應用於數位電視廣播系統之低複雜度頻率同步化設計

Abstract

在本論文中，我們提出了一個應用於數位電視廣播系統的低複雜度載波頻率同步化設計。此同步化設計由兩組偵測機制及一組追蹤迴路組成。與傳統的演算法相比，我們所提出的小數倍載波頻率漂移偵測機制可以有效的對抗多重路徑延遲造成的干擾，並且在均方根錯誤可達到0.25~7.8分貝的信號雜訊比改進。在整數倍載波頻率漂移偵測機制方面，我們所提出的二階段架構可以有效的減少偵測範圍以降低運算複雜度。此外，為了偵測正確的整數倍載波頻率漂移值，我們提出了兩種低複雜度的演算法，在不影響整體系統效能的前提之下，相較於傳統的演算法可以減少超過80%以上的乘法次數。提出的三階段載波頻率漂移追蹤迴路亦可有效的降低殘留的誤差。利用我們所提出的低複雜度載波頻率同步化設計，對整體數位電視廣播系統平台而言，在嚴重的傳輸環境包括Rayleigh衰減通道、杜普勒頻率70赫茲、取樣頻率漂移百萬分之20、載波頻率漂移百萬分之92.14情況下，載波頻率同步化誤差造成的訊號雜訊比損失仍小於0.2分貝。基於我們所提出的低複雜度載波頻率同步化設計，在2005年6月，我們使用0.18微米製程實現了數位電視廣播系統基頻接收器的晶片設計。

In this thesis, a low complexity carrier frequency offset (CFO) synchronization scheme is proposed for Digital Video Broadcasting-Terrestrial/Handheld (DVB-T/H) system, which comprises two acquisition strategies and a tracking loop. The proposed fractional CFO acquisition algorithm can overcome the distortion caused by multipath delay spread and achieves 0.25~7.8dB gain in RMSE compared with the conventional approach. A 2-stage scheme is proposed for the integral CFO acquisition to reduce the search range. Besides, two low complexity algorithms are also proposed to detect the accurate integral CFO value and save more than 80% of number of multiplication without any performance loss to the overall system compared with the conventional approach. The proposed three stage CFO tracking loop can reduce the residual CFO error effectively. The SNR loss due to the proposed CFO synchronization scheme of the overall DVB-T/H baseband receiver system is less than 0.2dB even in severe channel distortion including Rayleigh channel, Doppler spread 70Hz, CFO 92.14ppm (10.33 subcarrier spacing) and sampling clock offset 20ppm. Based on the proposed low complexity CFO synchronization scheme, a DVB-T/H baseband receiver is implemented with 0.18μm cell library and tapped out in Jun. 2005.