Acknowledgments for the Second Edition
For the new material in Chapter 6 (Hot parameters), I'd like to thank David Root and Jan Verspecht for their theoretical work, and Xin Chen for the implementation. Chapter 7 (differential and IQ mixer measurements) was implemented in firmware by Xin Chen as well. Many thanks for his great efforts.
My thanks for the implementation work in Chapter 8, which was realized in software by Jean‐Pierre Teyssier, along with his expert consulting on the concepts of coherent spectrum analysis.
Acknowledgments from the First Edition
Many of my colleagues assisted in the development and review of this book, and I would like to acknowledge their help here. Henri Komrij, my R&D manager, has been a great supporter from the initial concept, as well as Greg Peters, V.P. and general manager of the Components Test Division. Many R&D engineers in our lab contributed to the review of the manuscript, and their expertise in each field is sincerely appreciated: Keith Anderson, Dara Sariaslani, Dave Blackham, Ken Wong, Shinya Goto, Bob Shoulders, Dave Ballo, Clive Barnett, Cheng Ning, Xin Chen, Mihai Marcu, and Loren Betts. They did an excellent job, and any remaining errors are entirely and regrettably my own.
Many of the new methods and techniques presented here rely on the difficult and precise implementation of measurement methods and algorithms, and I'd like to thank our software design team, Johan Ericsson, Sue Wood, Jim Kerr, Phil Hoard, Jade Hughes, Brad Hokkanen, Niels Jensen, Raymond Taylor, Dennis McCarthy, Andy Cannon, Wil Stark, Yu‐Chen Hu, Zhi‐Wen Wong, and Yang Yang, as well as their managers, Sean Hubert, Qi Gao, and Dexter Yamaguchi for all their help over the years in implementing in our products many of the functions described here.
Finally, I would like to remember here Dr. Roger Pollard, who as my PhD adviser at University of Leeds and as a colleague during his sabbaticals at HP and Agilent Technologies, provided advice, mentoring, and friendship; he will be greatly missed.
1 Introduction to Microwave Measurements
“To measure is to know.”1 This is a book about the art and science of measuring microwave components. While this work is based entirely on science, there is some art in the process, and the terms skilled‐in‐the‐art and state‐of‐the‐art take on particular significance when viewing the task of measuring microwave components. The goal of this work is to provide the latest, state‐of‐the‐art methods and techniques for acquiring the optimum measurements of the myriad of microwave components. This goal naturally leads to the use of the vector network analyzer (VNA) as the principal test equipment, supported by the use of power meters, spectrum analyzers (SAs), signal sources and noise sources, impedance tuners, and other accessories.
Note here the careful use of the word optimum; this implies there are trade‐offs between the cost and complexity of the measurement system, the time or duration of the measurement, the analytically computed uncertainty and traceability, and some heretofore unknown intangibles that all affect the overall measurement. For the best possible measurement, ignoring any consequence of time or cost, one can often go to national standards laboratories to find these best methods, but they would not suit a practical or commercial application. Thus, here the attempt is to strike an optimum balance between minimal errors in the measurement and practical consequences of the measurement techniques. The true value of this book is in providing insight into the wide range of issues and troubles that one encounters in trying to carefully and correctly ascertain the characteristics of one's microwave component. The details have been gathered from decades of experience in hundreds of direct interactions with actual measurements; some problems are obvious and common, and others are subtle and rare. It is hoped that the reader can use this handbook to avoid many hours of unproductive test time.
For the most part, the mathematical derivations in this book are intended to provide the reader with a straightforward connection between the derived values and the underlying characteristics. In some cases, the derivation will be provided in full if it is not accessible from existing literature; in other cases, a reference to the derivation will be provided. There are extensive tables and figures, with key sections providing many of the important formulas. The mathematical level of this handbook is geared to a college senior or working engineer with the intention of providing the most useful formulas in an approachable way. As such, sums will be preferred to integrals; finite differences will be preferred to derivatives; and divs, grads, and curls will be entirely eschewed.
The chapters are intended to self‐standing for the most part. In many cases, there will be common material to many measurement types, such as the mathematical derivation of the parameters or the calibration and error‐correction methods, and these will be gathered in the introductory chapters, though well referenced in the measurement chapters. In some cases, older methods of historical interest are given (there are many volumes on these older techniques), but by and large only the most modern techniques are presented. The focus here is on the practical microwave engineer facing modern, practical problems.
1.1 Modern Measurement Process
Throughout the discussion of measurements, a six‐step procedure will be followed that applies to most measurement problems. When approaching a measurement, these steps are as follows:
Pretest: This important first step is often ignored, resulting in meaningless measurements and wasted time. During the pretest, measurements of the device‐under‐test (DUT) are performed to coarsely determine some of its attributes. During pretest, it is also determined if the DUT is plugged in, turned on, and operating as expected. Many times the gain, match, or power handling is discovered to be different than expected, and much time and effort can be saved by finding this out early.
Optimize: Once the coarse attributes of the device have been determined, the measurement parameters and measurement system can be optimized to give the best results for that particular device. This might include adding an attenuator to the measurement receivers, adding booster amplifiers to the source, or just changing the number of points in a measurement to capture the true response of the DUT. Depending upon the device's particular characteristic response relative to the system errors, different choices for calibration methods or calibration standards might be required.
Calibrate: Many users will skip to this step, only to find that something in the setup does not provide the needed conditions and they must go back to the first step, retest, and optimize before recalibration. Calibration is the process of characterizing the measurement system so that systematic errors can be removed from the measurement result. This is not the same as obtaining a calibration sticker for an instrument but really is the first step, the acquisition step of the error correction process that allows improved measurement results.
Measure: Finally, some stimulus is applied to the DUT, and its response to the stimulus is measured. During the measurement, many aspects of the stimulus must be considered, as well as the order of testing and other testing conditions. These include not only the specific test conditions but also pre‐conditions such as previous power states to account for non‐linear responses of the DUT.
Analyze: Once the raw data is taken, error correction factors (the application step of error correction) are applied to produce a corrected result. Further mathematical manipulations on the measurement result can be performed to create more useful figures of merit, and the data from one set of conditions can be correlated with other conditions to provide useful insight into the DUT.
Save data: The final step is saving the results in a useful form. Sometimes this can be as simple