Abstract-A circularly polarized (CP) substrate integrated waveguide (SIW) cavity-backed antenna based on dual concentric, orthogonal slot split ring resonators is proposed and experimentally studied. The circularly polarized wave is generated by two split ring-slots etched in the upper metal layer of the SIW cavity resonator. These two slots are excited by a coaxial probe located in the gap of the external slot split ring to radiate the right-handed circularly polarized (RHCP) wave. By rotating the dual split slot ring resonators and the probe by 45 degrees relative to the backed cavity, a better match characteristic and a slightly higher radiation gain are obtained. Because of the concentricity of radiant split ring slots, the beamwidth of the circular polarization is obviously increased. From the experimental results, the impedance bandwidth was 10.8% for the reflection coefficient less than −10 dB, the axial ratio (AR) bandwidth was 1.54% for the AR less than 3 dB, and the RHCP gain was 4.44 dBic. Moreover, the 3-dB axial ratio beamwidth at the centre frequency of 10.40 GHz has been extended to 142 • in the angular range from −78 • to +64 • .
Abstract-A rotationally symmetric short-circuited stub-loaded structure is proposed to design a microstrip-line bandpass filter with two transmission zeros near the lower and upper cut-off frequency edges of operating millimeter-wave bands. Furthermore, interdigital coupled-lines and additional resonators are integrated into the proposed rotationally symmetric bandpass filter to improve the out-of-band rejection. As design examples, the in-band and out-of-band performances of two filter prototypes using single layer microstrip-lines are designed and experimentally examined. The measured results show that the filter without any interdigital coupledlines achieves a passband insertion loss of 0.97 dB at 40 GHz and out-ofband rejection of larger than 23 dB, while the filter with the interdigital coupled-lines realizes the suppressions in lower and upper-bands of, respectively, larger than 30 dB and 19 dB for the overall insertion loss of 2.1 dB at 40 GHz.
A novel four-step weakly conditionally stable hybrid implicit-explicit finite-difference timedomain (HIE-FDTD) algorithm in three-dimensional (3-D) domains is presented in this paper, which is suitable for a finer discretization in one dimension. Based on the exponential evolution operator (EEO), the Maxwell's equations in a matrix form can be split into four sub-procedures. Accordingly, the time step is divided into four sub-steps. In addition, by taking second-order central finite-difference approximation for both the temporal and spatial derivatives, the formulation of the proposed fourstep HIE-FDTD method is obtained. The proposed four-step HIE-FDTD algorithm is implemented, in which the implicit scheme was applied only in one direction with a fine grid, and the explicit scheme was applied in two other directions with coarser grids. Compared with the existing HIE-FDTD methods, the proposed method has a weaker Courant-Friedrichs-Lewy (CFL) stability condition (Δt ≤ 2Δx/c and Δt ≤ 2Δz/c), which means that the proposed method can improve computational efficiency by taking larger time step size. Since the CFLN stability condition of the proposed method is determined by the smaller grid size of the two coarse grid sizes, the proposed method is suitable for analyzing the electromagnetic objects with fine structures in one direction effectively. Besides, the numerical dispersion analysis is given, and the comparisons of the numerical dispersion analysis among the proposed method, traditional FDTD method, ADI-FDTD method, and two existing HIE-FDTD methods are given. Finally, to testify the computational accuracy and efficiency, numerical experiments of the five FDTD methods are presented.
An X-band pyramidal horn antenna with a fourth order Chebyshev filtering function is presented in this paper. Four resonators are implemented in linear rectangular waveguide in the filter design. The last stage resonator provides not only resonance pole but also radiation function. To achieve high directivity, a pyramidal horn is attached to the filter output port, with negligible effect on the filter performance. Theoretical results are calculated based on the coupling matrix between the resonators. Finally, a pyramidal horn antenna operating at 10 GHz is designed and fabricated for demonstration. The measured results have found to be in good agreement with the simulated ones.
Abstract-A circularly polarized (CP) substrate integrated waveguide (SIW) cavity-backed slot antenna is proposed. A slot split ring (SSR) etched on the top metal surface of an SIW resonator is employed to generate the right-handed circularly polarized (RHCP) wave. The proposed antenna is excited directly by a coaxial probe with a proper distance from the symmetric axis of the SSR resonator. A prototype of the proposed CP antenna at the center frequency of 10 GHz is manufactured. As a result, the proposed antenna exhibits the advantages of both conventional planar antennas and metallic cavity backed antennas, including simple structure, compact size of 15.8×15.8 mm 2 , light weight, easy fabrication, high gain and wide axial ratio bandwidth. It is proved by experiment that an impedance bandwidth of 10.2% for the reflection coefficient less than −10 dB, an axial ratio (AR) bandwidth of 1.72% for AR less than 3 dB, and a RHCP gain 5.5 dBi have been obtained.
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