本論文發展一個實測平台,其中使用三種通道模型,如COST 207 TU6,China Test 8th(CT8)以及單頻網路(Single Frequency Network;SFN),分別為短、中、長的時間延遲;另外也加入都卜勒效應,如時速60公里和120公里,用來驗證以及評估通道估測演算法。 本文模擬台灣的數位電視訊號,透過儀器發射出實際訊號,經過實際環境做量測,再經由儀器把訊號擷取下來,最後用自己撰寫的程式做訊號的解碼。其中使用兩種通道估測法,一個為基本的通道估測方法,也就是導引訊號通道估測加上內插,而內插法是用線性(linear)內插、立方(spline cubic)內插、兩次快速傅立葉轉換(FFT)內插;另一個為時域下自相關(Frequency Domain Pilot Time Domain Correlation;FPTC)通道估測方法,然後運用以上方法來評估不同的通道模型下與不同的速度下之效能。 驗證結果得到,時域自相關通道估測法加上法蘭克斯窗(Franks window)效能,比只有時域自相關通道估測法還好。時域自相關通道估測演算法效能,在一般通道和較長通道下,比最基本的通道估測演算法較好。線性內插法效能,在一般通道下,比立方內插和兩次快速傅立葉轉換內插較好。立方內差法效能,在較長通道下,比線性內插和兩次快速傅立葉轉換內插較好。
In this thesis, an experimental platform for evaluating the performance of DVB-T system is developed. The parameters applied in Taiwan’s DTV system are used to generate the transmission signal. The Matlab simulated baseband signals are modulated by Angilent E4438C and emitted through an antenna. At the receiving side, the radiation signals are captured and down converted by Tectronix RSA 6114A and decoded by developed Matlab code. Three kinds of channel models, TU6, CT8, and SFN, with joined Doppler effects are used to verify and estimate the performance of channel estimation algorithms and interpolation methods. Base on the experimental results, the time domain correlation channel estimation method FPTC (Frequency Domain Pilot Time Domain Correlation) has better performance than traditional one tape equalization method. Besides, utilizing Franks window and FPTC channel estimation has good performance to compensate the Doppler effects. Moreover, the linear interpolation has much stable BER performance than FFT interpolations or cubic spline interpolation in most of the case. The proposed experimental platform can be used to evaluate the performance of developed algorithms or signal processing methods for improving the quality of DVB-T receivers. As a result of this thesis, we also found that further research on channel estimation and filtering algorithms are necessary to improve the performance of DVB-T receivers in high speed or long echoes’ environment.