Figure 11 3D radiation pattern of the proposed fractal MPA
array at (a) 5.35 GHz (b) 7.78 GHz (c) 9.47 GHz
SURFACE CURRENT DISTRIBUTION
To determine the influence of mutual coupling between the two array
elements, Figure 12 (a-f) shows the current distribution at three
resonant frequencies of 5.35 GHz, 7.78 GHz and 9.47 GHz. As shown in
Figure 12 (a-f), the funnel-shaped stub and slotted ground plane
decouples the energy from the fractal radiators and are mainly
responsible for improving the isolation level between the two ports.
This is also validated by the parametric analysis of the ground plane
presented in Section 2. For port-1 excited by simulated 1W of power at
the feed point (port-2 deactivated by 50 Ω load), the decoupling
structure (inserted in the ground plane) allows a very small amount of
current to flow through the non-activated port-2 for all three
resonances. For activated port-2 and port-1 terminated, a similar
reduction of coupling current is observed. Hence, the proposed fractal
MPA array exhibits good isolation performance throughout the UWB of
operation.