Über die Autorin bzw. den Autor

Dr. Ian A Glover is a Senior Lecturer. Research interests: radio science, microwave radio propagation, channel measure ments and modelling, and digital communications coding and modulation. He is co-author of the successful book Digital Communications.

Dr. Steve R. Pennock is a Senior Lecturer. Research interests: microwave engineering and communications, inset dielectric guide antennas and subsystems, monolithic microwave integrated circuits, flared slot antennas, discontinuities and non-uniformities in transmission lines and millimetre wave propagation effects.

Dr. Peter R. Shepherd is a Senior Lecturer and First Year Course Director. Research interests: microwave engineering and communications, inset dielectric guide antennas and subsystems, monolithic microwave integrated circuits, flared slot antennas, discontinuities and non-uniformities in transmission lines, millimetre wave propagation effects, and mixed signal integrated circuits

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Microwave Devices, Circuits and Subsystems for Communications Engineering provides a detailed treatment of the common microwave elements found in modern microwave communications systems. The treatment is thorough without being unnecessarily mathematical. The emphasis is on acquiring a conceptual understanding of the techniques and technologies discussed and the practical design criteria required to apply these in real engineering situations.

Key topics addressed include:
* Microwave diode and transistor equivalent circuits
* Microwave transmission line technologies and microstrip design
* Network methods and s-parameter measurements
* Smith chart and related design techniques
* Broadband and low-noise amplifier design
* Mixer theory and design
* Microwave filter design
* Oscillators, synthesisers and phase locked loops

Each chapter is written by specialists in their field and the whole is edited by experience authors whose expertise spans the fields of communications systems engineering and microwave circuit design.

Microwave Devices, Circuits and Subsystems for Communications Engineering is suitable for senior electrical, electronic or telecommunications engineering undergraduate students, first year postgraduate students and experienced engineers seeking a conversion or refresher text.

* Includes a companion website featuring:
* Solutions to selected problems
* Electronic versions of the figures
* Sample chapter

Aus dem Klappentext

Microwave Devices, Circuits and Subsystems for Communications Engineering provides a detailed treatment of the common microwave elements found in modern microwave communications systems. The treatment is thorough without being unnecessarily mathematical. The emphasis is on acquiring a conceptual understanding of the techniques and technologies discussed and the practical design criteria required to apply these in real engineering situations.

Key topics addressed include:
* Microwave diode and transistor equivalent circuits
* Microwave transmission line technologies and microstrip design
* Network methods and s-parameter measurements
* Smith chart and related design techniques
* Broadband and low-noise amplifier design
* Mixer theory and design
* Microwave filter design
* Oscillators, synthesisers and phase locked loops

Each chapter is written by specialists in their field and the whole is edited by experience authors whose expertise spans the fields of communications systems engineering and microwave circuit design.

Microwave Devices, Circuits and Subsystems for Communications Engineering is suitable for senior electrical, electronic or telecommunications engineering undergraduate students, first year postgraduate students and experienced engineers seeking a conversion or refresher text.

* Includes a companion website featuring:
* Solutions to selected problems
* Electronic versions of the figures
* Sample chapter

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Microwave Devices, Circuits and Subsystems for Communications Engineering

John Wiley & Sons

Chapter One

I. A. Glover, S. R. Pennock and P. R. Shepherd

1.1 Introduction

RF and microwave engineering has innumerable applications, from radar (e.g. for air traffic control and meteorology) through electro-heat applications (e.g. in paper manufacture and domestic microwave ovens), to radiometric remote sensing of the environment, continuous process measurements and non-destructive testing. The focus of the courses for which this text was written, however, is microwave communications and so, while much of the material that follows is entirely generic, the selection and presentation of material are conditioned by this application.

Figure 1.1 shows a block diagram of a typical microwave communications transceiver. The transmitter comprises an information source, a baseband signal processing unit, a modulator, some intermediate frequency (IF) filtering and amplification, a stage of up-conversion to the required radio frequency (RF) followed by further filtering, high power amplification (HPA) and an antenna. The baseband signal processing typically includes one, more, or all of the following: an antialising filter, an analogue-to-digital converter (ADC), a source coder, an encryption unit, an error controller, a multiplexer and a pulse shaper. The antialisaing filter and ADC are only required if the information source is analogue such as a speech signal, for example. The modulator impresses the (processed) baseband information onto the IF carrier. (An IF is used because modulation, filtering and amplification are technologically more difficult, and therefore more expensive, at the microwave RF.)

The receiver comprises an antenna, a low noise amplifier (LNA), microwave filtering, a down-converter, IF filtering and amplification, a demodulator/detector and a baseband processing unit. The demodulator may be coherent or incoherent. The signal processing will incorporate demultiplexing, error detection/correction, deciphering, source decoding, digital-to-analogue conversion (DAC), where appropriate, and audio/video amplification and filtering, again where appropriate. If detection is coherent, phase locked loops (PLLs) or their equivalent will feature in the detector design. Other control circuits, e.g. automatic gain control (AGC), may also be present in the receiver.

The various subsystems of Figure 1.1 (and the devices comprising them whether discrete or in microwave integrated circuit form) are typically connected together with transmission lines implemented using a variety of possible technologies (e.g. coaxial cable, microstrip, co-planar waveguide).

This text is principally concerned with the operating principles and design of the RF/ microwave subsystems of Figure 1.1, i.e. the amplifiers, filters, mixers, local oscillators and connecting transmission lines. It starts, however, by reviewing the solid-state devices (diodes, transistors, etc.) incorporated in most of these subsystems since, assuming good design, it is the fundamental physics of these devices that typically limits performance.

Sections 1.2-1.7 represent a brief overview of the material in each of the following chapters.

1.2 RF Devices

Chapter 2 begins with a review of semiconductors, their fundamental properties and the features that distinguish them from conductors and insulators. The role of electrons and holes as charge carriers in intrinsic (pure) semiconductors is described and the related concepts of carrier mobility, drift velocity and drift current are presented. Carrier concentration gradients, the diffusion current that results from them and the definition of the diffusion coefficient are also examined and the doping of semiconductors with impurities to increase the concentration of electrons or holes is described. A discussion of the semiconductor energy-band model, which underlies an understanding of semiconductor behaviour, is presented and the important concept of the Fermi energy level is defined. This introductory but fundamental review of semiconductor properties finishes with the definition of mean carrier lifetime and an outline derivation of the carrier continuity equation, which plays a central role in device physics.

Each of the next six major sections deals with a particular type of semiconductor diode. In order of treatment these are (i) simple P-N junctions; (ii) Schottky diodes; (iii) PIN diodes; (iv) step-recovery diodes; (v) Gunn diodes; and (vi) IMPATT diodes. (The use of the term diode in the context of Gunn devices is questionable but almost universal and so we choose here to follow convention.) The treatment of the first three diode types follows the same pattern. The device is first described in thermal equilibrium (i.e. with no externally applied voltage), then under conditions of reverse bias (the P-material being made negative with respect to the N-material), and finally under conditions of forward bias (the P-material being made positive with respect to the N-material). Following discussion of the device's physics under these different conditions, an equivalent circuit model is presented that, to an acceptable engineering approximation, emulates the device's terminal behaviour. It is a device's equivalent circuit model that is used in the design of circuits and subsystems. There is a strong modern trend towards computer-aided design in which case the equivalent circuit models (although of perhaps greater sophistication and accuracy than those presented here) are incorporated in the circuit analysis software. The discussion of each device ends with some comments about its manufacture and a description of some typical applications.

The treatment of the following diode types is less uniform. Step-recovery diodes, being a variation on the basic PIN diode, are described only briefly. The Gunn diode is discussed in some detail since its operating principles are quite different from those of the previous devices. Its important negative resistance property, resulting in its principal application in oscillators and amplifiers, is explained and the relative advantages of its different operating modes are reviewed. Finally, IMPATT diodes are described, that, like Gunn devices, exhibit negative resistance and are used in high power (high frequency) amplifiers and oscillators, their applications being somewhat restricted, however, by their relatively poor noise characteristics. The doping profiles and operating principles of the IMPATT diode are described and the important device equations are presented. The discussion of IMPATT diodes concludes with their equivalent circuit.

Probably the most important solid-state device of all in modern-day electronic engineering is the transistor and it is this device, in several of its high frequency variations, that is addressed next. The treatment of transistors starts with some introductory and general remarks about transistor modelling, in particular, pointing out the difference between small and large signal models. After these introductory remarks three transistor types are addressed in turn, all suitable for RF/microwave applications (to a greater or lesser extent). These are (i) the gallium arsnide metal semiconductor field effect transistor (GaAs MESFET); (ii) the high electron mobility transistor (HEMT); and (iii) the heterojunction bipolar transistor (HBT). In each case the treatment is essentially the same: a short description followed by presentations of the current-voltage characteristic,...