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MUHAMAD ASVIALCenter for Information and Communication Engineering Research (CICER)
Electrical Engineering Department, University of IndonesiaKampus UI Depok, 16424, Indonesia
[email protected]://www.ee.ui.ac.id/cicer
Satellite System Parameters
Lecture 3
1
– Satellite System Parameters• Transmit Power and Bit Energy
• Effective Isotropic Radiated Power
• Equivalent Noise Temperature
• Carrier-to-Noise Density Ratio
• Bit Energy to Noise Density Ratio
• G/Te Ratio
• Illumination Level and Power Flux Density
• C/Ts Ratio
Objectives
2
Figure Satellite mobile communications system configuration
Satellite System
3
Noise in Earth Station
– Noise comes from:• Ta= picked up by antenna from outside ( =effective noise)• Tf= lossy feeder• TLNA, TIPA= amplifiers in receiver chain• TD/C= down converter
– Refer all noise to a reference plane into the LNA
kBPa
DEMODBASEBAND
QoS(BER)
LNA IPA
rf if
G/T Ref
Lo
DOWN CONVC/NOD
Ta Tf
Ts
TLNA TIPA
TD/LDEMOD
BASEBANDQoS
(BER)LNA IPA
rf if
G/T Ref
Lo
DOWN CONVC/NOD
TaTa TfTf
TsTs
TLNATLNA TIPATIPA
TD/LTD/L
4
Noise in Payload
G/T Ref
Cu
D/C
C/N
• Noise comes from:– Antenna received noise –earth + galaxy– Feeder lossy noise (nb.290K)– Equipment noise –amps / D/C etc. added in same way as for earth
station.
CD
eirps
5
6
Noise Characterization
7
Noise Characterization
8
Noise contribution of an attenuator
9
– Thermal Noise Sources
– Thermal Noise Power
Noise
10
– Noise Measurements in a Receiver
Figure Noise Ratios at Receiver
Noise
11
– Transmitter Power and Bit Energy• Eb = Pt x Tb or Pt / fb where Pt is Tx Power in Watts or Jo
ules per Sec, Tb is Bit duration in Sec, fb is bps and
Eb is Bit Energy in Joules per Sec
Figure HPA input/output characteristic curve
Transmitter Power and Bit Energy
12
– Effective Isotropic Radiated Power (EIRP)• EIRP = PT x GT/ LT where GT is Tx Antenna Gain and LT is trans
mission line losses including back-off loss, feeder loss, and branching loss etc.
• EIRP (dBW) = Pt(dB) – Lbo(dB)- Lbf (dB)+ GT(dB)
Where
PT = actual power output of the transmitter (dBW)
Lbo = back-off losses of HPA (dB)
Lbf = total branching and feeder loss (dB)
GT = transmit antenna gain (dB)
EIRP
13
– Equivalent Noise Temperature
• N = KTB where K (1.39 x 10-23 joules per Kelvin) is Boltzmann’s constant, T (degree Kelvin) is environment temperature, and B (Hz) is System BW
• F = 1+Te/T where F (unitless) is noise factor and Te is Equivalent Noise Temperature (degree Kelvin)
• Te = T (F-1)
Example 5-3: Convert noise figures 4 and 4.01 to equivalent temperatures. Use 300 K for the environmental temperature.
Solution 5-3:
Te = T(F-1)
For F = 4 Te = 300(4-1) = 900 K
For F = 4.01 Te = 300 (4.01 –1) = 903 K
– Noise Density No = N/B or No = KTeB/B = KTe
Equivalent Noise Temperature
14
– Carrier to Noise Density Ratio C/No = C/KTe
– Eb/No = Pt/fb x B/N or C/N x B/fb where fb is bit rate R
(bits per sec) and Pt is replaced with C
This Eb/No is a very good measure to compare digital systems
employing different modulation or encoding schemes and data
ratesExample 5-5: Comparison of Two Digital Systems:Compare the performance characteristics of the two digital systems listed below, and determine which system has the lower probability of error.
QPSK 8PSK
Bit rate 40 Mbps 60 MbpsBandwidth 1.5 X minimum 2 X minimumC/N 10.75 dB 13.76 dB
Carrier to Noise Density Ratio
15
– Gain to Equivalent Noise Temperature Ratio G/Te:G/Te = G-10 log (Ts) = G- 10 log (Ta +Tr) where Ts is equivalent system noise temperature. Ta is antenna noise temp. and Tr is receiver effective noise temp.
As LNA is placed so closed (at feed point) to antenna, so, G/Te is changed as under:
G/Te = [Gr +GLNA]/Te
Expressed in log,
G/Te (dBK-1) = Gr (dB) + GLNA (dB) – Te (dBK-1)
G/Te
16
– Illumination Level
– Power Flux Density (PFD)- EIRP/4πd2
W = EIRP – L + G* (dBW/m2)Or, W = EIRP –20 log10 S –71 (dBW/m2)
Where S= Link distance in km
* Gain of a theoretical antenna w
ith one m2area…
D=1.13m
Figure 3.7.2-3 Illumination level for geostationary satellite
Illumination Level
17
Carrier-to-Thermal Noise Ratio-C/Ts
C/TS = EIRP – L – LADD + GR/TS
Where EIRP: Equivalent isotropic power of transmitter (dBW)
L: Path loss (dB)
LADD: Additional transmission losses (dB)
GR/TS: Receiving system figure of merit (dBi/K)
C/TS = w+ GR/TS – G1m2
C/Ts
18
– BER (Pe) Vs C/N and Eb/No
BER
19