Biao Li

Wideband Dual-Polarized Patch Antenna With Low Cross Polarization and High Isolation

A coax-feed wideband dual-polarized patch antenna with low cross polarization and high port isolation is presented in this letter. The proposed antenna contains two pairs of T-shaped slots on the two bowtie-shaped patches separately. This structure changes the path of the current and keeps the cross polarization under -40 dB. By introducing two short pins, the isolation between the two ports remains more than 38 dB in the whole bandwidth with the front-to-back ratio better than 19 dB. Moreover, the proposed antenna achieving a 10-dB return loss bandwidth of 1.70-2.73 GHz has a compact structure, thus making it easy to be extended to form an array, which can be used as a base station antenna for PCS, UMTS, and WLAN/WiMAX applications.

Design of a Multiband Quasi-Yagi-Type Antenna With CPW-to-CPS Transition

A novel coplanar waveguide-fed planar quasi-Yagi antenna for multiband operation is presented in this letter. The antenna consists of a basic quasi-Yagi element and a coplanar-waveguide-to-coplanar-strip (CPW-to-CPS) transition, which can excite the odd-mode electric fields at the CPS line though the CPW feed line. The proposed antenna can be used in multiband operation with directional radiation patterns whose front-to-back ratios approximate to 10 dB for desired bands. Its impedance bandwidth, determined by -10-dB reflection coefficient, covers numbers of present wireless communication systems, and the antenna can be simply integrated with other circuit components for its planar structure. Experimental data obtained from a laboratory prototype are also presented. The experimental results confirm the good performances observed by the electromagnetic simulations.

A WIDEBAND AND DUAL-RESONANT TERAHERTZ METAMATERIAL USING A MODIFIED SRR STRUCTURE

We present the desgin, fabrication and measurment of a dual-resonant broadband terahertz (THz) matamterial based on a modifled split-ring resonator (MSRR) structure. The proposed MSRR is constructed by connecting the inner split ring with the outer split ring of adjacent cell. Transmission and re∞ection characteristics of the proposed structure are simulated using Ansoft HFSS, and the permittivities show negative values in 0.492{0.693THz and 0.727{ 0.811THz bands. The designed sample is fabricated on a gallium arsenide layer, and experiments are performed in Terahertz Time- Domain Spectroscopy. Measured transmission characteristics agree well with the simulations.

Low-profile dual-polarized patch antenna with HIS reflector for base station application

A coax-feed low-profile dual-polarized patch antenna with high impedance surface (HIS) reflector is presented. The proposed antenna contains two pairs of narrow slots along the diagonals and two pairs of T-shaped slots along the centerlines, which keep the cross-polarization under −38 dB. By introducing two short pins, the isolation between the two ports remains more than 36 dB in the whole bandwidth. Low profile and high front–back ratio characteristics are achieved by using the HIS reflector, which is also applied to enhance the performance of two-element array. The height of the antenna is less than λ/8 and the front–back ratio is better than 35 dB. The mutual coupling lower than −31 dB is obtained for the array design with the patches placed 0.8λ apart. The proposed antenna which covers a −10-dB reflection coefficient bandwidth of 2.28–2.75 GHz can be used as the low-profile base station antenna for WiMAX and LTE applications.

A Novel Dual-Band Circularly Polarized Rectangular Slot Antenna

A coplanar waveguide fed dual-band circularly polarized rectangular slot antenna is presented. The proposed antenna consists of a rectangular metal frame acting as a ground and an S-shaped monopole as a radiator. The spatial distribution of the surface current density is employed to demonstrate that the circular polarization is generated by the S-shaped monopole which controls the path of the surface currents. An antenna prototype, having overall dimension 37 × 37 × 1 mm3, has been fabricated on FR4 substrate with dielectric constant 4.4. The proposed antenna achieves 10 dB return loss bandwidths and 3 dB axial ratio (AR) in the frequency bands 2.39–2.81 GHz and 5.42–5.92 GHz, respectively. Both these characteristics are suitable for WLAN and WiMAX applications.

A CPW-fed triple-band antenna with a Π-shaped slot for WLAN and WiMAX applications

A novel coplanar waveguide-fed triple-band antenna with omni directional radiation patters in the azimuth plane is proposed. The proposed antenna consists of a rectangular patch monopole with a Π-shaped slot. It can provide three separate impedance bandwidths of 27%, range from 2.22 to 2.89GHz; bandwidth of 15%, range from 3.18 to 3.71GHz; and bandwidths of 22%, range from 5.09 to 6.33GHz, respectively, covering all the 2.4/5.2/5.8GHz WLAN bands and 2.5/3.5/5.5GHz WiMAX bands.

A Symmetrical Dual-Band Terahertz Metamaterial with Cruciform and Square Loops

A symmetrical terahertz metamaterial for dual-band operation is designed and fabricated. The proposed metamaterial is composed of periodically arranged cruciform and square metal loops. Due to the symmetrical structure, this metamaterial is insensitive with the polarization of the incident wave. Transmission and re∞ection characteristics of the proposed structure are simulated using Ansoft HFSS, and the negative permittivity is flgured out in 378{500GHz and 626{677GHz bands. The designed sample is fabricated on a gallium arsenide layer, and experiments are performed in Terahertz Time-Domain Spectroscopy. The experimental results agree well with the simulations.

Design of a narrow-size planar monopole multiband antenna with double L-shaped slots

A narrow-size planar monopole antenna for triple-band operation is presented. The proposed antenna consists of a half E-shaped metal patch, a 50 ohm coplanar waveguide (CPW) transmission line and a branch extended from the ground. The narrowness of the antenna is achieved by applying the asymmetric coplanar strip (ACS) structure to the prototype one. The multiband characteristic of the antenna is due to the various meandered current paths excited in the different parts of radiation structure. There are double L-shaped slots within the antenna, one in the ground and the other in the E-shaped patch. By etching the slots, band-rejected filtering properties outside the PCS/WiMax/ WLAN bands are achieved. This technique is suitable for reducing the size meanwhile maintaining the main characteristic of antennas.