Chapter 7 Probability of Error for Coherent Bandpass Systems

1
Chapter 7Probability of Error for Coherent
Bandpass Systems

• On-off Keying with Coherent Detection
• BPSK
• Coherent FSK

Huseyin Bilgekul EEE 461 Communication Systems
II Department of Electrical and Electronic
Engineering Eastern Mediterranean University
2
Bandpass (Carrier) Systems
3
Coherent Detection
a) Matched Filter Detector
b) Correlator Detector

• Matched filter then sample and detect.
• Coherently demodulate, then filter out image with
  matched filter and sample/detect
• Coherent detector must match the phase of the
  input signal
• Detect pulse with an output signal to noise ratio
  of,

4
Coherent Detection of OOK
5
Coherent Detection of OOK
6
Coherent Detection of OOK

• Same as on/off (polar) signaling because we are
  transmitting polar as a bandpass signal.
• Requires 3 dB more power than BPSK in a coherent
  system

7
Coherent Detection of BPSK
8
Coherent Detection of BPSK
9
Coherent Detection of BPSK

• Same as polar signaling
• Requires -3 dB less power than OOK in a coherent
  system

10
Coherent Detection of FSK

• FSK signal is
• The noise power is
• The optimum threshold is VT0
• To find Ed

11
Coherent Detection of FSK

• The BER becomes
• FSK is 3 dB worse than BPSK.
• FSK is equivalent to OOK.

12
Coherent Detection of FSK