Chapter 9. Standing Wave Removal

Table of Contents

9.1. Introduction to Standing Wave Removal
9.2. Modified Passband Calibration Method
9.3. Sine Wave Fitting Method (fitHifiFringe)
9.3.1. Introduction to fitHifiFringe
9.3.2. Running fitHifiFringe
9.3.3. Example of Using fitHifiFringe
9.4. Reference Spectrum Matching Technique (HEB Bands)

Last updated: 26 January, 2012

9.1. Introduction to Standing Wave Removal

At many locations in the HIFI instrument, standing waves are generated. The standard (SPG) pipeline and AOTs are designed to minimize the amplitude of these waves in level 2 spectra. However, for certain observing modes, some mixer bands, and some observation characteristics (sky signal strength, signal-to-noise level) particular residual waves may still be present:

  1. All bands: a 98 MHz wave from the cold black body to mixer cavity

  2. All bands: a 92 MHz wave from the hot black body to mixer cavity

  3. All bands: a 100 MHz wave from the local oscillator unit to mixer cavity

  4. Diplexer bands (3,4,6,7): a 620 MHz wave from the diplexer rooftop to mixer cavity

  5. HEB bands (6,7): a ~320 MHz wave from within the HEB mixers

Depending on the science application, the user may want to remove these waves. Different techniques may need to be applied for the different waves. These are described in the next sections.