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

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

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

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

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

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

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 www.agi.com

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. www.agi.com

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) www.agi.com

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) www.agi.com

Directivity Visualization Using STK Coverage

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

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

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

Questions?