Modul

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Modul 3Sistem Transmisi

• TE-09-1313
• 2 sks
• Tim Bidang Studi
• Telekomunikasi Multimedia
• (Achmad Ansori, Devy Kuswidiastuti, Gatot
  Kusrahardjo, M Aries Purnomo)

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The use of the decibel and of relative levelsin
speechband telecommunications
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In transmission engineering, most often it would
be rather impractical to characterize the
magnitude of signals directly by a numerical
value in volts or watts. Instead, a logarithmic
measure is used, expressed in "dB", to
characterize the signal magnitude in relation to
some chosen reference value. Designations
commonly used are "power level difference",
"voltage level difference", etc., all expressed
in "dB". A level difference from a standard
situation is described simply as "level".
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Fundamentals about dB Alexander Graham Bell The
bel (symbol B) expresses the ratio of two powers
by the decimal logarithm of this ratio. This
unit is not often used, having been replaced by
the decibel (symbol dB) which is one-tenth of a
bel.
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Bel

• Unit dari ukuran perubahan daya
• Bel Log (P1/P2)
• P1 dan P2 dalam satuan yang sama
• ( Watt, mWat, kWatt )

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Daya, Tegangan dan Arus

• Daya Tegangan x Arus
• Satuan
• Daya Watt , Tegangan Volt , Arus Ampere
  (Amp)
• P V x I
• V I x R
• dimana R tahanan, Ohm (?)

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Bel dan Perubahan Tegangan

• P V x I V²/R , dimana V tegangan (Volt),
• I arus (Amp), R tahanan (Ohm, ?)
• Bel Log P1/P2 Log (V1²/R1) / (V2²/R2) Log
  (V1/V2)².(R2/R1) Log (V1/V2)² Log(R2/R1) 2
  Log(V1/V2) Log(R2/R1)
• Bel 2 Log (V1/V2), jika R1 R2

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Bel dan Perubahan Arus

• P V²/R (I x R)²/R I²/R
• Bel Log P1/P2 Log(I1²/R1)/(I2²/R2)
  Log(I1²/I2²)(R1/R2) Log(I1/I2)² Log(R1/R2)
• Bel 2 Log I1/I2 Log R1/R2
• Bel 2 Log I1/I2 , jika R1 R2

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Ringkasan (1)

• Bel Log P1/P2
• Bel 2 Log V1/V2 , jika R1 R2
• Bel 2 Log V1/V2 Log R2/R1 ,
• jika R1 ? R2
• Bel 2 Log(V1?R2)/V2?R1) ,
• jika R1 ? R2

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Ringkasan (2)

• Bel 2 Log I1/I2 , jika R1 R2
• Bel 2 Log I1/I2 Log R1/R2 ,
• jika R1 ? R2
• Bel 2 Log (I1?R1)/(I2?R2) ,
• jika R1 ? R2

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DECIBEL (1)

• Unit yang menyatakan ratio
• Bentuk logaritma dengan dasar 10
• Decibel ( dB ) 10 Log ( power ratio )

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Decibel (2)

• Decibel ( dB) 10 x Bel
• dB 10 Log P1/P2
• Jika R1 R2
• dB 20 Log V1/V2
• dB 20 Log I1/I2

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Decibel (3)

• Jika R1 ? R2
• dB 20 Log V1/V2 10 Log R2/R1
• dB 20 Log I1/I2 10 Log R1/R2
• dB 20 Log (V1?R2)/(V2?R1)
• dB 20 Log (I1?R1)/(I2?R2)

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Power Ratio Voltage Ratio (1)
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Power Ratio Voltage Ratio (2)
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Power Ratio Voltage Ratio (3)
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(No Transcript)
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Pengembangan Unit dB

• dBm 10 Log ( power ratio ) dg ref. 1 mW
• dBm 10 Log ( power / 1mW )
• dBW 10 Log ( power ratio ) dg ref. 1 W
• dBW 10 Log ( power / 1W )
• power output 20 W
• 10 Log (20W/1mW)
• 10 Log (20.000mW/1mW) 43 dBm

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dBm, dBW, Watt milliWatt
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Voltage Current Ratio

• dB(Voltage) 20 Log ( ratio voltage )
• dB(Current) 20 Log ( ratio current )

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dBmV

• Digunakan pada transmisi video
• Tegangan ( Voltage ) referensi 1 mVolt pada
  beban 75 Ohm
• dBmV 20 Log ( tegangan/1 mVolt )

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dBmV
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dBµV/m

• Pengukuran kuat medan listrik
• Referensi 1µV/m ? dBµV/m 20 Log (µV/m)

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KONSEP SISTEM TRANSMISI Loss Gain
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• attenuation, loss
• A decrease between two points of an electric,
  electromagnetic
• or acoustic power.
• 2. The quantitative expression of a power
  decrease, by the ratio
• of the values at two points of a power or of
  a quantity related to
• power in a well-defined manner.
• NOTE 1 By extension, the words attenuation or
  loss may represent the
• ratio of powers in a given
  situation and in a reference condition
• for example insertion loss.
• NOTE 2 Although the term loss is not
  synonymous in English with
• attenuation in every context,
  it is used to express the ratio of two
• powers in certain specified
  conditions as for example in insertion
• loss and return loss
  equivalent in French to
• affaiblissement d'insertion and
  facteur d'adaptation.
• NOTE 3 Attenuation is generally expressed in
  logarithmic units by a positive
• value.
• In some cases, attenuation could
  be used instead of gain, when
• the logarithmic unit value of a
  gain is negative.

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Gain 1. An increase between two points of an
electric, electromagnetic, or acoustic
power. 2. The quantitative expression of a power
increase, by the ratio of the values at two
points of a power or of a quantity related to
power in a well-defined manner. NOTE 1 By
extension, the word gain may represent the
ratio of powers in a given
situation and in a reference condition
for example the gain of an antenna. NOTE
2 Gain is generally expressed in logarithmic
units by a positive or negative
value. When a gain has a negative value in
logarithmic units, attenuation may be
used instead of gain.
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LOSS
1000 Watt
1 Watt
Kabel
Output
Input

• Loss (dB ) 10 Log(power ratio)
• 10 Log(output/input)
• 10 Log ( 1 / 1.000 )
• 10x(-3) -30 dB

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LOSS
1000 Watt
Kabel
Output ?
Input
Loss 10 dB 10 x Power Output Power Input
Loss 1.000 Watt 10 100 Watt Power Output
Power Input - Loss 30 dBW - 10 20 dBW
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GAIN (PENGUATAN)
1 Watt
2 Watt
Amplifier
Output
Input

• Gain (dB ) 10 Log(power ratio)
• 10 Log(output/input)
• 10 Log ( 2 / 1 ) 10 x
  0,3013
• 3,013 dB 3 dB

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GAIN (PENGUATAN)
1 Watt
Amplifier
Output ?
Input
Gain 6 dB 4 x
Power Output Power Input x Gain Power Input 1
Watt 30 dBm Power Output 1 Watt x 4 4
Watt Power Output 30 6 36 dBm
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Model Sistem Komunikasi Listrik
PowerOutput 1 mW 0 dBm
Loss 10 dB
Power Input - 10 dBm
Media Transmisi
Penerima
Pemancar
Wire / Kawat / Kabel Wireless / Radio Fiber Optik
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Model Sistem Pemancar
Power Input 27 dBW
Power Output 1 kW 30 dBW
Gain 10 dB
Antena
Pemancar
Loss 3 dB
Wire / Kawat /Kabel / Kabel Koaxial
Effective Radiated Power (ERP) 37 dBW
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effective radiated power (e.r.p.) (in a given
direction ) The product of the power supplied to
the antenna and its gain relative to a half-wave
dipole in a given direction. Note   The
reference antenna, when fed with a power of 1 kW,
is considered to radiate an e.r.p. of 1 kW in
any direction in the equatorial plane and
produces a field strength of 222 mV/m at 1 km
distance.
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equivalent isotropically radiated power
(e.i.r.p.) The product of the power supplied to
the antenna and the antenna gain in a given
direction relative to an isotropic antenna
(absolute or isotropic gain). Note The
isotropic antenna, when fed with a power of 1 kW,
is considered to provide an e.i.r.p. of 1 kW in
all directions and to produce a field strength
of 173 mV/m at 1 km distance.
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Model Sistem Pemancar Penerima
-32 dBm
Loss 100 dB
ERP 68 dBm
Gain 10 dB
Gain 10 dB
Wireless / Radio
Loss 3 dB
Loss 2 dB
Penerima
Pemancar
Power Input -25 dBm
Power Output 1 kW 60 dBm
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Series Network
G 3 dB
L 5 dB
G 3 dB
N1
N2
N3
T
S
10dBm
11 dBm
13 dBm
8 dBm
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Noise Figure (1)
Spot noise factor, spot noise figure (of a
linear two-port network) Symbol F( f ),
NF The ratio of the exchangeable power spectral
density of the noise appearing at a given
frequency at the output of a given linear
two-port electrical network, to the spectral
density which would be present at the output if
the only source of noise were the thermal noise
due to a one-port electrical network connected
to the input and which is assumed to have at all
frequencies a noise temperature equal to the
reference thermodynamic temperature fixed, by
convention, around 290 K.
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Noise Figure (2)
Noise Figure ( NF ) SNRin - SNRout (dB)
NF 1 ( 0 dB ) ? Noiseless
SNRout
SNRin
Network
40 dB
30 dB
Noise Figure ( NF ) 40 30 10 dB
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Noise Figure (3)
NF NF1 (NF2 1)/G1 (NF3 -1)/G1G2 .
antena
NF23dB Loss3dB
NF316dB G360dB
kabel
Penerima
NF2 3 dB 2 Loss 3 dB 2 G2 0,5
NF3 16 dB 40 G3 60 dB 1.000.000
NF NF2 (NF3-1)/G2 2 (40-1)/0,5 80 19
dB Gain -3 60 57 dB
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Noise Figure (4)
antena
NF23dB Loss3dB
NF316dB G360dB
NF16dB G120dB
kabel
Penerima
preamp
NF1 6 dB 4 G1 20 dB 100 NF2 3 dB
2 Loss 3 dB 2 G2 0,5 NF3 16 dB 40
G3 60 dB 1.000.000
NF 4 (2-1)/100 (40-1)/(100).0,5 4,79
6,8 dB Gain 20 3 60 77 dB
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Noise Figure (5)
antena
NF26dB G220dB
NF316dB G360dB
NF13dB Loss3dB
preamp
Penerima
kabel
NF1 3 dB 2 Loss 3 dB 2 G1 0,5
NF2 6 dB 4 G2 20 dB 100 NF3 16 dB
40 G3 60 dB 1.000.000
NF 2 (4-1)/0,5 (40-1)/(100).0,5 8,78
9,4 dB Gain -3 20 60 77 dB