A PRECISION WAVE-GUIDE SYSTEM FOR THE MEASUREMENT OF COMPLEX PERMITTIVITY OF LOSSY LIQUIDS AND SOLID TISSUES IN THE FREQUENCY-RANGE 29-GHZ TO 90-GHZ .2. THE LIQUID-SYSTEM FOR 90-GHZ, HIGH-FREQUENCY CELL DESIGN

A W-band waveguide system is described which enables the complex permittivity of high-loss liquids to be measured accurately at a spot frequency of 90 GHz. Mechanical restrictions are overcome by using an oversized rectangular cell. Data are presented and the experimental errors considered. The present work compares results found from an oversized rectangular waveguide cell with those from a standard circular waveguide cell and an E-band rectangular waveguide cell, operated at the upper limit of its frequency range. The results for a range of liquids are comparable within experimental errors.