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Book Review |
Reviewed by Norm Violette, Associate Editor |
These two introductory sections set the tone for the flow of the book's five main chapters. This book is essentially a companion to Volumes 1 and 2 which were reviewed in two previous EMC Society Newsletters.
This chapter presents basic concepts. Goals are defined that should be achieved to minimize interconnect noise interactions in high-speed digital printed circuit boards (PCBs). The transmission line (T-line) behavior of PCB traces at digital high-speed and high frequency performance is described. The dependence of performance on the PCB relative dielectric constant (relative permittivity) is described along with other transmission line parameters.
Specific applications to the microstrip configuration are illustrated. Capacitive effects in loads and T-lines are described to determine minimum load separation.
The chapter also addresses crosstalk, power distribution, decoupling capacitor applications, power dissipation in TTL and CMOS devices, thermal conduction, heat radiation, and control. Lossy T-lines and propagation delays are described.
VLSI failures and electromigration, topology-related and material-related problems are addressed and electromigration mechanisms are described. Other topics include interference concerns with connectors, including crosstalk; ground loops and radiated interference; solving interference problems in connectors; filtering; shielding; and the issue of vias.
The basic characteristics of noise in op-amps are presented and classified as either white noise or color noise, random or repetitive, of voltage or current form, and can be found at any frequency. An example of a noise density spectrum is illustrated. Thermal noise is described with sample calculations presented including the determination of noise figure.
Op-amp fundamental specifications are explained including the feedback concept. The characteristics of shot noise, flicker noise, and popcorn noise are described. The need for an input offset voltage is described. Op-amp noise gain, slew rate, power bandwidth, and gain-bandwidth product are defined. An analysis of op-amp internal noise is provided along with noise issues in high-speed ADC applications.
Power supply decoupling, the application of decoupling capacitors, and the design of power bus rails in power/ground planes for noise control are described. The effect of trace resistance and resulting power loss are analyzed. Signal integrity and the effects of ground bounce and crosstalk are described.
A discussion is presented of considerations and difficulties encountered in the use of EDA tools for ASICs in the design and delivery of submicron (mm) components and circuits. The main problems occur because parasitic effects such as parasitic (distributed) capacitance, inductance, and resistance become significant due to close proximities and affect circuit performance. The current EDA state-of-the-art can handle 0.5 mm and often deal with 0.35 mm, but the deep submicron area at 0.25 mm presents problems for current (1998) EDA design techniques.
The problem of providing a clear analog input signal into an analog-to-digital converter (ADC) arises because an ADC has several possible inputs, to wit: ground pins, power supply pins, and reference pins which can also act as inputs. These must be treated so as to prevent inherent noise and interfering signals from coupling into these paths and thereby corrupt the analog output. This ÒmeatyÓ chapter provides detailed analyses and many illustrations that describe techniques for identifying and mitigating these problems. Generally, analog circuits are much more sensitive and can be corrupted more easily than digital circuits.
The grounding of ADCs is presented as critical. Proper bypassing and circuit layout are also described as essential. The use of RC filters in the driving input of ADCs is described. Filtering the switched-mode power supply (SMPS) and the choices of capacitors for filtering are described. The use of inductors, ferrites, and ferrite cores in SMPSs are presented.
The shielding of cables in op-amp inputs is discussed and illustrated. The troublesome RFI rectification in analog circuits is illustrated. Op-amps driving capacitor loads, including load capacitance from cabling, are presented in detail.
Intermodulation distortion, phase-locked loops (PLLs), and voltage-controlled oscillators (VCOs) are described including VCO phase noise and Phase Detectors.
Some types of capacitors and carbon resistors can generate a substantial amount of 1/f type noise and thereby contribute to noise in low-pass filters. The design of low-noise circuits therefore requires the selection of low-noise capacitors and resistors. The noise power density is described.
Phase noise is described in DC amplifiers, high-frequency amplifiers, phase detection circuits, digital frequency dividers, frequency multipliers, oscillators, and reference frequency generators.
RF interference at the transistor level is described along with rectification in PN junctions. Illustrations and models are provided of the mechanisms of RF interference. RFI effects in op-amps and crystal oscillators are described.
A general introduction addresses the impact of Maxwell's formulations governing "... the electrical nature of matter and the fields associated with the currents involved." He (Maxwell) probably could not have imagined the application of computers and computational techniques used to solve his complex equations under a variety of boundary conditions and provide results that can be experimentally proven. The purpose of this chapter is to: "...discuss briefly the profound effect that computational techniques have had in solving electromagnetic field problems, especially those problems related to the area of electromagnetic compatibility (electromagnetic interference)."
Approaches to solving problems in electromagnetics include analysis and synthesis techniques, concepts of input-output, transfer functions, field propagators, and coupling mechanisms.
The selection of a field propagator is the first step in the development of a computer model. Basic categories of field propagators discussed include (1) integral equations, (2) differential equations, (3) optical equations, (4) network equations, and (5) multiple field equations. Details are presented that describe the different types of field propagators for each of these categories.
Computational Electromagnetic: Techniques presented and described briefly for constructing mathematical models and algorithms for solving problems in electromagnetics include the Method of Moments (MOM), with developments on the mathematical theory of the MOM, modeling problems using wire geometries, choosing basis and weighting functions, modeling problems using surface geometries, hybrid MOM for wire and surface currents, the aperture problem in the MOM, the two-media problem, slot apertures, and the hybrid MOM for apertures.
High frequency methods in computational electromagnetics are presented including geometrical optics, geometric theory of diffraction (GTD), the uniform geometric theory of diffraction, the physical theory of diffraction, and the hybrid MOM/GTD methods in EMC.
The Finite Difference Time Domain (FDTD) techniques are developed including structural modeling in FDTD, YeeÕs implementation of FDTD, and boundary conditions, with illustrations.
The Finite Element Method (FEM) and the Transmission Line Method (TLM) are presented, including Scattering concepts for 2D and 3D geometries.
A section is included on Computational Methods at Work: Getting Numbers from Your Models. Five worked examples are studied to illustrate the application of electromagnetic models based on MOM (three examples) and FDTD (one example) methods. The fifth example is an overview of several techniques applied to a single PCB. Several references are listed to complete this basic but comprehensive chapter.
A summary review is presented for determining the electric (E) and magnetic (H) fields due to currents in a radiating structure. The procedure illustrates the determination of the fields from vector potentials which, in turn, are derived from the structure currents. Radiated fields from thin wire antennas are then determined.
The characteristics of the linear dipole are derived and the radiated fields from dipoles are determined due to simple and sinusoidal current distributions. Radiated fields are then derived for thin wire loop antennas (circular and square loop geometry).
Models are derived and illustrated for microstrip antennas, antenna arrays, reflector antennas, and helix antennas.
Numerical methods (MOM, FDTD) are discussed in the design of loop antennas and cylindrical arrays for personal communication services (PCS). A brief outline is provided of antennas that can be modeled by the MOM. Radiation pattern models are illustrated of monopole and helix antennas mounted on a conducting box.
This book is highly recommended for engineers who work in fields related to modern wireless communications. It can also serve as a useful reference for undergraduate and graduate students in electrical engineering that have an interest in this field. EMC