Ik-Guen Choi

A Small Broadband Antenna for Wibro/WLAN/Mobile WiMAX

In this paper, we propose a small broadband antenna for mobile device. The proposed antenna consists of a printed rectangular monopole antenna and a parastic element connected to ground using narrow meander line and it is designed on a FR-4 substrate that has a thickness of 0.8 mm and a dielectric constant of 4.4. The FR-4 substrate`s size is 50 mm90 mm comparable to the real mobile device. The fabricated antenna`s size is 12.5 mm10.5 mm0.8 mm and the measurement shows -10 dB return loss bandwidth of 2,200~6,000 MHz and gains of 2.86~4.01 dBi. Accordingly, the proposed antenna can support mobile device for WiBro(2,300~2,380 MHz), WLAN(IEEE 802.11b/g/n: 2,400~2,480 MHz, IEEE 802.11a: 5,150~5,825 MHz), and mobile WiMAX(IEEE 802.16e : 2,500~2,690 MHz, 3,400~3,600 MHz) service bands.

The Design of Electronically Beam Steeling Array Antenna Using 4 Parasitic Elements

This paper proposes an electronically beam steering array antenna, consisting of single fed active element and 4 parasitic elements, operating in 5.8 GHz ISM band. Beam steering can be achieved by controlling the reactance of the variable reactance control circuit connected to the load of the parasitic elements without using the high cost phase shifters. The proposed antenna realizes beam scanning of E-plane and H-plane with the below -10 dB return loss in ISM band. The gain of the in E-plane and in H-plane is shown in the scanning range.

ESPAR(Electronically Steerable Parasitic Array Radiator) Antenna Composed of Uniplanar Yagi Dipole and Two Parasitic Dipoles

This paper proposes an small electronically steerable parasitic array radiator composed of a uniplanar dipole as a feeding element and two dipoles as parasitic elements. The fabricated antenna shows by measurement the gain between azimuth range in the dipole vertical plane and -10 dB return loss within , which includes UNII band.

Miniaturization of Circularly Polarized Microstrip Antenna for RFID Portable Reader at 900 MHz Band

This paper presents the miniaturization of circularly polarized microstrip patch antenna for UHF-band RFID portable reader. The proposed antenna has a group of four I-slots on a conventional corner-truncated square microstrip patch and it is shown that the antenna size is reduced compared to the antenna without I-slots. A 76 mm by 76 mm small antenna with four I-slots is fabricated with 6.4 mm thick FR4 substrate and its 10 dB return loss bandwidth, the gain and the axial ratio are measured to be , , and within the 10 dB return loss bandwidth, respectively.

Multi-Turn Circular Loop Antenna for Portable Terrestrial DMB

In this paper, we present a multi-turn circular loop antenna for portable terrestrial DMB. In order to satisfy the two contradictory requirements of small antenna size and high receiving capability, the proposed antenna`s diameter and turns are fixed to be 4 mm and 80 turns, respectively and its quality factor is set 1 in order to have high transfer function. The fabricated antenna length is 30 mm as small and its measured gain is -15 dBd. The antenna receiving power is verified by measurement very comparable with the receiving power of a commercial terrestrial DMB monopole antenna of length 190 mm.

Bandwidth Improvement of Circularly Polarized Microstrip Antenna for an UHF RFID Portable Reader

In this paper, circular polarized microstrip antenna with a conducted hollow cylinder-typed via around the coaxial probe is proposed to enhance the bandwidth of an RFID portable reader microstrip antenna. An antenna of thickness of 6.4 mm and size of is manufactured with FR4 substrate and its 10 dB return loss bandwidth is measured to be 92 MHz, which is about three times large than the same size`s microstrip antenna without hollow cylindrical via. The measured antenna gain and the axial ratio at each are and within 10 dB return loss bandwidth, respectively.

A Study on the Analysis of UWB Interference to WiMAX and Mitigation Method of Transmit Power Control

This paper presents the analysis of the potential ultra-wideband(UWB) interference to WiMAX at 3.5 GHz bands and the mitigation method using transmit power control(TPC) of UWB system. UWB interference effect is evaluated with WiMax`s outage probability over UWB density when multiple UWB systems and single WiMAX receiver distribute in unit area of 1, When UWB distribution density is 20 and the dynamic range of TPC is 30 dB, UWB interference effect with TPC is decreased by 42 % rather than that without mitigation scheme. Finally, we describe that the proposed TPC is an effective method to mitigate UWB interference to WiMAX.

Proposed Analytic Modeling for the Performance Effects of UWB on Broadband Network

This paper evaluates the interference effect of Ultra-wideband devices on the broadband network. Also, an analytic scheme based on the system level simulation is proposed. A proposed analytic modeling approach includes an assumed scenario based on a geometric model, the estimation of an interfering UWB power level, and the approach based on the system level simulation for the evaluation. Results show throughput losses or outages of the broadband network due to UWB interference. As a conclusion of research, UWB emission should be limited to protect the broadband network.

Enhanced MVDR beamforming implementation with arbitrary linear arrays on DS/CDMA

The efficient scheme for enhancing the performance of the MVDR beamforming for DS/CDMA systems is proposed. The main focus of the proposed scheme is to enhance the practical estimation of an array response vector for the MVDR beamforming on the arbitrary geometry structure of antenna arrays. Thus, the proposed scheme used the real Toeplitz-plus-Hankel approximation (RTHA) scheme to obtain the covariance matrix having the theoretical property of an overall noise-free signal. Computer simulation results are presented to show the effectiveness of the proposed scheme.