[理工] 通訊 98成大電通
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?
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