Ultra wideband planar antenna with spurline for subband rejection

The design of a compact ultra wideband planar antenna with subband rejection capability is presented. A spurline is incorporated in the microstrip feeder of the antenna to act as a bandstop filter, hence enabling the rejection of any undesired band within the passband of the antenna. Results of a parametric investigation are presented to show effect of the spurline parameters on width of the rejected subband. The investigation shows that increasing the slot and spurline widths increases width of the rejected subband. Three samples of the proposed antenna were designed and manufactured. One of the developed antennas does not contain spurline, whereas the other two contain spurlines with different dimensions. The designed antennas feature a compact size of 25 mm × 25 mm. Results of the simulation and measurement show that the designed antennas have a bandwidth from 3 GHz to more than 11 GHz. The results also show that the use of the spurlines in the microstrip feeder of the antennas efficiently rejects any undesired subband, such as the 4.9-5.9 GHz band assigned for IEEE802.11a and HIPERLAN/2. The gain of the antennas with spurline is about 2.5 dB at the passband, while it is less than -15 dB at the rejected subband. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 725-728, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23205