基帶

基帶（英語：baseband）是頻率範圍非常窄的訊號，也就是說振幅譜僅在原點（f = 0）附近才是非零的，其他頻率幾乎可以忽略。^[1] 在電信與訊號處理中，基帶訊號是未經載波調制的訊號，即該訊號的頻率範圍沒有任何移位，^[2] 而且頻率很低 - 包含頻帶從接近 0 Hz到更高截止頻率或最大頻寬。

基帶訊號的頻譜，單位頻率的能量 E 作為頻率 f 的函數。總能量是線下的面積。

此條目介紹的是訊號處理的概念。關於無線數碼通訊的訊號處理器，請見「基帶處理器」。

由於基帶訊號是未經載波調制的訊號，在GPS接收機和流動電話等無線數碼通訊領域，基帶訊號有時也泛指已經過射頻前端（英語：Radio Frontend）處理後的訊號。^[3][4]在無線通訊裝置中，來自天線的訊號先經射頻前端（英語：Radio Frontend）的模擬電路接收，然後再轉交給後續的數碼電路進一步處理，而後者就是基帶處理器。^[3][4]在當前中文語境中，手機基帶處理器所帶的韌體也簡稱「基帶」^[5]。

參見

• 解析訊號
• 寬頻
• 窄頻（英語：Narrowband）
• 寬頻 (通訊)（英語：Wideband）

參考文獻

1. Leon W. Couch II. Digital and Analog Communication Systems. Prentice Hall. 1993.
2. B.P. Lathi. Modern Digital and Analog Communication Systems. Holt, Rinehart and Winston. 1983.
3. Christian Piguet. 6: Low-Power Bandband Processors for Communications. Low-Power Processors and Systems on Chips. CRC Press. [2020-01-10]. （原始內容存檔於2020-04-26）. Baseband Signals are all signals in a radio system, which are not modulated onto the carrier wave. In a cellular phone, this means all signals except those in the radio frequency (RF) part of the phone.
4. U.S. International Trade Commission. In the Matter of Certain GPS Chips, Associated Software and Systems, and Products Containing Same, Investigation No. 337-TA-596 (報告). DIANE Publishing: 6. A GPS receiver typically includes an analog signal processing portion in a radio-frequency circuit (an "RF Front End") and a digital signal processing portion in a baseband circuit (a "Baseband Processor"). In a GPS receiver, the RF Front End receivers the GPS signal, filters and amplifies the signal, and converts the resulting signal into a digital formbat. The resulting digital signal, which is sometimes referred to as the "baseband signal," is sent to the Baseband Processor.
5. 基带是什么. 太平洋IT百科. [2016-02-07]. （原始內容存檔於2016-02-07）.