The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications. By Christophe Caloz and Tatsuo Itoh.

Space-Time Block Coding for Wireless Communications

In general, Micropower Impulse Radar (MIR) depends on Ultra-Wideband (UWB) transmission systems. UWB technology can supply innovative new systems and products that have an obvious value for radar and communications uses. Important applications include bridge-deck inspection systems, ground penetrating radar, mine detection, and precise distance resolution for such things as liquid level measurement. Most of these UWB inspection and measurement methods have some unique qualities, which need to be pursued. Therefore, in considering changes to Part 15 the FCC needs to take into account the unique features of UWB technology. MIR is applicable to two general types of UWB systems: radar systems and communications systems. Currently LLNL and its licensees are focusing on radar or radar type systems. LLNL is evaluating MIR for specialized communication systems. MIR is a relatively low power technology. Therefore, MIR systems seem to have a low potential for causing harmful interference to other users of the spectrum since the transmitted signal is spread over a wide bandwidth, which results in a relatively low spectral power density.

/pdf/response-to-fcc-98-208-notice-of-inquiry-in-the-matter-of-3attixctl7.pdf

Response to FCC 98-208 notice of inquiry in the matter of revision of part 15 of the commission's rules regarding ultra-wideband transmission systems

We present a flexible, compact antenna system intended for telemedicine applications. The design is based on an M-shaped printed monopole antenna operating in the Industrial, Scientific, and Medical (ISM) 2.45 GHz band integrated with a miniaturized slotted Jerusalem Cross (JC) Artificial Magnetic Conductor (AMC) ground plane. The AMC ground plane is utilized to isolate the user's body from undesired electromagnetic radiation in addition to minimizing the antenna's impedance mismatch caused by the proximity to human tissues. Specific Absorption Rate (SAR) is analyzed using a numerical human body model (HUGO) to assess the feasibility of the proposed design. The antenna expresses 18% impedance bandwidth; moreover, the inclusion of the AMC ground plane increases the front to back ratio by 8 dB, provides 3.7 dB increase in gain, in addition to 64% reduction in SAR. Experimental and numerical results show that the radiation characteristics, impedance matching, and SAR values of the proposed design are significantly improved compared to conventional monopole and dipole antennas. Furthermore, it offers a compact and flexible solution which makes it a good candidate for the wearable telemedicine application.

Flexible and Compact AMC Based Antenna for Telemedicine Applications

The electromagnetic interaction between the antenna and the human head is reduced with materials and metamaterials. The reduction of Specific Absorption Rate (SAR) with materials and metamaterial is performed by the finite-difference time-domain method with Lossy-Drude model by CST Microwave Studio. The metamaterials can be obtained by arranging split ring resonators (SRRs) periodically. The SAR value has been observed by varying the distances between head model to phone model, different width, different thickness, and different height of material and metamaterial design. Materials has achieved 47.18% reduction of the initial SAR value while metamaterial achieved a reduction of 42.12%.These results can provide helpful information in designing the mobile communications equipments for safety compliance.

https://www.jpier.org/pierc/pierc09/05.09062303.pdf

Reduction of specific absorption rate (SAR) in the human head with materials and metamaterial

Investigation of dosimetry in human head model for a helical antenna with mobile phone

In this paper, a comparative study of several antennas commonly used in portable telephones is investigated. These include a monopole, a helix, a patch and a PIFA antenna. Each one of these structures is modeled and numerically tested using finite-difference time-domain (FDTD) method by using CST Microwave Studio. The testing procedure involves antenna simulation in the proximity of the human head and hand. The behavior of each antenna is evaluated for variable distances from the head geometry (0 - 20 mm). The simulation outputs used as measures for this comparative study include the specific absorption rate (SAR). The computed SAR levels within each of the considered tissues vary for the four antennas under investigation and are within the determined health safety standards. Results suggest that the patch antenna may be the structure of choice when considering safety standards, as its radiation yields the lowest local SAR in the head tissues.

Analysis of SAR Levels in Human Head Tissues for Four Types of Antennas with Portable Telephones

In this paper, reducing specific absorption rate (SAR) with materials attachment is investigated. The finite-difference time-domain method with lossy-Drude model is adopted in this study. The methodology of SAR reduction is addressed and the effects of attaching location, distance, and size of ferrite sheet material on the SAR reduction are investigated. Materials have achieved a 47.68% reduction of the initial SAR value for the case of 1 gm SAR. These results suggest a guideline to choose various types of materials with the maximum SAR reducing effect for a phone model.

http://www.wseas.us/e-library/conferences/2010/Penang/ELECTRO/ELECTRO-07.pdf

Design of material attachment for SAR reduction in human head

Analysis of the resonance response improvement of a planar C-band (4–8 GHz) antenna is proposed using parasitic element method. This parasitic element based method is validated for change in the active and parasitic antenna elements. A novel dual-band antenna for C-band application covering 5.7 GHz and 7.6 GHz is designed and fabricated. The antenna is composed of circular parasitic element with unequal microstrip lines at both sides and a rectangular partial ground plane. A fractional bandwidth of 13.5% has been achieved from 5.5 GHz to 6.3 GHz (WLAN band) for the lower band. The upper band covers from 7.1 GHz to 8 GHz with a fractional bandwidth of 12%. A gain of 6.4 dBi is achieved at the lower frequency and 4 dBi is achieved at the upper frequency. The VSWR of the antenna is less than 2 at the resonance frequency.

/pdf/analysis-of-resonance-response-performance-of-c-band-antenna-4oh5rtg62c.pdf

Norbahiah Misran

Papers

Reduction of specific absorption rate (SAR) in the human head with materials and metamaterial

Investigation of dosimetry in human head model for a helical antenna with mobile phone

Analysis of SAR Levels in Human Head Tissues for Four Types of Antennas with Portable Telephones

Design of material attachment for SAR reduction in human head

Analysis of resonance response performance of C-band antenna using parasitic element