Ha-Ryoung Oh

Extending the Interrogation Range of a Passive UHF RFID System With an External Continuous Wave Transmitter

This paper introduces an interrogation enhancer (IE) as an external system that boosts a reader continuous wave (CW) with its auxiliary CW. The boosted reader CW powers the backscatters from a passive ultrahigh frequency radio frequency identification (UHF RFID) tag to reach the reader in extended range. The system performance is verified according to the measured ranges in practical tests. The IE permits the reader to successfully interrogate the tag in tripled or doubled range (e.g., 80-290 and 182-370 cm). The measurement results imply that the IE can be used for readers that may not transmit enough CW due to the local regulation or its limited battery capacity.

A 900-MHz Direct-Conversion Transceiver for Mobile RFID Systems

A fully integrated 900-MHz direct-conversion transceiver for mobile RFID system is presented. The transceiver consists of a low noise amplifier, a down-conversion mixer, a band pass filter, and programmable gain amplifier (PGA) for RX path; and a power amplifier, an up-conversion mixer, a low-pass filter, and a PGA for TX path. In addition, the fractional N PLL is integrated to cover different frequency standards for different nations. The transceiver meets the dense reader environment specifications.

Analysis of phase noise requirements on local oscillator for RFID system considering range correlation

Simple and new analysis method of phase noise requirements on a local oscillator (LO) for a RFID system is proposed. In general case, phase noise requirements are derived mathematically considering a reciprocal mixing with an interference signal. However, in RFID systems using the same oscillator for the transmitted signal and the LO, range correlation phenomenon effects the phase noise requirements. Thus we tried to derive new phase noise equation considering the range correlation effect on the residual phase noise in RFID system. Simulation results for IMF RFID system show that range correlation effect is a crucial factor in RFID system design.

Performance evaluation of mobile RFID under multiple BoMR environments

Form factor and demand for low power consumption limit the transmission power of UHF mobile RFID readers. BoMR [1], a kind of booster for mobile RFID readers to extend the read range, was introduced and its performance was analyzed. But some practical issues such as collision and interference should be estimated for its widespread usage. In this paper, the collision, interference and performance of BoMRs are evaluated under multiple BoMR environments. Simulation model with DEVS formalism is presented and the results are summarized. Finally, the performances of LBT schemes are studied by simulation.

Compact Size Directional Coupler for Mobile RFID Reader

In order to offer RFID services on mobile phones, the RFID reader must be embedded on the handset as a chip. However, the directional coupler, a ceramic passive component used in conventional handsets, of an RFID system using an identical Tx/Rx carrier frequency has a significant volume limitation compared to active components. This paper presents the directional coupler design for UHF RFID mobile reader using IPD (integrated passive device) process. The parallel-coupled line theory has been used for formulation of a T and pi-type coupler. Coupler with dimensions of 1.74times1.6, and 1.32times1.4 mm was assembled using the IPD process.

An Implementation of a RFID Reader System for EPC Class-1 Generation-2 Specification

As RFID systems are applied to various fields and applications such as supply chain management, asset management, location based applications etc. the requirements becomes diverse. For example, Much higher performance, TCP/IP protocol stack are required in some applications. However, low end processors based systems such as 8051 processor can not meet such requirements due to their low processing capacity and limited size of memory. In this paper a UHF band RFID system which meets the EPC Class-1 Generation-2 specification with ARM920T-based processor is implemented and tested.

Quad Band CEIFS Antenna for Mobile Communication

A novel compact cascaded-E inverted-F slot (CEIFS) type microstrip antenna is proposed for quad bands, radio frequency telephone systems. This antenna design is particularly unique since it supports the new generation mobile phone handsets where multiband operation with minimum size is greatly desired. Slot lines are embedded in the antenna in cascaded-E and inverted-F shape parallel to the edge of the antenna length. This kind of new structure provides broad banding and multiple frequency bands. Detail of design criteria with respect to physical parameters is described. Radiation patterns and impedance bandwidths are measured and shown

Conceptual Design and Simulation of an Unmanned Battery Exchangeable Electric Bus Management System

The exchangeable battery electric bus is an eco-friendly public transportation vehicle. Due to the technological limitation, however, it should repeatedly change batteries with charged ones. The unmanned battery exchangeable electric bus being studied in Korea can exchange batteries automatically by using a battery swapping system. In this paper, we propose an unmanned battery exchangeable electric bus management system. The proposed system provides two services: the bus information service and the battery change scheduling service. The bus information service is the existing traditional metropolitan area bus information systems, which inform bus passengers how long they should wait for the buses. Our second service assigns a low-battery bus, which needs to change the batteries, to the battery swapping system, which stores fully-charged batteries. To validate the proposed system, we model the system by using the DEVS formalism. The simulation result shows that the proposed system provides the services properly.

Extending the Read Range of UHF Mobile RFID Readers: Arbitration Methods Based on Interference Estimation

The read range of UHF mobile readers can be extended by a booster for mobile RFID readers (BoMR). But in an environment where multiple BoMRs are installed, the read success rate may be decreased due to signal interference. This paper proposes three arbitration methods based on interference estimation with the purpose of enhancing the read success rate. A central arbitration server manages global information in centralized arbitration method (CAM) without broadcast/multicast communication facility. In fully distributed arbitration method (FDAM), all the arbitration messages are broadcasted from a BoMR to every BoMR, and each BoMR decides with broadcasted global information. Events in FDAM are serialized naturally with broadcasted messages. Cluster Distributed Arbitration Method (CDAM) forms clusters with multicasted BoMRs and a selected BoMR acts as an arbiter in the cluster. Such effects as lengthened read range, improved the read success rates of readers can be obtained by the proposed methods without any hardware modification. In order to evaluate the arbitration methods, the RFID system is modeled by using the DEVS formalism and simulated by using the DEVSim++.

Design of a Multi-Thread Architecture for an LLRP Server

LLRP (Low-Level Reader Protocol) specifies an interface between RFID readers and RFID applications, also called LLRP servers and clients respectively. An LLRP server should concurrently execute various functions. This paper designs an LLRP server of a multi-threaded architecture. For that, (i) the operational procedure between LLRP servers and clients is investigated, (ii) the functional requirements of LLRP servers are presented, (iii) the operation of an LLRP server is decomposed into several threads to satisfy those functional requirements, and (iv) the operational procedure is further examined in thread-level. To validate the designed architecture, it is modeled and simulated by using the DEVS formalism which specifies discrete event systems in a hierarchical, modular manner. From the simulation result, we can conclude that the proposed architecture conforms the LLRP standard and satisfies all the given functional requirements.