1. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Electrical Communications Systems ECE.09.331 Spring 2010 Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring10/ecomms/ Lab 2: Pre-lab Instruction

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

3. S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversityPlan Baseband and Bandpass Signals Modulation Amplitude Modulation AM: Envelope Detector DSB-SC Modulation Systems Signals Complex Envelope Time Domain Spectrum Systems Balanced Modulator Coherent Detector Lab Project 2

4. S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversityModulation Modulating Signal Message Signal m(t) (Baseband) Modulated Signal s(t) (Bandpass) Information Modulation Frequency Translation What is it? How is it done? Modulator message: m(t) carrier: c(t) s(t): radio signal

5. 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

6. 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

7. 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 ]

8. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Spectrum of Single Tone AM Matlab Demo Instrument Demo http://engineering.rowan.edu/~shreek/spring10/ecomms/demos/am.m

9. 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 ]

10. S. Mandayam/ ECOMMS/ECE Dept./Rowan University Recall: 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

11. S. Mandayam/ ECOMMS/ECE Dept./Rowan University AM: Envelope Detector ~ + - + - + - v i (t) v o (t) RLRL s(t) Circuit Waveforms C s(t) t

12. S. Mandayam/ ECOMMS/ECE Dept./Rowan University DSB-SC Modulation Signals Systems Time Domain Complex Envelope Spectrum Power Performance Transmitters Receivers Standards Modulation Index Efficiency Bandwidth Noise -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 DSB-SC Spectrum Matlab Demo http://engineering.rowan.edu /~shreek/spring10/ecomms/ demos/dsbsc.m

13. S. Mandayam/ ECOMMS/ECE Dept./Rowan University DSB-SC: Balanced Modulator AM A c cos2  f c t m(t) AM -A c cos2  f c t -m(t) 

14. S. Mandayam/ ECOMMS/ECE Dept./Rowan University DSB-SC: Coherent Detector Product Modulator A o cos2  f c t s(t) Local Oscillator Baseband LPF v(t)

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