10.bandpass modulation(1).ppt [호환...
TRANSCRIPT
디지털통신
여섯째주
Digital Communications
Chapter 4Bandpass Modulation And Demodulation/Detection
Signal Processing Lab
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Block Diagram of a DCS
2
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4.2 Digital Bandpass Modulation Bandpass Modulation : The process of converting data signal to a
sinusoidal waveform where its amplitude, phase or frequency, or a combination of them, is varied in accordance with the transmitting data
Bandpass signal :
Where gT(t) is the baseband pulse shape with energy Eg
We assume here ( otherwise will be stated ) : gT(t) is a rectangular pulse shape with unit energy Gray coding is used for mapping bits to symbols; Es denotes average symbol energy given by
M
i is EM
E1
1
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Digital Bandpass Modulations (con’td)
One dimensional waveforms Amplitude Shift Keying ( ASK ) M-ary Pulse Amplitude Modulation ( M-PAM )
Two dimensional waveforms M-ary Phase Shift Keying ( M-PSK ) M-ary Quadrature Amplitude Modulation ( M-QAM )
Multidimensional waveforms M-ary Frequency Shift Keying ( M-FSK)
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Bandpass Digital Modulations
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Coherent Detections Coherent detectionRequires carrier phase recoveryNeeds circuits to perform phase estimation.
Source of carrier-phase mismatch Propagation delayOscillator mismatch
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Coherent Detections (cont’d)
)ˆ(
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Non-Coherent Detections
Does not require carrier phase recovery
Uses differential decoder or energy detectors
Less complexity at the price of higher error rate
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One Dimensional Modulation, Demodulation and Detection
Amplitude Shift Keying ( ASK ) modulation :
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One Dimensional mod.,….. (cont’d)
M-ary Pulse Amplitude modulation (M-PAM)
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One Dimensional mod.,….. (cont’d)
Coherent detection of M-PAM
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Two Dimensional Modulation, Demodulation and Detection
M-ary Phase Shift Keying (M-PSK)
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Two Dimensional mod.,….. (cont’d)
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Two Dimensional mod.,….. (cont’d)
Coherent detection of MPSK
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Two Dimensional mod.,….. (cont’d)
M-ary Quadrature Amplitude Mod. (M-QAM)
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Two Dimensional mod.,….. (cont’d)
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Two Dimensional mod.,….. (cont’d)
Coherent detection of M-QAM
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Multi-Dimensional Modulation, Demodulation and Detection (HW #4 p.202 Example 4.3)
M-ary Frequency Shift Keying ( M-FSK )
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Multi-Dimensional mod.,….. (cont’d)