This article aimed to optimize radar cross section (RCS) of the nose of flying objects using a new shaping method. In this method, parameters related to the scatterer shape can continuously change. Thus, precise optimization can be carried out. The nose of flying objects with desired size and sharpness was defined by mathematical formula with two parameters. The physical optics method was also applied to calculate RCS. Design curves were calculated by changing sharpness and size criteria of the nose of flying objects. Effects of changing frequency, angle of observation, and angle of incidence on RCS curves were also investigated.

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in Figure 13, where the voltage at the output of the structure is almost identical to the input voltage, with the difference resulting from slight deviations of the lumped-element parameters from their ideal values given by the relations in Eqs. (10a)-(10c). It can also be seen that the maximum voltage is located at the interface of the MNG and ENG structures, where resonance is generated. As one moves in opposite directions away from the interface, the voltage decreases uniformly. CONCLUSIONThe transparency in a CRLH-TL structure based on the ENG-MNG pair has been presented. The simulated and measured data demonstrate the transparency phenomenon in a conjugate matched pair of ENG and MNG structures. A circuit simulation of the voltage distribution along the structure has been presented in order to demonstrate the transparency of the structure. The stopband of a CRLH-TL has been shown to exhibit either ENG or MNG behavior, depending on the equivalent lumped-element parameters. OUT-OF-BAND IMPROVEMENT OF A SWITCHABLE NARROW BANDPASS FILTER

1 Abstract-Limited sensitivity and sensing range are arguably the greatest challenges in microwave sensor design. Recent attempts to improve these properties have relied on metamaterial-(MTM-) inspired open-loop resonators (OLRs) coupled to transmission lines (TLs). Although the strongly resonant properties of the OLR sensitively reflect small changes in the environment through a shift in its resonance frequency, the resulting sensitivities remain ultimately limited by the level of coupling between the OLR and the TL. This work introduces a novel solution to this problem that employs negative-refractiveindex TL (NRI-TL) MTMs to substantially improve this coupling so as to fully exploit its resonant properties. A MTM-infused planar microwave sensor is designed for operation at 2.5 GHz, and is shown to exhibit a significant improvement in sensitivity and linearity. A rigorous signal-flow analysis (SFA) of the sensor is proposed and shown to provide a fully analytical description of all salient features of both the conventional and MTM-infused sensors. Full-wave simulations confirm the analytical predictions, and all data demonstrate excellent agreement with measurements of a fabricated prototype. The proposed device is shown to be especially useful in the characterization of commonly-available high-permittivity liquids as well as in sensitively distinguishing concentrations of ethanol/methanol in water.

We have previously shown that a new class of Negative Refractive Index (NRI) metamaterials can be constructed by periodically loading a host transmission line medium with inductors and capacitors in a dual (high-pass) configuration. A small planar NRI lens interfaced with a Positive Refractive Index (PRI) parallel-plate waveguide recently succeeded in demonstrating focusing of cylindrical waves. In this paper, we present theoretical and experimental data describing the focusing and dispersion characteristics of a significantly improved device that exhibits minimal edge effects, a larger NRI region permitting precise extraction of dispersion data, and a PRI region consisting of a microstrip grid, over which the fields may be observed. The experimentally obtained dispersion data exhibits excellent agreement with the theory predicted by periodic analysis, and depicts an extremely broadband region from 960MHz to 2.5GHz over which the refractive index remains negative. At the frequency at which the theory predicts a relative refractive index of -1, the measured field distribution shows a focal spot with a maximum beam width under one-half of a guide wavelength. These results are compared with field distributions obtained through mathematical simulations based on the plane-wave expansion technique, and exhibit a qualitative correspondence. The success of this experiment attests to the repeatability of the original experiment and affirms the viability of the transmission line approach to the design of NRI metamaterials.

This paper investigates the propagation characteristics of circular waveguides whose interior surface is coated with a thin metamaterial liner possessing dispersive, negative, and near-zero permittivity. A field analysis of this system produces the dispersion of complex modes, and reveals in detail intriguing phenomena such as backward-wave propagation below the unlined waveguide's fundamental-mode cutoff, resonant tunneling of power, field collimation, and miniaturization. It is shown how the waveguide geometry and metamaterial parameters may be selected to engineer the lined waveguide's spectral response. Theoretical dispersion and transmission results are closely validated by full-wave simulations.Comment: 8 pages, 8 figure

A novel miniaturized printed folded dipole antenna has been designed for narrowband sensing applications. It is shown that the antenna may be systematically engineered to achieve matching to a practical source impedance at frequencies well below its half-wavelength resonance using series-LC loading and asymmetrical arm widths. This approach is used to design an inherently well-matched antenna that does not require an external matching network and demonstrates approximately 75% miniaturization, excellent co-to cross-polarization separation, over 24 dB higher realized gain, and strongly improved radiation efficiency relative to an unloaded folded dipole of the same electrically small size. Experimental validation of a fabricated prototype demonstrates excellent agreement with simulations.

This paper presents experimental verification of below-cutoff transmission through miniaturized waveguides whose interior is coated with a thin anisotropic metamaterial liner possessing epsilon-negative and near-zero (ENNZ) properties. These liners are realized using a simple, printed-circuit implementation based on inductively loaded wires, and introduce an HE11 mode well below the natural cutoff frequency. The inclusion of the liner is shown to substantially improve the transmission between two embedded shielded-loop sources. A homogenization scheme is developed to characterize the liner's anisotropic effective-medium parameters, which is shown to accurately describe a set of frequency-reduced cutoffs. The fabrication of the lined waveguide is discussed, and the experimental and simulated transmission results are shown to be in agreement.