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Modulación Analógica (AM-FM)

Modulación Analógica (AM-FM). CX Eléctricas 2011 E.Tapia. UMTS.

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Modulación Analógica (AM-FM)

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  1. Modulación Analógica (AM-FM) CX Eléctricas 2011 E.Tapia

  2. UMTS As can be seen from the diagram, UMTS FDD is designed to operate in paired frequency bands, with uplink in the 1920-1980 MHz band, and downlink in the 2110-2170 MHz band. UMTS TDD is left with the unpaired frequency bands 1900-1920 MHz, and 2010-2025 MHz. 

  3. Espectro Banda de Directa 64 Qam CM 64 Qam 64 Qam 550 750 54 450 Básicos Analógicos 5 42 Premium Digitalizados Básicos Digitalizados Espectro Banda de Retorno DOCSIS - BANDA DE RETORNO: Banda de Retorno y aspectos Relacionados 3

  4. TELEMETRÍA ( CHEETAH) 7,5 MHz SET-TOP-BOX (ACC4000) 10,7 MHz WEB TV (ENSAYOS) 8,9 MHz TELEFONIA ( ENSAYOS) 38 a 42 MHz CABLEMODEM ( DOCSIS) 24,5 a 36 MHz SET-TOP-BOX (DCT) 13,8 MHz BW 200 KHz 5 10 15 20 25 30 35 40 Frecuencia en MHz DOCSIS - BANDA DE RETORNO: Distribución de servicios en la banda de retorno ( 5- 42 MHz) Banda de Retorno y aspectos Relacionados 4

  5. TDT- Television Digital Terrestre

  6. Modulación de Onda CC (CW) • Representación en dominios t-f • Efectos del ruido en los receptores correspondientes

  7. Modulation -Demodulation • Ix transmission in presence of noise • Ix bearing signals or baseband signals • Transmitter-Channel-Receiver • Frequency shifting on Tx – Modulation using a carrier • Frequency shift back on Rx –Demodulation

  8. Modulation • Carrier is sinusoidal wave • Amplitude, frequency, or phase are varied with a modulating wave - signal

  9. Amplitude Modulation • Message signal m(t) and carrier c(t) are independent • Carrier amplitude is varied about a mean value (Ac), linearly with m(t) • Ka is the modulation sensiviy measured in 1/volt

  10. Some issues on AM • Overmodulation • Leads to envelope distortion. The demodulator will track a false envelope and information will be lost. • fc >>>> W – the message bandwidth • Easy envelope visualization and tracking

  11. Frequency Domain

  12. Note that • Mod-Demod are implemented using non-linear devices • Demod are often envelope detectors • AM Power and AM Bandwith • Not efficient at power use (tx of c(t)) • Sidebands are related each other >>>> just one is needed • Hence >>>> avoid c(t) transmission and duplicate sidebands

  13. Linear Modulation

  14. DSB-SC- (Double SideBand-Supressed Carrier)

  15. Coherent Detection

  16. Note that • Non coherent detection may lead to null quadrature effect • Need coherent local oscillator at demodulation >> complexity >> the price

  17. SSB MOdulation • DSB-SC + Filtering for Sideband Removal • Highly selective filters from cristal oscillators • Coherent detector >> low power pilot carrier addition is added at transmission

  18. VSB – Vestigial Sideband Modulation

  19. More on VSB

  20. Dealing with Noise http://www.ieeeghn.org/wiki/index.php/FM_Radio http://www.ieeeghn.org/wiki/index.php/Edwin_H._Armstrong

  21. Radio Spectrum • AM problems • static interference from household appliances and lighting • limited audio quality (frequency response and dynamic range) • nighttime interference between many stations (co-channel interference), because of ionospheric refraction, especially in rural areas http://www.cybercollege.com/frtv/frtv020.htm

  22. Modulación Angular

  23. Frecuencia Instantánea

  24. Phase Modulation

  25. Frequency Modulation (FM) Apex (radio band) - Wikipedia, the free encyclopedia

  26. Frequency Modulation (FM) •  f is the frequency deviation •  is the modulation index defined as  f /fm

  27. Which is the FM angle? •  << 1 radian is known as narrowband FM •  >> 1 radian is known as wideband FM

  28. FM- Cont’

  29. FM is non-linear

  30. FM with modulating tone

  31. Narrowband vs. Wideband FM

  32. Narrowband FM

  33. Compare to AM

  34. Narrowband FM Generation

  35. Errors coming from the Aproximation

  36. Demodulacion Directa FM (Discrimador de Frecuencia)

  37. Discriminador de Frecuencia

  38. Equivalente pasabajo de H1(f)

  39. Detecting (I)

  40. Detecting (II)

  41. Detecting (III)

  42. Detecting (IV)

  43. References Chapter 2. Puntos 2.1 a 2.9

  44. Narrowband Noise Representations

  45. Noise in CW Modulation • Chanel Model is AWGN • Power spectral density is No/2 • Receiver model defined by a bandpass filter and a demodulator model

  46. Representación en Envolvente-Fase

  47. Ruido. Envolvente y Fase

  48. SampleDistributions

  49. Cont’

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