Mathcad worksheets
PLT (Powerline Telecommunications)
Other projects
Mathcad worksheets, PLT and other projects
This page points you towards various files in Mathcad format (version 8 or earlier) 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 Root Solutions' webstore at http://www.mathcad-store.co.uk/ in the UK.

Other material including PLT discussion and project reports can be found further down:

EMC testing

Attenuator pads and mismatch 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 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 RF immunity testing 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 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

Electromagnetic fields

Shielding effectiveness of a box with a slot This is a zipped file including animations and a presentation based on the work of Martin Robinson et al at the University of York. The source from which it derives can be found at York's website, which has a Java-based calculator. 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 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 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
The Ofcom statement on PLT
A discussion of the enforcement implications of the April 2011 Ofcom "supplement" on PLT. Published in the EMC Journal June 2011
After the EMC Directive
Discusses the EC's response to complaints about PLT adaptors, and considers what this may mean for enforcement of the EMCD. Published in the EMC Journal July 2009
RF emissions of Powerline Ethernet adaptors Reports the results of conducted emissions tests on a widely-used powerline modem, and discusses some implications. Published in the EMC Journal May 2009
Why broadband PLT is bad for EMC (second pass) An update of a paper first written in 2005, which remains on this website (below). Published in the EMC Journal January 2009
Why broadband PLT is bad for EMC (first pass) Written in 2005 and unpublished elsewhere, the title says it all. If you are looking at this site on a broadband connection, read this paper and ponder. A heavily revised version appeared in the EMC Journal, issue 80 January 09. See above

DTI-NMSPU Projects

The project on Uncertainties of Immunity Measurements has its own download page.

The
LISNs and absorbing clamps report was for a project sponsored by the UK DTI to give a guidance for best practice in testing with and calibrating the CISPR LISN and ferrite absorbing clamp.  This report has been written to advise test engineers and others on techniques for the use and calibration of transducers for RF conducted emissions and disturbance power measurements. These measurements are inherent in many European EMC standards that are based on the CISPR emissions methods, and form an important part of testing to meet the compliance requirements of the European EMC Directive.

Several experiments were carried out to determine the effect on measurement result of various factors, such as grounding of the LISN, positioning of the EUT, cable layout and so on. The report presents the results of these experiments and makes recommendations for improvements in the use and calibration of these transducers.

From here you can download:

    the executive summary, as a short HTML document;
    the full report, as a large PDF file (3MB).
Audio files of PLT interference
6.175MHz-1
To go with the papers opposite, for interest. Recorded on HF with a pair of Comtrend PG902 adaptors as supplied with BT Vision, in the same room
Music programme on 12MHz, the units are switched on after 0:14 seconds
12MHz-1
Starts with a French programme on 6.175MHz, the units are switched on after 0:30 seconds; after 0:60 seconds they are transferring data, and are turned off after 1:40
13.7MHz-1a
Starts in the middle of transferring data, then transfer ends after 0:22 seconds and units are turned off after 0:34 seconds - voice programme reappears
Starts with a music programme on 13.7MHz, the units are switched on after 0:23 seconds and stay in standby
13.7MHz-1b
13.7MHz-2
Starts in the middle of transferring data, the transfer ends at 0:23 seconds and the units are turned off after 0:40 - voice programme reappears

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