Shufeng Zheng

A Compact CPW-Fed Monopole Antenna with a U-Shaped Strip and a Pair of L-Slits Ground for WLAN and WiMAX Applications

A compact tri-band planar monopole antenna suitable for 2.4/5.2/5.8GHz WLAN and 3.5GHz WiMAX is presented. The antenna employs a U-shaped parasitic strip and a defect ground-plane structure. By inserting a U-shaped strip as a parasitic strip into a normal monopole which operates at lower band of the WLAN, one more resonance at the higher WLAN band comes out. A defect ground-plane composed of two symmetrical L-shaped slits leads to another resonance operating at WiMAX band. The proposed antenna has a compact size of 22 £ 41 £ 0:8mm 3 and ofiers good radiation and re∞ection characteristics in the above frequency bands. The measured VSWR exhibits a good agreement with the simulated one. Detailed design steps, parametric studies and experimental results for the antenna are investigated in this paper.

DUAL-WIDEBAND SYMMETRICAL G-SHAPED SLOTTED MONOPOLE ANTENNA FOR WLAN/WIMAX APPLICATIONS

A novel dual-wideband printed monopole antenna is proposed for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The proposed antenna consists of a T-shaped monopole on top and dual combined G-shaped slots etched symmetrically on the ground plane to achieve a dual-wideband performance. Prototype of the proposed antenna has been constructed and tested. The measured 10dB bandwidths for return loss are 1.76GHz from 2.13 to 3.89GHz and 0.92GHz from 5.03 to 5.95GHz, covering all the 2.4/5.2/5.8GHz WLAN and 2.5/3.5/5.5GHz WiMAX bands. And this antenna also has omni-directional patterns over the lower operating range.

Double Screen FSSs with Multi-Resonant Elements for Multiband, Broadband Applications

Design investigations are presented for double screen frequency selective surfaces (DSFSSs) with multi-resonant elements. The DSFSS is composed of two identical single layer frequency selective surfaces (FSSs) separated by a foam layer. By tuning the thickness of the foam, a four-band FSS with improved S-band performance and a dual-band band-stop FSS with broad bandwidths and rapid rolloffs are designed. Both designs are angle and polarization insensitive. The Fabry-Perot interferometer (FPI) theory demonstrates that DSFSSs with a large distance between the metallic arrays are not suitable for broadband band-stop applications due to the interruptions of undesired transmission peaks, which are the results of array interference. An equivalent circuit model is developed to give an insight into the response of the DSFSS. Experimental verifications are carried out. The calculated results agree well with the measured ones.

Single-Feed Circularly Polarized Annular Slot Antenna for Dual-Broadband Operation

A novel dual-broadband circularly polarized folded slot antenna with single-feed is presented. The proposed antenna consists of two folded annular slots. By adjusting the asymmetric widths of the two slots, circularly polarized radiation can be achieved in two difierent bands. By optimizing the parameters of the proposed antenna, two wide impedance bandwidths of 35.0% (1.91{2.72GHz) and 46.5% (4.36{7.00GHz) can be obtained, and two axial ratio bandwidths are 2.36{2.56GHz and 5.68{6.04GHz, respectively. The antenna with simple structure is fabricated and measured. Good agreement between the simulated and measured results is also achieved.

A Simple Low-Cost Shared-Aperture Dual-Band Dual-Polarized High-Gain Antenna for Synthetic Aperture Radars

This paper presents a novel shared-aperture dual-band dual-polarized (DBDP) high-gain antenna for potential applications in synthetic aperture radars (SARs). To reduce the complexity of SAR antennae, a DBDP high-gain antenna based on the concept of Fabry-Perot resonant cavity is designed. This antenna operates in both Cand X-bands with a frequency ratio of 1:1.8. To form two separate resonant cavities, two frequency selective surface layers are employed, leading to high flexibility in choosing desired frequencies for each band. The beam-scanning capability of this proposed antenna is also investigated, where a beam-scanning angle range of ±15° is achieved in two orthogonal polarizations. To verify this design concept, three passive antenna prototypes were designed, fabricated, and measured. One prototype has broadside radiation patterns, while the other two prototypes have frozen beam scanned to +15°. The measured results agree well with the simulated ones, showing that the high gain, high port isolation, and low cross-polarization levels are obtained in both the bands. Compared with the conventional high-gain DBDP SAR antennae, the proposed antenna has achieved a significant reduction in the complexity, mass, size, loss, and cost of the feed network.

DESIGN OF A NOVEL WIDEBAND LOOP ANTENNA WITH PARASITIC RESONATORS

A novel coax-fed wideband loop antenna loaded with rectangular patches and U-shaped elements is presented and studied. By inserting a pair of rectangular patches inside the strip loops and employing a pair of U-shaped elements as the parasitic resonators, two additional resonances are excited and a good performance of bandwidth enhancement can be obtained. The measured results indicate that the impedance bandwidth (VSWR•2) is about 87.1% from 1.58 to 4.02GHz, which covers the required operating bands of DCS1800 (1710{1880MHz), PCS1900 (1850{1990MHz), UMTS2100 (1920{ 2170MHz), WLAN2400 (2400{2484MHz), LTE2300/2500 (2300{ 2690MHz) and WiMAX3500 (3300{3690MHz). In addition, good radiation characteristics such as symmetrical radiation pattern, moderate peak gain, low back radiation, and low cross-polarization are observed over the entire operating band.

Interdigitated hexagon loop unit cells for wideband miniaturized frequency selective surfaces

A single layer band-pass FSS with very small periodicity and superior bandwidth which is composed of interdigitated hexagon loop aperture unit cells is proposed in this paper. By interdigitating the unit cells at the common boundary of adjacent unit cells of FSSs, the extent of miniaturization and operating bandwidth can be significantly improved compared with convoluted ones. Simulated results shows that the merit λ1/p characterizing the extent of miniaturization is 31.4, moreover, the fractional bandwidth reaches 22.8% at normal incidence.

A conical four-arm sinuous antenna

A conical four-arm sinuous antenna with unidirectional radiation is presented. The proposed antenna consists of four sinuous metal arms printed on a conical dielectric substrate, an auxiliary feeding patch, and two modified exponentially-tapered baluns. The simulated results of active VSWR, realized gain and axial ratio in broadside direction reveal that the antenna can effectively radiate left-handed and right-handed circularly-polarized waves at frequencies ranging from 0.82-3GHz.

A Meta-Surface Antenna Array Decoupling (MAAD) Method for Mutual Coupling Reduction in a MIMO Antenna System

In this paper, a method to reduce the inevitable mutual coupling between antennas in an extremely closely spaced two-element MIMO antenna array is proposed. A suspended meta-surface composed periodic square split ring resonators (SRRs) is placed above the antenna array for decoupling. The meta-surface is equivalent to a negative permeability medium, along which wave propagation is rejected. By properly designing the rejection frequency band of the SRR unit, the mutual coupling between the antenna elements in the MIMO antenna system can be significantly reduced. Two prototypes of microstrip antenna arrays at 5.8 GHz band with and without the metasurface have been fabricated and measured. The matching bandwidths of antennas with reflection coefficient smaller than −15 dB for the arrays without and with the metasurface are 360 MHz and 900 MHz respectively. Using the meta-surface, the isolation between elements is increased from around 8 dB to more than 27 dB within the band of interest. Meanwhile, the total efficiency and peak gain of each element, the envelope correlation coefficient (ECC) between the two elements are also improved by considerable amounts. All the results demonstrate that the proposed method is very efficient for enhancing the performance of MIMO antenna arrays.

A Broadband Dual Circularly Polarized Conical Four-Arm Sinuous Antenna

A novel wideband four-arm sinuous antenna with dual circular polarizations (CPs) and unidirectional radiation is proposed. Different from the conventional designs, this sinuous antenna is realized in a conical form and no ground plane or absorptive cavity is required to obtain unidirectional radiation. The beamforming network for dual circularly polarized operations consists of a wideband quadrature coupler and two wideband baluns, and an auxiliary feeding patch is introduced to facilitate the connection between baluns and sinuous arms. The design of baluns and coupler is inspired from the printed exponentially tapered microstrip balun and broadside-coupled microstrip coupler, respectively. The dynamic differential evolution algorithm is employed to optimize the geometry of coupler for optimal performance. For both polarizations, the presented antenna has wide impedance bandwidth, good axial ratio, moderate realized gain, and front-to-back ratio within 2–5 GHz. An antenna prototype is fabricated and tested. The agreement between simulation and measurement results validates the proposed antenna framework. The demonstrated antenna has advantages of wide bandwidth, dual CPs, unidirectional radiation, lightweight, and low cost, and is promising for applications in wireless systems.