Ultra-Wideband IF/LO System of NTU W-band Interferometry Array and One-Bit Digital Spectrometer
Date Issued
2014
Date
2014
Author(s)
Teng, Hsiao-Feng
Abstract
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.
Subjects
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
Type
thesis
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