A Novel Carrier Suppression Method for RFID

When passive RFID tags are used, RFID readers need to transmit a constant carrier, during uplink communication to provide sufficient operating power to the tag. This high power carrier with its associated noise, limits the receiver sensitivity and, hence, the possible reading range. This letter proposes a new way to cancel the received carrier. The topology, based on a directional coupler and a reflective vector modulator, has a very small area consumption and is very attractive to use with integrated reader ICs. The principle of operation as well as the noise contribution of the circuit itself are discussed.      

铌酸锂定向耦合器的优化设计

分析了定向耦合器几个参数的相互关系,设计了钛扩散铌酸锂定向耦合器的仿真方案,用BPM软件对不同耦合间距的定向耦合器对工艺的容差进行了模拟计算,得到了几种耦合间距/串音变化的组合.     

An Efficient Reader Anticollision Algorithm in Dense RFID Networks With Mobile RFID Readers

In parallel with the proliferation of radio-frequency identification (RFID) systems, many RFID readers have been increasingly employed. In such an environment, collision among readers becomes a serious problem. Existing anticollision algorithms, depending on the information of neighboring readers, may require constant effort in order to grasp such information. Although it may be given by a server or a coordinator, they may not be suitable in dense and dynamic RFID networks with mobile readers. In this paper, we propose an efficient reader anticollision algorithm using a polling server in dense and dynamic RFID networks with mobile readers. Owing to the assistance of the server, the readers can rapidly decide whether they can work or not without interfering neighbors and can be easily synchronized. Our proposed algorithm is simple and makes readers aware of neighbors to minimize reader collisions. Performance evaluation shows how many readers can operate in a network and indicates that our proposed algorithm is more efficient than distributed color selection, colorwave, and hierarchical Q-learning algorithm, particularly in dense and mobile environments.      

A New Directional Coupler Design with High Directivity for PCS and IMT‐2000

This paper proposes a new design of directional couplers with high directivity for personal communication services (PCS) and International Mobile Telecommunications‐2000 (IMT‐2000). The directional coupler is used to check and verify the power, frequency, and antenna reflection of a signal at transmission stations for mobile communications. The performance requirements of directional couplers are a strong coupling to reduce the effect on the transmitted power and high directivity to suppress the interference of the reflected signals and reduce the errors in communication. So far, various architectures have been proposed to gain high directivity, and there have been many studies used to obtain a strong coupling. However, conventional architectures for high directivity and strong coupling have a directivity of only about 20 dB, and there have been difficulties to achieve the higher directivity of 30 dB suitable for PCS and IMT‐2000. This paper proposes a new architecture of directional couplers based on a grounding composed of strip lines, and compares the test results of this directional coupler with conventional ones. The results show that the proposed directional coupler has a directivity of more than 30 dB and is adequate for PCS and IMT‐2000.     

A 2.45-GHz Near-Field RFID System With Passive On-Chip Antenna Tags

The design of a 2.45-GHz near-field RF identification (RFID) system with passive on-chip antenna (OCA) tags is very challenging as the efficiency of RF power conversion is very low. It poses multidisciplinary research challenges such as ultra-low-power circuits design, semiconductor process technology, and integrated antenna design. This paper describes the designs of such an RFID system, the reader, and OCAs, as well as the passive tag integrated circuits in detail. The passive tag chip with 128-bit nonvolatile memory has been realized using CMOS 0.13- technology. The OCA is fabricated on top of the chip using post-processing technology. The complete RFID tag with an integrated OCA is smaller than 0.5- with a thickness of 0.1 mm. With the reader generating an output power of 0.5 W, the RFID system is able to perform with RF read/write functions at a distance of .     

Low Access Delay Anti-Collision Algorithm for Readers in Passive RFID Systems

Even though radio frequency identification (RFID) systems are spreading more and more as a medium for identification, location and tracking purposes, some reliability issues of these systems still need to be solved. In fact, RFID readers and tags experience collisions when sharing the wireless transmission channel over the same area. In this work, we propose a centralized scheduling-based algorithm as possible candidate solution for the reader collision problem in passive RFID systems. This algorithm has been designed taking into account the circuitry limitations of the tags, which do not allow the usage of frequency or code division multiple access schemes in passive RFID systems. The solution herewith proposed, which is suitable for those scenarios involving static or low mobility readers, aims at preventing reader collisions and provides at the same time low channel access delay to the readers. The performance of this algorithm has been tested via computer simulations. The results show that the proposed solution strongly reduces collision occurrences and, especially in static scenarios, provides low access delay to the readers during the channel contention phase.     

RFID-based localization with Non-Blocking tag scanning

The simple and cheap passive RFID tag systems have recently been used for efficient localization of indoor mobile robots, where each RFID tag stores its own absolute position and the mobile robot carrying an RFID reader scans the RFID tags to localize itself. The available localization schemes using passive RFID systems do not consider the scanning delay which may cause location estimation error, especially when the robot moves at a high speed. In this paper, a new Non-Blocking scanning (reading) scheme is proposed to avoid collisions so that the scanning delay, and consequently the localization error, can be reduced. This scheme avoids collisions among tag replies by assigning tag IDs based on the FCA coloring scheme. Theoretical and simulation studies indicate that the new Non-Blocking scheme combined with the new tag arrangement pattern can achieve a good RFID localization performance in terms of both estimation error and scanning delay with reduction of tag/reader required complexities.     

Coplanar-Waveguide Directional Couplers

Design information for coplanar-waveguide directional couplers has been calculated using quasi-static zeroth-order approximations. Experimental results on a 10-dB directional coupler designed from these calculations have shown reasonably good agreement with predictions. The smaller difference in even- and odd-mode velocity in a coplanar-waveguide directional coupler leads to better directivity and better performance than a microstrip directional coupler.     

CMOS RF Power Amplifier for UHF Stationary RFID Reader

A CMOS power amplifier (PA) for a UHF (860–960 MHz) stationary RFID reader is presented. To design a high power and power efficient CMOS PA, quasi four pair structure and integrated passive device (IPD) transformers are used. An amplitude modulation is performed through the cascode gate with a pulse shaping filter. The chips are fabricated in a 0.18 $mu$m CMOS process and IPD. Measurements show output power of 32.8–33.37 dBm and the power added efficiency (PAE) of 51.8–56.1% with the supply voltage 3.0 V.      

Realization of all-optical flip-flop using directionally coupled bistable laser diode

A novel all-optical flip-flop device has been realized using a directionally-coupled bistable laser diode (DC-BLD). We have fabricated the DC-BLD by a conventional fabrication technique of LDs. To separate the adjacent electrodes of the directional coupler, an oblique electron-beam evaporation technique was developed. By this self-align process, the two adjacent waveguides of the directional coupler were electrically isolated without employing any additional lithography step. Using the fabricated DC-BLD, all-optical flip-flop has been demonstrated due to the nonlinear effects of the saturable absorber and the directional coupler. The flip-flop operation has been achieved with sufficiently small input optical power level around 0 dBm.     

Compact Harmonic Filter Design and Fabrication Using IPD Technology

An integrated passive device (IPD) technology has been developed to meet the ever increasing needs of size and cost reduction in radio front-end transceiver module applications. Electromagnetic (EM) simulation was used extensively in the design of the process technology and the optimization of inductor and harmonic filter designs and layouts. Parameters such as inductor shape, inner diameter, metal thickness, metal width, and substrate thickness have been optimized to provide inductors with high quality factors. The technology includes 1) a thick plated gold metal process to reduce resistive loss; 2) MIM capacitors using PECVD SiN dielectric layer; 3) airbridges for inductor underpass and capacitor pick-up; and 4) a 10 mil finished GaAs substrate to improve inductor quality factor. Both lumped element circuit simulations and electromagnetic (EM) simulations have been used in the harmonic filter circuit designs for high accuracy and fast design cycle time. This paper will present the EM simulation calibration and demonstrate the importance of using EM simulation in the filter design in order to achieve first-time success in wafer fabrication. The fabricated IPD devices have insertion loss of 0.5 dB and harmonic rejections of 30dB with die size of 1.42 mm for high band (1710 MHz-1910 MHz) and 1.89 mm for low band (824-915 MHz) harmonic filters.     

一种提高RFID系统中耦合器定向性的方法

微带的定向耦合器是一些RFID系统中的关键性部件,功能一般是分离存在于信道中reader输出的信号和从天线接收的tag信号。定向耦合器的性能直接影响了系统所能辨识tag信号的能力,系统一般要求性能比较良好的定向耦合器。但是由于微带型定向耦合器其本身的奇偶模不平衡性,定向性一般不高。这里介绍一种新型的改进方法,通过调节耦合端的高阻抗线长度和宽度,使得定向性得到很大的提高。     

Hybrid-Ring Directional Coupler for Arbitrary Power Divisions

A directional coupler in the form of a hybrid ring is described in this paper. A theoretical analysis using the scattering matrix has been carried out and experimental verification of the theoretical result has been achieved in a stripline network. Simple design equations which enable one to design a directional coupler with any degree of coupling have been derived. This coupler differs from the commonly used couplers in that the voltages at the output arms are either in-phase or opposite-phase with respect to each other. In addition, its geometrical symmetry makes it very convenient for use in symmetrical networks, particularly as a power divider in antenna feeding systems.     

Monolithic integration of GaAs-AlGaAs quantum-well lasers with directional couplers using vertical coupling of light

A novel technique for the monolithic integration of a laser and a directional coupler in the GaAs-AlGaAs material system is demonstrated. The combination of single-step molecular beam epitaxy (MBE) on a planar substrate, vertical coupling of light between the active and passive waveguide in a p-n-p-doped structure and the use of a self-aligned fabrication process for the ridge waveguides in the active and passive sections results in a threshold current of 52 mA and an output power of up to 0.6 mW. The directional coupler is completely switched at an applied bias of 4.0 V.     

Keyless Security in Wireless Networks

Security and privacy issues in RFID technology gain tremendous popularity recently. However, existing work on RFID authentication problems always make assumptions such as (1) hash function can be fully employed in designing RFID protocols; (2) channels between readers and server are always secure. The first assumption is not suitable for EPC Class-1 Gen-2 tags, which has been challenged in many research work, while the second one cannot be directly adopted in mobile RFID applications where wireless channels between readers and server are always insecure. To solve these problems, in this paper, we propose a novel ultralightweight and privacy-preserving authentication protocol for mobile RFID systems. We only use bitwise XOR, and several special constructed pseudo-random number generators to achieve our aims in the insecure mobile RFID environment. We use GNY logic to prove the security correctness of our proposed protocol. The security and privacy analysis show that our protocol can provide several privacy properties and avoid suffering from a number of attacks, including tag anonymity, tag location privacy, reader privacy, forward secrecy, and mutual authentication, replay attack, desynchronization attack etc. We implement our protocol and compare several parameters with existing work, the evaluation results indicate us that our protocol significantly improves the system performance.     

An Ownership Transfer Scheme Using Mobile RFIDs

RFID reader equipment is widely used in hand-held devices; thus, the security of the connection between mobile readers and RFID servers is an important issue. In this paper, we propose a novel scheme with low implementation costs and conforming to EPC C1G2 standards. The benefits include reducing the manpower required for market management, market members using the mobile readers to query product information, as well as ensuring secure and efficient cash transactions. The membership can also access after-sales service or make ownership transfers with other users. Moreover, in order to achieve mutual authentication, our proposed scheme integrates fingerprint biometrics, related cryptology and a hash function mechanism to ensure the security of the transmitted messages.     

Autonomous Mobile Robot Navigation Using Passive RFID in Indoor Environment

This paper proposes an efficient method for localization and pose estimation for mobile robot navigation using passive radio-frequency identification (RFID). We assume that the robot is able to identify IC tags and measure the robot's pose based on the relation between the previous and current location according to the IC tags. However, there arises the problem of uncertainty of location due to the nature of the antenna and IC tags. In other words, an error is always present which is relative to the sensing area of the antenna. Many researches have used external sensors in order to reduce the location errors, with few researches presented involving purely RFID driven systems. Our proposed algorithm that uses only passive RFID is able to estimate the robot's location and orientation more precisely by using trigonometric functions and the IC tags' Cartesian coordinates in a regular gridlike pattern. The experimental results show that the proposed method effectively estimates both the location and the pose of a mobile robot during navigation.      

C波段单片有源环行器基本单元的研究

本文分析和研究了微波有源环行器所用的基本单元电路——放大器和定向耦合器.利用微波CAD欢件完成了放大器、定向耦合器和有源环行器的设计.模拟分析得出:在3.8～4.2GHz频率范围内,单片放大器的正向增益是6dB.反向隔离度为22dB:单片定向耦合器的正向插入损耗是4dB,反向隔离度为18dB.该有源环行器的隔离度是19dB,正向插损是5dB.实验结果为:放大器在3.5～4.0GHz频率范围内,正向增益是4.5dB,反向隔离度是23dB;定向耦合器在3.2～3.8GHz频率范围内,正向插入损耗是8dB,反向隔离度为23dB.     

基于PDA的RFID手持机开发研究

文章研究了如何利用无线射频识别(RFID)读写模块和PDA(掌上电脑)来进行RFID手持机的开发.首先简要描述了硬件设备、软件开发的流程和RFID盘点系统的功能模块,然后研究了开发过程中的通信接口、数据库同步等关键问题,最后将所开发的RFID手持机与传统RFID手持机进行了比较.结果表明,前者具有方便、快捷和直观等特点,能在实际应用中提高工作效率.