Cheng-Hsing Hsu

Microstrip-Fed Monopole Antenna with a Shorted Parasitic Element for Wideband Application

A microstrip-fed planar monopole antenna consisting of an inverted-L monopole and a square parasitic element extending directly from ground plane to obtain wideband operation covering Bluetooth/ISM, 2.5GHz WiMAX, 3.5GHz WiMAX and 5.2/5.8 GHz WLAN bands is presented. The proposed antenna employs a shorted parasitic element to improve the bandwidth. The return loss of the suggested antenna geometry was calculated by a commercial HFSS 9 simulator and the results are compared with measured return loss, which shows a good agreement between them. Details of the proposed antenna designs and experimental results of the constructed prototypes are presented. Corresponding author: C.-F. Tseng (cftseng@nuu.edu.tw). 116 Tseng, Huang, and Hsu

Microstrip rectangular ring bandpass filter design using high permittivity substrate

A selective bandpass filter with using microstrip rectangular ring resonator is proposed for wireless LAN system such as IEEE 802.11 systems (2.45GHz or 5.25GHz). The miniaturized bandpass filter is implemented using a high permittivity dielectric substrate. The full-wave simulator IE3D is used to design the microstrip rectangular ring filter. The responses of the implemented filter using Sm(Co/sub 1/2 /,Ti/sub 1/2 /)O/sub 3/ (/spl epsiv//sub r/ = 25.5, tan/spl gamma/ = 0.00013) dielectric substrate are designed at dual-band frequencies of 2.45GHz and 5.25GHz. The compacted size and good agreement have been obtained between simulations and implementation results.

Microwave dielectric properties of MgNb2O6 ceramics with Fe2O3 additives

The dielectric properties and microstructures of MgNb2O6 ceramics with Fe2O3 additions (0.5–2 wt %) prepared with a conventional solid-state route have been investigated. It is found that MgNb2O6 ceramics can be sintered at 1140°C due to the liquid phase effect of Fe2O3 additions. At 1140°C, MgNb2O6 ceramics with 0.5 wt % Fe2O3 addition possess a dielectric constant (er) of 20.5, a Q×f value of 70000 (9 GHz) and a temperature coefficient of resonant frequency (τf) of -49 ppm/°C. The Fe2O3-doped MgNb2O6 ceramics can find applications in microwave devices requiring low sintering temperatures.

Planar Octagon Monopole Antenna for UWB Applications

A planar octagon monopole antenna for ultrawideband(UWB) application is proposed and experimentally studied. The proposed antenna has wide impedance bandwidth from 2.8 GHz to more than 10.7 GHz with better than -10 dB return loss. The design is demonstrated assuming FR4 substrate with a relative dielectric constant of 4.4 and thickness of 1.6 mm. The size of the antenna is 40 mm×50 mm. Details of the proposed antenna design and simulation results for UWB operations are presented and discussed.

Effect of Annealing Temperature on Electrical Properties of ZnTe Layers Grown by Thermal Evaporation

The electrical properties of evaporated ZnTe films were investigated with emphasis on the effects of an annealing temperature from 600oC to 800oC by RTA technique. Crystallinity, carrier concentration, sheet resistance, and mobility are shown to be dependent on the annealing temperature. The highest carrier concentration and lowest sheet resistance are 7.9×1015 cm-3 and 9300 Ω/□ at an annealing temperature of 700oC, respectively. The mobility was found to vary from 20 to 50 cm2V-1S-1. The ZnTe thin films using thermal evaporation can find applications in solar cell or light emitting diodes

Fabrication of Ti-Doped ZnO Thin Films by Chemical Bath Deposition

Effect of thermal treatments on the structural and electrical properties of the chemical bath deposition derived Ti-doped ZnO thin films are studied. XRD results show that the annealed Ti-doped ZnO films with wurtzite structure are randomly oriented. Crystallite structure, carrier concentration, resistivity and mobility are found to be dependent on the treatment temperature. At a treatment temperature of 100°C, the Ti-doped ZnO film possesses a carrier concentration of 2.5×1020 cm-3, a resistivity of 2.8×10-3 Ω-cm, and a mobility of 12 cm2/Vs.

Printed octagon monopole UWB antenna with band-notch by modified U-shape slot

A planar octagon monopole UWB band-notched antenna is proposed and experimentally studied. It consists of an octagon patch with a modifed U-shaped notched, which intends to obtain frequency notched for WiMAX. The proposed antenna operates from 1.93 GHz to 11 GHz for return loss of less than -10dB with 5.26-6.4 GHz notched. The notch frequency of the proposed antenna can be adjusted by controlling the location of slot. The measured results are in reasonably good agreement with the simulated results. Details of the proposed antenna design and simulation results for UWB operations are presented and discussed.

Microwave Dielectric Characteristics of Zr0.8Sn0.2TiO4 Ceramics with WO3 Additives

The effects of low-level WO3 addition (up to 6 wt %) on the microstructures and microwave dielectric properties of Zr0.8Sn0.2TiO4 ceramics have been investigated. A second phase was not observed in Zr0.8Sn0.2TiO4 ceramics with 2–6 wt % WO3 added. Degradation in dielectric constant ( er) occurred for the doped Zr0.8Sn0.2TiO4 ceramics owing to the formation of a grain boundary phase. Moreover, the temperature coefficient of resonant frequency ( τf) was not significantly affected, while the unloaded quality factor Q was effectively increased by WO3 addition. An er of 33.4, a Q ×f of 56000 GHz, and τf of 0 ppm/°C were obtained for 4 wt % WO3-doped Zr0.8Sn0.2TiO4 ceramic sintered at 1400 °C for 3 h.

Properties of ZnTe Thin Films on Silicon Substrate

Zinc telluride thin films were deposited by thermal evaporation method on n-type Si substrate. The electrical properties of these films were investigated with special emphasis on the effects of a depositing temperature from 520°C to 560°C with various annealing temperatures by rapid thermal annealing (RTA) technique. Structural analysis through X-ray diffraction (XRD) was sensitive to the deposition conditions and annealing treatment. Crystallinity, carrier concentration, sheet resistance, resistivity and mobility are shown to be dependent on the thermal treatments.

Dielectric Properties of 0.2CaTiO3-0.8Li2CeO3 Ceramics

The dielectric properties and microstructures of Li2CeO3 doped CaTiO3 to form 0.2CaTiO3-0.8Li2CeO3 ceramic system prepared by solid-state method have been investigated. The structure of the materials is studied using X-Ray diffraction, and the microstructure is analyzed using scanning electron microscopy. The results indicated that the dielectric properties were associated with the sintering temperatures. The correlation between the microstructures and the sintering temperature was also discussed. For practical application, a dielectric constant (ϵr) of 11.9, a high Q × f value of 34,000 GHz, and a τf of −32 ppm/°C were developed for 0.2CaTiO3-0.8Li2CeO3 ceramics sintered at 750°C, and also can be used in low-temperature co-fired ceramics (LTCC) microwave devices.