SEW 101 PC 1
Common FEC (Forward Error Correction) Rates (4)
*1/2 (MOST Protection: for every 1 bit of data we add an extra bit of protection) *2/3 (for every 2 bits, add extra bit of protection) *3/4 (for every 3 bits, add extra bit of protection) *7/8 (FASTEST transmit: for every 7 bits, add extra bit of protection)
Delta 3 Squadrons (4)
*3 CTS (training), *4 EWS (Offensive), *5 EWS (for USSPACECOM / Green Door), *16 EWS (Defensive)
Digital Signal (6)
*Discrete wave that carries information in binary form *Represented by square waves *Described by bit rate and bit intervals *Finite numbers (ie 0 and 1) *Less prone to distortion *Carries data in the form of bits
Who handles allocation for civilian vs government?
*FCC (Federal Communications Commission) vs *NTIA (National Telecommunications and INformation Administration)
Magnetism
*Force exerted by magnet when they attract or repel each other *Caused by the motion of electric charges
Polarization orientations
*Linear (horitzontal, vertical, slant) *Circular (right- or left-hand)
Which are more impacted by scintillation / atmospheric effects?
*Scintillation: UHF (Narrowband) *Atmospheric: EHF (protected)
Analog signal (6)
*continuous wave that changes over time period. *sine wave *Described by: amplitude, frequency, phase, and/or period *no fixed range *more prone to distortions *transmits data in the form of a wave
Electromagnetic wave properties (4):
1) Accelerated charges are responsible for producing EM waves 2) Propagate by varying e-fields and b-fields 3) Travel through empty space at the speed of light 4) Can carry energy
Characteristics of a wave (5)
1) Amplitude 2) Wavelength 3) Frequency 4) Phase 5) Polarization
Quadrate Amplitude Modulation (QAM) definition and pros/cons (3)
1) Combination of amplitude and phase modulation 2) Pros: transmit more bits per symbol 3) Cons: susceptible to noise
ASK definition (pros/cons) (4)
1) Digital equivalent of AM 2) Pros: simple 3) Cons: susceptible to noise 4) Amplitude Modulation Depth
FSK definition (pros/cons) (5)
1) Digital equivalent of FM 2) Pros: less susceptible to noise 3) Cons: requires large bandwidth/bit than ASK 4) Order of modulation 5) Frequency deviation
PSK definition, pros/cons (3)
1) Digital equivalent of PM 2) Pros: less susceptible to noise and bandwidth efficient 3) Cons: requires complex receivers and transmitters
5 aspects of electromagnetism
1) One of 4 fundamental forces in the universe 2) 2nd strongest force 3) Operates at a distance 4) Acts on charge 5) Attracts and repels
Three atmospheric absorption bands?
1) Water vapor 2) Carbon Dioxide 3) Ozone
Charles-Augustin de Coulomb
18th century physicst, studied attractive/repulsive nature of electrical charges and magnets
Andre-Marie Ampere
19th century physicist, studied relationship between electricity and magnetism
How many possible outputs for BPSK?
2^1 = 2 = 1 or 0
How many outputs for QPSK?
2^2 = 4 ("quad") = 00, 01, 10, 11
FSK Order of Modulation
4 Frequencies, 4 Symbols
What did Andre-Marie Ampere show (2)
A magnetic needle is affected by a current in a wire, parallel wires attract or repel each other based on the direction of current
Maxwell Equation FOUR
A moving electric field produces a magnetic field, and a moving magnetic field produces an electric field
Define electromagnetic wave:
A wave that is composed of oscillating magnetic and electric fields
NATO frequency A-M (EU, NATO, US ECM)
ABCDEFGHIJKLMNOP
RF Signals can be classified as: (2)
ANALOG (continuous); DIGITAL (discrete)
Types of Digital Modulation (4)
ASK, FSK, PSK, QAM (Quadrature Amplitude Modulation)
Symbol rate =
Aggregate data rate / bits per symbol ***Easiest way to remember: Data/FEC/Bits = symbol rate = BANDWIDTH of the Signal (in Hz, with whatever was in front...k, M, etc)
Types of Analog Modulation (3)
Amplitude, Frequency, Phase (AM, FM, PM)
Maxwell Equation THREE
An electric current in a wire produces a magnetic field whose direction depends on the direction of the current
Allocation
Assignment of frequencies to a service
Two types of PSK:
BPSK (Binary) and QPSK (Quadrature, can be extended to 8PSK and beyond, but usually switch to QAM at this point)
Bits per symbol for each: BPSK QPSK 8PSK 16QAM 32QAM 64QAM
BPSK: 1 QPSK: 2 8PSK: 3 16QAM: 4 32QAM: 5 64QAM: 6
Symbol rate is equal to :
Bandwidth of the Signal (in G, k, etc) Hz
Binary code definition
Base is two (two states 0 and 1) (2^0 =1, vs 2^8-256), 8 bits = 1 byte
FEC rate =
Baseband Data Rate / Aggregate Data Rate (B/A)
Define amplitude modulation (AM) (or FM, PM)
CARRIER wave is modulated in amplitude / frequency, phase
James Clerk Maxwell
Calculated speed of electromagnetic field to approx speed of light, LIGHT IS AN ELECTROMAGNETIC DISTURBANCE, electricity + light calculations
Why is amplitude modulation more susceptible to noise?
Closer to the noise floor
What is a sine wave?
Continous, uniform wave with constant frequency, amplitude, and phase
BANDWIDTH equals:
Data/FEC/bits (example: 2000Mb / (3/4) / 4 = 666.66MHz
What is the SEW Delta and where is it?
Delta 3, Peterson
Wavelength definition, representation, measurement
Distance between crests (meters), measure of how long the wave is physically
Most affected by atmospheric affects?
EHF
What are RF Signals?
Electromagnetic waves that are manipulated and changed to send a message
What are RF signals?
Electromagnetic waves that are manipulated and changed to send a messsage
Assignment
Grant of national authority to use a SPECIFIC frequency for a particular entity (GPS)
Constellation diagrams are:
Graphical representation of digital modulation techniques (such as PSK and QAM; PSK in circles, QAM in squares)
Energy and Frequency relationship
Greater frequency = higher energy
Amplitude definition, representation, measurement
Height of the wave, represents power, measured in Watts (W)
What creates larger atmospheric refraction angle?
High Pressure + Low Temperature
Basic definition of electricity
Imbalance of charges
Wavelength and frequency relationship
Inverse (shorter wave, greater frequency)
Coulomb's Law
Inverse Square Law: the force is inversely proportional to the square of the distance between the charges
France & Iran
Iran jammed EUTELSAT to prevent accessibility to broadcast (BBC)
Why is EHF (protected) most utilized for military?
It's most resistant to nuclear
Captain Midnight
Jammed HBO, resulted in Electronic Communicatiosn Privacy Act of 1986 (satellite hijacking a felony)
IEEE frequency band names
L S C X KU K KA
Michael Faraday established:
Link between electricity and magnetism: magnet passing through a wire creates current in the wire, light can be affected by electrical currents, connecting LIGHT to ELECTRICITY and MAGENTISM
Maxwell Equation TWO
Magnetic poles come in pairs that attract and repel each other, much as electric charges do
Are electricity and magnetism different?
No, they are the same force operating in different ways
Frequency definition, representation, measurement
Number of cycles a wave completed every second *Hertz
Phase definition
Offset a wave from a given point (measured in degrees)
Three main atmospheric windows?
Optical, infrared, and radio windows
Polarization definition
Orientation of a wave, from e-field perspective
Electromagnetic radiation (EM) movement produces:
Oscillating (orthogonal) e-field and b-field, which travel perpendicular to each other in a bundle of energy called a photon
Youngs Double Slit Experiment proved and demonstrated:
PROVED light exhibits properties of waves, DEMONSTRATED light's constructive and destructive behaviors
Delta 3 mission
Present combat-ready electromagnetic warfare professionals to integrate, synchronize, and execute fires for US, Allied and Coalition Forces
Define scintillation
Rapid fluctuations in the phase and amplitude of a wave that is caused by rapid variations i(mainly in the electron density in ionosphere)
How do atmospheric layers affect electromagnetic signals?
Refract and distort low frequencies (UHF - Narrowband), water absorbs/destroys high frequencies (EHF - Protected)
Atmospheric windows?
Regions in the EM spectrum where energy can be fully transmitted
Pulse Code Modulation (PCM) PCM types (3)
Sampling, Quantizing, Encoding
Define atmosphere scattering
Scattering of electromagnetic waves makes sensor create hazy image *Absorption + Scattering = Attenuation
Static electricity
Separation of charges, opposite charges attract / like charges repel each other
Digital Modulation is:
Shift Keying (SK)
Baseband Data Rate:
The amount of information you are sending (data rate is based on the baseband)
Aggregate Data Rate
The data rate after Forward Error Correction is applied (adds extra bits to protect information)
Electromagnetic (EM) radiation is:
The flow of energy (photons) at the speed of light through free space or through a material medium in the form of electric and magnetic fields that make up electromagnetic waves
Maxwell Equation ONE
The force of attraction between electric charges is inversely proportional to the square of the distance between them
Current electricity
The movement of electrons through a conductive material in a uniform direction
Why is an analog signal more susceptible to noise?
There is not a finite value (digital is binary, either 0 or 1)
Signal domains?
Time domain (waves) vs frequency domain (lines/very narrow/tall wave)
Most affected by scintillation?
UHF
International Telecommunication Union (ITU)
UN's agency for information/communication technologies, ALLOCATE global radio spectrum & satellite orbits
What is Fourier transfer?
Used to convert a signal between te frequency and time domains
Fourier Transfer
Used to convert a signal between the frequency andterm-23 time domains
ITU frequency band names
VHF, UHF, SHF, EHF (very, ultra, super, extremely)
Modulation definition
Variation of a part of an EM wave for the transmission of information
Can the electromagnetic force operate at a long distance?
YES; physical interactions that do not have any observable contact are magnetic fields, but strength gets weaker as distance grows
Two types of modulation
analog and digital
Pulse Code Modulation (PCM) is used to:
convert analog signals to digital signals
Maxwell's unified theory of electromagnetism
electricity and magnetism are not separate forces - they are the same (electromagnetic force) acting in different ways
Modulation is process of:
superimposing a low frequency signal onto a higher frequency signal (baseband + carrier wave)
Scintillation is a term for:
variations in strength, position, and polarization of transmitted signals passing through a medium
