Penn State Talk EE 497F

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Penn State Talk- EE 497F

• September 2003

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What is STK?

• Satellite Tool Kit (STK) is a commercial
  off-the-shelf (COTS) geospatial analysis and
  visualization software package
• STK (free) and the comprehensive set of STK
  add-on modules provide users with integrated
  land, sea, air, and space elements
• The STK software suite provides technology
  solutions for all phases of industry programs and
  initiatives.

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STK Video
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STK 5.0 Terminology

• STK Workspace - The outer most space of the
  primary STK window. It serves as a container for
  all other components.
• Grey Space - The darker grey area in the center
  of the STK Workspace that contains Secondary
  Windows in their default state.
• Secondary Window - All windows within the primary
  window (Object Browser, Visualization Window, or
  HTML Viewer)
• Object Browser - Secondary window that is used to
  hold all instances of STK objects created by the
  user.

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STK 5.0 Terminology

• Visualization Window - Any instance of either 2-D
  or 3-D (VO) Graphics window.
• HTML Viewer Any instance of an embedded HTML
  window.
• Title Bar Appears at the top of the STK
  Workspace and displays the name of the last
  selected secondary window.
• Message Viewer Returns information about STK
  with respect to data sources and mouse actions.
• Status Bar Appears at the bottom of the STK
  Workspace and displays information about most
  recently selected Object, current lat/long of
  your cursor in 2-D Graphics window, current
  scenario time, time step, animation frame rate,
  and resolution level used to display on selected
  2-D Graphics window.

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Toolbar Manipulation

• Open the View Menu and select Toolbars -gt
  Customize
• Here we show/hide existing toolbars or create new
  ones
• You can also create a new toolbar by holding down
  the Ctrl key and dragging a button to the Grey
  space
• Create a New toolbar
• You can add buttons to your new toolbar by
  dragging buttons from other toolbars
• By holding down the Ctrl key you are copying the
  button to the new bar, without the Ctrl key you
  are cutting the button from the old toolbar
• You can also add buttons by clicking on the
  Command tab in the Customize tool and dragging
  the buttons from the different categories into
  the toolbar
• You can delete your toolbar by highlighting your
  toolbar in the Toolbar tab, and clicking Delete

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Window Management

• STK has four window state options that can be
  selected by right-clicking on the title bar of
  the windows
• Integrated The default window state. An
  Integrated window is confined to the grey area,
  when it intersects the STK Workspace it goes
  behind it
• Docked Is a window that is fixed or parked
  somewhere in the STK Workspace
• Floating Is a window that is detached from the
  STK Workspace. Floating windows are useful when
  you need a window to be in front of, or outside
  the STK Workspace
• Full Screen Is useful for visualizing certain
  events that require more Desktop space.

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Create a New Scenario

• To create a new scenario either click on or
  click File -gt New
• Double click on Scenario1 in the Object Browser,
  or highlight Scenario1 and click
• Under Basic -gt Time Period change the Start time
  to 29 Sep 2003 000000.00, the Stop time to 30
  Sep 2003 000000.00, and the Epoch to 29 Sep
  2003 000000.00
• Now go to the Animation menu. Make sure that
  your Start Time matches the time we entered in
  the Time Period menu, and change the Time Step to
  10 sec
• Now go to the Units menu and set the units to
  Kilometers, Seconds, Gregorian UTC, and Degrees

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Save Your Scenario

• Lets save the scenario weve got so far. Click
  File -gt Save As
• Create a new folder with the same name as you
  intend to name your scenario, well call ours
  HubbleLink
• This avoids accidental overwrites when two
  scenarios have the same object names
• Open your new folder, change the file name to
  HubbleLink.sc, and click Save

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Create a Satellite

• Click on the in the menu bar. The Orbit
  Wizard will appear. In the Orbit Wizard you can
  define a number of generic types of orbits for
  your satellite. Lets dismiss this window.
• Right click on the satellite and rename it mysat.
• Open up the satellite properties and go to the
  Basic -gt Orbit menu and check to make sure that
  the Start, Stop, and Orbit Epoch times match your
  scenario times. Also check to see that your Step
  Size is the same as we set it earlier.

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Set The Orbit Properties

• Lets create a circular orbit. Set the following
  parameters
• Semimajor Axis 7000 km
• Eccentricity 0
• Inclination 40 deg
• RAAN True Anomaly 0 deg
• Click OK and we can view the orbit track in the
  2D and 3D windows
• If we press the Start button we can animate
  the scenario view our orbit
• Now reset the scenario by pressing the button

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Create a Satellite Using the Satellite Database

• Click Insert -gt Satellite From Database
• Check the Common Name Box and type in Hubble
• Click on the HUBBLE satellite, make sure Auto
  Propagate is checked, and that the times matched
  what we entered earlier, and click OK
• Using the same method as before, insert TDRS_East
  into your scenario from the Satellite database
• Now would be a good time to save your scenario
• Since weve already created a folder to save to,
  we can just hit the button
• Close the Satellite Database

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Insert Facility From Database

• Click Insert -gt Facility From Database
• Check Site Name, and type in Greenbelt
• Highlight Greenbelt, make sure that the Creation
  Class says Facility, and click OK
• Now rename Greenbelt to Goddard
• Click Insert -gt City From Database
• Check City Name, and type in State College
• Highlight State College, make sure that the
  Creation Class says Facility, and click OK

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Creating Sensors

• Highlight TDRS_East in the Object and click on
  the Sensor button
• Change the name to TDRSxmit, and then open up its
  properties
• Lets make the sensor type Simple Sensor and the
  Cone Angle 45 deg
• Click on Pointing in the left menu
• Change the Pointing Type to Targeted
• Under Available Targets Select Goddard and click
  the button to add it as a target
• Create another sensor named TDRSrcv with the same
  settings, but this time target Hubble
• Now create a sensor on the Goddard Facility with
  the same properties, but lets name it
  GoddardSensor and target it to TDRS_East
• Add a sensor to Hubble
• Simple Conic 5 deg Cone Angle
• Target TDRS_East

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Transmitters

• Insert a transmitter on the TDRSxmit, name
  it TDRSxmit
• Simple Source Transmitter
• Details 14.5 Ghz Freq., 30 dbW EIRP, 16
  Mbits/sec Data Rate, Mod. Type BPSK
• Insert a transmitter onto HubbleSensor with the
  same properties, name it HubbleXmit

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Receivers

• Now add a Receiver to TDRSrcv, name it
  TDRSrcv
• Make it type Simple Receiver
• Details 20.0 g/T and set Frequency/Bandwidth to
  Auto Track/Scale
• Create a Receiver on GoddardSensor with the same
  properties as the Receiver on TDRSrcv, but name
  it GoddardRcv
• Save your scenario

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Link Budget

• Highlight the GoddardReceiver and click the
  button
• Select the TDRS_East/TDRStrans and click the
  Compute button
• Click on the Link Budget button under Reports

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Create a Constellation

• Create a new constellation by clicking the
  button
• Rename it TDRSx
• Under the Properties -gt Basic -gt Definition
• Highlight the TDRS transmitters under Available
  Objects and click the button
• Create a TDRSr constellation and add TDRSrcv to
  the available options list

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Create a Chain

• Click the button to add a Chain
• Rename it Link
• Open up the Properties -gt Basic -gt Definition
• Double click on the following objects listed
  under Available Objects in the following order
• HubbleTrans
• TDRSr
• TDRSx
• GoddardReceiver
• Click OK
• Right Click on Link, go to Chain Tools, and
  Select Compute
• Now animate the Scenario and watch for the link
  between Hubble and Goddard

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Bent Pipe Link Budget

• Right click on Link and go to Chain Tools
• Click on Reports
• Create a Bent Pipe Comm Link report

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Reference Material
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Classical Orbital Elements

• Semimajor Axis (a) This is the distance from
  the center of the ellipse to the farthest edge
• Eccentricity (e) A number between 0 and 1 that
  describes how circular the orbit is. An
  eccentricity of 0 is a circle
• Inclination (i) A number in degrees that
  describes the tilt of the orbit relative to the
  Earths equator. 0 inclination is an equatorial
  orbit. 90 is a polar orbit. Anything between 90
  and 180 is a retrograde orbit one that goes
  against the Earths rotation
• Argument of Perigee A number in degrees that
  describes where the perigee of the orbit occurs
  measured relative from where the satellite
  crosses the equator headed Northward
• Right Ascension of the Ascending Node (RAAN) or
  Longitude of the Ascending Node (LAN) This
  describes where the ellipse crosses the equator
  of the Earth on its way Northward
• True Anomaly or Mean Anomaly Where the
  satellite is in the orbital ellipse at the Epoch
• Epoch The moment in time at which these values
  have been defined for the orbit, creating a
  snapshot of where the satellite was at this moment

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Classical Orbital Elements
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Comm terms and equations

• Antennas are Described by their Gain Pattern, g
• Indicates how Gain is Spatially Distributed with
  Respect to the Antenna Coordinate System
• Gain
• Max Value of Gain Pattern
• Efficiency x 4p/l2 x Area of Antenna Aperture 
• Area is Function of Antenna Type (Function of the
  Diameter, d) 
• l speed of light/frequency
• Beamwidth
• Measure of the Angle Over which Most of the Gain
  Occurs
• l/d x Square Root(Efficiency)
• Sidelobes Amount of Gain in Off-Axis Directions
• NOTE Ideally, You Want Highly Directional
  Antenna Patterns with Max Gain Over Narrow
  Beamwidth with Negligible Sidelobes

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Comm terms and equations

• EIRP
• Effective Isotropic Radiated Power. Pronounced
  urrpp. A handy figure of merit used when
  comparing transmitters. Equal to the gain times
  the output power. A 10 watt transmitter with an
  antenna gain of 10 has an EIRP of 100 watts, the
  same as a 5 watt transmitter with an antenna gain
  of 20. EIRP is most often described in units of
  dBW
• RIP
• Received Isotropic Radiated Power. Pronounced
  rip. Its basically the EIRP minus all the
  losses you encountered on your way from the
  transmitter to the receiver

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Comm terms and equations

• Flux Density
• How much power per unit area. Usually measured in
  db(watts/meter2).
• g/Tº
• Receiver gain divided by the equivalent noise
  temperature. Common figure of merit for comparing
  receivers.
• C/N0
• Carrier to Noise Density. Advantage is that it
  is bandwidth independent. Pronounced see over N
  nought. Basically the received carrier power
  divided by the background noise power density.
  Every system has some background noise associated
  with it. The larger the C/No the better.

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Comm terms and equations

• C/N
• Carrier to noise ratio. Also abbreviated as CNR.
  Similar to C/No, but in this case the receiver
  bandwidth is included.
• Eb/N0
• Energy per bit over noise. The digital
  communications equivalent to signal to noise
  ratio for analog communications. The higher the
  Eb/No the better.
• BER
• Bit Error Rate. The number of bad bits divided by
  the total number of bits. Comm links typically
  require a BER of 10-6 or better.

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Analog Communications System
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Digital Communications System
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Comm terms and equations

• C/N (dB) RIP g/T K(BW)
• K Boltzmans Constant 1.38062259e-23 J/K
  -228.6 dBJ/K
• BW Bandwidth (Hz)
• RIP Received Isotropic Power (dBW)
• Bandwidth Despread BW (dB) CDMA Gain (dB)
• C/No (dB) C/N (dB) Bandwidth Despread
• Eb/No (dB) C/No(dB) Predemod Gain/Loss(dB)
  DataRate (dB)
• For BER, You Need to Look Up the Eb/No in the
  Appropriate Source Mod File and Retrieve the BER
  Value from the Lookup Table

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Comm terms and equations

• Link budget
• A summary of the all gains and losses for a given
  link.
• Typically done on a spreadsheet.
• Spreadsheet solutions do not allow for time
  varying parameters or geometry varying
  parameters.
• Contour plots
• Most common is EIRP. Gives user instant idea of
  where they have coverage and where they dont.

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Communications Systems Modeling
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Transmitter models (common)

• 4 transmitter models in STK
• Carrier frequency
• Raw data rate
• Signal modulation type, CDMA coding gain
• Transmitter polarization
• Type (Vertical, Horizontal, RHC, LHC, Linear,
  Elliptical)
• Alignment (w.r.t. Antenna body, X, Y or Z Axis)
• RF bandwidth
• Auto-scale (based on modulation type and data
  rate)
• User specified transmitter bandwidth
• Post transmit gains and losses

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Transmitter models

• Simple model
• Transmitter output (EIRP in watts, dBW)
• Medium model
• EIRP Power x Gain (models isotropic antenna)
• Complex model
• Model antennas, analytical as well as gain
  measurement data
• Gaussian, Parabolic, Square Horn, Aperture,
  Dipole, Helix, ITU specs
• EIRP Power x Antenna gain (computed by STK)
• Multibeam model
• Model multiple antenna beams, analytical as well
  as gain measurement data
• EIRP Power x Antenna gain (computed by STK)

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Receiver models (common)

• 4 receiver models in STK
• Receiver RF frequency
• Auto-track (transmitter) frequency
• Receiver tuned frequency
• Receiver RF bandwidth
• Auto-scale (receiver) bandwidth to the
  transmitted signal (patented algorithm)
• Fixed receiver bandwidth
• Receiver polarization
• Pre-receive gains and losses
• Pre-demodulation gains and losses
• Rain outage

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Receiver models

• Simple model
• Receiver g / T (dB / K)
• Medium model
• Isotropic antenna gain
• Model system noise temperature
• Compute g / T
• Complex model
• Model antennas and system/antenna noise
  temperature
• Compute g / T
• Multibeam model
• Model multiple beam antennas and system/antenna
  noise temperature
• Compute g / T

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Complex Antenna Model File Formats

• GIMROC
• ITU GIMROC Satellite Antenna Files are Sample
  Data Points of Antenna Gain Contours Projected
  onto the Surface Of The Earth
• Data Points are Recorded in Terms Of Latitude and
  Longitude
• Resolution of Data Points is Limited and in Some
  Cases Only a Few (1-4) Contours are Provided
• Very Little Additional Information Available
  Regarding Antenna Dish Type, Size, Transmitter
  Frequency and Actual Maximum Gain
• Intelsat
• Gain for an Intelsat Antenna is Determined from
  Data Stored in an External File in a Format
  Commonly Used by Intelsat
• Other External Files
• PhiThetaPattern, ThetaPhiPattern and
  SymmetricPattern
• AzElPattern and ElAzPattern

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Theta-phi coordinates

• Theta - ?
• Angle off the boresight.
• Range is 0 to 180 degrees.
• Phi - ?
• Angle about the boresight.
• Range is 0 to 360 degrees.
• Commonly used to model traditional antennas such
  as parabolic.
• For a symmetric pattern, pattern is symmetric
  about the boresight (gain is independent of ?)

?
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Azimuth-elevation coordinates

• Azimuth
• Rotation angle about -y.
• Range is -180 to 180 deg.
• Elevation
• Rotation angle about x.
• Range is -180 to 180 deg.
• Traditionally used by geo-stationary satellites
  where azimuth is from the boresight toward the
  east and elevation is from the equator to the
  north.

Azimuth
Elevation
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Analog vs. digital

• Computations for analog and digital
  communications links are common until C/N
• Signal to Noise ratio computations for analog
  links are usually handled in post processing
• Eb/No and BER are computed for digital links

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STK modulation types

• Analytical modulation schemes
• BPSK Bi-Phase Shift Keying
• QPSK Quadrature Phase Shift Keying
• OQPSK Offset Quadrature Phase Shift Keying
• MSK Minimum Shift Keying
• FSK Frequency Shift Keying
• NFSK Non-Coherent Frequency Shift Keying
• DPSK Differential Phase Shift Keying
• QAM Quadrature Amplitude Modulation

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BPSK Binary Phase Shift Keying
43
Code Division Multiple Access

• Code Division Multiple Access (CDMA) is a
• Digital Wireless Technology Developed by QUALCOMM
  in 1995
• Digital Spread-Spectrum Modulation Technique
• Used Mainly with Personal Communications Devices
  Such as Mobile Phones
• Digitizes the Conversation and Tags it with a
  Special Frequency Code
• Data is then Scattered Across the Frequency Band
  in a Pseudorandom Pattern
• Receiving Device is Instructed to Decipher Only
  the Data Corresponding to a Particular Code to
  Reconstruct the Signal
• In 1999, the International Telecommunications
  Union Selected CDMA as the Industry Standard for
  New Third-Generation" (3G) Wireless Systems
• Leading Wireless Carriers are Building/Upgrading
  to 3G CDMA Networks
• Over 100 Million Consumers Worldwide Rely on CDMA

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CDMA bandwidth spread

• Transmitter
• Signal bandwidth is spread by the spreading gain
• Receiver
• Signal bandwidth is de-spread by the spreading
  gain
• C/No is improved by the CDMA spreading gain

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Transmission light speed delay

• Near Earth and GEO satellites
• Impact on data transmission
• Significant impact on satellites beyond GEO
• Telemetry and control
• Data transmission protocols
• Access timing and tracking
• STK access computations take into account the
  light speed delay for transmitter and receiver
  accesses

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Polarization

• Polarization
• Quantity Describing the Orientation of the
  Electric Field Vector with Reference to the
  Antenna's Orientation
• 3 Basic Types
• Linear
• Elliptical
• Circular
• Linear Polarization can be Horizontal or Vertical
• Circular polarization can be right-handed or
  left-handed
• Polarization Orientation is a Direct Function of
  the Attitude of the Antenna's Parent Body
• When Parent Body Attitude Changes, Polarization
  Alignment Between the Receiver and the
  Transmitter May Change, and these Changes Will
  Impact G/T and Subsequent Link Performance Values
  such as C/N, Eb/No, BER, etc.

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Transponders

• Analog (bent-pipe)
• Power amplifiers with RF frequency up/down
  conversion
• Modeled as a back-to-back connection of a
  receiver and a re-transmitter
• Digital (re-generative)
• Complete demodulation and re-modulation of
  information signal
• Combination of a receiver and a source
  transmitter (all source transmitter parameters
  can be set)

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Transponders (all analog models)

• ANALOG Re-Transmitters (Bent-pipe)
• Saturated input flux density
• Polarization
• Transponder output power back-off transfer
  function
• Modeled as a polynomials (linear or dB scale)
• Transponder frequency conversion
• Modeled as a polynomial
• Post-transmit gains / losses

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Transponder models

• Simple model
• Saturated output EIRP
• Output of the Transmitter when the Amplifier is
  at its Saturated State
• Medium model
• Saturated EIRP Saturated Power Gain
  (isotropic antenna)
• Complex model
• Model antennas
• Saturated EIRP Saturated Power Antenna gain
  (computed)

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Link constraints

• Minimum and/or maximum parameter values to be
  satisfied before a link is considered available
  (closed) between a transmitter and receiver

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Link constraints

• Basic communication link constraints
• RIP, frequency, Doppler shift, flux density, C/N,
  C/No, Eb/No, BER
• Refracted elevation angle range
• System antenna noise temperature
• Special
• GEO belt exclusion
• Space object exclusion

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Communications graphics

• 2-D contours
• EIRP, antenna gain, RIP, flux density at user
  specified levels
• Drawn on the surface of the oblate Earth
• Drawn on a spheroid at a given altitude
• Access constraints
• Show access between communications transmitters
  and receivers graphically
• 3-D antenna beam gain patterns
• Antenna body axis vectors

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Propagation and Noise Models
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Propagation and Noise Models

• Rain models
• Attenuation models
• Noise calculation

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Rain models - basics

• STK can employ one of 4 different models
• Slightly different data and empirical formulas
• Calculations are based on geographic location
  data (rain regions)
• Rain height
• Rain rate
• Outage percentage specified by the user
• Ambient temperature
• Empirical formulas are applied to this data along
  with information on frequency to determine the
  rain-induced noise and loss for a link

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Rain models - implementation

• STK does NOT compute the outage percentage
• Users specify the outage, which the model turns
  into a loss
• STK uses the lower of the Xmtr/Rcvr to select the
  rain region
• Users may override the rain region data for rain
  height, rate, and temperature
• Example - Death Valley and San Fransisco are in
  the same rain zone

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Attenuation models - basics

• Two models are currently available
• Simple satcom model
• Assumes one end of the link is on the Earth
  surface and the other is above the troposphere.
  Empirical data-based model
• ITU model
• Specifies specific attenuation and atmosphere
  models, which AGI incorporates into a ray-traced
  calculation

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Attenuation models - implementation

• AGI Ray Tracing - ITU Model
• Generate a set of concentric spherical shells and
  break a line segment through the set of shells
  into individual segments
• Atmospheric conditions are determined at the
  bottom of each shell (worst-case)
• Determines the specific attenuation
• Applied to the length of the segment through the
  shell
• Total path attenuation is the sum of the
  attenuation on each line segment

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ITU specific attenuation

• Compute options
• High fidelity physics-based calculation based on
  molecular spectral lines - good for frequencies
  up to 1,000 GHz
• Curve-fit approximation - faster, slightly less
  accurate, limited to freq lt 300 GHz
• Global standard atmosphere model
• Atmospheric data as a function of season and
  latitude

60
Attenuation models - limitations

• Simple satcom model is simple, fast and accurate
  for Earth-station to satellite links
• Satcom model limited the same way as rain models
• ITU Ray Traced model is recommended for all other
  scenarios
• Ionospheric Attenuation (for STK 5.1)

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System noise - basics

• System noise Sum of all individual noise
  contributors
• Noise due to the environment - referred to as
  antenna noise
• Anything with a physical temperature radiates RF
  energy - Sun, Earth and cosmic background
• A medium that absorbs RF energy re-radiates
  energy as noise - atmospheric gases, rain
• Noise added by the waveguide between the antenna
  and the receiver circuitry
• A function of the loss and the physical
  temperature of the waveguide
• Noise due to losses within the receiver circuits
• Noise figure

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System noise - implementation

• The only contributors that are difficult to
  compute are the environment noise terms
• Antenna noise is the integral of the noise temp
  in a given direction multiplied by the antenna
  gain over the sphere enclosing the antenna

63
Frequency Spectrum Sharing Interference Analysis
64
Frequency Spectrum Interference

• Definitions
• Link performance analysis under interference
• Desired link analysis
• Interfering link analysis
• EPFD validation tool for ITU-R
• Examples
• Questions and answers

65
Frequency spectrum sharing

• Frequency spectrum sharing
• Frequency spectrum is a very limited resource
• Most frequency bands are already allocated to
  certain services
• New emerging applications need more more
  bandwidth
• Broadband data services
• Satellites phones
• Broadcast satellites
• LEOs need to share frequency bands with
• Terrestrial microwave links
• Existing GEO satellite links
• Share frequency bands AND avoid interference

66
Definitions

• EPFDDOWN
• Equivalent Power Flux Density being input into
  GEO Earth station receivers by the orbiting LEO
  transmitters
• EPFDUP
• Equivalent Power Flux Density being input into
  GEO satellites receivers by the orbiting LEO
  transmitters and LEO Earth station transmitters
• EPFDIS
• Equivalent Power Flux Density being input into
  satellites receivers of one constellation by the
  transmitters of another satellite constellation
• Measured in units dBW / m2 per Ref bandwidth

67
Reference bandwidth

• Reference Bandwidths are set for Power Flux
  Density (PFD) comparison of different systems
• 4 KHz
• 40 KHz
• 1 MHz

68
Access time filter

• Approach
• Determine intervals of time when Desired
  Transmitters have line-of-sight with Receivers
• Determine intervals of time when Interfering
  Transmitters have line-of-sight with Receivers
• Compute times when interference opportunities
  exist

69
Near field objects

• STK does not analyze objects in the near field
  (within d2/2l) of the antennas
• Interference between receivers and transmitters
  on the same satellite or facility is not an issue

70
Selection Criteria

• Satellite Selection Criteria (for CommSystem)
• Satellite which offers highest elevation angle
  from the receiver position
• Satellite which is the closest (minimum range) to
  the receiver position
• Antenna Beam Selection Criteria (for Multibeam
  Antenna)
• Beam which offers maximum antenna gain to the
  communications link
• Beam which offers the minimum angle from the
  antenna bore-sight

71
Comm system graphics

• Desired links
• Identified for the duration when the link is
  available
• Default color is green (All colors are user
  selectable)
• Interfering links
• Identified for the duration of interference
• Default color is white
• Highest interfering link
• Identified for duration of the highest
  interference
• Link is changed when the highest interfering
  source is changed
• Default color is red

72
Comm Plugins
73
Communications Plugins

• Transmitter Model
• Plugin Source Transmitter for Transmitter Model
  Type
• Receiver Model
• Plugin Receiver for Receiver Model Type
• Custom Antenna Gain Model
• Transmitter or Receiver Antenna Beam Type
• Comm Constraints User Plugin Model
• Receiver (Implemented)
• Transmitter (Future)

74
Communications Plugins

• Rain Model
• Scenario Level RF Environment Plugin Rain Model
  Type
• Gaseous Absorption Model
• Scenario Level RF Environment Custom Absorption
  Plugin Model Type
• Satellite Selection Model
• CommSystem Link Definition Link Criteria Plugin
  Selection Strategy Model
• Antenna Beam Selection Model
• Multibeam Source Antenna Beam Selection Criteria
  Custom Plugin Strategy Model

75
Dynamic Link Analysis with STK/Communications
76
Dynamic Link Analysis w/ Comm

• Basic Static Comm Link (GEO Downlink) in STK
• Static Downlink with a Dynamic Noise Source
• Dynamic Links and RF Interference
• Communications with a Satellite Constellation
• STK/Chains for Link Analysis
• End-to-End Communications Analysis

77
Basic Static Comm Link (GEO Downlink) in STK

• Create Static Downlink From a Geostationary (GEO)
  Satellite to a Ground Station
• Fundamental STK/Comm building blocks or objects
• Transmitters
• Receivers
• Static link-budget calculations
• STK/Coverage to Evaluate System Performance Over
  a Region
• RF environmental models
• Rain
• Atmospheric Attenuation (Absorption Loss)

78
Create Scenario

• S_AmGEO GEO Satellite
• Long Asc Node 60 degrees W
• GEOxmit Complex Source Transmitter on GEO
  satellite
• Gaussian Antenna Type
• Data Rate 10 MBits/Sec Freq. 5 GHz Power
  23 dBW
• Beamwidth 12.5 deg Antenna Efficiency 55
• Washington DC Facility
• MediumGatewayRcv Receiver
• Gain 38 dB
• Transmission Line Temperature 290 K Noise
  Figure 1
• Include Rain and Atmosphere in System Temperature

79
Link Budget Report

• Compute Access
• Generate Link Budget Report
• Custom Report Link Budget Detailed
• View link-budget report e.g.
• Xmtr Power (dBW) Xmtr Gain (dB) EIRP (dBW)
  
• 23.000 19.9567
  42.957
• Atmos Loss (dB) Rain Loss (dB) Prop Loss
  (dB)
• 0.0000 0.0000
  -197.9430
• Tatmos (K) Tantenna (K) Tequivalent (K)
  
• 4.003 294.003
  369.091
• g/T (dB/K) Eb/No (dB) BER
  
• 12.328666 15.9415 3.888376e-019

80
Define Coverage

• Create US_Coverage Coverage Definition
• Load usstates.rl Region List File for Custom
  Region
• Use MediumGatewayRcv as Point Definition in
  Associate Class
• Assign GEOxmit as Asset
• Create Eb_No Figure of Merit
• Access Constraint FOM Type
• Constraints Eb/No

81
Add Atmosphere

• Add Rain Model
• Crane 1985
• Surface Temperature 3.15 deg C
• Add Gaseous Absorption Model
• Simple Satcom
• Water Vapor Concentration 7.5 gm-3
• Temperature 293.15 K

Without atmospheric effects
With atmospheric effects
82
Atmospheric Effects on Link Budget

• Refresh Link Budget Report
• Xmtr Power (dBW) Xmtr Gain (dB) EIRP (dBW)
  
• 23.000 19.9567
  42.957
• Atmos Loss (dB) Rain Loss (dB) Prop Loss
  (dB)
• -0.0597 -1.2670
  -199.2698
• Tatmos (K) Tantenna (K) Tequivalent (K)
• 4.003 437.301
  512.389
• g/T (dB/K) Eb/No (dB) BER
  
• 10.903998 13.1901 5.346490e-011

83
Static Downlink with a Dynamic Noise Source

• Analyzing the Effects of Moving Objects
• Sun Outage in GEO to Ground Station (Downlink)
• Reports and Graphs of Link Performance and
  Availability
• Parametric Analysis and Post-Processing
• 3D Visualization Capabilities of STK/VO to
  Illustrate the Physical Effects that Occur During
  a Sun Outage

84
Create Groundstation

• Facility at Quito, Ecuador
• ParabolicRcv Complex Receiver
• Parabolic Type Az 89.357 deg El 68.263 deg
• Diameter 1.5 m Antenna Efficiency 55
• Transmission Line Temperature 290 K Noise
  Figure 1
• Include Sun, Rain and Atmosphere in System
  Temperature
• Rain Outage 0.1
• Compute Access to GEOxmit transmitter on S_AmGEO
  GEO Satellite

85
Generate Reports

• Generate AER and Link Budget-Detailed Reports
• Azimuth (deg) Elevation (deg) Range (km)
• 89.356 68.263
  36173.369418
• Xmtr Power (dBW) Xmtr Gain (dB) EIRP (dBW)
  
• 23.000 22.3760
  45.376
• Atmos Loss (dB) Rain Loss (dB) Prop Loss
  (dB)
• -0.0427 -1.6797
  -199.3173
• Tatmos (K) Tsun (K) Tantenna (K)
  Tequivalent (K)
• 2.868 0.448 474.953
  550.041
• g/T (dB/K) Eb/No (dB) BER
  
• 7.907484 12.5654
  9.349201e-010
• Indicates varying parameter due to sun effects

86
Generate Sun BER Graph
87
Evaluate Availability

• Change Maximum BER Constraint to 1.0e-6
• Examine Access and Gap Reports
• Gap Start Time (UTCG) Stop Time (UTCG)
  Duration
• 153223.88 154846.32
  982.434 (sec)
• Gap due to BER exceeding 1.0e-6 due to sun outage
• Compute range of antenna apertures using
  spreadsheet
• Compute the corresponding availability and outage
  times
• Note As the antenna aperture size increases, the
  beam width decreases as does the duration for
  which the sun is in the field of view of the
  antenna

88
Visualize the 3D Sun Interference

• 3D Graphics Attributes of ParabolicRcv Receiver
• Show Volume and Click on Details
• Frequency 5 GHz
• Gain Scale 100 km/dB
• Set Azimuth and Elevation Together
• Azimuth 0.2 deg and Elevation 0.2 deg
• Max Elevation Angle 15 deg
• 3D Graphics Vector of ParabolicRcv Receiver
• Add Quito Sun Vector
• Color Yellow Arrow Point Persistence
  Duration 1200 seconds
• Vector Size Scale 6.6

89
Dynamic Links and RF Interference

• Comm-System and Constellation Objects
• Evaluate Comm-System Performance among Multiple
  Nodes
• Include RF interference sources
• Dynamic Link from a Low-Earth-Orbiting (LEO)
  Satellite to a Ground Station
• In-Band interference from GEO
• Use Sensor as a Dynamic Pointing Platform for a
  Receiver

90
Low Earth Orbiting (LEO) Satellite

• Add LEO Satellite
• Circular orbit Semimajor axis 10560.3 km
• 75 deg inclined RAAN 154.296 deg mean anomaly
  0 deg
• LEOxmit Complex Source Transmitter
• Gaussian Antenna Type
• Data Rate 10 MBits/Sec Freq. 5 GHz Power
  18 dBW
• Beamwidth 45 deg Antenna Efficiency 55
• Antenna Gain Contour at -5 dB relative to maximum
• Compute Access from LEOxmit to MediumGatewayRcv

91
Constellations and CommSystem

• Create LEOdown Constellation
• Using LEOxmit Transmitter
• Create WashingtonRec Constellation
• Using MediumGatewayRcv Receiver
• Create LEO_IF Constellation
• Using GEOxmit transmitter
• Create LEOCommSys
• Transmit Constellation LEODown
• Receive Constellation WashingtonRec
• Disable Calculate Interference
• IF_Sources Constellation LEO_IF
• Compute LEOCommSys

92
BER Graph
BER BER I because Interference is disabled
93
Set GEO Interference
BER with Interference gt BER without Interference
94
Sensor Based Antenna

• Create WashingtonPoint Sensor on Washington
  Facility
• Complex Conic
• Inner Half Angle 0 deg Outer Half Angle 10
  deg
• Minimum Clock Angle 0 deg Maximum Clock Angle
  360 deg
• Targeted Pointing to LEO Satellite
• TwoMeterDish Complex Receiver
• Gaussian Type
• Diameter 2 m Antenna Efficiency 55
• Transmission Line Temperature 290 K Noise
  Figure 1
• Include Sun, Rain and Atmosphere in System
  Temperature
• Add TwoMeterDish to WashingtonRec Constellation
• Directivity of the antenna minimizes/eliminates
  RF interference outside the main lobe of the
  antenna pattern

95
BER and Interference
BER and the BER with interference are nearly
identical
96
Communications with a Satellite Constellation

• Communications to a Constellation of LEO
  satellites
• Evaluate Link Performance in the Presence of RF
  Interference
• Use Report Data to Set Subsequent Constraints and
  Attributes for Analysis
• Use Comm-System Analysis to Derive a Pointing
  Schedule for a Sensor
• Optimize Communications Performance
• Automate this Process Using Connect

97
Add a LEO Constellation

• Create a Walker Constellation Using LEO Satellite
• Number of Planes 5 Number of Satellites per
  Plane 5
• InterPlane Spacing 1
• Repoint WashingtonPoint Sensor to Constellation
• Add All LEOxmit Transmitters in Satellite
  Constellation to LEODown Constellation
• Recompute LEOCommSys

98
Link Information Report

• Examine Link Information Report for LEOCommSys
• The BER for the MediumGatewayRcv is generally
  low, but the BER with interference is not
• MediumGatewayRcv is omni-directional, so the GEO
  satellite contributes significant interference,
  which degrades the link performance.
• Use a Complex Receiver
• Receiver Must Be Actively Pointed for Mobile
  Transmitters
• BER for the TwoMeterDish Receiver for Many of the
  Accesses is High Due to Mis-pointing of the
  Receiver

99
Update Pointing

• Use the Link Information Report to Define Proper
  Pointing Targets and Schedule for the Sensor
  Platform
• Create a Custom Pointing Schedule for the
  WashingtonPoint Sensor in STK Object Browser
• In the Pointing Panel, Click on Target Time
• Deselect Use Access Times to Override the Default
  Pointing Targets
• Click on Add and Enter the Scheduled Times Based
  on the Link Information Report
• Process can be Automated by Using Connect

100
STK/Chains for Link Analysis

• Using Chains object
• Facilitate Availability Analyses Between LEO
  constellation and Ground Station
• Bit-Error-Rate (BER) Constraints on the
  Communication-Link Performance
• Evaluate Number of Available Accesses Between
  Constellation and Ground Station

101
Create Chain and Compute Availability

• Create and Build the LEOchain
• LEOdown Constellation
• MediumGatewayRcv Receiver
• Compute LEOchain
• Compute Complete Chain Access Report
• Note the 100 Availability Duration 43200
  seconds
• Washington Receiver Always Sees at Least One LEO
  Transmitter

102
Set BER Constraint

• Set Maximum BER Constraint for Receiver
• BER Constraint Duration Availability
• 1e-4 43200.0 100.0
• 1e-6 41737.9 96.6
• 1e-10 30624.1 70.9

103
End-to-End Communications Analysis

• Trans-Continental Link through LEO Relay
  Satellites
• Using Chains to Perform Link Analyses
• Retransmitter Object
• Models Transponder Links
• Modeling Relay Nodes
• Cross-Parent Coupling Between Constellations

104
Update Chain

• Los Angeles Facility
• MediumGatewayXmit Medium Source Transmitter
• Data Rate 10 MBits/Sec Freq. 5 GHz
• Power 28 dBW Gain 38 dB
• Add LEOrec Complex Receiver to LEO Satellite
• Gaussian Type
• Diameter 0.102939 m Antenna Efficiency 55
• Transmission Line Temperature 290 K Noise
  Figure 1
• Include Sun, Earth and Cosmic Background in
  System Temperature
• Replicate LEOrec Receiver for each Satellite in
  LEO_const Constellation

105
Update Chain (continued)

• Change LEOxmit to Complex Retransmitter
• Sat Flux Density -100 Sat Output Power 18
  dBW
• Diameter 0.102939 m Antenna Efficiency 55
• Replicate LEOxmit Retransmitter for each
  Satellite in LEO_const Constellation
• Create LEOup Constellation with One LEOrec
  Receiver
• Modify LEOdown Constellation to Have Only One
  LEOxmit Retransmitter
• Modify LEOchain
• MediumGatewayXmit transmitter on the Los Angeles
  facility
• LEOup receiver constellation
• LEOdown transmitter constellation
• MediumGatewayRcv receiver on the Washington
  facility

106
Bent Pipe Link

• Compute LEOchain
• Generate Bent Pipe Link Report and Bent Pipe BER
  Graph
• Note Differences in Link-Performance Parameters
  for the Uplink, Downlink and Aggregate
• e.g. BER for Uplink is very low BER for Downlink
  is high
• Composite BER is high

107
Bent Pipe Link BER
108
Update Constellation

• Modify LEOup Constellation to Include All LEOrec
  Receivers
• Modify LEOdown Constellation to Include All
  LEOxmit Retransmitters
• Recompute LEOchain
• Appearance of Crosslinks Illustrated in the
  Animations Even Though No Crosslinks Were
  Specified in the Chain Definition
• Disable Cross Parent Access for LEOdown
  Constellation
• Recompute LEOchain

109
LASER Link Analysis with STK/Communications
110
Laser Communications

• Models Free Space Laser Communications in the
  Near Infrared, Visual and Ultraviolet Bands
• Transmitted Laser Signal Properties
• Strong Signal
• Secure (Tamper Free)
• Large Bandwidth
• Highly Directional
• Facilitates Communications Laser Link Budget
  Analysis
• Contours, 3D Antenna Beam Patterns and
  Constraints are Unavailable at Present

111
Laser Source Transmitter Model

• Medium Source Transmitter Model with Additional
  Parameters
• Optics Area
• Optics Efficiency
• Gain Value is Queried First If Zero, Gain is
  Computed
• Gxmtr (4p A/l2)n
• A optics aperture area
• l laser wavelength c/f
• n optics efficiency

112
Laser Receiver Model

• Medium Receiver Model with Additional Parameters
• Laser Optics
• Optics Area
• Optics Efficiency
• Laser Detector
• Detector Area Detector Efficiency Detector
  Gain Detector Dark Current (Amps)
• Detector Noise Factor Detector Noise
  Temperature Load Impedance
• Parameters Used to Compute Signal-to-Noise Ratio
  and Eb/No for Laser Comm Link
• Receiver Gain Value, if Zero or Negative, is
  Computed
• Grcvr (4p A/l2)n
• A optics aperture area
• l laser wavelength c/f
• n optics efficiency
• Receiver Gain Value is Set to this Value for the
  Non-Tracking Receiver Types
• Auto-Tracking Receiver Type Gain Value is Checked
  at Each Time Step If Zero or Negative, Gain is
  Computed by Using Above Equation and the Doppler
  Shifted Frequency Received at that Instant

113
Laser Transmitter Parameters

• Geo_Sat1 GEO Satellite
• Long Asc Node 100 degrees W
• Transmit_Platform Sensor Targeted to Neighboring
  Geo_Sat2
• Laser Source Transmitter on Transmit_Platform
• Data Rate 1000 MBits/Sec
• Frequency 375000 GHz
• Power 0 dBW
• Gain 120 dB
• Optics Area 0.1 m2
• Optics Efficiency 70

114
Laser Receiver Parameters

• Geo_Sat2 GEO Satellite
• Long Asc Node 0 degrees
• Receive_Platform Sensor Targeted to Neighboring
  Geo_Sat1
• Laser Receiver on Receive_Platform
• Gain 60 dB System Temperature 290 K
• Detector Area 0.01 m2 Detector Efficiency
  90
• Detector Gain 60 dB Detector Noise Factor
  0.1 dB
• Detector Noise Temperature 10 K
• Detector Load Impedance 1.0e8

115
Laser Link Budget

• Xmtr Power (dBW) Xmtr Gain (dB) EIRP (dBW)
  
• 0.000 120.0
  120.0
• Atmos Loss (dB) Rain Loss (dB) Prop Loss(dB)
• 0.0000 0.0000
  -300.133
• Tatmos (K) Train (K) Tequivalent (K)
• 0.0 0.0 290.0
• g/T (dB/K) Eb/No (dB) BER
  
• 35.37602 42.4463 1.0e-025