S. Mandayam/ECE Dept./Rowan University Digital Communications / Fall 2002 Shreekanth Mandayam ECE Department Rowan University Lecture 7 October 21, 2002

S. Mandayam/ECE Dept./Rowan University Plan Midterm Exam Bandpass Data Transmission Binary Modulated Bandpass Signaling OOK BPSK and DPSK FSK Multilevel Modulated Bandpass Signaling QPSK & MPSK QAM

S. Mandayam/ECE Dept./Rowan University Digital Communications Transceiver Anti- aliasing Filter SamplingQuantization Data Encryption Encoder Source Encoder Error Control Encoder Channel/ Line Encoder Modulator MUX Audio Amp Source Decoder Data Encryption Decoder Error Control Decoder Equalization / Decision Circuits Demod- ulator DEMUX Reconstruction/ DAC ADC CODEC MODEM Analog o/p Multiple access channel Analog i/p

S. Mandayam/ECE Dept./Rowan University Digital Modulation Carrier signal: A c cos (2  f c t +  ) Modulation: m(t) Modulated signal:A c (t) cos (2  f c (t) t +  (t)) Vary Vary Vary amplitude frequency phase Variations are discrete!!!!!  m(t); discrete Binary OOK BPSK DPSK FSK Multilevel QPSK MPSK QAM

S. Mandayam/ECE Dept./Rowan University Principle ……… 1 0 Analog message Digital code Digital message Sinusoidal carrier modulate AM FM PM AM & PM 1 0

S. Mandayam/ECE Dept./Rowan University Signal Vector Representation Phase Magnitude S 0 degrees I Q I-Q Plane s(t) = A c (t) cos (2  f c t +  (t)) fixed!!!

S. Mandayam/ECE Dept./Rowan University Signal Changes: Representation in the IQ Plane S1S1 S2S2 I Q Magnitude Change S1S1 S2S2 I Q Phase Change S1S1 S2S2 I Q Magnitude & Phase Change Frequency Change ??? I-Q Diagrams or Constellations

S. Mandayam/ECE Dept./Rowan University Binary Phase Shift Keying (BPSK) I Q 10 IQ Diagram t  (t) 0 radians  radians s(t) = A c cos(2  f c t +  (t))

S. Mandayam/ECE Dept./Rowan University Frequency Shift Keying (FSK) Electronic Switch Binary data input m(t) Oscillator f 1 Oscillator f 2 FSK Output Control Line Binary data input m(t) Frequency Modulator Carrier: f c FSK Output Discontinuous-Phase FSK Continuous-Phase FSK

S. Mandayam/ECE Dept./Rowan University Quadrature Phase Shift Keying (QPSK) IQ Diagram I Q 

S. Mandayam/ECE Dept./Rowan University M-ary Phase Shift Keying (M-PSK) I Q Octophase I-Q Constellation

S. Mandayam/ECE Dept./Rowan University P/4 QPSK or 4-QAM I Q 11 IQ Diagram s(t) = A c cos(2  f c t +  (t)) t  (t)     

S. Mandayam/ECE Dept./Rowan University Summary