This is observable by looking at the surface current density along the entire structure at 1.6 GHz in Figure 3a, where it is seen that the integration of the arms does not change the current distribution on the main tapered strips. As shown in Figure 4, the new arms do not change or shift the other resonances of the conventional Vivaldi antenna. As indicated, it is easy to find that by integrating the new arms into the conventional structure, another resonance at 800 MHz is created which shifts the lower edge of cut-off from 1480 MHz to 720 MHz resulting in antennas’ size reduction by 51%. In this manuscript, we investigate the possibility of integrating another resonator into the antipodal Vivaldi antenna, which could help to reduce the size of antipodal Vivaldi antennas, without compromising the radiation characteristics.įigure 4 shows the reflection coefficient of the AVA structure with/without arms. It should be noted that increasing the length of the strips shifts the cut-off frequency of the antipodal antennas to lower frequency with the cost of having a larger antenna.
In addition, the antenna gain for all four cases in Figure 1b shows that the width of tapered strips in antipodal antennas affects mainly the antenna gain. Although m 1 can be used for antenna matching, this variable cannot be obviously utilized for antenna size miniaturization.
As shown in Figure 1b, by changing the width of tapered strips, the antenna cut-off frequency changes between 1.55 GHz to 1.4 GHz. To investigate the effect of tapered strips’ width of the antenna on cut-off frequency and antenna size miniaturization, four cases with different widths of tapered strips of 10 mm, 22 mm, 50 mm, and 80 mm are considered in Figure 1. Figure 1a shows conventional antipodal antennas with different widths of tapered strips labeled as m 1.
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