Abstract-This paper investigates the characteristics of electromagnetic wave propagation in biaxially anisotropic left-handed materials (BA-LHMs) theoretically and numerically. We discuss under what conditions the anomalous refraction or reflection will occur at the interface when a plane wave passes from one isotropic right-handed material into another BA-LHM. Meanwhile the refraction angle of the wave vector and that of the Poynting power are presented when the anomalous refraction takes place. According to the theoretical analysis, several sets of constitutive parameters of BA-LHMs are considered. Then the anomalous refraction or reflection of the continuous-wave (CW) Gaussian Beam passing from free space into BA-LHMs are simulated by the finite difference time domain (FDTD) method based on the Drude dispersive models. The simulated results are in agreement with theoretical results, which validates the theoretical analysis.
Abstract-The new definition of arbitrary isolation between antennas is proposed according to the microwave network theory. The multilevel fast multipole algorithm (MLFMA) with the near-field preconditioner is implemented to predict the isolation between multiple antennas on electrically large platforms over a wide frequency range. Experimental results show that the isolation defined in this paper is more practical than the traditional one. Finally the radiation pattern and the isolation results for the ultra-shortwave antennas mounted on full-scale models such as an aircraft and a ship are obtained and discussed, which can give significant instructions to the platform-mounted antennas design.
Abstract-The Goos-Hänchen shift on the surface when an optical beam is obliquely incident from one isotropic right-handed material (RHM) into another biaxial anisotropic left-handed material (BA-LHM) is numerically studied with the finite difference time domain (FDTD) method based on the Drude dispersive models. The analytical expression of the Goos-Hänchen shift is firstly presented, moreover the condition for the existence and the sign of the Goos-Hänchen shift are also discussed. According to the theoretical analysis, several sets of constitutive parameters of BA-LHM are considered. The simulated results are in agreement with theoretical results, which validate the theoretical analysis.
Abstract-In this paper, a novel dual-band bandpass filter (BPF) based on a single short-ended dual-mode resonator (SEDMR) is presented. According to the voltage distribution of the resonator, two pairs of loaded open stubs, inside and outside of the resonator, are utilized to tune the center frequency and the external quality factor of the first passband respectively, while there is no influence on the second passband. Meanwhile, source-load coupling is introduced to produce transmission zeros to improve the passband selectivity and band-to-band isolation. For demonstration, a dual-band filter working at 1.52 GHz for GPS and 3.5 GHz for WiMax is designed, fabricated and measured with insertion losses of 1.47 and 0.95 dB. In addition, two transmission zeros, introduced by source-load coupling, located at 2.19 and 2.67 GHz between the first and second passband improve passband selectivity and band-to-band isolation better than 50 dB.
Abstract-A hybrid tuning method for microwave filters is presented in this paper. This novel tuning technique is based on the combination of the Cauchy method and aggressive space mapping (ASM) technique. Cauchy method is applied to determine the characteristic polynomials of the filter's response, then the parameters (coupling matrix) of the low-pass prototype is extracted from the characteristic polynomials. The aggressive space mapping is used to optimized the fine model to guarantee that each step of a tuning is always in the right direction. The validity is verified by two examples. One deals with the fourresonator cross-coupled filter and the other one is an direct coupled six-resonator filter.
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