Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

Two low-permittivity dielectric materials Li2AGeO4 (A = Zn, Mg) were prepared via the solid-state reaction method. X-ray diffraction analysis and Rietveld refinement indicated that both ceramics crystallize in an orthorhombic olivine structure with a space group Pmn21. Dense ceramics with high relative density and homogeneous microstructure were obtained. Li2ZnGeO4 densified at 1200 °C possessed a relative permittivity er = 6.5, a quality factor Q × f = 35,400 GHz, and a temperature coefficient of resonant frequency. Li2MgGeO4 exhibited er = 6.1, Q × f = 28,500 GHz, and τf = –74.7 ppm/°C when sintered at 1220 °C. Additionally, the large negative τf values of Li2AGeO4 (A = Zn, Mg) ceramics were successfully adjusted compensated by forming composite ceramics with CaTiO3 and near-zero τf values of +2.9 ppm/°C and +5.8 ppm/°C were achieved in 0.92Li2ZnGeO4-0.08CaTiO3 and 0.90Li2MgGeO4-0.10CaTiO3, respectively.

Li2AGeO4 (A = Zn, Mg): Two novel low-permittivity microwave dielectric ceramics with olivine structure

Dielectric and magnetic properties of Mg–Ti substituted barium hexaferrite

Synthesis and characterization of high coercivity rare-earth ion doped Sr0.9RE0.1Fe10Al2O19 (RE: Y, La, Ce, Pr, Nd, Sm, and Gd)

The explosive process of 5G communication evokes the urgent demand of miniaturized and integrated dielectric ceramics filter. It is a pressing need to advance the development of dielectric ceramics utilization of emerging technology to design new materials and understand the polarization mechanism. This review provides the summary of the study of microwave dielectric ceramics (MWDCs) sintered higher than 1000 from 2010 up to now, °C with the purpose of taking a broad and historical view of these ceramics and illustrating research directions. To date, researchers endeavor to explain the structure-property relationship of ceramics with multitude of approaches and design a new formula or strategy to obtain excellent microwave dielectric properties. There are variety of factors that impact the permittivity, dielectric loss, and temperature stability of dielectric materials, covering intrinsic and extrinsic factors. Many of these factors are often intertwined, which can complicate new dielectric material discovery and the mechanism investigation. Because of the various ceramics systems, pseudo phase diagram was used to classify the dielectric materials based on the composition. In this review, the ceramics were firstly divided into ternary systems, and then brief description of the experimental probes and complementary theoretical methods that have been used to discern the intrinsic polarization mechanisms and the origin of intrinsic loss was mentioned. Finally, some perspectives on the future outlook for high-temperature MWDCs were offered based on the synthesis method, characterization techniques, and significant theory developments.

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Yih-Chien Chen

Papers

Microwave dielectric properties of 0.95MgTiO3–0.05CaTiO3 for application in dielectric resonator antenna

Elucidating the dielectric properties of Mg2SnO4 ceramics at microwave frequency

Dielectric properties of B2O3-doped La(Mg0.5Sn0.5)O3 ceramics at microwave frequencies

Influence of CuO additions and sintering temperatures on the microwave dielectric properties of CaLa4Ti5O17 ceramics

Investigation of the microwave dielectric properties of Ca1−xMgxLa4Ti5O17 ceramics for application in coplanar patch antenna