UNIVERSITY OF UTAH ELECTRICAL ENGINEERING DEPARTMENT ECE 5320 LABORATORY #1 Autumn 2004 USING AGILENT ADS (ADVANCED DEVELOPMENT SYSTEM) ANDTHE HP 8720 NETWORK ANALYZER Introduction ADS is Agilent's latest integrated system of software applications for analysis and design of microwave circuits. We greatly appreciate Agilent's donation of this software to our microwave engineering program for student use. ADS contains the latest state-of-the-art computer programs required for sophisticated design work. During this semester, we will learn how to use a portion of the software tools that analyze linear, passive microstrip circuits, and make swept plots of the reflection and transmission versus frequency. You will also learn how to use the graphics tools which output masks for microstrip photographic processing. Next semester, and beyond, you will use additional tools to analyze active circuits which contain transistors and diodes. Models of all these elements are contained in ADS, and circuits composed of these elements can be assembled together in this new software by simple "drag & drop" operations on the GUI interface. We worry about making the analysis & design process so easy that you (the student) fail to learn the underlying scientific principles and physical processes related to our subject. Our philosophy in EE 5320 will be that hand (or MATLAB) calculations in the beginning using the underlying theory followed by ADS analysis of the same (or similar) circuits will suffice to ground students in the underlying principles. Beyond this, it is up to you to make sure that you do not abuse these tools by trusting them too much and thinking too little about the results you obtain. Always try to understand your analysis outputs in terms of the physical properties of the circuit elements. As the frequency sweeps, make sure that you understand the behavior versus frequency and any resonant points where reflection or transmission peaks occur. This will help you learn microwave engineering while also learning how to use the professional tools you will see on the job. The HP 8720 Network Analyzers (NA) used in the labs are also donated by Hewlett-Packard. These state-of-the-art instruments are of the type that you will see on the job in a microwave company and you need to spend as much time as possible learning how they operate. Without these Agilent/HP donations, we would not be able to provide students with this type of "hands-on" training, and we need to be very careful with this equipment. The most important safety measure in working with the NA's is to avoid electrostatic discharge (ESD) while working at the bench. As we walk, we accumulate 1charge and when we touch something conductive, this charge drains off as an ESD. We usually do not even feel it until it gets to thousands of volts, but we must always assume that it is possible. Therefore, NEVER TOUCH THE NETWORK ANALYZER CABLES AND ATTACHMENTS UNLESS YOU WEAR A GROUNDING STRAP! An ESD into the coaxial input ports candamage the very sensitive microwave receivers in the system. They are very expensive to repair.Other than this, you probably will not hurt anything by pushing buttons and learning what the NA can do. (But, avoid "delete" and "modify" keys.) Goal: To learn how to use Agilent ADS to predict the performance of simple microstrip elements and to learn how to use the HP NA to measure the S-parameters for comparison of theory and experiment. Procedure: You will be provided with four simple microstrip line circuits to analyze using the ADS software. You will also be provided with calibrated microstrip adapters for the NA so that you can measure the elements and compare the results. An illustration of these circuits and their equivalent models is attached. The procedure you should use in this lab consists of these steps: 1. Read through the ADS tutorial on the class website 2. Use information provided by the TA for the dimensions of 4 sample lines to draw out the lab circuits with dimension labeled. Look up the material characteristics for "RO4350 Microwave Laminate" 3. Launch a new project in ADS and enter the substrate parameters using the MLIN substrate element under the “T-line Microstrip” category. 4. For each of the four circuits, one at a time, input the MLIN elements along with their measured widths and lengths, and connect the circuit to the test fixture. 5. For each of the four circuits, one at a time, analyze the S-parameters from 1 to 8 GHz and form plots of amplitude and phase for each parameter. You should plot and print all of the magnitudes and all of the phases for each circuit on the same graphs. Use dB logscales (0 to -50 dB) for the magnitudes and use degrees (-180 to 180) for the phases. Also, be sure to print your circuit schematic diagram for your report. 6. For each of the four circuits, make a plot of S11 on a Smith Chart and S21 on a Polar Plot. These alternative outputs provide both magnitude and phase on the same chart. 7. Start your work with the NA by using the straight-line element to check NA calibration. Read the supplementary handout for calibration procedures. You will need to learn how to adjust the NA output scale in order to see how well S21 2approximates 0 dB and how well S11 approximates - dB as it should for a uniform length of line. Document your results for your report to demonstrate that you are getting about what you expect for a simple piece of transmission line and that the NA is calibrated. In all future labs, you should always check calibration by first measuring a piece of straight line. You can then just state in your report that this check was done and what the results were in terms of deviations from ideal. 8. Measure each of the remaining three elements using the NA and make plots that compare the amplitudes and phases of the parameters against the theory from ADS. Often youwill find that the parameters for the second port are essentially the same as the first. If this is true, it is okay to just state this in your lab report and not output the whole set of parameters. Write-Up Discuss your step-by-step procedure in sufficient detail so that a peer can follow what you have done and the results you obtained. Bundles of graphs with no explanations are unacceptable. You should make hand notations as needed on all graphs to explain the results and identify the curves. Include graphs of the S-parameters