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Title: A 77-118 GHz RESONANCE-FREE SEPTUM POLARIZER

Measurements of polarized radiation often reveal specific physical properties of emission sources, such as the strengths and orientations of magnetic fields offered by synchrotron radiation and Zeeman line emission, and the electron density distribution caused by free-free emission. Polarization-capable, millimeter/sub-millimeter telescopes are normally equipped with either septum polarizers or ortho-mode transducers (OMT) to detect polarized radiation. Though the septum polarizer is limited to a significantly narrower bandwidth than the OMT, it possesses advantageous features unparalleled by the OMT when it comes to determining astronomical polarization measurements. We design an extremely wide-band circular waveguide septum polarizer, covering 42% bandwidth, from 77 GHz to 118 GHz, without any undesired resonance, challenging the conventional bandwidth limit. Stokes parameters, constructed from the measured data between 77 GHz and 115 GHz, show that the leakage from I to Q and U is below ±2%, and the Q – U mutual leakage is below ±1%. Such a performance is comparable to other modern polarizers, but the bandwidth of this polarizer can be at least twice as wide. This extremely wide-band design removes the major weakness of the septum polarizer and opens up a new window for future astronomical polarization measurements.
Authors:
; ;  [1]
  1. Department of Physics, National Taiwan University, 106 Taipei, Taiwan (China)
Publication Date:
OSTI Identifier:
22340322
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 211; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ELECTRON DENSITY; EMISSION; GHZ RANGE; MAGNETIC FIELD CONFIGURATIONS; MAGNETIC FIELDS; PHYSICAL PROPERTIES; POLARIMETERS; POLARIZATION; RESONANCE; STOKES PARAMETERS; SYNCHROTRON RADIATION; TELESCOPES; TRANSDUCERS; WAVEGUIDES; ZEEMAN EFFECT