Zi-Bin Weng

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].

CPW-Fed Broadband Circularly Polarized Planar Monopole Antenna With Improved Ground-Plane Structure

A novel CPW-fed planar printed monopole antenna with broadband circular polarization (CP) characteristic is presented. The proposed antenna consists of a rectangle patch and an improved ground-plane. By appropriately adding a vertical stub and cutting a horizontal slit on the ground-plane, the impedance bandwidth of the antenna is enlarged, and its wide axial-ratio (AR) bandwidth is achieved. The measured results show that the proposed antenna has not only a broad 3-dB AR bandwidth of 44.9% (2.65 GHz, 4.58-7.23 GHz) with respect to the CP center frequency 5.90 GHz, but also a wide 10-dB return loss bandwidth of 76.9% (4.35 GHz, 3.48-7.83 GHz) centered at 5.66 GHz.

DESIGN AND EXPERIMENT OF ONE DIMENSION AND TWO DIMENSION METAMATERIAL STRUCTURES FOR DIRECTIVE EMISSION

A new method to improve the gain of monopole and patch antenna with one dimension and two dimension metamaterial structures is presented. The analytical permittivity models of metamaterial are derived using the transmission line method. Then the monopole and patch antenna with the metamaterial are fabricated and measured. The experimental results show that this method is effective and these structures can realize congregating the radiation energy, thus the gain of these antennas with metamaterial increase greatly compared with the conventional ones.

Study on High Gain Patch Antenna with Metamaterial Cover

A new method to improve the gain of patch antenna with metamaterial composed of ring aperture lattice is presented. A comparison between the conventional patch antenna and the new metamaterial patch antenna is given. The experimental results show that this method is effective and metamaterial structure can realize congregating the radiation energy, so the gain of the antenna with metamaterial can greatly increase compared with the conventional one.

Dual-Polarized Dielectric Resonator Antenna with High Isolation Using Hybrid Feeding Mechanism for WLAN Applications

A dual-feed dual-polarized dielectric resonator antenna (DRA) with high isolation is proposed in this paper. The high isolation is achieved by using two hybrid feeding mechanism: one port having an H-shaped aperture coupled feed and the other with two out-of- phase probe feeds. The antenna is designed to operate at around 5.2GHz for WLAN (Wireless Local Area Network) applications and experimental results show that it has more than 35dB isolation over the entire impedance bandwidth. Good symmetric broadside radiation patterns with low cross polarizations are observed in the two principal planes, and in addition, the front-to-back (F/B) ratios for Port 1 and Port 2 are 10 and 18dB, respectively.

A Directive Patch Antenna with Arbitrary Ring Aperture Lattice Metamaterial Structure

A new method to improve the gain of patch antenna with metamaterial composed of ring aperture lattice spaced periodically along two arbitrary vectors is presented. The properties of the metamaterial are discussed, and the effective index of refraction and effective permittivity can be retrieved at all frequencies. Then a patch antenna with metamaterial is fabricated and measured. The experimental results show that this method is effective and this structure can realize congregating the radiation energy, thus the gains of the patch antenna with metamaterial can be greatly increased compared with the conventional one.

Wideband Rectangular Dielectric Resonator Antenna (DRA) with Slot-Fed Design

A novel wideband rectangular dielectric resonator antenna (DRA) is proposed in this paper. A hybrid structure with an isolated dielectric resonator (DR) and an equivalent air-dielectric DR is introduced by lifting the resonator from the ground plane. The hybrid structure is excited by a slot-fed mechanism to obtain a smooth transition between each resonant mode. The resonant modes of the isolated DR and the equivalent DR are merged together to form a wideband impedance bandwidth. It is found that the bandwidth of the proposed antenna can be greatly enhanced by using the hybrid DRA structure instead of the case mounted on the ground plane. A detailed parametric study is carried out to analyze the characteristics of the proposed antenna. Measured results show that the proposed DRA has a 10dB impedance bandwidth of 61% from 2.4GHz to 4.5GHz and the radiation pattern is stable through the operating frequency.

A Broadband CPW-FED Slot Antenna for IMT-2000, WIMAX and WLAN Applications

In this paper, a broadband CPW-fed slot antenna with a gradual-changed ground plane for bandwidth enhancement is proposed and experimentally studied. The effect of various shapes of the slot on broadband operation is investigated. From the experimental results, the measured impedance bandwidth, defined by 10 dB return loss, could be as large as 3.75 GHz or about 105% centered at about 3.56 GHz. The antenna radiation patterns within the operation band were also measured and studied.

Design and Experiment on Substrate Integrated Waveguide Resonant Slot Array Antenna at Ku-Band

By transferring the conventional waveguide resonant slot array antenna to the substrate integrated waveguide (SIW) structure, The resonant slot array antenna can take the advantages of the SIW such as small size, low profile, low cost. The whole antenna is fabricated on a single substrate, the design process and experimental results of a five-slot SIW array antenna at Ku-band are presented.