Table 2 illustrates some important radiation properties for each iteration, such as, impedance bandwidth, efficiency, gain and ARBW. It's clear that most of the required specifications of antennas used for Wi-Fi and WiMAX can be achieved at the 2nd iteration due to improving the values of radiation properties during the progress of antenna configuration, especially the impedance bandwidth, efficiency, gain and an ARBW as shown in Table 2.
Also, the proposed fractal ring antenna is circularly polarized with an ARBW of 83 MHz, which is about 8.3% of the operating band.
Initially, ellipse dipoles with coupled fed reach a wide IBW for [absolute value of [S.sub.11]] [less than or equal to] -10 dB of 75.9% (0.80-1.78 GHz) and ARBW for AR [less than or equal to] 3dB of 76% (0.78-1.78 GHz).
By utilizing the SRT, the 3 dB ARBW and AR performance are substantially enhanced.
CRS has managed to enhance the performance of the reflection coefficient and the ARBW, and it also produces a good gain.
Model Width of Impedance CRS (mm) bandwidth (GHz) Ground-plane model 1 1 10.1-12.33, 23.73% Ground-plane model 2 0.1 8.2-10.76, 27%, Ground-plane model 3 0.2 10.62-11.60, 0.98%, Conventional model Without CRS 8.5-11.90, 36.48%, Model 3 dB ARBW (dB), % Gain (dBic) Ground-plane model 1 10.27-10.52, 2.6%, 0.5 to 1.5 Ground-plane model 2 8.8-9.85, 10.6%, 6.67 to 6.81 Ground-plane model 3 none 2.12 to 4.36 Conventional model 9.15-9.85, 7%, 6.79 to 7.03 Table 3.
3 indicate that including the horizontal strip and C shaped gap, greatly influence the ARBW.
5 (a), the measured impedance bandwidth of the proposed antenna is from 3 GHz up to 10.1 GHz (108 %) for VSWR < 2 and the measured 3 dB ARBW is increased from 3.2 GHz to 5.7 GHz (57 %) that is about 2.5 GHz.
3 dB ARBW
curves of the antenna (Antenna 1-3) are presented in Figure 5.
The 3 dB ARBW
results for the values of [L.sub.1], [L.sub.2] of the T-shaped microstrip line are shown in Figures 5(a) and 5(b).
It can be seen in Figure 5 that the ARBW
of the antenna increased to 4.7 ~ 4.95 GHz and 5.78 ~ 5.95 GHz for Ant.
Among these four antenna prototypes, the one with [l.sub.p] = 19.5 mm has the largest 3-dB ARBW
of 29.1% with respect to 2.52 GHz, the center frequency of the combined CP band of 2155-2890 MHz.