The next-generation wireless broadband technology is changing the way we work, live, learn, and communicate through effective use of state- of-the-art mobile broadband technology. The packet-data-based revolu- tion started around 2000 with the introduction of 1x Evolved Data Only (1xEV-DO) and 1x Evolved Data Voice (1xEV-DV) in 3GPP2 and High Speed Downlink Packet Access (HSDPA) in 3GPP. The wireless broad- band fourth-generation technology (4G) is an evolution of the packet- based 3G system and provides a comprehensive evolution of the Universal Mobile Telecommunications System specifications so as to remain competitive with other broadband systems such as 802.16e (WiMAX)
標簽： Essentials LTE-A LTE and of
上傳時間： 2020-05-27
上傳用戶：shancjb
This book is intended to help electric power and telephone company personnel and individuals interested in properly protecting critical tele- communications circuits and equipment located in high voltage (HV) environments and to improve service reliability while maintaining safe working conditions. Critical telecommunications circuits are often located in HV environments such as electric utility power plants, substations, cell sites on power towers, and standalone telecommuni- cations facilities such as 911 call centers and mountaintop telecom- munications sites.
標簽： Protection Voltage High
上傳時間： 2020-05-27
上傳用戶：shancjb
OSCILLATORS are key building blocks in integrated transceivers. In wired and wireless communication terminals, the receiver front-end selects, amplifies and converts the desired high-frequency signal to baseband. At baseband the signal can then be converted into the digital domain for further data processing and demodula- tion. The transmitter front-end converts an analog baseband signal to a suitable high- frequency signal that can be transmitted over the wired or wireless channel.
標簽： High-Frequency Oscillator Design
上傳時間： 2020-05-27
上傳用戶：shancjb
The first edition as well as its forerunner of Kuffel and Abdullah published in 1970 and their translations into Japanese and Chinese languages have enjoyed wide international acceptance as basic textbooks in teaching senior under- graduate and postgraduate courses in High-Voltage Engineering. Both texts have also been extensively used by practising engineers engaged in the design and operation of high-voltage equipment. Over the years the authors have received numerous comments from the text’s users with helpful suggestions for improvements. These have been incorporated in the present edition. Major revisions and expansion of several chapters have been made to update the continued progress and developments in high-voltage engineering over the past two decades.
標簽： Engineering Voltage High
上傳時間： 2020-06-07
上傳用戶：shancjb
The PW4055 is a complete constant-current /constant-voltage linear charger for single cell lithiumion batteries.Its ThinSOT package and low external component count make the PW4055 ideallysuited for portable applications.Furthermore, the PW4055 is specifically designed to work within USBpower specifications.The PW4055 No external sense resistor is needed, and no blocking diode is required due to theinternal MOSFET architecture.Thermal feedback regulates the charge current to limit the dietemperature during high power operation or high ambient temperature. The charge voltage is fixedat 4.2V, and the charge current can be programmed externally with a single resistor. The PW4055automatically terminates the charge cycle when the charge current drops to 1/10th the programmedvalue after the final float voltage is reached. When the input supply (wall adapter or USB supply) isremoved, the PW4055 automatically enters a low current state, dropping the battery drain currentto less than 2μA. The PW4055 can be put into shutdown mode, reducing the supply current to 25μA.The BAT pin has a 7KV ESD(HBM) capability. Other features include charge current monitor, undervoltage lockout, automatic recharge and a status pin to indicate charge termination and the presenceof an input voltage
標簽： pw4055
上傳時間： 2022-02-11
上傳用戶：jason_vip1
射頻識別(Radio Frequency Identification，RFID)是一種允許非接觸式數據采集的自動識別技術。其中工作在超高頻(Ultra High Frequency，UHF)頻段的無源RFID系統，由于在物流與供應鏈管理等領域的潛在應用，近年來得到了人們的廣泛關注。這種系統所使用的無源標簽具有識別距離長、體積小、成本低廉等突出特點。目前在市場上出現了各種品牌型號的UHF RFID無源標簽，由于不同品牌型號的標簽在設計與制造工藝上的差異，這些標簽在性能表現上各不相同，這就給終端用戶選擇合適自己應用的標簽帶來了困難。RFID基準測試就是在實際部署RFID系統前對RFID標簽的性能進行科學評估的有效手段。然而為了在常規實驗室條件下得到準確公正的測試結果，需要對基準測試的性能指標及測試方法學開展進一步的研究。本文正是研究符合EPC Class1 Gen2標準的RFID標簽基準測試。 本文首先分析了當前廣泛應用的超高頻無源RFID標簽基準測試性能指標與測試方法上的局限性與不足之處。例如，在真實的應用環境中，由于受到各種環境因素的影響，對同一品牌型號的標簽，很難得到一致的識讀距離測試結果。另外，在某些測試場景中，使用識讀速率作為測試指標，所得到的測試結果數值非常接近，以致分辨度不足以區分不同品牌型號標簽的性能差異。在這些分析基礎上，本文把路徑損耗引入了RFID基準測試，通過有限點的測量與數據擬合分別得到不同類型標簽的路徑損耗方程，結合讀寫器天線的輻射方向圖，進一步得到各種標簽受限于讀寫器接收靈敏度的覆蓋區域。無源標簽由于其被動式能量獲取方式，其實際工作區域仍然受限于前向鏈路。本文通過實驗測試出這些標簽的最小激活功率后，得出了各種標簽在一定讀寫器發射功率下的激活區域。完成這些步驟后，根據這兩種區域的交集可以確定標簽的工作區域，從而進行標簽間的比較并達到基準測試的目的，并能找出限制標簽工作范圍的瓶頸。 本文最后從功率損耗的角度研究了標簽之間的相互干擾，為用戶在密集部署RFID標簽的場景中設置標簽之間的最小間隔距離具有重要的參考意義。
上傳時間： 2013-04-24
上傳用戶：hbsunhui
隨著綠色工程的實施，在照明領域，已將電力電子技術廣泛應用到電氣照明中去，所以尋找綠色、高效、長壽命、光色好等優點的照明設備已成為必然。高強度氣體放電燈(High-Intensity-Discharge)由于光效高而節能，已經在照明領域取得廣泛的應用。但傳統的電感鎮流器存在諸多缺點，故與之配套的HID燈電子鎮流器的開發成為研究的熱點，本文對基于數字控制的HID燈電子鎮流器進行了研究與設計。 本文第二章闡述了氣體放電的基礎知識和電光源的基本參數。比較了電子電感鎮流器的優缺點，針對HID燈對電子鎮流器的要求，介紹了電子鎮流器基本原理和發展趨勢。第三章對高強度氣體放電燈的關鍵技術進行了研究。首先是對電子鎮流器的拓撲結構進行分析與比較，選定了傳統的三級結構進行設計，其次是對電子鎮流器的核心-逆變器的結構進行了分析，選定了全橋逆變結構，再次是對HID燈的各種點火電路的結構進行分析，本文選定了用單片機進行控制的點火的方式；最后是對燈的聲諧振進行了各種方式的比較與分析，給出通過數字調頻的方式來抑制聲諧振理論分析。第四章主要通過比較各種功率因數校正的優缺點，并采取了基于boost結構的臨界功率因數校正。第五章對HID燈啟動工作過程進行了分析，提出了三段線性控制的策略，給出了控制的理論分析;比較了間接和直接兩種控制恒功率的方法，選定間接控制方式。第六章主要對數字控制的250W金鹵燈的樣機的實現中的部分電路(保護、驅動、逆變)進行分析與設計并給出了部分電路圖和軟件設計的流程圖以及部分仿真與試驗波形。最后在第七章對試驗結果進行分析，對本文的設計進行小結以及對未來的展望。
上傳時間： 2013-07-16
上傳用戶：heart_2007
30kHz高頻開關電源變壓器的設計:Design of 30kHz High－frequency SMPS Transformer 在傳統的高頻變壓器設計中，由于磁心材料的限制，
上傳時間： 2013-04-24
上傳用戶：Kecpolo
CR6221 combines a dedicated current mode PWM controller with a high voltage power MOSFET. It is opti
上傳時間： 2013-04-24
上傳用戶：brucewan
CR6228 combines a dedicated current mode PWM controller with a high voltage power MOSFET. It is opti
上傳時間： 2013-05-17
上傳用戶：natopsi
