determining dielectric constant of unknown material

with only a scalar network analyzer
and an anechoic chamber with pattern recorder

currently deciding on an approach
but was wondering if anyone else might have some thoughts on this

thanx in advance

gb

Is your material in bulk form or is it a printed circuit card? If bulk you could use your chamber to measure the transmission of a plane wave through the material. When it is a half wave thick there is no reflection and the transmission has a local maximum.

For printed circuit material, you can use it as a capacitor. After finding the capacitance you work backwards from the formula to get e-sub-r.

the material will be used for printed circuit style design
housing a patch antenna and its feeding network
material was chosen by customer however
this material is not a typically used in microwave applications
ie there is no dielectric constant data taken for microwave frequencies

sorry forgot to mention
that i have the material in bulk form

i was thinking along the plane wave idea
however the capacitive approach sounds reasonable also

One possible problem you may face in the antenna use is that the material may have a high loss which will drastically reduce the antenna efficiency. Try it out. Your customer may want to change the material once they find the extra cost of higher power amplifiers to get the same radiation field as from a good antenna is more than the cost of using good microwave material.

I normally use waveguide for a chunk of dielectric and see the refraction.
This technique dose not need a network analyzer.

And one of my friend uses horn antennas to mesure the permittivity of a sheet dielectric with a ground plane (suitable for patch antenna and high frequency). May be you are also interested in this method.

Scalar network analyzer may not give you the imaginary component.

Here is a link which I posted some time ago. You may find what you are looking for there

http://www.boulder.nist.gov/div813/r...lications.html

Timelord