Example Usage
Square-wave modulated noise
To generate a simulated voltage recorder observation of normally-distributed white noise in which the intensity is periodically modulated by a square wave, set up two configuration files (one for data and one for weights); e.g.
Example data_config.txt
HDR_VERSION 1.0
HDR_SIZE 4096
NPOL 2
NDIM 2
NCHAN 96
NBIT 16
TELESCOPE SKA1-Low
INSTRUMENT LowCBF
SOURCE SquareWave
MODE CAL
CALFREQ 10.0 # Hz
CAL_DUTY_CYCLE 0.2
CAL_OFF_INTENSITY 5.0
CAL_ON_INTENSITY 6.0
START_CHANNEL 0
UDP_NSAMP 32
WT_NSAMP 32
UDP_NCHAN 24
UTC_START 2023-08-05-11:07:09
OBS_OFFSET 0
FREQ 1000
BW 3.7037 # MHz
TSAMP 25.92 # microseconds
Example weights_config.txt
HDR_VERSION 1.0
HDR_SIZE 4096
NPOL 1
NDIM 1
NCHAN 96
NBIT 16
TELESCOPE SKA1-Low
INSTRUMENT LowCBF
SOURCE SquareWave
MODE CAL
UDP_NSAMP 32
WT_NSAMP 32
UDP_NCHAN 24
UTC_START 2023-08-05-11:07:09
OBS_OFFSET 0
FREQ 1000
BW 3.7037 # MHz
TSAMP 829.44 # microseconds
Generate one second of simulated data with
ska_pst_generate_file -d data_config.txt -w weights_config.txt -s SquareWave -T1.0
To process the signal using dspsr, first create a dual-file input meta file; e.g.
ls data/*.dada > data.ls
ls weights/*.dada > weights.ls
cat > dual.ls << EOD
DUAL FILE:
data.ls
weights.ls
EOD
Then run dspsr
dspsr dual.ls
The output data file is named 2023-08-05-11:07:09.ar
(corresponding to the UTC_START
in the configuration file) and
the contents of this file can be plotted with
psrplot -p freq+ 2023-08-05-11:07:09.ar -j p -j "r .5" -D /xs
This will plot a phase-vs-frequency image of the pulsed intensity, with the power from both polarizations added together, like the following
It is also possible to put spectral gradient on the intensity of the square wave for each polarization; e.g.
CAL_ON_POL_0_CHAN_0_INTENSITY 6.0
CAL_ON_POL_0_CHAN_N_INTENSITY 12.0
CAL_ON_POL_1_CHAN_0_INTENSITY 16.0
CAL_ON_POL_1_CHAN_N_INTENSITY 8.0
yields in pol 0:
and in pol 1: