Study of Monopole Radiators for Planar Circuit Integration

Communication terminals for WLAN and similar systems require omni-directional antennas which can be used as a single radiator or in array and MIMO arrangements. The paper proposes to use low-profile top-loaded monopole and top-loaded folded monopole radiators and the integration into planar circuits where the radiators are directly fed (without a launcher) by microstrip line. The design and performance of both types is investigated in a simulation study and by experiment. High relative bandwidth of 25% is achieved for the folded monopole type with a height over ground as low as 0.09 free space wavelength.