This paper is concerned with dielectric disks used as resonators in microwave bandpass filters. For many years it has been known that modes of resonance occur in isolated dielectric bodies having air boundaries, and that very compact high-Q resonators can be achieved when /spl epsiv/ /sub r/, is high and tan /spl delta/ is low. High-purity TiO/sub 2/ ceramic material, for example, has an /spl epsiv/ /sub r/ about 100, tan /spl delta/ about 0.0001, and Q/sub u/ about 10 000. Practical applications of dielectric resonators have previously been limited by insufficient design information. Formulas are derived for the coupling coefficient between adjacent dielectric-disk resonators within a metal waveguide below cutoff. This metal enclosure is necessary for shielding and to prevent radiation loss. Comparisons between theoretical and experimental coupling coefficient values show very good agreement in each of the three bandpass configurations treated in this paper. Techniques of loop and probe coupling to the end resonators of a multiresonator bandpass filter are discussed and methods of supporting the resonators are suggested. The conclusion is made that microwave dielectric resonators offer important size reductions compared to conventional resonators of similar high Q, but that the center-frequency change of the dielectric resonators as a function of temperature is excessive for many applications. Temperature stabilization is one solution, but preferably a material should be developed having electrical characteristics similar to TiO/sub 2/ ceramic, but with at least an order of magnitude improvement in temperature sensitivity.

Microwave Bandpass Filters Containing High-Q Dielectric Resonators

Dielectric resonators are being used in microwave filters and oscillators now that high-dielectric-constant, high-Q, temperature-stable ceramics have been developed. This paper reviews dielectric resonators with emphasis on applications, contains tutorial material, deseribes new 2-, 4-, and 6GHz bandpass filters, and presents several examples of oscillator applications. A complete blbliography to English language publications on dielectric resonators is included.

Application of Dielectric Resonators in Microwave Components

Magnetic excitations in solids

The resonant frequencies for the fundamental modes in circular cylindrical and rectangular parallelopiped high dielectric resonators have been calculated by computer for a range of values of physical dimensions and relative dielectric constant. The frequency range extends from zero to 50 kMc/s, the relative dielectric constant from 50 to 1800, and physical dimensions from zero to 500 roils. Results are presented in graphical form with frequency plotted vs. resonator length for parametric values of relative dielectric constant and cross-sectional dimensions. A brief review of earlier work with high dielectric resonators is included. Expressions for the resonant frequency and fundamental mode field configurations are given.

Design of Microwave Dielectric Resonators

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)

This is a review of two electrical equivalent circuits for multi-element magnetostatic wave transducers. The two circuit models are identified as a transmission line and a two terminal model. Both models have been extended to all three principal MSW modes of propagation to the point where computer programs have been written to plot phase and amplitude response as measured by commercial network analyzers. A review is provided of the basic assumptions, similarities and differences, advantages and disadvantages, and limitations of the two models. The useful range of them covers many cases of practical interest in the one to twelve Ghz frequency range.

Theory of MSW transducers

A second ``corner'' has been observed on the ``butterfly curve'' of the parallel pumping experiment on YIG (yttrium iron garnet) at x‐band frequency. The extra corner occurs in all crystallographic directions in a (110) plane except the [100] and [111]. The separation between the two corners closely equals the anisotropy‐produced azimuthal angle splitting of the top of the spin‐wave band. This splitting occurs in cubic YIG in all directions except the [100] and [111]. The shape of the butterfly curve in the region between the corners is partially explained by the variation in spin‐wave ellipticity with azimuthal angle. A variation in spin‐wave linewidth for k→0 with azimuthal angle may be responsible for the remaining discrepancy.

Spin‐Wave Anisotropy Effects in Parallel Pumping in YIG

Frequency stability in dielectric resonators

The frequencies of magnetostatic wave (MSW) oscillators employing three principal modes of propagation, surface (MSSW), forward (MSFVW), and backward (MSBVW) volume waves, have been investigated. Previous (MSW) oscillator papers dealt with MSSW. Oscillators were fabricated using LPE‐YIG MSW delay lines in a feedback loop of a 2–4 GHz amplifier. Wide and narrow band transducers were employed. Oscillator frequency as a function of biasing field is in agreement with a theoretical analysis. The analysis predicts frequency in terms of material parameters, biasing field, and transducer geometry. With wide band transducers a comb of frequencies is generated. Narrow band transducers for MSSW and MSFVW select a single mode; and MSBVW selects two modes. Spurious modes, attributed to instrumentation, are more than 20 dB below the main response, and bandwidths are less than 0.005 percent. No other spurious modes are observed. MSW oscillators produce clean electronically tunable signals and appear attractive in frequency agile systems.

J. C. Sethares

Papers

Theory of MSW transducers

Spin‐Wave Anisotropy Effects in Parallel Pumping in YIG

Frequency stability in dielectric resonators

Magnetostatic wave oscillator frequencies

Visual Observation of High Dielectric Resonator Modes