Fu-Shun Zhang

Multiband CPW-Fed Triangle-Shaped Monopole Antenna for Wireless Applications

A multiband CPW-fed triangle-shaped monopole antenna for wireless applications covering 2.4and 5 GHz WLAN bands and 3.4 GHz WIMAX band in IEEE 802.16 is proposed. Prototype of the proposed antenna have been constructed and tested. The experimental results show that the antenna can provide two separate impedance bandwidths of 140 MHz (about 5.8% centered at 2.43 GHz) and 3100 MHz (about 61.4% centered at 4.91 GHz), which meet the required bandwidths specification of 2.4/5 GHz WLAN and 3.4 GHz WIMAX standard. Good omnidirectional radiation in the desired frequency bands has been achieved. The proposed antenna with relatively low profile is suitable for multiband wireless applications.

COMPACT RING MONOPOLE ANTENNA WITH DOUBLE MEANDER LINES FOR 2.4/5 GHZ DUAL-BAND OPERATION

A novel compact ring monopole antenna with double meander lines is proposed for wireless local area networks (WLAN) applications in IEEE 802.11b/g/a systems. The designed antenna, fed by a 50 Ω microstrip transmission line, is only 32 mm in height and 16 mm in width. By introducing a horizontal and a vertical branched strips to a closed rectangular strip ring, the proposed antenna can generate two separate impedance bandwidths. Prototypes of the proposed antenna have been constructed and tested. The obtained impedance bandwidths reach about 12% for the 2.4 GHz band and 45.3% for the 5 GHz band, which meet the required bandwidth specification of 2.4/5 GHz WLAN standard. Also, good radiation performance and antenna gain over the two frequency ranges have been obtained.

LOWPASS FILTER DESIGN OF HILBERT CURVE RING DEFECTED GROUND STRUCTURE

LOWPASSFILTERDESIGNOFHILBERTCURVERINGDEFECTEDGROUNDSTRUCTUREJ.Chen,Z.-B.Weng,Y.-C.Jiao,andF.-S.ZhangNational Key Laboratory of Antennas and Microwave TechnologyXidian UniversityXi’an 710071,ChinaAbstract—In this paper,a novel Hilbert curve ring (HCR) fractaldefected ground structure (DGS) and its equivalent circuit areinvestigated. Furthermore,an improved HCR DGS cell model withopen stubs loaded on the conductor line is then presented to improvethe out-band suppression. By employing three cascaded improvedHCR DGS cells,an L-band microstrip low-pass is designed andfabricated. This lowpass filter achieves a quite steep rejection property;a low in-band insertion loss of below 0.5dB and a high out-bandsuppression of more than 33dB.1. INTRODUCTIONRecently,there has been an increasing interest in the applicationsof defected ground structure (DGS) in microwave and millimeter-wave applications [1–3]. The DGS of the microstrip line employsan intentional defect on the ground and it provides band rejectioncharacteristic from the resonance property. The applications of theDGS are developed in divider,filter,and amplifier circuits. Thedefect of the conventional DGS is with the dumbbell shape or therectangle shape,these conventional DGSs,however,have a flat slopeof their rejection characteristic. To fabricate a lowpass filter with steeprejection property,many these DGSs are needed to be cascaded,whichalso means higher in-band insertion and larger size.Different from Euclidean geometries,fractal geometries have twocommon properties,space-filling and self-similarity. It has been shownthat the self-similarity property of fractal shapes can be successfullyapplied to the design of multi-band fractal antennas,such as theSierpinski gasket antenna [4],while the space-filling property of fractalscan be utilized to reduce antenna size [5,6].

A Miniaturized Antipodal Vivaldi Antenna With Improved Radiation Characteristics

In this letter, a modified antipodal Vivaldi antenna is presented. A novel tapered slot edge (TSE) structure is employed in this design. The proposed TSE has the capacity to extend the low-end bandwidth limitation and improve the radiation characteristics in the lower frequencies. A prototype of the modified antenna is fabricated and experimentally studied as well. The measured results show reasonable agreement with the simulated ones that validate the design procedure and confirm the benefits of the modification.

A Subwavelength Element for Broadband Circularly Polarized Reflectarrays

A subwavelength element is presented for designing a circularly polarized (CP) reflectarray that converts the linearly polarized incident field of the feed into an outgoing circularly polarized field. To evaluate the performance of the designed element, a parametric study is carried out using Ansoft HFSS. Compared to the conventional near-resonant patch, the subwavelength one can realize a more similar behavior for the phase curves at different frequencies, leading to broader bandwidth. The phase shifts for both linear polarizations can be controlled by varying the x- and y-dimension of the element. A prime-focus reflectarray with this type of element has been designed and implemented, and a superior bandwidth performance has been verified, compared to a reflectarray with conventional ¿/2 elements. The measured results show that the obtained 1-dB gain and 3-dB axial ratio bandwidths of the reflectarray with subwavelength elements can reach as large as 17% and 11%, respectively.

A Three-Fed Microstrip Antenna for Wideband Circular Polarization

New design of a circular microstrip antenna with three feeds for wideband circular polarization is presented. Detailed theoretical analysis proves that a circular microstrip antenna, which is excited by three central symmetrical feeds with equal amplitudes and relative 120° phase shifts, can obtain good circular polarization characteristic. A broadband 120° phase shifter is developed using the metamaterial transmission line (MM TL). It consists of a Wilkinson power divider and three phase-adjusting TLs, namely a MM TL and two microstrips. The antenna is composed of two circular patches. The primary radiating patch under the parasitic patch is excited by three feeds. The proposed antenna can provide an impedance bandwidth of 54.75% and a 3-dB axial ratio bandwidth of 47.88%. The 3-dB gain bandwidth is as large as 40%, with the peak gain 8.8 dBic. In addition, the measured and simulated symmetrical radiation patterns are in good agreement.

Design of Novel Wideband Monopole Antenna with a Tunable Notched-Band for 2.4 GHz WLAN and UWB Applications

In this article, a novel wideband planar monopole antenna for applications in 2.4GHz WLAN and UWB bands is presented and investigated. The proposed antenna is composed of a gourd-like radiation element fed by a 50Ohm microstrip line and a step-shaped ground plane. A pair of slot lines is etched symmetrically on the ground plane to obtain the 5GHz band-notched characteristic, and the notched band can be tuned. The proposed antenna is successfully simulated, designed, and measured. The measured results agree reasonably with the simulated ones. According to the measured results, the proposed antenna yields a wide bandwidth ranging from 2.2 to 11GHz for VSWR less than 2, except the notched band of 5.1{6.2GHz for 5GHz WLAN. Moreover, it exhibits nearly omnidirectional radiation patterns, stable gain, and small group delay variation across the operation band, which meets the requirements of 2.4GHz WLAN and UWB applications.

A Multi-Band Monopole Antenna with Two Different Slots for WLAN and WiMAX Applications

A compact triple-band monopole antenna with two difierent slots for WLAN and WiMAX applications is proposed and experimentally studied. The proposed antenna with a size of 30mm £ 25mm £ 1mm is excited by a 50› microstrip feed line. The designed antenna obtains three frequency bands through loading an inverted E-shaped slot and an inverted C-shaped slot which incise the surface current and change the path of the current on the rectangle patch. The obtained results show that the designed antenna has impedance bandwidths of 2.4GHz, 5.8GHz for WLAN and 3.5GHz for WiMAX. The return loss, radiation patterns and peak antenna gains are presented using computer simulations and measurements.

An Effective Analysis Method for EBG Reducing Patch Antenna Coupling

This paper presents an efiective analysis method for EBG reducing patch antenna coupling. A couple of coaxial probes are used to analyze the mutual coupling reduction range of patch antenna arrays loaded with EBG in this method. Conventional FDTD/PBC algorithm for EBG structures is appropriate only in inflnite ground plane and substrate. The gained frequency band-gap by using the algorithm can not be directly used in flnite ground plane because of the edge efiects. While the proposed coaxial probe method is valid not only in inflnite ground plane and substrate, but also for flnite ground plane. The method is more suitable for real environments. In order to validate the described method, a two-element microstrip patch antenna array is fabricated and measured. The experimental results are in good agreement with the theoretical data obtained by using the proposed method.

COMPACT TRIPLE-FREQUENCY SLOT ANTENNA FOR WLAN/WIMAX OPERATIONS

A novel microstrip-fed slot antenna with triple-band operation in compact size is proposed. The proposed antenna structure consists of a L-shaped microstrip feed line and open-ended slot on the ground plane, having small overall size of 14 £ 34mm 2 . The open- ended slot constructed of crossed double T-shaped slots is aimed to obtain resonant modes at 2.4/3.5GHz. Meanwhile, with the use of a via-loaded metal patch connected to the edge of ground, the upper resonant frequency point at 5.8GHz is achieved. The numerical and experimental results exhibit the designed antenna operates over triple frequency ranges, fulfllling the standards of 3.5-GHz WiMAX and 2.4/5.8-GHz WLAN. In addition, acceptable radiation characteristic is obtained over the operating bands.