Link Budget (1) Lecture 8

Transcription

1 Link Budget (1) Lecture 8 MUHAMAD ASVIAL Center for Information and Communication Engineering Research (CICER) Electrical Engineering Department, University of Indonesia Kampus UI Depok, 16424, Indonesia asvial@ee.ui.ac.id

2 Link budget & system planning 1

3 Mobile System 2

4 Performance (i) QoS b.e.r if speech data (extra coding) (ii) Availability 95% Channel conditions 3

5 Basic Transmission 4

6 Carrier Transmission Budget -Antenna Gain- The antenna gain is defined as the ratio of the power per unit solid angle received/radiated by the ant enna in a given direction to the power per unit solid angle received/radiated by an isotropic anten na supplied with the same power. 5

7 Basic Transmission 6

8 Basic Transmission 7

9 Antenna radiation pattern Antenna radiation pattern = gain variations as a function of the a ngle relative to boresight 8

10 Transmitted power in a given direction 9

11 Predicted coverage areas for the HOTBIRD satellites (a) Superbeam (b) Widebeam (courtesy of EUTELSAT) 10

12 Effective isotropically radiated power (EIRP) 11

13 Exercise (1) - Carrier Transmission B udget Given Power fed to antenna: P T = 10W Antenna gain (at boresight): G Tmax = 40dB Distance: R = 36000km (earth to geostationary satellite Calculate Transmitter EIRP in db(w) Flux density at receiver in db(w/m 2 ) 12

14 Down Path 13

15 GEO - Geometry 14

16 Earth station from the geostationary orbit Satellite Height h above the equator Sub-satellite point, longitude Φ S Earth station Latitude E, longitude Φ E Relative longitude satellite = (Φ E Φ S ) = ΦE S 15

17 Exercise (2) Carrier Transmission Budget Given Uplink frequency = 14GHz Earth station Power fed to the antenna: P T =100W Antenna diameter: D=4 (efficiency =0.6) Location: Bercenary (France) Latitude = 48º13 07 N Longitude = 03º53 13 E Satellite Receiving antenna gain at boresight: G Rmax =40dB Location: 7ºE (EUTELSAT 1-F2) Calculate EIRP of earth station Free space loss Received power 16

18 Noise in an Earth Station G/T Ref rf if Ta Tf T LNA LNA T IPA IPA T D/L Lo DEMOD BASEBAND QoS (BER) DOWN CONV Ts C/N OD Noise comes from: Ta= picked up by antenna from outside Pa ( =effective noise) kb Tf= lossy feeder T LNA, T IPA = amplifiers in receiver chain T D/C = down converter Refer all noise to a reference plane into the LNA 17

19 Noise in a Payload G/T Ref Cu C D D/C C/Nou eirps Noise comes from: Antenna received noise earth + galaxy Feeder lossy noise (nb. 290K) Equipment noise amps / D/C etc. added in same way as fo r earth station. 18

20 19

21 Noise Characterisation (1) 20

22 Noise Characterisation (2) 21

23 Noise contribution of an attenuator 22

24 Earth-station system G/T and noise temp. Ref LdB Ta Tf T LNA T IPA T D/C LNA IPA D/C T LNA G LNA G IPA T IPA g LNA 1 ( 1 )Tf l T D/C g LNA 1 xta l xg IPA L D/C Ts Ta (1- )Tf T LdB 10log(l),α GdB 10log(g) 1 l LNA T g LNA Gain of antenna at reference (G G (Ga L) 10Log(Ts)dB/K T IPA a g LNA - L)dB T D C x g IPA... 23

25 Earth station antenna noise temperature Examples (clear sky conditions) 24

26 Exercise (3) - Noise Contribution Budget Operating frequency = 12 GHz LNA: T LNA = 150K, G LNA = 50dB MIXER: T MX = 850K, G MX = -10dB IF AMP: T IF = 400K, G IF = 30dB Calculate Receiver effective input noise temperature T R Receiver noise figure 25

27 Exercise (4) - G/T of C-band earth st ation Dish=15m, n=70% Ta=30K Tf=290K Loss f=0.5db T LNA =35K G LNA =30dB F IPA =3dB G IPA =20dB T D/C =1000K Loss D/C=-10dB Feeder Calculate the earth station G/T What are the advantages of trading off dish size and LN A temp.? LNA IPA D/C if 26