Synthetic Filterbank File Generation

About

The code Ersatz.py generates non-stationary Gaussian noise and RFI. The output is saved as a SIGPROC filterbank file. The correlation length and the amplitude of the non-stationary noise along with the specifics for the injected RFI are specified in a .txt file that is passed to the function.

How to use

1. To download the python function called Ersatz.py right click here: ersatz.py and choose 'Save As'. The current name of the fucntion is 'ersatz.py_1.txt', rename it as 'ersatz.py'.

2. Create or download a .txt file specifying the noise characteristics, RFI and bandpass as below:

**************************************

Baseline Lambda 2
Baseline Amplitude 4
Broadband Occurrences 0
Broadband t_start 0
Broadband t_end 0
Broadband Magnitude 0
Narrowband Occurrences 0
Narrowband F_start 0
Narrowband F_end 0
Narrowband t_start 0
Narrowband t_end 0
Narrowband Magnitude 0
Periodic Broadband Occurrences 0
Periodic Broadband Period 0
Periodic Broadband Duty cycle 0
Periodic Broadband t_start 0
Periodic Broadband t_end 0
Periodic Broadband Magnitude 0
Periodic Narrowband Occurrences 0
Periodic Narrowband Period 0
Periodic Narrowband Duty cycle 0
Periodic Narrowband F_start 0
Periodic Narrowband F_end 0
Periodic Narrowband t_start 0
Periodic Narrowband t_end 0
Periodic Narrowband Magnitude 0
BandPass ramp-up 0.3
BandPass ramp-down 0.2
BandPass Amplitude 0.5

**************************************

 

             

Identifier Description
Baseline Precedes the variables associated with the non-stationary baseline.
Broadband Precedes the variables associated with impulse RFI.
Narrowband Precedes the variables associated with narrowband RFI.
Bandpass Precedes the variables associated with giving the bandpass a shape.
Baseline Lambda Non-stationary baseline correlation length in seconds.
Baseline Amplitude Amplitude of the non-stationary noise  (0< value ≤ 6).
Occurrences Number of RFI instances.
t_start The start time of the RFI instances (s)
t_end  The end time of the RFI instances  (s)
Magnitude

The magnitude of the noise i.t.o. the number of standard deviations from the expected value (0< value ≤6)
F_start   First frequency affected by RFI artefact (MHz)
F_end Ending frequency affected by RFI artefact (MHz)
Period Period of the periodic noise (s)
Duty cycle Specify how long the RFI should be 'on' as a percentage of its period (0<value<99).
Ramp-up  Specify the protion of highest frequency channels to be modulated (0<value<1).
Ramp-down Specify the portion of lowest frequency channels to be modulated (0<value<1).
Amplitude Specifies the height of the slope (0<value<1).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NB. If any of the noise phenomena should be ignored just set the 'Occurrences' variable to zero.

NB. For the bandpass shape to be enforced the flag '"--bandPass" should be set when ersatz.py is called.

 

 

3. An example of how to call the function:

>> python ersatz.py --tobs 20.0 --tsamp 64 --fch1 1536 --foff -0.62890625 --nchans 512 --nbits 8 --noiseInput FakeNoiseParameters.txt --stationary "No" --bandPass