Magnetostatic wave mixer

A new element, allowing the mixing of signals in the microwave frequency range is described. Excitation of magnetostatic waves (MSW) in the non-stationary medium has been used to modulate the carrier harmonic signal. The proper choice of the working point allows the higher harmonic products of the output frequency spectrum to be suppressed.<>     

Magnetostatic wave convolvers

The present paper reviews recent theoretical results, and reports initial experimental results, on the convolution of contra-propagating magnetostatic forward volume waves (MSFVWs), in the form of cw signals or time-limited cw pulses, in an epitaxial yttrium iron garnet (YIG) film. Computations of the convolver bilinearity factorF _int indicate an efficient convolution process over a wide bandwidth, with values ofF _int that are of the same order as, or better than, the reported experimental results for MSW convolution in a YIG cylindrical or plate geometry. The values of F_int determined experimentally are in excellent agreement with theory. These results are of interest to microwave system developers particularly if bandwidths of 1 GHz or larger can be realized in practice. A limiting feature of magnetostatic wave (MSW) convolvers is that the maximum delay time of a delay line that is realizable without excessive insertion loss is in the order of 0.5s. The advantage of MSW convolvers, of course, lies in their ability to perform signal processing directly at microwave frequencies, and in applications such as electronic warfare the advantageously large bandwidths would mitigate the limitations in delay time.This work was supported in part by a contract from the AIL Division of the Eaton Corporation.     

Magnetostatic bulk wave propagation in a multilayered structure

The effect of finite sample width on the dispersion and delay characteristics of magnetostatic bulk waves in a multilayered structure consisting of a y.i.g. sandwiched between grounded dielectric layers is investigated. It is seen that the cutoff frequency of bulk waves is different for different modes. The effect of finite sample width is significant in the low-wave-number region only when one of the dielectrics is ungrounded.     

Magnetostatic wave resonators and oscillators

The purpose of this paper is to describe the current status of magnetostatic wave tunable resonators operating between 2 and 12GHz and their applications to microwave oscillators, the wave propagating in a pure yttrium-iron-garnet epi-layer. The first section deals with magnetostatic surface wave (MSSW) resonators consisting of a pair of reflective grooved gratings and two microstrip-transducers set between the gratings. Results on insertion loss, off-resonance frequency rejection andQ value are presented. However MSSW cavities suffer several disadvantages such as the small saturation power level at low frequencies and the difficulty to temperature compensate MSSW devices. These problems are overcome with magnetostatic forward volume waves (MSFVW). Then the second section is devoted to MSFVW resonators. A peculiar folded geometry made of five grooved gratings and two microstrip-transducers has been designed to provide a sufficient out-of-band rejection. The experimental characteristics of these resonators are given. In the last section of this paper are reported the features of tunable oscillators implemented with MSSW and MSFVW resonators in a hybrid configuration. Results about tunability, output power,FM phase noise are reported. MSFVW resonator stabilized oscillators are very promising and magnetostatic wave resonators seem a challenge to YIG spheres.This work was supported by the Direction des Recherches, Etudes et Techniques (France).     

Magnetostatic surface wave straight-edge resonators

The performance of the magnetostatic surface wave straight-edge resonator (MSSW-SER) is presented. The resonator uses a rectangular YIG film to propagate MSSWs where the straight edge serves as a reflector. Problems arising from coupling to width mode resonances and their effect on the main resonance are investigated. Through a careful choice of YIG and transducer parameters, the interference effects of the width mode resonances with the main resonance are minimized. As a result, highQ tunable microwave resonators with a tuning range from 2–20 GHz, insertion loss less than 10 dB, and spurious rejection better than 10 dB could be designed and fabricated. This MSSW resonator could be used to construct a tunable low-phase-noise feedback oscillator. However, the tuning range of this MSW feedback oscillator is limited by the phase change of the external amplifier circuit.     

Magnetostatic wave resonators using microstrip disk

The authors propose a magnetostatic wave resonator using yttrium-iron-garnet (YIG) film with a microstrip disk. Assuming a magnetic wall at the edge of the disk, a dispersion relation is derived and solved numerically to obtain the resonant frequency. Resonant mode charts are given for various parameters of resonator. The quality factor is also given as a function of the resonator dimensions. Resonant characteristics are confirmed experimentally using 40-μm- and 13.5-μm-thick YIG films with 5-mm-diameter strip disk at S band     

Magnetostatic wave devices for UHF band applications

Magnetostatic surface wave (MSSW) devices made with pure and gallium-substituted yttrium-iron garnet (Ga:La-YIG) films are described. These devices include nondispersive and dispersive delay lines, band-pass filters, oscillators, and resonators. By controlling the magnitude of the bias magnetic field and the temperature of operation, it is possible to tune these devices over a wide frequency range extending from 0.3 to 4 GHz and from 3 to 18 GHz using Ga:La-YIG and pure YIG films, respectively.These devices could be used in pulse compression radar, microscan receivers, complicated Fourier transform processors, and fundamental oscillator circuits. In this paper, we briefly show results for pure YIG devices tunable in C and X bands and discuss, in detail, the performance of the Ga:La-YIG devices for UHF applications.     

Magnetostatic wave propagation in YIG double layers

Calculations are presented for the magnetostatic surface wave propagation characteristics in single-crystal yttrium-iron-garnet (YIG) double layers with arbitrary direction of magnetization. The induced uniaxial magnetic anisotropy field is assumed to be different in the two layers; hence, the magnetization in one layer is aligned at an angle with respect to the magnetization direction in the other layer. The magnetostatic field interactions between layers depend on the angle between the two magnetization directions and on the separation between the two YIG layers. The wave propagation directions and time delays in each layer can be strongly affected by the use of an applied magnetic field and the magnetostatic coupling between the two layers, as well as by the uniaxial anisotropy energy in each layer     

Magnetostatic correlator of microwave signals with the internal wave front reversal

A new technique of the correlation processing of data based on the nonlinear interaction of signals of backward volume magnetostatic waves in yttrium-iron garnet thin films and a corresponding laboratory mock-up of the correlation receiver operating in the 6 cm wavelength range have been presented in this paper. It was proposed to use additional pumping pulse for obtaining a time-reversed signal pulse. The resultant correlation signal occurred during the nonlinear interaction of the delayed signal wave and the pumping-reversed wave. The specificity of the passage of broadband signals through the resonance system of waveguide of spin waves was taken into account. It has been found out that the resonance properties of the correlator affect the efficiency of the desired signal separation from the noise level. The resultant signal-to-noise ratio for the output signal was enhanced by more than 20 dB.     

Matrix converters: a technology review

The matrix converter is an array of controlled semiconductor switches that connects directly the three-phase source to the three-phase load. This converter has several attractive features that have been investigated in the last two decades. In the last few years, an increase in research work has been observed, bringing this topology closer to the industrial application. This paper presents the state-of-the-art view in the development of this converter, starting with a brief historical review. An important part of the paper is dedicated to a discussion of the most important modulation and control strategies developed recently. Special attention is given to present modern methods developed to solve the commutation problem. Some new arrays of power bidirectional switches integrated in a single module are also presented. Finally, this paper includes some practical issues related to the practical application of this technology, like overvoltage protection, use of filters and ride-through capability     

Interconnects for nanoscale MOSFET technology: a review

In this paper,a review of Cu/low-k,carbon nanotube(CNT),graphene nanoribbon(GNR)and optical based interconnect technologies has been done,Interconnect models,challenges and solutions have also been discussed.Of all the four technologies,CNT interconnects satisfy most of the challenges and they are most suited for nanometer scale technologies,despite some minor drawbacks.It is concluded that beyond 32nm technology,a paradigm shift in the interconnect material is required as Cu/low-k interconnects are approaching fundamental limits.     

Magnetostatic Surface-Wave Transducers

Magnetostatic surface-wave (MSSW) transducer theory is extended and generalized. A Fourier transform relation is established between MSSW field amplitudes and transducer spatial current distribution. Expressions are developed for the radiation resistance of periodic meander and grating transducers, spatial harmonic amplitudes, and radiation resistance for uniform and nonuniform current distribution models. An expression is given for the radiation resistance of apodized transducers. The results enable one to predict transducer frequency response for a specified weighting of transducer element width, Iength and spacing.     

Magnetostatic Waves in a Normally Magnetized Waveguide Structure

In this paper, the propagation of magnetostatic waves (MSWS) in a normally magnetized low-loss ferrite slab (such as a yttrium iron garnet (YIG) slab) placed inside a waveguide is investigated theoretically. This case has never been studied before, and is analyzed here for tbe first time. A dispersion relation for the modes of propagation in terms of an infinite determinant can be obtained. With proper truncation procedures, sample numerical calculations for dispersion relations and group time delay per unit length were obtained and are presented herein. The general formulation in this paper contains all the information provided by the degenerate cases previously published. One special case of interest, i.e., that of a multilayer planar structure, is derived from our general formulation. The derivations of other special cases follow the same procedure.     

Magnetostatic dipolar propagation in a thin ferromagnet slab

A thin ferromagnet slab magnetised in an arbitrary direction parallel to its plane is shown to support a magnetostatic dipolar mode hosc resonant frequency is the same as that of magnetostatic propagation in an infinite medium transverse to the bias field.     

Magnetostatic Wave Propagation in a Finite YIG-Loaded Rectangular Waveguide

The propagation of magnetostatic waves (MSW) in a waveguide partially loaded with a low-loss ferrite slab is investigated theoretically. The most common low-loss ferrite material used for MSW propagation is epitaxial yttrium iron garnet (YIG). A YIG slab is placed inside and along the guide and not in contact with the sidewalls of the wavegnide. The dc magnetic field is assumed to be parallel to the YIG slab and perpendicular to the direction of propagation. Using the integral equation method, the dispersion relation is found to be an infinitely large determinant equal to zero. Proper truncation of this determinant and numerical analysis to find its roots are carried out in this work. It is seen that in order to obtain high values of group time delay, the YIG slab must be narrow and placed at the bottom of the guide. On the other hand, to maximize the device bandwidth, a narrow YIG slab positioned at the top inside surface of the waveguide is preferred. It is also noticed that there exists a tradeoff between the time delay and the device bandwidth and that maximization of one property leads to a poor value in the other. Thus, some design compromises should be made. It is also observed that the frequency range of operation of the device can be adjusted by an external magnetic bias field. This property of tuning the device to operate in any frequency range adds an extra dimension of flexibility to the operation and also to the design of these devices.     

Propagation of Magnetostatic Surface Waves in a Dissipative Ferrite Plate

In the geometry of a plane-parallel in-plane magnetized ferrite plate with dissipation, the dispersion of forward and backward magnetostatic surface waves propagating in an arbitrary direction relative to the field has been investigated. Dispersion curves as functions of the imaginary and real parts of the complex wave number has been constructed. The group velocity of both wave propagation and increase of wave attenuation have been considered. The frequency range of the experimentally observable waves has been estimated at a specified level of sensitivity of the measuring instruments.     

近场拉曼技术发展概述

本文介绍了一种新兴的超分辨光谱技术——近场拉曼散射技术。结合国内外的有关近场拉曼的文献,详细介绍了其实验和理论发展近况,针对近场拉曼的特性,分析了近场拉曼的光谱特点。     

Optically interconnected electronic chips: a tutorial and review ofthe technology

Optoelectronic interconnects between VLSI chips have been identified by the Semiconductor Industry Association (SIA) Roadmap as one of the few solutions to overcoming the communication bandwidth bottleneck between VLSI chips. Large-scale demonstrators based on optical interconnects, when fully operational, can exhibit today the same aggregate bandwidth as that foreseen by the Roadmap for the year 2007. Massive parallelism, low input/output driving energy over large distances, and synchronous processing of hundreds of optical information input channels mean that these prototypes can potentially provide on/off communication rates in the tera-pin-Hz region (i.e., a total capacity of one terabit/s). After discussing the limitations of electrical interconnects this paper reviews the means of integrating optoelectronic components with VLSI chips, suitable types of optoelectronic device and the three main approaches to constructing optical data links: fibre-ribbons, planar waveguides and free-space optics