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during non contact dielectric measurement of any sample using VNA and patch antennas,should the antenna dielectric be taken into consideration for calculations? i want to use a ultra wide band patch antenna but i have no idea about its dielectric or material it is made of. Usually which material is used for making UWB patch antennas operating in GHz?

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The best substrate dielectric measurements are made by etching your own test pieces onto the substrate under test. That way, you have only one material in play.

It sounds like from your question, you are using patch antennae to couple to a substrate under test. What the VNA will measure is the perturbation of the patch antenna when loaded by the substrate under test. You need to analyse the whole system to get any meaning results from the measurements. Depending on the measurement geometry you use, this may be more or less sensitive to geometry and analysis errors. That's why it's better to use only the substrate you are testing.

Rogers 4350 is the 'go to' material for many applications in the GHz. It's readily available, and can be processed using the same workflow as FR4, and indeed is frequently bonded with FR4 to make a hybrid multi-layer board.

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  • \$\begingroup\$ i want to measure dielectric of a liquid say water then how should the test setup be? suppose i place the water filled test tube in between two antennas and then measure its parameters using VNA. how can i get only the dielectric value of the liquid and eliminate the effects of other materials like antenna and coaxial cable and connectors. \$\endgroup\$
    – V.Jhanjee
    Commented Dec 29, 2016 at 12:44
  • \$\begingroup\$ is there any specific method or formula to calculate the dielectric of liquid that is based on this antenna method? \$\endgroup\$
    – V.Jhanjee
    Commented Dec 29, 2016 at 12:46
  • \$\begingroup\$ It's simply a perturbation method, where you measure your test cell full of air, then full of liquid. The air measurement is, as much as anything, to make sure you have calculated correctly what it should be for air. Cables and connectors are 'automatically' eliminated if they match the impedance of the VNA. If you have to ask that bit, then you indeed have a long learning curve ahead before you can make microwave measurements of complicated things. The simplest is to cut the end off a cable, dip it into the liquid, measure S11. Analyse that before you try anything harder. \$\endgroup\$
    – Neil_UK
    Commented Dec 29, 2016 at 12:55
  • \$\begingroup\$ thanks for responding but i do not want to do open ended coaxial method. i want to do non contact free space dielectric measurement. \$\endgroup\$
    – V.Jhanjee
    Commented Dec 30, 2016 at 5:19

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