10-401-09-BandpassTransmissionDetection-2

10-401-09-BandpassTransmissionDetection-2 - Essential...

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Bandpass Modulation and Demodulation 1 Essential Blocks:Digital Communication System Format Pulse Modulation Bandpass Modulation Transmitter Synchronization Format Detection Demodulation Sampling Receiver Channel 010100 0 T 2T 3T 4T 5T 6T 7T 8T 0 T 2T 3T 4T 5T 6T 7T
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Bandpass Modulation and Demodulation 2 Receiver performance under AWGN (revisit) The variance of l Var [ l ]= N 0 E b 1 − the probability of error be derived as in the baseband detection system; P e = P B = P l 0 H 0 = P l 0 H 1 = Q E b 1 − N 0 Coherent PSK s 0 t =− s 1 t =− 1(antipodal or bipolar signals) P e = P B = Q 2 E b N 0 Coherent FSK s 0 t and s 1 t are orthogonal to each other = 0(orthogonal or unipolar signal) P e = P B = Q E b N 0 z = y  Y = y A E b / 2T b Q u = u exp − z 2 / 2 dz
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Bandpass Modulation and Demodulation 3 Continuous phase-frequency SK (CPFSK) In coherent FSK, phase information be passed to the Rx via synchronisation (impossible to exploit phase) Improve noise performance by utilizing phase information in a different way, CPFSK (improvement on FSK) Price: more complex receiver CPFSK signal s t = A c cos 2 f c t  t   t :time varying phase f c = f 1 f 0 / 2 Signal components: s t = [ A c cos 2 f 1 t  0  binary 1 A c cos 2 f 0 t  0  binary 0 ]  0 , at t = 0,  t depends on previous values  t = 0 ± h T b t where :symbol 1 :symbol 0 h = T b f 1 f 0 : deviation ratio both phase and bit transition are continuous  T b − 0 = [ h, symbol 1 − h, symbol 0 ]
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Bandpass Modulation and Demodulation 4 Minimum Shift Keying (MSK)
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10-401-09-BandpassTransmissionDetection-2 - Essential...

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