Low-Dispersion Leapfrog WCS-FDTD with Artificial Anisotropy Parameters and Simulation of Hollow Dielectric Resonator Antenna Array
Abstract : An optimized three-dimensional one-step leapfrog finite-difference time-domain (FDTD) method has been investigated, which is with a weakly conditional stability (WCS) to reduce numerical dispersion further. By introducing the artificial anisotropy parameters in a cross-correspondence manner, the phase velocity error is effectively limited without additional computational time and memory cost. An auxiliary field variable is adopted to simplify the iterative formulae with few additional processes; and the same stability has been validated between methods of conventional leapfrog WCS-FDTD and ourselves. Moreover, much lower numerical dispersion is shown to withstand larger Courant-Friedrich-Levy number under the same error condition. To verify our method efficiently, a newly designed hollow dielectric resonator antenna (DRA), instead of a solid one, is conducted effective calculation. Furtherly, two forms of four-elements arrays have been developed with the DRA element above; and a T-shaped power divider are designed as a fed-network and subjected to calculations and experimental analyses. Reflection coefficients and radiation patterns are shown the effectiveness of both DRA and arrays. The most noteworthy aspect is that our low-dispersion WCS-FDTD scheme can be effectively simulated the hollow DRA and arrays, and with excellent performance in terms of memory occupation, calculation accuracy, and efficiency.
? In this article, a hollow DR exited by transformer type microstrip feedline covering 3.28 to 10.4 GHz of the UWB band is proposed.
? The concept of hollow DRA for the UWB range is validated in the proposed design.
? Millimeter-wave (mm-Wave) frequency bands have been selected for 5G applications as a response to the demand for higher data transmission rates in wireless communications.
? One of the challenges in these bands is the increased link loss due to the reduced wavelength and atmospheric absorption.
? DRAs consist of volumetric dielectric structures that are excited via an electromagnetic coupling mechanism, such as a microstrip line, an aperture in a conducting plane or a feeding probe.
? In the conventional CDRA design, the placement of the DR on top of the ground plane, where the radiation slot is located, is done manually, which leads to alignment precision issues that can easily impact the antenna gain and/or bandwidth.
? This thickness ensures that all higher order modes are cut off while having minimum impact on the performance of the antenna.
? This coupling will impact the radiation pattern, the appearance of grating lobes and the impedance matching.
? It is found that the width of center elements has greater impact on the current distribution of array than the width of outer elements.
• The proposed design presents a tapered current amplitude distribution by using DRA element width gradation method, and low side-lobe level (SLL) characteristic can be obtained.
• To validate the performance of the proposed design, the conformal array is fabricated and measured in an anechoic chamber.
• The measured results of the fabricated prototype demonstrate that the proposed design has the potential to be applied to wireless communication system with curved surface.
• A conformal array is firstly constructed based on the eight curved DRA elements with the same dimensions of the proposed DR element.
• Compared with the DRA arrays in and, the proposed structure shows higher gain and lower SLL.
? A grooved and grounded superstrate is introduced to facilitate the alignment of the individual array elements while enhancing the overall performance of the antenna array.
? The performance of the proposed stack is evaluated numerically and compared with measured data.
? These techniques have led to gain, efficiency and bandwidth performance that are better than the printed antennas.
? This becomes even more critical at higher frequencies where high alignment precision and tight size tolerances are required to avoid performance degradation.
? Consequently, mm-Wave antenna systems are required to provide high gain and high efficiency.
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