Wei-Jun Wu

A New Compact Filter-Antenna for Modern Wireless Communication Systems

Design, fabrication, and measurement of a new compact filter-antenna for modern wireless communication systems are presented in this letter. Two microstrip square open-loop resonators, a coupled line, and a Γ-shaped antenna are used and integrated to be a filter-antenna. The Γ-shaped antenna is excited by a coupled line that is treated as the admittance inverter in filter design. The Γ-shaped antenna performs not only a radiator, but also the last resonator of the bandpass filter. Therefore, near-zero transition loss is achieved between the filter and the antenna. The design procedure follows the circuit approach-synthesis of bandpass filters. Measured results show that the filter-antenna achieves an impedance bandwidth of 16.3% (over 2.26-2.66 GHz) at a reflection coefficient |S11 | <; - 10 dB and has a gain of 2.41 dBi.

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 Wideband Dual-Sleeve Monopole Antenna for Indoor Base Station Application

The design and enhanced bandwidth performance of a dual-sleeve monopole antenna for indoor base station application is presented. By a top-loading circular patch shorted to the ground plane through four shorting probes, the size reduction is achieved. The dual-sleeve structure is successfully employed to improve the impedance bandwidths through achieving another two resonant modes. A measured impedance bandwidth for VSWR ≤ 2 of about 137% ranging from 730 to 3880 MHz is achieved. It is very suitable for GSM900, DCS1800, PCS1900, UMTS, IMT2000, WiBro, WiMAX2350/3500, and wireless LAN (IEEE 802.11b).

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.

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.

A Wideband Stacked Shorted Antenna for Miniaturized Active RFID Tags

A novel and simple antenna applicable to active RFID tags is designed. The designed antenna has been skillfully integrated with the active RFID tag circuit. The antenna consists of two parts. One part comprises stacked shorted patches and a ground plane. The other one is an active tag circuit mounted on the bottom of the antenna. By using the offset shorting posts technique, the proposed antenna can achieve an enhanced operating bandwidth with a small size. The measurement results reveal that the antenna has return loss less than −10 dB within the bandwidth of 42 MHz (from 914 MHz to 956MHz), which totally covers the 5 MHz bandwidth from 920 MHz to 925MHz (The band is also allowed for passive RFID) requirement for active RFID in China.

Wideband dual-polarized crossed bowtie dipole antenna with shorted stubs for base station applications

A wideband dual-polarized crossed-dipole antenna with shorted stubs for base station applications is presented. By using a pair of orthogonal crossed-dipole, two linear polarizations (± 45 ◦ ) are obtained. The shorted subs are introduced to improve the impendence bandwidth and enhance the isolation (S12) between the two orthogonal polarizations. The antenna shows a wideband impedance characteristics of about 29.4% for S11 −10 dB (+45 ◦ polarization) and S22 −10 dB (−45 ◦ polarization). High isolation (S12 −32 dB) between the two polarizations in the required band is obtained, which the lowest isolation is only −56 dB at about 1.8 GHz. The stable peak gain, unidirectional radiation patterns, low cross-polarization and high front-to-back ratio over the whole operating band are also achieved. Due to its good performance, the antenna is very suitable for potential base station applications in mobile communication such as DCS, PCS and UMTS.