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Systematic effects induced by a flat isotropic dielectric slab
Claudio Macculi1, Mario Zannoni, Oscar Antonio Peverini
1INAF-IASF Roma, Roma, Itlay. claudio.macculi@iasf-roma.inaf.it
Applied Optics
|July 11, 2006
Summary
Even isotropic dielectric slabs can cause spurious polarization in microwave frequencies. A Teflon slab, however, introduces negligible polarization, making it suitable for radio astronomy applications.
Area of Science:
- Physics
- Astronomy
- Materials Science
Background:
- Instrumental polarization can arise from isotropic dielectric materials in microwave frequencies.
- Understanding and mitigating spurious polarization is crucial for sensitive radio astronomy observations.
Purpose of the Study:
- To investigate the instrumental polarization induced by flat isotropic dielectric slabs at microwave frequencies.
- To evaluate the performance of common radio astronomy materials in generating spurious polarization.
- To quantify polarization leakage and depolarization effects.
Main Methods:
- Utilized the Mueller matrix formalism to evaluate instrumental polarization.
- Measured complex dielectric constants of various dielectric materials.
- Applied results to a 32 GHz receiver scenario with different slab configurations.
Main Results:
- Isotropic dielectrics can induce spurious polarization through transmission of anisotropic radiation or thermal inhomogeneity.
- A 0.33 cm thick Teflon slab demonstrated negligible spurious polarization (<2.6 x 10^-5 in transmission, <6 x 10^-7 in emission).
- Teflon also minimized polarization leakage (<10^-8) and depolarization (~1.3 x 10^-3).
Conclusions:
- Instrumental polarization can occur even with isotropic dielectrics, necessitating careful material selection in radio astronomy.
- Teflon is a highly suitable material for radio astronomy applications due to its minimal induced polarization and leakage.
- The Mueller matrix formalism provides an effective framework for assessing instrumental polarization effects.
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