Nguyen Quoc Dinh

Electrical characteristics of a very small normal mode helical antenna mounted on a wheel in the TPMS application

A very small NMHA having the size of 0.014 wavelength is developed for TPMS. The novel simple impedance matching structure is developed. As a result, antenna gain of −6.75 dBd is ensured in the case of the antenna mounted on a wheel.

Design method of a tap feed for a very small normal-mode helical antenna

Very small normal-mode helical antennas (NMHA) can achieve a high antenna gain in the metal proximity use. So, the NMHAs were developing to use for the RFID (Radio Frequency Identification) tags and the TPMS (Tire Pressure Monitoring System) sensor antenna placed in a tire. In order to achieve impedance matching to the radio unit, a tap feed structure is inevitable. In this paper, the usefulness of the tap feed is shown by an actual example of a RFID tag antenna. Next, the performance of the tap feed is analyzed with the equivalent circuit expression. The input impedance of the tap feed is clearly expressed in a closed form equation. By applying the self resonance condition to the preceding equation, the simple expression of the impedance step up ratio is derived. Moreover, comparisons of input impedances by equations and electromagnetic simulations are shown. Simulated and equation results agree well.

Simple design equations of tap feeds for a very small normal-mode helical antenna

A very small normal-mode helical antenna (NMHA) has been developed for sensor antennas of the tire pressure monitoring system (TPMS) [1] and tag antennas of the radio frequency identification (RFID) [2], because of the usefulness in metal proximity. In order to achieve an actual antenna applicable to radio units, an impedance matching structure was necessary. A simple tap structure was developed [1]. However, design method of a tap feed was not clarified. In this paper, important design data such as mutual inductances between a tap and the NMHA, step-up ratios of input resistances and simple design equations are shown.

Self-resonant structures of normal-mode helical antennas embedded in dielectric and magnetic materials

Normal-mode helical antennas (NMHA) are well known for achieving high antenna efficiencies in very small sizes when antenna structures are tuned to self-resonant situations. The design equation determining self-resonant structures were developed in free space conditions. However, in practically, NMHA mostly used dielectric or magnetic materials as cores. The design equation for these cases is not studied yet. In this paper, fundamental self-resonant structures are studied for NMHA placed in dielectric or magnetic material. In order to obtain correct calculation results, calculation models of an commercial electromagnetic simulator (FEKO) is studied. Many data for structural change from free space condition to inside materials are achieved. Moreover, input resistance and antenna efficiency changes are also obtained.

A design of compact ultra-wide band antenna

In this article, a new ultra-wideband (UWB) antenna for UWB application is proposed. This antenna is designed with the operation of bandwidth from 3.1 GHz to 10.6 GHz. The purpose is to design a simple and compact antenna with broad bandwidth VSWR ≤ 2. Antenna characteristics such as radiation pattern, maximal gain are also thoroughly investigated.

Simulation methods of a normal-mode helical antenna in a human body condition

In implantable antenna applications for human health care, normal-mode helical antenna (NMHA) is considered to be one of promising candidates. Due to antennas put inside human body, electromagnetic simulations are needed to model human body and clarify electrical characteristics of antennas. Electromagnetic performances of NMHA can be conveniently calculated by using Method of Moment (MoM). However, accuracies of calculated results were not clear. In this paper, another simulation method of finite element method (FEM) is employed as a reference. Calculated results such as self-resonant structures, electromagnetic field distributions, input impedances and radiation pattern are compared between MoM and FEM. Through very good agreements between two simulation methods, calculation accuracies of MoM are ensured.

A proposal of a compact Ultra-Wide Band antenna works as a magnetic dipole

Recently, the Ultra-Wideband Multi-Input Multi-Output technique has draw the intention of many researchers as it is very promising for high data rate wireless communication systems. In this paper, a new ultra-wideband (UWB) antenna with the size of 15 mm × 26 mm × 1.6 mm is proposed. The antenna works as a magnetic dipole and has the working bandwidth from 3.1 GHz to 10.6 GHz with VSWR ≤ 2. The antenna parameters such as radiation pattern, maximal gain are also investigated.

Asymmetrical radiation pattern synthesis of a linear array antenna by a least mean square method

In mobile base station antennas, linear array antennas are employing and asymmetrical radiation patterns are achieved. For multi frequency use, unequally spaced array configurations are preferable because of reducing grating lobes in higher frequency operations. Previously, radiation pattern synthesis methods were developed for equally spaced array configurations. In radiation pattern synthesis method, the least mean square (LMS) method was very conveniently used in mobile base station designing. The convenience of this method is obtaining array excitation coefficients by simply giving the objective radiation pattern. Moreover, the merit of this method is having the function of emphasizing design importance in the radiation angles that is called the weighting matrix. In this paper, a radiation pattern synthesis program based on LMS scheme is developed for unequally spaced array configuration. As an initial step, the accuracies of a developed program are examined. Through designing actual asymmetric radiation pattern with very low side lobe levels, the accuracies of program and effects of weighting matrix are ensured.

A method to miniaturize antenna structure for the 3G mobile device

This paper presents a miniaturization method of planar inverted F antenna structure by folded monopole antenna placed on FR4 dielectric. The proposed antenna comprises compact size (23 × 14 × 5 mm3), easy to make and provide enough bandwidth, which covers 3G band (VSWR ≤ 2). Using the simulation program to optimize antenna structure and calculate the antenna parameters in order to verify its applicability for the 3G devices.

A design of very small normal mode helical antenna for wireless communication systems

The normal mode helical antenna becomes an efficient radiator in the condition of the self resonance. When the antenna size is less than 0.03 wavelengths, the antenna input resistance becomes very small such as about 1 ohm. Therefore, the impedance matching structure is inevitable and its usefulness is required as well.