Dielectric measurement method for water using FSMM - RF Cafe Forums

 Post subject: Dielectric measurement method for water using FSMM

Posted: Thu Dec 18, 2008 11:56 pm 

For dielectric measurement method for water using Free Space Microwave Measurement system (Microwave Non destructive Testing);

how to calculate/design the container of the sample holder for the water sample..the container was made by plexiglass.

if there are 3 types of water that will be used, then 7 samples of each types of water will be tested, is that possible to use only 3 container of sample holder?

 Post subject:

Posted: Fri Dec 19, 2008 12:14 pm 

Hi
It is not clear from your brief description how, and at what frequency, you are intending to do these tests.
Assuming you are using an open top plexiglass tank and measuring the Brewster angle, you will certainly need good microwave absorber to ensure a good depth of null as the Brewster Angle is reached. I only ever did water measurements in a closed transmission line/waveguide setup, but a colleague at Uni had endless problems with spurious reflections at X Band using an open radiator free space method, until we found good RAM absorber.
Three tanks should be OK, but you will need to rinse them out for each measurement to avoid any contaminant film across the top surface.
But maybe I don't understand your setup clearly enough.

 Post subject: Frequency range that will be used is 12GHz to 18 GHz

Posted: Wed Dec 24, 2008 3:17 am 

thank you for your explanation.
i will use the open top plexiglass tank. i want to measure the dielectric constant of the water samples at frequency of 12GHz to 18GHz (Ku Band). i will compute the complex permittivity of the sample from measuring the reflection coefficient (S11) and transmission coefficient (S21).

from the last question that i posted, i will use the free space measurement system. some of the equipments that involves including the Gaussian Optic Lens (GOA) and the Vector network Analyzer (VNA).