13數(shù)字通信載頻偏差與載波頻率同步-在線瀏覽
2025-01-30 21:09本頁(yè)面
【正文】 13QuadratureI n P h a s e含相偏的星座圖9 Source Coding Channel Encoding Digital Modulation Lowpass Filtering Carrier modulation Channel Carrier Demodulation Lowpass Filtering Digital Demodulation Channel Decoding Carrier symbol synchronization Channel Equalization Source decoding 因此接收機(jī)前端一般具有載波同步模塊 10 如何進(jìn)行載頻同步 1。1 數(shù)字通信 (第十四講 ) 載頻偏差與載波頻率同步 202311 2 B i n a r y D a t a G e n e r a t o r1 6 Q A MM o d u l a t i o nU p S a m p l eS q r t C o s i n eF i l t e rC a r r i e rM o d u l a t i o nA W G NC h a n n e lM a t c h F i l t e rD o w n S a m p l e1 6 Q A MD e m o d u l a t i o nB E RC a l c u l a t i o nBlock diagram of the munication system 發(fā)射信號(hào)被調(diào)制倒載頻上，載頻信號(hào)由發(fā)射機(jī)產(chǎn)生 3 接收機(jī)的載波解調(diào)將信號(hào)降到基帶，載波信號(hào)由接收機(jī)產(chǎn)生 4 載波頻率偏差 ? 發(fā)射 /接收信號(hào)的載波頻率不同 器件固有頻率偏差 ? 發(fā)射 /接收頻率受到溫度變化的影響 溫度漂移 ? 一般來(lái)講發(fā)射 /接收頻率偏差在 50ppm以下 1ppm為 106 5 Carrier frequency error model Assume the transmitted signal is Here fc is the carrier frequency of the transmitted signals. If the frequency of the receiver is Then the received base band signal bees 39。cf6 The sampled signal bees The frequency difference is ( ) ( ) | ( ) e xp( 2 ( 39。發(fā)送用于同步的 pilot頻率 發(fā)射的是單頻信息，沒(méi)有數(shù)據(jù) 2。載頻信號(hào)上調(diào)制了未知信號(hào) 沒(méi)有專用的單頻信號(hào)或訓(xùn)練序列 4。21exp。2exp0TdttstrNC ??設(shè)發(fā)射 /接收信號(hào)存在頻率偏差，傳輸?shù)氖禽d波信號(hào)，依據(jù)最大似然法則，有 其最大似然函數(shù)為 14
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