Quasi-TEM model of magnetostatic-surface wave excitation in microstrip lines

The per unit length capacitance and inductance of a YIG-loaded microstrip line are computed in the frame of a quasi-transverse electromagnetic approach. The transmission line parameters, i.e., the complex propagation constant and the complex characteristic impedance are computed from them and the insertion loss of a finite-length YIG-loaded microstrip line is obtained using the simple transmission line model. In particular, it is shown that this model is suitable even for the magnetostatic regime.     

Insertion loss of magnetostatic surface wave delay lines

An experimental and theoretical study is presented of the insertion loss of magnetostatic surface wave delay lines. The magnetostatic surface waves are excited by single microstrip transducer and propagate in a delay line consisting of conductor-dielectric-YIG-GGG. The effect of nonuniformity in microstrip current and the effect of finite width of YIG film are included in the theory. An undesired notch seen in the insertion-loss response of the surface-wave delay line in the low-frequency region of the band is explained by the present theory, which includes the finite width of the YIG film     

Insertion loss of electronically variable magnetostatic wave delaylines

An investigation is presented of insertion loss and constant variable delays in electronically variable magnetostatic-volume-wave delay lines. The delay line has a conductor-dielectric-YIG-dielectric-conductor structure. Variable delays up to 300 MHz bandwidth have been obtained in a single volume-wave delay line by adjusting the direction and magnitude of the biasing DC magnetic field in a plane containing the normal to the YIG film and the direction of wave propagation. Insertion loss as a function of frequency has been obtained for different biasing field angles and also for the angles corresponding to variable constant delays. Good agreement between theoretically obtained insertion loss and experimental results is found. Electronically variable magnetostatic-wave delay lines have promising applications in broadband phased-array antennas at 1-20 GHz     

Insertion loss concepts

The term "insertion loss" has become such a popular one and is applied to so many different concepts that it is becoming unsuitable for precise use. Certain other concepts connected with insertion loss such as attenuation and mismatch loss, are in need of clarification. A logical set of definitions and equations are presented as a suggested approach to more precise terminology. The effect of complex characteristic impedance on these equations is given in an Appendix. Specific suggestions are given for changes in the usage of terms, which if acceptable and adopted would improve the situation.     

Insertion loss of mismatched filters

The design of power line filters is difficult because the actual impedances of the equipment to be suppressed and of the power lines are often unknown. By means of simple geometric considerations it is easy to calculate the maximum and minimum insertion losses which give a more realistic characterization of power line filter performances.     

A new development of an equivalent circuit model for magnetostaticforward volume wave transducers

A three-port equivalent circuit model of microstrip transducers used for the generation and detection of magnetostatic forward volume waves (MSFVW) is derived from fundamental physical considerations. In this circuit model, each microstrip MSFVW transducer is modeled as a three-port circuit incorporating a frequency-dependent series reactance, a frequency-dependent lossless transformer, and a lossy transmission line. Circuit parameters are determined in closed form by the use of solutions of pertinent boundary-value problems. The effects of parasitics, for example, capacities of bonding pads, are easily taken into account. Some typical transducer configurations are analyzed numerically. The three-port model developed is in excellent agreement with experiments. The model can be applied directly to nonuniform arrays of microstrips weighted by varying the separation between strip centers and the widths of successive strips or reversing the current direction of some groups of strips     

GHz-range surface acoustic wave interdigital transducers and applications

GHz-range SAW interdigital transducers, unidirectional transducers and SAW filters are described. Also, new fabrication technologies which can achieve higher operating frequencies are presented.     

Insertion loss and saturation effects in the diode correlator

The insertion loss and electronic saturation effects observed in the series-configuration diode correlator are described in terms of a simple 1st-order theory. The results of this theory are favourably compared with experiments for an 8-tap diode correlator operating in the 30?60 MHz range.     

Surface acoustic wave resonator filters based on dispersive transducers

The possibility of using interdigital transducers (IDTs) and reflecting lattices with electrode period modulation (dispersion) in resonator filters with longitudinal acoustic coupling on surface acoustic waves is considered. The experimental investigation of test structures with different directivities of the transducer dispersion shows that dispersive IDTs provide for unidirectional excitation. A model developed on the basis of the equivalent-circuit method makes it possible to calculate the characteristics of filters of the class under consideration. It is found that the use of dispersive IDTs and reflecting lattices makes it possible to reduce the insertion losses of devices, to extend their passbands, and to improve their selectivity. A set of filters is designed on the basis of lithium tantalate and lithium niobate acoustic ducts with insertion loss ranging from 1.5 to 3.0 dB and relative passbands ranging from 1 to 8%.     

阵列波导光栅插入损耗的降低

阵列波导光栅（AWG Arrayed Waveguide Grating）是实现多通道密集波分复用（DWDM Dense Wavelength Division Multiplexing)光网络的理想器件,插入损耗是它的一个重要性能指标。本文介绍了多种减小AWG插入损耗的方法,并在此基础上,分析了如何使用楔形波导结构来降低模式失配所导致的耦合损耗。这种方法可以在不增加器件制作难度的同时大大降低AWG的插入损耗,并且适用于各种材料和结构的AWG器件设计。     

体波声光器件中换能器特征频率的测定

在体波声光器件换能器设计中,往往把它的厚度共振频率f_o作为工作频率。本文通过对换能器的几个特征频率的分析与测定,指出工作频率应选取在它的机械串联共振频率f_3上,并提出了从史密斯圆图上的换能器阻抗与频率的关系曲线上找出f_3的方法。     

Radio wave loss deviation and shadow loss at 900 MHz

Radio wave propagation between base and mobile stations is normally described as being Rayleigh distributed due to multipath radio wave combining. When the number of radio wave paths are limited the variation in received signal amplitude frequently follows a more general case given by a Weibull distribution. A significant portion of the Weibull distribution is defined as the transmission loss deviation. Other definitions have been included with the object of standardizing methods of measuring and reporting propagation data. Data will be presented showing loss deviation between 3 and 30 dB. Shadow loss over hills and around buildings are usually assumed to be knife-edge or rounded knife-edge. Shadow loss based on these assumptions is generally found to be less than the true measured value. Data will be presented comparing calculated shadow loss with measured value.     

Pyroelectric imaging of defects in bulk acoustic wave lithium niobate transducers

Initial results on a method for testing piezoelectric transducers made of a polar material are presented. The method consists of measuring the voltage induced across the transducer electrodes by an intensity-modulated laser beam scanning the surface. Applied to a bulk acoustic wave LiNbO3 transducer, this technique has revealed domains with Z-axis reversed.     

声传播损失试验分析与仿真

声传播损失是水声环境调查的主要内容之一,也是声场预报的重要参数之一。文章利用时频分析方法和能量计算,对声传播数据进行了处理,分析了某海域海洋声学环境特性以及声传播损失的空间分布,并与抛物方程（RAM）模型仿真结果进行了对比分析。结果表明,试验数据和仿真吻合良好,验证了模型的适用性以及声场预报的可行性。     

Plane wave reflection from microstrip-patch arrays--Theory and experiment

Numerical solution of plane wave reflection from an infinite, planar rectangular microstrip-patch array on a grounded dielectric substrate is presented and compared to phased array simulator measurements with a good correlation. In the theory, particular attention is paid to the edge condition and to the convergence of the matrix elements which was accelerated by the Poisson summation technique, as well as to the rate of convergence of the overall solution. The agreement of the values of the resonant frequencies, the associatedQvalues, and their parametric dependence on geometry and frequency, establish confidence in the application of the method used, to prediction of performance of probe-excited microstrip-patch phased arrays.     

Insertion loss function synthesis of maximally flat parallel-coupled line bandpass filters

Insertion loss (IL) functions are derived for synthesis of microstrip parallel-coupled line bandpass filters with maximally flat responses. The derivation is performed by successively multiplying the ABCD matrices of all coupled stages. Simultaneous equations for determining linewidth and line spacing of the coupled stages are established by total Q (Q/sub T/) of the filter specification and comparing the IL function with the canonical form. The results are provided for filters of order N/spl les/6. Two filters with fractional bandwidths /spl Delta/=30% are synthesized and demonstrated by simulation using a full-wave software package. In addition, two filters with /spl Delta/=40% and 50% are fabricated. Tapped line inputs are employed to these two circuits since some linewidths or gaps are beyond the fabrication resolution. The measured results show very good agreement with the theoretical responses.     

Insertion loss due to a spherical shell in low frequency zone

Electromagnetic scattering due to a spherical conductor in presence of a slightly conducting dielectric cover has been studied. Numerical results have been presented for a three-layer model, excited by a uniform time harmonic magnetic field, where the intermediate layer accounts for the spacing between the core and the shield. Scattering coefficients for the covered and uncovered situations are compared in terms of an insertion loss parameter. The resulting curves provide information about the interesting frequency bands of supertransmission of energy between the source and the core-conductor. The results may find application in electromagnetic probing of some terrestrial and lunar situations.     

Equivalent-circuit model for interdigital transducers with varying electrode widths

A recently developed bulk-wave equivalent-circuit model that allows the electric fields in a transducer to be arbitrary functions of distance along the direction of acoustic propagation has been adapted for surface-acoustic-wave transducers. Experimental results are presented that confirm the validity of this model.     

Diffraction loss of the signal in microwave acoustic delay lines with multielement piezoelectric transducers

On the basis of the Green??s function, a method for calculation of diffraction fields in multielement piezoelectric transducers used in anisotropic crystal acoustic ducts is developed. The results of the numerical analysis of diffraction fields, which are created by multielement piezoelectric transducers on the face of the acoustic duct, are given together with the results of calculation of the diffraction loss of the main signal and the triple and quintuple transit echoes in an acoustic delay line of the microwave signal, which operates in the direct mode. The dependences of the diffraction loss on the angle between the crystallographic axis and the geometrical axis of the acoustic duct are studied.