共查询到20条相似文献,搜索用时 15 毫秒
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《IEEE transactions on information theory / Professional Technical Group on Information Theory》1975,21(2):222-226
The results of an experiment are described in which contextual information is used to improve the performance of an optical character reader when reading English text. Specifically, English is modeled as a Markov source and the Viterbi algorithm is used to do maximuma posteriori sequence estimation on the output of an optical character reader (OCR). 相似文献
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Radio-frequency identification (RFID) is a recent technology that utilizes radio frequencies to track the object by transmitting a signal with a unique serial identity. Generally, the drawbacks of RFID technology are high cost and authentication systems between a reader and a tag become weak. In this paper, we proposed a protocol for RFID tag–reader mutual authentication scheme which is hardware efficient and consumes less dynamic power. Truncated multipliers are implemented in RFID tag–reader mutual authentication protocol system due to reduction in hardware cost and dynamic power. Experimental evaluation reveals that the proposed protocol with truncated multipliers provides more security than the earlier schemes. The proposed protocol is described in VHDL and simulated using Altera Quartus II. The functional block is implemented as hardware using an Altera DE2 Cyclone II (EP2C35F672C6) Field-Programmable Gate Array (FPGA). 相似文献
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介绍了一种基于计算机通用串行总线接口的指纹采集器的设计。说明了指纹采集器的工作原理、功能结构及其设备驱动程序软件、外围设备接口通讯软件的编写方法。采用即插即用计算机外设接口(USB)技术和模块化设计思想是本设计的最大特点。 相似文献
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基于MSP430单片机的实用射频卡读卡电路设计 总被引:1,自引:0,他引:1
以射频识别技术的实际应用为背景,采用低功耗RF射频感应式收发模块MTP-K4,结合低功耗FLASH型16位RISC指令集MSP430单片机,设计一个射频卡读卡电路。给出各部分的硬件电路设计原理图,描述各个功能的实现方法,同时给出部分程序代码。采用本电路设计的门禁系统保密性强,并具有远程监控的特点。 相似文献
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非接触E5550卡读写器在公路收费系统中的应用 总被引:3,自引:0,他引:3
在公路收费系统中,卡座的寿命直接影响了IC卡的普及使用。本文介绍一种非接触ID IC卡(E5550)的结构及其读写方法。利用89C51开发了一种廉价非接触ID IC卡的读写器。并将其应用到公路收费系统中,效果良好。 相似文献
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Davies S.W. Eizenman M. Pasupathy S. 《IEEE transactions on bio-medical engineering》1999,46(9):1044-1056
The faithful recovery of the base sequence in automatic DeoxyriboNucleic Acid (DNA) sequencing fundamentally depends on the underlying statistics of the DNA electrophoresis time series. Current DNA sequencing algorithms are heuristic in nature and modest in their use of statistical information. In this paper, a formal statistical model of the DNA time series is presented and then used to construct the optimal maximum-likelihood (ML) processor. The DNA-ML algorithm that is derived in this paper features Kalman prediction of peak locations, peak parameter estimation, whitened waveform comparison and multiple hypothesis processing using the M-algorithm. Properties of the algorithm are examined using both simulated and real data. Model parameters of critical importance and their impact on different types of error mechanisms, such as insertions and deletions, are pointed out. The statistical model of the DNA time-series and the structure of the DNA-ML algorithm provides a basis for future investigation and refinement of DNA sequencing techniques. 相似文献
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The addition of an optional feedback loop to a previously described automatic analog curve reader, which was originally designed for reconversion of EEG ink recordings to electrical form, permits operation of the curve reader as a true line follower, often a more appropriate method for reconversion of polygraphic ink recordings having gradual to moderate slopes. 相似文献
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The development of compact, low-height bar code readers for European supermarkets, where clerks sit at checkstands arranged much like office desks, is described. The technology used to meet all the requirements for this application is described. The resulting reader features advanced hologram lenses, for less-expensive optics and greater efficiency 相似文献
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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. 相似文献
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为简化UHF RFID读写器系统设计,提高读写器控制模块控制协调能力、抗干扰强度、降低功耗,提出了一种基于NiosⅡ处理器的UHF RFID读写器控制模块的SOPC设计方案。采用SOPC设计理念,在一个可配置的FPGA芯片上嵌入NiosⅡ处理器,搭载操作系统,实现收发信号的数字处理控制及与上位机系统的通信控制。根据设计需要充分配置了处理器性能,给出了模块硬件结构,模块与上位机、数字基带处理模块间的通信接口及模块软件设计流程图。仿真结果表明,该控制模块能实现所需控制信号的产生和传输,完成协议解析、时序控制、状态转换及防碰撞等功能。与传统嵌入式控制模块相比,该控制模块实时控制能力强、稳定性高,功耗更低,外围电路更简单,系统更小型化。 相似文献
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Handheld radio frequency identification reader units become increasingly important with the adoption of passive ultra-high frequency RFID systems in supply chain, warehouse, and retail store management. Important requirements for the handheld reader unit are ergonomic size and weight, sufficient battery life, and suitable read range for the desired applications. In addition, usability of the reader unit in terms of reading directions and orientations of tags has to be taken into account. This article presents a performance comparison of compact reader antennas for a handheld UHF RFID reader unit. The reader antennas presented in this study are designed to be affixed either inside the casing of the reader unit or into an external reader antenna module. The presented antenna designs have been optimized with finite element method modeling. The resonance frequency and bandwidth characteristics are analyzed using modeled and measured results. Read range measurement results with the antenna designs affixed to the handheld reader are presented and analyzed to verify the practical performance. All the antenna designs presented in this article are applicable to a handheld RFID reader unit 相似文献
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Applications of passive radio frequency identification (RFID) systems have gained considerable attentions in recent years. Because a passive tag must obtain its operating power from a continuous wave transmitted from a reader in a conventional RFID system, reader coverage is limited. Thus, expanding reader coverage is a current goal in RFID research. In this work, passive tags are provided with additional operating power via continuous waves in multiple frequency bands. In an interrogation region, continuous wave emitters, which provide additional operating power to passive tags, are deployed according to the base station configuration in a cellular phone system. Because transmission power of continuous wave emitters must consider the reader command demodulation constraint and minimum operating power required by a tag, transmission power of continuous wave emitters must be chosen carefully. A method for analyzing reader coverage in multi-carrier passive UHF RFID systems is derived in this work. Assuming all tags are uniformly distributed in an interrogation region, the optimal continuous wave emitter transmission power that achieves the largest reader coverage can be analytically determined. Simulation results verify that continuous wave emitters with suitable transmission power expand reader coverage in a multi-carrier passive UHF RFID system. Additionally, adjusting reader power in the forward (reader-to-tag) link duration can loosen the reader command demodulation constraint and thereby further expand reader coverage. 相似文献
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A two-stage differential linear power amplifier(PA) fabricated by 0.18μm CMOS technology is presented. An output matching and harmonic termination network is exploited to enhance the output power,efficiency and harmonic performance.Measurements show that the designed PA reaches a saturated power of 21.1 dBm and the peak power added efficiency(PAE) is 35.4%,the power gain is 23.3 dB from a power supply of 1.8 V and the harmonics are well controlled.The total area with ESD protected PAD is 1.2×0.55 mm~2.Sy... 相似文献