CE Lecture on various AM modulation and Demodulation
- 1. AM – Modulation and Demodulation Techniques 1
- 2. Double-sideband Suppressed Carrier Amplitude Modulation (DSB-SC) 2
- 3. DSB-SC 3
- 4. DSB-SC (Why DSB? Why SC?) 4
- 7. Difference between Modulator & Demodulator Difference between modulator and demodulator lies in input signal and output filter. For modulator, input is message signal and outputof multiplier is passed through a band pass filter (centered at fc). For demodulator, input is DSB-SC signal and outputof multiplier is passed through a low passfilter. 7
- 8. Example of DSB-SC Signal 8
- 9. Example of DSB-SC Signal 9
- 10. AM Modulators 10 Multiplier Modulators Non-linear Modulators Switching Modulators
- 13. Non-linear Modulators This is known as a balanced modulator (single balanced modulator) 13
- 17. Switching Modulators The lesson of the example is: 17
- 18. Diode-bridge Switch (Switching Modulator) 18
- 19. Ring Modulator (Switching Modulator) 19
- 20. Ring (Switching) Modulator Here, wo(t)=2w(t)-1 20
- 21. Amplitude Modulation (AM) Alternative of DSB-SC = AM 21
- 22. Envelope Detection for AM 22
- 23. Envelope Detection for AM 23
- 24. Envelope Detection for AM 24
- 25. Problem with Envelope Detection 25
- 26. Problem with Envelope Detection=Low Power Efficiency 26
- 27. Demodulation of AM Signals 27
- 30. Limitations of DSB-SC and AM 30 Both DSB-SC and AM have two sidebands (LSB/USB). So the modulated bandwidth is 2B Hz when the message bandwidth is B Hz. This leads to lower spectral efficiency. There are two ways to improve spectral efficiency: 1. SSB 2. QAM
- 31. Bandwidth Efficient AM (SSB and QAM) 31 SSB (single sideband AM) removes LSB or USB and uses a bandwidth of B instead of 2B Hz forone message. QAM (quadrature AM) sends two (instead of one) messages over the same bandwidth of 2BHz.
- 32. SSB Modulation 32 Three methods: 1. Phase shifting 2. Selective filtering 3. Weaver method
- 33. Selective Filtering (SSB Modulation) 33
- 34. Phase-shift method (SSB Modulation) 34
- 35. Phase-shift method (SSB Modulation) 35
- 38. Applications of AM Entertainment - AM Radio (music, talk radio) Business - CB Radio to relay shipment progress, conference calls with other branches via telephone or speakerphone Government - Police officers keeping contact with the station, or relaying the information and location of a suspect Personal - Cell phones or walkie-talkies for chatting with friends Military - Using undetectable radio signals to communicate with other soldiers, or voice commands to control weapons
- 39. Generation of AM https://www.youtube.com/watch?v=l6i1XJlAwtw https://www.youtube.com/watch?v=tp0GaNKqaaY Generation of DSB-SC-AM https://www.youtube.com/watch?v=u0WcxJmOfiI Generation of SSB-SC-AM https://www.youtube.com/watch?v=D6IBERQFP3s https://www.youtube.com/watch?v=GKYWaIXvVYc