Won-Kyu Choi

Polarization and Space Diversity Antenna Using Inverted-F Antennas for RFID Reader Applications

An orthogonal antenna is presented for reader applications of radio frequency identification (RFID) at 433 MHz. The antenna is composed of two 1 times 2 subarrays orthogonally placed on a ground plane. Two different feeding networks are introduced to control horizontal and vertical radiation current flows for each subarray, respectively. An inverted-F structure is used as a radiation element with vertical and horizontal currents flowing on the radiator, thereby obtaining two linear polarizations. Antenna gains are 3.71 and 3.43 dBi and isolation between the two input ports is less than 25 dB

RFID tag antenna with a meandered dipole and inductively coupled feed

This paper presents tag antennas with an inductively coupled feed structure for the RFID application in the UHF band. The designed antennas consist of the rectangular loop for feeding and meandered dipole. We estimate the maximum bandwidth of the designed antenna using the approximate calculation and the calculated results are verified by measuring the read range of the tag antennas as a function of frequency. The read range of the designed RFID tag is approximately from 2.5 m to 4 m in air

STUDY ON THE DEMODULATION STRUCTURE OF READER RECEIVER IN A PASSIVE RFID ENVIRONMENT

In this paper, we present a demodulation structure suitable for a reader receiver in a passive Radio Frequency IDentification (RFID) environment. In a passive RFID configuration, undesirable DC-offset phenomenon may appear in the baseband of the reader receiver. As a result, this DC-offset phenomenon can severely degrade the performance of the extraction of valid information from a received signal in the reader receiver. To mitigate the DC-offset phenomenon, we propose a demodulation structure to reconstruct a corrupted signal with the DC-offset phenomenon, by extracting useful transition information from the corrupted signal. It is shown that the proposed method can successfully detect valid data from a received signal, even when the received baseband signal is distorted with the DC-offset phenomenon.

Broadband circularly polarized corner-truncated square patch array antenna

A circularly polarized antenna with low cost foam substrate and film is proposed to obtain wide bandwidth and high performance. The proposed antenna is composed of stacked corner-truncated patches with sequential rotation feed. Having above 20% return loss and axial ratio bandwidths, the designed antenna can be used for application of a broadband system using circular polarization. And, as low cost foam and film is used for the substrate, a low cost antenna can be designed.

Near-field antenna for RFID smart shelf in UHF

This paper presents the design of a near-field reader and tag antennas in UHF that can be used for various smart shelves. The tag antenna is designed by introducing an “S”-shaped or “+”-shaped slot to the circular patch and the reader one is a rectangular slot array fed by a microstrip line. These antennas operated in UHF near-field are more reliable in many RFID applications where reading distance is not the major factor. Electric coupling concept between the reader and tag antenna is employed for near-field communication.

High-Q band rejection filter by using U-slot DGS

This paper presents a new U-slot defected ground structure (DGS) in the microstrip line for the use in the design of high-Q band rejection filter. Compared to the conventional DGS, a U-slot DGS has a simple shape but the slope of its rejection characteristic is more steep. The Q factor of the band rejection property for the U-slot DGS increases when the distance between two slots in the U-shape decreases. By employing three cascaded U-slot DGSs, a high-Q band stop filter is designed and fabricated. Experimental results show that the Q factor of the band stop filter with three U-slot DGSs is 38.4.

A planar inverted-F antenna (PIFA) to be attached to metal containers for an active RFID tag

The main purpose of this paper is to present a planar inverted-F antenna to be attached to metal containers. The designed PIFA introduce various shapes of slots and meander line for size reduction and loop-shaped stubs for impedance matching. The impedance bandwidth of the PIFA is about 1.4% for VSWR<2 and the maximum gain is about 2.5 dBi

High gain and broadband microstrip patch antenna using a superstrate layer

In this paper, the gain of the single patch with the superstrate is compared to that of the single patch without the superstrate and the experimental results of 2/spl times/8 array antenna with the superstrate, and 4/spl times/8 array antenna without the superstrate are shown. Details of the proposed antenna design are presented.

A frequency agile floating-patch MEMS antenna for 42 GHz applications

A novel frequency agile floating-patch MEMS (micro-electro-mechanical system) antenna is proposed for 42 GHz applications. The floating-patch MEMS antenna is fabricated on a high resistivity silicon (HRS) substrate using surface micromachining technology. Simulation and experimental results for reflection coefficients and radiation patterns are presented.

Radiation efficiency improvement method of RFID tag antenna for metallic objects printed on lossy substrate

This paper proposes a novel design method of RFID tag antenna on metallic surfaces using a lossy substrate such as FR4. The proposed design reduces the substrate loss and improves the radiation efficiency more than double compared with a conventional PIFA (planar inverted-F antenna). The antenna can be directly matched to the typical high-Q impedance of a tag chip, which consists of small resistance and large capacitive reactance.