An instrument for measuring permittivity and loss tangent of substrate

Discussion in 'Wireless & RF Design' started by PersianEngineer, Oct 25, 2014.

  1. PersianEngineer

    Thread Starter New Member

    Aug 15, 2013
    We need to buy an instrument for measuring permittivity and loss tangent of antenna substrate for our lab. The frequency scale of GHz around max 10 GHz or more.
    The budget is around US$15000.
    Could you recommend a device for this purpose (with brand and model)?
  2. BR-549

    Distinguished Member

    Sep 22, 2013
    Would you please explain loss tangent of antenna to me?
  3. b1u3sf4n09


    May 23, 2014

    He is referring to the resistive losses of the antenna. A perfect antenna would have only reactive elements, which would not result in any power loss at the antenna during transmission/reception.
  4. BR-549

    Distinguished Member

    Sep 22, 2013
    Are you purchasing or manufacturing the substrate?
  5. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    I would think a network analyzer with the proper jigs would be appropriate. You MIGHT be able to do that for $15,000, but it would be a challenge.
  6. BR-549

    Distinguished Member

    Sep 22, 2013
    Permittivity changes with many factors... temp, humidity, pressure, stay fields and other.
    If you were publishing the results, an environmental testing unit would be needed.

    If you just need to know how a certain substrate will react with an antenna, I would suggest a scaled down version of a free space capacitance testing jig.
    With properly constructed jig.....under hard vacuum, you should see close to free space capacitance.......your jig is now calibrated.
    Replace vacuum with substrate. Sweep input plate and measure output plate. Plot capacitance vs frequency. You should be able to correlate the capacitance with the permittivity.

    What about permeability? And I still can't find anything about tangent loss.

    Unless you are testing substrate for a living......maybe it would be best to mount and power the antenna and then measure field strength.

    No test or data is better than use.
  7. BR-549

    Distinguished Member

    Sep 22, 2013
    I know you were in a hurry, but better late than never.

  8. alfacliff

    Well-Known Member

    Dec 13, 2013
    we used to use an x band signal generator with two known gane horns. generator into one, small space, and detector on the other. since the permitivity, dielectric loss, and loss are known for air, it is fairly easy to see the change when a sample is inserted into the space between horns. at lower frequencies, rf loss in insulators can be aproximated with a microwave oven, put the sample in the oven, along with a glass of water ( to absorb excess energy) and run the oven a while. if the sample heats up, it is absorbing rf energy.