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Über dieses Buch

To handle many standards and ever increasing bandwidth requirements, large number of filters and switches are used in transceivers of modern wireless communications systems. It makes the cost, performance, form factor, and power consumption of these systems, including cellular phones, critical issues. At present, the fixed frequency filter banks based on Film Bulk Acoustic Resonators (FBAR) are regarded as one of the most promising technologies to address performance -form factor-cost issues. Even though the FBARs improve the overall performances the complexity of these systems remains high. Attempts are being made to exclude some of the filters by bringing the digital signal processing (including channel selection) as close to the antennas as possible. However handling the increased interference levels is unrealistic for low-cost battery operated radios. Replacing fixed frequency filter banks by one tuneable filter is the most desired and widely considered scenario. As an example, development of the software based cognitive radios is largely hindered by the lack of adequate agile components, first of all tuneable filters. In this sense the electrically switchable and tuneable FBARs are the most promising components to address the complex cost-performance issues in agile microwave transceivers, smart wireless sensor networks etc.

Tuneable Film Bulk Acoustic Wave Resonators discusses FBAR need, physics, designs, modelling, fabrication and applications. Tuning of the resonant frequency of the FBARs is considered. Switchable and tuneable FBARs based on electric field induced piezoelectric effect in paraelectric phase ferroelectrics are covered. The resonance of these resonators may be electrically switched on and off and tuned without hysteresis.

The book is aimed at microwave and sensor specialists in the industry and graduate students. Readers will learn about principles of operation and possibilities of the switchable and tuneable FBARs, and will be given general guidelines for designing, fabrication and applications of these devices.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract
This chapter starts with brief discussions about needs in tuneable resonators focusing on advanced agile microwave communication systems. To assist in reading of the following chapters, vibrational modes in FBARs are reviewed. The concept of electrostriction-mediated induced piezoelectric effect in paraelectrics, used in intrinsically tuneable ferroelectric FBARs, is discussed. A summary of the state-of-the-art in intrinsically tuneable FBARs concludes the chapter.
Spartak Gevorgian, Alexander K. Tagantsev, Andrei Vorobiev

Chapter 2. Dielectric, Mechanical, and Electromechanical Properties of Ferroelectrics and Piezoelectrics

Abstract
This chapter introduces the fundamentals of dielectric, mechanical, and electromechanical properties of insulating solids, primarily focusing on ferroelectric and piezoelectric materials, suitable for FBARs. Sections 2.1, 2.2, and 2.3 address these properties, neglecting the energy dissipation associated with AC signals, whereas Sect. 2.4 is reserved for the discussion of effects related to the energy dissipation (e.g. dielectric and acoustic loss).
Spartak Gevorgian, Alexander K. Tagantsev, Andrei Vorobiev

Chapter 3. Models of FBARs

Abstract
In this chapter, the conventional models of acoustic resonators, such as Mason, KLM, and Lakin, are considered as a general background and possibility of their application (with adequate modifications) for modelling of the tuneable FBARs. In ferroelectric-based tuneable FBARs, the basic parameters, stiffness, acoustic velocity, and relative dielectric permittivity of the ferroelectric film are assumed to be DC electric field dependent.
Spartak Gevorgian, Alexander K. Tagantsev, Andrei Vorobiev

Chapter 4. Making Non-tuneable Piezoelectric FBARs Tuneable

Abstract
This chapter explores the possibilities of tuning the resonant and anti-resonant frequencies of fixed-frequency FBARs. The first two sections address the possibilities of intrinsic tuning where the stiffness of the piezoelectric film is changed through applied high DC electric field and by heating. The rest of the chapter deals with extrinsically tuneable FBARs. In this case, the tuning is imposed by tuneable inductors and capacitors shunt or series connected with an FBAR. The maximum reported intrinsic tuning of the AlN resonators under applied DC field and heating is about 1 %, while the maximum extrinsic tuneability is less than 2 %.
Spartak Gevorgian, Alexander K. Tagantsev, Andrei Vorobiev

Chapter 5. FBARs Utilizing Induced Piezoelectric Effect

Abstract
This chapter is devoted to the theoretical description of tuning of FBARs based on materials with induced piezoelectric effect. Though DC field–induced piezoelectric ity occurs in any centrosymmetric material, only ferroelectrics display an effect that is strong enough to be of interest for practical applications. This chapter is essentially based on the paper by (Noeth et al. 2008). However, apart from the incipient ferroelectrics (regular ferroelectric in the paraelectric phase), ferroelectrics in ferroelectric phase are also considered.
Spartak Gevorgian, Alexander K. Tagantsev, Andrei Vorobiev

Chapter 6. Designs of Tuneable FBARs

Abstract
In this chapter, the basic design features of intrinsically tuneable FBARs are considered focusing on the Bragg reflectors for the solidly mounted resonators. Effects of the electrodes and other layers on the tuneable performance of the FBARs including tuneability, Q-factor, and electromechanical coupling coefficient are also addressed.
Spartak Gevorgian, Alexander K. Tagantsev, Andrei Vorobiev

Chapter 7. Fabrication Processes and Measurements

Abstract
The first sections in this chapter give a brief review of the main processes used for the fabrication of intrinsically tuneable ferroelectric FBARs. Test structures used for low-frequency and microwave measurements and also procedures for extracting the acoustic parameters of the ferroelectric films used in tuneable FBARs are considered in Sect. 7.6. The last sections are devoted to studies of temperature dependence and power-handling capabilities.
Spartak Gevorgian, Alexander K. Tagantsev, Andrei Vorobiev

Chapter 8. Circuit Applications of Tuneable FBARs

Abstract
This chapter looks at the circuit applications of intrinsically and extrinsically tuneable FBARs. VCOs seem to be one of the most attractive circuits for applications of the tuneable FBAR. They benefit both from high Q-factor (much higher than LC tanks based on semiconductor varactors) and tuneability. Perhaps tuneable and switchable filters are the most desired devices. The chapter includes several demonstrators of these types of filters. Some specific applications such as amplifiers, sensors and clocks are also considered.
Spartak Gevorgian, Alexander K. Tagantsev, Andrei Vorobiev

Chapter 9. Conclusions and Challenges

Abstract
The possible ways of increasing the Q-factor, tuneability, and electromechanical coupling coefficients are discussed, including the use of new materials, improvement of crystalline quality in ferroelectric films, and the designs of FBARs. The potential of nanoscale resonators and resonators with graphene electrodes are also discussed.
Spartak Gevorgian, Alexander K. Tagantsev, Andrei Vorobiev

Erratum to: Tuneable Film Bulk Acoustic Wave Resonators

Without Abstract
Spartak Sh. Gevorgian, Alexander K. Tagantsev, Andrei K. Vorobiev

Backmatter

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