Download - Satellite Presi
-
8/22/2019 Satellite Presi
1/34
Project of
Satellite Communication for the Martian Colonies
Sanaz Roshanmanaesh Mohammad shabash Mohammad Abbas
Zein Jaber Mahyar Alzobaidy Caglar Sekman
March 2011
Satellite & Cellular Radio
Supervisors:
Dr. Peter GardnerDr. Costas Constantinou
-
8/22/2019 Satellite Presi
2/34
Satellite constellation
2 orbits each consist of 6 satellites MMOAstra 2C taken as a model for the spacecraft
Orbit altitude of 5000 Kilometres
-
8/22/2019 Satellite Presi
3/34
Satellite constellation
A combination of 20 beams in each satellite
3dB beamwidth of 5 degrees per beamOne complete orbit in 6.49 hours
Each satellite covers area of approximately
15.2 Million square Km
-
8/22/2019 Satellite Presi
4/34
Outline
Introduction
Satellite Transponder
* HTS BPF
* Antenna* LNA & HPA
Ground station outline design
* BPF
* Antenna
* LNA & HPA
* Duplexer
Satellite & RF Radio
4
-
8/22/2019 Satellite Presi
5/34
Introduction
Frequencies:
* Beacon Frequency:5000MHz
Satellite & RF Radio
5
Uplink Ground Station-Satellite
5500 ~ 6000 MHz
Downlink Satellite- Ground
Station 4000 ~ 4500 MHz
-
8/22/2019 Satellite Presi
6/34
Satellite Transponder
A receiver-transmitter that will generate a reply signalupon proper electronic interrogation
Total block diagram of designed satellite transponder
Satellite & RF Radio
6
LNA6 GHz Amp1
Frequency
DMUX
Frequency
MUX
HPAD/CEqualiser
6 GHz 4 GHz
4GHz
HTS
BPF
BPFAmp2
-
8/22/2019 Satellite Presi
7/34
Antenna of Transponder
Reflector Antenna
Two separated
antenna
Circular polarization
Satellite & RF Radio
7
-
8/22/2019 Satellite Presi
8/34
Antenna of Transponder
Rx Antenna (6GHz)
* Diameter 0.8m. Aperture Efficiency 0.7, radiation
efficiency 0.9. Physical temperature 50 K.
* Gain 33dBi, Beam Width : 3.5 degree
Tx Antenna (4GHz)
* Diameter 0.9m. Aperture Efficiency 0.7, radiation
efficiency 0.9. Physical temperature 50 K.
* Gain 30dBi, Beam Width : 5 degree
Satellite & RF Radio
8
-
8/22/2019 Satellite Presi
9/34
HTS filter
Expensive but economical
because of Two important
properties:
* Low Insertion Loss* Small size and weight
Low temperature in out of
Mars atmospher
Lead to small noise figure
in receiver
Insertion Loss=0.5 dB
Satellite & RF Radio
9
-
8/22/2019 Satellite Presi
10/34
LNA & HPA of Transponder
LNA
* Noise figure=1.5dB
* Gain=20dB
* Amp1 (NF=3dB, Gain=40 dB)* Total NF of receiver=2.0135
HPA
* 10 Watt, SSPA (Solid State Power Amplifier)
* Saturated output power 13dBW=43dBm 3dB back-off
* Gain 30 dB & Efficiency: 38%
* GaN HFETs TechnologySatellite & RF Radio
10
-
8/22/2019 Satellite Presi
11/34
Outline of Ground Stations
Transceiver Configuration (Using one antenna)
* Utilizing Waveguide Duplexer
Insertion Loss @ 4GHz: 1dB
Insertion Loss @ 6GHz: 1.2dB
BPF
* Waveguide filters
Insertion loss=1dB
Amp1: Gain: 40dBAmp1: Gain: 30dB
Satellite & RF Radio
11
Duplexer
IFProcessing
LNA D/C
HPA U/CBPF
Ant.BPF
4 GHz
6 GHz
Amp1
Amp2
-
8/22/2019 Satellite Presi
12/34
Antenna of Ground Station
Using a common antenna for transmitting & receiving
* since the ratio of the U/L to the D/L frequencies is no more
than 1.5
* Reflector Antenna, Helical feed, Circular polarization
* Diameter 2m. Aperture Efficiency 0.7, radiation efficiency
0.9. Physical temperature 50 K
Rx Mode (4GHz)
* Gain 37dBi, Beam Width : 2.5 degreeTx Mode (6GHz)
* Gain 40dBi, Beam Width : 1.8 degree
Satellite & RF Radio
12
-
8/22/2019 Satellite Presi
13/34
LNA & HPA of Ground Station
LNA
* Noise figure=1.5dB
* Gain=20dB
* Amp1 (NF=3dB, Gain=40 dB)
* Total NF of receiver=2.5135
HPA
* 100 Watt, TWTA (Travelling Wave Tube Amplifier)
* Saturated output power 23dBW=53dBm 3dB back-off
* Gain 40 dB
Satellite & RF Radio
13
-
8/22/2019 Satellite Presi
14/34
Down/Up Converter
* Conversion Loss of Mixer: 4dB
* Insertion Loss of filter: 2dB
* Total Loss of Converter: 6dB
* Noise temperature: 3000K* A synthesizer with suitable frequency steps should be used as
a local oscillator
* DMUX and Equaliser loss: 12 dB (Physical temp. 50 K)
Satellite & RF Radio
14
Local
Oscillator
BPF4000~4500
MHz
5500~6000
MHz5500~6000
MHz
Local
Oscillator
4000~4500
MHz
BPF
-
8/22/2019 Satellite Presi
15/34
Link Budget Calculation
Noise at receiver
Antenna noise (Tant)
Active device noise
Thermal noiseReceiver figure of merit
M= Gr/Ts (dB/K)
09/08/2013 15
Receiver
Power
EIRP calculation
Gain and losses calculation
i
-
8/22/2019 Satellite Presi
16/34
Link budget Losses
Atmospheric attenuation will be neglected because Mars is dominated by C
O2 and N2. It is found that the attenuation values due to oxygen at Mars are reduced by a factor of 14,000 relative to Earth, Such a small attenuation is
negligible for telecommunications.
This table provide to us the Attenuation around mars for various frequency
-
8/22/2019 Satellite Presi
17/34
Link budget
Since we know that the power at the receiver is defined by the following equation
S(dBW) =Pt (dBW) +Gt(dB) +Gr(dB)Lp (dB)Lat(dB)
We need first to determine the transmitter power
Carrier to noise spectral density ratio is defined by these equations
C/N0 (dBHz) =Eb/N0+ 10log10(B) (2)
=Pt +GtLt+ 10log10(Gr/Ts)10log10(k) (3)
Where
Pt transmited power , Gt antenna transmited gain
Lt is the total losses
K is boltzman losses
(Gr/Ts) is the figure of merit
Eb/N
0is the energy per noise density for modulation
B is the bit rate.
Since we know the modulation sachem and the bit rate, we can calcuate C/N0
For a QPSK modulation and BER 10-3 of ,Eb/N0 = 21dB , where B =45Gb/s. Substituting these values in Eq (2)
C/N0
= 21 + 101og10
45G = 127.53 (dBHz)
Li k b d
-
8/22/2019 Satellite Presi
18/34
Link budget
In order to calculate (Gr/Ts) , we need to evaluate the noise system temperature Ts.we simplified the receiver architecture as shown below
Where
L= 0.5 dB , l= 1.122. FGLA=1.5 dB, fgla= 1.413. GLA= 20 dB FGA= 3dB, fGA= 2. GA= 30 dB
TF = 210 (1.122-1)=25.62K. TLA=210(1.413-1)=86.73. TAmp=210(2-1)=210.
TA= 50 K.
Ts= TA + TF + TLA/ (1/L) + TAmp/ (GLA * (1/L)) + ...........
Ts = 50 + 25.2 + 96.432 + 2.36 = 173.992 K
The results confirms that the major contributors to the system noise temperature are the first two de
vices comparing the front end area of the satellite receiver.
+ 1/L + GLA + GA
TLA TAmpTF
TA
Li k b d
-
8/22/2019 Satellite Presi
19/34
Link budget
10log10(Gr/Ts) = 10log10 (3162.278/173.992 ) = 12.6 dB/K
Pt = C/N0 - Gt + Lt- 10log10(Gr/Ts)10log10(k)
Where
Lt = Lp + LatLp = 20 log (4d/) = 176 dB ,Lat= 0.45 dB
Pt= 127.5345 + 176.512.6228.6
Pt = 17.83dB , 61 watt
N(dBW) = 10log10k(dBW/Hz/K) + 10 log10 (Tant+ Te) (dBK) + 10log10B (dBHz)
N = -228.6 + 22.4 + 87
N = - 119.2 dBw
-
8/22/2019 Satellite Presi
20/34
Link budget
up link down link Unit
Pt tx power 17.83 27 dBW
Gt tx ant gain 45 37 dB
L p free space loss -176 -178.5 dBL a atmosph loss -0.45 -0.45 dB
Gr rx ant gain 35 40 dB
Prrx power -78.62 -74.96 dBW
Tnoise temp 173.992 460.7 K
Bbandwidth 500 500 MHz
Nnoise power - 119.2 dBw -114.9 dBW
S/Nat rx 40.58 39.9 dB
20
note up and down link values different due to different frequencies
4/6 GHz link; satellite antenna = 1m earth antenna = 3m
-
8/22/2019 Satellite Presi
21/34
Multiple Access Techniques
- Able to provide fixedtraffic patterns
- Unable to perform verywell for the future broadband
satellite communicationservices.
SDMA
FDMA
TDMA
CDMA
OFDM
High spectralefficiency & Low
PAPR
Robust against intersymbol interference
(ISI) and fading
Useful in Broadband& Mobile Satellite
Comm.
Complex
receivers,
Need power
Inflexibility
Inflexible, antennas fixed
Guard space needed (multipath
propagation), synchronization difficult
-
8/22/2019 Satellite Presi
22/34
Power Efficiency or Spectral Efficiency ?
Spectral/Bandwidth Efficiency
is not important
No Bandwidth
restrictions
QPSK (modulation technique)
No need for 16-QAM ( less powerefficient )
Importance:
High powerefficiency &Low PAPR
-
8/22/2019 Satellite Presi
23/34
Block diagram of OFDM system
The main drawback of OFDMA scheme: High PAPRLow Power Efficiency.
-
8/22/2019 Satellite Presi
24/34
Block diagram of SC-FDMA/DFT-S OFDM Syste
m
DFT- spreading block between the S/P & IFFT blocks
Low PAPR High power efficiency
-
8/22/2019 Satellite Presi
25/34
-
8/22/2019 Satellite Presi
26/34
Same scheme by both downlink and uplinkComplexity & Cost of terminals equipment will be Reduced.
Uplink: Increasing Pt compensate for the fading
Downlink: Difficult to compensate for the fading by high power.
Solution: Employing the efficient coding scheme
The link scheme based on the OFDM/TDM technique
frequency & power more efficient
Challenges
-
8/22/2019 Satellite Presi
27/34
Satellite Electrical Power System
EnergyStorageSystem
PDCU
PayloadSolarArray
A Satellite has to produce its own power!! Power Requirements of subsystem on board.
-
8/22/2019 Satellite Presi
28/34
Primary Source
Solar Panels* Gallium Arsenide 3-junction solar cells .
* 2 Solar panels.
* Efficiency up to 26 % of the sun energy.
* Each panel measures 5.35 2.53m
* 3744 individual photovoltaic cells.
* Power produced at 32 v.
* Power produced is 7000watts
-
8/22/2019 Satellite Presi
29/34
Primary Source
-
8/22/2019 Satellite Presi
30/34
Secondary Source
Lithium Ion Cells (Batteries)
Higher energy density than the Nickel-based batteries.
Operating voltage is 3.6 to 3.9 v which reduces the
number of cells.
65% volume advantage and 50% mass advantage.
150 Kg should be considered.
A regulator system that bleeds off the excess power
as heat will be used.
Used for the night hours (12 per martian day)
-
8/22/2019 Satellite Presi
31/34
Performance and Future
Factors with adverse impact:
variation in Mars-Sun distance
Atmos. Scattering and accumulation of mars dust on arrays.
dust accumulation will decrease solar cell performance by 77% after only 2 years.
Approaches:
Array vibrating technique for dust removal.
Use RTG or fuel cells as secondary power sources during eclipses.
RTG provide more power for less mass but they are much more expensive.
-
8/22/2019 Satellite Presi
32/34
Communications Gateway
Building a publicly accessible gateway on Mars.
Gateways should be positioned in deep space so th
at information can be passed back and forth.Robust redundancy is required for gateways to ens
ure reliable, long term operations.
Orbital dynamics could be a problem in the name
of position of gateways at solar LaGrange points
-
8/22/2019 Satellite Presi
33/34
Communications Gateway
A proposed system called Interplanetary Internet (IPN) can be used for deep space communication and linked to Earth by satellites.
There will be a network between two internets wit
h a local gateway.Data rate of minimum 1 Mbps would be enough fo
r real time data transfer.
Parcel Transfer Protocol (PTP) can be also used ifnecessary.
TCP/IP protocol can be used on both planet.
-
8/22/2019 Satellite Presi
34/34
Technical Challenges
Interactive protocols do not work as the distance is
long.
Latency or delay may occur.Antennas weight should be small.
Low bandwidth.