Download presentation

Presentation is loading. Please wait.

Published byDevon Timothy Modified over 3 years ago

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

2
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. UMTS

3
3 450 PremiumDigitalizados 550750 BásicosDigitalizados 54 64 Qam Espectro Banda de Directa425 Espectro Banda de Retorno CM 64 Qam Básicos Analógicos DOCSIS - BANDA DE RETORNO:

4
4 510152025303540 Frecuencia en MHz TELEMETRÍA ( CHEETAH) 7,5 MHz WEB TV (ENSAYOS) 8,9 MHz Distribución de servicios en la banda de retorno ( 5- 42 MHz) SET-TOP-BOX (ACC4000) 10,7 MHz TELEFONIA ( ENSAYOS) 38 a 42 MHz CABLEMODEM ( DOCSIS) 24,5 a 36 MHz SET-TOP-BOX (DCT) 13,8 MHz BW 200 KHz DOCSIS - BANDA DE RETORNO:

5
TDT- Television Digital Terrestre

7
Modulación de Onda CC (CW) Representación en dominios t-f Efectos del ruido en los receptores correspondientes

8
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

9
Modulation Carrier is sinusoidal wave Amplitude, frequency, or phase are varied with a modulating wave - signal

10
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) K a is the modulation sensiviy measured in 1/volt

11
Some issues on AM Overmodulation Leads to envelope distortion. The demodulator will track a false envelope and information will be lost. f c >>>> W – the message bandwidth Easy envelope visualization and tracking

12
Frequency Domain

13
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

14
Linear Modulation

15
DSB-SC- (Double SideBand-Supressed Carrier)

16
Coherent Detection

17
Note that Non coherent detection may lead to null quadrature effect Need coherent local oscillator at demodulation >> complexity >> the price

18
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

19
VSB – Vestigial Sideband Modulation

20
More on VSB

21
Dealing with Noise http://www.ieeeghn.org/wiki/index.php/FM_Radio http://www.ieeeghn.org/wiki/index.php/Edwin_H._Armstrong

22
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

23
Modulación Angular

24
Frecuencia Instantánea

25
Phase Modulation

26
Frequency Modulation (FM) Apex (radio band) - Wikipedia, the free encyclopedia

27
Frequency Modulation (FM) f is the frequency deviation is the modulation index defined as f /f m

28
Which is the FM angle? << 1 radian is known as narrowband FM >> 1 radian is known as wideband FM

29
FM- Cont’

30
FM is non-linear

31
FM with modulating tone

32
Narrowband vs. Wideband FM

33
Narrowband FM

34
Compare to AM

35
Narrowband FM Generation

36
Errors coming from the Aproximation

37
Demodulacion Directa FM (Discrimador de Frecuencia)

38
Discriminador de Frecuencia

39
Equivalente pasabajo de H1(f)

40
Detecting (I)

41
Detecting (II)

42
Detecting (III)

43
Detecting (IV)

44
Chapter 2. Puntos 2.1 a 2.9

45
Narrowband Noise Representations

46
Noise in CW Modulation Chanel Model is AWGN Power spectral density is N o /2 Receiver model defined by a bandpass filter and a demodulator model

58
Tono + ruido pasabanda

59
Calculando pdf conjunta

60
Pdf conjunta de envolvente y fase

61
Marginales

62
Chapter 1. Puntos 1.10 a 1.13 Consulta suplementaria CioffiChap2PassBand.pdf

63
Modulación Analógica frente al ruido

64
SNRs SNR I (Input) Ratio of the average power of the modulated signal s(t) to the average power of the filtered noise SNR o (Output) Ratio of the averaged power of the demodulated signal to the power of noise measured at the receiver output SNR c (Channel) Ratio of the averaged power of the modulated signal to the average power of noise in the message bandwith both at the receiver input

65
Noise in DSB Coherent Detection s(t) is the DSB component of x(t) C is system dependent scaling factor m(t) sample from stationary process of zero mean and S(f) Hence compute SNR C, DSB

66
Figure of Merit in Coherent Detection The quadrature component of noise is rejected in coherent detection The average power of filtered noise n(t) is Same for n I (t)

67
Figure …. The same holds for SSB NO way to improve SNR by increasig bandwith use in DSB w.r.t SSB The effect of modulation is just frequenxy shifting

68
Noise in AM From the SNR at the channel (C, AM) we desire the SNR at the output, demodulator – envelope

69
Phasorial Analysis

70
Figures of Merit Always << 1for AM envelope receivers Equal to 1 for DSB, SSB Caused by waste of power on carrir transmission Existence of threshold effect

71
Threshold effect in AM Detectors

73
Noise Effects in FM Limiter: clipp and round so that amplitude is independent of the carrier amplitude at the receiver input.

74
Noise Model for FM R(t) is Rayleigh Phase is uniform

75
Signal Model for FM

76
Signal and Noise in FM

77
Discriminator Output Provided the carrier to noise is high

78
FM Discriminator: S2N

79
Cont’ The carrier power has noise quoting effect in FM Recall that The average signal transmitted power is k f 2 P

80
How can we improve S2N in FM?

81
The conclusion FM provides a mechanism for the exchange of improved noise performance by increased transmission bandwidth FM can also reject other FM signals closed to the carrier frequency provided interferent signal are weaker w.r.t. the target FM input

82
Threshold Effect in FM Assumption Carrier to Noise ratio at the discriminator input >> 1 Violation to this assumption FM receiver breaks. From breaks to sputtering sounds. The formula does not hold.

83
No signal but Noise Ac >> n I, n Q Ac << n I, n Q P 1 noves to the origin and random phase is observed is around

84
Alternatevely Clicks are heard after the low pass filter

85
Threshold Effect As is decreased the rate of clicks grows Rate of clicks is high threshold occurs

87
Designing an FM System Given D ( ) Compute B T Given B T and N 0 (Noise power per unit bandwidth) Determine A C to keep above the threshold

88
FM Threshold Reduction FM demodulator with negative feeback (FMFB) or PLL

89
FM Threshold Reduction The VCO output The phase comparator output

90
FM Threshold Reduction (cont)

93
Linear Model of the PLL-FM Demodulator

94
PreEmphasis - Deemphasis Pre at transmitter De- at the receiver

95
Pre-emphasis & De-emphasis Pre at transmitter De- at the receiver

96
Conclusions

97
Chapter 2. Puntos 2.10 a 2.14

Similar presentations

OK

Chapter 6. Effect of Noise on Analog Communication Systems

Chapter 6. Effect of Noise on Analog Communication Systems

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on cultural tourism in india Upload and view ppt online maker Ppt on flowers for kindergarten Ppt on spiritual leadership theory Ppt on total quality management in education Ppt on cross cultural differences Ppt on basic computer organisation Ppt online download youtube Download ppt on oxidation and reduction calculator Ppt on non ferrous metals