基于聲卡的虛擬信號發(fā)生器的設(shè)計外文翻譯

1、本科畢業(yè)設(shè)計（論文）外文翻譯浙江師范大學(xué)本科畢業(yè)設(shè)計(論文)外文翻譯譯文：軟件為計量大的特征性PC聲卡作者：Jan Saliga 和 Linus Michaeli 1電子通訊系，高冰大學(xué)摘要：論證了一種虛擬儀器軟件，使得簡單而快速的性能測試和計量特征的任何PC機在波形記錄的應(yīng)用。除了在時間和譜域?qū)τ涗浶盘柲Ｊ降挠^察，軟件直接計算各種各樣輸入模擬通道的基本計量參數(shù)，例如，根據(jù)1057和1241和 DYNAD的IEEE標準：有效位的數(shù)量，總諧波失真，總諧波失真加噪聲，信噪比等。在確定模型參數(shù)進行的時間以及在光譜領(lǐng)域比較所取得的結(jié)果。在軟件開發(fā)LabWindows/CVI（C語言）和實行的低層次的W

2、in32API多媒體功能。作者的意圖是應(yīng)用軟件進行計算機部件供應(yīng)商,為教育示范的ADC測試原理文章還包括了幾個例子，取得了有趣的結(jié)果從測試一些PC聲卡和實用的作者的經(jīng)驗，從個人電腦聲卡的測試。關(guān)鍵詞：PC聲卡；波形記錄儀測試；ADC的動態(tài)測試；虛擬儀器軟件文章大綱1. 介紹2. 動態(tài)測試方法進行波形記錄儀基于插板3. 聲卡為波形記錄儀4. 測試軟件和安裝特點5. 實例測試結(jié)果的實現(xiàn)6. 結(jié)論參考1.介紹聲卡,有時也被稱為“錄音機”，同時錄音機經(jīng)常被用于許多計算機(PC)的功能。它們可以被認為是他們的“標準”音頻(模擬)接口。通常聲卡比多功能機機和工業(yè)數(shù)據(jù)采集插板便宜10到100倍。另一方面，模

3、擬輸入和輸出參數(shù)宣布由供應(yīng)商，如至少16位模擬至數(shù)字和數(shù)字到模擬轉(zhuǎn)換器（ADC和DAC），決議的可能性表示這樣的聲卡生成低成本，低頻率的數(shù)據(jù)采集系統(tǒng)，可以從化學(xué)，壓力，振動等傳感器的信號。建立了完善的聲卡的頻率帶寬可以延長直流或半直流信號通過應(yīng)用菜刀，或者由在PC卡輸入數(shù)字調(diào)制解調(diào)其次放大器。這些思想，以及在同行業(yè)中的挑戰(zhàn)，促使作者進行模擬信號錄音通道一些測試根據(jù)IEEE標準1057和1241和DYNAD草稿中的實例驗證聲卡的應(yīng)用可能性表示的大不相同過。新的專有虛擬儀器（VI）軟件開發(fā)，必須進行實驗和測試。2動態(tài)測試方法進行波形記錄儀基于插板標準的測試方法進行波形記錄儀通常是眾所周知的，他們也

4、帶出一個全面的形式IEEE性病。10571。目前，新的，即將被公認標準IEEE性病。12412，3DYNAD來與一些新的理念和測試步驟進行更詳細的討論。此外，很多研究者已經(jīng)提出了許多觀點和方法來解決 AD 和 DA 的轉(zhuǎn)換測試問題，對于那些觀點的信息反饋和調(diào)查正在廣泛地進行4 。經(jīng)過比較各種標準，得知IEEE標準1057數(shù)字化波形錄音器標準是與聲卡測試最接近的一個。然而，這個標準涵蓋了靜態(tài)和準靜態(tài)測試大多主要基于直方圖方法測試，其不足的程序和數(shù)據(jù)處理方法，確定細節(jié)測試ADC的動態(tài)參數(shù),特別在頻域。基于直方圖方法的一般都是非常方便的，因為聲卡的特征性交流耦合對信號輸入的卡片(圖1)。圖1 .典型

5、的功能框圖的模擬信號和數(shù)字電路的信號記錄儀的一部分在音效卡標準都更關(guān)注行動一致并且獨立的可測試,但他們包含了很多的細節(jié)上執(zhí)行和評價的一些動態(tài)測試。特別是DYNAD草案中蘊涵著極其詳細描述數(shù)據(jù)的處理，對評估過程中參數(shù)ADC的動態(tài)光譜域。這些事實，以及有很多相似之處，也和數(shù)字化測試波形記錄儀、導(dǎo)致申請的決定，很多程序詳見DYNAD IEEE性病的評估。1241 ADC的動態(tài)參數(shù)對計算機聲卡測試波形記錄儀中扮演的角色。測試波形記錄儀在PC插件板的形式有一些細節(jié)。PC的內(nèi)部通常是準確的數(shù)字私密的某一輸入信號。提出了開發(fā)和測試方法以及一些實現(xiàn)多功能工業(yè)試驗均為在各種各樣的情形下插板,已發(fā)表在5,第6和第

6、7條。作者們更喜歡動態(tài)測試方法基于FFT頻譜或正弦曲線擬合和確定有效的比特數(shù)(第三)和測試頻率為主要質(zhì)量的特征性參數(shù)的測試板。在軟件領(lǐng)域,兩個通用版本的VI測試軟件已經(jīng)發(fā)展和出版在LabVIEW9和另外的Matlab8。兩個版本的軟件已經(jīng)很普遍assignations-they過程數(shù)據(jù)從任何測量記錄在一個文件時,他們不包含任何數(shù)據(jù)采集部分。3聲卡為波形記錄儀一般都是致力于聲卡錄音和玩聲音信號。這一結(jié)果在限制的輸入與輸出頻率,通常用來頻率跨度帶寬從20赫茲到20千赫，避免應(yīng)用靜態(tài)測試方法的應(yīng)用,導(dǎo)致的動態(tài)檢測方法采用正弦輸入測試信號。典型的功能框圖的聲音拼輸入記錄通道圖1顯示的是(10-11和其

7、他的)。模數(shù)轉(zhuǎn)換積分的轉(zhuǎn)換器轉(zhuǎn)換通常雇工作的modes-8在至少兩個精度和16位。 數(shù)據(jù)能被編碼成幾個非線性和線性格式。線性格式(PCM)，這是最適合的格式的性能測試,他被選中在發(fā)達的測試程序。各種各樣的可選的采樣頻率取決于聲卡model-at至少8、11、16和44.1 kHz-are通常所提供的。穩(wěn)定性,而且最終,多普勒頻移的這些頻率通常不被明確地表明在音效卡的使用手冊。Digitising輸入就可以轉(zhuǎn)移的一場模擬多工器。麥克風輸入和一個較不敏感的線錄和麥克風(輔助)輸入是內(nèi)置在為連接外部模擬信號的來源。音效卡在可能是最經(jīng)常使用的個人電腦與操作系統(tǒng)(OS)Windows 9x / NT /

8、 2000 /我/ XP。任何聲音應(yīng)用在Windows下可以使用一些三個層次的Win32 API多媒體課件的職能,為控制和數(shù)據(jù)轉(zhuǎn)移/從任何Windows兼容的聲卡。MCIWnd最高的窗口類，MCI設(shè)備中間接口，低層音頻接口，應(yīng)用程序使用的最好的可能，需要控制的音頻設(shè)備。4 測試軟件和安裝特點一般安裝所需要的聲音錄音部分射性能測試是非常簡單的(圖2)。它是由一個精確的測試信號發(fā)生器和普通PC機和音效卡計算機機箱的考驗。DS360超低失真的發(fā)電機，斯坦福研究系統(tǒng)與20位DAC和拉力比100分貝是用于測試的設(shè)置。測試的音效卡(ATX)和各種各樣的新老(在)計算機機箱不同萬塊主板和在一些筆記本。圖2

9、設(shè)定了聲卡的測試此安裝必須結(jié)合一個方便的軟件,它必須控制聲音激射測試，收集和處理的記錄的數(shù)據(jù)，以及目前和檔案的結(jié)果。當前通用軟件8-9不包含任何部分的資料收集，他們可以使只有數(shù)據(jù)處理。一個可能的附加變形記錄的數(shù)據(jù)，這可能是由于使用第三方軟件，未知數(shù)據(jù)獲取詳細記錄從一個語音卡在一個非線性的格式，導(dǎo)致這個決定開發(fā)一種新的特殊VI的軟件。該軟件被創(chuàng)造的目的是最大的綜合性在音效卡的測試。它是完全結(jié)合其低層數(shù)據(jù)錄入子程序，它可以作為一個可執(zhí)行文件安裝在任何PC視窗操作系統(tǒng)和正確安裝聲卡包括安裝的Windows兼容的司機。軟件開發(fā)環(huán)境LabWindows /約定保險價值的民族樂器的支持下，軟件開發(fā)工具包(

10、SDK由微軟)，被用來作為主要的software-developing工具。用戶面板被顯示在圖3。圖3 用戶VI前面板的開發(fā)軟件這種軟件能夠使：記錄數(shù)據(jù)從任何聲音卡在標準8/16位和單色和立體聲模式在一個可選的標準的采樣頻率，在線性PCM格式。用戶可以跟上錄音過程和簡單地識別任何問題從文本信息中顯示的窗口。觀想記錄的數(shù)據(jù)，包括為視覺評價,嗡嗡作響,也用來儲存和閱讀記錄的數(shù)據(jù)/從一個文件。在分析記錄數(shù)據(jù)時域：選擇性地的四性能均配件和噪聲功率,有效的枚舉第三位的數(shù)字和其他派生的參數(shù)。真正的采樣頻率估計的0.9%。價值的估計DC測試信號的幅值和相位。分析和可視化的記錄的數(shù)據(jù)在光譜域：計算功率密度譜和

11、功率譜分布函數(shù)。估計基本的諧波，總諧波失真，總諧波失真加噪聲，信噪比第三和其它參數(shù)計算出的功率密度譜。根據(jù)接收到的迭代算法正弦波擬合有點改變，以IEEE標準,因為它的收斂問題。在應(yīng)用算法始于計算正弦適合和相應(yīng)的噪聲功率PN0頻率fn0立足fsamplingsf = fsignal /()高于其估計和fsampling由給定的fsignal通過采樣頻率偏移三藩市< 1。接下來的兩個組合和相應(yīng)的噪聲，PN2權(quán)力(PN1在頻率計算fnk)/(fsamplingsf = fsignal + kfstep)(k = 0、1、2)，在那里fstep0步驟是開始的采樣頻率為最小的PN搜索程序。PNk值

12、比較，無論是fn0降低或fstep在下一次迭代。迭代過程中之間的區(qū)別是停止PNk低于武裝的限制。當然，如果迭代過程中收斂的fsignal評估和fsampling是相當?shù)慕咏麄兇_切的價值觀和三藩市選用適當。5。實例測試結(jié)果的實現(xiàn)到目前為止，8個型號的音效卡進行試驗研究。它們可以被分為兩組：PC聲卡上實現(xiàn)主板或在筆記本上?！安寮豹毩⒙暱?。第一個測試模型集成在相對較新的聲音blasters m805lr ATX主板和m807r用PC芯片1213于2000年。Socket-462主板支持的低功耗總線(Socket-A)處理器的速度200或266兆赫。 他們用這些通過VT8363芯片組,它提供了一個

13、4 AGP插槽高度的圖形顯示、中央處理器的即插即用通過固件。主板所建的在同一AC97音頻編解碼器,提供了現(xiàn)代隔水管(AMR)槽來支持音頻和現(xiàn)代的應(yīng)用程序。有一個內(nèi)建的m805lr 10BaseT / 100BaseTX。 賣方指定執(zhí)行AC97具有如下特點:“支持18-bit解碼器ADC和DAC,以及18-bit立體聲全雙工編解碼器”12和13。這兩個樣本,個人計算機芯片和一個m807r m805lr,進行試驗研究。一些結(jié)果在一個取樣頻率的44.1千赫是列在表1和表2以及在圖4和圖5。表1 測試結(jié)果，從第三編解碼器上實現(xiàn)聲音的形式m805lr PC芯片主板:結(jié)果擬合/結(jié)果頻譜全尺寸表(<

14、1K)表2.測試結(jié)果,從第三編解碼器上實現(xiàn)的聲音l807r主板PC芯片全尺寸表(< 1K)圖4 (a)第三依賴測試信號頻率的8和16(*)-(×)-bit單聲道模式m805lr編解碼器在PC上芯片的聲音。(b) 典型的譜在16位模式在PCCHIPS m805lr聲音編碼器(測試頻率是2.1千赫)。圖5 (a)第三依賴測試信號頻率的8和16(*)-(×)-bit單聲道模式m807r編解碼器在PC上芯片的聲音。(b)典型的16位模式譜在PCCHIPS m807r聲音編碼器(測試頻率是認識千赫)。所取得的結(jié)果表明價格之間的差距太大了供應(yīng)商的宣布參數(shù)和真正的問題。特別是在16

15、位模式，最大限度地達到第三價值總是降到10位元m805lr和略多于10位元m807r。此外，依賴急劇減少的第三輸入測試信號的頻率在大約5千赫茲的頻率在m805lr被分配。同時，a / d轉(zhuǎn)換器輸入范圍的偏移量。28846進入midpoint-112代替128,進入32768-was檢測。 它會減低輸入電壓范圍內(nèi)。最后要說明的是更好的價值觀為m807r參數(shù),取得了。它是相當奇怪的,因為它們都主板使用相同的聲音晶片。光譜比較,如圖4和圖5的廣告nonharmonics低得多的m807r扭曲的。改變采樣頻率并沒有導(dǎo)致任何改變都克服0.1-bit l80x板。進一步的測試聲音的CM8330射來的正是建

16、立在芯片14集成在主板m559在老用PC芯片。第一次試驗,結(jié)果表明一個非常低素質(zhì)的聲音并導(dǎo)致射來的錄音機部分取消任何下一步的測試。這個原因可以看出在圖的局限性。6-the地板在水平測試信號進入62 16000多人,減低了所有的測試質(zhì)量參數(shù)的錄音機厘米,防止聲音晶片8330射來的正確的決定的其他錄音機參數(shù)。圖6 記錄正弦波為16位模式由m55 水平上的限制16,062完全降解CM8330參數(shù)在筆記本上的音效卡，實現(xiàn)進行了測試。最有趣的結(jié)果，取得了TravelMate在筆記本212TX16，宏碁與音頻16位AC 97年立體聲編解碼器。表3和圖7說明其中的一些。表3 結(jié)果從第三編解碼器實施測試的聲音

17、212TX宏碁TravelMate筆記本全尺寸表(< 1K)圖7 .(a)第三測試信號頻率的依賴(*)的8 - 16×單聲道模式(聲音的)-bit宏碁實現(xiàn)TravelMate射來的212TX筆記本。(b)典型的16位模式譜，宏碁實現(xiàn)聲音TravelMate射來的筆記本212TX(測試頻率采樣頻率44100 4.11千赫,赫茲)。(c)詳細的典型譜的16位模式實施的聲音在筆記本宏碁TravelMate射來的212TX 11.11(測試頻率采樣頻率44100赫茲)。所取得的結(jié)果提示,同樣在此之前，一個糟糕的音頻輸入的質(zhì)量檢測筆記本特別是在16位模式。此外，那奇怪的頻譜如圖。7b和c

18、意味著一個想法，即真正的采樣頻率的聲音編解碼器是不同于設(shè)一或者數(shù)字濾波的積分模數(shù)轉(zhuǎn)換器不正確的工作。最后一個例子是“獨立的”插件板聲激射PCI6415通過創(chuàng)造性的技術(shù)。一些實現(xiàn)的結(jié)果顯示在表4和圖8和圖9。在與過去相比,此牌blasters證明聲音輕輕更好的計量參數(shù)。表4。第三依賴測試信號頻率的聲音PCI64射來的圖8。(a)第三測試信號頻率的依賴(*)的8 - 16×單聲道模式(聲音的)-bit射來的一種總線標準64。(b)典型的譜在16位模式(測試頻率聲音拼PCI64 211赫茲，采樣頻率44100赫茲)。圖9。觀察到的聲音失真為輸入信號PCI64會議射來的全尺寸的音頻輸入(輸入

19、頻率21赫茲，采樣頻率44100赫茲)。聲卡的8位模式似乎非常接近理想的結(jié)果就缺超過8位是造成真正的量子化的比較理想的噪聲信號和歸一化的力量是簡化，在大多數(shù)的標準是1 / 12。然而，最大限度地實現(xiàn)價值是在16位模式第三只略微超過12位,這仍然是遠離宣布16位分辨率。而且,如果輸入信號滿足幾乎全尺寸的測試，明顯的音頻輸入非線性失真的觀察記錄的數(shù)據(jù)(見圖9)。測試相同的牌在不同的機器帶來的只有微不足道的差異超過0.5點達到results-not。通常情況下，只有大約0.1一點。這個事實表明主要影響的計量參數(shù)語音卡有卡圖案，不干擾其他的個人計算機的部件。6。結(jié)論開發(fā)的軟件應(yīng)用的測試和評價中幾個聲卡

20、。這似乎是一種非常有用的tool-it使測量和習(xí)得的音效卡，許多復(fù)雜的參數(shù)在較短的時間內(nèi)。開發(fā)的軟件就業(yè)用PC零售商可以導(dǎo)致質(zhì)量的提高和信心的PC組件提供。本軟件也將被用來在教育教學(xué)過程中，電子測量和數(shù)據(jù)采集系統(tǒng)在柯增強的冰科技大學(xué)作為一個示范虛擬儀器的講解和演示的標準ADC測試方法。不同聲卡的測試結(jié)果都表明了從測量的角度上看音質(zhì)較差。在16位模式下尤其明顯。獨立插入式聲卡似乎比主板集成顯卡好一些(好一兩個字節(jié))。電腦內(nèi)部零件似乎比聲卡設(shè)計本身對于測量參數(shù)的干擾要小。種種事實都表明聲卡只能用在不超過10到12個字節(jié)的簡單的系統(tǒng)上。此外，不同聲卡的測量參數(shù)存在著相當大的差異。參考文獻：1 IEE

21、E標準.1057-1994性病,數(shù)字化波形記錄.2 IEEE性病,草案.1241覆蓋.VS022500.3 DYNAD覆蓋,草案,http:/www.fe.up.pt/.3.3 hsm / DYNAD,2001年.4 p . Arpaia Daponte .和p . Cennamo converters-a計量的特征性的模擬/數(shù)字,國家的藝術(shù)。 論文的第三屆國際會議上發(fā)表的A / D轉(zhuǎn)換和先進D / A轉(zhuǎn)換技術(shù)及其應(yīng)用(09/10/1997.Publ.沒有466章)(1999),頁.134-144。 全文通過CrossRef帕斯| |觀點被記錄在斯高帕斯(0).5 m . Pokorny,第五

22、卷,j . Roztocil、抑Haasz由AD-modules測試信號失真。 在:動態(tài)測試,IMEKO研討會論文集,ISSDMI TC-4 98年的今天,意大利那不勒斯隊(1998),頁.889-892.6 m . Pokorny,第五卷,Haasz替代方法的A / D轉(zhuǎn)換質(zhì)量檢測。在:Instrumentaion和測量技術(shù)研討會,99論文集中的第16卷IEEE,意大利的威尼斯.3(1999): 1421-1424.全文通過CrossRef帕斯| |觀點被記錄在斯高帕斯(1)7 r . Holcer,性能測試的一些廣告轉(zhuǎn)換器中嵌入了微控制器。論文IMEKO世界大會的十六,IMEKO 2000

23、年,訴訟,維也納,奧地利(2000年):165-169。8 一、Kollar馬庫斯,正弦波的ADC的手段測試國際比較。在IMEKO:十六,IMEKO 2000年世界大會,訴訟,維也納,奧地利(2000).9 j .布萊爾,Sine-fitting IEEE標準和軟件為1241 1057年.論文的第16次IEEE儀器和測試技術(shù)研討會,頁。/ 99中的3(1999): 1504-1506.全文通過CrossRef帕斯| |觀點被記錄在斯高帕斯(14)10 模擬設(shè)備:廣告1845年16位SoundPort平行端口立體聲編解碼器、產(chǎn)品應(yīng)用手冊,模擬設(shè)備,1997年.11 OPTi:82C931Plug

24、和演奏聲音控制器、產(chǎn)品應(yīng)用手冊,OPTi,1997年。12 電腦芯片:805lr用戶手冊.13 電腦芯片:807用戶手冊.14 電腦芯片m569用戶手冊.15 (16 ().原文：Software for metrological characterisation of PC sound cardsJán aliga ,and Linus Michaeli 1   Author vitae Department of Electronics and Telecommunications, Technical University of Ko ice, Park K

25、omenského 13, SK-04120, Ko ice, Slovak Republic,Available online 17 September 2002.Abstract：The paper demonstrates a virtual instrument software that enables the performance of simple and fast testing and metrological characterisation of any PC sound card in waveform recorder applications. In a

26、ddition to the visualisation of recorded signal patterns in time and spectral domains, the software directly computes a variety of basic metrological parameters of input analogue channels, e.g. effective number of bits, THD, THD+noise, SINAD, etc., according to IEEE Standards 1057 and 1241 and DYNAD

27、. The parameter determination is performed in time, as well as in spectral, domain to compare the achieved results. The software was developed in LabWindows/CVI (C language) with implementation of low-level Win32 API multimedia functions. The authors' intention is to apply the software for compu

28、ter component vendors and for the educational demonstration of ADC testing principles.The paper also contains a few examples of achieved interesting results from testing some PC sound cards and practical authors' experiences from PC sound card testing.Author Keywords: PC sound card; Waveform rec

29、order test; ADC dynamic test; Virtual instrumentation softwareArticle Outline1. Introduction2. Dynamic test methods for waveform recorders based on plug-in boards3. Sound card as a waveform recorder4. Test software and setup characteristics5. Examples of achieved test results6. ConclusionsReferences

30、1. IntroductionSound cards, sometimes called sound blasters, are very common and are often used as components of many computers (PC) nowadays. They can be considered as their “standard” audio (analogue) interface. Sound cards are much cheaper than multifunction and industrial data acquisition plug-i

31、n boardsusually more than 10100 times.On the other hand, the parameters of analogue inputs and outputs declared by vendors, e.g. at least 16-bit resolution of analogue-to-digital and digital-to-analogue converters (ADCs and DACs), indicate the possibility to apply such a card in low cost and low-fre

32、quency data-acquisition systems acquiring signals from chemical, pressure, vibration and other sensors. The frequency bandwidth of a sound card can be extended on DC or quasi-DC signals by applying a chopper or a modulation amplifier on card input followed by a digital demodulation in the PC. These

33、ideas, as well as the challenge in the industry, led the authors to perform some tests of analogue signal recording channels according to IEEE Standards 1057 and 1241 and DYNAD drafts to verify the application possibilities of sound cards in the examples indicated herein before. New proprietary virt

34、ual instrument (VI) software had to be developed to perform the experiments and tests.2. Dynamic test methods for waveform recorders based on plug-in boardsThe standard test methods for waveform recorders are generally well known, and they were brought out in a comprehensive form in IEEE Std. 1057 1

35、. Nowadays, the new, about to be accepted standards IEEE Std. 1241 2 and DYNAD 3 are coming with some new ideas and test procedures described in more detail. Moreover, many researchers have contributed with lots of ideas and approaches to solve AD and DA converter test problems. Probably the widest

36、survey of those ideas was made in 4.Comparing the standards, IEEE Std. 1057“Standard for digitising waveform recorders”is the closest to the task of sound card testing. However, this standard covers mostly the static and quasi-static tests methods based mainly on the histogram testing and there is a

37、 deficiency of procedure and data processing details on testing and determining the dynamic parameters of ADC especially in the frequency domain. The histogram-based methods are generally not very convenient for sound card characterisation because of the AC coupling on signal input of the cards (Fig

38、. 1).Full-size image (9K)Fig. 1. Typical function block diagram of analogue and digital circuits for signal recorder part in sound cards.View Within ArticleBoth on-coming standards are more focused on testing stand-alone ADCs but they contain much more specific details on execution and evaluation of

39、 some dynamic tests. Particularly, the DYNAD draft contains very detailed descriptions of data processing for estimation of the ADC dynamic parameters in the spectral domain. These facts, as well as many similarities in testing ADCs and digitising waveform recorders, led to the decision to apply man

40、y procedures referred in DYNAD and in IEEE Std. 1241 for evaluation of ADC dynamic parameters on PC sound card testing in the role of waveform recorder.Testing waveform recorders in the form of PC plug-in boards have some specifics. The interior of PC is generally illicit for a precise digitalisatio

41、n of an input signal. The test methods developed and suggested, as well as some achieved test results for multifunction industrial plug-in boards in various circumstances, have been published in 5, 6 and 7. The authors preferred the dynamic test methods based on FFT spectrum or sinusoidal curve fit

42、with determining effective number of bits (ENOB) versus test frequency as the main quality characterisation parameter of the tested board.In the software area, two universal versions of VI test software have been developed and publishedone in LabVIEW 9 and another in Matlab 8. Both versions of softw

43、are have very general assignationsthey process data from any measurement recorded in a file and they do not contain any data acquisition part.3. Sound card as a waveform recorderSound cards are generally dedicated to recording and playing sound signals. This results in a restriction of input and out

44、put frequencies span, usually to the frequency bandwidth from 20 Hz to 20 kHz, which prevents application of the static test methods and leads to the application of the dynamic test methods using the sinusoidal input test signal. The typical function block diagram of sound blaster input recording ch

45、annels is shown in Fig. 1 ( 10 and 11 and others).The analogue-to-digital conversion usually employs sigmadelta converters that can work in at least two precision modes8 and 16 bits. Data can be coded into a few nonlinear and linear formats. The linear format (PCM), which is the most suitable format

46、 for the performance test, was chosen in the developed testing procedure. A variety of optional sampling frequencies depending on the sound card modelat least 8, 11, 22.05 and 44.1 kHzare commonly offered. The stability and, eventually, a frequency shift of these frequencies are not usually explicit

47、ly indicated in sound card manuals. Digitising input may be switched by an analogue multiplexer. A microphone input and a less sensitive line-in (aux) input are built-in for linking external analogue signal sources.Sound cards are probably most often used in PCs with operational systems (OS) Windows

48、 9x/NT/2000/ME/XP. Any sound application under Windows can use some of the three levels of Win32 API multimedia class of functions for controlling and data transferring to/from any Windows-compatible sound card: the highest MCIWnd window class, the middle MCI device-independent interface, the low-le

49、vel audio interface, which is used by applications that need the finest possible control over audio devices.4. Test software and setup characteristicsThe general setup needed for performance testing sound blaster recording part is very simple (Fig. 2). It consists only of a precise test signal gener

50、ator and a common PC with the sound card to be tested in a PC chassis. The ultra low distortion generator DS360 by Stanford Research Systems with 20 bits DAC and THD better than 100 dB was used in the testing setup. The sound cards were tested in various new (ATX) and old (AT) PC chassis with differ

51、ent motherboards and in a few notebooks.Full-size image (3K)Fig. 2. Setup for sound card testing.View Within ArticleThis setup must be integrated with a convenient software, which must control the sound blaster to be tested, collect and process the recorded data, as well as present and archive the r

52、esults. The current general-purpose software 8 and 9 does not contain any part of data collecting and they enable only data processing. A possible additional distortion in the recorded data, which can be caused by using a third-party, unknown in detail recording software acquiring data from a sound

53、card in a nonlinear format, led to the decision to develop a new special VI software.The software was created with the intention of maximal comprehensiveness at sound card testing. It was fully integrated with its low-level data recording subroutines and it can be installed as an executable file in

54、any PC with Windows OS and correctly installed sound card including installation of its Windows-compatible driver. Software development environment LabWindows/CVI by National Instruments, with the support of the Software Development Kit (SDK by Microsoft), was used as the main software-developing to

55、ol. The user panel is shown in Fig. 3.Full-size image (49K)Fig. 3. User front panel of the developed VI software.View Within ArticleThe software enables: Recording data from any sound card in standard 8/16 bits and mono/stereo modes at an optional standard sampling frequency in linear PCM format. Th

56、e user can follow the recording process and simply identify any problem from text messages shown in the message window. Visualisation of recorded data, including zooming for visual assessment, as well as saving and reading recorded data to/from a file. Analysis of recorded data in time domain: Perfo

57、rmance optionally of four- and three-parameter fittings with enumeration of noise power, effective numbers of bits (ENOB) and other derived parameters. Estimation of real sampling frequency. Estimation of DC value, amplitude and phase of test signal. Analysis and visualisation of recorded data in sp

58、ectral domain: Computation of power density spectrum and power spectrum distribution function. Estimation of basic harmonic, THD, THD+noise, ENOB and other parameters calculated from the power density spectrum.The iteration algorithm for the four-parameter sine wave fitting was a bit changed to IEEE standards because of its convergence problem. The applied algorithm starts with computing the sine wave fit and the