Today I received some Polyimide tape from China. This should make it possible to lower the resonant frequency of Microstrip and Stripline filters, applying the tape to the resonators.
This should increase the dielectric constant of the surroundings of the resonator strips, thereby lowering the velocity factor , effectively electrically lengthening the resonators.
I have seen this tape used in a TV satellite LNB for lowering the band pass filter frequency. My question is how much loss, (i.e. lower Q) this adds to the filter.
I was promised some PTFE (Teflon) tape from a friend (I suspect with lower losses), but we have not yet had time to get it to me. He has some stuff that I can measure, so he wants to come here, and bring the tape.
The coming week end will be quite busy, but after that I should be able to test the tape for losses, and frequency change of the filters I already have.
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