Propagation characteristics of magnetostatic waves

The present paper reviews the propagation characteristics of the three magnetostatic wave-types that can exist in a ferrimagnetic film such as the commonly used epitaxial yttrium-iron-garnet (YIG) film, viz., magnetostatic surface waves (MSSWs), magnetostatic forward volume waves (MSFVWs) and magnetostatic backward volume waves (MSBVWs). The pronounced inherent dispersiveness of these waves and methods of controlling or tailoring dispersion are discussed. Other propagation characteristics such as diffraction and propagation loss and the envelope distortion of acw pulse in propagating through such a dispersive medium are briefly described.     

Propagation characteristics of magnetoelastic surface wave

The propagation characteristics of a magnetoelastic surface wave in ferrites are described using numerical calculations pertinent to gallium-y.i.g.     

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     

Tunable magnetostatic surface wave demultiplexing filter/switch

A tunable frequency demultiplexing filter/switch has been realised on a magnetostatic surface wave delay line by employing both parallel-bar structure and meander line structure as output transducers together with a wideband single-line input transducer. Switching from one output terminal to the other has been obtained by changing the applied magnetic field from 57 Oe to 78 Oe at 1.1 GHz.     

Propagation of magnetostatic surface waves in multiple magnetic layer structures

The dispersion of magnetostatic surface waves (m.s.s.w.s) propagating in structures consisting of up to four magnetic layers has been calculated. The m.s.s.w. dispersion and velocity can be controlled by selecting layer thickness and magnetisation. Experiments performed with layered y.i.g. structures were in agreement with the analysis.     

The mechanism of transformation of a magnetostatic surface wave into an electromagnetic wave

On the basis of the analysis of the variations in the characteristics of a magnetostatic surface wave propagating in an inhomogeneously magnetized plane ferrite/dielectric structure, the physical mechanism of transformation of this wave into an electromagnetic wave has been studied and the radiation patterns have been calculated at various parameters of the structure for the case of a slowly changing surface impedance. The earlier experimental results are analyzed on the basis of these theoretical studies.     

Bragg resonances of magnetostatic surface waves in a ferrite-magnonic-crystal-dielectric-metal structure

Formation of Bragg resonances of surface spin waves (SSWs) propagating in a magnonic-crystaldielectric-metal (MC-D-M) structure is studied. It is shown that, in an MC-D-M structure with a finite dielectric interlayer of thickness t, Bragg resonances of the SSWs with the wavenumbers k < 1/t can be destroyed whereas the resonances of the SSWs with k > 1/t persist and lead to formation of rejection bands in the wave spectrum.     

Dispersion characteristics of magnetostatic surface waves in a two-layer ferromagnetic film

The dispersion characteristics (dispersion and isofrequency curves and dispersion surfaces) of magnetostatic surface waves propagating in an arbitrary direction in a two-layer ferromagnetic film are investigated. The shapes of these curves and surfaces are studied at different ratios between the saturation magnetizations of the ferromagnetic layers, and the conditions for existence of external waves (always forward) and internal waves (forward and backward or only forward) are determined.     

System applications of magnetostatic wave devices

A need for microwave signal processing components ranging from simple delay lines to broadband, complex analog non-recursive transversal filters has led to the exploration of several solid-state technologies. Bulk acoustic delay lines lack spatial signal tapping and have high insertion loss. Electromagnetic delay lines have high insertion loss, limited signal processing capabilities, and are bulky. Surface acoustic wave (SAW) devices offer excellent signal processing capabilities at VHF/UHF but suffer from excessive loss at microwave frequencies and the requirement for transducers of sub-micron linewidths. However, a signal processing technology based on magnetostatic waves (MSW) propagating on epitaxial yttrium iron garnet (YIG) is emerging to fill microwave signal processing requirements. This paper summarizes the characteristics and status of magnetostatic waves and devices based on MSW, and initial experimental studies of the application of MSW devices to systems, and presents a survey of other potential areas of MSW device applications.     

Multipassband electronically tunable magnetostatic wave filter

A new design for a multipassband microwave filter based on magnetostatic waves propagating in a multilayer planar ferrite structure is described. The experimentally realised filter had two passbands of 10 MHz bandwidth and 5-6 dB insertion loss separated by 400 MHz, and was tuned with an external magnetic field over the 2.5-4 GHz range.<>     

Propagation of magnetostatic surface waves in a ferrite plate magnetized by a spatially periodic transverse field

Propagation of magnetostatic surface waves (MSSWs) in a ferrite plate magnetized by a spatially periodic transverse field has been considered. The parameters of MSSW propagation have been calculated by the Hamilton-Auld method. It is shown that only noncollinear MSSWs, whose wave-beam trajectories as well as wave numbers and angles, which determine the directions of the vectors of the phase and group velocities, are described by functions that are periodic in the direction of the wave propagation, can exist in this field. The period of these functions is determined by the period of the spatially periodic field. The frequency range of existence of the collinear waves is narrower than that of the waves in a uniformly magnetized plate. The characteristics of wave propagation in a nonuniform spatially periodic field are compared to the characteristics of wave propagation in nonuniform fields of known types.     

Nonlinear behaviour of magnetostatic surface waves

The higher-power behaviour of magnetostatic surface waves propagating at right angles to a magnetic bias field in a y.i.g. single-crystal slab has been investigated experimentally. The conditions for coincidence of the surface modes and the high-power subsidiary absorption are discussed.     

Dispersion control in magnetostatic wave delay lines

A major impediment to the realization of practical magnetostatic wave (MSW) devices is the inherent non-linear delay versus frequency characteristics of MSW delay lines. Most device applications require either nondispersive (delay vs. frequency slope=0) or linearly dispersive (delay vs. frequency slope = constant) characteristics. There are four basic approaches to the elimination and/or linearization of MSW dispersion: (1) modification of the magnetic film properties as a function of film thickness, (2) modification of the ground plane geometry, (3) modification of the bias field uniformity, and (4) perturbation of the propagation path surface with metal electrode reflective arrays. In principle all four approaches can yield either linearly dispersive or nondispersive characteristics with a suitable choice of bias field orientation and critical design parameters. These dispersion control techniques are reviewed, and data from recent experiments demonstrating the strengths and weaknesses of the various approaches are discussed. To date the most extensive experimental work has been done with the multiple layer (magnetic properties varied as a function of film thickness) and ground-plane spacing techniques. At present the ground-plane spacing technique produces results acceptable for some systems applications, while the multiple-layer approach is still under development.Research supported in part by Air Force Office of Scientific Research (AFSC), United States Air Force, under contract Number F49620-82-C-0081 and Rome Air Development Center (RADC), United States Air Force, under Contract Number F19628-82-C-0098. The United States Government is authorized to-reproduce and distribute reprints for governmental purposes notwithstanding any copyright notation herein.     

On-board frequency demultiplexing by magnetostatic wave technologies

Possible magnetostatic wave (MSW) implementations of variable bandwidth variable centre frequency (VBVCF) on-board demultiplexers are presented. Hybrid technologies using magnetic thin films in conjunction with gallium arsenide (GaAs) monolithic microwave integrated circuits (MMIC) are introduced. New areas of research to advance the state of the art in this field are identified.     

Electronically tunable nondispersive magnetostatic wave delay line

An electronically tunable, nondispersive magnetostatic wave delay line consisting of cascaded magnetostatic backward volume waves and magnetostatic surface waves delay lines has been designed and realised. The distinguishing feature of the device is a wide continuously tunable time delay range of ±30% with the central value of 58 ns. An obtained bandwidth for constant time delay is ~300 MHz at a 3.15 GHz centre frequency. A deviation from constant delay is <±5%     

Phase noise characterisation of planar magnetostatic wave oscillators

The phase noise performances of a planar configuration of a magnetostatic wave oscillator have been investigated. The behaviour of the output signal has been studied in terms of the single sideband power spectral density. Values as low as -100 dBc at 100 kHz of offset from the carrier frequency have been measured in the whole range of tunability, by using two different resonators.     

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     

Broadband terminations for magnetostatic surface waves

The properties of magnetostatic surface wave (MSSW) devices are disturbed by the finite length of the YIG film. Such disturbances, causing interference phenomena of MSSW reflected from both film ends, can be measured in the time domain by multiple reflections or in the frequency domain by a passband ripple. These reflections can be eliminated by adequately loading the film ends with semiconductive samples.     

Diffraction of surface magnetostatic waves by surface cavities on ferromagnetic film

The diffraction problem of the scattering of surface magnetostatic waves by shallow rectangular and circular cavities on the surface of a ferromagnetic film that is tangentially magnetized with respect to the surface is numerically analyzed in the magnetostatic approximation.     

Propagation of surface polaritons and total electromagnetic wave transmission through layered structures

Dispersion relations of coupled magnon-plasmon surface electromagnetic waves propagating along the interface between antiferrodielectric and uniaxial semiconductor are considered. Total transmission of infrared wave trough such layered structure induced by resonant excitation of the surface wave is investigated.