1. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Electrical Communications Systems 0909.331.01 Spring 2005 Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring05/ecomms/ Lecture 4a February 22, 2005

2. S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversityPlan Battle Plan for Analyzing Comm Systems Complex Envelope Spectrum of a bandpass signal Amplitude Modulation Signals Systems Complex Envelope Time Domain Spectrum Power Performance Transmitters Receivers Standards Modulation Index Efficiency Bandwidth Noise

3. S. Mandayam/ ECOMMS/ECE Dept./Rowan University ECOMMS: Topics

4. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Battle Plan for Analyzing any Comm. Sys. Signals Systems Complex Envelope Time Domain Spectrum Power Performance Transmitters Receivers Standards Modulation Index Efficiency Bandwidth Noise

5. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Complex Envelope Representation We want a common mathematical representation for information transfer from baseband to bandpass any bandpass signal any time of modulation signal/noise and signal+noise Signal P rocessing Carrier circuits Channel Carrier circuits Signal processing m(t) g(t) s(t) r(t) n(t)

6. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Complex Envelope Representation We want a common mathematical representation for information transfer from baseband to bandpass any bandpass signal any time of modulation signal/noise and signal+noise Modulator message: m(t) carrier: c(t) s(t): radio signal

7. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Spectrum of a Bandpass Signal

8. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Amplitude Modulation (AM) Signals Systems Complex Envelope Time Domain Spectrum Power Performance Transmitters Receivers Standards Modulation Index Efficiency Bandwidth Noise

9. S. Mandayam/ ECOMMS/ECE Dept./Rowan University AM Spectrum -B 0 +B |M(f)| f -f c -B -f c -f c +B 0 f c -B f c f c +B |S(f)| f Message Spectrum AM Spectrum

10. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Single Tone AM s(t) = A c [1 + A m cos(2  f m t)]cos(2  f c t) c(t) = A c cos(2  f c t) m(t) = A m cos(2  f m t) t m(t) AmAm t c(t) AcAc s(t) t AcAc A c [1+A m ]

11. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Spectrum of Single Tone AM Matlab Demo Instrument Demo http://engineering.rowan.edu/~shreek/spring03/ecomms/demos/am.m

12. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Percentage Modulation s(t) t AcAc A max = A c [1+A m ] A min = A c [1-A m ]

13. S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversitySummary