PST Static Configuration

As part of the work for AT3-821 and AT3-816 the PST schema was rationalised static configuration codified within the PST code base.

This page documents the YAML file and the fields within it.

Future work will further improve on this and get these values from the SKA Telescope Model. This will be needed to deal with the change in CBF/PST configuration values, such as the Mid CBF channelisation will change in the future. This structure can also be extended to all for dynamically determining which polyphase filter bank (PFB) coefficients have been used based on the cbf_firmware_release in the PST scan configuration.

Top level structure

The YAML file, telescope_config.yaml, has the following structure:

• A list of telescopes

• For each telescope a dictionary of frequency_bands. For SKALow there is only 1 band but for SKAMid bands 1, 2, 3, 4, 5a, and 5b are defined.

• For each frequency band, there is static configuration for the receiver (receiver_config) and CBF/PST configuration (cbf_pst_config).

An example of the high level structure of the YAML file is as follows:

- name: SKALow
  frequency_bands:
    low:
      receiver_config:
        ...
      cbf_pst_config:
        ...
- name: SKAMid
  frequency_bands:
    "1":
      receiver_config:
        ...
      cbf_pst_config:
        ...

CBF/PST Configuration (cbf_pst_config)

This section of the YAML file provides configuration that defines how the correlator beam former (CBF) channelises the data and the UDP packet structure that is sent to PST.

Name	Notes
tsamp	The sampling interval, in microseconds.
udp_nchan	The number of PST fine channels in a UDP packet.
udp_nsamp	The number of time samples in a UDP packet.
wt_nsamp	The number of samples per weight in a UDP packet. This value should be same as udp_nsamp
nbit	The number of bits used to represent a dimension of a sample value (total bits is number of dimensions * nbit)
wt_nbit	The number of bits per weight.
oversampling_ratio	The oversampling ratio for the frequency band.
max_nchan	The maximum number of channels for the frequency band.
chan_separation_khz	The frequency separation between the start and end of a channel, in kHz.
rf_freq_minimum_mhz	The bottom end of the frequency band, in MHz.
rf_freq_maximum_mhz	The top end of the frequency band, in MHz.
rf_bw_mhz	The bandwidth of the band, in MHz.
channel_0_start_freq_mhz	The effective start frequency of channel 0, in MHz.
ring_buffer_config/num_buffers	The number of buffers withing a ring buffer. This is internal to PST
ring_buffer_config/packets_per_buffer	The number of UDP packets per buffer that a channel needs be recorded for.
channelisation_stages/num_frequency_channels	The number of channels used in the channelisation stage.
channelisation_stages/oversampling_ratio	The oversampling ratio for the channelisation stage.

Receiver Feed Configuration (receiver_config)

While the receiver feed configuration is not used with in the PST code the following values are added as metadata to the output files of the PST processing.

Name	Notes
receiver_id	The name/id of the receiver. This relates to the telescope and frequency band
feed_polarization	The native polarisation of the feed for the receiver.
feed_handedness	The handedness of the feed of the receiver.
feed_angle	The feed angle of the receiver.
feed_tracking_mode	The tracking mode for the feed of the receiver.
feed_position_angle	The requested angle of feed reference.

Example

- name: SKALow
  frequency_bands:
    low:
      receiver_config:
        receiver_id: LOW
        feed_polarization: LIN
        feed_handedness: 1
        feed_angle: 45.0
        feed_tracking_mode: FA
        feed_position_angle: 0.0

      cbf_pst_config:
        udp_format: LowPST
        tsamp: 207.36
        udp_nchan: 24
        udp_nsamp: 32
        wt_nsamp: 32
        nbit: 16
        wt_nbit: 16
        oversampling_ratio: [4, 3]
        max_nchan: 82944
        chan_separation_khz: 3.616898148
        rf_freq_minimum_mhz: 49.6093750
        rf_freq_maximum_mhz: 349.609375
        rf_bw_mhz: 300.0
        channel_0_start_freq_mhz: 49.609375
        ring_buffer_config:
          num_buffers: 64
          packets_per_buffer: 16
        channelisation_stages:
        - num_frequency_channels: 1024
          oversampling_ratio: [32, 27]
        - num_frequency_channels: 256
          oversampling_ratio: [4, 3]
...