Millimeter Wave Complex Permittivity Measurements of High Dielectric Strength Thermoplastics

This paper presents for the first time the complex dielectric permittivity and loss tangent measurements for a selection of advanced polymer-based thermoplastics in the Q-band, V-band and W-band frequencies. These plastics are reported to have exceptional mechanical, thermal and electrical properties and are extensively used as electrical insulating materials, often operating at high voltages. With this view in mind, we have studied their dielectric properties with high-power sources in the millimeter wave range. The measurements have been performed using a broadband quasi-optical millimeter wave spectrometer with a backward wave oscillator (BWO) as a nondestructive high-power tunable source of coherent radiation. Values of real and imaginary parts of dielectric permittivity and loss tangent of the materials have been accurately calculated from the transmittance spectra.