Header menu link for other important links
Tailoring Antenna Focal Plane Characteristics for a Compact Free-Space Microwave Complex Dielectric Permittivity Measurement Setup
, Pakkathillam J.K., Sivaprakasam B.T., Poojali J.,
Published in Institute of Electrical and Electronics Engineers Inc.
Volume: 70
This article presents a compact precision free-space microwave measurement setup with a choice of three dielectric lenses to tailor the antenna focal plane characteristics for extracting complex dielectric permittivity of small samples. Custom designed spot-focusing horn antenna pairs were used to achieve a compact setup with antenna separation distance, 2f l : 4λ c-8λ c and focal spot size, fs : 1λ c-1.5λ c , where λ c is the wavelength at center frequency. Using the compact free-space setup, relative complex permittivity (j) was extracted over 8-12 GHz for low-and high-loss dielectrics with lateral dimensions, 3.3 λ c× 3.3λ c and 10 λ c × 10 λ c. For large materials under test (MUTs), i.e., 10 λ c × 10 λ c , measurement accuracy in dielectric constant, Δ% was <0.65% and ≤1.14% for low-and high-loss dielectrics, respectively. For smaller MUTs ( 3.3 λ c × 3.3 λ c ), Δ % was <0.89% and ≤2.29% for low-and high-loss MUTs, respectively. The error in loss tangent ( Δ) varied over 0.002-0.016 and 0.015-0.056 for large ( 10 λ c × 10 λ c ) and small MUTs ( 3.3 λ c × 3.3 λ c ), respectively. For large MUTs, biconvex lens pair with the smallest f-s ( 1 λ c ) and f-l ( 4 λ c ) among the three lenses yielded the best accuracy in dielectric constant due to tight field focusing at the focal plane. The plano-convex lens pair yielded the best accuracy in loss tangent for large MUTs due to slow variation in the phase of the local plane wave. By tailoring antenna focal plane characteristics, a compact free-space setup that is 6×-10× smaller than the classical setup for handling MUTs that are 1/5th of the size used in classical setup is demonstrated without compromising the measurement accuracy. © 1963-2012 IEEE.
About the journal
JournalData powered by TypesetIEEE Transactions on Instrumentation and Measurement
PublisherData powered by TypesetInstitute of Electrical and Electronics Engineers Inc.
Open AccessNo