for quiz Flashcards
object in space that orbits or circles around a larger object
satellite
is an object that has been intentionally placed into orbit that relays and amplifies radio telecommunications signals
artificial satellite
Applications Satellite
Voice/Telephone
Television/Radio Broadcast
Network/Internet
Navigation and GPS
scientific research
Meteorology
The path of a celestial body or an artificial satellite that revolves around another body
Orbit
Orbit common classification:
Low Earth Orbit (LEO)
Middle Earth Orbit (MEO)
Geostationary Orbit (GEO)
Geosynchronous Orbit (GSO)
High Earth Orbit (HEO)
technique used to improve the signal-to-noise ratio of received signals,eliminate undesirable interference sources and focus transmitted signals to specific locations
Beanforming
Advantages of Satellite
*Cost is independent of the distance between earth stations
*Cost advantage over building land lines for remote locations
*Cost effective for short term requirements Mobility
*Adaptable and versatile for multiple applications (Voice, Video, Data)
Disadvantages
*High cost of equipment
*Limited frequency spectrum
SC
* Electromagnetic Interference (EMI) (power lines, terrestrial communications)
*Susceptible to some environmental conditions (rain, snow, solar outages)
One-way Communication
Broadcast, Multicast
Examples of One way communication
Examples: Broadcasting satellite services like Radio, TV, GPS, Weather Monitoring
Two-way Communication
Point-to-point
Example two way communication
Examples: tracking telemetry and control (TT&C) system, Internet services.
Converts information into an analogue Receives Signal and transmits it to the satellite , Amplifies Down converts
Retransmit
Uplink Earth Station
Receives the signal and recovers the Loss Loss Original information
down-link earth stations
Parabolic Antenna
Parabolic Antenna
* Uses the parabolic geometry to create a highly directional beam
*The point of source is placed at the focus of the parabola to direct radio waves In a narrow beam or receive signals from a particular direction
* The reflector is made of a material that reflects radio waves
Satellite Components
*Consists of multiple subsystems that allow It to operate and to provide services throughout Its expected lifetime
*Transponders are segments of the nsatellite bandwidth
* Transponders receive, amplify, filter convert and rebroadcast a signal
a device that is intended to convert an analog signal between a lower frequency and a higher frequency
Up and Down Converter and mixer
electromagnetic radiation that consist of synchronized oscillations of electric and magnetic fields. measured bt its frequency or wavelength
electromagnetic wave
property in which the directiin and magnitude of the electromagnetic wave is propagated in a specific way
Polarization
types of polarization
Linear, Circular and Elliptical
types of linear polarization
horizontal and Vertical polarization
Circular and Elliptical
Left and Right Polarization
Frequency Bands
C band (4-8 GHz)
X band (8-12 GHz)
Ku Band (12-18 GHz)
Ka Band (26-40 GHz)
Ka Band
27-40 GHz, 1.1-0.2 cm Rarely used for SAR (Airport Surveillance)
K band
18-27 GHz, 1.7-1.1 cm, H20 absorption
Ku band
12-18GHz, 2.4-1.7 cm satellitr altimetry
types of earth stations
fixed, portable and Satellite on the Move (SOTM)
types of SOTM
Ground Vehicles, Maritime and Airborne
converts information into a signal that can be transmitted
Modulators, Demodulators and Modems
Block up converter and Low noise block
Amplifiers
Interference, Polarization
Filters
Material,Design,Size
Reflector
components or subsystems of an earth station installed in an outdoor location
outdoor unit (ODU)
components or subsystems of an earth station installed in an indoor locati9n or weatherproof shelter
Indoor Unit (IDU)
cable system to connect an ODU and IDU
Interfacility Link (IFL)
ODU
Antenna and Antenna Base
Feed Horn
Filters
LNB
BUC
tells you the direction to face
azimuth
tells you how high up in the sky to look
elevation
IDU
Modulators
Demodulators
Satellite Receivers
Modems
Tracking Devices
IFL
Radiofrequency Signals
Monitor and Control (M&C)
Power
summary of all power gains and losses
Link Budget
Considerations for Product Selection
Terminals
*band and frequency range
*nature of application
*auto or manuel acquisition
*size and portability
BUCs
*band and frequency range
*output power
*nature of application
*special requirements
LNBs
*band and frequency range
*gain
*frequency stability and reference
*phase noise
Calculate loss of signal strength along a path in space
free space path loss
application of FSPL
*estimating the best case for path loss at a given distance and frequency
Radiation patterns caused by diffraction of the transmitted signals
Fresnel Zones
two types of satellite
natural satellites, artificial satellites
for example- earth revolves around the sun, so it is a satellite. Moon revolves around earth,so it is also a satellite
Natural Satellites
designed and launched into space for a variety of purposes such as weather monitoring etc.
artificial satellites
acronym: INSAT
Indian National Satellite System
Acronym: IRS
Indian Remote Sensing Satellite
acronym: GSAT
Global Satellite
Basic Element of satellite communication
earth station,satellite,terrestrial system, user
a satellite radio repeater which a satellite may have many.
transponder
consist of one or more satellite space vehicles, a ground based station to control the operation of the system
Satellite System
includes control mechanism that support the payload operation
bus
the actual user information conveyed through the system
payload
a type of satellite wherein it simply “bounces” signals from one place to another
passive reflector
natural satellite of earth, visible by reflection of sunlight having a slightly elliptical orbit
moon
used by passive satellites for tracking and ranging purposes
radio beacon transmitters
launched by russia first active earth satellite in 1957.
Sputnik I
type of satellite capable of receiving,amplifying, reshaping,regenerating and retransmitting information
active satellite
satellite launched by U.S., transmitted telemetry information for nearly five months
Explorer I
satellite launched by NASA in 1958, a 150 pound conical shaped satellite. the first artificial satellite used for relaying terrestrial communications
score
first active satellite to simultaneously receive and transmit radio signals
Telstar I
lauched in 1963, and was used for telephone television, facsimile and data transmission and accomplished the first successful transatlantic video transmission
Telstar II
launched in february 1963, first attempt to place a geosynchronous satellite into orbit
Syncom I
First commercial telecommunications satellite. launched from cape kennedy in 1965 and used two transponders.
Intelsat I
Domestic satellite launched by former soviet union in 1966. it means lighting
Molniya
Domestic Satellites is also known as
Domsat
German Astronomer who discovered the laws that governs satellite motion
Johannes Kepler
point in an orbit closest to earth
Perigee
point in an orbit farthest from the earth
apogee
line joining the perigee and apogee through the center of earth, sometimes called line of apsides
major axis
line perpendicular to the major axis and halfway between the perigee and apogee
minor axis
path that a satellite can follow as it rotates around the earth
inclined,equatorial or polar
all satellite rotate around earth in an orbit that forms a plane that passes through the center of gravity of earth
geocenter
virtually all orbits except those that travel directly above the equator or directly over the north and south poles
inclined orbits
states that the square of the periodic time of orbit is proportional to the cube of the mean distance between the primary and the satellite.
harmonic law
high altitude earth orbit satellites operating primarily in the 2 GHz frequency spectrum with orbits satellite 22,300 miles above earth surface
geosynchronous satellite
angle between the earths equatorial plane and the orbital plane of a satellite measured counter clockwise at the point in the orbit.
angle of inclination
point where the polar or inclines orbit crosses the equatorial plane travelling from north to south
descending node
line joining the ascending and descending nodes
line of nodes
it is when the satellite rotates in an orbit direct above the equator, usually in a circular path
equatorial orbit
satellite rotates in path that takes over the north and south poles in an orbit that is close to earth and passes over and very close to both the north and south poles
polar orbit
important effect of the Earth’s equatorial bulge is causing elliptical orbits to rotate in a manner that causes the apogee and perigee to move around the earth
rotation of the line of apside
a geosynchronous earth is sometimes referred to it after arthur clarke
clarke orbit or clarke belt
to optimize the performance of a satellite communications system, the direction of maximum gain of an earth station antenna must be pointed directly at the satellite
antenna look angles or boresight
to ensure that the earth station antenna is aligned, two angles must be determined
azimuth and elevation angle
the location identified by a point on the surface of earth directly below the satellite
SSP or subsatellite point
vertical angle formed between the direction of travel of an electromagnetic wave radiated from an earth station antenna pointing directly toward a satellite and the horizontal plane
elevation angle
horizontal angular distance from a reference direction,either the southern or northern most point of the horizon
Azimuth
defined as the horizontal pointing angle of an earth station antenna
Azimuth Angle
determine the farthest satellite away that can be seen looking east or west of the earth’s longitude
limits of visibility
primary classifications for communication
Spinners and three-axus stabilizer satellites
uses the angular momentum of its spinning body to provide roll and yaw stabiliztion
Spinner Satellites
the body remains fixed relative to Earth’s surface while an internal subsystem provides roll and yaw stabilization
three axis stabilizer satellites
a frequency from earth station-to-transponder
Uplink Frequency
a frequency from transponder to earth station
downlink frequency
services by satellite
fixed point, broadcast,mobile, intersatellites
the geographical representation of a satellite antenna’s radiation pattern
footprint or footprint map
smallest beams,concentrate their poeer to very small geographical areas
spot beams
have wider beams that can accommodate the wide area with low concentration power
zonal beams
typically target up to 20% of the earth surface and therefore have EiRPs that are 3dB or 50% lower than spot beams
hemispherical beams
radiation patterns of earth coverage antennas have a beamwidth of approximately 17•
Earth Beams
an elliptically shaped area formed in the region between transmitter and receiver
Fresnel Zone
