- 學位論文
利用繪圖法計算多組射頻訊號之取樣頻率
Calculation of Sampling Frequency for Multiple RF Signals By Using Graphical Method
摘要
帶通取樣在對於射頻訊號的降頻上面非常有效。一般來說，取樣理論上的Nyquist rate 為兩倍的最高頻，但當一個射頻訊號的載波頻率很高的話，則取樣頻率也會變的非常高，不符合實務上的要求，故無法實現軟體無線電的架構，然而若利用帶通取樣的技巧，則得到的取樣頻率可以比兩倍的最高頻還要降低許多。 由於訊號在廣義上有分單旁波帶與雙邊帶兩種型態，所以單旁波帶與雙邊帶的取樣頻率範圍的算法也不一樣。目前對於多個射頻訊號的取樣頻率的計算有幾種方法法，利用取樣後頻譜的位置關係與順序，來推導出能夠使多組訊號同時可行的取樣頻率，也有利用訊號的參數來取得訊號的取樣頻率範圍再求其交集的方法。 在本論文中，我們使用一個簡單的觀念，首先，先算出其中一個射頻訊號的取樣頻率範圍，接著再與下一個射頻訊號的取樣頻率範圍取交集，接著利用作圖方法將圖形重疊處去除，最後剩下的頻率範圍即為兩個射頻訊號的共同取樣頻率的範圍，這樣的方法也適用在任意多個射頻訊號。
並列摘要
The bandpass sampling is useful for downconversion of RF signals. Generally, the sampling frequency must be larger than in nyquist theory. If the carrier frequency with RF signals is very high, then the sampling frequency will be not feasible to practice. It doesn’t conform to the practice requirement with the software defined radio. In bandpass sampling theory, the sampling frequency is lower than Nyquist rate. There have two kinds of bandpass sampling that complex sampling and real sampling. In this paper, we discussed how to find of multiple RF complex signals and real signals. Today, there have several ways to find the sampling frequency of multiple RF signals. In this paper，we implement the graphic algorithm in matlab by [2]. First one, figure out the RF signal sampling frequency range and take the intersection with the next sampling frequency range. Finally, use the graphic method to remove the graphics overlap. The result by using graphic method we can find the valid sampling frequency with two RF signals easily. This algorithm is also applies to any number of RF real signals or complex signals.