看板 Grad-ProbAsk 關於我們 聯絡資訊
The pdf of the amplitude of a lowpass random signal x(t) (bandwidth = 20kHz) at any time t0 is uniformly distributed over(-16,16) This signal is sampled at a rate higher than the Nyquist rate to provide a guard-band of 5k Hz, digitized with a uniform 64-level quantizer, and encoded by a natural PCM coder. (c) If the PCM output is baseband modulated by 8-level polar NRZ signals, the "one-sided mainlobe bandwidth" will be ? ______ 解答: 前面(a)小題有算出Rb= 270Kbps, 所以Rs = Rb/3 = 90K BT= 1/Ts = Rs = 90K (HZ) 抱歉讓大家看了這麼多的英文, 我想問的只有C小題那個被我引號(" ") 起來的one-sided mainlobe bandwidth到底是什麼東西@@? 依據大碩TKB老師的解答, 我猜測老師應該是用ideal Nyquist channel (方波) BT = Rs/2 , 但是成大又很喜歡考one sided, 依據之前對於AWGN的處理方式 one sided 通常是我們平常習慣用的數據的兩倍, 於是one sided mainlobe BT 必須要是平常的兩倍, 所以乘以二, 變成BT=Rs, 這是我看老師的解答所作的推論 但是真的是這樣嗎? 我看成大一直考one sided mainlobe bandwidth, 這到底要如何計算? 跟一般的bandwidth又有何不同咧? -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 114.40.65.100
jimmihg:希望板上能有高手能不吝賜教, 感激不盡!! 02/25 19:56
FatDaniel:教科書上有定義嗎? Haykin or Ziemer 的書沒有嗎@@? 02/25 21:07