Lecture 6: Amplitude Modulation (QAM, SSB, VSB and Analog TV) Dr. Mohammed Hawa. Electrical Engineering Department, University of Jordan

Transcription

1 Leture 6: Amplitude Modulation (QAM, SSB, VSB and Analog TV) Dr. Mohammed Hawa Eletrial Engineering Department University of Jordan EE421: Communiations I Orthogonality In Modulation: QAM modulation (sin/os) Used in DVB, Wi-Fi, WiMAX, 3G, 4G LTE In Multiplexing: CDMA(Walsh odes, GOLD odes) Used in 3G ellular telephony OFDMA(multiple osines) Used in Wi-Fi, WiMAX, 4G LTE 2 1

2 QAM(Quadrature Amplitude Modulation) = 1 os + 2 sin 3 M 1(ω) γ 2πB 2πB ω M 2(ω) 2πB 2πB ω Φ QAM(ω) γ γ ω ω 2πB ω ω ω + 2πB 4 2

3 M 1(ω) γ 2πB 1 2πB 1 ω M 2(ω) 2πB 2 2πB 2 ω Φ QAM(ω) γ γ ω ω ω ω 2πB 2 ω + 2πB 2 5 QAM Transmitter and Reeiver 6 3

4 QAM vs. DSB-SC Advantages of QAM: QAM is more bandwidth effiient than DSB-SC, allowing us to send two signals on the same hannel (of bandwidth 2B). Disadvantages of QAM: When synhronous detetion is used for QAM with errors in synhronization, attenuation, distortion and o-hannel interferene show up. 7 Appliations Analog QAM is used to arry hrominane (olor) information in Analog TV broadasting. Digital QAM (to be disussed later) is very popular nowadays: DVB, DAB, Wi-Fi, WiMAX, 3G, 4G, ADSL, et. DSB-SC is used in analog instrumentation, and as part of multiplexing in Stereo FM broadasting. 8 4

5 SSB-SC (USB) Modulation 9 M( ) DSB-SC( ) + BPF SSB-SC( ) (USB)

6 11 VSB-SC (USB) Transmitter 12 6

7 M( ) DSB-SC( ) + Vestigial Filter VSB-SC( ) (USB) / VSB-SC (USB) Reeiver 14 7

8 VSB-SC( ) (USB) /4 + X( ) + /4 /4 /4 /4 2 X( ) LPF /4 /4 + 2 Y( ) /4 15 VSB-SC (LSB), VSB+C (USB), VSB+C (LSB) 16 8

9 VSB Advantages of VSB: Simple to generate (no need for sharp filters). Can vary the VSB filter bandwidth (flexibility). VSB transmission bandwidth is smaller than DSB. Smaller bandwidth means more immunity to frequeny-seletive fading ompared to DSB. In ase of synhronization errors, VSB-SC suffers less attenuation and distortion ompared to DSB-SC. 17 VSB Disadvantages of VSB: VSB-SC require synhronous detetion. VSB+C (whih allows envelope detetion) is less power effiient ompared to AM (sine we need A >> m(t) min ) Appliations: VSB+C is used to send luminane (B & W) information in Analog TV broadasting. VSB-SC is used in fasimile (fax) mahines. 18 9

10 Summary QAM Bandwidth is 2(but we send two signals) Average power is = + SSB-SC (USB or LSB) Bandwidth is (one signal) Average power is = VSB-SC(USB or LSB) Bandwidth is 1+(one signal) Average power is = 19 Analog Television Standards U.S. Standard European Standard Analog TV NTSC: National Television System Committee (VSB+C, QAM, FM; FDM) PAL: Phase Alternating Line (VSB+C, QAM, FM; FDM) Digital TV ATSC: Advaned Television System Committee (MPEG-2; VSB-8 or QAM; TDM+FDM) DVB-T, DVB-S, DVB-S2,...: Digital Video Broadasting (MPEG-2; QPSK, QAM; TDM+FDM) 2 1

11 Analog Television (PAL/NTSC) 21 Television and Pixels 22 11

12 Sanning Lines and Resolution 23 Analog Television (PAL/NTSC) M( ) 4. MHz M( ) NTSC PAL 6. MHz 24 12

13 Standard Definition (SDTV) Resolution Aspet ratio Pixel shape Form of sanning Frame Rate (Hz) Vertial Horizontal :3 square 74 4:3 or 16:9 non-square interlaed progressive interlaed progressive 3 (6 fields/s) Many other profiles and frame rates are supported by ATSC and DVB, but the above are the most popular and the most likely to be supported by a digital TV set (monitor). The monitor profile name is alled 48i and 48p (6 fields/s) High Definition (HDTV) Resolution Aspet ratio Pixel shape Form of sanning Frame Rate (Hz) Vertial Horizontal :9 square progressive interlaed (5 fields/s) 3 (6 fields/s) :9 square progressive :9 square progressive

14 Luminane & Chrominane 27 RGB to YUV 28 14

15 RGB to YUV Transformation See for mode details. 29 Notieable only in sharp images 3 15

16 Analog TV(VSB+C & FM & QAM)