為提升虛擬儀器傳輸速率與實時性能，擴(kuò)展監(jiān)測范圍，在VC的軟件平臺上設(shè)計了一種全功能虛擬示波器。與傳統(tǒng)虛擬示波器相比，該系統(tǒng)采用嵌入式系統(tǒng)完成信號采集，采用工業(yè)以太網(wǎng)為傳輸介質(zhì)，通過線性插值算法和多線程編程思想，實現(xiàn)波形顯示、參數(shù)計算、頻譜分析以及波形存儲及回放功能。實驗結(jié)果表明，該虛擬示波器可以實現(xiàn)20 kHz采樣頻率下的波形精確顯示，達(dá)到預(yù)期的各項指標(biāo)。
Abstract:
o enhance the transfer rate and real-time of virtual instrument performance， expand scope of monitoring， this paper uses the VCs software platform to design a fully functional virtual oscilloscope. Compared with traditional virtual oscilloscope， this system adopts the embedded system to complete the data acquisition， industrial Ethernet as the transmission medium used by the linear interpolation algorithm and multi-threaded programming ideas， namely to achieve waveform display， parameter calculation， spectrum analysis and waveform storage and playback. Experimental results show that the virtual oscilloscope can accurately display the waveform with 20kHz sampling frequency， and achieve the desired targets.
This paper investigates the design of joint frequency
offset and carrier phase estimation of a multi-frequency time division
multiple access (MF-TDMA) demodulator that is applied to
a digital video broadcasting—return channel system via satellite
(DVB-RCS). The proposed joint estimation algorithm is based on
the interpolation technique for two correlation values in the frequency
and phase domains. This simple interpolation technique
can significantly improve frequency and phase resolution capabilities
of the proposed technique without increasing the number of
the correlation values. In addition, the overall block diagram of a
digital communications receiver for DVB-RCS is presented, which
was designed using the proposed estimation algorithms.
Index Terms—Carrier phase estimation, DVB-RCS, frequency
offset estimation, interpolation, joint estimation, MF-TDMA.
There are numerous MATLAB m-files included in this software package. Thus, the the authors have bundled all files and sample data in a *.zip file (KTHorb.zip). The Readme.txt file describes the directories created when the .zip file is unpacked. The file Matlab_implementation.doc (or Matlab_implementation.txt) describes some of the classes and methods included in the package for GPS satellite orbit interpolation.
PNG開放源接口 The interface has
been designed to be as simple and intuitive as possible. It supports plotting and reading in the RGB (red, green,
blue), HSV (hue, saturation, value/brightness) and CMYK (cyan, magenta, yellow, black) colour spaces, basic
shapes, scaling, bilinear interpolation, full TrueType antialiased and rotated text support, bezier curves, opening
existing PNG images and more.
DFT(Discrete Fourier Transformation)是數(shù)字信號分析與處理如圖形、語音及圖像等領(lǐng)域的重要變換工具，直接計算DFT的計算量與變換區(qū)間長度N的平方成正比。當(dāng)N較大時，因計算量太大，直接用DFT算法進(jìn)行譜分析和信號的實時處理是不切實際的。快速傅立葉變換(Fast Fourier Transformation，簡稱FFT)使DFT運算效率提高1～2個數(shù)量級。其原因是當(dāng)N較大時，對DFT進(jìn)行了基4和基2分解運算。FFT算法除了必需的數(shù)據(jù)存儲器ram和旋轉(zhuǎn)因子rom外，仍需較復(fù)雜的運算和控制電路單元，即使現(xiàn)在,實現(xiàn)長點數(shù)的FFT仍然是很困難。本文提出的FFT實現(xiàn)算法是基于FPGA之上的，算法完成對一個序列的FFT計算，完全由脈沖觸發(fā)，外部只輸入一脈沖頭和輸入數(shù)據(jù)，便可以得到該脈沖頭作為起始標(biāo)志的N點FFT輸出結(jié)果。由于使用了雙ram，該算法是流型(Pipelined)的，可以連續(xù)計算N點復(fù)數(shù)輸入FFT，即輸入可以是分段N點連續(xù)復(fù)數(shù)數(shù)據(jù)流。采用DIF(Decimation In Frequency)-FFT和DIT(Decimation In Time)-FFT對于算法本身來說是無關(guān)緊要的，因為兩種情況下只是存儲器的讀寫地址有所變動而已，不影響算法的結(jié)構(gòu)和流程，也不會對算法復(fù)雜度有何影響。
