Dual-mode composite-right/left-handed transmission line ring resonator

The phase response of composite right/left-handed transmission lines is used in the design of a dual-mode ring resonator. The phase can be designed to change the spacing of the resonant modes. Simulation and measured results for a dual-mode ring demonstrate this technique. The designed structure exhibits the elimination of the singlemode resonance at the second harmonic.     

All-fiber compound ring resonator with a ring filter

The new all-fiber compound ring resonator has two rings: a primary one that serves as a resonator, and a secondary one that serves as a filter. The main contribution of this resonator is to increase the free spectral range by choosing the fiber lengths in the compound ring cavity. This resonator with a large free spectral range can be readily used as a doped fiber laser. The optimum resonant conditions of the resonator are discussed by using an equivalent model and by the transfer matrix method. The frequency responses of the output and of the circulating intensities are given. Mode suppression by the vernier effect is demonstrated. Comparison with a fiber Fox-Smith resonator is also presented     

Dynamic response of a fiber-optic ring resonator: Analysis with influences of light-source parameters

In practice, dynamic behavior of fiber-optic ring resonator (FORR) appears as a detrimental factor to influence the transmission response of the FORR. This paper presents dynamic response analysis of the FORR by considering phase modulation of the FORR loop and sinewave modulation of input signal applied to the FORR from a laser diode. The analysis investigates the influences of modulation frequency and amplitude modulation index of laser diode, loop delay time of the FORR, phase angle between FM and AM response of laser diode, and laser diode line-width on dynamic response of the FORR. The analysis shows that the transient response of the FORR strongly depends on the product of modulation frequency and loop delay time, coupling and transmission coefficients of the FORR. The analyses presented here may have applications in optical systems employing an FORR with a laser diode source.     

Compact hexagonal open-loop resonator bandpass filters using capacitive side-coupled stub and spurline technique

Compact quasi-elliptic bandpass filters using hexagonal open-loop resonators are presented. To miniaturise circuit size, a pair of capacitive side-coupled stubs and two pairs of spurlines are placed skilfully into the filter structure. The new filter operating at 1.65 GHz was analysed, simulated and fabricated. Good agreement between simulations and measurements verified the validity of the methodology. Moreover, the circuit size only occupies 21.1 x 14.1 mm2 (?0.21λg x ≅0.14λg).     

Rigorous analysis of a circular patch antenna excited by amicrostrip transmission line

Boundary conditions are enforced on a portion of the microstrip feed line as well as the patch antenna. The integral equation for the unknown currents on the antenna and feed is solved by applying the Galerkin method of moments in the Fourier transform domain. The validity of the solution is tested by comparison of computed results with experimental data. The theoretical treatment proves to be applicable to the most common feeding arrangements, namely, the direct edge-feed and proximity coupling excitation. In the latter case, two-layer substrates having distinct dielectric constants are studied. The purpose of the study is to deduce, for a given overall substrate thickness, the smallest line-ground plane separation for which a match of the radiator to the feed line is still possible. The advantages of such a configuration are discussed     

Microwave characterization of a microstrip line using a two-port ring resonator with an improved lumped-element model

A two-port ring resonator is used to characterize the microwave properties of a microstrip line printed on Ferro A6-S low-temperature co-fired ceramic. The ring and its coupling gaps are simulated using a simple lumped-element model. The coupling gaps are modeled as capacitors, the values of which are extracted using a commercial two-and-one-half-dimensional electromagnetic simulator. The validity of the lumped-element model is assessed by comparing the simulated and experimental resonant frequencies and, for the first time, the simulated magnitudes of both the reflection and transmission coefficients are also compared with those obtained experimentally. A correction for the frequency pushing due to the capacitive loading of the coupling gaps is also presented. The resulting model is then shown to predict the resonant frequencies to within 0.11% from 5 to 40 GHz. The simulated and experimental reflection magnitudes are within 0.5 dB across the band, whereas the transmission magnitudes are within 3.5 dB up to 22 GHz. Experimental results indicate that the loss of the microstrip ranges from approximately 0.11 to 0.42 dB/cm across the band and that the relative permittivity of the substrate is nearly constant versus frequency with an average value of 6.17.     

Microstrip side-coupled ring bandpass filters with mode coupling control for harmonic suppression

A technique to suppress higher harmonics in side-coupled ring bandpass filters is proposed and demonstrated. The proposed technique basically consists of optimising the ring shape and the excitation stage of the complete filter structure in order to mitigate the excitation of the resonant modes that generate the second-harmonic filter resonances. A harmonic suppression ratio for the second harmonic greater than 25 dB in a flat bandpass filter centred at 2.5 GHz is experimentally demonstrated.     

Analysis of a wide radiating slot in the ground plane of amicrostrip line

An analysis of a wide rectangular radiating slot excited by a microstrip line is described. Coupled integral equations are formulated to find the electric current distribution on the feed line and the electric field in the aperture. The solution is based on the method of moments and using the space domain Sommerfeld-type Green's function. The information about the input impedance or reflection coefficient is extracted from the electric current distribution on the microstrip line utilizing the matrix pencil technique. The theoretical analysis is described and data are presented and compared with other theoretical and experimental results     

Simulations of a ring resonator free-electron laser

A relatively high gain (≈25 to 40%) free-electron laser (FEL) with an optical ring resonator is simulated using the code FELEX. The laser system corresponds to the `burst mode' FEL. The ring consists of paraboloids, grazing incidence hyperboloids, and a grating rhomb. The wiggler is 5 m in length and has an adjustable taper, while the electron beam is produced by an RF linac. The optical elements of the ring together with the FEL interaction in the wiggler are modeled in three spatial dimensions to investigate the system from start-up to saturation. Both single-frequency and finite-pulse simulations are performed     

集成光学陀螺谐振腔结构参量的确定

为了研究集成光学陀螺灵敏度的优化,采用调频光谱原理与多光束干涉方法,对谐振式集成光学陀螺核心敏感器件的谐振特性、决定因素及其它们对陀螺灵敏度的影响进行了研究,得到了与光纤谐振腔情形不同,耦合比与腔长变化对谐振特性影响具有二重性的结果.结果表明,在给定波导传输损耗的条件下,以陀螺灵敏度为判据,集成光学陀螺存在由波导损耗水平决定的最佳谐振腔结构参量.     

Dual-mode stepped-impedance ring resonator for bandpass filterapplications

It is well known that two orthogonal resonant modes exist within a one-wavelength ring resonator. In this paper, we focus on a ring resonator possessing an impedance step as a form of perturbation. A convenient analyzing method for obtaining the resonance characteristics of this resonator structure is presented. Furthermore, generation of attenuation poles obtained by the dual-mode ring resonator is discussed. In addition, a filter design method based on this resonator is explained, followed by experimental results, which prove the validity of the proposed design method     

A generic approach for permittivity measurement of dielectricmaterials using a discontinuity in a rectangular waveguide or amicrostrip line

A generic approach is proposed to accurately measure microwave and millimeter-wave properties of dielectric materials. This novel technique first determines the scattering parameters of a discontinuity containing a material having a wide range of complex dielectric permittivity ϵ that is known a priori (the direct problem). The discontinuity is embedded in a rectangular waveguide or a microstrip line. A unified theory, which is essentially based on a combination of the boundary integral equation technique with a modal expansion approach, is presented to tackle the direct problem. A class of generic diagrams are obtained for interrelating the dielectric permittivity ϵ to its S-parameters, and a simple analytical expression is deduced to solve the inverse problem. The proposed analytical formulation is easy to use and much more rapid than its iterative counterparts. It demonstrates a completely new and efficient strategy for accurate complex dielectric measurements     

Microstrip ring resonator for soil moisture measurements

Development of a successful remote sensing instrument for soil moisture relies on the accurate knowledge of the soil dielectric constant (ϵ_soil) to its moisture content. Two existing methods for measurement of dielectric constant of soil at low and high frequencies are, respectively, the time domain reflectometry and the reflection coefficient measurement using an open-ended coaxial probe. The major shortcoming of these methods is the lack of accurate determination of the imaginary part of E_soil. In this paper, a microstrip ring resonator is proposed for the accurate measurement of soil dielectric constant. In this technique the microstrip ring resonator is placed in contact with soil medium and the real and imaginary parts of E_soil are determined from the changes in the resonant frequency and the quality factor of the resonator, respectively. The solution of the electromagnetic problem is obtained using a hybrid approach based on the method of moments solution of the quasistatic formulation in conjunction with experimental data obtained from reference dielectric samples. Also, a simple inversion algorithm for E_soil=E^'_r-jϵE^"_r based on regression analysis is obtained. It is shown that the wide dynamic range of the measured quantities provides excellent accuracy in the dielectric constant measurement. A prototype microstrip ring resonator at L-band is designed and measurements of soil with different moisture contents are presented and compared with other approaches     

Tests of a grazing-incidence ring resonator free-electron laser

The authors describe operational experience of the first free-electron laser (FEL) using a grazing-incidence ring resonator. The Boeing FEL optical cavity was changed from a simple concentric cavity using two spherical mirrors to a larger grazing-incidence ring resonator. Initial tests showed that poorly positioned ring focus and unreliable pointing alignment resulted in reduced and structured FEL output. Later efforts concentrated on improving the resonator alignment techniques and lowering the single-pass losses. FEL performance and reliability have significantly improved due to better ring alignment. The alignment procedure and recent lasing results are described. The effect the electron beam has on lasing is also discussed. Measurements are presented showing FEL temporal output and wavelength are sensitive to electron beam energy variation     

一种新颖的复合环形谐振腔的理论分析

文章基于环形谐振腔所具有的非线性相位传输特性,提出了一种新型的动态光谱滤波器结构,它将全通环形谐振腔调相器接入平衡马赫-曾德干涉仪,实现复合结构的动态滤波特性.与传统的马赫-曾德干涉仪相比,此复合滤波结构可利用远小于π的相移调整实现输入光信号的开关,因此,在提高开关速度、降低调相器功耗等方面具有重要的应用价值.     

带有环形谐振器的T形光子晶体滤波器

提出了一种带有环形谐振器的T形光子晶体滤波器,利用时域有限差分法研究了滤波器传输特性,分析了光子晶体结构参数对其传输特性影响。结果表明：该结构具有可调性开关波长、传输率高及频带宽的特点,在光子晶体集成制作、光通信器件制作等方面具有潜在的应用价值。     

一种适合于同轴放电气体激光器的多程环形腔

本文提出了一种适用于同轴放电气体激光器的环形腔方案,给出了这种腔的设计和光束特性。     

Design and manufacture of a 1GHz split ring resonator

TheQ value and the resonant frequency for split ring resonator are derived by the method of equivalent circuit. The relationship betweenQ and dimensions of split ring resonator is obtained by taking the resonator as a solenoid. A series of curves for optimum design is plotted. In our experiments, a highQ value of 900 to 1000 in the frequency range of 1 to 1.4 GHz is easily obtained; the resonator has the merits of small dimension, wide frequency range and simplicity in construction.     

Application of a new MPIE formulation to the analysis of adielectric resonator embedded in a multilayered medium coupled to amicrostrip circuit

A new mixed-potential integral-equation (MPIE) formulation is developed for the analysis of electromagnetic problems due to conducting or dielectric objects of arbitrary shape embedded in a planarly stratified medium. In the new MPIE formulation, the dyadic kernel of the vector potential is kept in the simple form originally developed by Sommerfeld. The scalar potential, which is related to the vector potential via the Lorenz gauge, is then represented by a double dot product of a dyadic kernel with a dyadic charge density. An extra line integral term, which is well behaved and nonsingular, will appear when the object penetrates an interface. The numerical implementation of the double dot product is found to be trivial if one takes advantage of the well-established basis functions in which the unknown current density is expressed. The new MPIE formulation is employed in conjunction with the triangular patch model to treat the problem of a dielectric resonator (DR) excited by microstrip circuit. A matched-load simulation procedure has been used to extract the network S-parameters of a DR microstrip circuit. The diameters of the Q circles have been measured to determine the coupling coefficients and the Q factors of the DR excited by a microstrip circuit. The validity of the new MPIE formulation and the numerical procedure have been verified by comparing the obtained S-parameters, with available measurement data     

Accurate closed-form expressions for the electromagnetic parameters of the shielded split ring line

Based on rigorous analysis of finite element method (FEM), moment method (MoM), and curves fitting techniques, a set of closed-form formulas for the characteristic impedance and the primary (L and C) parameters of the shielded split ring line, are presented. The general expressions give a good accuracy for a wide-range of discontinuity angles and are suitable for all shielded split ring lines which have an outer–inner conductors radius ratio between 2 and 10. These expressions can be easily implemented in CAD simulation tools, to design many components as RF resonators, filters, transmission lines, for wireless communication and probes for material characterization. The results of the design of an RF resonator using the shielded split ring line are presented.