Hsien-Wen Liu

Novel CPW-Fed Planar Monopole Antenna for WiMAX/WLAN Applications

A coplanar waveguide (CPW)-fed planar monopole antenna with triple-band operation for WiMAX and WLAN applications is presented. The antenna, which occupies a small size of 25(L) × 25(W) × 0.8(H) mm3, is simply composed of a pentagonal radiating patch with two bent slots. By carefully selecting the positions and lengths of these slots, good dual stopband rejection characteristic of the antenna can be obtained so that three operating bands covering 2.14-2.85, 3.29-4.08, and 5.02-6.09 GHz can be achieved. The measured results also demonstrate that the proposed antenna has good omnidirectional radiation patterns with appreciable gain across the operating bands and is thus suitable to be integrated within the portable devices for WiMAX/WLAN applications.

Compact Monopole Antenna With Band-Notched Characteristic for UWB Applications

A compact planar monopole antenna with standard band-notched characteristic suitable for ultrawideband (UWB) applications is presented. This microstrip-fed antenna, consisting of a square slot patch with a vertical coupling strip, only occupies a small size of 15 (L) × 15 (W) × 1.6 (H) mm3. By properly designing the strip placed at the center of the patch, good frequency rejection performance of the antenna with a wide operating band from 3.05 to 11.15 GHz can be obtained. Compared to other designs, the antenna has a quite simple structure to make the band-notched property to reduce the effect caused by the frequency interference. Furthermore, fairly good omnidirectional radiation patterns and transmission responses both indicate that the proposed antenna is well suited to be integrated within various portable devices for UWB operation.

Folded Dual-Loop Antenna for GSM/DCS/PCS/UMTS Mobile Handset Applications

A folded dual-loop antenna suitable for GSM/DCS/ PCS/UMTS applications is proposed. It is fabricated using a pair of symmetric meander strips to form two loops. By properly bending the radiating strips, the antenna can achieve a compact size of 50 (L) × 9 (W) × 9 (H) mm3 to be integrated within a mobile handset device as an internal antenna. With 6 dB return loss, two operating frequency bands covering 847-971 and 1670-2230 MHz can be obtained with our design. Moreover, the resonant characteristics of the antenna can be tuned by using various strip lengths and also spaces between the radiator and the ground plane. Experimental results exhibit that the proposed folded dual-loop antenna features nearly good omnidirectional radiation patterns with proper gain, so it is well suitable to meet GSM/DCS/PCS/UMTS operations for mobile handset applications.

Compact Inverted-F Antenna With Meander Shorting Strip for Laptop Computer WLAN Applications

In this letter, a novel compact inverted-F antenna with dual-band property for WLAN applications is presented. It comes with a C-shaped radiator and two meander shorting strips, which only occupy a small size of 35 (L)3 (W) mm to be easily embedded inside a laptop computer as an internal antenna. This design can radiate with two operating bands covering 2.38-2.54 and 4.99-5.96 GHz. By properly forming these two shorting strips, the effects due to the antenna near the external casing can be suitably tackled for actual application. Nearly omnidirectional coverage to enhance the communication quality can be obtained with our design. Therefore, the proposed antenna with a compact size is well suitable for WLAN operation in a laptop computer.

Design of Near-Field Edge-Shorted Slot Microstrip Antenna for RFID Handheld Reader Applications

In this letter, a compact edge-shorted slot microstrip antenna with good near-field performance for radio frequency identification (RFID) applications is proposed. It is composed of a rectangular slot radiator, a shorting wall, and a pair of shorting strips, which occupy a small size of 40 (L)×16 (W)×6 (H) mm3 to be easily embedded inside a handheld reader device as an internal antenna. By properly designing a thin slot and a shorting wall, strong and uniform electric field distribution surrounding the near-zone region can be obtained with the antenna. This design can not only achieve an operating band of 2.38-2.55 GHz, but also generate large capacitive coupling effect to significantly enhance the near-field performance for actual application. Experiments exhibit that the proposed patch antenna may well function as a handheld reader antenna to detect the dipole-like tags through capacitive coupling for RFID near-field operation.

Novel Miniature Monopole Tag Antenna for UHF RFID Applications

A novel miniature monopole tag antenna for passive UHF radio frequency identification (RFID) operation is presented. The antenna possesses a two-sided structure that is printed on an FR4 substrate and fed by a 50-¿ microstrip line. By properly using helical strips and vias, the antenna size can be reduced to a small volume of 10 (L) × 9.5 (W) × 0.8 (H) mm3 to be easily integrated within various portable devices. A miniaturized quasi-lumped circuit is also designed to achieve a good impedance matching between the antenna and the tag chip. Experimental results demonstrate that the antenna has a suitable operating band about 914-939 MHz and also nearly omnidirectional radiation patterns with proper gain. Moreover, the proposed compact tag antenna, capable of achieving a maximum readable range about 5.6 m with an effective isotropic radiated power (EIRP) equal to 4 W, is well suitable for RFID applications.

An UHF reader antenna design for near-field RFID Applications

In this paper, two UHF reader antennas based respectively on inductive and capacitive couplings for near-field RFID applications are presented. To identify item-level tags with inductive coupling, a loop-type antenna is developed to have strong magnetic fields in near zone. As for the capacitive coupling, a near-field focusing circular patch array fed by a network with various input phases for radiation elements is proposed to enhance the electric field in near zone. Thus, dipole-like tags can be recognized with the capacitive coupling. Measurements show that those antennas operating with commercial readers provide good performance of tag identifications for near-field RFID applications with inductive and capacitive couplings, respectively.

A metal mounting tag for passive UHF RFID applications

This metal mounting tag is basically a dipole-type antenna on a polypropylene (PP) substrate, a low-loss material with epsivr=2 and tandelta=0.006 at 900 MHz, backed with a ground plane. Thus, we have designed a high efficient tag antenna to be mounted on a metal object or any other object. This metal mounting tag antenna has a high gain, light weight, compact size, and low profile very suitable for RFID applications to tag various objects, particularly on metal surfaces.

A miniature chip antenna without empty space on PCB for 2.4GHz ISM band applications

For 2.4 GHz ISM band applications, such as Bluetooth and WLAN communication systems, an antenna effective in both radiation performance and space requirement is a critical part of the portable devices. Antennas used in the portable devices need to be compact, low-cost, efficient, and omni-directional for commercial applications. Thus, a miniature chip antenna without an empty area for 2.4 GHz ISM band applications is proposed in this paper. As shown in Fig. 1, the dimensions of this chip antenna are only 10(L)x3(W)x3.5(H) mm3, fabricated on an FR4 substrate, so that it can be easily installed inside the portable devices. Particularly, the empty area usually needed by using other built-in antennas is not required with our chip antenna. Thus, circuit routing on a multi-layer PCB will not be restricted due to the antenna, and circuit components can even be placed near the antenna. Therefore, the PCB space can be used more efficiently to miniaturize the RF device, and the antenna can be built in the device more flexibly.

Design of RFID near-field focusing circular patch array antenna at 2.4GHz with applications

In this paper, a planar circular patch array antenna that features electric fields focused in the near-field zone for 2.4 GHz radio frequency identification (RFID) applications is presented. This array antenna is implemented by using six circular patch elements and a microstrip feeding network with a proper input phase for each element. The array antenna is capable of enhancing electric field distributions in the near zone to charge and interrogate dipole-like passive tags near the array antenna by capacitive coupling. Readable range is measured for up to 12 tags lined up closely with 1 cm spacing. Applications using the proposed array antenna with an RFID reader by Sunlit are discussed.