Theory and experimental results are presented to show the possibility of using a resonant post technique for characterizing dielectric and magnetic materials at microwave frequencies. Results of the temperature dependence of the relative dielectric constant of nonmagnetic materials with /spl epsilon//sub r/, varying from 4 to 60 are presented and also loss tangent measurements at room temperature. The complex permittivity and permeability of a number of garnet materials has also been measured with 4/spl pi//spl gamma/M/sub s/ / /spl omega/ varying from 0.25 to 0.8. The measured real part of the permeability is in good agreement with the theoretical predictions of Schlomann and the imaginary part of the permeability agrees with measurements by Green et al. on similar materials.

Analysis and Evaluation of a Method of Measuring the Complex Permittivity and Permeability Microwave Insulators

Improvements both in accuracy and speed are described for the technique of measuring the microwave dielectric properties of low-loss materials by using a dielectric rod resonator short-circuited at both ends by two parallel conducting plates. A technique for measuring the effective surface resistance R/sub s/ of the conducting plates is proposed to allow the accurate measurement of the loss tangent tan delta. By means of the first-order approximation, the expressions are analytically derived for estimating the errors of the measured values of relative permittivity epsilon/sub r/, tan delta, and R/sub r/, for measuring the temperature coefficient of epsilon/sub r/, and for determining the required size of the conducting plates. Computer-aided measurements are realized by using these expressions. It is shown that the temperature dependence of R/sub s/, should be considered in the tan delta measurement. The copper plates used in this experiment have the relative conductivity of 91.0+-2.7 percent at 20°C, estimated from the measured R/sub s/ value. For a 99.9-percent alumina ceramic rod sample, the results measured at 7.69 GHz and 25°C show that epsilon/sub r/,= 9.687+-0.003 and tan delta = (1.6+-0.2)x 10/sup -5/. The temperature coefficients measured between 25 and 100°C are 112x10/sup -6//°C for epsilon/sub r/, and 23x10/sup -4//°C for tan delta.

Microwave Measurement of Dielectric Properties of Low-Loss Materials by the Dielectric Rod Resonator Method

The dielectric properties at microwave frequencies of Ba(Zn1/3Ta2/3)O3 ceramics prepared by sintering were investigated. These ceramics had lower density but higher loss quality than ceramics hot-pressed at 1400°C. Loss quality was greatly improved by prolonged sintering. The Q of the ceramics measured by the dielectric resonator method was 14 000 at 12 GHz. The ceramics were investigated by X-ray diffraction analysis. It was found that Q improvement corresponds with increased Zn and Ta ordered structures in the ceramics.

Ba(Zn1/3Ta2/3)O3 Ceramics with Low Dielectric Loss at Microwave Frequencies

The microwave characteristics of two dielectric resonator materials were investigated. This research included (Zr, Sn)TiO4, a material having the characteristics of a dielectric constant K= 38, Q= 7000 at 7 GHz, and temperature coefficient of resonant frequency τf, = 0 ppm/°C. The investigation determined the relations between the dielectric loss and micro-structures of this ceramic. Analysis by X-ray microanalyzer made it clear that the addition of Fe2O3 increased the dielectric loss of this ceramic because the Fe ions diffused into the grain. The other material investigated was BaO-PbO-Nd2O3-TiO2, a ceramic having a dielectric constant of K= 88, Q= 5000 at 1 GHz, and τf= 0 ppm/°C. As this ceramic has a very high dielectric constant, it is useful for applications at frequencies <1 GHz.

Microwave Characteristics of (Zr, Sn)TiO4 and BaO‐PbO‐Nd2O3‐TiO2 Dielectric Resonators

In addition to the constant demand of low-loss dielectric materials for wireless telecommunication, the recent progress in the Internet of Things (IoT), the Tactile Internet (fifth generation wireless systems), the Industrial Internet, satellite broadcasting and intelligent transport systems (ITS) has put more pressure on their development with modern component fabrication techniques Oxide ceramics are critical for these applications, and a full understanding of their crystal chemistry is fundamental for future development Properties of microwave ceramics depend on several parameters including their composition, the purity of starting materials, processing conditions and their ultimate densification/porosity In this review the data for all reported low-loss microwave dielectric ceramic materials are collected and tabulated The table of these materials gives the relative permittivity, quality factor, temperature variation of the resonant frequency, crystal structure, sintering temperature, measurement 

Low-loss dielectric ceramic materials and their properties

A novel technique for the measurement of dielectric and magnetic properties of a homogeneous isotropic medium in the range of approximately 3 to 100 kmc is described. An accuracy of /l.chemc/ 1 per cent is possible in the determination of permittivity or permeability in those cases where the loss tangent is sulliciently small. The measuring structure is a resonator made up of a right circular cyndrical dielectric rod placed between two parallel conducting plates. For measurement of permittivity two or more resonant TE/sub onl/ mode frequencies are determined whereas for the measurement of permeability two or more resonant TM/sub onl/ mode frequencies are determined. The dielectric or magnetic properties are computed from the resonance frequencies, structure dimensions, and unloaded Q. Since the loss tangent is inversely proportional to the unloaded Q of the structure, the precision to which Q is measured determines the accuracy of the loss tangent.

A Dielectric Resonator Method of Measuring Inductive Capacities in the Millimeter Range

Intense superradiant laser action in the far infrared (FIR) has been observed in several gases optically pumped with a CO/sub 2/ transversely excited atmospheric-pressure (TEA) laser. A maximum FIR power of 100 kW was observed from CH/sub 3/F at 496 mu m. Characteristics of the system and possibilities of scaling to higher powers are also discussed.

High Power Optically Pumped Far Infrared Lasers

Intense superradiant emission has been observed from methyl fluoride excited by 0.6‐MW pulses from a high‐pressure CO2 laser. Pulses of ∼ 1 kW with a duration of ∼ 150 nsec have been obtained from a 5‐m‐long 40‐mm‐diam cell containing 0.7 Torr of methyl fluoride. This output represents an efficiency of converting infrared photons to far‐infrared photons of ∼ 5%. Evidence for partial waveguiding in the cell and for phase‐coherent amplification are presented.

Intense superradiant emission at 496 μm from optically pumped methyl fluoride

The mixing of various pairs of CO/sub 2/ laser lines in a nonlinear material can produce thousands of step-tunable far infrared (FIR) signals in the range 70-mu m-7-mm wavelength with frequency spacings of less than 0.1 cm/sup -1/. The major problem in realizing these coherent signals is achieving phase matching in a suitable nonlinear material. In this paper, the interest is in generating tunable signals at the milliwatt level in a planar-dielectric integrated-optics waveguide configuration. Phase rnatching can be achieved with cubic materials (i.e., GaAs) by adding the waveguide dispersion to the bulk dispersion. Work on the analysis of the waveguide mixing system and its correlation with experimental data are described for a planar GaAs dielectric waveguide in the 100-1000-mu m wavelength range.

Step-Tunable Far Infrared Radiation by Phase Matched Mixing in Planar-Dielectric Waveguides

The aim of this survey is to discuss the basic problems encountered in the general areas of generation, transmission, and detection of millimeter waves. Representative examples of work in these three areas since 1959 are reviewed with respect to the methods and techniques employed to circumvent present limitations and extend the frontier into the submillimeter range. Subject classifications include classical and quantum electronics, harmonic generation optical frequency pumping and mixing, waveguide and optical transmission systems, resonators, and detectors. At the end of each section, a few critical evaluation remarks are made on the work in progress and the prospects of success in the near future. A fairly comprehensive list of some 157 references dating from 1959 is listed by year and subject title. While substantial progress has been made, especially in technology, in the last few years, the submillimeter wave problem appears as formidable as ever and no breakthrough idea has yet been recognized.

P.D. Coleman

Papers

A Dielectric Resonator Method of Measuring Inductive Capacities in the Millimeter Range

High Power Optically Pumped Far Infrared Lasers

Intense superradiant emission at 496 μm from optically pumped methyl fluoride

Step-Tunable Far Infrared Radiation by Phase Matched Mixing in Planar-Dielectric Waveguides

State of the Art: Background and Recent Developments--Millimeter and Submillimeter Waves