Ying-Hsun Lin

Enhance antenna bandwidth by using high permittivity ceramic and FR4 stacked structure

The microstrip patch antennas with high-permittivity ceramic substrate is very effective for antenna size reduction. However, the impedance bandwidth obtained for such a microstrip patch antenna is usually very narrow and the antenna gain is also significantly decreased, and that will severely limit its practical applications. Therefore, the enhancement of the bandwidth and gain of a microstrip patch antenna with high-permittivity substrate is highly desirable. This paper presents a stacked patch antenna structure with enhanced bandwidth and good radiation. Details of the proposed stacked antenna and experimental results are discussed.

A Novel Calcining Method Used to Fabricate the K0.5Na0.5NbO3 Ceramics

K0.5Na0.5NbO3 ceramic prepared by a conventional solid-state reaction process (calcinated at 850°C and sintered) is so fragile that it can not be used to measure dielectric properties. In this paper, we use a two-step calcining method to synthesize KNN composition, with a hydrothermal treatment (200°C for 4 hrs) preceding the calcining process (750°C and 850°C for 2 hrs). Following the hydrothermal treatment and calcining the KNN ceramic was sintered at 1100°C ∼ 1160°C. X-ray diffraction patterns for all KNN ceramics showed a perovskite structure with orthorhombic symmetry. The effects of different calcining and sintering temperatures on the properties of the resulting KNN ceramic, including surface morphology and dielectric characteristic, were recorded and analyzed.