Page 108 - 2023-Vol19-Issue2
P. 108
104 | Abdulzahra, Alnahwi & Abdullah
Fig. 4. (a) A small slit for integrating diode and (b) the Fig. 5. (a) The second slit on the lower corner and (b) The
reflection coefficient response. reflection coefficient response.
effect of slit width g and slit length d on the OFF-state antenna V. RESULTS
reflection coefficient response is shown in Fig. 8. The dual-
band response and the wideband response are both affected The antenna reflection coefficient at the diode ON-state is
by the variation the parameter d.At the wideband mode, the illustrated in Fig. 9. The -10 dB bandwidth of the antenna
bandwidth decreases as the value of d increases.For the dual- covers the range from 2.95 GHz to 8.2 GHz. When the diode
band mode, it controls the matching of the second is at OFF-state, the effective length of the radiator is changed
due to altering of surface current distribution so that the corre-
resonant frequency because the slit is located at the shorter sponding response shows a dual-band that resonate at 3 GHz
monopole that is responsible for the generation of that res- and 6GHz with reflection coefficient values of -27.78 dB and
onant frequency. At d equal to 3mm, a wide bandwidth for -40.7 dB, respectively, as shown in Fig. 10. In addition, the
the wideband mode and good matching characteristics for the fractional bandwidths are 19% at 3 GHz and 47% at 6 GHz
dual-band mode are guaranteed. At both wideband and dual- band.
band, the parameter g does not cause a noticeable influence
on both modes, but g=0.5 mm provides better matching than Fig. 11 shows the proposed antenna simulated surface
the other values especially at the second resonant frequency. current distributions at the OFF-state. At 3GHz, the major-
ity of the currant is concentrated at the longer monopole,
Overall, antenna dimensions are critical parameters that while the majority of the current is concentrated at the shorter
need to be optimized to achieve the desired operating charac- monopole and the lower slit at 6 GHz. In addition, Fig. 12
teristics. A careful parametric study of antenna dimensions shows the proposed antenna surface current distributions at
can help in designing antennas that are efficient, compact, and the ON-state at the three resonant frequencies of the antenna.
well-suited for IoT applications. The proposed antenna final As expected, the first resonant frequency results in a current
structure is optimized as shown in Table II, as determined by covering the entire patch. Meanwhile, the second and third
the parametric study. The CST Microwave Studio software is resonant frequencies result in current concentrations at two
used to obtain all of the simulation results [23]. and three different regions, respectively, along the edge of the
patch.
