A novel wideband unidirectional antenna composed of a planar electric dipole and a shorted patch antenna is presented. The antenna is excited by a Γ-shaped strip feed line. A wide impedance bandwidth of 43.8% (SWR≤1.5) from the frequency of 1.85 to 2.89 GHz is achieved. Stable radiation pattern with low cross- polarization, low backlobe radiation, nearly identical E-and H-plane patterns and an antenna gain of ~8dBi is found across the entire operating bandwidth.

https://www.ijmot.com/ijmot/uploaded/fJAl1POcc7.pdf

A New Wideband Unidirectional Antenna Element

High-permittivity ceramics make it possible to noticeably miniaturize passive microwave devices. These ceramics must fulfil the requirements of high permittivity, very low dielectric losses and an extremely low temperature dependence of permittivity to yield temperature-stable resonators. Recent progress has been made in understanding the physics of microwave ceramics, particularly the property-structure relationship, in developing new materials with higher permittivity, better temperature stability and considerably lower sintering temperature, and in making co-fired multilayer devices possible, as well as in developing new microwave devices such as oscillators, antennas and band-pass filters.

Microwave ceramics for resonators and filters

High-frequency dielectric properties of A5B4O15 (A=Ba, Sr, Mg, Zn, Ca; B=Nb, Ta) dielectric ceramics are studied by means of the microwave cavity technique, a combination of far-infrared reflection and transmission spectroscopy and time-resolved terahertz transmission spectroscopy Microwave permittivity e′ and Q×f factor vary, depending on the chemical composition, between 11 and 51, and 24 and 88 THz, respectively The temperature coefficient τf varies between −73 and 232 ppm/°C, and in two samples |τf| is less than 15 ppm/°C It is shown that the microwave permittivity e′ of the ceramics studied is determined by the polar phonon contributions and that linear extrapolation of the submillimeter dielectric loss e″ down to the microwave region is in agreement with the microwave data of single phase samples The relationship among phonon spectra, the crystal structure, and the unit cell volume is discussed

High frequency dielectric properties of A5B4O15 microwave ceramics

This paper introduces a folded planar monopole antenna, which has a very low profile of about one twentieth of the wavelength of the lowest operating frequency. The effect is achieved by using a bended rectangular radiating patch and an inverted L-shape ground plane. The proposed antenna can be used in multiband operation, with omnidirectional radiation patterns for all operating bands. Its impedance bandwidth, determined by 10 dB return loss, covers almost all present wireless communication systems: Global System for Mobile Communication (GSM), Digital Communication System (DCS), Personal Communication System (PCS), Universal Mobile Communication System (UMTS), and Industrial Science Medical (ISM) band. This paper presents the design and experimental results of the proposed antenna. Moreover, the study also investigates the tuning effects of the geometry parameters on impedance matching.

Multiband folded planar monopole antenna for mobile handset

Microwave ceramic dielectric resonator materials in the BaO-TiO2-Nb2O5Ta2O5 system such as BaTiNb4O13, BaTiTa2Nb2O13, BaTiTa4O13, Ba3Ti4Nb4O21, Ba3Ti4Ta4O21, Ba3Ti5Nb6O28, Ba3Ti5Ta6O28 and Ba3Ti5Nb3Ta3O28 have been prepared by the conventional solid state ceramic route. They have relatively high dielectric constant and high quality factor. The resonator materials are characterized by X-ray diffraction and scanning electron microscopy (SEM) methods. The BaTiNb4O13Ba3Ti5Nb6O28 and Ba3Ti5Nb3Ta3O28 have small temperature variation of the resonant frequency and are possible microwave dielectric resonator materials for practical applications.

New low loss microwave dielectric ceramics in the BaO-TiO2-Nb2O5Ta2O5 system

Perfect blazing of reflector-backed thin strip gratings to n = ? 1 spectral order for both TE and TM polarisations is compared with corrugated reflection gratings. The strip gratings are shown to be simulating effects of rectangular corrugations in conducting surfaces.

Reflector-backed perfectly blazed strip gratings simulate corrugated reflector effects

The authors present the results of a detailed experimental investigation exploring the possibility of improving the impedance bandwidth of a printed dipole antenna. This configuration can give considerable enhancement of impedance bandwidth without adversely affecting the efficiency of the antenna. Specifically, the new microstrip version of the FMDA (flared microstrip dipole antenna) has a bandwidth twice that of a conventional dipole antenna. This enhancement in the bandwidth is not accompanied by any losses. It is noted that this compact broadband microstrip dipole is a substitute for conventional dipoles in phased-array antennas for terrestrial applications. >

Bandwidth enhancement by flared microstrip dipole antenna

Synthesis, characterisation and properties of ceramics for application as dielectric resonators in microwave circuits

/pdf/dielectric-properties-of-ba5nb4o15-ceramic-52ok9vwmzu.pdf

Dielectric Properties of Ba5Nb4O15 Ceramic

The development of reflector-backed strip gratings exhibiting properties like the elimination of specular reflections from a conducting surface for normal and near-normal incidence is reported. This is not possibly by conventional corrugated metallic surfaces. Perfect blazing to n = −1 spectral order is also provided by the developed system. This technique offers a simple and inexpensive method for the simulation of corrugated horns.

K.A. Jose

Papers

Reflector-backed perfectly blazed strip gratings simulate corrugated reflector effects

Bandwidth enhancement by flared microstrip dipole antenna

Synthesis, characterisation and properties of ceramics for application as dielectric resonators in microwave circuits

Dielectric Properties of Ba5Nb4O15 Ceramic

Low backscattered TM-polarised strip gratings