1. Digital Modulation
oleh
Warsun Najib

2. Digital Modulation Three basic forms of digital modulation
Analog Digital
AM Amplitude ASK
FM Frequency FSK
PM Phase PSK
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Digital Modulation

3. Amplitude Shift Key t
(logic 1)
(logic 0)
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Digital Modulation

4. Amplitude Shift Key[1] The ASK waveform for one pulse (logic 1)
In order to find an Energy Spectrum of
The Autocorrelation technique is used
Delay
Energy Spectrum
Therefore Energy Spectrum of ASK
sinc2 function
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Digital Modulation

5. Power Spectral Density
Detection of ASK : detect present (logic 1) or of the carrier
absent (logic 0)
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Digital Modulation

6. Frequency Shift Key t
Output for 1
Output for 0
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Digital Modulation

7. Power Spectral Density
Frequency separation
Note: To prevent significant overlapping of the bandpass of two
filters in detection process
frequency separation Data rate
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Digital Modulation

8. Power Spectral Density[1]
The Actual shape of Power Spectral Density of FSK
Detection of FSK Bandpass Filter
is used to detect f1 (1) and f2 (0)
In general for frequency separation; ; or
where m is an integer
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Digital Modulation

9. Phase Shift Key t ~
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Digital Modulation

10. Power Spectral Density
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Digital Modulation

11. Detection of PSK Phase Reversal Key (PRK)
Since information is in the phase, only synchronous detection is possible
Receiver:
To data detection
Matched filter detection
carrier
Synchronize
(coherent)
Local oscillator e.g. Crystal oscillator
known as Voltage Control Oscillator VCO
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Digital Modulation