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Shreehari

CS115 test procedures

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Hi All

We have a query from the customer related to CS115 test procedure.

. The setup includes a coaxial cable, a pulse generator with 640KV and current injection probe. Kindly explain how I can set up same on

   FEKO. How can apply train of pulses to the cable? This requires time domain analysis. How this can be done?

 

 How I can apply DFT and IDFT in post feko ?? 

 I have to apply pulse at some location in the table and need to measure the current at 5 cm away from that location.attaching file for reference 

System_description_CS114_115_116_Test_Setup_V40.pdf

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We have a query from the customer related to CS115 test procedure.

Who is the customer? Is this not rather a question that should be sent to support and not on the forum?

 

Quote

The setup includes a coaxial cable, a pulse generator with 640KV and current injection probe. Kindly explain how I can set up same on FEKO.

What part of the model have you setup thus far? Have you created the cable and the excitation? A basic cable model is included in the FEKO Example Guide, see "D-2 Calculating field coupling into a shielded cable".

 

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How can apply train of pulses to the cable?

POSTFEKO allows the time signal to be defined and there are a number of signals, see "9.10 Time analysis" in the User Manual. You will probably use the "Ramp pulse", but you can also import your time signal from a file. Since the time domain analysis is based of FFT / IFFT, the signal is repeated and you will probably only define one pulse. Also have a look at "G-1 Time analysis of the effect of an incident plane wave on an obstacle".

 

Quote

 How I can apply DFT and IDFT in post feko ?? 

POSTFEKO does the DFT / IDFT for you as part of the time analysis, but if you want to do it yourself, it can be done using trace math (just use fft or ifft) or in the Lua scripting environment. For the Lua scripting environment, see the Matrix and ComplexMatrix objects since they both have FFT and IFFT methods. You will have to populate the matrix with your data and then perform the FFT / IFFT.

Unfortunately I don't have an example that I can readily share (maybe someone else on the forum does), but here is an extract from a project that I worked on in the past that shows the idea for getting the spectrum of a time signal and the definition of a Triangle signal.

local function Triangle(SignalDuration, Amplitude, Delay, PulseWidth, SamplePoints)
--[[ Returns a Matrix (row) with the defined time signal.
     In this case the time signal is a triangular pulse
--]]
  sigMatrix = pf.Matrix(1,SamplePoints,0)
  for tt = 1, sigMatrix.ColumnCount do
    local t = (tt-1)*SignalDuration/(SamplePoints-1)
    if (math.abs(t -Delay) <= PulseWidth ) then
      sigMatrix[1][tt] = Amplitude * (1- (math.abs(t - Delay))/(PulseWidth))
    end
  end 
  return sigMatrix
end

-- Access or define the time signal
local SignalDuration = 50e-9
local Amplitude = 1
local Delay = 5e-9
local PulseWidth = 2e-9
local SamplePoints = 256
local m = Triangle(SignalDuration, Amplitude, Delay, PulseWidth, SamplePoints)

local dt = SignalDuration/(SamplePoints-1)
local df = 1/SignalDuration

local app = pf.GetApplication()

local fmax = app.Models[1].Configurations[1].EndFrequency 
local fmin = app.Models[1].Configurations[1].StartFrequency 
local fminPos = math.ceil(fmin/df)
local fmaxPos = math.floor(fmax/df)
local Fsamples = fmaxPos - fminPos + 1
assert(fmaxPos<SamplePoints,"Not enough samples. At least "..fmaxPos.." samples are required or reduce the signal duration.")

-- Get the spectrum of the time signal
local S = m:FFT()/(SamplePoints)

 

I hope that helps. The more specific the questions are, the better the chance that we can help you.

 

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