Notched circular microstrip patch antennas with bow tie shaped aperture coupling for improved axial ratio bandwidth
This paper presents improvement in the axial ratio bandwidth obtained with notched circular microstrip patch antennas. The antenna is electro-magnetically fed with bow tie shaped apertures as compared to a full circular microstrip patch of the same configuration. The simulation has been carried out using a method of moments based computer aided design tool. A near to 1:1 ellipticity to impedance bandwidth has been obtained in simulation with the above configuration. It is observed that by cutting electrically small rectangular notches (W/sub /spl eta//=/spl lambda//sub 0//25 and L/sub /spl eta//=/spl lambda//sub 0//20) into the circular patch parallel to the current lines significantly improves the ellipticity bandwidth without changing its impedance bandwidth. The current distribution of the notched patch remains unaltered and hence the radiation pattern is also not affected. This has been verified from the simulated results. In simulation 2:1 impedance bandwidth of 34% and 3 dB axial ratio bandwidth of 33% has been achieved with the above geometry. An improvement of 6% in ellipticity bandwidth is obtained over a full circular patch antenna of same configuration. The use of dielectric foam makes the antenna light weight and low cost. The above features make it an ideal element for wide band applications as required for personal, mobile satellite and wireless communication systems.