Zhi-Ya Zhang

EIGENMODE DECOUPLING FOR MIMO LOOP-ANTENNA BASED ON 180 - COUPLER

A low-cost, high isolation, printed loop-antenna system for multiple-input multiple-output (MIMO) applications in the 2.4GHz WLAN band is presented. By feeding the orthogonal eigenmodes of the array, port decoupling (S21 < i20dB) with tightly coupled elements (only 0:07‚ separation) is obtained. The orthogonal eigenmodes are realized based on 180 - coupler. Then decoupled external ports of the feed network may be matched independently by using conventional matching circuits. With this low-cost and high isolation characteristic, it is very suitable for being embedded inside a wireless access point (AP).

INVESTIGATIONS OF REDUCTION OF MUTUAL COUPLING BETWEEN TWO PLANAR MONOPOLES USING TWO λ/4 SLOTS

This article presents a simple structure for reducing mutual coupling between two diversity planar monopole antennas for WLAN 5.2/5.8GHz applications. The structure has two ‚=4 (‚- wavelength in the substrate) slots cut into the ground plane between the two monopoles. In 0.5‚o (‚o-wavelength in the air) of the antenna spacing, mutual coupling was i33:3, i21:1dB at 5.2, 5.8GHz, respectively. The lowest mutual coupling of i33:3dB was achieved at 5.2GHz, which are 20.8dB improvements over the reference.

A Miniaturized Broadband 4 : 1 Unequal Wilkinson Power Divider

This paper presents the design of a miniaturized unequal 4 : 1 Wilkinson power divider operated across a broadband 1 to 11 GHz, which has a compact size with overall dimensions only of 10 mm × 26 mm. By using a simple defected ground structure (DGS), the microstrip line can be realized with very high impedance of over 150Ω, and consequently a 4 : 1 power dividing ratio can be obtained. Meanwhile, the fabrication problems caused by the very thin conductor microstrip width can be prevented. For verification, the measured results of good dividing ratio, better than 10 dB return loss and better than 15 dB isolation across the whole operating band, are also given.

A SIMPLE FILTERING-ANTENNA WITH COMPACT SIZE FOR WLAN APPLICATION

This paper presents a simple microstrip flltering-antenna with compact size for WLAN application. The T-shape resonator through an inset coupling structure can be treated as the admittance inverter and the equivalent circuit of the flltering-antenna is exactly the same as the bandpass fllter prototype. With a little extra circuit area, the proposed flltering-antenna has almost twice wider bandwidth, good skirt selectivity and high suppression in the stopband compared to the conventional microstrip antenna.

Ultra-Wideband Cavity-Backed Bowtie Antenna for Pattern Improvement

The design and ultra-wideband performance of a cavity- backed bowtie antenna with the parasitic dipole and parasitic circular ring is presented. Besides the elliptical bowtie dipole and the taper feeding microstrip for obtaining ultra-wideband impedance characteristics, the parasitic dipole and parasitic circular ring to efiectively improve the radiation pattern can be used for obtaining the stable broadside unidirectional radiation patterns. An ultra-wideband impedance characteristic of about 118.2% for VSWR • 2 ranging from 2.75{10.7GHz is achieved. A unidirectional radiation pattern, a stable peak gain of around 7.4{10.8dBi and low cross polarization over the whole operating band are also produced. A prototype has been fabricated and tested, and the experimental results validate the design procedure.

Wideband Unidirectional Bowtie Antenna with Pattern Improvement

A wideband unidirectional bowtie antenna with stable radiation patterns is proposed and investigated. It is fed by a wideband microstrip balun, using a coupling triangular structure to induce more balanced currents. Particularly, the corners of the conventional triangular bowtie dipole are rounded to achieve an impedance BW of 106.9% for jS11j • i10dB ranging from 1.97GHz to 6.49GHz. Additionally, a special small circular re∞ector between the ground plane and the bowtie dipole is used to stabilize the radiation patterns. The antenna achieves a stable gain of around 9.5dBi with a little variation of 1.4dBi and unidirectional radiation patterns over the whole operating band.

Printed 6-Element Dipole Array Antenna for Omnidirection Applied in WiMAX

Abstract-A collinear printed 6-element dipole array antenna for WiMAX application is presented. By employing loop-loaded structures, the better omnidirectional coverage is achieved. The array has shown a 7.2% bandwidth (VSWR≤1.5) of center frequency at about 3.5GHz for application in WiMAX. Its performance is relatively stable with 8dBi antenna gain and about ±0.5dBi of the un-roundness on horizontal plane. Design details of the proposed antenna and the results of both simulation and experiment are presented and discussed.

A Planar Meander Monopole Antenna for DVB-H/GSM/DCS Mobile Handsets

A novel planar meander monopole antenna can generate a wide operating band to cover the DVB-H band in the UHF frequency band (470–702 MHz) and mobile communication in the GSM850/900 (824–894 MHz/890–960 MHz) and DCS1800 (1720–1880 MHz) bands. By using the planar monopole type radiating element constructed with meander strips, the antenna provides a degree of miniaturization while retaining a wide impedance bandwidth. A prototype is constructed and tested, which shows that impedance bandwidths of 740 MHz (440–1180 MHz) and 220 MHz (1710–1930 MHz) within 3 : 1 VSWR are achieved. Moreover, it has good omni-directional radiation characteristics within its operation band with gain values larger than 2 dBi.

Printed UWB MIMO Antenna with Different Polarizations and Band-Notch Characteristics

A novel ultra wideband (UWB) multiple-input-multiple-output (MIMO) antenna with difierent polarizations and band-notch characteristics is proposed in this letter. The antenna consists of two monopole antenna radiating elements with gradual change structure, which are placed perpendicularly to each other and printed on each side of the substrate to achieve a wide bandwidth and difierent polarizations. Band-rejected flltering property in the WLAN band is achieved by etching a H-shaped slot and employing a resonant L-shaped strip on two antenna elements. The proposed antenna has a small size of 27£37£1mm 3 with a bandwidth of 128.6% (2.35{10.82GHz). Within the required band, the isolation for the two ports exceeds 18dB. The envelope correlation coe-cient is also measured.

DUAL-WIDEBAND MONOPOLE LOADED WITH SPLIT RING FOR WLAN APPLICATION

This paper presents a novel monopole antenna which uses split ring loading in order to achieve a dual-wideband operation for WLAN (2.4/5.2/5.8GHz) application. By adjusting the split ring position and its natural resonant frequency, the proposed antenna can produce more than 1GHz wideband match in the 5GHz band. According to the measured results, the bandwidth with re∞ection coe-cient less than i10dB is about 715 and 1017MHz in the two bands. Good radiation patterns are also achieved. The dimensions of the monopole loaded with split ring are 27.2mm £ 16.2mm £ 1mm, which is suitable for a hallway antenna or ceiling mount antenna of WLAN application.