Zhan Li

University of California, Los Angeles, Los Angeles, CA, United States

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Publications (6)3.5 Total impact

  • Zhan Li, Y. Rahmat-Samii
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    ABSTRACT: This paper discusses the specific absorption rate (SAR) issue in handset antenna designs from the system level. Four planar inverted F antenna (PIFA) models were designed for the personal communication system (PCS) frequency band (1850 ∼ 1990 MHz, also referred to as the 1900 MHz band). The free-space and against-the-head antenna efficiencies are measured and analyzed. The measured SAR were normalized by adjusting the transmit (TX) power. Then the antenna efficiencies were combined together to obtain the total radiated power (TRP), which is one of the requirements to evaluate the current handset antenna performance.
    Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005
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    ABSTRACT: This paper compares four planar inverted “F” antenna (PIFA) models designed for the personal communication system (PCS) frequency band (1850–1990 MHz, also refer to as the 1900-MHz band). The ground-plane size, the dielectric substrate, and the feeding pin are fixed for all the antenna models. By moving the ground pin, three different-size patches are tuned to the 1900-MHz band. The fourth model is a dual-band design with a J-shaped slot. The impedance bandwidth and the free-space antenna efficiency are measured. The impact of the presence of a phantom head on the efficiency is also shown and analyzed. A prototype transmitter is then integrated into the antenna models with a mechanical chassis for specific absorption rate (SAR) measurements. The measured SAR distribution shows that by relocating the ground pin of the PIFA, the SAR can be reduced. For each case, the transmit (TX) power is adjusted to normalize the SAR, and then the total radiated power (TRP) is calculated and compared. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 569–573, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21054
    Microwave and Optical Technology Letters 07/2005; 46(6):569 - 573. · 0.59 Impact Factor
  • Zhan Li, Y. Rahmat-Samii
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    ABSTRACT: As commercial needs have expanded the functions of the wireless cellular handsets, multiantenna development in one handset has become more and more common. This paper addresses a multiantenna solution for the wireless handset application. A planar inverted "F" antenna (PIFA) was designed as the main antenna of the handset to cover the 800 MHz band (824 MHz-894 MHz) and the 1900 MHz band (1850 MHz-1990 MHz). A side-mounted inverted "F" antenna (IFA) was designed as the 1575.42 MHz global positioning system (GPS) antenna. The location of the feed/ground pins of both antennas affected not only the total antenna efficiency, but also the polarization of the GPS IFA. The length of the GPS IFA affected the isolation between the two antennas and the specific absorption rate (SAR) of the PIFA at the 1900 MHz band. A three-dimensional efficiency measurement of the prototypes in both free space and against-head position will be presented. Measurement of SAR and its distribution will also be presented to demonstrate the impact of the IFA on the near field of the PIFA.
    IEEE Transactions on Antennas and Propagation 06/2005; · 2.33 Impact Factor
  • Source
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    ABSTRACT: In this paper, a circuit model is developed in RF ADS in order to simulate the coupling effect of a retracted whip on a planar inverted-F antenna (PIFA) for wireless-handset application. The PIFA is designed as the main antenna of the handset to cover the 800-MHz (824–894 MHz) and 1900-MHz (1850–1990 MHz) bands. A parasitic whip antenna is used to improve the performance of the PIFA, especially when the handset is used against the human head. In such a whip–PIFA combination environment, the retracted whip will degrade the PIFA performance if it is not designed carefully. The purpose of this paper is to present an efficient method to optimize the PIFA performance when the whip antenna is in the retracted position. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 210–215, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20590
    Microwave and Optical Technology Letters 02/2005; 44(3):210 - 215. · 0.59 Impact Factor
  • Zhan Li, Y. Rahmat-Samii
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    ABSTRACT: In this paper, a circuit model was developed in RF ADS to simulate the coupling effect of a retracted whip on a PIFA (Planar Inverted "F" antenna) in a wireless handset application. A PIFA was designed as the main antenna of a handset to cover the 800 MHz band (824 MHz ∼ 894 MHz) and 1900 MHz band (1850 MHz ∼ 1990 MHz). A parasitic dual band whip antenna was used to improve the performance of the PIFA especially when the handset is used against the head. In such a whip-PIFA combination environment, the retracted whip degrades the PIFA performance if it is not designed carefully. The purpose of this paper is to present an efficient method to optimize the PIFA performance when the whip is in retracted position.
    Antennas and Propagation Society International Symposium, 2004. IEEE; 07/2004
  • [Show abstract] [Hide abstract]
    ABSTRACT: A dual band PIFA (planar inverted "F" antenna) is designed for the 800 MHz band (824-894 MHz) and 1900 MHz band (1850-1990 MHz) that are the current US carrier frequency bands for mobile service. The PIFA has a J-shaped slot on a fixed substrate. The ground plane size has very small variation. The substrate is 10 mm thick with a dielectric constant of 2.25. The ground plane area is 3 times the area of the PIFA. A coaxial feed is used in the numerical simulation (Ansoft HFSS). Bandwidth enhancement for both bands is investigated.
    Antennas and Propagation Society International Symposium, 2003. IEEE; 07/2003

Publication Stats

71 Citations
3.50 Total Impact Points

Institutions

  • 2003–2005
    • University of California, Los Angeles
      • Department of Electrical Engineering
      Los Angeles, CA, United States