Dong-Uk Sim

Design of Optimized Multilayer PIFA With the EBG Structure for SAR Reduction in Mobile Applications

This paper proposes an optimized multilayer planar inverted-F antenna (PIFA) with an electromagnetic bandgap (EBG) at personal communication services band for specific absorption rate (SAR) reduction. The EBG structure, which has bandgap capability and acts as a perfect magnetic conductor surface, can suppress surface waves and reduce undesired radiation from an antenna. Thus, the EBG structure is capable of preventing electromagnetic (EM) fields being emitted in the direction of the human head. To optimize the multilayer PIFA structure for SAR reduction, the EBG structure between the printed circuit board and antenna layer is designed first. Second, a parameter study about the EBG cell numbers, height, and location of the PIFA with the EBG structure is performed. Finally, the optimized multilayer PIFA with the EBG is investigated and the S-parameters, radiation patterns, total radiated power values, and SAR values are presented. The results demonstrate the reduction of SAR values while maintaining the antenna performance. Thus, the human head can be protected from hazardous EM fields using the EBG structure.

An internal triple-band antenna for PCS/IMT-2000/Bluetooth applications

An internal triple-band antenna fed by a microstrip line is proposed for operation in the PCS, IMT-2000, and Bluetooth bands. By using two branches of meander line, the desired resonant frequencies can be achieved. A broadband characteristic for each band is optimized by tuning the parts of the radiating patch and the size of each strip line segment. The proposed antenna and substrate are small enough to be built in a practical mobile handset. Details of the proposed technique and experimental results are presented and discussed.

A Compact Wideband Modified Planar Inverted

A compact wideband modified planar inverted F antenna (PIFA) with two shorting strips for 2.4/5.2-GHz wireless local area network (WLAN) operations is presented. As a starting point, two-branch strip lines derived from the dipole antenna structure are used to achieve the desired resonant frequency. One of them is connected to two shorting strips with the different length and width, and those strips generate additional resonant modes. A wideband characteristic can be optimized by tuning the parts of two shorted patches and size of each strip line segment. The proposed antenna has a low profile and can easily be fed by a 50-Omega coaxial cable. In addition to covering 2.4- and 5.2-GHz band, a wide impedance bandwidth from 2.94 to 5.82 GHz (|S11|<-10 dB, about 69% centered at 4.14 GHz) is obtained. The measured maximum radiation gains at the frequencies of 2.44, 4.14, and 5.2 GHz are about 1.6, 3.8, and 2.5 dBi, respectively. The proposed antenna is suitable for the multiband operations, covering 2.4/5.2-GHz WLAN operation

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In this paper, specific absorption rate (SAR) reduction at the PIFA type for a mobile phone using various types of EBG structure are tested. Two EBG structures, that is a via or a via-less, are designed. The EBG structures can reduce the surface wave and prevent the undesired radiation from the ground plane. Thus, the EBG structure which is designed for mobile terminal enables to comply with the exposure guideline. From the simulation and measured results demonstrated the reduction of the radiation pattern towards the direction of human head and the SAR value.

Antenna (PIFA) for 2.4/5-GHz WLAN Applications

A triple-band stubby antenna, fed by a coaxial probe, and a tuning technique are proposed for operating at PCS, IMT-2000, and Bluetooth bands. The proposed antenna, shielded by the antenna cover, consists of two radiating elements. The impedance matching and bandwidth for the proposed antenna are mainly affected by the length of the ground patch at the bottom of a small substrate. By properly choosing the size of the ground patch, the resonant frequencies can be easily adjusted, and a wide impedance bandwidth of 59.7% (|S/sub 11/| < -10 dB), which covers the Korean PCS (1750-1870 MHz), IMT-2000 (1920-2170 MHz), and Bluetooth (2402-2483.5 MHz) can be achieved. An omnidirectional radiation pattern is obtained, and a peak antenna gain of about 3 dBi or more is measured. The electrical characteristics of the proposed antenna make it attractive for use in mobile handset applications.

SAR reduction on a mobile phone antenna using the EBG structures

An internal triple-band antenna fed by a microstrip line is proposed for operating at PCS, IMT-2000, and Bluetooth bands. As a starting point, a two-branch meander-line antenna is used to achieve the desired resonant frequency. A broadband characteristic for each band can be optimized by tuning the parts of radiating meander lines and size of each strip line segment. Considering normal use situation, the initially designed structure of the proposed antenna is extended and modified to tune the desired frequency bandwidth on the placement of handset case and battery, and in the presence of the head. Detailed model of the handset case is implemented to check the effects of the phone case and battery on the antenna performance. The return loss and radiation patterns from the proposed antenna built in a phone case in the presence of the phantom head are presented. It is found that the battery and human head have a strong influence on the antenna input impedance, radiation patterns, and gain for the internal antenna configurations. The computational values are presented to validate the experimental results.

A wideband monopole antenna for PCS/IMT-2000/Bluetooth applications

In this paper, as one of those RFID tags, novel RFID tag antennas mountable on metallic objects using EBG surface for passive UHF/RFID applications. These tags achieve longer read ranges than tags using EBG surface, and can be utilized in various retail store products including metal, motor vehicles, and containers, etc. Details of the serial design and analysis of the proposed tag are described and the experimental results of the constructed prototype are presented.

A triple-band internal antenna: design and performance in presence of the handset case, battery, and human head

This paper propose a optimized multilayer PIFA in PCS bands based on the electromagnetic bandgap (EBG) for SAR reduction. The EBG structure which has bandgap capability and acts as PMC surfaces can reduce the surface waves and prevent the undesired radiation from the antenna. Thus, the EBG structure can reduce the electromagnetic fields toward the human head direction. First, to optimize of multilayer PIFA structure for SAR reduction, the EBG structure with the PCB and antenna layer is designed. And second, a parameter study of location and height of a PIFA with the EBG structure is performed. Finally, the optimized multilayer PIFA with EBG is investigated, both on the S-parameters, radiation patterns and on the SAR value. The results demonstrated the reduction of SAR value with maintaining the antenna performance and the human body can be protected from hazard electromagnetic fields.

Design of novel dipole-type tag antennas using electromagnetic bandgap (EBG) surface for passive RFID applications

In this paper, the SAR measurement values are compared with a conventional mobile handset and with EBG structures. In order to protect a human head from the exposure of electromagnetic field and to comply with the exposure guideline, the designed EBG components are inserted in a commercial US-PCS handset. The total width and length of the EBG structures are 31 mm and 8 mm, respectively. The measured results in this paper demonstrated the movement of a hot spot, the reduction of total radiated power toward the head direction and the reduction of the SAR in the human head.

Design of multilayer PIFA based on an EBG structure for SAR reduction in mobile applications

A compact wideband modified planar inverted antenna (PIFA) with two shorting strips for 2.4/5.2-GHz wireless local area network (WLAN) operations is presented. As a starting point, two-branch strip lines derived from the dipole antenna structure are used to achieve the desired resonant frequency. One of them is connected to two shorting strips with the different length and width, and those strips generate additional resonant modes. A wideband characteristic can be optimized by tuning the parts of two shorted patches and size of each strip line segment. The proposed antenna has a low profile and can easily be fed by a 50- coaxial cable. In addition to covering 2.4- and 5.2-GHz band, a wide impedance bandwidth from 2.94 to 5.82 GHz ( 10 dB, about 69% centered at 4.14 GHz) is obtained. The measured maximum radiation gains at the frequencies of 2.44, 4.14, and 5.2 GHz are about 1.6, 3.8, and 2.5 dBi, respectively. The pro- posed antenna is suitable for the multiband operations, covering 2.4/5.2-GHz WLAN operation.