UNIFIED ELECTROMAGNETIC DESIGN SOFTWARE
Version 1.6
March 2004



Introduction

The Unified Electromagnetic (UEM) Design software is a tool for dealing with the effects of electromagnetic (EM) environments on systems. There are many diverse types of EM environments and effects, and they are all brought together in this software (hence, the term "Unified"). A major part of the software is a collection of key features from various EM standards, both military and commercial. In considering EM hardening of a system, the UEM Design software emphasizes an approach that protects against EM fields in general, not hardening individually for each separate effect (another reason for the term "Unified").

There are several aspects to this software. Partially it is like a textbook, discussing EM effects on systems, and how to protect against adverse EM effects. Some of the resulting computational models are interactive, in which the user can modify parameter values to tailor the results to the user's cases of interest. Part of the software also goes beyond this, allowing the EM design of the user's system to be inserted into the software for evaluation.

The UEM Design Software helps manage a program to build an EM hardened system. It provides guidance on what steps are needed in such a process. Its tools help select requirements that will allow the hardened system to be built. While it does have some computational ability, it does not provide detailed calculations of system responses in an EM environment.

Users Benefited by the UEM Design Software

The software would be useful to anyone interested in the possible adverse effects of electromagnetic environments on a system. This includes natural and man-made EM environments: hostile, essential (i.e., pulses from nearby radar), or inadvertent leakage from other systems or from within your own system. Thus, this includes, for example, selectors of system specifications, system designers, design evaluators, and those responsible for system safety and maintenance.
Systems of Concern for the UEM Design Software

Some systems will obviously need to have EM evaluations. This includes any electronic system, especially if it has antennas, or external, or long internal, cabling. Electronics are ubiquitous in newer systems. But other systems may be of concern also.

A typical system will have its vulnerable parts in subsystems, which will be protected by shielding enclosures. However, the protection provided by these enclosures will be compromised by various "penetrations". A significant penetration of concern is cables, which often are necessary if a system is to serve any useful purpose. Major system features modeled by the software are enclosures and cabling.

Vulnerabilities Addressed by the UEM Design Software

The chief worry is that the EM environments can induce extraneous signals in the system's circuitry. This can cause improper operations (upset), of various consequences and outage times, or be strong enough to cause permanent damage to the electronics (burn out parts). Some other worries include such things as ignition of rocket propellants or ordnance.
Tasks Helped by the UEM Design Software

Some of the tasks that might benefit from this UEM Design application include:

1.	System Specification: The software can help select environments, and specific EM environment specifications, that the system buyer will specify against the system.

2.	System Design: The software can help with many design tasks: development of the protection concept, determination of environment and immunity levels, allocation for barriers, and testing of the conceptual designs

3.	Hardness Assurance (HA) Program: A HA program examines EM protection design features during all phases of the manufacturing and production process to ensure compliance with engineering drawings, specifications, etc.

4.	Hardness Maintenance (HM) Program: A HM program provides instructions for preserving the EM protection design during operations, maintenance, logistics, and other support activities.

5.	Hardness Surveillance Program: This examines the fielded equipment to determine if the EM protection features have degraded. A second function of the HS program is to assess the HM program to determine if that program is adequate for maintaining the system.

UEM Design Software EM Environments

Some of the EM environments considered in this software are:
1.	Natural lightning
2.	Electrostatic discharge (ESD)
3.	Manmade, non-hostile radio frequency (RF) emissions, including electromagnetic environments (EME) and high intensity radiated fields (HIRF)
4.	High altitude electromagnetic pulse (HEMP)
5.	All classes of manmade, hostile radio frequency weapons (RFW), including high-power microwave (HPM) and ultra-wideband (UWB) weapons
6.	Out-of-band effects of electronic countermeasures (ECM)
7.	Precipitation Static (P-Static)

Source region electromagnetic pulse (SREMP) and the associated internal system generated electromagnetic pulse (SGEMP) are not included in this version.  
UEM Design Software Tools

This UEM Design software provides several useful computational tools. These tools may be categorized as:
1.	Equations
2.	Overlays and customize plots
3.	Transverse functions
4.	System analysis

The "Equations" provides the basis of some quantity, such as an environment, immunity, transfer function, etc. Often these are in the form of both a plot and also the underlying equation (or table). Most include various (user-selectable) forms, such as: time domain or frequency domain, electric field or magnetic field, voltage or current, field level or power density level, etc. Some have user-settable parameter values, with the values set by a slider or by keyboard entry. The user can select one of these, and then send a copy (using "Edit\Save As") of it to the "User Specified Quantities" section. Once there, all the parameters of the equation may be changed (using the "Equation" tab in the plot window). The software also has a set of generic functions, which the user can use to create his own quantity, such as environment or immunity level, by setting values for all the parameters. Thus, unlike a printed textbook, the results can be interactive.

In another interactive feature, the user can configure the plots. A useful option is overlay plots. The user can select several quantities to appear together on the same plot, so they may be compared. The user also has some control over the appearance of plots (i.e., can change titles, etc.), by using the tabs in the chart window.

The various parts of the UEM Design software have quantities that actually are interconnected, in a sequential way. An external EM field couples to a cable, and this signal interacts with the internal circuitry, which causes an upset. This can be represented by:
Environment (EM field)  Transfer function (coupling)  Immunity (circuit upset)
The UEM Design software allows the user to make such connections within the software also. A transfer function or margin can be applied to an environment or immunity standard. This is done simply by accessing them in the proper order.

A final tool is in the "System Analysis" section. It is explained in the "Doing a System Analysis" section, later in this introduction.

UEM Design Software System Approach

Each of these various tools may be used individually. However, a major use of this software, which brings together all these tools, is the design, building, and maintaining of a system immune to adverse EM effects. Part of the software provides a guide to such a task. It is based on a specific hardening philosophy, involving barriers. Vulnerable sections of the system are separated from harmful EM environments by barriers, in either a single layer or multiple layers. The barriers are composed of fully enclosing shields, with protection devices on any penetrations, which, for electrical or mechanical reasons, go through the shield enclosure.

Using the UEM Design Software

The UEM Design software has a built-in ("online") discussion on using the software. (It is the "Unified EM Overview\Unified EM Design Software" section. Use the "Help\On-line" menu item, which is available when the text window is active, to directly jump to the "Unified EM Overview" section.) Here we'll briefly introduce use of the software.

The software starts with a two-panel window. The left side has the table of contents (the "tree"). Sections of it can be expanded (+) or contracted (-) by using the little boxed + or - to the left of each entry (with a left mouse click on the small box). Selecting an entry (left mouse click) brings up the corresponding text in the right panel. This will be scrollable if it is too big to fit. Some entries also have associated charts, which will show up in a second window. These two windows have the normal options - they may be minimized, cascaded, tiled, etc. A handy mode of viewing is to make the UEM Design overall window big (either full screen, or close to it), get the two windows showing, and then select the "Window\Tile" menu item.

The displays can be printed, using the "File\Print" menu item. They can also be copied, for insertion into another application. For the text window, use "Ctrl-A" to highlight the full text (or highlight some smaller part of it), and then hit "Ctrl-C". Then use "Paste" (often "Ctrl-V") in the application to get it. For the chart (plot) window, be sure it is active (its title bar is blue), and then hit "Ctrl-C" (or use the "Edit\Copy" menu item). Then there are two options for retrieving it. In Word, for example, using "Paste" (or Ctrl-V") will insert a table of the plot values. To get the actual plot, use "Edit\Paste Special\Picture".

Making overlay plots is fairly simple ("overlays" plot several functions in the same chart). Whenever you see a plot that you want in overlay, simply hit the "Overlay" button. When you go to a new plot, all previously selected overlays will also be shown. To clear out the set of overlays, hit the "Single Plot" button. Note that overlays will not work well if the axes, both vertical and horizontal, are not compatible for the various overlays.

A similar technique is used for sequential connecting of various quantities. For example, we can see the effect of connecting an environment or immunity standard to a transfer function or margin. To do this, simply look at the environment (for example) first, and then go and look at a transfer function (for example).  If the two are compatible, then the display will combine the two, as will be obvious from the chart title and vertical axis label.  To undo this connection, and look at a plot of only the transfer function, hit the "Single Plot" button.

The next section explains a system analysis, in which the user puts in a system design and does a hardness analysis of it.

Doing a System Analysis

Analyzing a system design is discussed in "Unified EM Overview\Unified EM Design Software"; here we will just briefly summarize this aspect of the software.

This analysis tool helps decide on the level of protection needed for the system. The user inserts details of the system: the system structure (topology), the EM environments it must withstand, and the vulnerabilities (as "immunities" level) of its sensitive subsystems. Then the "System Analysis" feature of the software determines how much the environments must be reduced to protect the system, that is, how much shielding is needed.

The basic steps involved are:

1.	Open a system of concern: If the system doesn't exist in the UEM Design software yet, select a type in the "System Analysis" section (it doesn't actually matter what type), and select the "File\New" menu item, or right click and select "New"; then give the system a name. The new system will be added into the tree, under the selected system type. It can, as can any existing systems, then be opened by left clicking it, and then right clicking it and selecting "Open" (or using the "File\Open" menu item).

2.	Define the Topology: This step specifies the enclosures and subsystems. There may be enclosures around other enclosures, and around subsystems. Select "Topology\ Enclosures" in the system tree, and then the "Topology\Add\Enclosure" (or "Subsystem") to add one of these at the outer-most level (so it usually wouldn't be a subsystem). Then, to put an enclosure or subsystem inside this outer one, do the same, but select the outer enclosure in the tree first.

We also need to specify all the pertinent cabling, which runs from where it ends at the subsystems, to other subsystems, or out, through enclosure walls, to other places. Some cabling often goes outside the system itself - these external cables are often the biggest hardness concerns. To add cables, select an enclosure or subsystem, and use the "Topology\Add\Penetrations" menu item. Make sure that the cables are connected up properly.   

3.	Define the environments: Specifying EM environments is very easy. You need to have the desired environment selected in the main UEM Design window, and the system analysis opened for the system of concern (you can "tile" these two windows). Select the desired environment by left clicking it in the tree (so its text, not its chart, is the active window), and select the "Edit\Copy Standard" menu item (or right click on it and then select "Copy Standard". Then go to the system tree, and left click the "Environments" item. Then select the "Define\Environments" menu item. Make sure to have a full set of environments: for each type (radiated and conducted), there are transient and narrowband types.

4.	Define the cable coupling: Each cable in the system can couple to the EM environment. This coupling is specified by "Transfer Functions," which depends on the properties of the cable, such as its length. There are several generic coupling models (transfer functions) in the UEM Design software. These convert an EM field into a cable current. To specify these, select the appropriate transfer function (an existing UEM Design one, or a user specified one) and do a "Copy Standard". Then select the appropriate port in the system design, and do a "Define\Transfer Function".

5.	Define the subsystem vulnerabilities: Immunities are added the same way. Select one in the main UEM Design tree, and do a "Copy Standard". Then select "Immunities" in the system tree, and do a "Define\Immunities" menu item. You then can select which subsystems will have that immunity. Where the immunity gets applied (transient/narrowband and enclosure/cabling) is set by where it originated. However, note that it must be in the proper form: enclosures use EM field immunities, and cabling ports (i.e., "conducted") use currents (all in the frequency domain). If the selected immunity is in the wrong form, you must use a transfer function to convert it first. Make sure to have a full set of immunities: for each type, radiated and conducted, there are transient and narrowband types (which can be identical functions).

6.	Define the safety margin: You also should specify safety margins, which scale the immunities lower by the selected amount. A single margin for the whole system can be easily set by selecting the level in the main UEM Design "Margin" section, doing a "Copy Standard," selecting "Margins" in the system tree, and hitting the "Define\Margins" menu item. To set the margin for a given subsystem, select it instead of the "Margin" item before doing the "Define\Margin".

7.	Do the analysis: The analysis is done by the steps in the "Processing" menu of the system analysis window. The last one, "Report", is the most important. Its output can be seen by selecting "Allocation Processing\Report" in the system analysis tree, but also exists as a RTF (Rich Text Format) file that can be imported into a word processor. The basic results of the analysis are frequency domain plots of shielding levels needed for various parts of the system.

Outline of the UEM Design Software

There are seven sections to the software:
1.	Environments
2.	Immunities
3.	Margins
4.	Transfer Functions
5.	User Specified Quantities
6.	Unified EM Overview
7.	System Analysis

There is some general discussion in the "Environments" section, but most of it is composed of various EM standards. These are divided into "External" and "Internal" sections. Within each, there are three sections: "Electronic Operation" (resulting from the normal operating of electronic equipment), "Hostile", and "Natural". Under these are listed the appropriate types of EM environments. There may be further divisions in the organization of the standards presented, such as military/commercial, radiated/conducted, and different equipment types. There are plots of most results, and these may have optional forms (time/frequency domain, electric/magnetic, etc.), and user-selectable parameters. This is the second largest section of the software.

The "Immunities" section is the largest section of the software. It presents standards for the EM levels that systems are designed to withstand. Each result is presented at least twice, since they are organized two ways: first all are organized by port type (enclosure, AC power, DC power, signal & control, antenna). Within these, they are further organized by military/commercial, and then by groupings such as transient/narrowband. They appear again in an organization that gives first the military standards, then the commercial standards. As for environments, these usually have plots, which can have optional forms, and may also have user-defined parameters.

The "Margins" section is very short, since, basically, the system designer simply has to decide on what level of safety margin to use.

The "Transfer Functions" section deals with interaction (i.e. coupling and leakage) of EM field environments with a system. These are organized by system structure type: external long lines (like power and communications lines), antennas, enclosures, local AC power lines, DC power lines, and signal and control lines. As stated, by selecting one of these after viewing an environment, the software shows the effect of applying the transfer function to the environment, if the two are compatible.

Under the "User Specified Quantities" section we are allowed to add to the software: environments, immunities, or transfer functions. We are first told how this is done, either by copying and modifying an existing one, or by working from one in a list of generic forms. Once added, these quantities may be used just like the ones built into the software.

The "Unified EM Overview" has three parts. First it has a three section tutorial on hardening a system. Next, there is "Unified EM Design Software", which explains how to use this software. The "On-line" "Help" menu selection transfers you down to this section. You may find it helpful to go through this section after experimenting with the software a little. Finally, there is section with a listing of references.

The last section, "System Analysis", allows the user to enter in a system for EM hardening analysis (as discussed in "Doing a System Analysis").

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Copyright 2004, Mission Research Corporation, WDC, USA.