正交分頻多工（OFDM）系統具有抵抗多重路徑干擾及頻譜使用效率高等優異特性，其中抵抗多重路徑干擾是藉由循環字首（Cyclic prefix）及多載波之特性以達到免除碼字間干擾（ISI）及載波間干擾（ICI），而頻譜使用效率高則是運用多載波正交特性達到的。在循環字首的保護下，多路徑通道對各載波的影響在於其振幅與相位的失真，因此在個子載波之通道等化只需一個複數係數（One-tap）以修正其失真，而其成功要件則在於各子載波之通道頻率響應估測。 本研究中以實現複雜度許可之前提下，針對DVB-T系統進行穩定通道及快速衰落（移動）通道下之通道估測與等化演算法的模擬與硬體設計實現，其中模擬實現結果亦有助於了解OFDM傳收系統規格，如頻段、頻寬、子載波頻率間隔等與通道狀況對接收性能的影響，且針對典型的通道估測採最小平方法搭配線性內插之缺點，並提出插值濾波器之方法改善通道估測之精確度，進一步提升接收機效能。 OFDM systems exhibit superior characteristics in terms of simplicity in combating multi-path transmission and efficiency in spectral utilization. The effects of ICI and ISI arise from the multi-path interference could be successfully eliminated by the insertion of cyclic-prefix and the use of multi-carriers. Furthermore the advantage of spectral efficiency is achieved by orthogonal property. Under the protection of cyclic-prefix, multi-path effect causes distortion of amplitude and phase only. In accordance with the exact channel estimation among each sub-carrier, the distortion could be compensated by one-tap complex coefficients. With the consideration of hardware implementation, the algorithms of the channel estimation and equalization were investigated and simulated for static channels and fast fading channels for DVB-T system. Moreover, the dependence of the receiving performance upon relationships between channel conditions and system specifications, e.g. transmission band, bandwidth, sub-carrier spacing, etc. would be clarified from simulation results. In contrast to the least-square method with linear interpolation for conventional channel estimator, interpolation filter was proposed to estimate the channel response more accurately, and improve the performance of the receiver further.
