EEE 360 1

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• Chapter 5
• AM, FM, and Digital Modulated Systems
• Binary Bandpass Signalling Techniques
• OOK
• BPSK
• FSK

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Binary bandpass signaling techniques

• OnOff keying (OOK) amplitude shift keying
  (ASK) - Consists of keying (switching) a carrier
  sinusoid on and off with a unipolar binary
  signal.
• - Morse code radio transmission is an example
  of this technique.
• - OOK was one of the first modulation
  techniques to be used and precedes analog
  communication systems.
• Binary Phase-Shift Keying (BPSK) - Consists of
  shifting the phase of a sinusoidal carrier 0o or
  180o with a unipolar binary signal.
• - BPSK is equivalent to PM signaling with a
  digital waveform.
• Frequency-Shift Keying (FSK) - Consists of
  shifting the frequency of a sinusoidal carrier
  from a mark frequency (binary 1) to a space
  frequency (binary 0), according to the baseband
  digital signal.
• - FSK is identical to modulating an FM
  carrier with a binary digital signal.

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Binary bandpass signaling techniques
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On-Off Keying (OOK)

• Also known as Amplitude Shift Keying (ASK)

• The complex envelope is

• The OOK signal is represented by

• The PSD of this complex envelope is given by

where m(t) has a peak value of
So that s(t) has an average normalized power of
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On-Off Keying (OOK)
Tb bit period R bit rate
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On-Off Keying (OOK)

• PSD of the bandpass waveform is given by

• Null-to-Null bandwidth is and
  absolute bandwidth is

• The Transmission bandwidth is

Where B is the baseband bandwidth
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Detection of OOK

• Non-Coherent Detection

• Coherent Detection with Low-pass filter

Binary output
LPF
OOK in
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Binary Phase Shift Keying (BPSK)
Generation
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Binary Phase Shift Keying (BPSK)

• The BPSK signal is represented by

let
pilot carrier term
data term

• The level of the pilot carrier term is set by
  the value of the peak deviation
• The digital modulation index h is given by

2?? maximum peak-to-peak deviation during time
Ts

• If Dp is small, then there is little power in
  data term more in pilot term
• To maximize performance (minimum probability of
  error)

Optimum case
BPSK signal
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Binary Phase Shift Keying (BPSK)

• The complex envelope for this BPSK is given by

• The PSD for this complex envelope is given by

• PSD of the bandpass waveform is given by

Average normalized power of s(t)
Null-to-Null BW
PSD of optimum BPSK
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Binary Phase Shift Keying (BPSK)
Power Spectral Density (PSD) of BPSK
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Frequency Shift Keying (FSK)

• Discontinuous FSK

• The discontinuous-phase FSK signal is
  represented by

for t during a binary 1 signal
for t during a binary 0 signal
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Frequency Shift Keying (FSK)

• Continuous FSK

Frequency Modulator fc
FSK output
Message m(t)

• The Continuous-phase FSK signal is represented by

or
where
for FSK
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Frequency Shift Keying (FSK)
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Frequency Shift Keying (FSK)
FSK modem with 300bps