Modul – 3 Sistem Transmisi TE-09-1313 2 sks Tim Bidang Studi Telekomunikasi Multimedia (Achmad Ansori, Devy Kuswidiastuti, Gatot Kusrahardjo, M Aries Purnomo) TE-09-1313-03-Transmisi-2 1 The use of the decibel and of relative levels in speechband telecommunications TE-09-1313-03-Transmisi-2 2 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". TE-09-1313-03-Transmisi-2 3 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 This unit is not often used, having been replaced by the decibel (symbol dB) which is one-tenth of a bel. TE-09-1313-03-Transmisi-2 4 Bel • Unit dari ukuran perubahan daya • Bel = Log (P1/P2) • P1 dan P2 dalam satuan yang sama ( Watt, mWat, kWatt ) TE-09-1313-03-Transmisi-2 5 Daya, Tegangan dan Arus • Daya = Tegangan x Arus • Satuan : Daya : Watt , Tegangan : Volt , Arus : Ampere (Amp) • P=VxI • V=IxR dimana R : tahanan, Ohm () TE-09-1313-03-Transmisi-2 6 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 TE-09-1313-03-Transmisi-2 7 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 TE-09-1313-03-Transmisi-2 8 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(V1R2)/V2R1) , jika R1 R2 TE-09-1313-03-Transmisi-2 9 Ringkasan (2) • Bel = 2 Log I1/I2 , jika R1 = R2 • Bel = 2 Log I1/I2 + Log R1/R2 , jika R1 R2 • Bel = 2 Log (I1R1)/(I2R2) , jika R1 R2 TE-09-1313-03-Transmisi-2 10 DECIBEL (1) • Unit yang menyatakan ratio • Bentuk logaritma dengan dasar 10 • Decibel ( dB ) = 10 Log ( power ratio ) TE-09-1313-03-Transmisi-2 11 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 TE-09-1313-03-Transmisi-2 12 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 (V1R2)/(V2R1) dB = 20 Log (I1R1)/(I2R2) TE-09-1313-03-Transmisi-2 13 Power Ratio & Voltage Ratio (1) dB 0 1 2 3 4 5 6 7 8 9 10 20 30 40 Gain Power Ratio Voltage Ratio 1.00 1.26 1.58 2.00 2.51 3.16 3.98 5.01 6.31 7.94 10.00 100.00 1000.00 10000.00 TE-09-1313-03-Transmisi-2 1.00 1.12 1.26 1.41 1.58 1.78 2.00 2.24 2.51 2.82 3.16 10.00 31.62 100.00 14 Power Ratio & Voltage Ratio (2) dB 0 1 2 3 4 5 6 7 8 9 10 20 30 40 Loss Power Ratio Voltage Ratio 1.0000 0.7943 0.6310 0.5012 0.3981 0.3162 0.2512 0.1995 0.1585 0.1259 0.1000 0.0100 0.0010 0.0001 TE-09-1313-03-Transmisi-2 1.0000 0.8913 0.7943 0.7079 0.6310 0.5623 0.5012 0.4467 0.3981 0.3548 0.3162 0.1000 0.0316 0.0100 15 Power Ratio & Voltage Ratio (3) dB Ratio Power Voltage 1 2 4 8 10 16 32 64 100 128 256 512 1000 0.00 3.01 6.02 9.03 10.00 12.04 15.05 18.06 20.00 21.07 24.08 27.09 30.00 0.00 6.02 12.04 18.06 20.00 24.08 30.10 36.12 40.00 42.14 48.16 54.19 60.00 TE-09-1313-03-Transmisi-2 16 TE-09-1313-03-Transmisi-2 17 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 TE-09-1313-03-Transmisi-2 18 dBm, dBW, Watt & milliWatt TE-09-1313-03-Transmisi-2 19 Voltage & Current Ratio • dB(Voltage) = 20 Log ( ratio voltage ) • dB(Current) = 20 Log ( ratio current ) TE-09-1313-03-Transmisi-2 20 dBmV • Digunakan pada transmisi video • Tegangan ( Voltage ) referensi = 1 mVolt pada beban 75 Ohm • dBmV = 20 Log ( tegangan/1 mVolt ) TE-09-1313-03-Transmisi-2 21 dBmV TE-09-1313-03-Transmisi-2 22 dBµV/m • Pengukuran kuat medan listrik • Referensi 1µV/m dBµV/m = 20 Log (µV/m) TE-09-1313-03-Transmisi-2 23 KONSEP SISTEM TRANSMISI Loss & Gain TE-09-1313-03-Transmisi-2 24 attenuation, loss : 1. 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. TE-09-1313-03-Transmisi-2 25 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. TE-09-1313-03-Transmisi-2 26 LOSS 1000 Watt 1 Watt Kabel Input Output • Loss (dB ) = 10 Log(power ratio) = = 10 Log(output/input) = = 10 Log ( 1 / 1.000 ) = = 10x(-3) = -30 dB TE-09-1313-03-Transmisi-2 27 LOSS 1000 Watt Kabel Input Output = ? 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 TE-09-1313-03-Transmisi-2 28 GAIN (PENGUATAN) 1 Watt 2 Watt Amplifier Input Output • Gain (dB ) = 10 Log(power ratio) = = 10 Log(output/input) = = 10 Log ( 2 / 1 ) = 10 x 0,3013 = 3,013 dB = 3 dB TE-09-1313-03-Transmisi-2 29 GAIN (PENGUATAN) 1 Watt Amplifier Input Output =? 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 TE-09-1313-03-Transmisi-2 30 Model Sistem Komunikasi Listrik PowerOutput : 1 mW = 0 dBm Pemancar Loss 10 dB Power Input : - 10 dBm Media Transmisi Penerima Wire / Kawat / Kabel Wireless / Radio Fiber Optik TE-09-1313-03-Transmisi-2 31 Model Sistem Pemancar Power Output 1 kW = 30 dBW Power Input 27 dBW Gain = 10 dB Loss = 3 dB Antena Pemancar Wire / Kawat /Kabel / Kabel Koaxial TE-09-1313-03-Transmisi-2 Effective Radiated Power (ERP) : 37 dBW 32 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. TE-09-1313-03-Transmisi-2 33 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. TE-09-1313-03-Transmisi-2 34 Model Sistem Pemancar & Penerima ERP : 68 dBm -32 dBm Loss = 100 dB Gain 10 dB Wireless / Radio Loss = 3 dB Loss = 2 dB Pemancar Gain 10 dB Power Input = -25 dBm Penerima Power Output 1 kW = 60 dBm TE-09-1313-03-Transmisi-2 35 Series Network S G 3 dB L 5 dB G 3 dB N1 N2 N3 T 10dBm 13 dBm 8 dBm TE-09-1313-03-Transmisi-2 11 dBm 36 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. TE-09-1313-03-Transmisi-2 37 Noise Figure (2) Noise Figure ( NF ) = SNRin - SNRout (dB) NF = 1 ( 0 dB ) Noiseless SNRin Network 40 dB SNRout 30 dB Noise Figure ( NF ) = 40 – 30 = 10 dB TE-09-1313-03-Transmisi-2 38 Noise Figure (3) NF = NF1 + (NF2 – 1)/G1 + (NF3 -1)/G1G2 + …. antena NF2=3dB Loss=3dB kabel NF3=16dB G3=60dB 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 TE-09-1313-03-Transmisi-2 39 Noise Figure (4) antena NF1=6dB G1=20dB NF2=3dB Loss=3dB NF3=16dB G3=60dB preamp kabel Penerima 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 TE-09-1313-03-Transmisi-2 40 Noise Figure (5) antena NF1=3dB Loss=3dB kabel NF2=6dB G2=20dB preamp NF3=16dB G3=60dB Penerima 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 TE-09-1313-03-Transmisi-2 41