【正文】 Create and promote a mon industry view on an architectural framework.? Help consolidate standards groups and work in conjunction with other existing standards organizations and groups.B. The Composite Vision? 20 Mbps data rates? Streaming Audio/Video? Asymmetric Access? Adaptive Modulation/Coding? Dynamic packet assignment? Smart/Adaptive antennas supportedC. 4G Network Architecture“4G” wireless networks can be realized with an IPbased core network for global routing along with more customized localarea radio access networks that support features such as dynamic handoff and adhoc routing as well as newer requirements such as selforganization,QoS, multicasting, content caching, etc..In 4G LANs will be installed in trains and trucks as well as buildings, or even just formed on an adhoc basis between random collections of devices that happen to e within radio range of one other. Routing in such networks will depend on new architectures, already under development by the IEEE and a European project called Mobile IP Network Developments (MIND).D. The working Principle In 4Gstyle mobile IP, each cell phone is assigned a permanent home IP address, along with a careof address that represents its actual a puter somewhere on the Internet wants to municate with the cell phone, it first sends a packet to the phone39。D labs to move beyond the limitations and problems of 3G which is having trouble getting deployed and meeting its promised performance and throughput .While this 3G has not pletely reached researchers and vendors are expressing growing interest in 4G why? Two main areas are addressed in these initiatives: An increase of capacity in the radio link and seamless mobility across heterogeneous access networks. Section 2 discusses about the issues of 3G that has created interest towards 4G developments. Section 3 about evolution and parison,Section 4 describes about the goals and the vision, section 5 explains about some of the technologies for 4G, and in other following sections the applications, the research and other issues for 4G developments are discussed.II. WHY THE LEAP TOWARDS 4G?3G networks are in a very painful phase of their development, with early trials yielding disappointing results, costs ballooning, technical glitches, and network operators being forced to deflate expectations based on unrealistic hype. Despite the hype surrounding the higherspeed 3G mobile networks now under construction, the reasons for the leap towards 4G are:A. PerformanceIndustry skeptics say that users will not be able to take advantage of rich multimedia content across wireless networks with 3G. 4G munications will feature extremely highquality video equal to that of highdefinition television. In addition, it will enable wireless downloads at speeds exceeding 100 Mbps, about 260 times than 3G wireless network.B. InteroperabilityThere are multiple standards for 3G making it difficult to roam and interoperate across networks. We need a global standard that provides global mobility and service portability so that service provider would no longer be bound by singlesystem vendors of proprietary equipment.C. Networking3G are based on primarily a widearea concept. We need hybrid networks that utilize both wireless LAN (hot spot) concept and cell or basestation WAN design. With 4G,the world would have base stations everywhere, ensuring phone users connection to a highspeed network anywhere, anytime.D. BandwidthWe need wider bandwidth and higher bit rates. The 4G technology, with its transmission speeds of more than 20 mbps, would offer highbandwidth services within the reach of LAN hotspots, installed in offices, homes, coffee shops ,and airport lounges. Away from these hotspots, customers could connect to soupedup 2G networks for voice and rudimentary data coverage.E. TechnologyUnlike 3G, 4G will more resemble a conglomeration of existing technologies rather than an entirely new standard. Analysts define 4G as a seamless bination of existing 2G wireless networks with localarea networks (LANs) or Bluetooth.F. ConvergenceConvergence involves more than mere technology。研究心電放大電路對于心電放儀的研制具有比較實際的意義。測得。電源通過連線分別接入以上各個部分。即是說，雖然前端采用集成化器件已經(jīng)有了很高的共模抑制比，但由于它不能消除干擾以及后級電路再次引入50Hz工頻干擾，在電路的最后部分仍需加入50Hz陷波器，其可以采用雙T帶阻濾波器，其品質因數(shù)與反饋系數(shù)有一定比例關系，但并不是品質因數(shù)越大越好，品質因數(shù)越大，其β也越大，電路將出現(xiàn)不穩(wěn)定甚至自激振蕩。其作用是將電極板上獲得的心電信號送到放大器的輸入端。AD6MAX4194的輸入緩沖電路圖如圖所示是AD6MAX4194的輸入緩沖電路，可以提高輸入阻抗，通過最右邊的電阻網(wǎng)絡取出共模信號，可以進行共模驅動，再經(jīng)過反向放大可以做右腿驅動，能獲得較高的共模抑制比。理論上，在運算放大器為理想的情況下，并聯(lián)型差動放大器的輸入阻抗為無窮大，共模抑制比也為無窮大。 三運放差分放大電路電路中輸入級由AA4兩個同相輸入運放電路并聯(lián)，再與A5差分輸入串聯(lián)的三運放差分放大電路構成，其中AA2是增加電路的輸入阻抗。③信息綜合化，網(wǎng)絡化：建立心電工作站和完善的心電檢測數(shù)據(jù)庫，完善心電分析內容，結合臨床提供的其他信息資料進行綜合化信息分析判斷。自動心電圖在模擬心電圖、數(shù)字心電圖技術的基礎上，在獲取了心電圖數(shù)字信號的前提下，采用各種算法對信號進行預處理、特征波形(P波、QRS波、T波和ST段)識別、特征參數(shù)檢測并實現(xiàn)心電圖自動分析與自動診斷，其核心技術在于算法。ECG是一種重要的心電信號檢測技術，它反映心臟興奮地產(chǎn)生、傳導和恢復過程ELECTR0NIC TEST中的生物電變化。除去系統(tǒng)參數(shù)外，每個部分還有其不同的衡量性能的參數(shù)，為了不顯累贅將在第三章測試中一一詳細介紹。 (2)查明冠狀動脈循環(huán)障礙。心臟在機械性收縮之前，首先產(chǎn)生電激動。第一章 心電放大器系統(tǒng)概述第1節(jié) 心電放大器系統(tǒng)簡介和基本原理一、心電放大器總體簡介心電信號是一種十分微弱的信號，常見的心電頻率一般在0—100Hz之間，能量主要集中在17Hz附近，幅度小于5mV，大約在10uV（胎兒）～5mV（成人）之間，所需放大倍數(shù)大約為5001000倍。3　 輸出阻抗測量方法：接好電路，輸入小直流信號，分別測其直接輸出電壓和加1Ω 負載后的電壓輸出，通過分壓公式，可求得輸出阻抗。1901年，荷蘭生物學家萊頓大學教授Willem Emoven首次描記出比較滿意的PQRST波群，于1903年發(fā)明了世界上第一臺采用弦線電流計和光學記錄的方法制成的心電圖機，記錄出每個心動周期的心臟變化曲線，1912年Waller將心電變化曲線命名為“心電圖(Electrocardiogram，ECG)。早期的Holter系統(tǒng)中，馬達變速、定期保養(yǎng)和更換是磁帶記錄的一大難題，1985年后出現(xiàn)了固態(tài)Holter系統(tǒng)，它把心電信號轉換成數(shù)字信號后存儲在芯片上，避免了馬達引起的一些問題。第二章 心電放大器方案論證及電路 第一節(jié) 前置放大電路的設計一 、備選方案前置放大器是硬件電路的關鍵所在，設計的好壞直接影響信號的質量，從而影響到儀器的特性。這樣對于A3和A4的漂移要求就會降低。由于阻容耦合電路的隔直作用，后級的儀器放大器可以做到很高的增益，進而得到很高的共模抑制比。第二節(jié) 共模信號抑制電路的設計一 、備選方案有源屏蔽驅動電路有源屏蔽驅動電路可以用來消除共模電壓。各導聯(lián)線以不同顏色的標志來表示所接的部位。即, 所以，RV KΩ， KΩ左右，R19在2 KΩ左右， KΩ。當然變壓器的磁心一般是錳鋅鐵氧體的，不能用硅鋼片的。四、后級主運放電路增益測量方法：連好主運放電路，輸入一定大小的信號，測其輸出信號，其比值即運放增益。論文最難的方面在于，將理論和實際相結合，完成自己的邏輯框架；最有收獲的方面是，完成整個過程，最后成了一篇文章。s home directory server on the home network forwards this to the careof address via a tunnel, as in regular mobil