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1、福建工程學(xué)院 電磁波與微波技術(shù) 課程設(shè)計(jì) ----帶阻濾波器的設(shè)計(jì)與仿真 課 題：帶阻濾波器的設(shè)計(jì)與仿真 指導(dǎo)老師： 姓 名： 學(xué) 號(hào)： 目 錄 1. 設(shè)計(jì)要求3 2. 微帶短截線帶阻濾波器的理論基礎(chǔ)3 2.1 理查德變換4 2.2 科洛達(dá)規(guī)則6 3. 設(shè)計(jì)步驟7 3.1 ADS 簡(jiǎn)介7 3.2 初步設(shè)計(jì)過程8 3.3 優(yōu)化設(shè)計(jì)過程14 3.4 對(duì)比結(jié)果17 4. 心得體會(huì)17 5. 參考文獻(xiàn)18

2、 1．課程設(shè)計(jì)要求： 1. 1 設(shè)計(jì)題目：帶阻濾波器的設(shè)計(jì)與仿真。 1.2 設(shè)計(jì)方式：分組課外利用ads軟件進(jìn)行設(shè)計(jì)。 1.3 設(shè)計(jì)時(shí)間：第一周至第十七周。 1.4 帶阻濾波器中心頻率：6GHz；相對(duì)帶寬：9%；帶內(nèi)波紋： <0.2dB。 1.5 濾波器阻帶衰減>25dB；在頻率5.5GHz和6.5GHz處， 衰 減<3dB；輸入輸出阻抗：50Ω。 2．微帶短截線帶阻濾波器的理論基礎(chǔ) 當(dāng)頻率不高時(shí)，濾波器主要是由集總元件電感和電容構(gòu)成，但當(dāng)頻率高于500Mz時(shí)，濾波器通常由分布參數(shù)元件構(gòu)成，這是由于兩個(gè)原因造成的，其一是頻率高時(shí)

3、電感和電容應(yīng)選的元件值小，由于寄生參數(shù)的影響，如此小的電感和電容已經(jīng)不能再使用集總參數(shù)元件；其二是此時(shí)工作波長(zhǎng)與濾波器元件的物理尺寸相近，濾波器元件之間的距離不可忽視，需要考慮分布參數(shù)效應(yīng)。我們這次設(shè)計(jì)采用短截線方法，將集總元件濾波器變換為分布參數(shù)濾波器，其中理查德變換用于將集總元件變換為傳輸段，科洛達(dá)規(guī)則可以將各濾波器元件分隔。 2.1 理查德變換 通過理查德變換，可以將集總元件的電感和電容用一段終端短路和終端開路的傳輸線等效。終端短路和終端開路傳輸線的輸入阻抗具有純電抗性，利用傳輸線的這一特性，可以實(shí)現(xiàn)集總元件到分布參數(shù)元件的變換。 在傳輸線理論中，終端短路傳輸線的輸入阻抗為：

4、 = （1.0） 式中 當(dāng)傳輸線的長(zhǎng)度 = 時(shí) （1.1） 將式（1.1）代入式（1.1），可以得到 （1.2） 式中 （1.3） 稱為歸一化頻率。 終端短路的一段傳輸線可以等效為集總元件電感，等效關(guān)系為

5、 （1.4） 式中 S = j （1.5） 稱為理查德變換。 同樣，終端開路的一段傳輸線可以等效為集總元件的電容。終端開路傳輸線的輸入導(dǎo)納為 （1.6） 式中 S = j 為理查德變換。 前面將電感和電容用一段傳輸線等效時(shí)，傳輸線的長(zhǎng)度選擇為 ，這樣的選擇有個(gè)好處，因?yàn)辄c(diǎn)f = S = j = j1 （1.7） 這適合將集總元件低通濾波器原型轉(zhuǎn)換為由傳輸線構(gòu)成的低通濾波器，這時(shí)低通濾波器原型的電感值與終端

6、短路傳輸線的歸一化特性阻抗值相等，低通濾波器原型的電容值與終端開路傳輸線的歸一化特性導(dǎo)納值相等。 當(dāng)傳輸線的長(zhǎng)度 時(shí)，這種選擇適合將集總元件低通濾波器原型轉(zhuǎn)換為由傳輸線構(gòu)成的帶阻濾波器。所以我們?cè)谧鲈O(shè)計(jì)時(shí)用的傳輸線的長(zhǎng)度 為 。 2.2 科洛達(dá)規(guī)則 科洛達(dá)規(guī)則是利用附加的傳輸線段，得到在實(shí)際上更容易實(shí)現(xiàn)的濾波器。利用科洛達(dá)規(guī)則既可以將串聯(lián)短截線變換為并聯(lián)短截線，又可以將短截線在物理上分開。附加的傳輸線段稱為單位元件。 3 設(shè)計(jì)步驟 3.1 ADS簡(jiǎn)介 ADS（Advanced Design System）電子設(shè)計(jì)自動(dòng)化軟件為美國(guó)Agilent Technol

7、ogies公司的產(chǎn)品，該軟件的功能包含時(shí)域電路模擬（SPICE－like Simulation）、頻域電路模擬（HarmonicBalance Linear Analysis）、電磁模擬（EM Simulation）、通信系統(tǒng)模擬（Communication SystemSimulation）、數(shù)字信號(hào)處理設(shè)計(jì)（DSP）等。此外和多家芯片廠商合作建立ADS Design Kit及Model File供設(shè)計(jì)人員使用。使用者可以利用Design Kit及軟件模擬功能進(jìn)行通信系統(tǒng)的設(shè)計(jì)、規(guī)劃與評(píng)估，以及MMIC／RFIC、類比與數(shù)位電路設(shè)計(jì)。除上述的設(shè)計(jì)模擬功能外，ADS也提供輔助設(shè)計(jì)功能，如Des

8、ign Guide是以范例及指令方式示范電路或系統(tǒng)的設(shè)計(jì)規(guī)劃流程，而Simulation Wizard是以步驟式界面進(jìn)行電路設(shè)計(jì)與分析。ADS還能提供與其他設(shè)計(jì)模擬軟件（如SPICE、Mentor Graphics的ModelSim、Cadence的NC-Verilog、Mathworks的MATLAB等）做Co－Simulation，加上豐富的元件／應(yīng)用模型庫及量測(cè)／驗(yàn)證儀器間的連接功能，將增加電路與系統(tǒng)設(shè)計(jì)的方便性、速度與精確性。它提供優(yōu)秀的頻率模式和混合模式電路仿真器，可以模擬整個(gè)通信信號(hào)通路，完成從電路到系統(tǒng)的各級(jí)仿真。它把廣泛的經(jīng)過驗(yàn)證的射頻、混合信號(hào)和電磁設(shè)計(jì)工具集成到一個(gè)靈活的環(huán)

9、境中。　　ADS采用自頂至底的設(shè)計(jì)和自底至頂?shù)尿?yàn)證方法，將系統(tǒng)設(shè)計(jì)和驗(yàn)證時(shí)間降到最少。它具有DSP、RF和EM協(xié)同仿真能力，從而能在系統(tǒng)級(jí)設(shè)計(jì)中高效率地分配和優(yōu)化系統(tǒng)性能。完成系統(tǒng)建模后，就可用實(shí)際RE和DSP電路設(shè)計(jì)替代行為模型，評(píng)估它們對(duì)性能的影響。當(dāng)任何一級(jí)仿真結(jié)果不理想時(shí)，都必須回到原理圖中重新進(jìn)行優(yōu)化，并再次進(jìn)行仿真，直到仿真結(jié)果滿意為止，這樣可以保證實(shí)際電路與仿真電路的一致性。 ADS可以為電路設(shè)計(jì)者提供進(jìn)行模擬、射頻與微波等電路和通信系統(tǒng)設(shè)計(jì)的仿真分析方法，其提供的仿真分析方法大致可以分為時(shí)域仿真、頻域仿真、系統(tǒng)仿真和電磁仿真。 3.2 初步設(shè)計(jì)過程 利用微帶短截線帶阻濾波

10、器的理論基礎(chǔ)，可以方便地設(shè)計(jì)出符合技術(shù)指標(biāo)的微帶短截線濾波器。下面我們用ADS設(shè)計(jì)并仿真微帶短截線帶阻濾波器的原理圖，。 微帶短截線帶阻濾波器的設(shè)計(jì)指標(biāo)如下： 中心頻率：6GHz；相對(duì)帶寬：9%；帶內(nèi)波紋： <0.2dB。 濾波器阻帶衰減>25dB；在頻率5.5GHz和6.5GHz處， 衰減<3dB；輸入輸出阻抗：50Ω。 3.2.1創(chuàng)建原理圖 啟動(dòng)ADS軟件創(chuàng)建一名為Filter_Stubl的原理圖。 3.2.2 利用ADS的工具tools完成對(duì)微帶線的計(jì)算 利用ADS提供的工具tools，可以進(jìn)行微帶線物理尺寸和電參數(shù)之間的數(shù)值計(jì)算，若給定微帶線的特性阻抗和電長(zhǎng)度，可

11、以計(jì)算微帶線的寬度。 （1） 設(shè)置微帶線參數(shù)。 在【Microstrip Substrate】對(duì)話框中進(jìn)行設(shè)置，設(shè)置好后在原理圖中有： （2） 在微帶線元件面板上，選擇一個(gè)微帶線MLIN，插入原理圖的畫圖區(qū)。 （3） 在畫圖區(qū)中選中微帶線MLIN,再選擇【tools】調(diào)出【LineCalc】 計(jì)算窗口。 （4） 在【LineCalc】計(jì)算窗口，設(shè)置： 將頻率Freq 設(shè)置為 6 GHz 將微帶線的特性阻抗設(shè)置為 70.7 Ohm 將微帶線的長(zhǎng)度相移設(shè)置為 90度 點(diǎn)擊【Synthesize】按鈕可計(jì)算出 微帶線的寬度 W =1.458mm 和微帶線的長(zhǎng)度 L

12、= 8.457mm 。 （5） 在【LineCalc】計(jì)算窗口，繼續(xù)計(jì)算 將頻率Freq 設(shè)置為 6 GHz 將微帶線的特性阻抗設(shè)置為 50 Ohm 點(diǎn)擊【Synthesize】按鈕可計(jì)算出微帶線的寬度 W = 2.647mm （6） 在原理圖畫圖區(qū)中，計(jì)算終端開路的微帶線MLOC. （7） 在【LineCalc】計(jì)算窗口，設(shè)置： 將頻率Freq 設(shè)置為 6 GHz 將微帶線的特性阻抗設(shè)置為 170.7 Ohm 將微帶線的長(zhǎng)度相移設(shè)置為 90度 點(diǎn)擊【Synthesize】按鈕可計(jì)算出 微帶線的寬度 W = 0.093mm 和微帶線的長(zhǎng)度 L =9.133mm 。

13、 （8） 在【LineCalc】計(jì)算窗口，繼續(xù)計(jì)算 將頻率Freq 設(shè)置為 6 GHz 將微帶線的特性阻抗設(shè)置為 60.4 Ohm 將微帶線的長(zhǎng)度相移設(shè)置為 90度 點(diǎn)擊【Synthesize】按鈕可計(jì)算出微帶線的寬度 W = 1.940mm和微帶線的長(zhǎng)度 L =8.455mm 。 （9） 通過上述計(jì)算得到的數(shù)據(jù)，是微帶短截線帶阻濾波器的尺寸。 3.2.3 設(shè)計(jì)原理圖 （1）保留前面設(shè)置的微帶線參數(shù)，刪除原理圖中的一個(gè)微帶線MLIN。 （2）在原理圖的元件面板列表上，選擇微帶線【Tlines-Microstrip】元件面板上出現(xiàn)與微帶線對(duì)應(yīng)的元件圖標(biāo)。在微帶線元件面板上

14、，選擇微帶線MLIN，4次插入到原理圖中，并做如下設(shè)置： （3）在微帶線元件面板選擇微帶線的T形結(jié)MTEE，3次插入到原理圖中，并做如下設(shè)置： （4）在微帶線元件面板，選擇終端開路的微帶線MLOC,3次插入原理圖中，并做如下設(shè)置： （5）在S參數(shù)仿真元件面板上，選擇負(fù)載終端Term，2次插入原理圖中，并讓兩個(gè)負(fù)載均接地。 （6）應(yīng)用連接工具，將MTEE , MLOC，Term和 MLIN 相連如下圖： 3.2.4 原理圖仿真 （1）在S 參數(shù)仿真元件面板上，選擇S參數(shù)仿真控件SP,插入到原理圖中，并設(shè)置如下： （2）對(duì)

15、微帶短截線帶阻濾波器的原理圖仿真。 （3）數(shù)據(jù)顯示，結(jié)果如下： （4）對(duì)比設(shè)計(jì)指標(biāo)發(fā)現(xiàn)此設(shè)計(jì)在多個(gè)方面存在不足，如：中心頻率沒有正好落在6GHz，M1和M2點(diǎn)的衰減又過大 3.3 優(yōu)化設(shè)計(jì)過程 （1）由于3.2.4（3）圖中曲線不滿足技術(shù)指標(biāo)，需要調(diào)整原理圖，下面采用優(yōu)化方法調(diào)整原理圖。在優(yōu)化仿真之前，先設(shè)置變量，然后再添加優(yōu)化控件和目標(biāo)控件。 （2） 修改S參數(shù)仿真控件中微帶線段的取值方式，將微帶線段導(dǎo)體帶的寬度W設(shè)置為變量。再對(duì)原理圖中TL2和TL3進(jìn)行設(shè)置如下： TL2 的導(dǎo)體寬度設(shè)置為 W = x1 mm TL3的導(dǎo)體寬度設(shè)置為 W =

16、 x1 mm （3）設(shè)置T形結(jié)Tee1，Tee2，Tee3如下（單位mm）： Tee1 設(shè)置為 W1=2.647 W2=x1 W3=x2 Tee2 設(shè)置為 W1=x1 W2=x1 W3=x3 Tee3 設(shè)置為 W1=x1 W2=x2.647 W3=x2 （4）設(shè)置終端開路的微帶線MLOC 如下： 微帶線TL5的寬度設(shè)置為 W = x2 mm 微帶線TL6的寬度設(shè)置為 W = x3 mm 微帶線TL7的寬度設(shè)置為 W = x2 mm （5）在原理圖的工具欄，選擇變量【var】按鈕，插入原理圖中，雙擊VAR，打開【Vari

17、ables and Equations】對(duì)話框，在對(duì)話框中分別對(duì)x1，x2，x3進(jìn)行設(shè)置 其結(jié)果如下： （6）在原理圖的元件面板列表上，選擇優(yōu)化元件【Optim/Stat./yield/DOE】項(xiàng)，在優(yōu)化的元件面板上，選擇優(yōu)化控件Optim插入原理圖的畫圖區(qū)，并選擇目標(biāo)控件Goal插入原理圖的畫圖區(qū)，共4個(gè)。 （7）雙擊Optim ，打開【Nominal Optimization】窗口，在其中設(shè)置優(yōu)化控件，設(shè)置優(yōu)化控件的步驟如下： 選擇隨機(jī)Random 優(yōu)化方式 優(yōu)化次數(shù) 400 次，其余保持默認(rèn)狀態(tài)。 （9） 分別設(shè)置Goal1，Goal2，Goal3，Go

18、al4 控件，結(jié)果如下： （10） 點(diǎn)擊仿真【Simulate】圖標(biāo)，運(yùn)行仿真，等仿真結(jié)束后，選【Simulate/Update Optimization Values】命令，將優(yōu)化后的值保存在原理圖中。 （11） 數(shù)據(jù)結(jié)果顯示： 3.4 對(duì)比結(jié)果 查看優(yōu)化后的曲線圖可知： 在5.5GHz 處， 在 6 GHz 處， 在 6.6GHz處， 這組數(shù)據(jù)比起優(yōu)化前的要好的多了，以上數(shù)據(jù)滿足了設(shè)計(jì)要求的技術(shù)指標(biāo)。 4 心得體會(huì) 這次課程設(shè)計(jì)總的來說不是特別容易，在課

19、堂上雖然學(xué)了不少的理論知識(shí)，可當(dāng)真正實(shí)踐的時(shí)候就發(fā)現(xiàn)自己懂的太少了，這次的仿真軟件完全是自學(xué)的，自己圖書館查資料，上網(wǎng)找資料，在查找和閱讀中確實(shí)學(xué)到挺多知識(shí)，也對(duì)ADS的仿真過程以及帶阻濾波器的原理有了更深刻的理解，在設(shè)計(jì)過程中遇到不少的問題，但都在我們組員的共同努力下找到解決辦法，大家共同努力，共同進(jìn)步，通過這次課程設(shè)計(jì)更加體會(huì)到實(shí)踐對(duì)于理論的重要性，平時(shí)基本都是上課，實(shí)踐的機(jī)會(huì)很少，以后應(yīng)該加強(qiáng)這方面的練習(xí)。 5.參考文獻(xiàn) 1. 《電磁場(chǎng)與微波技術(shù)》 ----------------------人民郵電出版社 2. 《射頻電路理論與設(shè)計(jì)》--------------------人

20、民郵電出版社 3. 《ads應(yīng)用詳解》 -----------------------------人民郵電出版社 4. 網(wǎng)絡(luò)所搜 g an employment tribunal clai Employment tribunals sort out disagreements between employers and employees. You may need to make a claim to an employment tribunal if: you dont agree with the disciplinary action your employer

21、 has taken against you your employer dismisses you and you think that you have been dismissed unfairly. For more information about dismissal and unfair dismissal, seeDismissal. You can make a claim to an employment tribunal, even if you haventappealedagainst the disciplinary action your employer

22、 has taken against you. However, if you win your case, the tribunal may reduce any compensation awarded to you as a result of your failure to appeal. Remember that in most cases you must make an application to an employment tribunal within three months of the date when the event you are complaining

23、 about happened. If your application is received after this time limit, the tribunal will not usually accept i. If you are worried about how the time limits apply to you, take advice from one of the organisations listed underFurther help. Employment tribunals are less formal than some other courts

24、, but it is still a legal process and you will need to give evidence under an oath or affirmation. Most people find making a claim to an employment tribunal challenging. If you are thinking about making a claim to an employment tribunal, you should get help straight away from one of the organisatio

25、ns listed underFurther help. If you are being represented by a solicitor at the tribunal, they may ask you to sign an agreement where you pay their fee out of your compensation if you win the case. This is known as adamages-based agreement. In England and Wales, your solicitor cant charge you more

26、than 35% of your compensation if you win the case. If you are thinking about signing up for a damages-based agreement, you should make sure youre clear about the terms of the agreement. It might be best to get advice from an experienced adviser, for example, at a Citizens Advice Bureau. To find you

27、r nearest CAB, including those that give advice by e-mail, click onnearest CAB. For more information about making a claim to an employment tribunal, seeEmployment tribunals. The (lack of) air up there Watch mCayman Islands-based Webb, the head of Fifas anti-racism taskforce, is in London f

28、or the Football Associations 150th anniversary celebrations and will attend Citys Premier League match at Chelsea on Sunday. "I am going to be at the match tomorrow and I have asked to meet Yaya Toure," he told BBC Sport. "For me its about how he felt and I would like to speak to him first to find

29、 out what his experience was." Uefa hasopened disciplinary proceedings against CSKAfor the "racist behaviour of their fans" duringCitys 2-1 win. Michel Platini, president of European footballs governing body, has also ordered an immediate investigation into the referees actions. CSKA said they we

30、re "surprised and disappointed" by Toures complaint. In a statement the Russian side added: "We found no racist insults from fans of CSKA." Age has reached the end of the beginning of a word. May be guilty in his seems to passing a lot of different life became the appearance of the same day; May be

31、 back in the past, to oneself the paranoid weird belief disillusionment, these days, my mind has been very messy, in my mind constantly. Always feel oneself should go to do something, or write something. Twenty years of life trajectory deeply shallow, suddenly feel something, do it. 　　一字開頭的年齡已經(jīng)到了尾聲

32、。或許是愧疚于自己似乎把轉(zhuǎn)瞬即逝的很多個(gè)不同的日子過成了同一天的樣子；或許是追溯過去，對(duì)自己那些近乎偏執(zhí)的怪異信念的醒悟，這些天以來，思緒一直很凌亂，在腦海中不斷糾纏?？傆X得自己自己似乎應(yīng)該去做點(diǎn)什么，或者寫點(diǎn)什么。二十年的人生軌跡深深淺淺，突然就感覺到有些事情，非做不可了。 The end of our life, and can meet many things really do? 　　而窮盡我們的一生，又能遇到多少事情是真正地非做不可？ During my childhood, think lucky money and new clothes are necessary for

33、 New Year, but as the advance of the age, will be more and more found that those things are optional; Junior high school, thought to have a crush on just means that the real growth, but over the past three years later, his writing of alumni in peace, suddenly found that isnt really grow up, it seems

34、 is not so important; Then in high school, think dont want to give vent to out your inner voice can be in the high school children of the feelings in a period, but was eventually infarction when graduation party in the throat, later again stood on the pitch he has sweat profusely, looked at his thro

35、wn a basketball hoops, suddenly found himself has already cant remember his appearance. 　　童年時(shí)，覺得壓歲錢和新衣服是過年必備，但是隨著年齡的推進(jìn)，會(huì)越來越發(fā)現(xiàn)，那些東西根本就可有可無；初中時(shí)，以為要有一場(chǎng)暗戀才意味著真正的成長(zhǎng)，但三年過去后，自己心平氣和的寫同學(xué)錄的時(shí)候，突然就發(fā)現(xiàn)是不是真正的成長(zhǎng)了，好像并沒有那么重要了；然后到了高中，覺得非要吐露出自己的心聲才能為高中生涯里的懵懂情愫劃上一個(gè)句點(diǎn)，但畢業(yè)晚會(huì)的時(shí)候最終還是被梗塞在了咽喉，后來再次站在他曾經(jīng)揮汗如雨的球場(chǎng)，看著他投過籃球的球框時(shí)，突然間

36、發(fā)現(xiàn)自己已經(jīng)想不起他的容顏。 Originally, this world, can produce a chemical reaction to an event, in addition to resolutely, have to do, and time. 　　原來，這個(gè)世界上，對(duì)某個(gè)事件能產(chǎn)生化學(xué)反應(yīng)的，除了非做不可的堅(jiān)決，還有，時(shí)間。 A persons time, your ideas are always special to clear. Want, want, line is clear, as if nothing could shake his. Also onc

37、e seemed to be determined to do something, but more often is he backed out at last. Dislike his cowardice, finally found that there are a lot of love, there are a lot of miss, like shadow really have been doomed. Those who do, just green years oneself give oneself an arm injection, or is a self-righ

38、teous spiritual. 　　一個(gè)人的時(shí)候，自己的想法總是特別地清晰。想要的，不想要的，界限明確，好像沒有什么可以撼動(dòng)自己。也曾經(jīng)好像已經(jīng)下定了決心去做某件事，但更多的時(shí)候是最后又打起了退堂鼓。嫌惡過自己的怯懦，最終卻發(fā)現(xiàn)有很多緣分，有很多錯(cuò)過，好像冥冥之中真的已經(jīng)注定。那些曾經(jīng)所謂的非做不可，只是青蔥年華里自己給自己注射的一支強(qiáng)心劑，或者說，是自以為是的精神寄托罷了。 At the moment, the sky is dark, the air is fresh factor after just rained. Suddenly thought of blue plaid s

39、hirt; Those were broken into various shapes of stationery; From the corner at the beginning of deep friendship; Have declared the end of the encounter that havent start planning... Those years, those days of do, finally, like youth, will end in our life. 　　此刻，天空是陰暗的，空氣里有著剛下過雨之后的清新因子。突然想到那件藍(lán)格子襯衫；那些被

40、折成各種各樣形狀的信紙；那段從街角深巷伊始的友誼；還有那場(chǎng)還沒有開始就宣告了終結(jié)的邂逅計(jì)劃……那些年那些天的非做不可，終于和青春一樣，都將在我們的人生中謝幕。 Baumgartner the disappointing news: Mission aborted. r plays an important role in this mission. Starting at the ground, conditions have to be very calm -- winds less than 2 mph, with no precipitation or humidity and l

41、imited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commerc

42、ial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence. The supersonic descent could happen as early as Sunda. The weatheThe balloon will slowly drift to the edge of space at 120,000 feet (

43、 Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform. Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will not be like divin

44、g into the deep end of a pool. It will be like he is diving into the shallow end. Skydiver preps for the big jump When he jumps, he is expected to reach the speed of sound -- 690 mph (1,110 kph) -- in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches

45、 the more dense air closer to Earth. But this will not be enough to stop him completely. If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-square-met

46、er) main chute at an altitude of around 5,000 feet (1,524 meters). In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds. Even if everything goes as planned, it wont. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters). cause there 23