Engenharia

Chapter 9: Antennas II
David R. Jackson Jeffery T. Williams Donald R. Wilton Applied Electromagnetics Laboratory Department of Electrical and Computer Engineering University of Houston Houston, TX 77204-4005

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TABLE OF CONTENTS INTRODUCTION I. MICROSTRIP ANTENNAS A. Introduction B. Basic Principles of Operation C. Feeding Techniques D. Resonance Frequency E. Radiation Patterns F. Radiation Efficiency G. Bandwidth H. Input Impedance I. Improving Performance II. BROADBAND ANTENNAS A. Introduction B. Helical Antenna C. Frequency Independent Antennas D. Spiral Antennas E. Log-Periodic Antennas III. TRAVELING AND LEAKY-WAVE ANTENNAS A. Introduction B. Slow-Wave Antennas C. Leaky-Wave Antennas 1. Uniform Structures 2. Periodic Structures 3. Two-Dimensional Leaky-Wave Antennas

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IV. APERTURE ANTENNAS A. Introduction B. Radiation from Apertures C. Electrically Small Rectangular Slot D. Rectangular Horn Antenna E. Reflector Antennas V. PHASED ARRAYS A. Array Far Fields B. Array Pattern Characteristics C. Array Gain D. Array Elements E. Phased Array Feed and Beamforming Systems F. Electronic Beamsteering G. Mutual Coupling REFERENCES

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INTRODUCTION In Chapter 8, an overview of basic antenna terminology and antenna properties was given, including a discussion of concepts that are common to all antennas. In the present chapter, the discussion is focused on the specific properties of several representative classes of antennas that are commonly used. These include microstrip antennas, broadband antennas, phased arrays, traveling and leaky-wave antennas, and aperture antennas. Of course, in a single chapter, it is impossible to cover all of the types of antennas that commonly used, or even to adequately cover all of the design aspects of any one type of antenna. However, this chapter should provide enough information about the five types of antennas that are discussed here to allow the reader to obtain a basic overview of the fundamental properties of these