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VERSION:2.0
PRODID:-//Memento EPFL//
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SUMMARY:Quasioptical system for material characterization in millimeter/su
 bmillimeter-wave domain
DTSTART:20150601T103000
DTEND:20150601T113000
DTSTAMP:20260407T053520Z
UID:706f1cde6ad64cb3bfd1552994b4ababaabf0b98affac3bf9f0724f8
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Alireza Kazemipour (Physikalisch-Technische Bundesanstalt 
 (PTB)\, Braunschweig\, Germany)\nMeasurement of intrinsic material propert
 ies\, such as the complex permittivity and permeability\, is very importan
 t in many areas. The relative permittivity is important in microwave and m
 illimeter-wave engineering (substrates and dielectric components)\, agricu
 lture\, material engineering\, and others.\nDifferent measurement techniqu
 es could be used for different frequency bands and applications. For very 
 low-loss materials\, the microwave cavity technique gives best results\, h
 owever\, it is limited to a single frequency and measurement in millimeter
 -wave bands is problematic.\nAnother technique is inserting the measured s
 ample into a rectangular or cylindrical waveguide. The sample preparation 
 is complicated at very high frequencies.\nThe broadband free-space measure
 ment techniques circumvent the problem of the precise fit of the sample t
 o the waveguide or cavity walls. A disadvantage is the need of a flat and
  homogeneous sample with relatively large dimensions to avoid diffraction 
 effects. This method has long been possible for material properties measur
 ement at microwave frequencies using a vector network analyzer (VNA). With
  the advance of measurement instrumentation\, free-space systems for milli
 meter/submillimeter waves became possible as well. Systems for material ch
 aracterization in the submillimeter bands were presented. These systems us
 e complicated design with large parabolic mirrors or lenses\, high-cost co
 rrugated horns\, and sophisticated micrometer positioners to perform the r
 elevant free-space calibration. Due to the Gaussian beam approximation ass
 umption\, these systems are referred to as quasi-optical systems. Measurem
 ent of material properties at terahertz (THz) frequencies has long been pe
 rformed in the time domain with use of ultrawideband pulses. In particular
 \, most materials\, especially organic ones\, have their vibration and rot
 ational modes in the THz band. The measurement accuracy of these systems i
 n the sub-THz regime is rather low and with poor resolution and the quasi-
 optical VNA systems represent a low-cost and higher accuracy alternative.\
 nWe present an easy-made setup with classic pyramidal horn antennas togeth
 er with a practical comprehensive calibration process and simple data extr
 action algorithm. The detailed data-extraction process\, measurement uncer
 tainty analysis\, and actual electromagnetic field pattern on the materia
 l plane\, are presented. The system uses compact-size mirrors to cover the
  wide frequency range from 50 to 500 GHz and a reliable simple calibration
  method without need for precise positioning.
LOCATION:PPB 019
STATUS:CONFIRMED
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