1. STK 3D Electronically Steerable Phased Array Antenna Plugin
Trey Spetch, Jerry Odhner, and Kristen Jones

2. What is a 3D Steerable Phased Array Antenna?
Flat Panel Array of Elements
Beam Electronically Steered by Varying Phase Across Elements
Steerable in Both Azimuth and Elevation

3. Applications of Electronically Steerable Flat Panel Arrays
Over the Horizon Radar
Missile Searching and Tracking (Patriot Missile)
Ship-Borne Radar
Aircraft Antennas
Must be conformal with aircraft
No dishes allowed
Large apertures achievable

4. STK Static Antenna Patterns Not Suitable to Model Phased Array Beam
90 Degree Elevation Beams 45 Degree Elevation Beams
1 GHz, 1m Aperture 1 GHz, 1m Aperture
Array Antenna Dish Antenna Array Antenna Dish Antenna

5. Antenna Notional Model
Crossed-Dipole Element
n = 3
l/2

6. Dihedral Angles to Boresight and ToObject
Dihedral Angles for Boresight (f, q) and ToObject (a, b)

7. Plugin Model G(m, n, l, q, f, a, b) Coord Xform ToObjectAz b
AGI User's Conference
October 2005
Plugin Model
Coord
Xform
ToObjectAz b
ToObjectEl a
m, n, l
G(m, n, l, q, f, a, b)
GainToObject
OUTPUT:
The Gain at a specific angle (in Az/El). The STK executes the plugin over a range out input angles to generate the gain over a hemisphere.
CONVERT/CALC:
Transform Az/El to dihedrals angles and use Jerry’s equations
INPUT:
Az/El basic input values: come automatically with plug-in
M, N, and Wavelength: properties of the array. Can be hard-coded into the plug-in but we pass these values since we dynamically drive this from Connect and change the values between runs.
Boresight angles: steering varies over course of scenario so we use custom angles built in vector geometry tool (example follows)
BoresightHoriz q
BoresightVert f

8. Beam Steered to Invisible Vehicle
AGI User's Conference
October 2005
Beam Steered to Invisible Vehicle
To control the steering we created a “Steer to” vehicle (invisible in our scenario) and a vector (“steeredBoresight”) which points to it.
Dihedral angles are derived from this vector in the Vector Geometry Tool
This (invisible) vehicle can be made to move smoothly along its path OR, in our case, jump around using timed waypoints.

9. Creating and Attaching Plugin Scripts
AGI User's Conference
October 2005
Creating and Attaching Plugin Scripts
There are several kinds of plugins (constraints, transmitter and receiver models, custom antenna gain, etc)
For a custom antenna gain plugin, select the plugin file on the receiver properties panel under Antenna… Details…
Languages: Matlab, Perl, and VBScript.
The examples scripts that AGI provides are a good place to start. You can then add any additional input variables as needed and write functions to do custom calculations.
Examples provided for each plugin type in each language. Start here and modify them.
Speed differences are substantial. Originally done in Matlab which called JAVA code – easy to debug but very slow. Currently in VBScript – speedy.
Custom antenna gain plugin scripts come with several predefined input parameters (antenna position lat/lon/alt, azimuth, elevation…) and certain output parameters (gain, maxgain, beamwidth, integratedGain)
Virtually anything created in the Vector Geometry Tool can be passed in and used in your plugin.
You but register these (additional) input parameters (as I did with n, m, and the dihedral angles)

10. Plugin Code AntennaGainPlugin.vbs.doc AGI User's Conference
October 2005
Plugin Code
AntennaGainPlugin.vbs.doc
Registering inputs
Main functions = Jerry’s equations
Return Value(s)

11. Directivity Visualization Using STK Coverage

12. Effect of Changing Array Dimensions
Increasing the number of elements along one axis of the antenna decreases the beamwidth in that direction
5 x 5 Array, 1 GHz
5 x 10 Array, 1 GHz
10 x 10 Array, 1 GHz

13. Effects of Wavelength
For a given panel aperture size, the beamwidth decreases with wavelength
1 meter array (2x2), 500 MHz
1 meter array (7x7), 1 GHz
1 meter array (33x33), 5 GHz

14. Conclusion
STK Plugins allow dynamic beam shaping for antennas based on custom equations
Any geometric variable or scalar value can be input to the plugin
Allows extremely accurate modeling of link margins for phased arrays and other custom antennas

15. Questions?