Multi-notch slot loaded wide band planar plate monopole antenna

A tuneable notch through the use of a small modified U-slot (MU-slot) in a wideband, 3-16-GHz, planar monopole plate antenna is presented. The MU-slot shape with its low width and long effective perimeter length (long current length) can result in a notch even at the lower frequency limit of the antenna. By optimising the MU-slot parameters and their relative positions, the centre frequency, the return loss level and bandwidth of the notch can be controlled. Based on slot current length, a formula for the notch centre frequency is derived. Also, because of the low width of the proposed slot, several MU-slots can be placed on top of each other along the axis of the monopole antenna to produce multiband notch behaviour. Based on the height of the given monopole antenna, up to four tuneable notch bands with good characteristics are shown. Simulation and measurement results are presented and discussed.