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Earthquake Science 2008年第1期21卷 91-97+109页

作者：曾宪伟赵卫明盛菊琴 Earthquake Administration of Ningxia Hui Autonomous Region Earthquake Administration of Ningxia Hui Autonomous Region Yinchuan 750001 China Lanzhou Institute of Seismology Lanzhou 730000 China

Mallat decomposition algorithm of wavelet packet transform can divide broader band into narrower ones with equal bandwidth and no overlapping each other. However, order by size of frequency within signal subspace is not in accordance with that of node label of decomposition tree. Therefore, it is not easy to determine frequency range of reconstructed signal from each node. In this paper, by analyzing the relationship between Mallat decomposition algorithm of wavelet packet transform and decomposition filter and setting operation rule of binary conversion of band labels into node labels, we find the corresponding relationships between nodes of decomposition tree and frequency bands of signal subspace. Then, the conclusion is verified by analog signals. Also, it shows that the ar- ranged rule of bands of signal subspace summarized in the paper is correct.

关键词： decomposition tree nodes signal subspace frequency bands

Th-Shaped Tunable Multi-Band Antenna for Modern Wireless Applications

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Computers, Materials & Continua 2023年第2期74卷 2517-2530页

作者： Wasi Ur Rehman Khan Muhammad Fawad Khan Muhammad Irfan Sadiq Ullah Naveed Mufti Usman Ali Rizwan Ullah Fazal Muhammad Saifur Rahman Faisal Althobiani Mohammed Alshareef Mohammad E.Gommosani Department of Telecommunication Engineering University of Engineering and TechnologyMardanPakistan Electrical Engineering Department College of EngineeringNajran UniversityNajranSaudi Arabia Department of Electrical Engineering University of Engineering and TechnologyMardan23200Pakistan Faculty of Maritimes Studies King Abdulaziz UniversityJeddahSaudi Arabia Ports&Maritime Transportation Faculty of Maritimes StudiesKing Abdulaziz UniversityJeddahSaudi Arabia Natural Science Department Faculty of Maritimes StudiesKing Abdulaziz UniversityJeddahSaudi Arabia

A compact,reconfigurable antenna supporting multiple wireless services with a minimum number of switches is found lacking in literature and the same became the focus and outcome of this *** was achieved by designing a Th-Shaped frequency reconfigurable multi-band microstrip planar antenna,based on use of a single switch within the radiating structure of the *** frequency bands(i.e.,2007–2501 MHz,3660–3983MHz and 9341–1046 MHz)can be operated with the switch in the ON switch *** the OFF state of the switch,the antenna operates within the 2577–3280MHz and 9379–1033MHz *** proposed antenna shows an acceptable input impedance match with Voltage Standing Wave Ratio(VSWR)less than *** peak radiation efficiency of the antenna is 82%.A reasonable gain is obtained from 1.22 to 3.31 dB within the operating bands is *** proposed antenna supports UniversalMobile Telecommunication System(UMTS)-1920 to 2170 MHz,Worldwide Interoperability and Microwave Access(WiMAX)/Wireless Broadband/(Long Term Evolution)LTE2500–2500 to 2690 MHz,Fifth Generation(5G)-2500/3500 MHz,Wireless Fidelity(Wi-Fi)/Bluetooth-2400 to 2480 MHz,and Satellite communication applications in X-Band-8000 to 12000 *** overall planar dimension of the proposed antenna is 40×*** antennawas designed,along with the parametric study,using Electromagnetic(EM)simulation *** antenna prototype is fabricated for experimental validation with the simulated *** proposed antenna is low profile,tunable,lightweight,cheap to fabricate and highly efficient and hence is deemed suitable for use in modern wireless communication electronic devices.

关键词： Antenna design reconfigurable antenna satellite communication frequency bands

Electromagnetically induced left handedness in a V-type four-level atomic system

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Chinese Optics Letters 2010年第12期8卷 1187-1190页

作者：张振清刘正东赵顺才郑军 Institute of Modern Physics Nanchang University Engineering Research Center for Nanotechnology Nanchang University School of Science Nanchang University School of Materials Science and Engineering Nanchang University

A closed four-level system in atomic vapor is proposed, which is made to possess left handedness by means of the technique of quantum coherence. The method of density matrix is utilized in view of the rotating-wave approximation and the effect of local-field in dense gas. The result of the numerical simulation shows that the negative permittivity and negative permeability of the medium can be achieved simultaneously （i.e., the left handedness） in a wider frequency band under appropriate parameter conditions. Furthermore, when analyzing the dispersion property of the left-handed material, we find that the probe beam can be controlled to change from superluminal to subluminal or vice versa via changing the detuning of the probe field.

关键词： frequency bands Probes

Propagation properties of the terahertz waveguide using a metallic nanoslit narrower than skin depth

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Chinese Optics Letters 2016年第7期14卷 90-93页

作者：杨洁林功伟钮月萍祁义红周凤雪龚尚庆 Department of Physics East China University of Science and Technology

A terahertz （THz） waveguide using a metallic nanoslit whose width is much smaller than the skin depth is analytically investigated. By taking some important physical properties into account, we derive a simple, yet accurate, expression for the effective index. We also study the changes in modal field and the attenuation coefficient in the whole THz region, and find some interesting physical properties. Finally, we verify that these theoretical analyses coincide with the rigorous nmnerical simulations. This research can be useful for various applications of THz waveguides made of metallic nanoslits.

关键词： frequency bands Nanostructures Physical properties

Multicolor coherence-induced negative refraction in three-level atomic system

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Chinese Optics Letters 2012年第12期10卷 71-74页

作者：郭洪菊张红军王春芳陈昱 Shanghai Publishing and Printing College College of Physics and Information Technology Shaanxi Normal University School of Science University of Shanghai for Science and Technology

Multicolor manipulation of negative refraction in a three-level A atomic system is theoretically investigated. Based on multicolor coherence, the negative refl-active index can be obtained with reduced absorption. The refractive index can also be controlled by changing the sun, of the phases of the sidebands in the trichromatic driving fields. By adjusting the sum phase, the refractive index can be varied between negative and positive in two different frequency bands. Furthermore, the frequency band corresponding to the negative refractive index is widened by increasing the intensity and the frequency difference of the trichromatic field.

关键词： frequency bands Light refraction

Polarization sensitivity contributes to multiple band spectra of one mid-infrared absorber

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Chinese Optics Letters 2014年第10期12卷 86-90页

作者：黎永前王斌斌许小轮苏磊 Key Laboratory of Micro/Nano Systems for Aerospace of Ministry of Education Northwestern Polytechnical University

The emerging perfect-absorber metamaterials （PAMs） provide an alternative material approach for the next generation of electromagnetic detection at any frequency band of interest. One type of dual cross-shaped PAMs is developed to obtain multiplex-band spectrum absorption at mid-infrared region. Three distinct absorption peaks are attributed to the polarization sensitivity excitation of the plasmonic resonance. The charge density distributions, which are excited by resonant electromagnetic waves passing through the PAMs medium, provide insights into the observed absorption behavior. We find that the retrieved optical properties of the PAMs including permittivity and permeability are still consistent with the sum of the Drude and Lorentz type models at wavelengths ranging from 2.0 to 10.0μm. Such multiplex-band absorption properties enable the proposed PAMs a powerful tool for the direct detection of multiple molecular vibrational structures, and for multiple spectra infrared detection.

关键词： Electromagnetic waves frequency bands Infrared devices Multiplexing Optical properties Polarization

Compact beam splitters based on self-imaging phenomena in one-dimensional photonic crystal waveguides

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Chinese Optics Letters 2012年第11期10卷 28-31页

作者：陈兵黄琳李永东刘纯亮刘贵忠 Key Laboratory of Physical Electronics and Devices of the Ministry of Education Xi'an Jiaotong University Institute of Information and Communication Engineering Xi'an Jiaotong University

A fundamental 1× 2 beam splitter based on the self-imaging phenomena in multi-mode one-dimensional （1D） photonic crystal （PC） waveguides is presented, and its transmission characteristics are investigated using the finite-difference time-domain method. Calculated results indicate that a high transmittance （〉95%） can be observed within a wide frequency band for the 1×2 beam splitter without complicated structural optimizations. In this letter, a simple and compact 1×4 beam splitter is constructed by combining the fundamental 1×2 beam splitter with the flexible bends of 1D PC waveguides. Such beam splitters can be applied to highly dense photonic integrated circuits.

关键词： Finite difference time domain method frequency bands Laser optics Optical instruments Optical waveguides Photonic crystals Structural optimization Time domain analysis Waveguides