• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1243-1253
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• 2007

Recently UHF RFID system has drawn a great deal of attention because of its potential to revolutionize supply chain management. An important characterization of the performance of a RFID system is 'interrogation range', which is defined as the maximum distance between a reader and a tag. Forward-link interrogation range is defined as the maximum distance from which the tag receives just enough power to turn on and back-scatter, and reverse-tink interrogation range is the maximum distance from which the reader can detect this back-scattered signal. A link balance has to be found between the two interrogation ranges. In this paper, the interrogation range equations are formulated in both forward-link and reverse-link and a trade-off between the two values is investigated in order to maximize the interrogation range. As a result, it is observed that the gain of the reader antenna, the isolation of the circulator, and the phase noise of the local oscillator with range correlation effect mainly determine the reverse-link interrogation range.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.489-499
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• 2011

RFID technologies, which allow collecting, storing, processing, and tracking information by wirelessly recognizing the inherent ID of object through an attached electronic tag, have a variety of application areas. This paper presents a novel carrier leakage suppression RF(CLS-RF) front-end for ultra-high-frequency RF identification reader. The proposed reader CLS-RF front-end structure generates the carrier leakage replica through the nonlinear path that contains limiter. The limiting function only preserves the frequency and phase information of the leakage signal and rejects the amplitude modulated tag signal in the envelope. The carrier leakage replica is then injected into the linear path that contains phase shifter. Therefore, the carrier leakage signal is effectively cancelled out, while not affecting the gain of the desired tag backscattering signal. We experimentally confirm that the prototype shows a significant improvement in the leakage to signal ratio by up to 36 dB in 910 MHz, which is consistent with our simulation results.

• Journal of electromagnetic engineering and science
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• v.10 no.3
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• pp.79-85
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• 2010

In this paper, a directive antenna design with a combination of electric-magnetic radiators for an radio frequency identification(RFID) system is presented. To generate a directive antenna radiation pattern, a structure combining a dipole and loop antenna is presented. A reader antenna and tag antenna are proposed for the RFID system. For the reader antenna, the frequency bandwidth defined by $S_{11}$<-10 dB is approximately from 820~990 MHz. The forward and backward gain differences are 1.5~2 dBi. For the tag antenna, the frequency bandwidth is approximately from 860~920 MHz with a maximum gain of 3.58 dBi at 910 MHz. In both cases, directive radiation characteristics are observed.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.415-418
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• 2007

This paper presents the design and analysis of LNA-Mixer for 2.45GHz RFID reader. The LNA is implemented by PCSNIM method for low power consumption. The Mixer is implemented by using the Gilbert-type configuration, current bleeding technique, and the resonating technique for the tail capacitance. The connection between the two designed circuits is made by active balun. This LNA-Mixer has about 35dB for -40dBm input RF power, LO power is 0dBm and RF frequency is 2.45 GHz and IIP3 is -4dBm. The layout of LNA-Mixer for one-chip design in a $0.18-{\mu}m$ TSMC process has 2.6mm ${\times}$ 1.3mm size.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.423-426
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• 2007

An active Balun is designed for RFID reader at 2.45GHz. The Balun is integrated inside the receiver, then the LNA and mixer can be connected. The unbalanced LNA output signal is transformed to a balanced signal at the input mixer The RF mixer and LO mixer, by using this balun. The Balun provided a balanced signal with two output stage, gain mismatch is 0.116dB. The phase show a good behavior with $163.918^{\circ}$,$-16.609^{\circ}$. The phase mismatch is about $0.527^{\circ}$. The tight difference between the gain and phase on each brancd, is because of the used capacitor and integrated inductor and the other parasitic element inside the balun.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1719-1724
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• 2013

In this paper, a size-reduction technique is presented for the RFID reader antenna working at two UHF bands. To tackle the problem of size increase in multi-band applications, two resonance paths are made to occur in one geometry with a single feed. While one resonance path is combined with the other, the entire geometry is determined to guarantee the resonance at the target frequencies through the dual-band input impedance matching. The antenna performance is predicted by the full-wave simulation, and the design method is verified by observing the good agreement between the simulated and measured results. At the two frequencies, the satisfactory return loss as well as the antenna efficiency and peak gain of the far-field pattern is obtained.

• ETRI Journal
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• v.34 no.2
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• pp.147-158
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• 2012

In this paper, we present a demodulation structure suitable for a reader baseband receiver in a passive radio frequency identification (RFID) environment. In a passive RFID configuration, an undesirable DC-offset phenomenon may appear in the baseband of the reader receiver, which can severely degrade the performance of the extraction of valid information from the received tag signal. To eliminate this DC-offset phenomenon, the primary feature of the proposed demodulation structures for the received FM0 and Miller subcarrier signals is to reconstruct the signal corrupted by the DC-offset phenomenon by creating peak signals from the corrupted signal. It is shown that the proposed method can successfully detect valid data, even when the received baseband signal is distorted by the DC-offset phenomenon.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.10
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• pp.1491-1497
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• 2013

Radio frequency identification (RFID) is an important and essential components of ubiquitous computing, with the development of wireless communication technologies and mobile computing environment. Recently, RFID becomes the mainstream application that helps fast handling and uniquely identifying the physical objects. It utilizes the electromagnetic energy for data transmission from a tag to a reader in the presence of arbitrary interference and noise. In order to employ the portable mobile RFID reader, a tag-collision problem between two or more adjacent tags should be considered. In this paper, we present the operation of RFID system in which numerous tags are present in the interrogation zone of a single reader at the same time. Since there may exist a number of tagged objects in the narrow area, multiple RFID tags may interfere each other, caused to degrade the data reliability and efficiency of the RFID system. In order to suppress interference signals from multiple neighboring tags, we present an application of Gold code for RFID communication system, which uses spread spectrum technique. In this RFID system, data bits are spreaded in each tags with the unique Gold code and the spreaded data bits are despreaded in the reader with the same Gold code. The performance analysis of the considered RFID anti-collision system is illustrated via computer simulation examples.

• Tunnel and Underground Space
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• v.26 no.4
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• pp.253-265
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• 2016

In this study, travel time data collection of mine equipments was conducted in an underground mine using a reverse Radio Frequency IDentification (RFID) system. In the reverse RFID system, RFID readers and antennas are mounted on mine equipments, and RFID tags are attached to the underground mine gallery. Indoor experiments were performed to analyze how RFID reader transmission power levels affect tag readable area and tag recognition rates. The results showed that travel time measurement become precise when the reader transmission power was reduced, however tag recognition rates were reduced. The field experiments indicated that setting the reader transmission power to 28 dBm maintained the tag recognition rate while minimizing the tracking location error. In addition, the results revealed that the reverse RFID system can be used successfully in an underground mine to collect the travel time data of haulage trucks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1B
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• pp.85-94
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• 2010

Many RFID systems use dynamic slotted ALOHA to identify the label information of the RFID tags. One of the key problems in the RFID system is how to estimate the number of RFID tags up to the desired level of accuracy. In this paper, we present the framework of tag estimation algorithm for the collision-oblivious (CO) reader which can only decide whether the tag response is successful or not. Thus, the CO reader must rely on the success estimator to predict the RFID tag population. We propose two estimation algorithms to predict the number of RFID tags, named the memoryless success estimator (MSE) and the intersection-based success estimator (ISE). The MSE considers only the estimate obtained at the current inventory round, while the ISE finds an appropriate intersection interval of the existing estimates collected at every inventory round. Through the simulation results, we demonstrate that the ISE is a fast, accurate, and controllable estimator whose performance is close to that of the collision/idle estimators.