IEEE Access (Jan 2023)
Dual-Mode Characteristic Based on Miniaturized Metamaterial for Multiband Operation Utilizing Double-Layer Interdigital and Trisection Step-Impedance Techniques
Abstract
This paper presents a dual-mode characteristic for miniaturized metamaterial with a unit cell design based on an interdigital coplanar waveguide (ICPW) combined with trisection step-impedance to enable the three resonant frequency responses of 1.8 GHz, 3.7 GHz, and 5.8 Hz. In addition, the unit cell dimensions can be reduced from $\lambda $ /2 to $\lambda $ /8 due to the fact that the ICPW technique based on the CPW structure enhances the capacitive load between the transmission line and the side ground, thereby increasing the slow-wave on the transmission line. In addition, the trisection step- impedance will be incorporated and applied to the transmission line and cooperate with the unit cell structure’s capacitive load to effectively resonate at the desired frequency location. Moreover, the unit cell structure designed with the method above must be utilized as a double layer in which the structure on both sides is identical. The back structure will property the rod, which will cause the permittivity and permeability to be negative and closer to zero. This property of the proposed material allows for its utilization as a director at its first resonant frequency and as a reflector at the subsequent second and third resonant frequencies. The proposed metamaterial employs FR-4 printed circuit boards with a dielectric constant ( $\varepsilon _{r}$ ) of 4.4, a substrate thickness of 1.6 mm, a conductor thickness of 0.035 mm, and a loss tangent (tan $\delta $ ) of 0.04. The unit cell size is approximately 14 mm $\times 14$ mm. The unit cell will then be arranged as a $7\times 7$ array with an overall dimension of $98\times 98$ mm2 to evaluate an antenna’s performance. An antenna used for testing the proposed unit cell is a dipole antenna that propagates at a single frequency corresponding to the unit cell’s resonant frequency. At all resonant frequencies, the impedance matching of the dipole is less than −10 dB. At 1.8 GHz, 3.7 GHz, and 5.8 GHz, the dipole antenna gain is 2 dBi, 2.06 dBi, and 1.95 dBi, respectively. Moreover, the dipole antenna’s characteristics were simulated using the CST program in conjunction with the unit cell array. Based on the simulation and measurement results, the antenna with the unit cell array exhibits an impedance bandwidth of less than −10 dB at frequencies of 1.8, 3.7, and 5.8 GHz. The gains obtained from the simulation results are 5.49 dBi, 8.21 dBi, and 7.87 dBi, while the measurement results show gains of 5.73 dBi, 8.19 dBi, and 7.79 dBi, respectively. The simulated and measured outcomes demonstrate a substantial correspondence.
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