This review aims to summarise the progress in some materials and structures for electromagnetic applications, such as microwave absorption, electric shielding and antenna designs, which have been developed in recent years. Composites with spherical powders for microwave absorption focus mainly on those based on ferrites (especially hexagonal), carbonyl iron and related alloys and various newly emerged nanosized materials. Composites with long conductive fibres as fillers will be summarised, with speical attentions to prediction, measurment and evaluation of their performances. Metamaterials include structures for microwave absorbing applications, tunable materials or structures with reflection or transmission coefficients that are tunable by external magnetic or electric fields, and specially designed structures for microwave absorbing applications, with thickness much smaller than that of conventional composite materials and performances that can be optimised by the physical properties of substra...

Recent progress in some composite materials and structures for specific electromagnetic applications

An antenna device is provided. The antenna device may include a conductive radiator pattern formed on one surface of a dielectric substrate, an artificial magnetic conductor layer including at least one unit cell formed on the other surface of the dielectric substrate, and a shorting pin connected to the unit cell. The artificial magnetic conductor layer may be configured to form an induction current of the same phase with regard to a signal current flowing through the conductive radiator pattern.

Antenna device and electronic apparatus having the same

The introduction of electromagnetic (EM) media with unique field manipulation properties, collectively labelled as metamaterials, has boosted the interest toward the design, the fabrication, and the testing of artificial materials whose features can be engineered according to the applicative requirements and user objectives. In this framework, the long-term promise of reconfigurable metamaterial theory (i.e., the possibility to change the EM response of a 2-D/3-D material arbitrarily and in real time) has given the designers an extremely wide number of new degrees of freedom for the synthesis of innovative adaptive systems. Moreover, successful experimental validations of reconfigurable metamaterials in the entire EM spectrum from microwaves to optical frequencies have further stimulated academic and industrial interests in developing devices with enhanced performances, efficiency, and robustness. Nevertheless, the exploitation of reconfigurable metamaterials in commercial devices is still an open problem with several challenges from both the theoretical and technological viewpoints. This paper is then aimed at reviewing the latest advances on reconfigurable metamaterial engineering from the methodological perspective also providing a comprehensive and balanced survey on latest concepts, current trends, and envisaged future developments on this active field of research.

Reconfigurable Electromagnetics Through Metamaterials—A Review

A novel dual-band 4-shaped printed multiple-input-multiple-output (MIMO) antenna system of two elements is designed and fabricated for Long Term Evolution (LTE) wireless handheld and portable terminals. The low frequency band covered is 803-823 MHz, and the high frequency band covered is 2440-2900 MHz. The isolation between the two elements was more than 17 dB in the low band after using a defected ground plane structure (DGS) between the two antenna elements. The overall size of the printed MIMO antenna system was 50× 100×1.56 mm3.

A Dual-Element Dual-Band MIMO Antenna System With Enhanced Isolation for Mobile Terminals

A novel dual-broadband multiple-input-multiple-output (MIMO) antenna system is developed. The MIMO antenna system consists of two dual-broadband antenna elements, each of which comprises two opened loops: an outer loop and an inner loop. The opened outer loop acts as a half-wave dipole and is excited by electromagnetic coupling from the inner loop, leading to a broadband performance for the lower band. The opened inner loop serves as two monopoles. A combination of the two monopoles and the higher modes from the outer loop results in a broadband performance for the upper band. The bandwidths (return loss >;10 dB) achieved for the dual-broadband antenna element are 1.5-2.8 GHz (~ 60%) for the lower band and 4.7-8.5 GHz (~ 58\%) for the upper band. Two U-shaped slots are introduced to reduce the coupling between the two dual-broadband antenna elements. The isolation achieved is higher than 15 dB in the lower band and 20 dB in the upper band, leading to an envelope correlation coefficient of less than 0.01. The dual-broadband MIMO antenna system has a compact volume of 50×17×0.8 mm3, suitable for GSM/UMTS/LTE and WLAN communication handsets.

A Dual-Broadband MIMO Antenna System for GSM/UMTS/LTE and WLAN Handsets

A method to extend the bandwidth of metamaterial (MTM) antennas using a composite right/left-handed transmission line (CRLH-TL) is presented. The resonance modes and wideband characteristics of MTM antennas are analyzed and described using dispersion diagrams based on the CRLH-TL theory. Based on the analysis, we propose an efficient way to extend the bandwidth of MTM antennas, which has been verified by both full-wave simulations and experiments. The proposed analysis can be used to design novel wideband MTM antennas and other microwave components for mobile handset applications.

Bandwidth Enhancement of Metamaterial Antennas Based on Composite Right/Left-Handed Transmission Line

A long-term evolution (LTE) MIMO ferrite antenna was fabricated on Ni0.5Mn0.2Co0.07Fe2.23O4 ferrite substrate (14 × 7 × 3 mm3) and characterized for antenna performance. Measured return loss and isolation were -26 and -16.4 dB at 720 MHz, respectively. Correlation coefficient calculated from experimental S-parameters (S11, S22, S12, and S21) was less than 0.02 in the LTE band. Three-dimensional peak gain at 746 MHz was measured to be -8.83 dBi for antenna 1 and -8.32 dBi for antenna 2. These low antenna gains are attributed to high magnetic loss of ferrite substrate. Performance simulation suggests that antenna gain can be further improved up to -3.14 dBi with the use of low-loss ferrite.

Miniature Long-Term Evolution (LTE) MIMO Ferrite Antenna

A tunable internal antenna with an epsilon negative zeroth order resonator (ENG-ZOR) for digital video broadcasting-handheld service is proposed in this paper. The antenna consists of two helical radiators, an ENG ZOR with two inductors and a variable capacitor to adjust the resonant frequency. The resonant frequency of the designed antenna can be swept from 474-702 MHz by adjusting the capacitance of the variable capacitor by controlling the DC bias voltage. The proposed antenna has a very compact size of 40 mm times 5 mm times 5 mm.

A Tunable Internal Antenna With an Epsilon Negative Zeroth Order Resonator for DVB-H Service

In this paper, a low-loss Ni-Mn-Co ferrite (Ni0.76Mn0.24-xCoxFe2O4 with x = 0-0.04) has been developed for miniaturization and performance improvement of mobile handset antennas. The developed ferrite material has almost equal permittivity and permeability of 7-9, as well as sufficiently low dielectric and magnetic loss tangent less than 0.001 and 0.01 below 200 MHz, respectively. Miniaturization factor of about 8 and normalized impedance of about 1 were obtained at 200 MHz. A helical antenna operating at terrestrial digital multimedia broadcasting (T-DMB, 174-216 MHz) band was fabricated on the ferrite substrate, which has compact size, low loss, wide bandwidth, and good radiation performance.

Miniaturized T-DMB Antenna With a Low–Loss Ni–Mn–Co Ferrite for Mobile Handset Applications

A compact multiband antenna using a double-negative (DNG) zeroth-order resonator (ZOR) for global system for mobile communications (GSM850/1800/1900, 824894/17101880/18501990 MHz), wideband code division multiple access (WCDMA, 19202170 MHz), and wireless broadband (WiBro, 2.32.4 GHz) operations is presented. The proposed antenna having a total volume of 40 times 6 times 3 mm3 comprises a lower-band ZOR antenna part and an upper-band ZOR antenna part. The zeroth-order resonant properties are analyzed by magnitude and phase distributions of the surface magnetic field using near-field scanning system. The performance of the antenna is verified by experimental data obtained from fabrication and measurement. The antenna offers omnidirectional radiation patterns and measured radiation efficiencies exceeding about 53% and 41% for lower and upper bands, respectively.

Gi-Ho Kim

Papers

Bandwidth Enhancement of Metamaterial Antennas Based on Composite Right/Left-Handed Transmission Line

Miniature Long-Term Evolution (LTE) MIMO Ferrite Antenna

A Tunable Internal Antenna With an Epsilon Negative Zeroth Order Resonator for DVB-H Service

Miniaturized T-DMB Antenna With a Low–Loss Ni–Mn–Co Ferrite for Mobile Handset Applications

A Compact Multiband Antenna Based on DNG ZOR for Wireless Mobile System