EEsof Momentum Tutorial

Introduction


This exercise is designed to get you acquainted with the Agilent Technologies (formerly Hewlett Packard) EEsof Advanced Design System (ADS) software, and to reinforce the information on antenna design that we have been studying.  The exercise will more-or-less lead you through the software and should be all you need (the ADS user interface is great - very easy to use and 'Windows-like').  However, if you wish to learn more, all the manuals are on-line (choose 'help' after starting the program), and there is a Getting Started with Momentum manual in the lab (RA297).
 
 

Setting up Your Account

Before you can run the software, you will need a few things:

Environment Variables

You must tell the operating system and the program itself where they can find certain things. This can be done by adding the following lines to your '.tcshrc' file in your home directory. Note that  you will have to log out and back in, or invoke a new shell before these changes will take effect.

    # variables and path for EESOF RF design program
    setenv   HPEESOF_DIR   /usr/local/hp1.3
    setenv   LM_LICENSE_FILE   $HPEESOF_DIR/licenses/license.dat
    set path = ( $path   $HPEESOF_DIR/bin )
 
 

Running on the Sun Network

The EEsof ADS software that we have runs under the Solaris operating system on the department's Sun workstations ('fang' is the primary machine).  Up to 5 students can use it at once by logging in to one of the Linux workstations, "telnet'ing" to a remote Sun machine (e.g.  telnet fang), and then setting up the remote machine to send the display information back to the Linux box.  If you are not familiar with this process, click here for more info.
 
 

Overview of the Exercise

Our goal  is to draw a simple dipole antenna using the ADS  layout editor and then analyze it using the ADS electromagnetic simulation program "Momentum".  The program can show you the antenna impedance, the current distribution, and the far field patterns.  It can also compute many useful parameters such as the effective aperture, the efficiency, and the antenna gain.  (We will learn the schematic editor and circuit simulation portions of ADS in the next exercise.)
 
 

Starting the Program

Creating a New Project

Creating a Layout

We will be creating our antenna by drawing traces on a PC board.  In the layout editor, you can draw traces of various widths and lengths on various layers (like the top or bottom of a PC board).  We will use a single layer, and draw the following geometry:


 

To accomplish this, do the following:

Printing your Layout

You need to turn in a hardcopy of your layout.  To do this, use the following steps:
 

Simulating the Antenna with Momentum


Momentum is EEsof's electromagnetic simulator.  It solves Maxwell's field equations for 2.5 D layouts such as those encountered in circuit boards and ICs.  It can then show you the terminal impedance of your layout (antenna reactance and radiation resistance in our case), as well as the current flow on the metal traces, and the far field patterns.

The process of setting up and running the simulation and then viewing the results involves a sequence of steps:
 


The detailed steps you need to follow to accomplish this are shown below:
 

Examining the Results

There are many ways in which the results of an electromagnetic simulation can be examined.  The charts that come up at the end of the simulation show the port impedances, etc., but you can also look at the currents on the antenna, the fields produced by the antenna, and many important antenna characteristics such as the directivity/gain, effective area, and efficiency.  In this last section, we will take a tour of some of these features of the program.  You will also print out several items to prove that you got this far!
 

Deliverables


Turn in the printout of your layout and the printouts of the antenna impedance and 2D pattern data.  Also turn in a discussion of whether or not these data generated by the simulation is reasonable.  For example, does the impedance of the antenna agree with theory?  Does the antenna gain and effective areas match what you expected to see?