1. Pengantar Teknik Elektro Telekomunikasi II

2. Standar Kompetensi
Mahasiswa mampu memahami konsep dan persamaan dasar bidang telekomunikasi

3. Rujukan
Tarmo Anttalainen, Introduction to Telecommunications Network Engineering, 2003

4. A Communications Model

5. Communication Systems

6. Basic Digital Communications System
Baseband
Passband
audio
video
(analogue)
data
(digital)
A/D
Channel
Code
Modulation
ASK
FSK
PSK
binary
M’ary
anti-alias
filter
•Nyquist
sampling
FEC
ARQ
block
convolution
pulse
shaping
filter
ISI
channel
filter
Source
Source
code
Communications
Channel
loss
interference
noise
distortion
Transmit
Receive
data
(digital)
audio
video
(analogue)
Source
decode
Sink
D/A
Channel
Decode
Regeneration
Demodulation
low pass
filter
quantisation
noise
matched filter
decision threshold
timing recovery
envelope
coherent
carrier recovery
channel
filter
FEC
ARQ
Block
Convolution

7. Communication Channels
A channel is a path between two communication devices
Channel capacity: How much data can be passed through the channel (bit/sec)
Also called channel bandwidth
The smaller the pipe the slower data transfer!
Consists of one or more transmission media
Materials carrying the signal
Two types:
Physical: wire cable
Wireless: Air
destination network server
T1 lines
T3 lines

8. Physical Transmission Media
A tangible media
Examples: Twisted-pair cable, coaxial cable, Fiber-optics, etc.
Twisted-pair cable:
One or more twisted wires bundled together (why?)
Made of copper
Coax-Cable:
Consists of single copper wire surrounded by three layers of insulating and metal materials
Typically used for cable TV
Fiber-optics:
Strands of glass or plastic used to transmit light
Very high capacity, low noise, small size, less suitable to natural disturbances

9. Physical Transmission Media
plastic outer coating
woven or braided metal
insulating material
copper wire
twisted-pair cable
twisted-pair wire
protective coating
glass cladding
optical fiber core

10. The Electromagnetic Spectrum
Frequency and wavelength. (a) One cycle. (b) One wavelength.

11. The Electromagnetic Spectrum
Frequency and Wavelength: Wavelength
Wavelength (λ) = speed of light ÷ frequency
Speed of light = 3 × 108 meters/second
Therefore:
λ = 3 × 108 / f
Example:
What is the wavelength if the frequency is 4MHz?
λ = 3 × 108 / 4 MHz
= 75 meters (m)

12. Gain, Attenuation, and Decibels
Most circuits in electronic communication are used to manipulate signals to produce a desired result.
All signal processing circuits involve:
Gain
Attenuation

13. Gain, Attenuation, and Decibels
Gain means amplification. It is the ratio of a circuit’s output to its input.
AV = =
output
input
Vout
Vin
An amplifier has gain.

14. Gain, Attenuation, and Decibels
Most amplifiers are also power amplifiers, so the same procedure can be used to calculate power gain AP where Pin is the power input and Pout is the power output.
Power gain (Ap) = Pout / Pin
Example:
The power output of an amplifier is 6 watts (W). The power gain is 80. What is the input power?
Ap = Pout / Pin therefore Pin = Pout / Ap
Pin = 6 / 80 = W = 75 mW

15. Gain, Attenuation, and Decibels
An amplifier is cascaded when two or more stages are connected together.
The overall gain is the product of the individual circuit gains.
Example:
Three cascaded amplifiers have power gains of 5, 2, and 17. The input power is 40 mW. What is the output power?
Ap = A1 × A2 × A3 = 5 × 2 × 17 = 170
Ap = Pout / Pin therefore Pout = ApPin
Pout = 170 (40 × 10-3) = 6.8W

16. Gain, Attenuation, and Decibels
Attenuation refers to a loss introduced by a circuit or component. If the output signal is lower in amplitude than the input, the circuit has loss or attenuation.
The letter A is used to represent attenuation
Attenuation A = output/input = Vout/Vin
Circuits that introduce attenuation have a gain that is less than 1.
With cascaded circuits, the total attenuation is the product of the individual attenuations.

17. Gain, Attenuation, and Decibels
Total attenuation is the product of individual attenuations of each cascaded circuit.

18. Gain, Attenuation, and Decibels
The decibel (dB) is a unit of measure used to express the gain or loss of a circuit.
The decibel was originally created to express hearing response.
A decibel is one-tenth of a bel.
When gain and attenuation are both converted into decibels, the overall gain or attenuation of a circuit can be computed by adding individual gains or attenuations, expressed in decibels.

19. Gain, Attenuation, and Decibels
Decibels: Decibel Calculations
Voltage Gain or Attenuation
dB = 20 log Vout/ Vin
Current Gain or Attenuation
dB = 20 log Iout/ Iin
Power Gain or Attenuation
dB = 10 log Pout/ Pin