CONCLUSION
A compact dual-port microstrip line fed MPA array with Koch curve
fractals for portable UWB-MIMO systems is proposed in this article. The
proposed fractal array occupies an overall area of 1433.5
mm2 (30.5 mm × 47 mm). The upper substrate layer
consists of two semi-circular patches joined with Koch curve fractals
(optimized up to 2nd order of iteration) and the lower
substrate layer consists of a reduced ground plane with slots and a
funnel-shaped decoupling structure. The radiating elements in the array
are kept at a distance of λ/2 to mitigate the effect of mutual coupling
between the ports. The simulated results show a wide frequency band of
4.395-10.184 GHz with a fractional bandwidth of 79.4 % (at a center
frequency of 5.789 GHz), the peak radiation efficiency of 88.8 % (at
6.2 GHz frequency) and a high isolation level
(S21/S12 ≤ -16.8 dB). The measured
S-parameter results cover the frequency band from 4.6-10.45 GHz (port-1,
S11) and 4.55-10.32 GHz (port-2, S22)
with fractional bandwidths of 77.7% GHz and 77.6 % respectively and
S21/S12 ≤ -19.3 dB. The proposed fractal
array exhibits low ECC (≤ 0.0021 (simulated), ≤ 0.0023 (measured)), high
DG (≥ 9.989 (simulated), ≥ 9.988 (measured)), high MEG (≥ -3.7 dB
(simulated) and ≥ -3.85 dB (measured)), low CCL (≤ 0.4 bits/s/Hz
(simulated, measured)) and acceptable TARC (-10 dB (simulated), -8.9 dB
(measured)) values which makes it an appropriate choice for portable and
high data rate UWB communication systems.