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Frequency Modulation (FM) in Signal Processing

Explore the principles of Frequency Modulation (FM) in signal processing, covering topics such as spectrum analysis, demodulator circuits, and FM radio block diagrams. Learn about FM noise, stereo FM, and the impact of modulation errors on signal quality. Discover practical FM transmitter and receiver circuits for hands-on learning.

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Frequency Modulation (FM) in Signal Processing

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  1. Angle Modulation

  2. Angle Modulation • General Format • Phase • Instantaneous Frequency

  3. Phase and Frequency Modulation • Waveform • Base band • PM • FM • Constant amplitude • No static noise • Modulation Index • m inversely proportional to fm for FM • Spectrum • Bessel functions • Broader bandwidth • Carson’s rule B=2(+fmax)

  4. FM Java • http://contact.tm.agilent.com/Agilent/tmo/an-150-1/classes/liveFM_popup.html

  5. FM Noise • Amplitude • Controlled by limiter • Driving into saturation • Phase • Phasor picture • Maximum angle deviation • White noise

  6. Frequency Error by Phase Noise • Simplified S/N Analysis • Signal frequency: 1 kHz • Signal amplitude, ES: 10 • Frequency deviation: 5 kHz • Noise amplitude, EN: 1 • (S/N)P: 20 dB • Maximum angle deviation: 0.1 rad • Noise modulation index, mN: 0.1 • Frequency error caused by noise • 1 kHz x 0.1 = 100 Hz • (S/N)F: 5 kHz/100 Hz = 50; 34 dB in power

  7. FM Noise • Threshold and Capture Effect • S/N below threshold: poor performance • S/N above threshold: improved performance • Strong station dominates weak station

  8. FM Noise • Noise in FM system • Frequency error: mNfm • Larger signal needed at higher frequency • Pre-emphasis and de-emphasis • High pass and low pass filters

  9. FM Radio • Source • Audio, 50-15 kHz • Carrier Frequency • 88 – 108 MHz • IF • 10.7 MHz • Performance • 15 kHz bandwidth • 50-100 km range • 10 µV sensitivity

  10. FM Radio

  11. Block Diagram

  12. FM Modulator Circuits • Varactor • Variable Reactance Modulator

  13. FM Detector Circuits • FM Detection • Convert frequency deviation to voltage • Frequency dependent throughput • Slope detector • Discriminator • Project

  14. FM Detector Circuits • Quadrature demodulator tutorial • PLL

  15. FM Stereo - Frequency Allocation • Sub-Carrier • Multiplexing

  16. Stereo Transmitter • Frequency Division Multiplexing • 19 kHz Pilot • Preemphasis

  17. Stereo Receiver

  18. Practical Circuits • FM Transmitter • http://www.free-electronic-circuits.com/circuits/fm-transmitter.html • Regenerative Receiver • http://www.somerset.net/arm/fm_only_one_transistor_radio.html

  19. IC-Based FM Radio

  20. Digital Audio Broadcasting • Eureka • Britain: Band III, 174-240 MHz • Canada: L-Band, 1452 to 1492MHz • Data: 192 kb/s, digital compression • iBiquity • In band on channel • Analog + digital sideband • Perceptual audio coder • http://beradio.com/mag/radio_iboc_transmission/index.html • http://www.broadcastpapers.com/whitepapers/BAsia04BcastElectHDRadio.pdf • Sirius and XM Radio

  21. Television

  22. Analog TV • Standard • NTSC, PAL, SECAM • Broadcasting • Local station, CATV, satellite • HDTV • Monitor

  23. NTSC Signaling • Vertical Scan Lines • 525 lines (625) • Aspect Ratio • 4:3 • Frame Rate • 30 Hz (25 Hz) interlaced • 525 lines/frame x 30 frames/sec = 15.75 kHz • Resolution: • 0.7-0.75 utilization factor

  24. NTSC Broadcasting 4.75 3.579545

  25. Analog TV Signaling • Composite Video • Luminance (brightness) ~340 lines • Y=0.3R+0.5G+0.11B • Chrominance (color); 50-100 lines • I=0.6R-0.28G-0.32B • Q=0.21R-0.52G+0.31B • H Sync • V Sync • Blanking • Color burst • Reference

  26. Waveforms

  27. Spectrum • Luminance • AM vestigial side band • From -0.75 MHz to +4 MHz • Chrominance • QUAM VSBSC • Pilot at 3.58 MHz • Sound • FM • Sub-carrier at 4.5 MHz

  28. TV Receiver Circuits • RF, IF • 45 MHz • Video Detector • Composite Video to RGB • Comb filter • Audio IF, Audio Detector • Sync Separator • H Sync • V Sync • TV Circuit Chips http://www.nteinc.com/linear_web/tv.html

  29. Block Diagram

  30. Display - CRT • CRT • Control, acceleration, focusing, deflection, shadow mask, purity, convergence • Picture-in-picture (PIP)

  31. Video Image Sensors • Vidicon • CCD • http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html • CMOS • http://micro.magnet.fsu.edu/primer/digitalimaging/cmosimagesensors.html

  32. CATV System • Video Signal Distribution • Source • Fiber trunk, linear modulator • Headend • Coax distribution, amplifier, splitter • Pay per View • Cable Modem • Reference • http://people.deas.harvard.edu/ ~jones/cscie129/nu_lectures/ lecture13/CATV/CATV.html

  33. Digital Set Top Box http://www.xilinx.com/esp/consumer/home_networking/pdf_files/stb_to_rg/stb_complete.pdf Source: TI

  34. High-Definition TV • Analog MUSE • 1125 lines, 20 MHz • Digital TV • 1920x1080, 6 MHz • Compression

  35. Digital TV

  36. HDTV Signaling • MPEG-2 • 19.39 Mbps • http://www.bretl.com/mpeghtml/MPEGindex.htm • 8-VSB • http://www.broadcast.net/~sbe1/8vsb/8vsb.htm

  37. Other Display Technologies • LCD • Plasma Display Panel • Other Display Technologies • OLED • Field emission • Electroluminescent display • E-Ink • Projection • LCOS • Digital light processor • Grating light valve http://www.hdtvmagazine.com/downloads/Display%20Wars%20-%20Flat%20Panels%20(InfoComm%202005).ppt

  38. Chapter Review • FM and PM • Modulation Index and Side Bands • Phase Noise and FM Noise Analysis • Limiter and S/N Improvement • FM Modulator • FM Detection • NTSC • DTV • CATV • Display Technologies

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