Hyeonjin Lee

Wide-band high-efficiency printed loop antenna design for wireless communication systems

A new wide-band high-efficiency coplanar waveguide-fed printed loop antenna is presented for wireless communication systems in this paper. By adjusting geometrical parameters, the proposed antenna can easily achieve a wide bandwidth. To optimize the antenna performances, a parametric study was conducted with the aid of a commercial software, and based on the optimized geometry, a prototype was designed, fabricated, and tested. The simulated and measured results confirmed that the proposed antenna can operate at (1.68-2.68 GHz) band and at (1.46-2.6 GHz) band with bandwidth of 1 and 1.14 GHz, respectively. Moreover, the antenna has a nearly omnidirectional radiation pattern with a reasonable gain and high efficiency. Due to the above characteristics, the proposed antenna is very suitable for applications in PCS and IMT2000 systems.

Compact band-notched ultra-wideband antenna

A novel band-notched ultra-wideband antenna having small dimensions (12.7×22×1.6 mm) is proposed. With the use of a modified ground plane, a microstrip feed with bevel, and parallel dual patches, the proposed antenna has very wide impedance bandwidth measured at 8.18 GHz (2.97 to 11.15 GHz, defined by 2:1 VSWR). By inserting slits in the ground plane, a band-notched frequency of 5.12 to 5.88 GHz is achieved. The transmission loss and group delay are measured and discussed.

A design and fabrication of bandpass filter using miniaturized microstrip square SIR

A four-pole quasi-elliptic function bandpass filter of 1.95 GHz center frequency with 60 MHz bandwidth for IMT-2000 is designed and fabricated using the miniaturized square stepped impedance resonator (SIR). The nonuniform finite difference time domain (NUFDTD) method is used to design the resonator and to calculate the coupling coefficient of three basic structures. The size reduction of miniaturized square SIR resonator is about 50% compared with a square open loop resonator. A bandpass filter using this resonator show good microwave characteristics with harmonic suppression of about -19 dB at 4.76 GHz. The results of measurements are almost similar to those of simulation.

Design of dual polarized antenna for DCS, UMTS, WiBro base stations

In this paper, we proposed the dual polarization antenna for DCS, UMTS, and WiBro bands. To extend the impedance band width, the proposed antenna used the square loop radiators. In addition, by square loop radiators, the dimensions of an antenna are reduced. As a result of measurement after compensation, we can see that the first port is less than −14dB, the second port is less than −14dB and intra isolation is less than −25dB. Additionally, a gain of the antenna is more than 9dBi. This polarization diversity antenna element can be used to form an array antenna for a wireless communication base station.

Modified annular ring slot antenna for dual WLAN band application

In this paper, the modified annular ring slot antenna is proposed for 2.4/5-GHz dual WLAN band operation. The higher order resonant modes in the annular ring slot are used to control the second operating frequency. The proposed antenna is printed on a FR-4 substrate, and has dimensions of 50 times 50 times 1.2 [mm] with a ground plane. The frequency ratio of the two operating frequencies can be adjusted from 1.97 to 2.64 with geometric values. The measured impedance bandwidths (VSWR<2) of the proposed antenna are approximately 13.2% for the 2.4-GHz band and 40% for the 5-GHz band and the peak gains are 3.74, 4.12 and 5.25 dBi for 2.45, 5.35 and 5.8 GHz bands, respectively.

A design of printed square loop antenna for omni-directional radiation patterns

In this paper, for dual band operation of both PCS and IMT2000, we propose a wideband antenna with printed square loop configuration. The proposed antenna has the CPW-feed structure on the same plane with radiating element. The calculated and measured bandwidths for 15 dB return loss are 1 GHz (1.68/spl sim/2.68 GHz) and 1.14 GHz (1.46/spl sim/2.6 GHz), respectively. The fabricated antenna has nearly omni-directional radiation pattern, and measured antenna gain of 2.67 dBi. These results confirm that proposed antenna could be used in both PCS and IMT2000 band operation.

Miniaturized bandpass filter with improved stopband characteristics using microstrip interdigital-loop resonator

A four-pole quasi-elliptic function bandpass filter is designed and fabricated using a miniaturized microstrip interdigital-loop resonator. The novel microstrip interdigital-loop resonator is able to control spurious responses in a compact size. A bandpass filter using this resonator shows good microwave characteristics with harmonic suppression of about -15 dB at 6.52 GHz, which is 3.34 f/sub 0/, where f/sub 0/ is the midband of frequency of a bandpass filter. The results of measurements are almost similar to those of simulation.

Compact chip monopole antenna with parasitic patch for GPS applications

A chip monopole antenna with a parasitic patch is proposed for GPS applications. To reduce the dimensions of the antenna, the chip monopole antenna is composed of stacked meander, helix structures, and a parasitic patch. The impedance and radiation characteristics of the antenna are investigated. The measured results show that the proposed antenna, having compact dimensions of 3.6 × 5 × 1.3 mm, has a bandwidth of 60 MHz (1.53–1.59 GHz) and a maximum radiation gain of 0.53 dBi.

Design of circular polarized microstrip aperture coupled patch antenna for 5.8 GHz ISM band

The demand for using wireless communication systems which make mass memory information and high speed contact possible has increased, recently. A built-in microwave antenna is necessary for such systems. This paper presents the design of an aperture coupled modified cross-slot microstrip patch antenna with four new slots generating a circular polarization and using a microstrip substrate produced by plane type printing technology which meets such a demand. The antenna is characterized by small size, light weight, and multifunctional operation. As a result, a return loss of -40 dB at the center frequency 5.84 GHz was obtained by simulation of the ISM band with an operation frequency 5.8 GHz and a return loss of -37 dB at 5.79 GHz by actual measurement, suggesting that the match between the feeding line and radiation patch is better than the existing aperture coupled cross slot microstrip antenna, and the axial ratio is also good.

A Broadband Monopole Antenna with Ring Loop By Modified Ground Plane

Abstract - In this paper, a wideband monopole antenna with ring loop by modified ground plane is presented. The proposed antenna consist of monopole antenna, ring loop by ground plane. This antenna is fed CPW-fed and wide slot antenna of a novel structure for broadband characteristics is proposed. To enhance the impedance bandwidth of the wide slot antenna, we proposed the wide slot structure with CPW-fed which is combined with four λ /2 rectangular radiation modified monopole and inductively coupled. The measured impedance bandwidth is about 2.5 GHz(3.65∼6.15 GHz) then less -10 dB.Key Words : Monopole antenna, Ring loop, Wide slot, CPW-fed†교신저자, 정회원 : 동강대학교 전기전자과 교수 E-mail : hyeonjin@dkc.ac.kr*정 회 원 : 광주보건대학교 안경광학과 접수일자 : 2012년 7월 12일 최종완료 : 2012년 7월 30일 1. 서 론 무선통신 기술의 발전은 음성 및 멀티미디어 송수신 통신이 가능한 다중, 광대역 통신으로 동작 주파수의 대역이 날로 넓어지고 다중대역화 되고 있다. 따라서 양질의 서비스를 제공하기 위해서는 통신 장비의 핵심부품인 안테나의 설계 및 개발이 중요한 요소라 할 수 있다. 개인 휴대 단말기의 소형화와 집적화에 따라 안테나 역시 소형, 경량, 다기능 특성 및 대량생산이 요구되고 있다[1,2]. 이를 충족하는 안테나가 인쇄형 마이크로스트립 패치 안테나이며, 마이크로스트립 패치안테나는 제작이 용이하고, 인쇄회로(printed circuit)기술에 의한 대량생산이 가능하므로 위성통신 및 이동 통신용에 적합한 안테나이다 [3,4]. 그러나 한편으로 마이크로 스트립안테나는 대역폭이 협소한 단점이 있기 때문에 대역폭을 확장하고자하는 연구가 활발하게 진행 중에 있다 [5,6]. 일반적으로 마이크로스트립 안테나의 대역폭 확장방법으로 낮은 유전율, 두께가 두꺼운 기판을 사용하는 방법, 기생패치 및 적층구조에 의한 방법 등이 일반적으로 이용되고 있다. 본 논문에서는 단일 면에 안테나부와 급전부를 동시에 수용할 수 있는 CPW(Coplanar waveguide)급전 방식에 의한 모노폴 방사체와 접지면을 변형시킨 원형 루프구조로 이루어져있다. 또한 접지면을 변형하여 전기적인 공진 길이를 증가시켜 공진 주파수대역을 확대하고자 하였다. CPW 급전구조 방식은 마이크로 스트립 선로에 비해 분산이 적고, 광대역 특성을 얻을 수 있으며 접지 면과 동일면에 급전 구조를 구현함으로써 급전 손실을 줄일 수 있다 [7]. 제안된 안테나는 단일 평면 구조로 설계가 단순하며 제작 과정이 평판회로 공정 기법을 통해 이루어지므로 제작의 용이성 및 정확성을 기할 수 있으며 제작비용이 매우 저렴하다. CPW 슬롯 안테나를 급전하는 일반적인 방법은 급전선로를 슬롯의 중앙으로 급전하는 방법이다 [8]. 이 급전방법은 매우 높은 방사저항을 갖은 문제점이 있어 이를 해결하기 위한 급전방법들이 연구 되고 있다 [9]. 그러나 슬롯 폭이 좁은 경우에 한하여 좋은 정합을 이룰 수 있지만 슬롯 폭이 넓어지면 방사 저항도 슬롯 폭에 비례적으로 증가하여 우수한 정합을 하기 어려운 문제가 있다. 슬롯 폭이 넓은 안테나에 대한 연구가 지속적으로 이루어졌으나 슬롯 폭이 증가하면 대역 폭 이 넓어질 수 있다는 가능성만 확인했을 뿐 더 넓은 대역폭을 얻지 못했다 [10]. 본 연구에서는 이러한 문제점을 해결할 수 있는 방법으로 링-형태( ring-type)의 변형된 모노폴구조의 마이크로 스트립 선로를 사용하여 넓은 공진 주파수대역에서 방사저항의 변화를 구형(rectangular) 슬롯 형태와 비교할 때 더욱 일정하게 유지할 수 있는 광대역 슬롯안테나 설계의 최적화를 하였다. 링-형태의 루프를 갖은 CPW 슬롯안테나에서 대역폭과 정합에 가장 큰 영향을 주는 설계변수는 모노폴 안테나의 길이 (fl) 및 모노폴의 폭 (fw)의 변화이고, 특성 임피던스 매칭을 위하여 간격(gap)값을 조절하여 최적화 하였다.