satellite presi

8/22/2019 Satellite Presi

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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


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Satellite constellation

2 orbits each consist of 6 satellites MMOAstra 2C taken as a model for the spacecraft

Orbit altitude of 5000 Kilometres


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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


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Outline

Introduction

Satellite Transponder

* HTS BPF

* Antenna* LNA & HPA

Ground station outline design

* BPF

* Antenna

* LNA & HPA

* Duplexer

Satellite & RF Radio

4


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Introduction

Frequencies:

* Beacon Frequency:5000MHz


5

Uplink Ground Station-Satellite

5500 ~ 6000 MHz

Downlink Satellite- Ground

Station 4000 ~ 4500 MHz


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Satellite Transponder

A receiver-transmitter that will generate a reply signalupon proper electronic interrogation

Total block diagram of designed satellite transponder


6

LNA6 GHz Amp1

Frequency

DMUX

Frequency

MUX

HPAD/CEqualiser

6 GHz 4 GHz

4GHz

HTS

BPF

BPFAmp2


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Antenna of Transponder

Reflector Antenna

Two separated

antenna

Circular polarization


7


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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


8


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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


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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


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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


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Duplexer

IFProcessing

LNA D/C

HPA U/CBPF

Ant.BPF

4 GHz

6 GHz

Amp1

Amp2


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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


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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


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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)


14

Local

Oscillator

BPF4000~4500

MHz

5500~6000

MHz5500~6000

MHz

Local

Oscillator

4000~4500

MHz

BPF


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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


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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


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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


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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


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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


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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

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note up and down link values different due to different frequencies

4/6 GHz link; satellite antenna = 1m earth antenna = 3m


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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


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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


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Block diagram of OFDM system

The main drawback of OFDMA scheme: High PAPRLow Power Efficiency.


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Block diagram of SC-FDMA/DFT-S OFDM Syste

m

DFT- spreading block between the S/P & IFFT blocks

Low PAPR High power efficiency


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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


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Satellite Electrical Power System

EnergyStorageSystem

PDCU

PayloadSolarArray

A Satellite has to produce its own power!! Power Requirements of subsystem on board.


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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


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Primary Source


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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)


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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.


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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


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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.


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Technical Challenges

Interactive protocols do not work as the distance is

long.

Latency or delay may occur.Antennas weight should be small.

Low bandwidth.

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