This program performs a plain old Fourier transform or a polyphase filter bank operation on baseband (raw voltage time series) data. In other words, this is a software spectrometer. The input is expected to be 8-bit, complex, dual-polarization data, interleaved in the following manner:

The output is written in the headerless SIGPROC .fil format, along with a .fhd configuration file.

If doing PFB, this program requires a filter coefficients file to be present in the current directory. Filter coefficients files can be created using the yapp_genpfbcoeff.py Python script.

Usage:

The options are:

• -h or --help: Display this usage information
• -s or --skip time: Length of data to be skipped, in seconds (default is 0 s).
• -p or --proc time: Length of data to be processed, in seconds (default is all data).
• -l or --tsamp tsamp: Sampling time in seconds.
• -f or --centre-freq freq: Centre frequency of the observing band in MHz.
• -b or --pfb: Do polyphase filter bank.
• -t or --ntaps ntaps: Number of taps in the PFB (default is 8).
• -n or --nfft N: Number of points in FFT (default is 4096).
• -a or --nacc acc-len: Number of spectra to be accumulated (default is 1 - no accumulation).
• -o or --obs-site site-name: Observatory name.
• -r or --pulsar psr-name: Pulsar name.
• -g or --graphics: Turn on plotting.
• -i or --invert: Invert background and foreground colours in plots (default is white on black).
• -e or --non-interactive: Run in non-interactive mode.
• -v or --version: Display the version.

The flags -l (or --tsamp) and -f (or --centre-freq) are required arguments.

Example:

The following performs an 8-tap pre-filtering followed by a 1024-point Fourier transform on the data in rawdata.dat. The spectra thus produced are accumulated to a length of 10, and the output is written to a headerless SIGPROC filterbank file named rawdata.dat.fil, and metadata is written to a file named rawdata.dat.fhd. The site name (in this case, 'GBT') and the pulsar name ('J1921+2153') go into the metadata file.