Design of Multi-band Small Antenna Based on Single Split-Ring Resonator

To use the single split-ring resonator （SRR） as a basic unit cell for small antenna with multi-band frequency response is proposed. The structure of antenna is consisted of a single spilt-ring resonator and a coupled microstrip line. The designed antenna is numerically optimized with CST Microwave Studio. The radiation properties of the antenna show that there are three frequency bands among which two bands are 1.3 GHz and 2.1 GHz ultra-widehand （UWB）, respectively, where Sll is less than - 10 dB. The gain at every frequency for the multi-hand antenna is above 2.6 dBi, and it increases monotonously with the frequency in the two UWB.

Effects of oblique incidence on terahertz responses of planar split-ring resonators

Effects of oblique incidence of terahertz waves on the response of planar split-ring resonators are investigated, both experimentally and by simulation. It is found that the incident angle dependent phase delay and coupling conditions of neighboring split-ring resonator （SRR） units play important roles and greatly change both the transmission and reflection spectra for the resonant feature of linear charge oscillations. Our results show that the SRR structure-supported magne- toelectric couplings at oblique excitation are trivial and can be ignored. A highly symmetric response is found in the cross-polarization effects, which may manifest the bianisotropic properties of the SRR system but this needs further study.

Band-stop optical nanofilters with split-ring resonators based on metal–insulator–metal structure

Novel band-stop filters with circular split-ring resonators based on the metal-insulator-metal （MIM） structure are presented, with their transmission properties of SPPs propagating through the filter simulated by the finite-difference time-domain （FDTD） method, The variation of the gap of the split ring can affect the transmission characteristics, i.e., the transmission spectrum of SPPs exhibiting a shift, which is useful for modulating the filter. Linear and nonlinear media are used in the resonator respectively. By varying the refractive index of the linear medium, the transmission properties can be changed obviously, and the effect caused by changing the incident intensity with a nonlinear medium is similar. Several resonant modes that are applicable can be enhanced by changing the position of the gap of the split ring. Thus, the transmission properties can be modulated by adjusting the size of the gap, varying the refractive index, and changing the incident intensity of the input light. These methods may play significant roles in applications of optical integrated circuits and nanostructural devices.

Expanding the bandwidth of planar MNG materials with co-directional split-ring resonators

An effective approach to expand the bandwidth of negative permeability of small-sized planax materials is proposed. Based on qualitative analysis of equivalent circuit models, the fractional bandwidth of an μ-negative （MNG） material is expanded from 3.53% up to 12.87% by adding split-ring resonators （SRRs） and arranging them by proposed steps. Moreover, the experimental results validate the effectiveness of bandwidth-expanding methods, which is promising for the extensive application of metamaterials in the microwave field.

Experimental Study on Split-Ring Resonators with Different Slit Widths

Metamaterial one-dimensional periodic structures are composed of split-ring resonators, which can display electric permittivity and magnetic permeability simultaneously negative, are studied experimentally. In the present study, each resonator is made up of two concentric circular copper rings patterned on a substrate of kapton, with slits diametrically opposite each other and with the line of the splits along the longitudinal direction of the periodic array containing seven split rings evenly spaced. The experiments consist in inserting the metamaterial slab into a square waveguide of side length 6 mm, corresponding to a cutoff frequency of 25 GHz. Transmission bands due to magnetic and electrical responses are identified for slits with aperture widths of 1 mm and 2 mm, centered at 5.67 and 6.12 GHz frequencies, respectively, values well below the 25 GHz frequency cutoff, so characterizing a medium with negative permeability and permittivity.

Advanced high-pressure plasma diagnostics with hairpin resonator probe surrounded by film and sheath

The hairpin probe using microwave resonance in plasma is applicable to high pressure 1.33 ×10^3-1.01×10^5 Pa）） as developed recently. In this work, an analytic model of the hairpin resonator probe surrounded by a thin dielectric layer and a sheath layer is proposed. The correction factor due to these surroundings is analytically found and confirmed by electromagnetic field finite difference time domain simulation, thus enabling the accurate measurement of electron density in a high-pressure non-equilibrium uniform discharge.

Characteristic plume morphologies of atmospheric Ar and He plasma jets excited by a pulsed microwave hairpin resonator

Different discharge morphologies in atmospheric Ar and He plasmas are excited by using a pulsed microwave hairpin resonator.Ar plasmas form an arched plasma plume at the opened end of the hairpin,whereas He plumes generate only a contracted plasmas in between both tips of metal electrodes.Despite this different point,their discharge processes have three similar characteristics:(i)the ionization occurs at the main electrode firstly and then develops to the slave electrode,(ii)during the shrinking stage the middle domain of the discharge channels disappears at last,and(iii)even at zero power input(in between pulses)a weak light region always exists in the discharge channels.Both experimental results and electromagnetic simulations suggest that the discharge is resonantly excited by the local enhanced electric fields.In addition,Ar ionization and excitation energies are lower than those of He,the effect of Ar gas flow is far greater than that of He gas,and the contribution of accelerated electrons only locates at the domain with the strongest electric fields.These reasons could be used to interpret the different characteristic plume morphologies of the proposed atmospheric Ar and He plasmas.

A Modified Split⁃Ring Resonator Antenna for Radio Frequency Identification Tag

A compact antenna formed by three concentric split rings for ultra-high frequency(UHF)radio frequency identification(RFID)tag is proposed in this paper.The antenna is composed of two parts,an outer short-circuited ring modified from a traditional split-ring resonator(SRR)antenna and an inner SRR load,so the antenna can be regarded as a short-circuited ring loaded with SRR.According to the transmission line theory,to conjugate match with the capacitive input-impedance of a tag chip,the length of the short-circuited ring isλg/4 shorter than that of an open-circuited dipole of a traditional SRR antenna,whereλg is the wavelengh of the operating frequency.Hence,the size of the proposed antenna is more compact than that of the traditional SRR antenna.Thereafter,the proposed antenna is simulated and optimized by ANSYS high-frequency structure simulator(HFSS).The impedance,efficiency,and mutual coupling of the fabricated antenna are tested in a reverberation chamber(RC).The results show that the size of the presented antenna is 83%smaller than that of the traditional SRR antenna and the proposed antenna can cover the whole UHF RFID operating frequency band worldwide(840—960 MHz).The measured read range of the tag exhibits maximum values of 45 cm in free space and 37 cm under dense tag environment.

Permittivity Measurement of Low-Loss Substrates Based on Split Ring Resonators

In this paper, we present the complex permittivity measurement of low-loss substrates based on a microstrip-line-excited split-ring resonator (SRR). Permittivity of an unknown substrate is calculated based on the change in oscillation frequency of SRR caused by the material-under-test (MUT) above the SRR. Theoretical analysis and results of the simulations and experiments demonstrate the microstrip-line-excited SRR can be used to effectively improve measurement sensitivity. Simple equations for measurement of low-loss substrates using SRR are proposed and experimentally verified.

Tunable multiband terahertz metamaterials using a reconfigurable electric split-ring resonator array

We demonstrate micromachined reconfigurable metamaterials working at multiple frequencies simultaneously in the terahertz range.The proposed metamaterial structures can be structurally reconfigured by employing flexible microelectromechanical system-based cantilevers in the resonators,which are designed to deform out of plane under an external stimulus.The proposed metamaterial structures provide not only multiband resonance frequency operation but also polarization-dependent tunability.Three kinds of metamaterials are investigated as electric split-ring resonator(eSRR)arrays with different positions of the split.By moving the position of the split away from the resonator’s center,the eSRR exhibits anisotropy,with the dipole resonance splitting into two resonances.The dipole–dipole coupling strength can be continuously adjusted,which enables the electromagnetic response to be tailored by adjusting the direct current(DC)voltage between the released cantilevers and the silicon substrate.The observed tunability of the eSRRs is found to be dependent on the polarization of the incident terahertz wave.This polarization-dependent tunability is demonstrated by both experimental measurements and electromagnetic simulations.

Continuous Tera-Hertz wave transmission spectroscopy of Nb double superconducting split-ring resonator array

Transmission spectroscopy of two Nb double superconducting split-ring samples with different thicknesses on MgO substrates was measured by a continuous Tera-Hertz spectrometer.The transmission curves of two different samples with the thicknesses of 50 and 150 nm at 7.5 K show dips at 480,545 GHz,respectively,which origin from the different capacities and inductances of the samples.For the sample of 50 nm,the dip shifts to lower frequency,also decreases in depth and increases in width with temperature or field increasing below T c of Nb film,while the sample of 150 nm does not show such a phenomenon.This thickness-dependent transmission behavior is due to the kinetic inductance and conductivity change of superfluid electrons in Nb film and may suggest a practical tunable THz filter based on the thinner samples.

Terahertz radiation enhancement in photoconductive antennas with embedded split-ring resonators

This Letter proposes a novel method for enhancing terahertz(THz) radiation from microstructure photoconductive antennas(MSPCA). We present two types of MSPCA, which contain split-ring resonators(SRRs) and dipole photoconductive antennas(D-PCAs). The experimental results reveal that when the femtosecond laser is pumping onto the split position of the SRR, the maximum THz radiation power is enhanced by 92 times compared to pumping at the electrode edge of the D-PCA. Two π phase shifts occur as the pumping laser propagates from the negative electrode to the positive electrode. Analysis shows that photoinduced carrier charges move within the split position of the SRR.

The double coupled microwave resonance probes and application for diagnosing atmospheric pressure plasma jet

The double-coupled microwave resonance probe(DMRP)based on the hairpin probe is proposed for diagnosing atmospheric plasma jet(ne<1017 m-3).In this work,the resonance characteristics of DMRP are investigated by numerical simulation.It shows that two resonance peaks on the reflectance spectrum can be observed,and influenced significantly by some parameters,such as the probe separation,the distance to the handheld radio frequency atmospheric pressure glow discharge plasma jet(RF-APGDPJ)and the plasma electron density less than 1017 m-3.Based on two resonance modes of DMRP,the electron densities in the afterglow of RF-APGDPJ at the different rf powers and helium flow rates are diagnosed experimentally by matching the change of FWHM(Df1-Df1,airand Df2-Df2,air)measured by vector network analyzer with the simulated relation between the FWHM changes and the plasma density.

A New Type Four-Fold Microstrip Hairpin Line Bandpass Filter at 1.82 GHz for TranslReceive Communication Systems

A conventional hairpin-line resonator size is normally very large. This paper presents the design, simulation/optimization and measured results of a four-resonator multi-folded hairpin line microstrip bandpass filter at 1.82 GHz, with great reduction in size compared to the conventional hairpin line structure. In the proposed filter, the cross couplings have been realized between adjacent and non-adjacent resonators.

微带发夹型谐振器滤波器的实验研究

微带发夹型谐振器滤波器具有尺寸小、成本低、易于集成等优点,在微波平面电路的设计中有着良好的应用前景。此前已有一些文献对这类滤波器进行过研究,但一般都是只针对某一种特定的发夹型谐振器进行滤波器的分析设计,而没有对各种不同谐振器的性能指标与滤波器设计要求进行比较研究。本文使用几种不同的发夹型谐振器和不同耦合方式分别设计了三阶和四阶带通滤波器,通过实验对这几种谐振器滤波器进行了分析研究,得到了一些具有实际应用价值的结论。

一种毫米波微带带通滤波器的设计

基于小反射理论,引入Klopfenstein阻抗渐变线对传统发夹型谐振器结构进行改进,设计了一种相对带宽为8%的结构紧凑型毫米波带通滤波器。采用S参数的多项式综合方法得到耦合矩阵电路模型,利用三维电磁场全波仿真软件HFSS拟合出耦合系数与谐振器间距、外部品质因数与抽头位置的关系曲线,进而提取出耦合矩阵对应滤波器的物理尺寸。实测结果表明:在28.8 GHz^31.2 GHz频带内,该滤波器的插损小于3.0 dB,回波优于-17 dB,带外抑制大于40 dB@33 GHz,测试结果与计算结果吻合较好。

一种新型小型化宽阻带低通滤波器设计

对基于阶梯阻抗加载发卡型谐振器的多级椭圆函数微带滤波器进行了讨论。通过把两个谐振器用等效于电感的细微带线连接起来构成二级低通滤波器,其在阻带带宽和阻带衰减方面与单谐振器滤波器相比,取得了非常明显的改善。新设计滤波器的3dB截止频率位于2GHz,在2.5~25GHz具有小于10dB的衰减,而滤波器的面积仅等效于0.081λg×0.096λg（λg是在截止频率2GHz的导波波长）,证明了此种谐振器在多级滤波器设计中的有效性。此外,为更好地理解此种滤波器工作原理,文中对单谐振单元滤波器的LC等效电路进行了提取。与其它微带低通滤波器相比,此种滤波器在小型化、宽阻带方面具有明显优势,可广泛应用于多种微波系统。

一种新颖的开口环地面缺陷结构低通滤波器

提出了一种新颖的具有陡峭边带和宽阻带的小型化低通滤波器。通过把开口谐振环地面缺陷结构(Split-Ring Resonator Defected Ground Structure,SRRDGS)与阶梯阻抗梳状谐振器结合,提高了滤波器的选择特性,同时获得了宽阻带。对所提出的结构作了加工并进行了实物测量,测试结果表明:滤波器选择特性大于160dB/GHz,在2.98GHz到8.2GHz范围内抑制度大于20dB,而占用面积仅为20×25mm2。

微带发夹式带通滤波器的计算机辅助设计

主要论述了目前广泛应用的发夹式带通滤波器的设计技术。该设计方法不同于传统的微波带通滤波器,其理论简单,适合计算机仿真,易达到一次性设计成功的目的。最后给出了一个相对带宽为4%的五极发夹带通滤波器的设计实例,对发夹式带通滤波器的设计理论进行验证,取得了较高的一致性,为这种结构的滤波器的设计提供了一定的指导意义和参考价值。

小型化三维发夹型LTCC宽带带通滤波器

利用低温共烧陶瓷(LTCC)工艺,通过通孔互联实现了三维结构的发夹型宽带带通滤波器。该结构将谐振单元的横向尺寸转移到z轴方向实现,有效减小了滤波器的尺寸并且谐振器间的耦合系数为传统结构的1.6倍。利用五个谐振器结构实现较宽的频带(>30%)和较好的选择特性。设计并实际制作了中心频率10 GHz的LTCC带通滤波器,3 dB带宽为8.8～12.1 GHz,实测指标与设计仿真结果较为吻合。