satellite system parametersstaff.ui.ac.id/system/files/users/ir.muhammad/material/komsat-3.pdf ·...

MUHAMAD ASVIALCenter for Information and Communication Engineering Research (CICER)

Electrical Engineering Department, University of IndonesiaKampus UI Depok, 16424, Indonesia

asvial@ee.ui.ac.idhttp://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