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畢業(yè)論文（設(shè)計(jì)）開題報(bào)告 題目名稱 CA6140車床831008撥叉零件數(shù)控加工工藝及工裝設(shè)計(jì) 學(xué)生姓名 王曉宇 專業(yè) 機(jī)電技術(shù)教育 班級(jí) 042班 指導(dǎo)教師姓名 杜家熙 專業(yè) 機(jī)械制造 職稱 副教授 完成期限 2009年2月16日至2009年2月27日 一、選題的目的意義 隨著我國(guó)現(xiàn)代制造技術(shù)的發(fā)展，數(shù)控機(jī)床的普及和從事數(shù)控加工人員的增多，數(shù)控加工越來(lái)越受到人們的重視。撥叉是一種重要輔助零件，廣泛應(yīng)用于我們的日常生活及生產(chǎn)當(dāng)中，在機(jī)械行業(yè)有著越來(lái)越重要的作用，撥叉零件的制造精度能不能夠滿足加工技術(shù)要求；如何更大限度的降低機(jī)加工的基本勞動(dòng)時(shí)間及提高單位時(shí)間內(nèi)的生產(chǎn)率，都成為機(jī)械行業(yè)勢(shì)待解決的技術(shù)性問題。隨著數(shù)控技術(shù)的不斷發(fā)展成熟及數(shù)控技術(shù)應(yīng)用的不斷廣泛化、深入化、大眾化，我們意識(shí)到，采用數(shù)控機(jī)床來(lái)加工撥叉零件既能夠提高零件的精度又能夠完成采用普通機(jī)床加工時(shí)應(yīng)運(yùn)受限的瓶頸，對(duì)提高加工效率、以及降低勞動(dòng)強(qiáng)度都有不可估量之好處。 二、國(guó)內(nèi)外研究現(xiàn)狀 隨著計(jì)算機(jī)科學(xué)、信息技術(shù)的迅速發(fā)展，傳統(tǒng)的制造業(yè)已發(fā)生了十分顯著的變化，發(fā)達(dá)國(guó)家正進(jìn)行由傳統(tǒng)的制造技術(shù)向現(xiàn)代制造技術(shù)的轉(zhuǎn)變，并提出了全新的制造模式。數(shù)控加工技術(shù)將逐步引航現(xiàn)代機(jī)械制造業(yè)的發(fā)展。數(shù)控機(jī)床的應(yīng)用范圍日益擴(kuò)大，其產(chǎn)生的經(jīng)濟(jì)效益與社會(huì)效益十分明顯。尤其是數(shù)控加工不斷朝高速、精密方向的發(fā)展，提高數(shù)控機(jī)床的應(yīng)用范圍對(duì)于提高制造企業(yè)的競(jìng)爭(zhēng)力有著重要的意義。 對(duì)傳統(tǒng)零件的數(shù)控加工技術(shù)也得到越來(lái)越廣泛的應(yīng)用。面對(duì)新技術(shù)、新工藝的不斷出現(xiàn)，提高數(shù)控加工技術(shù)在傳統(tǒng)撥叉類零件的應(yīng)用也受到越來(lái)越多的重視。如何使數(shù)控技術(shù)在加工這一類零件中表現(xiàn)出其高質(zhì)量、高精度、高效率，都成為各國(guó)爭(zhēng)先要解決的問題。因此研究它對(duì)我國(guó)的制造行業(yè)很有借鑒作用。 三、主要研究?jī)?nèi)容 1) 數(shù)控加工工藝的特點(diǎn)及說(shuō)明； 2) 數(shù)控加工的一般步驟； 3) 撥叉零件數(shù)控加工工藝原理及特點(diǎn)； 4) 撥叉在數(shù)控加工中的應(yīng)用及其優(yōu)越性； 5) 通過(guò)撥叉零件的工裝設(shè)計(jì)來(lái)體現(xiàn)數(shù)控加工的重要作用； 四、畢業(yè)論文（設(shè)計(jì)）的研究方法或技術(shù)路線 1. 根據(jù)設(shè)計(jì)內(nèi)容查閱相關(guān)期刊資料； 2. 利用網(wǎng)絡(luò)查找相關(guān)資料進(jìn)行修改整理； 3. 對(duì)實(shí)際生產(chǎn)中撥叉零件沒的應(yīng)用進(jìn)行統(tǒng)計(jì)總結(jié)； 4. 論文總結(jié)。 五、參考文獻(xiàn)與資料 [1] 趙家奇. 機(jī)械制造工藝學(xué)課程設(shè)計(jì)指導(dǎo)書(2版). 北京：機(jī)械工業(yè)出版社,2006. [2] 曾志新,呂明. 機(jī)械制造技術(shù)基礎(chǔ). 武漢：武漢理工大學(xué)出版社,2001. [3] 李益明. 機(jī)械制造工藝設(shè)計(jì)簡(jiǎn)明手冊(cè). 北京：機(jī)械工業(yè)出版社,1993. [4] 肖詩(shī)綱. 切削用量手冊(cè). 北京：機(jī)械工業(yè)出版社,1993. [5] 金屬切削機(jī)床夾具設(shè)計(jì)手冊(cè). 上海柴油機(jī)廠工藝設(shè)備研究所編. 北京：機(jī)械工業(yè)出版社，1987. [6] 李旦，邵東向，王杰等. 機(jī)床專用夾具圖冊(cè). 哈爾濱：哈爾濱工業(yè)大學(xué)出版社（2版），2005. [7] 羅良玲，劉旭波. 數(shù)控技術(shù)及應(yīng)用. 北京：清華大學(xué)出版社，2005. [8] 邏輯. 數(shù)控工藝及刀具. 重慶：重慶大學(xué)出版社，2006. [9] 劉武發(fā)，劉德平. 機(jī)床數(shù)控技術(shù). 北京：化學(xué)工業(yè)出版社，2007. [10] 劉萬(wàn)菊. 數(shù)控加工工藝及編程. 北京：機(jī)械工業(yè)出版社，2007. [11] 余英良. 數(shù)控工藝與編程技術(shù). 北京：化學(xué)工業(yè)出版社，2007. [12] 楊建明. 數(shù)控加工工藝與編程. 北京：北京理工大學(xué)出版社，2006. [13] 賀曙新，張思第，文少波. 數(shù)控加工工藝. 北京：北京工業(yè)出版社，2005. [14] 聶秋根，陳光明. 數(shù)控加工實(shí)用技術(shù). 北京：電子工業(yè)出版社，2007. [15] 唐應(yīng)謙. 數(shù)控加工工藝學(xué). 北京：中國(guó)勞動(dòng)保障出版社，2000. [16] 胡志剛. 計(jì)算機(jī)輔助繪圖. 北京：高等教育出版社，1999. [17] 趙家奇編. 機(jī)械制造工藝學(xué)課程設(shè)計(jì)指導(dǎo)書2版. 北京: 機(jī)械工業(yè)出版社，2000. [18] 李云主編. 機(jī)械制造及設(shè)備指導(dǎo)手冊(cè). 北京: 機(jī)械工業(yè)出版社，1997. [19] 孟少農(nóng)主編. 機(jī)械加工工藝手冊(cè). 北京: 機(jī)械工業(yè)出版社，1991. [20] 徐圣群主編. 簡(jiǎn)明加工工藝手冊(cè). 上海: 上海科學(xué)技術(shù)出版社，1991. 六、指導(dǎo)教師審批意見 摘 要 本設(shè)計(jì)分析研究了CA6140車床變速箱中拔叉零件的加工工藝規(guī)程及夾具設(shè)計(jì)。由于拔叉零件的結(jié)構(gòu)較為復(fù)雜，工序較多，因此為保證加工精度提高生產(chǎn)率及降低勞動(dòng)強(qiáng)度，考慮采用數(shù)控機(jī)床進(jìn)行加工，首先進(jìn)行了撥叉零件工藝性分析、確定了工藝方案及加工順序，進(jìn)行了撥叉零件數(shù)控加工工藝規(guī)程設(shè)計(jì)和鉆孔工序的夾具設(shè)計(jì)，為撥叉零件在數(shù)控機(jī)床上加工提供了理論依據(jù)和有效的硬件保證。 關(guān)鍵詞：數(shù)控加工工藝，定位，夾緊，專用夾具 CA6140 Lathe 831008 Fork Parts CNC Machining Technology and Equipment Design Abstract Analysis of the design of the gearbox in the CA6140 lathe machining fork and Fixture Design Process.Fork parts as a result of the more complex the structure, process more, so in order to ensure the accuracy of processing to increase productivity and reduce labor intensity, consider the use of CNC machine tools for processing, first of all, a fork components analysis process to determine the technology solutions and processing order , a fork parts Process Design CNC machining and drilling of the fixture design process, fork parts for CNC machine tools in the processing provides a theoretical basis and an effective assurance of hardware. Keywords: NC Machining Process, Positioning, Clamping, Special Fixture 目 錄 1 緒論 ............................................................................................................................1 2 數(shù)控加工工藝概述 ....................................................................................................1 2.1 數(shù)控加工工藝分析的一般步驟與方法 .............................................................1 2.2 機(jī)床的合理選用 .................................................................................................1 2.3 數(shù)控加工零件工藝性分析 .................................................................................2 2.3.1 零件圖樣上尺寸數(shù)據(jù)的給出應(yīng)符合編程方便的原則 ..............................2 2.3.2 零件各加工部位的結(jié)構(gòu)工藝性應(yīng)符合數(shù)控加工的特點(diǎn) ..........................2 2.4 加工方法的選擇與加工方案的確定 .................................................................2 2.4.1 加工方法的選擇 ..........................................................................................2 2.4.2 加工方案確定的原則 ..................................................................................3 2.5 工序與工步的劃分及加工順序安排 .................................................................3 2.5.1 工序的劃分 ...................................................................................................3 2.5.2 工步的劃分 ..................................................................................................3 2.5.3 加工順序安排 ..............................................................................................4 2.6 零件的安裝與夾具的選擇 .................................................................................4 2.6.1 定位安裝的基本原則 ..................................................................................4 2.6.2 選擇夾具的基本原則 ..................................................................................4 2.7 刀具的選擇與切削用量的確定 .........................................................................4 2.7.1 刀具的選擇 ..................................................................................................4 2.7.2 切削用量的確定 ..........................................................................................5 2.8 對(duì)刀點(diǎn)與換刀點(diǎn)的確定 .....................................................................................5 2.9 加工路線的確定 .................................................................................................5 3 撥叉零件數(shù)控加工工藝分析 ....................................................................................6 3.1 撥叉零件的作用 .................................................................................................6 3.2 撥叉零件的工藝分析 .........................................................................................7 3.3 確定撥叉零件生產(chǎn)類型 .....................................................................................7 3.4 確定撥叉零件毛坯類型 .....................................................................................7 3.4.1 確定毛坯種類 ..............................................................................................7 3.4.2 確定鑄件加工余量及形狀 ..........................................................................7 3.4.3 繪制鑄件零件圖 ..........................................................................................8 3.5 撥叉零件數(shù)控加工工藝規(guī)程設(shè)計(jì) .....................................................................8 3.5.1 選擇定位基準(zhǔn) ..............................................................................................8 3.5.2 制定數(shù)控加工工藝路線 ..............................................................................8 3.6 機(jī)械加工余量、工序尺寸及公差的確定 .........................................................9 3.6.1 圓柱表面工序尺寸 ......................................................................................9 3.6.2 平面工序尺寸 ............................................................................................10 3.6.3 確定切削用量及時(shí)間定額 ........................................................................10 4 夾具設(shè)計(jì) ..................................................................................................................19 4.1 問題的提出 .......................................................................................................19 4.2 夾具設(shè)計(jì) ...........................................................................................................19 4.2.1 定位基準(zhǔn)選擇 ............................................................................................19 4.2.2 切削力及夾緊力計(jì)算 .................................................................................20 4.3 定位誤差分析 ....................................................................................................20 4.3.1 定位元件尺寸及公差的確定 .....................................................................20 4.3.2 計(jì)算鉆套中心線與工作臺(tái)的垂直度誤差 .................................................20 4.3.3 計(jì)算定位銷軸與工作臺(tái)的平行度誤差 .....................................................21 4.4 夾具設(shè)計(jì)及操作的簡(jiǎn)要說(shuō)明 ............................................................................21 5 結(jié)束語(yǔ) .......................................................................................................................23 致謝 ..............................................................................................................................24 參考文獻(xiàn) ......................................................................................................................25 撥叉零件的數(shù)控加工工藝及工裝設(shè)計(jì),論文作者：王曉宇 學(xué) 號(hào)：20040315025 所在班級(jí)：機(jī)教042 指導(dǎo)老師：杜家熙,一：撥叉零件數(shù)控加工工藝簡(jiǎn)述 隨著數(shù)控技術(shù)應(yīng)用的不斷廣泛化、深入化、大眾化，為了提高傳統(tǒng)零件的的制造精度、提高勞動(dòng)生產(chǎn)率及降低勞動(dòng)強(qiáng)度，考慮采用數(shù)控加工來(lái)滿足其要求。 對(duì)于撥叉零件來(lái)說(shuō)由于其形狀較復(fù)雜、加工工序較多，為提高加工效率，考慮采用數(shù)控機(jī)床進(jìn)行加工。,二：撥叉的普通加工工序,工序01 粗銑20、50下端面，以T2為粗基準(zhǔn)，采用X51立式銑床加專用夾具； 工序02 粗銑20上端面，以T1為定位基準(zhǔn)，采用X51立式銑床加專用夾具； 工序03 粗銑50上端面，以T4為定位基準(zhǔn)，采用X51立式銑床加專用夾具； 工序04 鉆、擴(kuò)20孔，以32外圓和T2為基準(zhǔn)，采用Z525立式鉆床加專用夾具； 工序05 粗鏜50孔，以D1為定位基準(zhǔn)，采用T616臥式鏜床加專用夾具； 工序06 銑斜肩，以D1和T2為定位基準(zhǔn)，采用X51立式銑床加專用夾具； 工序07 精銑20下端面，以T2為基準(zhǔn)，采用X51立式銑床加專用夾具； 工序08 精銑20上端面，以T1為基準(zhǔn)，采用X51立式銑床加專用夾具； 工序09 粗鉸、精鉸20孔，以T2和32外圓為基準(zhǔn)，采用Z525立式鉆床加專用夾具； 工序10 精銑50端面，以D1為基準(zhǔn)，采用X51立式銑床加專用夾具； 工序11 半精鏜50孔，以D1做定位基準(zhǔn)，采用T616臥式鏜床加專用夾具； 工序12 鉆、鉸8錐孔，以T1和零件中線為基準(zhǔn)，采用Z525立式鉆床加專用夾具； 工序13 鉆M6底孔，攻螺紋，以T1和零件中線為基準(zhǔn)，采用Z525立式鉆床并采用專用夾具； 工序14 銑斷，以D1為基準(zhǔn)，采用X60臥式銑床加專用夾具,撥叉的數(shù)控加工工序：,工序01 粗銑、精銑20、50下端面，以T2為粗基準(zhǔn)，采用立式數(shù)控銑床加專用夾具； 工序02 粗銑、精銑20上端面，以T4為定位基準(zhǔn)，采用立式數(shù)控銑床加專用夾具；粗銑、精銑50上端面，以T4為定位基準(zhǔn)，采用立式數(shù)控銑床加專用夾具； 工序03 鉆、擴(kuò)20孔，粗鉸、精鉸20孔；以32外圓和T2為基準(zhǔn)，采用立式數(shù)控鉆床加專用夾具；粗鏜、半精鏜50孔，以D1為定位基準(zhǔn)，采用臥式數(shù)控鏜床加專用夾具； 工序04 銑斜肩，以D1和T2為定位基準(zhǔn)，采用立式數(shù)控銑床加專用夾具； 工序05 精銑50端面，以D1為基準(zhǔn)，采用立式數(shù)控銑床加專用夾具； 工序06 鉆、鉸8錐孔，以T1和零件中線為基準(zhǔn)，采用立式數(shù)控鉆床加專用夾具； 工序07 鉆M6底孔，攻螺紋，以T1和零件中線為基準(zhǔn)，采用立式數(shù)控鉆床并采用專用夾具； 工序08 銑斷，以D1為基準(zhǔn)，采用臥式數(shù)控銑床加專用夾具；,三：鉆、擴(kuò)20孔，粗鉸、精鉸20孔，粗鏜、半精鏜50孔的數(shù)控加工時(shí)夾具的設(shè)計(jì),圖一：撥叉零件圖,1).定為基準(zhǔn)的選擇：,由零件圖可知，孔20、50為通孔，跟撥叉的上下底面有垂直度的技術(shù)要求要求，為使定位誤差為零，應(yīng)該選擇撥叉下底面為定位基準(zhǔn)保證該垂直度要求。此外，還應(yīng)以20孔外圓柱面為基準(zhǔn)，從而保證孔在精度要求。 為了提高加工效率，現(xiàn)決定采用自動(dòng)夾緊工件快換裝置，并采用快換鉆套以利于在鉆底孔后進(jìn)行精鉸或精鏜。,2).夾緊力的計(jì)算：,（1）鉆20時(shí)的夾緊力 由實(shí)際加工的經(jīng)驗(yàn)可知,鉆削時(shí)的主要切削力為鉆頭的切削方向,即垂直于工作臺(tái),查切削手冊(cè)表2.3，切削力計(jì)算公式為： 其中： ， ， ， ， ， 與加工材料有關(guān),取0.94；與刀具刃磨形狀有關(guān),取1.33；與刀具磨鈍標(biāo)準(zhǔn)有關(guān),取1.0，則：,,,（2）鉆50孔時(shí)的夾緊力,由實(shí)際加工的經(jīng)驗(yàn)可知,鉆削時(shí)的主要切削力為鉆頭的切削方向,即垂直于工作臺(tái),查切削手冊(cè)表2.3，切削力計(jì)算公式為： 其中： ， ， ， ， ， 與加工材料有關(guān),取0.94；與刀具刃磨形狀有關(guān),取1.33；與刀具磨鈍標(biāo)準(zhǔn)有關(guān),取1.0，則：,,由實(shí)際加工的經(jīng)驗(yàn)可知,鉆削時(shí)的主要切削力為鉆頭的切削方向,即垂直于工作臺(tái),查切削手冊(cè)表2.3，切削力計(jì)算公式為： 其中： ， ， ， ， ， 與加工材料有關(guān),取0.94；與刀具刃磨形狀有關(guān),取1.33；與刀具磨鈍標(biāo)準(zhǔn)有關(guān),取1.0，則：,,,3）：夾具體的設(shè)計(jì),圖二 ： 夾具體,4):夾具體的設(shè)計(jì),圖三 ： 夾具體,5）夾具裝備圖的設(shè)計(jì)：,,圖四 ： 裝備圖,由于能力有限，設(shè)計(jì)中有錯(cuò)誤和不妥之處，敬請(qǐng)各位老師批評(píng)指正。 謝謝！,河南科技學(xué)院 2009屆本科畢業(yè)論文（設(shè)計(jì)） 外文資料 學(xué)生姓名：王曉宇 所在院系：機(jī)電學(xué)院 所學(xué)專業(yè)：機(jī)電技術(shù)教育 導(dǎo)師姓名：杜家熙 完成時(shí)間：2009年3月27日 Network architectures The term architecture is commonly used today to describe networks. A network architecture, such as illustrated in Fig.1.7, describes the components in the network, how they operate , and what form they take . A network encompasses hardware, software, data link controls (DLC), Standards, topology, and protocols. 1. hardware The physical equipment in the network is referred to as the hardware. Typical of such equipment are computers, modems, telephone, terminals , machines, controllers, and the like. 2. Software Software consists of programs, procedures, and sometimes, associated documentation of the operation of the communication system. Communications software (CSW), application programs (AP), network control programs (NCP), operating system (OS), and database management system (DBMS) are examples of software. 3. Protocols A protocol defines how network components establish communications, exchange data, and terminate communications. A protocol is essentially a formal set of conventions, or rules, between communicating processes about of messages to be exchanged. Handshaking and line discipline are also protocols. To make implementation and usage more convenient in sophisticated networks, higher-level protocols may use lower-level in a layered fashion. 4. Data link controls A data link consists of electronic equipment such as electronic devices, terminals, and machines and the interfacing circuits that are operating in a particular way to permit information to be exchanged between installations. The specific method of operation is defined by transmission codes, transmission modes, and direction control. There are two major categories link control protocol in use today: (1) Asynchronous, in which bit streams are transferred at fixed rates with the transmitter and receiver operating in synchronization by the clock. (2）The flow of date to and from the many points and links within the network must be controlled and orderly. The sending and receiving sites must sequencing of the messages being transmitted among all users. The connection path between sits is usually shared by more than one user, as multipoint configuration. A multi-point line, sometimes called a multi-drop line, is a communications line having several subsidiary controllers that share time on the line under the control of a central site. Date line controls provide for all these needs. They manage the flow of data messages across the communications path, or links. In essence, they are special kinds of protocols consisting of a combination of software and hardware located at each site in the network. Through a communication link, the DLC protocol pro-vides for the reliable interchange of information between data terminal equipment. Typical DLC functions in the network are the following: Synchronizing the sender and receiver 1) Controlling the sending and receiving of data 2) Detecting and recovering transmission errors between two points 3) Maintaining awareness of link conditions 4) Topologies Topology describes the surface layout the elements comprising the communications network-----that is, it is the shape of the system. Communication system may be implemented in a variety of ways. typical communication system are telephone lines, radio wave links, networks, serial connections, parallel connections and power line system modulations. The choice of topology depends on factors such as cost, response time, throughput, capacity, load sharing, and capacity needs. 5. Local area networks A local area network (LAN) is a communications network operating in a local area. It extends from several hundred to several thousand feet within a building or other facility. A LAN is owned and operated by an individual or organization and is, therefore, not subject to regulation by either the federal communications commission (FCC) or the state Public Utility Commission (PUS). A LAN is a means of connecting various types of equipment for the purpose of sharing resources and communicating in a distributed processing environment, as illustrated in fig .1.8. that is , all device that must communicate with one another in a CIM environment can be tied together though some form of common interface such as a LAN . An effective LAN has specific characteristics. Typical of these are the following: ① Is in a moderate-sized geographic area (office, laboratory, building, factory, industrial complex, or campus, for example) ② Has medium –to high –sped data channel(s) ③ Provides reliable communications ④ Is owned and used by a single organization ⑤ Connects independent devices rather than a device and its peripherals A LAN usually has four major components that serve to transport data between end users: user workstation, protocol control logic. medium interface, and physical path. 6. User workstation The user workstation is used to accomplish an application. The station can be anything from a word processor to a mainframe computer. (1) Protocol control logic A protocol control logic takes user is information and converts it to a protocol that can move the LAN network to reach the desired location , the protocol logic also controls the LAN and provides for the end user is access to the network . （2) Medium Interface The medium interface function generates the electrical signals to be transmitted on the LAN the interface is between the path the protocol logic can take several forms, typical of which are CATV (cable television) taps , infrared diodes for infrared path , microwave antennas, or complex laser-emitting semiconductors for optic fibers. (3) Physical Path A LAN is path may consist of coaxial TV cables, coaxial bade-band cables, twisted pair of wires, optic fibers, and microwaves. Cable TV coaxial cable is used in many networks because it has a high capacity, a very good signal-to-noise ratio, low signal radiation, and low error rates. (4) Manufacturing Automation Protocol There are many types and sizes of networks. Some LAN systems are owned by an organization and are confined to the premise of that organization. Others are owned by national or international public networks that may be accessed by the user. In many case, LAN systems may also connect to public networks and be able to access them. Network are also connected in several configurations (topologies) , as seeing in Fig .1.9.Each topology can constitute an entire network or can be just a portion of a large network . A star network is a centralized network in which each device is connected virtually to a central controlling point. A ring network, sometimes called a loop, is a network in which each device is connected to the next in sequence in a closed, circular fashion. This topology has two possible paths, one in each direction. A bus network is a topology that consists of a single shared line to which all devices are connected. In a hierarchy network, a central root node has over the entire network. The secondary nodes attached to the root can be front-end processors (EEP) that in turn connect to tertiary nodes of lesser significance. The hierarchy can consist of a large computer that has overall of several smaller control devices connected to their own terminals. A multiply connected topology requires that there be at least two paths between any pair of nods to assure availability and reliability m the event of failure one path or node. The unconstrained network occurs most commonly. The term unconstrained merely means that the configuration is not restricted to one specific kind of connection. Many LAN systems are available today. All use either base-bands, broad-bands, or both, in a base-band, the line is pulsed, as in the on/off conditions. Because these pulses are still the square wave direct current, they require no additional special handling or modulation, which makes the process relatively inexpensive, it is impossible to mix voice and data unless the analog voice signals have been previously digitized. The broadband technology requires a conversion process and is therefore more expensive. The advantages gained are that voice, video, and data can all be sent on the same channels. Facilities can be shared through assignment of frequency channels to allow all devices to operate simultaneously. Popular modulation and multiplexing techniques can be used because a wide range of frequencies is available. 4