MHO_LSBOffset

Purpose

MHO_LSBOffset applies a phase offset to the lower sideband (LSB) channels of double-sideband (DSB) channel pairs. The operator constructs a complex phasor from a user-supplied phase offset value (in degrees) and multiplies the visibility data of LSB channels by that phasor. The correction is applied independently for the reference and remote stations, with conjugation applied to the phasor that is applied to the remote station.

Control File Trigger

  • Keyword: lsb_offset

  • Category: calibration

  • Priority: 3.4

Parameters for lsb_offset

Parameter

Type

Description

value

real

The LSB phase offset in degrees.

Input Data

This operator acts on the visibility_type container.

Algorithm

MHO_LSBOffset has no Initialize method; all work occurs in ExecuteInPlace.

The builder (MHO_LSBOffsetBuilder) retrieves the phase offset value from the value attribute and the target station identifiers from the control file, then configures the operator.

Execution (``ExecuteInPlace``):

  1. Iterate over the reference (index 0) and remote (index 1) stations.

  2. For each station, check applicability via IsApplicable:

    1. Retrieve the station’s Mark4 ID and 2-character station code from the visibility container.

    2. Match against the configured station identities. A 1-character identity is matched against the Mark4 ID (with ? as wildcard); a 2-character identity is matched against the station code (with ?? as wildcard).

  3. If applicable, construct the LSB phasor:

    \[\Phi = \exp\!\left(i \cdot \phi_{\rm lsb} \cdot \pi/180\right)\]

    where \(\phi_{\rm lsb}\) is the phase offset in degrees and \(\pi/180\) is the degrees-to-radians conversion. For the remote station (st_idx = 1), the phasor is conjugated: Phi_rem = conj(Phi).

  4. Iterate over all polarization products and channels:

    1. For each channel, check for the presence of both the dsb_partner and net_sideband labels.

    2. If dsb_partner is present and net_sideband equals L (lower sideband), multiply all visibility data for that (polarization-product, channel) sub-view by Phi.

Effect on Data

For each station that matches the configured station identities, the visibility data of every lower-sideband channel within a double-sideband pair is multiplied by the phasor exp(i * phi_lsb * pi/180). The reference station receives the phasor directly; the remote station receives the conjugated phasor. Only channels tagged with both dsb_partner and net_sideband = L are modified. Upper-sideband channels and non-DSB channels are untouched.