Satellite Basics

Types of Satellite

LEO (Low Earth Orbit) 500 to 1000 miles above the earth

MEO (Medium Earth Orbits) 8000 miles above the earth

GEO (Geostationary Earth Orbit) 22,238 miles above the earth

LEO

MEO

GEO

Geostationary Orbit (GEO)

GEOSTATIONARY Earth Orbit

(22238 miles above Earth We utilise the satellites in this orbit Satellite is visible continuously, and appears to

remain in the same place relative to a pointon earth.

Geostationary satellite uses

Broadcast Video Distant Learning Broadcast Audio Data Broadcasting Data/Voice services

Frequencies

Frequencies C-Band

– Transmit 5.925 - 6.425 GHz– Receive 3.700 - 4200 GHz

Ku-Band– Transmit 14.0 - 14.5 GHz– Receive 11.45 - 12.5 GHz

Ka-Band – Transmit 30 GHz– Receive 18 GHz

C Band

C-Band Advantages

– Wide Footprint Coverage– Minor Effect From Rain (Rain Fade)

Disadvantages– Requires Larger Antennas– Requires Larger SSPA– Effected by Terrestrial Interference (TI)

Ku Band

Ku-Band Advantages

– Requires Smaller Antennas– Requires Smaller SSPA

Disadvantages– Effect by Rain (Rain Fade)– Smaller Footprint

Polarisation

Polarization A technique designed to increase the capacity of

the satellite transmission frequency. In linear cross polarization schemes, half of the frequencies beam their signals to earth in vertically polarized mode; the other half horizontal polarize their down links. Although the two sets of frequencies overlap, they are 90 degree out of phase, and will not interfere with each other.

Rain Fade

Rain Fade Loss of signal due to absorption of heavy rain.

Rain Attenuation (dB) at 30deg

Rain Rate (mm/h) 4 GHz 6 GHz 12 GHz 14 GHz5 .1 .15 1.6 1.8

10 .11 .80 2.0 2.915 .12 1.4 2.6 5.020 .13 1.6 3.3 6.825 .14 1.8 4.1 8.030 .15 2.0 5.0 9.235 .16 2.4 6.0 10.440 .17 2.8 7.0 11.8

Typical Satellite footprints -

Intelsat 706 @ 307° East

EIRP (Effective Isotropic Radiated Power) - The strength of the signal leaving the satellite antenna

Maps are also available with G/T (Gain-to-Noise) data.

Satellite Transponder

Transponder Block of frequency on a satellite.Typical bandwidth is

40MHz per transponder (36MHz usable - 2 MHz of guard band on each side). Some Ku-Band transponder are 54MHz & 72MHz.

Rx (MHz) 3720 3760 3800 3840 3880 3920 3960 4000 4040 4080 4120 4160Tran. 1 3 5 7 9 11 13 15 17 19 21 23

V

Tx (MHz) 5945 5985 6025 6065 6105 6145 6185 6225 6265 6305 6345 6385Tran. 1 3 5 7 9 11 13 15 17 19 21 23

H

Rx (MHz) 3740 3780 3820 3860 3900 3940 3980 4020 4060 4100 4140 4180Tran. 2 4 6 8 10 12 14 16 18 20 22 24

H

Tx (MHz) 5965 6005 6045 6085 6125 6165 6205 6245 6285 6325 6365 6405Tran. 2 4 6 8 10 12 14 16 18 20 22 24

V

SCPC Earth Station

Satellite Modem

Antenna

IFL 70M Hz Tx

IFL 70M Hz Rx

LNA

OM T w/Reject FilterFeed Horn

Heliax4GHz

W aveguide6GHz

RFT

OffsetTx/Rx

Antenna

FRAD

RS422 or V.35

6GHz

4G Hz

SatelliteTypical C-Band SCPC

(Single-Channel-Per-Carrier)Earth Station Components

Also called VSAT (Very Small Aperture Terminal)

Delay -Sun outages

Transmission Delay Delay is 250ms from Site A to the

Satellite to Site B, due to the distance of 22,238 miles.

Sun Outage Sun passes behind a satellite in

relation to the earth, and the sun’s energy briefly interferes with the satellite signals. Happens two times each year.

125ms125ms

Earth Station Components

Feedhorn A component that collects

the signal from the antenna and channels it to the OMT

OMT/Reject Filter Orthogonal-Mode

Transducer. Performs Polarization of Tx/Rx


LNA (Low Noise Amplifier) Preamplifier of the receive signal. Rated in

Noise temp (K). Heliax

Low loss foam-dielectric cable. Typical loss of 1/2” Heliax at 4GHz is .4dB per 10ft.

Flexible Waveguide A metallic microwave conductor, typically

rectangular in shape, used to carry high frequency microwave signal.Typical loss at 6GHz is .15dB per 10ft.


RF Transceiver Consist of an Upconverter, Downconverter,

and SSPA(Solid State Power Amplifier) Other Names

– ODU - Outdoor Unit– RF


RFT (Radio Frequency Terminal) cont. Upconveter/Downconverter

IF (Intermediate Frequency) Coax Cable, typically RG8 50. 70 or 140 MHz

IFL 70MHZ Rx(±18MHz in 5KHz Steps)

RFT C-Band

Upconverter

Downconverter

SSPA 5W

IFL 70MHZ Tx(±18MHz in 5KHz Steps)

Step 1- 3980MHz to 1250MHzStep 2 - 1250MHz to 70MHz

Step 1- 70MHz to 1250MHzStep 2 - 1250MHz to 6205MHz

Earth Station Components- Modem

Satellite Modem (MOdulator, DEModulator)

Provides interface between multiplex unit and RF Transceiver.

Modulates transmit signals from mux,thereby providing 70 Mhz output to RF.

Demodulates received 70 Mhz signals from RF and converts into format suitable for multiplex unit.

Earth Station Components- Modem

Forward Error Correction (FEC) - Viterbi– Adds unique codes to the digital signal

at the source so errors can be detected and corrected at the receiver. – 1/2 rate = 1bit data, 1bit error correction– 3/4 rate = 3bit data, 1bit error correction– 7/8 rate = 7bit data, 1bit error correction

Transmission method Channel Spacing Eb/No @ 10E-07

256Kbps, QPSK, rate 1/2 360 kHz 6.5




128Kbps, BPSK, rate 1/2 360 kHz 6.5






Eb/No - Bit Energy-to-NoiseRatio.

Frequency Configuration

Satellite Modem

IFL 70.25 MHZ Rx(±18MHz in 5KHz Steps)

RFT C-Band

Satellite

6205 MHz(1 MHz Steps)

3980 MHz(1 MHz Steps)

Upconverter

Downconverter

SSPA 5W

Antenna

LNA

OMT w/Reject FilterFeed Horn

6205.25 Mhz3980.25 MHz

L.O 2225MHz

IFL 70.25 MHZ Tx(±18MHz in 5KHz Steps)

Required FrequenciesTx - 6205.25 MHzRx - 3980.25 MHz

LNB

LNB (Low Noise Block Downconverter) A combination Low Noise Amplifier and downconverter

built into one device attached to the feed. PLL LNB (Phase-Locked Loop Low Noise Block Downconverter)

A combination Low Noise Amplifier and stable downconverter built into one device attached to the feed.

SCPC L-Band Earth Station

Antenna

IFL 950-1450 M Hz Tx

IFL 950-1450M Hz Rx

PLLLNB

OM T w/Reject F ilterFeed Horn

BUC

OffsetTx/Rx

Antenna

FRAD

RS422 or V.35

6GHz

4GHz

Satellite

SL512 L-BandSatellite M odem

SL512

L Band Earth Station Components

BUC (Block Upconverter) Input of 950-1450 and Upconverter the 500MHz to

C-Band or Ku-Band PLL LNB (Phase-Locked Loop Low Noise Block

Downconverter) A combination Low Noise Amplifier and stable

downconverter built into one device attached to the feed.

L Band Earth Station Components

Cable Rx RG6 75, Tx LMR-600-DB 50

L-Band Modem Tx/Rx 950-1450MHz 10MHz Ref to BUC DC Power to BUC 19.2kbps - 512kbps

L Band Earth Station Advantages

Advantage Lower Cost RFT (BUC & PLL LNB) Utilizes off-the-shelf PLL LNB’s Powers most BUC Tunable over the whole satellite spectrum

500MHz

L Band Earth Station Disadvantages

Disadvantages Cable length - max 300ft. DC power on the Tx side may damage test

equipment. Need to use a DC Block or turn off DC Power on the modem.

May Require an Uplink Power Control cable.

Education

Satellite Basics