Electromagnetic Absorption Characteristics of Conductive Polymer Composites
Conductive polymer composite absorption depends on balancing complex permittivity and skin depth to eliminate surface reflection and satisfy radiated emission limits.
Quasi Optical Free Space
Meaning
Millimetre wave material characterization setups employ focused beam paths to measure dielectric properties without physical contact. Researchers use a quasi optical free space system to evaluate the permittivity of radome materials and substrate panels at high frequencies.
Measurement Setup
High gain horn antennas are combined with focusing lenses to create a parallel beam that passes through the sample plate. This sample is held in a fixture mounted between the lenses to ensure the wave hits the material at a right angle. The absence of enclosing metal walls reduces the calibration issues common in waveguide cavities, which simplifies the characterization of flat panels over broad frequency ranges.
Signal Propagation
Wave propagation through the material sample alters the phase and amplitude of the transmitted electromagnetic beam. S-parameters are gathered across a wide frequency band by a vector network analyzer connected to the horn antennas. This data is converted mathematically into complex dielectric constants and loss tangent figures.
Antenna Array
Lens focus must be carefully aligned to avoid diffraction losses at the edges of the material sample under test. If the sample plate is too small relative to the beam spot size, leakage around the borders degrades the measurement accuracy. This requirement limits the test method to flat, uniform samples of a minimum required size.