Microstrip Patch Antennas

Kai Fong Lee, Kwai Man Luk;Hau Wah Lai

• Publisher: WSPC
• Year: 2017
• ISBN:
  9789813208612
• Edition: 2
• Topic: Tecnologia e ingegneria
• Subtopic: Comunicazioni mobili e wireless

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Microstrip patch antennas have become the favorite of antenna designers because of their versatility and having the advantages of planar profile, ease of fabrication, compatibility with integrated circuit technology, and conformability with a shaped surface. There is a need for graduate students and practicing engineers to gain an in depth understanding of this subject. The first edition of this book, published in 2011, was written with this purpose in mind. This second edition contains approximately one third new materials. The authors, Prof KF Lee, Prof KM Luk and Dr HW Lai, have all made significant contributions in the field. Prof Lee and Prof Luk are IEEE Fellows. Prof Lee was the recipient of the 2009 John Kraus Antenna Award of the IEEE Antennas and Propagation Society while Prof. Luk receives the same award in 2017, both in recognition of their contributions to wideband microstrip antennas.

--> Contents:

• Introduction
• Review of Some Background Materials
• General Formulation of the Cavity Model
• Characteristics of the Rectangular Patch Antenna
• Characteristics of the Circular Patch Antenna
• The Annular-Ring Patch and the Equitriangular Patch
• Introduction to Full Wave Analysis
• Microstrip Patch Antennas with Adjustable Air Gaps
• Broadbanding Techniques I — General Principles, Probe Compensation, Coplanar Parasitic Patches, Stacked Parasitic Patches
• Broadbanding Techniques II — The U-Slot Patch Antenna
• Broadbanding Techniques III — The L-Probe Coupled Patch and the Meandering-Probe Fed Patch
• Broadbanding Techniques IV — Aperture Coupled Patches
• Size Reduction Techniques
• Dual- and Multi-Band Designs
• Dual Polarized Patch Antenna Designs
• Circular Polarization
• Reconfigurable Microstrip Patch Antennas
• Microstrip Antenna Array I — Basic Principles and Examples of Design Below 5 GHz
• Microstrip Antenna Array II — Sixty (60) GHz Antenna Array Design and Applications
• Novel Material Patch Antennas
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  --> Readership: Graduate students, academics and antenna designers in the industry. -->
  Keywords:Microstrip Antennas;Printed Antennas;Planar AntennasReview:

  Review of the First Edition:
  
  

  "With problems at the end of each chapter and many references, this book on MPA is an outstanding textbook for a graduate course or as a self-study guide for the practicing engineer. It will not only give the reader a firm understanding of the fundamentals of MPAs but will also provide the necessary tools for designing and optimizing MPAs. Anyone who designs MPAs or wants to learn about them needs to get a copy of this book."
  
  

  IEEE Electrical Insulation Magazine
  Key Features:
  • Although there are a number of books on microstrip antennas, they were written as reference books rather than as textbooks. The proposed book will present the subject in a way that is suitable as a textbook for a graduate course on antennas, or as a self-study textbook for practicing engineers
  • As befits a textbook, there are problems and/or mini-projects at the end of each chapter, which are absent in existing books on microstrip antennas. The first edition of the book has been classroom tested by Professor K F Lee in his graduate course on Microstrip Antennas at The University of Mississippi and in the short courses he gave at City University of Hong Kong and National University of Singapore
  • The authors have been active contributors to microstrip antenna development since the 1980's. Professor K F Lee was one of the early pioneers. They are well recognized, as evident from the frequent citations to their work in the microstrip antenna literature. This book will draw on many of their own contributions. Describing these contributions first hand will stand out from existing publications

Chapter 1

Introduction

1.1Introductory Remarks

Microstrip patch antennas (MPA) are a class of planar antennas which have been researched and developed extensively in the last four decades. They have become favorites among antenna designers and have been used in many applications in wireless communication systems, both in the military sector and in the commercial sector. The aim of this book is to provide a coherent account of the theory, analysis, and design of these antennas, as well as some recent developments. Since the authors have been involved with the research and development of MPAs from the early 1980’s, this book can also be regarded as a partial record of their personal journeys in this field. A significant fraction of the material is drawn from their own work in the last three decades.

In this opening chapter, we first briefly describe some commonly used antennas before MPAs came on the scene. This helps the reader appreciate the attractiveness of MPAs. The chapter then discusses, in general terms, the basic geometry of the MPA, material considerations, and various feeding methods for the single element. A discussion on the knowledge and skills needed to design MPAs follows. For easy reference, we include the electromagnetic spectrum and its utilization for various wireless communication applications at the end of the chapter.

1.2Conventional Antennas

We review some antennas that are commonly used before the advent of microstrip patch antennas. They will be referred to as conventional antennas.

The simplest and most widely used antenna element is the half-wave dipole, which consists of two linear conductors about a quarter wave long, driven by a source at the center, as shown in Figure 1.1a. Two variations of the half-wave dipole are the quarter wave monopole (Figure 1.1b) and the folded dipole (Figure 1.1c).

Fig. 1.1 Illustrations of (a) dipole; (b) monopole and (c) folded dipole.

Fig. 1.2 (a) A driven element and a director; (b) a driven element and a reflector.

The pattern of a dipole can be modified by placing a passive or parasitic conductor near it. Although the parasitic element is not connected to a source, a current is induced in it due to the radiation from the driven dipole. The total radiation is the sum of the driven and the parasitic elements. By suitably choosing the length and spacing of the latter, it can act either as a reflector enhancing radiation in the direction of the dipole (negative x) or as a director enhancing radiation in its own direction (positive x). These are illustrated in Figure 1.2.

An antenna consisting of a driver, a reflecting element, and one or more directing elements is called a Uda-Yagi array or a Yagi for short (Figure 1.3). There is a limit to the number of parasitic elements that can be added to a Yagi since the induced current on a parasitic element becomes progressively smaller as its distance from the driven element increases. It ceases to play an effective role if it is placed too far from the driven element. Yagis are seldom designed to have more than 12 elements. A 7 element Yagi using a folded dipole as driver is shown in Figure 1.3b.

Fig. 1.3 (a) A three-element Yagi-antenna and (b) a seven-element Yagi-antenna using folded dipole as driver.

While a thin conductor can act as a reflector, it is highly sensitive to frequency. The frequency dependence is reduced if a plane conducting sheet is used instead. The effectiveness of the reflecting sheet can be further enhanced if it is bent into two sheets intersecting at an angle, as shown in Figure 1.4a. The resulting structure is known as a corner reflector antenna. The corner reflector has the limitation that, even if the sides are infinite in extent, there is an upper limit to the directivity of the resultant radiation. To reduce wind resistance, the reflecting metal sheets are replaced by conducting rods, resulting in a grid type corner reflector antenna (Figure 1.4b).

Other traditional antenna elements are the loop antenna, the horn antenna, and the helical antenna. The loop antenna is used extensively in TV reception and as directional finders. An indoor TV antenna consisting of a dipole and a loop is shown in Figure 1.5.

By flaring the aperture of an open-ended waveguide, a horn antenna is obtained (Figure 1.6). The horn antenna is used extensively at microwave frequencies, both as feed antennas for parabolic reflectors and as the standard calibration antenna for gain.

For communication with satellites and space vehicles, electromagnetic waves with circular polarization (CP) is preferred over linear polarization (LP). The helical antenna (Figure 1.7) is a popular CP antenna and was the antenna brought to the moon by the astronauts in the late 1960’s and early 1970’s.

Fig. 1.4 (a) Plane conductor type corner reflector antenna and (b) grid type corner reflector antenna.

Fig. 1.5 An indoor TV antenna.

Two important antenna parameters are the gain and the impedance bandwidth. The gain describes the directional property of an antenna while the impedance bandwidth describes the range of frequencies within which the voltage standing wave ratio is below a certain value. This value is usually taken as 2 in academia and 1.5 in industry. The abbreviation for voltage standing wave ratio is VSWR or SWR. Both will be used in this book. Table 1.1 shows the typical values of these two parameters for the conventional antenna elements described above.

Fig. 1.6 A horn antenna.

Fig. 1.7 A helical antenna.

Table 1.1 Typical gain and bandwidth of conventional antenna elements.

One method of obtaining high gain antennas is to use an array of fed elements, all of which are connected to a source. A linear array is one with the elements arranged in a straight line. The elements can also be arranged in a plane, resulting in a planar array. The element spacing is usually about half a wavelength. In theory, for a given spacing, the gain can be made as high as one wishes by increasing the number of elements. Figure 1.8 shows a linear array of folded dipoles. Photograph of a planar array of helical antennas is shown in Figure 1.9.

Fig. 1.8 A linear array of folded dipoles.

Fig. 1.9 A planar array of eight helical antennas. (Courtesy of SETI League).

Another method of obtaining high gain antennas is to use a parabolic reflector, with the feed antenna at the focus. This antenna is also known as a dish. For a given frequency, the gain is proportional to the diameter of the dish. In theory, the gain can be made as high as one wishes by increasing the dish diameter. Figure 1.10a shows the 1000 feet dish at the Arecibo Observatory in Puerto Rico. Figure 1.10b shows the 300 feet dish in Effelsberg, Germany. The former is the world’s largest dish but it is fixed on the ground, although the main beam can be steered to a limited extent by electronic means. The latter is one of the world’s largest fully steerable dishes. Figure 1.11 shows the Very Large Array (VLA) in New Mexico, consisting of 27 85-feet dishes arranged in the form of the letter Y.

Fig. 1.10 (a) The dish antenna at the Arecibo Observatory in Puerto Rico (Courtesy of Astronomy and Ionosphere Center); and (b) the dish antenna in Effelsberg, Germany (Courtesy of Max Planck Institute for Radio Astronomy).

Fig. 1.11 The Very Large Array (VLA) in New Mexico. (Courtesy of National Radio Astronomy Observatory).

Several undesirable features of the conventional antennas can be noted. They ...