Main characteristics of human eye with regard to perception of colours-mixing of colours. three standards of colour transmission system, CATV, DTH, HDTV & SMART TV For TS-SBTET, C-18, DECE 6 Unit, By Nenavath Ravi Kumar, MIST Hyderabad

1. MICROWAVE COMMUNICATIONS AND TELEVISION
DECE, II YEAR-IV SEMESTER
Nenavath Ravi Kumar
Associate Professor
ECE Dept-MIST

2. UNIT-6
Basics of Colour Television and
Digital TV

3. INTRODUCTION TO COLOUR TV
• The first commercial colour TV started in US in 1954
• The main constraint for the design of color TV was maintaining
compatibility with existing monochrome TV
• Compatibility:
– Colour TV signal must produce normal monochrome picture
on monochrome TV
• Reverse Compatibility:
– Monochrome signal must produce a normal monochrome
picture on colour TV

4. INTRODUCTION TO COLOUR TV
Requirement for achieving compatibility:
 Colour TV signal should occupy the same BW
 Location of picture and sound carriers should be the same
 The colour signal should have the same luminance (brightness)
information as B&W TV
 The composite colour signal should contain colour information
and other ancillary signals
 The colour information should not not affect the picture
reproduced on the screen of a monochrome receiver.
 The system must use the same deflection frequencies.

5. CONCEPT OF COLOR
 What is color?
Color is the light wavelengths that the human eye receives and
processes from a reflected source. When light shines on an
object some colors bounce off the object and others are
absorbed by it. Our eyes only see the colors that are bounced
off or reflected.
 How do we see color?
The inner surfaces of our eyes contain photoreceptors—
specialized cells that are sensitive to light and relay messages
to our brain. There are two types of photoreceptors: cones
(which are sensitive to color) and rods (which are more
sensitive to intensity). We are able to “see” an object when
light from the object enters our eyes and strikes these
photoreceptors. Light with a wavelength of about 400 nm is
seen as violet, and light with a wavelength of about 700 nm is
seen as red.

6. COLOUR PERCEPTION
 All colours are perceived
by human eye by the
stimulation of the three
groups of the cones at
different levels
 The sensitivity of human
eye is maximum for green
light (550nm)

7. COLOUR MIXING
Subtractive Mixing
• The combination of two
colours reflects only the
colours which are
common to both
• Uses the reflective
property of the
pigments
• Used in painting and
printing
Additive Mixing
 Light from 2 or more
colours obtained either
from independent
sources or through
filters can create a
combined sensation of
a different colour
 Used in TV systems

8. COLOUR MIXING
 Additive mixing  Subtractive mixing

9. COMPLIMENTARY COLOURS
 The colours which are obtained by pair wise
additive mixing of primary colours are know as
complimentary colours
 Red + Green = Yellow
 Red + Blue = Magenta
 Blue + Green = Cyan

10. TRISTIMULUS VALUES
• The values of the individual colour components to get a
particular colour is known as the tristimulus values
• The wavelengths of red (700nm), green(546.1nm) and
blue(438.8nm) are standardized to make different colours by
additive mixing
• The relative strengths of these components for getting different
colours also have been standardized
• E.g. white= 30% red + 59% green + 11% blue
• i.e. 1 lumen white= 0.3 lumen red+0.59 lumen green + 0.11
lumen blue

11. LUMINANCE, HUE & SATURATION
 Luminance (Brightness): Amount of light intensity perceived
by the eye regardless of the colour
 Hue (tint): This is the spectral colour of the light
- Different hue due to different wavelengths and perceived
by the cones of the retina
- Eg: red apple is red due to red hue
 Saturation: Spectral purity of the colour.
- Saturation indicates whether a colour is diluted (by mixing
with white) or not.
- Saturation 100% means no white component
 Hue and saturation put together is known as Chrominance

12. CHROMINANCE SIGNAL
 Chrominance signal contains all the colour
information.
 It indicates both the hue & saturation of colour.
 Chrominance signal is also called the c-signal
 Chrominance signal obtained from the colour
difference signals R-Y & B-Y, a colour difference
signal can be produced by adding the Y signal with
its phase reverse –Y to any of the signals R,B or G
of the three possible colours difference signal, R-Y,
B-Y & G-Y.

13. PRODUCTION OF COLOR DIFFERENCE SIGNAL
•Voltage Vy is low because Rc is chosen to be small to avoid crosstalk. Hence
it is amplified before it leaves camera subchassis.
•Also the amplified Y signal is inverted to obtain –Y signal
•Then two adder circuits to obtain (R-Y) and (B-Y)

14. COMPATIBILITY AND REVERSE COMPATIBILITY
 Colour television signal
must produce a normal
black & white picture on
monochrome T.V receiver
without any modification
of the receiver circuitry.
This is known as
‘Compatibility’
 A colour receiver must be
able to produce a black &
white picture from a
normal monochrome
signal. This is referred to
as ‘Reverse
Compatibility’

15. COMPATIBILITY AND REVERSE COMPATIBILITY
 The following requirements are needed for
compatibility.
 The colour signal should occupy the same bandwidth as
the monochrome
 The location and spacing of picture and sound carriers
should be same as in monochrome signal.
 The colour system has to employ the same deflection
frequencies and sync signals as the monochrome system.
 The channel bandwidth is also required to be same as
the monochrome system.

16. COLOUR TRANSMISSION SYSTEM
Composite Video Signal
 Encoding the Chrominance over Luminance into one
signal (saving bandwidth):
 NTSC (National TV System Committee) North America,
Japan –
 PAL (Phased Alternation Line) Europe (Including Israel) –
 SECAM (Systeme Electronique Color Avec Memoire)
France, Russia and more

17. HOW CHROMINANCE SIGNALS ARE TRANSMITTED
ON ONE CARRIER IN PAL SYSTEM
 The modulated picture sub-carrier containing the
colour information is to be accommodated in the
standard TV channel bandwidth(7MHz).
 This channel width is already fully occupied by the
luminance signal which has bandwidth of 5MHz.
 This problem is solved by employing a method is
known as frequency interleaving.
 frequency interleaving is the process of
accommodating colour information signals between
the vacant spaces of clusters.

18.  Each cluster consists of harmonics of line
frequencies (H, 2H,3H, 4H......NH) i.e.
1Hz=1x15625 = 15625Hz
2Hz=2x15625 = 15625Hz
3Hz=3x15625 = 15625Hz
4Hz=4x15625 = 15625Hz
..
..
..
320Hz=320x15625 = 5MHz

19. FREQUENCY INTERLEAVING
• The colour signal is interleaved in these gaps
• The carrier frequency is so chosen that its sideband
frequencies fall exactly mid-way between the harmonics
of the line frequency.
• This requires that the frequency of the subcarrier must be
an odd multiple of half the line frequency.
• i.e. (2n+1)* 15625/2
• In 625 line system, this freq. is selected as 4.43MHz
(2*283+1)*15625/2
• In 525 line system it is 3.58MHz

20. FREQUENCY INTERLEAVING

21. BLOCK DIAGRAM OF COLOUR TV TRANSMITTER
C Signal
1
2

22. BLOCK DIAGRAM OF COLOUR TV TRANSMITTER
 Colour camera: The scene to be televised is separated
into R,G & B.
 Colour matrix: Separate luminance signal (Y) &
chrominance signals (R-Y & B-Y) using suitable matrix.
 LPF: Limits chrominance signals bandwidth 1.5MHz.
 Modulators: Chrominance signals are Amplitude
modulated by colour subcarrier signals of 6.8MHz.
 Colour subcarrier generator: Generates 4.43MHz.
 Adder: Adder 2 adds both chrominance modulated signals
it is C-signal and Adder 1 adds C-signal and Y-signal is the
composite colour video signal.
 Main transmitter: Using antenna radiates Colour video
signal and Audio signal into space.

23. BLOCK DIAGRAM OF COLOUR TV RECEIVER

24. BLOCK DIAGRAM OF COLOUR TV RECEIVER
 RF Tuner: Selects only band TV signals.
 Video IF Amplifier: To boost received TV signals
 Video detector & Video Amplifier: To detects Video signal and
separate C-signal, Y-signal & sync signal Audio & Video Signal.
 Detector: Amplitude demodulation of Chrominance signals.
 Colour subcarrier generator: Generates 4.43MHz.
 Phase reverse switch: 90 degrees phase shift.
 Matrix: To generate (R-Y), (G-Y), and (B-Y) from chrominance
signals (R-Y & B-Y) .
 Matrix 1: (R-Y), (G-Y), and (B-Y) colour difference signals are
added with Y-signal in the matrix and generates R,G & B signals
fed to tri colour picture tube.
 Sync pulse: pulses are separated and fed to vertical &
horizontal deflection circuits to deflect to electron beam.

25. PROCESSING OF COLOUR VIDEO SIGNAL (PAL-
SYSTEM)-PAL-DECODER
U+jV
U+jV
U-jV

26. PROCESSING OF COLOUR VIDEO SIGNAL (PAL- SYSTEM)-PAL-DECODER
 The received signal from Rx Antenna fed to Video detector
(Chroma Signala). The output of Video detector connected Y-
Amplifier & BPF of 3-5 MHz.
 The problem of cross interference (distortion) between U and V
signals in the video detector’s output is solved by using delay
circuit of 64us before U&V signals.
 At the added & subtraction we get
Assume U+jV Direct signal
U-jV Delay Line signal
The j operator with V-signal indicates that V is at 90 degree phase difference with U-
signal.
 Adding two expressions to get 2U signal at the added output i.e
U+jV+U-jV=2U
 Subtraction of expressions to get 2jV signal at the added output
i.e U+jV-U-JV= 2jV.
 These U & V signals are added in the matrix to produce R-Y, G-Y
& B-Y signals.
 These three colour signals and Y-signal is added in the RGB
matrix to produce R, G & B colours.

27. PAL-DECODER
 Advantages :
 -The phase error causing error in reproduction of colour is
eliminated
 -Bandwidth of U & V is same .This simplifies filtering action
 -Studio mixing is easy as compared to SECAM
 -Use of delay lines before demodulators isolates U and V
signal s from each other reduces crosstalk type of interference
in colours better than NTSC-results in better picture quality
 Disadvantages:
 -Electronic circuit and Ident signals are necessary in PAL which
makes the design complex
 -Delay line technique reduces vertical resolution of chroma
signal

28. PROCESSING OF COLOUR VIDEO SIGNAL (PAL-
SYSTEM)-PAL-ENCODER

29. PROCESSING OF COLOUR VIDEO SIGNAL (PAL- SYSTEM) -
ENCODER
 The R, G & B signal for the camera are combined in the Y-
matrix to form Y-signal.
 The U-V matrix combines the R&B signal with –Y signal to
obtain U & V signals.
 The colour subcarrier is modulated in the quadreture by the
U & V Signal.
 The colour subcarrier is fed to the U modulator over a 90
degree phase shift network while the V modulator gets the
subcarrier over a 0 to 180 phase shift switched in every
alternate line by electronic commutator.
 Two modulated chrominance signal U & ± jV signal are
combined in the adder stage and the F-signal is obtained.

30. CABLE TV SYSTEM
 Introduction to cable TV
 Basically cable TV system is classified as
1) MATV(master antenna TV)
2) CCTV(close circuit TV)
3) CATV(cable TV)
 Cable TV was initially introduce for the benefit is possible of
communication in rural area that were beyond the range of
broadcast transmission
 However with the advent of satellite television, reception of
signal from a large number of TV station located far away
become possible.
 With this cable TV developed in a complex multi channel
system and expanded in a big way in all countries.

31. CABLE TV SYSTEM
 Cable sig.nal resources
 The first step in cable TV is to collect the desired signal
from available source.
 The main signal coming from various satellite. for that
purpose high gain antenna is required.
 By correct adjustment of this antenna towards satellite,
collect signal arriving from it by dish and deliver these to
LNBC. this minimize the losses in co axial cable.
 Principle: The parabolic reflector antenna collects all the
electromagnetic waves from satellite due to parabolic
shape reflected rays concentrated at focal point which give
the high gain signal.

32. CABLE TV SYSTEM
 Specification of Dish Antenna:
 Size - 8feet.
 Gin - 36db.
 Band –c (3.7 to 4.2GHz downlink frequency)
 Look angle - 360 rotation in azimuth.
 Offset angle - 24.62limit
 Focal length - 90cm
 Azimuth angle= 0 to 360
 Aperture efficiency -75%

33. SIMPLE BLOCK DIAGRAM OF CABLE TV SYSTEM

34. DIAGRAM OF CABLE TV SYSTEM FUNCTION
 Head-end: Broadcast signals are received from the various satellite by
using antennas. They are amplified by a low noise amplifier (LNA).
 Trunk Lines: Trunk lines are coaxial cables are used to provide the
high bandwidth low noise.
 Trunk Amplifiers: Trunk amplifiers are used between trunk lines
(coaxial cables) to compensate for signal loss in cables and to increase
the distance of the signal without losses.
 Signal Splitters: Signal splitters are also directional couplers. This can
be used to distribute cable signal from trunk lines to ranch routes.
 The Branch Line Cable: The branch line comes out of the main trunk
line. It is also
 Bridge Amplifier: The bridge amplifier to act as bridge between trunk
line and the branch line. Care of impedance matching.
 Drop Line: It is the from branch line to subscriber home TV.
 Line Extension Amplifiers: When branch line is to be extended a line
extension amplifier becomes necessary to amplify signals and hence it
is called line extender

35. NEED OF SATELLITE FOR DTH
 CA TV system uses coaxial cable for connecting the television
sets to the head end so the cost of system increases with
distance of consumers from the head end.
 Signal strength decreases with increasing distance which
requires amplifiers for specified distance which again increase
the cost of the system
 Illegible tapings are possible along the coaxial cable.
 CA TV systems are not able to provide services in remote
areas such as forests, hilly regions, rural areas etc.
 Early satellite television was broadcast in C-band - radio in the
3.4 gigahertz (GHz) to 7-GHz frequency range. Digital
broadcast satellite transmits programming in the Ku frequency
range (10 GHz to 14 GHz).
 Doordarshan TV is India's biggest broadcast with over 1400
territories and covering approximately 90% of geographical
area.

36. COMPONENTS OF DTH
 The major components of DTH are
 Satellites
 Signal Processing (Broadcasting centre, Multiplexers, Modulators)
 DTH Antenna
 LNB
 Set-top Box
 Schematic Picture of DTH :

37. SATELLITE
 A Geo-Stationary satellite plays an important role in DTH
systems. Satellites are higher in the sky than TV antennas, so
they have a much larger "line of sight" range.
 The television satellites are all in geosynchronous orbit,
meaning that they stay in one place in the sky relative to the
Earth.
 In India DD Direct & Dish TV transmission services are from
NSS-6 Satellite.
 Specifications of NSS-6 Satellite :
• Location : 95 degree East
• No. of Ku-Band Transponders : 60
• Ku Band Uplink : 13.75 to 14.5 GHz
• Ku Band Down link : 10.95 to 11.70 GHz
• Modulation Type : QPSK
• Symbol Rate : 27.5 Mb/s.
• Downlink for DD Direct : 12815, 12534, 12898 GHz.
• Altitude = 57.26 degree

38. BROADCAST CENTRE:
 The provider doesn't create original programming itself; it pays
other companies (HBO, for example, or ESPN) for the right to
broadcast their content via satellite. In this way, the provider is
kind of like a broker between you and the actual programming
sources.
 The broadcast centre is the central hub of the system.
 The satellites receive the signals from the broadcast station
and rebroadcast them to the ground.
 The viewer's dish picks up the signal from the satellite (or
multiple satellites in the same part of the sky) and passes it on
to the receiver in the viewer's house. The receiver processes
the signal and passes it on to a standard television.
 With MPEG-2 compression, the provider can reduce the 270-
Mbps stream to about 5 or 10 Mbps (depending on the type of
programming).
 With digital compression, a typical satellite can transmit about
200 channels.

39. MULTIPLEXER & MODULATOR
 A multiplexer is a device which transmits the information
of many channels in one channel.
 The multiplexer is built in the broadcasting centre.
 The multiplexer in the broadcasting centre compresses
all the frequency signals into one single channel &
transmits it to the GeoStationary satellite.
 It sends the single channel to the modulator.
 Modulation is a process in which the information signal is
imposed on a carrier signal which is of high strength and
greater frequency.
 This process is done in the modulator.
 The modulator modulates the signals and sends to the
encoder

40. DTH ANTENNA
 The reflector's surface material
must be constructed out of metal
in order to reflect the incoming
microwave signals.
 Some antenna reflectors appear
to be manufactured out of plastic
or fibre glass; however, these
dishes actually have an embedded
metal mesh material that reflects
the incoming satellite signals to
the front and centre of the dish.
Dish Antenna

41. LNB (LOW NOISE BLOCK DOWN CONVERTER):
 The incoming satellite signal propagates
down the waveguide of the feed horn
and exits into a rectangular chamber
mounted at the front of the low-noise
block down converter (LNB), in which a
tiny resonant probe is located.
 This pickup probe, which has a
wavelength that resonates with the
incoming microwave frequencies,
conducts the signal onto the first stage
of electronic amplification.
 A wide band product called a "universal"
Ku-band LNB is available that can
switch electronically between the 10.7-
11.7 and 11.7-12.75 GHz frequency
spectra to provide complete coverage of
the entire Ku-band frequency range.

42. SET-TOP BOX:
 The set top box accepts the entire down converted band and
separates out the individual transponder frequency.
 Then signals are first converted to fixed IF and then QPSK
demodulated.
 The bandwidth of QPSK signals is 27.5 MHz as the bit rate is
27.5 Mb/s.
 It is observed that 11 digital channels are multiplexed in 27.5
MHz bandwidth.
 After the QPSK demodulation, the digital bit stream obtained
contains several multiplexed channels as well as error control
bits.
 The bit stream is processed to correct and detect errors,
deinterleaved, and decrypted.
 A digital demultiplexer then extracts the bits for wanted
channel, and sends them to MPEG decoder, and finally
generates analog Audio and Video signals with DIA converters
to drive TV set.

43. DEFICIENCIES IN EXISTING TV SYSTEM
 Present TV signals can’t project the vivid (pure)
impressions and emotions as the 35mm.
 Line visibility when brightness is high.
 Unpleasant when the viewer is close to the screen.
 Narrow aspect ratio of 4:3 and small screen size
permits the small viewing angle of around 15
degrees.
 Peripheral vision is not involved in viewing the
picture. Need not to move the eyes or head to the
follow the action

44. HOW DOES. DTH DIFFER FROM CABLE TV
 In DTH channel should be transmitted from the satellite to
a small dish antenna mounted on the window or roof top of
the user house
 So the broadcast directly contact to the user.
 The middle man like cable operator are not there in picture.
 Also with DTH a user can see nearly 700 channels.
 DTH offer better quality picture than cable TV.
 This is because cable TV in India is analog.
 DTH offer stereophonic sound effect.
 It can also reach remote terrestrial area
where transmission and cable TV have filed to penetrate.

45. HIGH DEFINITION TV (HDTV)
 Is a digital television broadcasting system.
 HDTV is simply the highest of all the DTV standards
 HDTV is digitally broadcast because digital television (DTV)
requires less bandwidth if sufficient video compression is used.
 pictures look so much sharper and clearer than regular TV.
 HD get its clarity from a feature called Resolution. Resolution
means the amount of visual information in a picture.
 The number of pixels which gives resolution.
 A pixel is a tiny square or rectangle. Each pixel creates one tiny
dot of colour. Many pixels combine to form an image on
screen.
Higher Pixels equals higher resolution and a better picture

46. HIGH DEFINITION TV (HDTV)
 HDTV aims at:
 Improvement in both vertical and horizontal resolution of reproduced
picture by approximately 2:1 over existing standard.
 Much improved color reproduction
 Higher aspect ratio of at least 5:3
 Stereophonic sound.
 Development of HDTV
 Pioneer-NHK, Japan Broadcasting corporation Tokyo
 Standard adopted include 1125 scanning lines per frame, 60 fields per
second,2:1 interlace scan and aspect ratio 16:9.
 Compatible to Europe’s 625 line PAL standard and America’s 525 line
NTSC standard.
 MUSE stands for Multiple Sub-Nyquist Sampling Encoding and is an
HDTV bandwidth compression scheme developed by NHK.
 Europe developed their own project named EUREKA compatible with
CCIR standard but line number equal to 1249 and aspect ratio 16:9

47. STANDARD OF HDTV
 1125/60/2:1 Interlace
System
1. Number of scanning
lines:1125
2. No of active lines:1035
3. Aspect ratio: 16:9
4. Scanning :2:1 Interlace
5. Field frequency : 60 Hz
6. Samples for active lines:
960 for colour different
1920 for lumirances
 1250/50/1:1 Progressive
Scanning:
1. Number of scanning
lines:1250
2. No of active lines:1152
3. Aspect ratio: 16:9
4. Scanning :1:1 Interlace
5. Field frequency : 50 Hz

48. SMART TV
 Smart TV sometimes
referred to as connected TV
or Hybrid TV
 Smart TV either have an
ethernet port or Wi-Fi
capability so we can stay
connected to internet.
 In smart TV, the operating
system is preloaded or
available through set-top
box

49. FEATURES OF SMART TV
 Internet:
 High Quality Crystal Clear Picture:
 Miracast:
 Sharing Photos & Videos:
 High Resolution Videos:
 4X Graphics Engine:
 Advanced Image Quality Enhancement Technology
 Experience dbx Surround Sound
 High Apect Ratio

50. CONTACT FOR
Thank you