This page points you towards various files in Mathcad format for use by EMC engineers. Disclaimer: no guarantee is given as to the suitability or correctness of these calculations. Use them at your own risk.
If you don't have Mathcad, it's available from the webstore at Adept Scientific in the UK. Full information and links are at Adept Scientific's Mathcad home page.
EMC Testing
| Title | Size | Mathcad version | Comments |
|---|---|---|---|
| Attenuator pads and mismatch | 21k | 4 | Attenuator pads are used to reduce mismatch errors. This worksheet allows you to calculate resistor values versus attenuation for any impedance; it also covers VSWR and reflection coefficient, and how to calculate mismatch errors with and without pads |
| Chamber and enclosure resonance | 22k | 8 | Any rectangular screened enclosure exhibits internal resonances. This worksheet allows you to calculate the frequencies of the different resonant modes of an empty enclosure |
| Modulation | 20k | 8 | RF immunity testing now requires you to use a modulated signal. This sheet illustrates the effect of modulation and will calculate the increase in peak and RMS power that results from applying sinusoidal modulation |
| Field strength on an OATS | 24k | 8 | NB this is a zipped file including an animation Open Area Test Sites (OATS) have a defined path loss and the field strength you measure is maximised using an antenna height scan. This worksheet demonstrates the effect of the height scan and will calculate the measured field strength for an isotropic emitter of known power across 30-1000MHz at any site distance |
EM Fields
| Title | Size | Mathcad version | Comments |
|---|---|---|---|
| Shielding effectiveness of a box with a slot | 304k | - | This is a zipped file including animations and a presentation based on the work of Martin Robinson at the University of York. The Mathcad files from which it derives can be found at York's site. The animations show the effect of different sizes of box, different sizes of slot in a wall of that box, and variations in the measurement position within the box. |
| The field equations | 59k | 6 | Maxwell's field equations when applied to elemental loops and dipoles show the concept of wave impedance and the distinction between near field and far field. This worksheet allows you to calculate the field vectors from an elemental radiator at any point in space. |
| Magnetic fields from 3-phase cables | 12k | 6 | Using the Biot-Savart law, this worksheet will calculate and display the magnetic flux density in a plane a fixed distance away from a group of wires carrying three phase current. You can modify the cable geometry, distance from the cables, current flowing and three-phase balance. |
More worksheets will follow...
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