1. Satellite Communication
2011-2012
Various sources of Information &
Signals, their Characteristics and
Application
Batch 1
Ajay Kumar N (1RV08TE002)
Jagadeesh B (1RV08TE023)

2. Information
Information in its most restricted technical
sense is a message (utterance or expression)
or collection of messages that consists of
symbols in an ordered sequence, or it is the
meaning that can be interpreted from such a
message or collection of messages.

3. • Vast term
• Covers everything that we see around us
• Human Body is continuously processing
information

4. Information Sources in SatCom
Primary
• Speech
• Audio
• Video
• Data

5. Speech
• Bandwidth of 300-3400 Hz

6. Audio
• Ranges upto 20 Khz (sensitivity of Human Ear)

7. Video
• Ranges upto 5 Mhz
• Must usually be synced with Audio

8. Signals
A signal is a changing value of electric voltage or
current through a transmission medium.
Types
• Periodic : Periodic signals repeat themselves after
a certain period of time -- after they have cycled
through one period, following periods don't
contain any new information.
• Aperiodic : Aperiodic signals don't repeat
themselves, and therefore can contain
information.

9. Signals
Classification
• Analog-Continuous in nature
• Digital-Discrete in nature

10. Analog Signals
• Analog signals are electrical replicas of the original signals such as audio
and video.
• Baseband signals are those signals which occupy the lowest, or base, band
of frequencies, in the frequency spectrum used by the
telecommunications network.
A baseband signal may consist of one or more information signals. For
example, a number of analog telephony signals may be combined into one
baseband signal by the process known as frequency-division multiplexing
(FDM).
• Other common types of baseband signals are the multiplexed video and
audio signals which originate in the TV studio.
In forming the multiplexed baseband signals, the information signals are
modulated onto subcarriers. This modulation step must be distinguished
from the modulation process, which places the multiplexed signal onto
the microwave carrier for transmission to the satellite.

11. The Telephone Channel
• Natural speech, including that of female and
male voices, covers a frequency range of
about 80 to 8000 Hz.
• The range of 300 to 3400 Hz is accepted
internationally as the standard for “telephone
quality” speech, and this is termed the speech
baseband.

12. • Noise, which covers a very wide frequency
spectrum, is reduced by reducing the band
width.
• Reducing the bandwidth also allows more
telephone channels to be carried over a given
type of circuit

13. DSBSC Telephony
• When the telephone signal is multiplied in the
time domain with a sinusoidal carrier of
frequency fc, a new spectrum results, in which
the original baseband appears on either side
of the carrier frequency.
• The band of frequencies below the carrier is
referred to as the lower sideband and the
band above the carrier as the upper sideband

14. • Only the sidebands, and not the
carrier, appear in the spectrum
• To avoid distortion, the carrier frequency must
be greater than the highest frequency in the
baseband.

15. Single-Sideband Telephony
• All the information in the original telephone
signal is contained in either of the two sidebands,
and therefore, it is necessary to transmit only one
of these.
• For the lower sideband, the frequencies have
been inverted, the highest baseband frequency
being translated to the lowest transmission
frequency and the lowest baseband frequency to
the highest transmission frequency.

16. • Companded single sideband (CSSB) refers to a technique in
which the speech signal levels are compressed before
transmission as a single sideband, and at the receiver they are
expanded again back to their original levels
• The expander decreases attenuation when a speech signal is
present and increases attenuation when it is absent, thereby
reducing idle noise.

17. FDM Telephony
• FDM provides a way of keeping a number of individual
telephone signals separate while transmitting them
simultaneously over a common transmission link circuit.
• Each telephone baseband signal is modulated onto a
separate subcarrier, and all the upper or all the lower
sidebands are combined to form the frequency-multiplexed
signal
• Each voice channel occupies the range 300 to 3400 Hz, and
each is modulated onto its own subcarrier.
• The subcarrier frequency separation is 4 kHz, allowing for
the basic voice bandwidth of 3.1 kHz plus an adequate
guardband for filtering.

18. CCITT Modulation Plan
• Group-consists of 12 channels
• Supergroup-consists of 5 Groups
• Basic mastergroup-consists of 5 Supergroups
• Super mastergroup-consists of 3 Basic
mastergroups

19. FDM Scheme

20. Color Television
• The baseband signal for television is a composite
of the visual information signals and
synchronization signals
• The visual information is transmitted as three
signal components, denoted as the Y, I, and Q
signals
• Y signal is luminance
• I and Q signals are chrominance components
• Chrominance signal bandwidth is less than that of
the luminance signal since eye can resolve
intensity better than colors

21. Frequency Spectra for Luminance and Chrominance Signals
One line Waveform for Color TV Signal

22. Generation of NTSC color TV signal.

23. Analog TV Broadcasting of Video and Audio Signals
Generation of Satellite Uplink Signal

24. Applications
• AM
• FM
• POTS
• Sensors

25. Analog
Advantages
• Accurate
• Simple
• Less Bandwidth
Disadvantages
• Noise

26. Digital Signals
• Analog signals can be converted into digital
signals for transmission.
• Digital signals may also originate in the form
of computer and other data.
• In general, a digital signal is a coded version of
the original data or analog signal

27. Examples of binary data sources

28. Unipolar NRZ
Polar NRZ
Polar RZ
Manchester
Alternate Mark Inversion
Encoding of Digital Data

29. Digital Modulation Schemes

30. Applications
• Audio signal processing
• Audio compression
• Digital image processing
• Video compression
• Speech processing
• Speech recognition
• RADAR
• SONAR
• Biomedicine

31. Digital
Advantages
• Less expensive
• More reliable
• Easy to manipulate
• Flexible
• Security
• Digitized information can be transported through
a noisy channel without degradation

32. Disadvantages
• Complex Circuitry
• Sampling Error
• More Bandwidth
• Synchronization

33. Conclusion
• Overall , digital signals are better than analog
signals because of various advantages
• Application wise , digital signal processing has
a wider gamut of uses compared to analog
signal processing