Signal Integrity and EMI Fundamentals

Course 243

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Summary

This course covers the methodology of designing an electronic product to minimize the possibilities for electromagnetic interferences (EMI) and signal integrity (SI) problems. The techniques are useful specially for designers of high speed digital and analog circuits, and radiofrequency designers. The basics of designing electronic products with SI and EMI in mind are introduced in a very understandable and entertained style. This is a three day course with a very practical approach through many real world examples, techniques, simulation and hardware demos.

First, the basics of EMI and SIGNAL INTEGRITY in electronic circuits including a review of components in the high frequency/speed domain are presented. The typical EMI/SI problems (crosstalk, reflections, coupling mechanisms, radiation, pickup, etc.) are discussed in a general perspective. Transmission lines and impedance matching are covered because of the importance in the design of a robust system as explained in the rest of the course.

Second, GROUNDING, FILTERING and the design techniques for PRINTED CIRCUIT BOARDS (PCBS) in high frequency/speed systems are covered.

Finally, CABLES, the longest elements in our designs are discussed. They are key elements in the signal propagation and antenna effects of any electronic design. A general and intuitive explanation of antenna fundamentals is included for non RF specialists explaining in a very intuitive way the radiation and pick-up behaviour of cables as "hidden antennas." Finally instrumentation and measuring and troubleshooting techniques for EMI/SI problems are included.

No prior EMI/SI knowledge is needed but an electrical engineering background (BSEE or equivalent experience) is recommended.

Learning objectives

Upon completing the course you will be able to:

  • understand the basics and fundamentals of EMI and SIGNAL INTEGRITY (SI) issues.
  • look at the high frequency fundamentals of EMI/SI, modelling the problems to be able to propose solutions.
  • locate and fix EMI/SI problems in a product or installation.
  • design electronic equipment to avoid common EMI/SI failures.
  • use lab measurements and tools to find or fix typical EMI/SI problems.
  • reduce time and cost of EMI/SI diagnostic and fixes.

Target Audience

  • Design engineers/technicians from the electronics industry involved in EMI and SIGNAL INTEGRITY (SI) problems.
  • those interested in a working knowledge of EMI/SI engineering principles and concerned with EMI/SI problems as high speed digital designers, RF designers and PCB layout engineers.
  • managers responsible for design, production, test and marketing of electronic products.
  • marketing engineers who need a general and practical knowledge of the EMI/SI basics.

Outline

Day One

Fundamentals
 • Electrical signals • Maxwell vs. Kirchhoff: limits of circuit theory • Decibel and logarithmic scales • Spectrum of a signal: time domain vs. frequency domain • Resonance • Quality factor (Q) both loaded and unloaded • Bandwidth • Impedance matching definition • Frequency vs. dimensions (size) • Time vs. distance • Scattering parameters (s-parameters) • Typical formats and how to measure them
High speed/frequency effects in electronic circuits: when a capacitor is an inductor
 • High speed and RF effects: attenuation, gain, loss and distortion • Skin effect, return current and parasitic effects • The importance of rise time and fall times (dv/dt and di/dt) • Controlling signal return currents, differential vs. common mode currents • Introduction • Non ideal components • The "hidden schematic" concept - Resistors, capacitors and inductors - Ferrites - Transformers - Diodes - Transistors - ICs • Digital and high speed circuit key parameters - power, speed and package • Wires • Cables and connections basics • PCB structures (dielectric materials, structures, dissipation factor, the multi-layer structure idea) • Transmission lines basics • Lumped vs. distributed systems • Vias (effects and modelling in high frequency) • Shielding basics • Clocks
Transmission lines: controlling propagation
 • Wiring and connecting components - limitations for high frequency and high speed systems • What is a transmission line? • Motivation: signal propagation • Modelling a transmission line - Characteristic impedance - Velocity of propagation • description of typical transmission lines - coax, pairs, microstrip and stripline • Reflection coefficient • Standing wave ratio (SWR, VSWR and ISWR) and Return loss • Intuitive explanation • Examples from real world
Matching: Avoiding reflections. Obtaining maximum power transfer
 • Maximum transfer of power and avoiding reflections • Matching with LC components • Matching networks: L, PI and T networks • Matching in narrow and broadband networks • Matching with transformers • Matching with transmission lines • Terminations to avoid SI/EMI problems: solutions and techniques • Using software to design a matching network • Examples from real world

Day Two

Signal Integrity Parameters
 • What is Signal Integrity (SI) in electronic circuits? • undesired effects • Propagation time and delay • Reflections and ringing • Inductive vs. capacitive coupling - crosstalk (near and far) • Delays • Jitter • Ground bounce • Power supply noise • High frequency, dv/dt and di/dt
Grounding: the most important subject
 • Signal ground vs. safety ground • Ground in high frequency/speed applications - low impedance path • Minimizing ground impedance • Common impedance • Ground strategies (single point, multipoint, and hybrid) • Ground loops
Filtering
 • Basic ideas • Filters for known impedances (no EMI applications) • Basic design techniques with examples • Filters for EMI/EMC • How filters work: reflection vs. dissipation • Insertion losses • Source and load influence • Parasitic and location effects • Filtering with ferrites • Saturation and undesired coupling effects • Decoupling and bypass fundamentals • Damping resonances and ringing • Three terminal and feed through components
Printed Circuit Boards (PCBs)
 • Basic ideas • Design strategy • Partitioning and critical zones • PCB structures - dielectric materials, structures, dissipation factor • Choosing the PCB structure: how many layers and distribution • Power planes design and distribution • Layout and routing (1, 2 and multilayer) techniques - traces - microstrip and stripline - corners - vias - controlling impedance for SI - transmission line effects and solutions • Ground planes • Splits or ground discontinuities in planes (slots) • Decoupling and bypass (how, where, resonances, etc): discrete capacitors vs. embedded techniques in high speed/RF designs • Crosstalk and guards • How ground plane layout affects crosstalk • Mixed signal PCBs (A/D designs) • Controlling clock waveform • Clock distribution • Clock shielding • Examples from real world

Day Three

Cables
 • Basic ideas for cable fundamentals • The control of return current • Types of cables (wires, twisted pairs, coax, shielded cables, ribbon cables, etc.) • Cable impedance • Shielded cables and cable grounding • Connectors • Parasitics in connectors for high speed signals • Avoiding crosstalk and reflections in cables (layout and terminations) • Avoiding common impedance in cables • Reducing emissions and pick-up in cables • Examples from real world
Measuring and Troubleshooting Techniques
 • Antenna basics • How to measure EMI and SI effects - tools, instruments and techniques • Scope and probe limitations • Review of some typical errors in measurement techniques • Measuring high frequency current in electronic circuits • Diagnostic and troubleshooting techniques and hints • Locating EMI sources with near field probes