Television. Modern Electronic Communication.pptx

Modern Electronic Communication 9th edition
Jeffrey S. Beasley and Gary M. Miller
Copyright ©2008 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Chapter 17
Television
Modern Electronic Communication
Beasley & Miller

Television
• Digital Television (DTV)
• High Definition TV (HDTV)
 Began transmission in 1999
 All stations on the air in 2009
 Old NTSC (analog) signal is no longer
transmitted
• National Television System Committee
(NTSC)

Figure 17-1 The (a) HDTV screen ratio and (b) NTSC screen ratio format, shown for comparison.

• Advanced Television System Committee
(ATSC)
 Came up with 16 by 9 format
 Also defined standard definition television
(SDTV)

Video Signal
• ITU-R 601 4:2:2 format
• International standard for digitizing
component video
• Base sampling frequency of 3.375 MHz

Video Signal
• Luminance [Y]:Red-luminance [R-Y]:Blue-luminance [B-Y]
• 4 2 2
• Video signal composed of red, green, and blue (RGB)
• Luminance is the black and white detail
• Y, R-Y, and B-Y are converted to digital signal using Pulse Code
Modulation (PCM) at 3.375 MHz base rate.
• 10-bit sampling is used
• Luminance is sampled at 4 times the base rate
• Red-luminance and Blue-luminance at 2 times the base rate
• They are time-division-multiplexed (TDM) together at 270 Mbps

Video Signal
• Channel Sample Rate Bit Rate
• Luminance Channel 4 X 3.375 MHz = 13.5 MHz x 10 bits/sample = 135 Mbps
• R-Y channel 2 X 3.375 MHz = 6.75 MHz x 10 bits/sample = 67.5 Mbps
• B-Y channel 2 X 3.375 MHz = 6.75 MHz x 10 bits/sample = 67.5 Mbps
• Serial data bit rate of 270 Mbps = 135 + 67.5 + 67.5
• MPEG2 is used for data compression to fit in 6 MHz bandwidth
• Motion Pictures Expert Group (MPEG)

Audio Signal
• Digital Audio Compression (AC-3) developed by Dolby
Laboratories
• Provides five full-bandwidth audio channels (3 Hz to 20
kHz)
• Left, center, right, and left-right surround-sound channels
• Also one low-frequency enhancement channel at 3 Hz to
120 Hz
• 5.1 Channel Input (5 full and 1 reduced)
• 6 channels are multiplexed together to 5.184 Mbps
• Compressed to 384 kbps

Figure 17-2 A block diagram of the ATSC digital transmission system.

Transmission
• 8VSB – 8–level vestigial-sideband modulator
• I (In-phase) and Q (Quadrature)
• Exciter has 6 parts
 Frame synchronizer to synchronize the MPEG2 data packets
 Data randomizer to make data appear random to make the RF spectrum be flat across the
channel so data will fit in 6 MHz bandwidth
 REED Solomon Encoder for error correction
 Data Interleaver – interleaves data to reduce interference
 Trellis Encoder – more error correction
 Pilot/Sync Insertion

Figure 17-3 (a) The 8VSB and (b) the 64-QAM constellations. (Courtesy of Harris Broadcast.)

Figure 17-4 The 8VSB segment sync. (Courtesy of Harris Broadcast.)

Figure 17-5 The 8VSB frame sync. (Courtesy of Harris Broadcast.)

Figure 17-12 The display of the 8VSB constellation and the 8VSB eye diagram as displayed in the modulation detail
screen.

Figure 17-15 The RF spectrum for a DTV signal.

Figure 17-16 Simplified TV system.

Figure 17-17 An example of a CCD imaging device. (Courtesy of Hamaqmatsu Corp.)
CCD – Charge Coupled Device

Figure 17-18 Simplified scanning representation.

Figure 17-19 Interlaced scanning.

Video Signal
• Horizontal Retrace - Time to move from
end of one line back to start of next lower
line
• Vertical Flyback or retrace – time to move
from bottom line to the start of the top line
• FCC stipulates that NTSC broadcasts
have 525 horizontal scanning lines.
• 40 lines are lost as result of vertical
retrace interval, so only 485 visible lines

• Frame frequency – number of times per
second that complete set of 485 lines is
traced.
 30 times per second
• Flicker – need 60 frames per second so
human eye does not perceive difference
• Interlaced scanning is used to trick the
eye.

• First set of lines (first field) is traced in 1/60 second
• Second set of lines (second field) is then traced
• 485 lines are displayed, even lines first, then the odd
lines
• Horizontal sync between every line of video signal
• Horizontal sync for each of 525 lines in 1/30 second
• So 525 X 30 = 15.75 kHz is frequency of pulses

Figure 17-20 Horizontal sync pulses.

Figure 17-21 Vertical retrace interval video signal.

Figure 17-22 Transmitted TV signal.

Figure 17-23 TV receiver block diagram.

Figure 17-24 VHF/UHF tuner block diagram.

Figure 17-25 Stagger tuning.

Figure 17-26 SAW filter.

Figure 17-27 Ideal IF response curve.

Figure 17-28 Wavetraps.

Figure 17-29 Video section block diagram.

Figure 17-30 Sync separator.

Figure 17-31 Horizontal deflection block diagram.

Figure 17-32 Nonlinear horizontal scanning. (From Bernard Grob, Basic Television Principles and Servicing, 4th ed.,
1977; Courtesy of McGraw-Hill, Inc., New York.)

Figure 17-33 Horizontal system schematic.

28-Sep

Composite video
• Composite video is the format of an
analog television (picture only) signal
before it is combined with a sound signal
and modulated onto an RF carrier
• Contains four information groups
 Video Brightness information
 Horizontal Line Sync
 Vertical Line Sync
 Sound (Audio)

Composite Video
• A composite video signal combines on one wire the
video information required to recreate a color picture, as
well as line and frame synchronization pulses.
• The color video signal is a linear combination of the
luminance of the picture, and a modulated subcarrier
carries the chrominance or color information.
• Chrominance is a combination of hue and saturation.
• Hue is a pure color like red, green, or blue without tint.
• Saturation is the amplitude of a given color
• Tint is the shade of a color

Composite Video
Video
> 7.5 IRE
Sync
Pulses
< 0 IRE
0 IRE

Color TV
• Color TV started in 1953
• Compatible with monochrome
• Uses same 6 MHz bandwidth
• Needed to be displayed on monochrome
• Can use unused spaces in spectrum
by interleaving

Figure 17-34 Interleaving process.

Color Camera
• Uses 3 cameras in one – one for each color
 Red, Green, Blue
 3 cameras scan in unison
 Can create any color with these 3 primary
colors

Figure 17-35 Generating the electrical color signals (color camera).

• The 3 color signals are fed into a
transmitter processing circuit called the
matrix
• Creates the Y (luminance) and the chroma
or color signal (I and Q)
• Y signal has proportions of Red, Green,
and Blue to create a monochrome signal
for use on Black/White screens.
• The I and Q signals will contain the color
information.

Figure 17-36 Composite color TV transmission.

Figure 17-37 The composite color modulating signal.

Figure 17-38 Color receiver block diagram.

Figure 17-39 Color burst.

Figure 17-40 Color CRT construction.

To build a jumbo TV, you take thousands of these LED modules and arrange
them in a rectangular grid. For example, the grid might contain 640 by 480
LED modules, or 307,200 modules.
The computer system looks at the incoming TV signal and decides which
LEDs it will turn on and how brightly. The computer samples the intensity
and color signals and translates them into intensity information for the three
different LED colors at each pixel module.

Plasma TV

What is Plasma?
• The central element in a fluorescent light is a plasma, a
gas made up of free-flowing ions (electrically charged
atoms) and electrons (negatively charged particles).
• In a plasma with an electrical current running through it,
negatively charged particles are rushing toward the
positively charged area of the plasma, and positively
charged particles are rushing toward the negatively
charged area.
• In this mad rush, particles are constantly bumping into
each other. These collisions excite the gas atoms in the
plasma, causing them to release photons of energy.

Plasma TV
To ionize the gas in a particular cell, the plasma display's computer charges
the electrodes that intersect at that cell. It does this thousands of times in a
small fraction of a second, charging each cell in turn.

Plasma TV
• When the intersecting electrodes are charged (with a voltage
difference between them), an electric current flows through the gas
in the cell. The current creates a rapid flow of charged particles,
which stimulates the gas atoms to release ultraviolet photons.
• The released ultraviolet photons interact with phosphor material
coated on the inside wall of the cell. Phosphors are substances that
give off light when they are exposed to other light. When an
ultraviolet photon hits a phosphor atom in the cell, one of the
phosphor's electrons jumps to a higher energy level and the atom
heats up. When the electron falls back to its normal level, it releases
energy in the form of a visible light photon.

LCD Screens
• http://www.howstuffworks.com/lcd.htm

LCD
• The combination of four facts makes LCDs
possible:
• Light can be polarized.
• Liquid crystals can transmit and change
polarized light.
• The structure of liquid crystals can be
changed by electric current.
• There are transparent substances that can
conduct electricity.

• If we apply an electric charge to liquid
crystal molecules, they untwist. When they
straighten out, they change the angle of
the light passing through them so that it no
longer matches the angle of the top
polarizing filter. Consequently, no light can
pass through that area of the LCD, which
makes that area darker than the
surrounding areas

Digital TV
• Aspect ratio - Standard television has a 4:3 aspect ratio -- it is four
units wide by three units high. HDTV has a 16:9 aspect ratio, more
like a movie screen.
• Resolution - The lowest standard resolution (SDTV) will be about
the same as analog TV and will go up to 704 x 480 pixels. The
highest HDTV resolution is 1920 x 1080 pixels. HDTV can display
about ten times as many pixels as an analog TV set.
• Frame rate - A set's frame rate describes how many times it creates
a complete picture on the screen every second. DTV frame rates
usually end in "i" or "p" to denote whether they are interlaced or
progressive. DTV frame rates range from 24p (24 frames per
second, progressive) to 60p (60 frames per second, progressive).

When you hear someone mention a "1080i" HDTV set,
they're talking about one that has a native resolution of
1920 x 1080 pixels and can display 60 frames per
second, interlaced.

Figure 17-41 Color convergence yoke.

Enhanced Audio
• Zenith / dbx
• Similar to FM, but better signal

Figure 17-42 Zenith/dbx stereo system.

Figure 17-43 The Electronics WorkbenchTM Multisim circuit used to simulate the frequency spectra for a UHF
television signal.

Figure 17-44 The Electronics WorkbenchTM simulation of the frequency spectra for a channel 22 television signal.

Figure 17-45 The Electronics WorkbenchTM Multisim circuit of a high-Q bandstop circuit, or wavetrap.

Figure 17-46 The Bode plotter output for the wavetrap filter.

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