Magnetostatic wave (MSW) technology has been under investigation for more than a decade. Using ferrimagnetic films such as liquid-phase epitaxial (LPE) yttrium iron garnet (YIG) films, MSW devices and subsystems offer instantaneous bandwidths of up to 1 GHz at operating frequencies in the microwave bands (0.5-26.5 GHz). Because MSWs travel with velocities two-to-four orders of magnitude slower than electromagnetic waves, compact devices can be built using hybrid and monolithic microwave integrated circuit (MMIC) techniques. These devices include delay lines, dispersive delay lines, filters, resonators, and directional couplers. Subsystems using these devices, such as electronically tunable delay lines channelized filter banks, delay-line discriminators, oscillators, and frequency multipliers can be used for applications in signal identification, control and processing directly at microwave frequencies. An overview of the MSW technology is presented and an assessment of the various devices and subsystems that can be built using thin and thick LPE-YIG films is provided. >

Magnetostatic wave technology: a review

Spectrum and linear excitation of spin waves in ferromagnetic films

The linear excitation of spin waves by an inhomogeneous microwave magnetic field (the field of a microwave antenna) is investigated. The investigation is based on the spin-wave normal-mode theory which takes into account the specific features of spin waves (dipole and exchange interactions and surface-spin-pinning conditions) travelling in perpendicularly and in tangentially magnetised thin ferromagnetic films. Explicit dispersion equations and expressions for the spin-wave magnetisation generated are derived. These expressions enable one to calculate the characteristics of spin waves excited by the microwave field of an antenna.

Excitation of propagating spin waves in ferromagnetic films

Electronic warfare and telecom systems demands for increased bandwidths and operating frequencies for analog signal processing could be satisfied in the near future by the emergence of a novel technology based on magnetostatic waves (MSW) propagating in single crystal magnetic films such as the epitaxial yttrium iron garnet (YIG). Offering bandwidths up to 2 GHz at operating frequencies ranging from 0.5 to 20 GHz, MSW is, at the present time, the only available technology for analog signal processing directly at microwave frequencies. This paper will present an overview of the various techniques involved in the MSW area and of the possible device applications. In a first section, the growth of epitaxial YIG film, the propagation characteristics, the transduction, terminations, and temperature stability are briefly reviewed. Next, periodic structures obtained by ion beam milling, metal deposit, or ion implantation are considered. The following section is devoted to dispersive and nondispersive delay lines....

State of the art in design and technology of MSW devices (invited)

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 Surface-Wave Transducers

The insertion loss for multibar magnetostatic-surface-wave (m.s.s.w.) transducers has been calculated from a ‘small’-loss microstrip-transmission-line model. Experimental results for 2-bar and 8-bar parallel-strip and 4-bar π transducers are in excellent agreement with theoretical predictions. The 8-bar parallel-strip-transducer delay line gives a major bandpass response at 3.1 GHz, corresponding to an m.s.s.w. wavelength of 300 μm. The insertion loss is 11 dB, the 10 dB bandwidth is 70 MHz and adjacent sidelobes are 16 dB down.

Bandpass filtering with multibar magnetostatic-surfacewave microstrip transducers

This paper reports results of theoretical and experimental studies of microwave delay line filters based on magnetostatic wave (MSW) propagation in epitaxial yttrium iron garnet (YIG) with multielement transducer pairs for wave launching and receiving. Filter transmission and input impedance characteristics for both magnetostatic surface wave (MSSW) and magnetostatic forward volume wave (MSFVW) devices have been calculated and measured experimentally. A planar, multilayer metal‐dielectric‐YIG geometry, permitting consideration of decoupling due to spacing between the transducers and YIG surface, is used to model the transducer. A ’’low’’ loss microstrip transmission line model is used to derive an equivalent transducer circuit. For assumed noninteraction of transducer element currents, the Poynting vector is used to determine the radiation resistance and the radiation reactance is derived from the Hilbert transform of this resistance. Experimental swept frequency measurements of insertion loss and input i...

H. J. Wu

Papers

Bandpass filtering with multibar magnetostatic-surfacewave microstrip transducers

Bandpass filtering and input impedance characterization for driven multielement transducer pair‐delay line magnetostatic wave devices