Horng-Dean Chen

Circularly Polarized Loop Tag Antenna for Long Reading Range RFID Applications

A novel circularly polarized (CP) loop antenna design for a UHF band (902-928 MHz) radio frequency identification (RFID) tag is proposed to overcome the polarization mismatch problem between reader antenna and tag antenna. The structure of the proposed tag antenna is a simple square-loop type loaded with an open gap, two feeding strips, and a matching stub. The open gap and two feeding strips were used to achieve good CP radiation. Desirable impedance matching between the tag antenna and RFID chip was attained by tuning the matching stub. Besides achieving satisfactory 3-dB axial-ratio and 10-dB impedance bandwidths of approximately 5.5%, good antenna gain and reading range of more than 2.8 dBic and 16.3 m, respectively, were also demonstrated.

Circularly polarized annular-ring slot antenna for WiMAX 2.3 GHz and WLAN 2.4 GHz applications

The design of a novel microstrip-line fed circularly polarized (CP) annular-ring slot antenna (ARSA) is studied. To achieve CP radiation with broad axial ratio (AR) bandwidth that can cover both the WiMAX 2.3 GHz and WLAN 2.4 GHz bands, a simple method of loading an inverted L-shaped slot into the bottom section of the ARSA is proposed. Measured results show that the proposed antenna can exhibit wide 10-dB impedance bandwidth of 48% (1.69-2.76 GHz), and its corresponding 3-dB AR bandwidth was approximately 8% (2.29-2.48 GHz).

Compact Circularly Polarized Meandered-Loop Antenna for UHF-Band RFID Tag

A planar loop antenna design for ultra-high frequency radio frequency identification (UHF RFID) operating in the 922-928 MHz band is investigated. To achieve compact size of 58.6 × 58.6 mm2 for this loop antenna, the technique of using meandered-loop structure is applied, and by further introducing an open gap into this meandered-loop, good circularly polarized (CP) radiation is also attained. Desirable impedance matching between the meandered-loop antenna and RFID chip is achieved by applying a simple matching stub. Besides exhibiting satisfactory 3-dB axial-ratio (AR) bandwidth of 921-929 MHz and 10-dB impedance bandwidth of 915-942 MHz, good antenna gain of 1.73 dBic and long read range of up to 20.5 m are also demonstrated.

Magnetic and resistive properties of

Detailed studies of the magnetic properties and resistivity of the ternary intermetallic compound are presented. Besides the low-temperature antiferromagnetic transition at , a possible second anomaly in the magnetic and transport properties has been found at about . Below , a metamagnetic behaviour was observed. In the region , the magnetic susceptibility and magnetization data show that an extra spin magnetic moment appears, in addition to the Curie-Weiss and Pauli paramagnetism. It is suggested that the observed anomalies in the temperature dependencies of the resistivity and magnetic susceptibility are related to the effect of spin correlations. Several mechanisms of the spin fluctuations are discussed.

Compact size annular-ring slot antenna with broad circularly polarized bandwidth

A novel microstrip-line fed circularly polarized (CP) annular-ring slot antenna (ARSA) is investigated. To achieve broad CP bandwidth, a simple method of loading a lightning-shaped slot into the bottom section of the ARSA is proposed. Measured results show that the proposed antenna has wide 10-dB impedance bandwidth of 41.15% (2.20-3.34 GHz), and its corresponding CP bandwidth was approximately 12.94% (2.24-2.55 GHz).

Low-profile PIFA array RFID tag antenna mountable on metallic objects

The use of radio frequency identification (RFID) system has increased noticeably in recent years. Tag antenna is one of the essential components for an RFID system. Many applications require tag antennas to be of low profile and to be mounted on metallic objects. Although several designs based on PIFAs or microstrip antennas have been developed for RFID tags mountable on metallic objects [1]-[4], they may be limited by their inconvenient mounting on metallic objects because of their high profile. However, it is inherently obvious for PIFA or microstrip antenna that lowering the antenna profile would degrade its antenna gain. In order to improve the gain of a low-profile antenna and provide applicable reading range, array antennas are considered to be effective candidates. In this paper, we present a design of a low-profile PIFA array antenna for a RFID tag mounted on metallic objects. With shorting pins placed at the inner edges of the patches, two quarter-wavelength microstrip lines with two additional matching stubs are needed in order to achieve conjugate impedance matching, and a broadband operation can be obtained. The effect of the spacing between the PIFAs on RFID tag reading range in the presence of metal plates is investigated.

An annular-ring slot antenna with CP radiation and harmonic suppression

A microstrip-line fed annular-ring slot antenna with circularly polarized (CP) radiation is initially studied. To achieve harmonic suppression for this antenna, the technique of loading a defected ground structure into the ring slot is proposed. Measured and simulated results show that the proposed antenna can achieve broad CP bandwidth of 9.7% (2.26-2.49 GHz), while good harmonics suppression from 3 to 10 GHz are also demonstrated.

Open slot antenna for smartwatch application

This paper presents an open slot antenna for the Bluetooth smartwatch with a metallic frame. The proposed antenna is formed by an open slot and a 50-Ω microstring line. The size of the metal frame selected here is 42 × 42 × 5 mm3 in total. This bandwidth of the antenna can cover the 2.4-GHz band (2400 ∼ 2485 MHz) for Bluetooth operation. The users wrist effects on the antenna performance are also studied.

LTE/WWAN monopole antenna with band-stop matching circuit for tablet computer

A simple two-branch monopole antenna coupled-fed with an Z-shape monopole for the LTE/WWAN operations in tablet computer application is presented. The antenna is composed of a two-branch strip monopole and an Z-shape monopole. Adding a band-stop matching circuit can improve the bandwidth of the lower band, and thus the proposed antenna can cover the lower band (698 ∼ 960 MHz) and higher band (1710 ∼ 2690 MHz) for the LTE/WWAN operation. Design consideration and results of the proposed antenna are presented and discussed.

Simple open slot antenna for LTE/WWAN smartphone with metallic frame

A simple open slot antenna for the LTE/WWAN operation is presented for the smartphone with a metallic frame. A novel feeding network integrated with a chip capacitor is used to excite the antenna, and the bandwidth of the lower band can be greatly enhanced. Two wide bands for the proposed antenna are easy to adjust and can cover the LTE/WWAN operation in the 698–960 MHz and 1710–2690 MHz bands.