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Table of Contents

Title Page

Preface

The global navigation satellite system (GNSS) is becoming yet another pillar technology in today's society along with the Internet and mobile communications. GNSS offers a range of services, such as navigation, positioning, public safety and surveillance, geographic surveys, time standards, mapping, and weather and atmospheric information. The usage of GNSS applications has become nearly ubiquitous from the ever-growing demand of navigation facilities made available in portable personal navigation devices (PNDs). Sales of mobile devices including smart phones with integrated GNSS are expected to grow from 109 million units in 2006 to 444 million units in 2012, and this sector of industry is second only to the mobile phone industry. The navigation industry is predicted to earn a gross total of $130 billion in 2014. The current developments and expected future growth of GNSS usage demand the availability of more sophisticated terminal antennas than those previously deployed.

The antenna is one of most important elements on a GNSS device. GNSS antennas are becoming more complex every day due to the integration of different GNSS services on one platform, miniaturisation of these devices and performance degradations caused by the user and the local environment. These factors should be thoroughly considered and proper solutions sought in order to develop efficient navigation devices. The authors have been active in this research area over the last decade and are aware that a large amount of information on GNSS antenna research is scattered in the literature. There is thus a need for a coherent text to address this topic, and this book intends to fill this knowledge gap in GNSS antenna technology. The book focuses on both the theory and practical designs of GNSS antennas. Various aspects of GNSS antennas, including the fundamentals of GNSS and circularly polarised antennas, design approaches for the GNSS terminal and satellite antennas, performance enhancement techniques used for such antennas, and the effects of a user's presence and the surrounding environment on these antennas, are discussed in the book. Many challenging issues of GNSS antenna design are addressed giving solutions from technology and application points of view.

The book is divided into eight chapters.

Chapter 1 introduces the concept of GNSS by charting its history starting from DECCA land-based navigation in the Second World War to the latest versions being implemented by the USA (GPS), Europe (GLONASS and Galileo) and China (Compass). The fundamental principles of time delay navigation are addressed and the operation of the US NAVSTAR GPS is described. The enhanced applications of the GPS are addressed including its use as a time reference and as an accurate survey tool in its differential form.

Chapter 8 describes radio wave propagation between the GNSS satellite and the ground receiver and the rationale for selecting circularly polarised (CP) waves. It also introduces the relevant propagation issues, such as multipath interference, RF interference, atmospheric effects, etc. The fundamental issues in GNSS antenna design are highlighted by presenting the basic approaches for designing a CP antenna.

Chapter 3 covers the requirements for spacecraft GNSS antennas illustrating the descriptions of typical deployed systems for both NAVSTAR GPS and Galileo. The various special performance requirements and tests imposed on spacecraft antennas, such as passive intermodulation (PIM) testing and multipactor effects, are also discussed.

Chapter 4 deals with the specifications, technical challenges, design methodology and practical designs of portable terminal GNSS antennas. It introduces various intrinsic types of terminal antennas deployed in current GNSSs, including microstrip, spiral, helical and ceramic antennas.

Chapter 5 is dedicated to multimode antennas for an integrated GNSS receiver. The chapter presents three kinds of multimode GNSS antennas, namely dual-band, triple-band and wideband antennas. Practical and novel antenna designs, such as multi-layer microstrip antennas and couple feed slot antennas, are discussed. It also covers high-precision terminal antennas for the differential GPS system, including phase centre determination and stability.

Chapter 6 discusses the effects of the multipath environment on the performance of GNSS antennas in mobile terminals. It highlights the importance of statistical models defining the environmental factors in the evaluation of GNSS antenna performance and proposes such a model. It then presents a detailed analysis of the performance of various types of mobile terminal GNSS antennas in real working scenarios using the proposed model. Finally, it describes the performance enhancement of the terminal antennas in difficult environments by employing the techniques of beamforming, antenna diversity, A-GPS and ESTI standardised reradiating.

Chapter 7 deals with the effects of the human user's presence on the GNSS antennas, presenting details of the dependency of antenna performance on varying antenna–body separations, different on-body antenna placements and varying body postures. It also considers the effects of homogeneous and inhomogeneous human body models in the vicinity of the GNSS antennas. Finally, it discusses the performance of these antennas in the whole multipath environment operating near the human body, using a statistical modelling approach and considering various on-body scenarios.

Chapter 8 describes the limitations of both antenna size and shape that are imposed when GNSS functions are to be added to small devices such as mobile handsets and personal trackers. It is shown how the radiation patterns and polarisation properties of the antenna can be radically changed by factors such as the positioning of the antenna on the platform. The presence of a highly sensitive receiver system imposes severe constraints on the permitted levels of noise that may be generated by other devices on the platform without impairing the sensitivity of the GPS receiver. The chapter gives the steps which must be taken to reduce these to an acceptable level. The case studies cover a range of mobile terminal antennas, such as small backfire helices, CP patches and various microstrip antennas.

This is the first dedicated book to give such a broad and in-depth treatment of GNSS antennas. The organisation of the book makes it a valuable practical guide for antenna designers who need to apply their skills to GNSS applications, as well as an introductory text for researchers and students who are less familiar with the topic.