Feed gap influence for printed multiple ring fractal antennas

A simple structure of printed multiple ring fractal antennas has already been investigated in our previous work, which demonstrate better performance than conventional antennas as dual-band or triple-band element This paper presents the feed gap influence for printed multiple ring fractal antennas. As the ground plane is under part of the feed line, the feed gap between antenna and ground plane is the key point for impedance matching and obtaining good performance of radiation pattern and S-parameter. After comparing a large number of simulation results, an expression is given to indicate the relationship between feed gap h and the radius of biggest ring R. The single antenna unit has the potential of operating in several of the currently existing systems such as GSM, UMTS, WLAN and Bluetooth