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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,...
Helmet antennas have been investigated for various applications, such as military, construction, and disaster prevention. In their radio system operated at the low frequency, the half wavelength circular loop antenna, the folded dipole antenna, and the inverted-F antenna have been proposed. Since these antennas are arranged in proximity to the human head, the radiation efficiency is reduced and the...
A slender left-handed leaky wave omni-directional antenna, which is suitable for such small cell, has been proposed. This paper derives the equivalent circuit of the unit cell of the leaky wave omni-directional antenna and derives the intercell coupling matrix for the number of cells required.
In mobile base station antennas, linear array antennas are employed to achieve shaped beams in the vertical plane. Also, antennas are designed to achieve multi-frequency use. In the case of expanding multi-frequency range, conventional equal element spacing configuration shows a defect of producing grating lobes. In order to suppress grating lobes, unequal element spacing is promising. In this paper,...
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...
Helmet antennas have been considered for military and disaster prevention uses. This paper presents the inverted-F antenna on annular ground plane as an electrically small antenna of low operational frequency of 150 MHz. In comparison with the hemispherical ground plane, the gain and 10 g average local SAR can be maintained by removing the appropriate region in the ground plane.
The metamaterial design process provides significant change to the material selection of the general antenna design process. To apply metamaterials to small antennas, multi-layer ceramic capacitors (MLCCs) has been investigated to compose a small size and a compact structure for each unit cell. In this paper, the open and closed metamaterial structures composed of MLCCs are designed by the eigenmode...
The metamaterial design process provides significant change to the material selection of the general antenna design process. To apply metamaterials to small antennas, multi-layer ceramic capacitors (MLCCs) has been investigated to compose a small size and a compact structure for each unit cell. In this paper, the open and closed metamaterial structures composed of MLCCs are designed by the eigenmode...
In this study, we propose a novel leaky-wave omnidirectional antenna using a coplanar-strip-type composite right/left-handed (CRLH) line for application to a base station antenna used for a mobile communication system. Further, we realize an extremely slender omnidirectional antenna by adopting a polarization composite method. We also design a prototype antenna in the 3.5 GHz band and show the results...
In this paper, we propose a very simple broadband technique for the two types of the design of a sleeve antenna with a choke (SLAC) and compare the proposed antennas. This technique is only to load one cylindrical conductor on the choke of SLAC. The relative bandwidth of proposed antenna is 105% for VSWR≤3. The VSWR characteristics of proposed antennas are similar to each other.
This paperproposes a novel mobile base station antenna with a dielectric lens radome. The dielectric lens has a function to shape the radiation pattern which is useful to achieve low side lobe characteristics. In designing the dielectric lens, a ray tracing method has been developed in the MATLAB software. In order to achieve a slender lens shape, adequate radiation patterns for the feed radiator...
In recent years, metamaterials are strongly expected to be useful for antenna miniaturization. In general, to be used in small antennas, metamaterials must have a small size and a compact structure for each unit cell. In this report, metamaterial resonators composed of multi-layer ceramic capacitors (MLCC) excited by small loop antenna are investigated. The configuration of interior electrodes is...
Helmet antennas have been widely developed as wearable antennas for military and disaster prevention uses. To reduce the operational frequency band and overcome the gain reduction in proximity to human head, this paper presents the inverted-F antenna on the hemispherical metal ground plane. The arrangement of the antenna element and the feeding directions are examined in detail through electromagnetic...
Radiation patterns of present mobile base station antennas are designed to be low sidelobe characteristics. To achieve this radiation pattern, linear array feeds are employed. For simplicity of antenna configuration, authors considered to replace antenna radome by a lens antenna. The array feed also replaced by a single feed. However, it is considered that lens thickness will be main problem. This...
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 radar cross section (RCS) of an airplane is very important subject in a military use. As for a RCS estimation object, a scale down model is often employed for the ease of measurements. Recently, electromagnetic simulations of RCS become very convenient because of developments of high speed calculation methods such as MLFMM and HOBF in electromagnetic simulators employing MoM algorithm. As for...
Theoretical explanations of radiated, dissipated and stored energies of small antennas were shown in a textbook. However, practical values of these energies were not discussed previously. In this paper, these energies are obtained numerically through electromagnetic simulations. As for a study object, a normal-mode helical antenna is utilized, because stored electric and magnetic energies are simultaneously...
Theoretical treatments of stored and dissipated energies of small antennas were made previously. In this paper, these energies are examined numerically through electromagnetic simulations. As study example, a normal-mode helical antenna is utilized. At the self-resonant conditions, stored electric and magnetic energies are shown to be the same value. And, dissipated energies that are consist of radiated...
As basic studies of low radar cross section (RCS) structures, patch antennas with different terminal loads were selected became of convenience for calculation and measurement. Terminal conditions of the open, short and dummy were previously studied. And effects of low RCS characteristics were shown. In this paper, terminal conditions are expanded to high ohmic resistances. Effects of RCS reductions...
In multi-band base station antennas, interference toward neighboring cells at low operating frequency increases since tilting angle is frequency-independent and beamwidth in the vertical plane increases as decreasing the operating frequency. This paper presents a new low-profile phase shifter which comprises non-linear frequency-dependent characteristics. The proposed phase shifter is composed of...
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