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Title: | 台大干涉陣列超寬W頻帶中頻及本地震盪器系統與單位元取樣數位頻譜儀 Ultra-Wideband IF/LO System of NTU W-band Interferometry Array and One-Bit Digital Spectrometer |
Authors: | Hsiao-Feng Teng 滕曉峯 |
Advisor: | 闕志鴻 |
Keyword: | 超寬頻,中頻本地震盪器系統,類比光纖傳輸,單一位元取樣,雜訊抖動,頻譜分析儀, Ultra wide-band,IF/LO system,analog optical transceiver,One bit digitization,Noise dithering,Spectrometer,Spectrum Analyzer, |
Publication Year : | 2014 |
Degree: | 博士 |
Abstract: | 台大干涉陣列是設計用來觀測W-band (78-113GHz) SZ效應(SZ-effect),第一階段六套接收機單極化觀測已經於2008年完成。單一位元18GHz頻寬與數位相干器已經使用並驗證其特性。
由於觀測波段涵蓋範圍非常寬頻達到35GHz,因此中頻系統需要將此頻寬分成四個各為8.7GHz次頻段。第一級中頻模組包含一個35GHz全寬頻增益相對平坦且達到25分貝的放大器,此模組同時將訊號分成兩路分送到下一級中頻模組。第二級中頻模組包含兩個次模組,再各自將訊號再分成兩路並且降頻至直流(DC)到8.7GHz。因此,本地震盪器需要產生8.7GHz兩倍、三倍以及九倍諧波,供應中頻模組降頻使用,其中九倍頻本地震盪器訊號載入Walsh函數(Walsh function)送進第一級中頻IQ混波器(IQ Mixer)供作RF降頻使用。每一路降為8.7GHz頻寬之中頻訊號皆以光纖傳送至位於控制室之18GHz單一位元取樣類比數位轉換器(ADC)。每一路光纖皆有驅動器(driver)與等化器(equalizer)補償路徑損失。考慮望遠鏡基座有限的空間,每一套雙極性共計八路輸出都設計在20公分見方的體積內,目的為未來NTU array升級成19個單位準備, 原始設計接下來的訊號要接進數位干涉相關器做干涉分析,現階段我們先建造單一位元超寬頻取樣頻譜儀以展示主要利用雜訊抖動引入與正弦函數變換兩個方法,目前我們具體展示了頻寬17.4GHz的原型機,並且量測了主要的特性,可以證明單位元取樣可以應用在頻譜偵測,並且適合於連續且快速偵測的要求。 NTU-Array is designed for W-band (78-113Ghz) observationthrough SZ-effects. The first-phase operation of the telescope with 6receivers had its first light in 2008 with single-polarization and half thefull bandwidth. The second-phase operation of NTU-Array in Nevada will beginthe dual-polarization, full-band observation in 2010. One-bit sampling at18Ghz and digital correlation are in use in this telescope. Due to the ultrabroadband coverage, the IF system divides the 35GHz full-band into four 8.7GHzsub-bands. The first stage of IF module containing a 35GHz broadband amplifierwith fairly flat-gain performance over 25db gain divides the first-stage IFinto two outputs. The 2nd-stage IF module further divides the two input IFsignals and down-converts them to four basebands of DC-8.7Ghz. An LO modulewith 8.7Ghz input is to generate outputs with x2, x3 and x9 harmonics for thedown-conversion. The Walsh function is injected into the x9 LO throughup-conversion with an IQ mixer. Each IF baseband is transmitted through an optical fiber to the 18Ghz, 1-bit sampling ADC located in the control room.The analog optical link contains a driver and equalizer to compensate for thepath loss.Considering the limited size of the telescope mount, the entire IF/LOsystem of each receiver has a compact size about 20cm cubed. Thisphysical size can be further reduced to fit the future 19-pixel-receiverupgrade of NTU-Array. The original design made the four bands 8.7 GHz signals go into the digital correlator for interferometry correlation. Instead of the digital correlator, a 17.4 GHz one-bit sampling spectrum analyzer is built to demonstrate the working principle for a much faster spectrometer, where noise dithering and sine transformation are two key features of the principle. While the noise dithering can suppress the harmonics of signals, the sine transformation is shown to restore the noise. Measurements of this instrument reveal that the newly proposed novel scheme works as it should, with no technical showstopper for a much faster device. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/57223 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 天文物理研究所 |
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ntu-103-1.pdf Restricted Access | 5.87 MB | Adobe PDF |
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