基本介紹
- 中文名:一階保持
- 外文名:Frst-order hold
- 縮寫:FOH
- 定義:重建信號的數學模型
簡介,基本的一階保持,延遲一階保持,預測型一階保持,相關條目,
簡介
一階保持(Frst-order hold、FOH)是一種重建信號的數學模型,可以透過傳統的數位類比轉換器(DAC)及稱為積分器的模擬電路完成。一階保持可以將訊號重建為分段線性近似原始訊號的函式。在實務上,像一階保持或零階保持之類的保持電路有其必要性。根據採樣定理,可以將離散後的訊號用狄拉克δ脈衝序列xs(t)表示,再經過低通濾波器即可還原到原始的訊號。不過實務上無法輸出狄拉克δ脈衝序列。利用傳統的數位類比轉換器以及一些線性類比電路就可以重建預測型或是延遲型的一階保持電路。
基本的一階保持
一階保持是利用假想的濾波器或是線性時不變系統,將理想的取樣訊號
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轉換為分段線性的訊號。
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延遲一階保持
延遲一階保持(Delayed first-order hold)有時也稱為因果一階保持(causal first-order hold)和一階保持相同,但輸出會延遲一個取樣周期才輸出,因此會有延遲的分段連續信號
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預測型一階保持
預測型一階保持(predictive first-order hold)和上二一個一階保持的差異較大,預測型一階保持是因果系統的假想線性時不變系統,可以將理論取樣信號
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等效頻率回響為衝激回響的傅立葉變換。
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