Electronic Design

Small Antenna Design, First Edition

Communications Engineering SeriesBy Dr. Douglas MironISBN: 0750678615

Most EEs today are educated in almost everything but RF and antennas. Some EEs even consider themselves lucky not to have had to endure a good electromagnetics course featuring the every popular Maxwell's equations. Yet with the rising demand for wireless embedded into every electronic product, many of you are wishing you had an RF course or two to fall back on. I have talked with more than a few engineers who have really had to learn RF and wireless related stuff on their own.

Probably the subject most often neglected is antennas. It is a strange and complex subject. I have often wondered how a truly mechanical device or structure like an antenna can make all the difference in the world as to whether a wireless technology works or not. Yet, the antenna is often overlooked in the early design stages of a project. The antenna is the final link that determines the success or failure of the product.

As a ham, I have played around with antennas for years. The variety is nearly infinite as are experimentation possibilities. What is fascinating is the quest for smaller, more compact antennas. As products have been miniaturized, so has the need to reduce the antenna size. Moving up into the microwave region has really helped in that regard. At lower frequencies, you still need length and size to get the kind of efficiency and performance preferred. Most of these techniques for creating ever smaller antennas are described in this book.

Chapter 1 defines small and gives some examples of small antennas. Chapters 2 and 3 review antenna fundamentals. It is a pretty good introduction to the subject for those who know nothing and a great review for someone who may have learned these principles previously. In chapter 3, I especially appreciated the impedance matching section. Today, some impedance matching network is always going to be needed between the transceiver and the antenna, especially with small antennas. The section on grounds and ground planes is a good reminder how big a role a good ground plays in antenna performance.

Chapters 4 and 5 get into the subject of numerical modeling of wire antennas. The author uses the government developed Numerical Electromagnetic Code (NEC) to show how antennas can be simulated mathematically. Chapter 6 continues with the discussion. Most of the software that’s included on the CD supplied with the book uses NEC.

Chapter 6 is on open-ended antennas, mostly variations of the popular monopole. Some of the topics are thick monopoles, top loading, radials, coil loading, and all the related math. Chapter 7 addresses loops and other closed-wire antennas. This is material I have never seen anywhere else. All kind of loops and helical antennas are discussed. Chapter 8 focuses on receiving antennas. The ferrite loop is discussed as well as active loops and whips. Chapter 9 covers measurements, a topic that eludes many who have to work with antennas. The book concludes with a batch of interesting appendices.

Overall, the book is a good one that I recommend. It is heavy on the math, but none of it is overly exotic and all of it is easily dealt with. Even though I already have a dozen antenna books in my personal library, I like this one as it adds another dimension. The author has obviously had the experience to create this unique book.

P.S. If you are really getting into antenna design you may be interested in some good continuing education courses on the subject. These courses are conducted by the American Radio Relay League, ham radio's premium organization. They have an excellent Antenna Modeling course (EC-004) and a follow-on course called Antenna Design and Construction (EC-009). The first course uses a version of the NEC software described in the book. The ARRL also has courses on RFI and RF propagation, which may be of interest. Check out their website at www.arrl.org.

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