Analyzer and the Multifunction Radar Object

STK Premium (Air), STK Premium (Space), or STK Enterprise
You can obtain the necessary licenses for this tutorial by contacting AGI Support at support@agi.com or 1-800-924-7244.

Additional installation - Analyzer. You can obtain the necessary install by visiting http://support.agi.com/downloads or calling AGI support.

The results of the tutorial may vary depending on the user settings and data enabled (online operations, terrain server, dynamic Earth data, etc.). It is acceptable to have different results.

Capabilities covered

This lesson covers the following STK Capabilities:

  • STK Pro
  • Radar
  • STK Analyzer

Problem statement

Engineers and operators have radars that track multiple target types. They need a quick way to determine how various settings on the radar will affect its ability to track the targets. In this scenario, an aircraft leaves an airbase in Spain and flies to an airbase in Italy. The radar site located at an Italian airbase is employing a new multifunction radar (MFR) which will track the inbound aircraft. Terrain is accounted for analytically in the vicinity of the radar site.

You need to know how the following will affect the multifunction radar's ability to track the aircraft:

  • Gain
  • Signal to noise ratio (SNR)
  • Pulse integration

Solution

Use STK and STK's Analyzer capability to perform four separate trade studies to examine various input variables and how they affect a multifunction radar's tracking of an aircraft.

What you will learn

Upon completion of this tutorial, you will have a basic understanding of the following:

  • Analyzer parametric studies
  • Analyzer carpet plots
  • How Gain, SNR, and Pulses Integrated affect Integrated PDet (probability of detection)

Starter scenario

To speed things up and allow you to focus on the portion of this exercise that teaches you how to use Analyzer and Aviator, a partially created scenario has been provided for you.

You should complete the Level 3 - Focused Feature Specific tutorial Introduction to STK's Multifunction Radar prior to beginning this lesson in order to understand STK's multifunction radar properties and settings.

  1. Launch STK ().
  2. Click Open a Scenario () in the Welcome to STK Window.
  3. Browse to <STK install folder>\Data\Resources\stktraining\VDFs\.
  4. Select MFR_Analyzer_Starter.vdf.
  5. Click Open.

Save a VDF as a SC File

When you save a scenario in STK, it will save in the format in which it originated. In other words, if you open a VDF, the default save format will be a VDF (.vdf). The same is true for a scenario file (*.sc). If you want to save a VDF as a SC file (or vice-versa), you must change the file format when you are performing the Save As procedure.

  1. Open the File menu.
  2. Select Save As.
  3. Click STK User.
  4. Select the MFR_Analyzer_Starter folder.
  5. Click Open.
  6. Change Save as type: to Scenario Files (*.sc).
  7. Click Save .
  8. Click Yes to Replace exiting file.

Save often!

Obtain situational awareness

There are three windows used in this scenario. Use STK's 3D and 2D Graphics windows to visualize and understand the aircraft flight plan.

  1. Look at the Aircraft - 3D Graphics Window which is zoomed to the aircraft ().
  2. Use your mouse to get an idea of where the aircraft is located and the airbase from which it just left.

    3. 3D Graphics View of the Aircraft Leaving the Spanish Airbase

  3. Click Start () in the Animation Toolbar to obtain situational awareness of the aircraft's location.
  4. Adjust (, )the step size as desired.
  5. When finished, Reset () the scenario.

    6. The aircraft is using a constant radar cross section value of 20 dBsm which is a good generic value for a large airliner.

  6. Look at the Radar Site - 3D Graphics Window which is zoomed to the radar site (). Radar_Site () and MFR () are both using an Az-El Mask constraint that takes into account the surrounding terrain.

    7. 3D Graphics View of the Radar Site and Surrounding Terrain

  7. Look at the Flight Plan - 2D Graphics Window to obtain the overall view of the aircraft flight plan.
  8. Note the box in northern Italy. The box is a visual representation of the analytical terrain boundaries. Everything outside the box is using WGS84 and everything inside the box uses analytical terrain.

2D Graphics View of the Aircraft's Flight Plan

Radar properties

Prior to running any trade studies, you should understand the MFR settings. STK's Radar capability provides thorough analysis and graphic displays of radar systems. It adds a new radar object that can be attached to an STK vehicle, facility, place, target, or sensor.

  1. Open MFR's () properties ().
  2. On the Basic - Definition page, view Beam ID TargetTransport.
  3. Note the TargetTransport beam is targeting the aircraft.
  4. Note the Gain value of 30 dB. We will analyze this in Analyzer.

Waveform strategy

Normally, you would want to use the Range setting for any target being tracked at different ranges. You are starting with a waveform strategy created for this analysis that is similar to the medium range rectangular strategy.

  1. Select the Waveform sub-tab on the Beams tab. Note that the Waveform is set to MFR Analyzer Waveform.
  2. Open the Utilities menu.
  3. Select Component Browser ().
  4. Open the Show Component Type shortcut menu.
  5. Select Radar Components.
  6. Select Radar Waveforms.
  7. Double click the MFR Analyzer Waveform in the Radar Waveforms list.
  8. Look at the settings.
  9. Click Cancel when finished.
  10. Close the Components Browser.

Detection processing

Detection processing allows you to define probability of detection, pulse integration and pulse specifications.

  1. Return to MFR's () properties ().
  2. Select the Detection Processing tab.
  3. Select the Pulse Integration sub-tab.
  4. Look at the SNR and Maximum Pulses values. Goal SNR and Maximum Pulses will be studied using Analyzer.
  5. Click Cancel to close MFR's () Properties Browser without accepting any changes.

Radar access

Create an access between the radar and the aircraft. This is required prior to using the Report & Graph Manager and Analyzer.

  1. Right click on MFR () in the Object Browser.
  2. Select Access... ().
  3. When the Access Tool opens, select Aircraft () in the associated objects list.
  4. Click .
  5. Click Report & Graph Manager... below the Reports frame.

Create a custom report

Create a custom report that provides pertinent data that will be analyzed when running the trade studies. The focus of this scenario will be integrated PDet. An integrated PDet value of 0.8 to 1.0 is required to track the aircraft with certainty.

  1. When the Report & Graph Manager opens, right-click on the MFR_Analyzer_Starter Styles () folder in the Styles frame.
  2. Select New in the shortcut menu.
  3. Select Report () in the second shortcut menu.
  4. Type Trade Study Data while in rename mode.
  5. Press Enter on your keyboard. You can also select the report and then click Properties (). This will open the Report Style - Trade Study Data Content properties.

Report content properties

You can define the contents and format of a new report style or modify the contents and format of an existing style. The properties available for defining the content and format of data will depend on the data providers in the selected report style. In this scenario, you are creating a custom report that contains elements of your choosing.

  1. When the Properties Browser opens, select the Content page.
  2. Remove the asterisk (*) in the Filter field.
  3. Type Radar in the Filter field.
  4. Click Filter.
  5. Expand () the Radar Multifunction () group in the Data Providers list.
  6. Expand () the TargetTransport () data provider.

    7. Any beams that are added to the Beams list in the Radar () object's properties will become a data provider under Radar Multifunction. TargetTransport is the default beam for this scenario.

  7. Move () the following elements to the Report Contents field in the order shown:
    Data Element
    Time
    S/T Integrated SNR
    S/T Integrated PDet
    S/T Pulses Integrated
  8. Click OK to accept the changes and to close the Properties Browser.

Generate the report

  1. Select Trade Study Data () in the MFR_Analyzer_Starter Styles () folder.
  2. Click Generate... ..
  3. Click Show Step Value at the top of the report.
  4. Change Step: to 10 sec.
  5. Click Refresh (F5) () in the report toolbar.
  6. Scroll through the report until you find the first time S/T Integrated PDet is at or above 0.8.
  7. Determine how long the radar tracks the aircraft (approximately nine (9) minutes).
  8. Look at the changes in S/T Integrated SNR (dB) and S/T Pulses Integrated throughout the report. As the S/T Integrated PDet improves, S/T Integrated SNR (dB) increases and S/T Pulses Integrated decreases.
  9. Right click on the time when the S/T Integrated PDet is first at or above 0.8.
  10. Select Time in the shortcut menu.
  11. Select Set Animation Time in the second shortcut menu.

Obtain situational awareness

  1. Bring the Radar Site 3D Graphics window to the front.
  2. Use your mouse to obtain a good view of the radar site and the beam pointing at the aircraft. Maximum gain is blue and minimum gain is red.

    3. Radar Beam Tracking the Aircraft

  3. When finished, close the report, the Report & Graph Manager and the Access Tool.
  4. Save () the scenario.

Analyzer

Analyzer provides a set of analysis tools that:

  • Enable you to understand the design space of your systems
  • Enable you to perform analyses in STK easily without involving programming or scripting
  • Introduce trade study and post-processing capabilities
  • Can be used with all STK scenarios, including those with STK Astrogator satellites

Determine the impacts of gain

In the first trade study, you will vary gain and determine its affect on S/T Integrated PDet. Antenna gain indicates how strong a signal an antenna can send or receive in a specified direction.

First, you need to select input and output variables from the main Analyzer window to pass to the Parametric Study tool.

  1. The Analyzer Toolbar should already be visible. However, If required, open the View menu, select Toolbars, then select Analyzer.
  2. Click Analyzer... () on the Analyzer Toolbar.

Another way of opening Analyzer is to extend the Analysis menu, extend Analyzer and select Analyzer. One more way opening Analyzer is to go to the Object Browser, right click on the scenario object (or any object), select the object's Plugins, and click STK Analyzer.

STK Variables

The MFR () is the variable required for your trade study.

  1. Expand () Radar_Site () In the STK Variables list.
  2. Select MFR ().

STK Property Variables

Select Gain for your first trade study.

  1. Select the General tab in the STK Property Variables list.
  2. Expand () Multifunction ().
  3. Expand () Beams ().
  4. Expand () TargetTransport ().
  5. Double click on Gain (). This moves it to the Analyzer Variables list as an input.

Data Provider Variables

The same data providers that are in the Report & Graph Manager are available in the Data Provider Variables list.

  1. Expand () Access () in the STK Variables list.
  2. Select Place-Radar_Site-Radar-MFR-to-Aircraft-Aircraft ().
  3. Select the Show all data providers check box below the Data Provider Variables list.
  4. Expand () Radar Multifunction ().
  5. Expand () Target Transport ().
  6. Expand () S/T Integrated PDet ().
  7. Double-click on Mean. This moves it to the Analyzer Variables list as an output.

    8. You will always have a maximum probability of detection value of 1. Minimum values change slightly. You can get a better idea of how changing gain impacts the mean value of the probability of detection. You will use the mean value for all of the trade studies.

Parametric Study Tool

Use the Parametric Study Tool to run a model through a sweep of values for an input variable. The resulting data can be plotted to view trends. To perform a Parametric Study, one design variable and one or more responses must be specified. For the design variable, a starting value, ending value, and number of steps must also be specified.

The current gain is 30 dB. For the purposes of this trade study, vary the gain from 20 dB to 40 dB in 2 dB increments. 11 runs (scenario changes) will be required to analyze your variable.

  1. Click Parametric Study... () on the Analyzer toolbar to open the Parametric Study tool.
  2. Drag Gain () from the Components list to the Design Variable () field.
  3. Set the following Design Variables:
    4. Option Value
    starting value: 20
    ending value: 40
    step size: 2

Set the response

  1. Drag Mean from the Components list to the Responses list.
  2. Click Run... .
  3. When the Parametric study is finished, close the 2D Scatter Plot.

Data Explorer

The Data Explorer is a tool used by Trade Study tools to display data while they are being collected from STK. While data is being collected, the Data Explorer displays a progress meter, a halt button, and the data.

Table Page

The Table page displays trade study data in a tabular form. It is the default window that is present for all trade studies. Cells are shaded differently depending on the associated variable's state. Input variables are shown with green text, valid values are displayed with black text, invalid values are displayed with gray text, and modified values are displayed with blue text. From the table it is possible to view and edit all values in your trade study and even to add and remove whole runs.

  1. Look at the Table.
  2. Notice the first line shows gain from lowest to highest, in 2 dB increments.
  3. Notice the second line shows mean integrated probability of detection.

    4. The assumption is that the higher the mean value, the further out you may be able to track the aircraft. Remember, a gain of 30 dB is the current setting for the radar beam.

2D Line Plot

There are multiple views that can be selected to visualize the data seen on the Table Page. You can choose views by clicking on Add View on the Data Explorer Toolbar.

  1. Open the Add View shortcut menu on the Table Page Toolbar.
  2. Select 2D Line plot.
  3. On the 2D Line plot, click Axes to the left of the plot.
  4. Select the Ticks tab in the Axes dialog box.
  5. Set the Max # value to 20.
  6. Click anywhere on the plot to close the Axes menu.

    7. Gain Parametric Study

    You can see from the study that the mean S/T Integrated PDet has a slight increase from a gain of 20 dB through 30 dB. However, from 30 dB through 40 dB there is a steeper climb.

  7. Close the 2D Line Plot and the Table Page.
  8. Click No when the Save window appears.
  9. Close the Parametric Study.
  10. Return to Analyzer.

Goal Signal to Noise Ratio (SNR)

Goal SNR is an integration analysis based on the desired signal-to-noise ratio. SNR is a measure that compares the level of a desired signal to the level of noise. The default value is 16 dB. Study how SNR affects the mean value of integrated probability of detection.

STK Variables

Select your variable.

  1. Expand () Radar_Site () in the STK Variables list.
  2. Select MFR ().

STK Property Variables

Select SNR for your next trade study.

  1. Select the General tab in the STK Property Variables frame.
  2. Expand () Multifunction ().
  3. Expand () DetectionProcessing ().
  4. Expand () PulseIntegration ().
  5. Expand () GoalSNR ().
  6. Double-click on SNR (). This moves it to the Analyzer Variables list as an input.

Parametric Study Tool

  1. Click Parametric Study... () on the Analyzer toolbar to open the Parametric Study tool.
  2. Drag SNR () from the Components list to the Design Variable () field.
  3. Set the following Design Variables:
    4. Option Value
    starting value: 10
    ending value: 22
    step size: 1

Set the response

  1. Drag Mean from the Components list to the Responses list.
  2. Click Run... .
  3. When the Parametric study is finished, close the 2D Scatter Plot.

2D Line Plot

  1. Open the Add View shortcut menu on the Table Page toolbar.
  2. Select 2D Line plot.
  3. Click Axes.
  4. Select the Ticks tab in the Axes dialog box.
  5. Set the Max # value to 20.
  6. Click anywhere on the plot to close the Axes menu.

    7. Goal SNR Parametric Study

    If you looking for a specific SNR, you can see that there is a steady S/T Integrated PDet mean increase until you reach 20 dBW. At that level, it begins to taper off.

  7. Close the 2D Line Plot and the Table Page.
  8. Click No when the Save window appears.
  9. Close the Parametric Study.
  10. Return to Analyzer.

Maximum Pulses

Pulse integration is a improvement technique to address gains in probability of detection by using multiple transmit pulses. When a target is located within the radar beam during a single scan, it may reflect several pulses. By adding the returns from all pulses returned by a given target during a single scan, the radar sensitivity SNR can be increased. Most radars have a fixed number of pulses.

STK Variables

  1. Expand () Radar_Site () in the STK Variables list.
  2. Select MFR ().

STK Property Variables

Select MaximumPulses for you next trade study.

  1. Select the General tab in the STK Property Variables frame.
  2. Expand () Multifunction ().
  3. Expand () DetectionProcessing ().
  4. Expand () PulseIntegration ().
  5. Expand () GoalSNR ().
  6. Double-click on MaximumPulses (). This moves it to the Analyzer Variables list as an input.

Parametric Study Tool

  1. Click Parametric Study... () on the Analyzer toolbar to open the Parametric Study tool.
  2. Drag MaximumPulses from the Components list to the Design Variable () field.

    3. Depending on an actual radar, there could be a limited number of pulses. STK defaults to 512.

  3. Set the following Design Variables:
    4. Option Value
    starting value: 1
    ending value: 200
    step size: 10

Set the response

  1. Drag Mean from the Components list to the Responses list.
  2. Click Run... .
  3. When the Parametric study is finished, close the 2D Scatter Plot.

2D Line Plot

  1. Open the Add View shortcut menu on the Table Page tool bar.
  2. Select 2D Line plot.

    3. Pulses Integrated Parametric Study

    In this instance, the mean integrated probability of detection has a sharp rise until 50 pulses integrated, after which it begins to level off.

  3. Close the 2D Line Plot and the Table Page.
  4. Click No when the Save window appears.
  5. Close the Parametric Study.
  6. Return to Analyzer.

Carpet Plot Tool

A Carpet Plot is a means of displaying data dependent on two variables in a format that makes interpretation easier than normal multiple curve plots. A Carpet Plot can be thought of as a multi-dimensional Parametric Study.

  1. Click Carpet Plot... () on the Analyzer toolbar to open the Carpet Plot Tool.
  2. Drag Gain () from the Components list to the first Design Variable () field.
  3. Drag SNR () from the Components list to the second Design Variable () field.
  4. Set the following Gain Design Variables:
    5. Option Value
    From 20
    To 40
    Step Size 5
  5. Set the following SNR Design Variables:
    6. Option Value
    From 10
    To 20
    Step Size 2

Set the response

  1. Drag Mean from the Components list to the Responses list.
  2. Click Run... .

Carpet Plot

Search for a specific integrated PDet

In this study, you're looking for a gain and SNR combination that provide an S/T Integrated PDet mean value of 0.4. Use the Axes tab to set options for the axes.

  1. Click Axes .
  2. Select the Ticks tab in the Axes dialog box.
  3. Set the Max # value to 20.
  4. Click anywhere on the plot to close the Axes menu.

Constraints Tab

Constraints allow you to specify the constraints to display on your graph.

  1. Click Constraints .
  2. Set the following minimum values (boxes on the left) in the Constraints dialog box:
    3. Option Value
    Gain 36
    SNR 13.7
    Mean 0.4
  3. When finished, click anywhere on the plot to close the Constraints menu.

    4. You can see how the shading in the plot merge at an Integrated PDet of 0.4 when Gain is 36 dB and SNR is 13.7 dBW. You could have used the constraints dialog and the slider bars to find the settings. The shading makes it easier to read the plot.

    Mean vs SNR vs Gain

  4. When finished, close the Carpet Plot and the Table Page.
  5. Click No when the Save window appears.
  6. Close the Carpet Plot Tool.
  7. Close Analyzer.

Summary

You began by determining how long the multifunction radar could track an aircraft based on a S/T Integrated PDet mean value of 0.8 or higher. Using Analyzer you ran three (3) different Parametric studies determining how gain, SNR and pulses integrated affect the mean value of S/T Integrated PDet. Finally, using the Carpet Plot Tool, you determined which combination of gain and SNR provided a S/T Integrated PDet mean value of 0.4.

Save Your Work

  1. Save () your work.

On Your Own

You could rerun all the Parametric studies using new values with the existing input variables. To make things very interesting, you could go into MFR's Multifunction STK Property Variables, open the various inputs, and try new inputs to see how they affect the mean S/T Integrated PDet . If you look at the Access Data Provider Variables, Radar Multifunction/TargetTransport has many more variables. You could run trade studies against them. Explore and have fun.