOR SHORT-DISTANCE WIRELESS COMMUNICATIONS

Ultra-wideband (UWB) monopole antennas are broadly used in wireless communications. A common problem with present planar UWB antenna designs is that the changes in the ground-plane size greatly affect its radiation performance. This is because variations in antenna dimensions influence the characteristic modes that are excited on the ground plane, which directly affect the impedance and radiating mechanism of the antenna. In order to solve this problem, the proposed work uses a technique, such as cutting slots on the ground structure. Characteristic mode analysis (CMA) is applied to obtain physical insight into the model behavior of the slots. By introducing the slots with optimal dimensions into the ground plane, the slot modes are generated and create a strong coupling with the modes of the ground plane. This coupling establishes the model behavior of ultra-wideband monopole antennas insensitive to modifications in ground-plane dimensions, thus effectively reducing the antenna's dependence on ground-plane dimensions. Using this technique, a CPW-fed UWB monopole antenna is developed and analyzed to observe how the slots affect the time- and frequency-domain properties of the proposed antenna. There is a good agreement between the measurement and simulation results.