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Westbay Tools v2 for Windows

Emc Analysis, Calculations and Utilities

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A superb collection of software tools for performing a wide variety of emc (electromagnetic compatibility) related tasks. Automates and provides graphical display of shielding, transient, filtering, crosstalk and pcb instances of emc design and analysis. Releases emc theories for use as a set of practical tools.


Emc can seem a bewildering subject, especially when a complete analysis of the susceptibility or emission characteristics of an item of equipment is virtually impossible. It is tempting to just 'test and see', and try to correct non-compliances as they occur. However, many sub-sets of the entire emc description of the equipment are possible. These can examine for example the performance of a decoupling capacitor in maintaining the voltage at a chip during a current demand; Westbay Tools provides an immediate graph of output voltage versus time, and includes the effect of inductance in series with the capacitor.

Transient clamping using non-linear devices is not an easy topic to analyse, so Westbay Tools provides a ready-made model summarising load and device voltage and energy. In keeping with the practical nature of the program, an inductance may be placed in series with the clamping device, to assess the importance of lead and track inductance when dealing with fast pulses.

Transient Clamp.gif (11167 bytes)


Analysis of a transient voltage clamp, using a suppression diode. Pulse and load parameters are fully definable, and load voltage may be plotted.



Westbay Tools does not require the user to learn a Spice type programming language - the tools and utilities are ready programmed for you to enter data. Most importantly, it does not leave you with a mathematical emc expression in a text or course book, with no way to manipulate real data other than to program that formula yourself.

Similarly, critical parameters such as dielectric constants, or metal conductivities, are already present, not hidden away in a book! From basic capacitance and inductor impedance calculations, to advanced crosstalk models of wires over ground planes, Westbay Tools will prove invaluable to your emc program.


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The Waveguide Below Cut-off tool. An instant calculation is provided at a spot frequency, whilst an attenuation vs frequency plot can also be made on-screen, and printed.


Technical Features

Westbay Tools supports the calculations and analyses listed below. (Follow the highlighted links for more details).


  •     Common Mode Field Coupling. Loop pick-up; unbalanced circuits, balanced circuits.
  •     Electromagnetic Field formulae. Transmitter powers, field impedance, magnetic units conversions.
  •     Helmholtz Coils. Axial field analysis, including graphical presentation and field tabulation.
  •     Magnetic Field due to a Current in a Wire.


  •     Shielding Effectiveness. Fundamental enclosure performance. Reflection loss, Absorption loss, Re-reflection loss. Plane, electric and     magnetic waves. Conductivity and Skin Effect are considered.
  •     Waveguide below cut-off. Attenuation due to an open walled aperture extending into an enclosure.
  •     Cavity Resonance. Resonant frequencies of a walled enclosure. Useful for indication of minimum resonant frequency, although actual frequencies will be modified by the enclosure contents in practice.
  •     Twisted Pair Rejection Ratio. Degradation in rejection due to out of phase coupling at wire twists.
  •     Circular/Square EMI Gasket Groove Design. Calculates gasket deflection and groove fill for all tolerance conditions. Allows selection of industry standard or custom diameters, and also computes the effect of lid bowing.
  •     Shielding effectiveness due to an aperture in an enclosure. Emitted fields due to pcb DM Loop.

Periodic Waves

  •     Fourier Analysis of trapezoidal, chopped sinusoidal, multi-pulse sequences and user-defined waveforms, with independently definable rise and fall times, and period. Display of harmonics referred to magnitude of fundamental.
  •     Filter Insertion Loss. Display of loss versus frequency for C, L, L-C, C-L, Pi and T Circuits, and Common Mode Choke. User defined component values, source and load resistances. Parasitic capacitances and inductances.
  •     Decibel conversions. dB's to actual power/voltage; referred values (dBm) to actual values; dBuV to dBm.

Transient Waveforms

  •     Transient Voltage Clamping by non-linear devices such as varistors or suppression diodes. Waveform consists of definable linear risetime and exponential fall time. Ground inductance and resistance may be placed in series with clamping device. In addition to source and load resistance, an additional series resistance may be included. Analysis for load and device peak power, current and voltage, and also total energy.

PCB Related Topics

  • Decoupling Capacitance. Maintenance of voltage at a chip during a current demand. In addition to definition of nominal capacitance, ground inductance and resistance can be defined to simulate real capacitors and track layout. Effective decoupling is essential in avoiding fast current transients on pcb supply tracks.
  • Characteristic Impedance of various track and wire geometries, including ground plane effects.
  • Transmission Line Test for Surface Microstrip and Embedded Stripline. Returns the propagation time for a given geometry of track, to enable comparison with signal transition time.
  • Common Mode Rejection Ratio reduction due to capacitance to ground imbalance. Useful for estimating the effect of tolerance of filter components on critical lines.
  • Ground Plane Impedance at dc and rf frequencies, including skin effects.
  • Amplifier Ground Noise Tool; analysis of ground current coupling in single-ended and differential amplifiers.
  • Radiated emissions due to differential and common mode current loop. Continuous spectrum plot, or Fourier analysis of emissions due to a digital waveform.

Capacitance, Inductance and Crosstalk

  • Capacitance and Inductance of assorted structures, including pull down dielectric constants list.
  • Impedance of Capacitance/Inductance, Resonant frequency of L-C circuits.
  • Inductor Q Factor.
  • Crosstalk between parallel wires, with and without a ground plane.
  • Inductance and flux density of toroidal inductors.

Design Guides

  • PCB, ESD and Shielding Design Guides.
  • A flexible Design Review Check List generator, which is fully user-editable.

    PCB Design Guide.gif (9822 bytes)


    PCB Design Guides. Seven Golden Rules are accessed from here, whilst the blue captions launch specific Tools analyses.

    Westbay Tools Lite can be downloaded free of charge.

    System Requirements: Windows 95 or later. test

    Westbay Tools is a trademark of Westbay Technology Ltd.

    Microsoft and Windows are trademarks of Microsoft Corporation
    Copyright Westbay Technology 1995-2011.

Westbay Technology Ltd, Main Street, Baycliff, Ulverston, Cumbria LA12 9RN, England

Tel: 01229 869 798    (from the United Kingdom)    Tel: +44 1229 869 798    (International)                                 Contact by e-mail