Adun
Junior Member level 3
universal test fixture
Hi there, I have fabricated stripline bandpass filter on LTCC.
A pair of extra vias and pads are added to elevate the buried striline port up to the surface so that measurement can be done by UTF.
The performance of the filter looks fine under HFSS simulation.
However, when I do the actual measurement, the result is bad. Especially in the passband, S11 is only around -5dB, which is far from the -15dB from simulation. The cut off frequency and stop band attenuation are good though.
After discussion with my friend who has experience in using UTF, we think the reasons could be:
1. My feedline is too short. There should be at least 1/4 lamda length of feedline at each port. My design has only about 1/20 lamda feedline...
2. The filter is physically too small, i.e., 5 milimeter in length. That is too small for UTF, as the two jaws are too closed up when holding the filter. Hence huge coupling between the two jaws could be affecting thing.
3. The LTCC filter, being ceramics in nature, is too brittle and fragile. It simply breaks when we put it in the UTF.
Any input on why the measurement did work out please?
Any comments, suggestions, speculations or questions are all very appreciated.
Thank you very much!
Adun
Hi there, I have fabricated stripline bandpass filter on LTCC.
A pair of extra vias and pads are added to elevate the buried striline port up to the surface so that measurement can be done by UTF.
The performance of the filter looks fine under HFSS simulation.
However, when I do the actual measurement, the result is bad. Especially in the passband, S11 is only around -5dB, which is far from the -15dB from simulation. The cut off frequency and stop band attenuation are good though.
After discussion with my friend who has experience in using UTF, we think the reasons could be:
1. My feedline is too short. There should be at least 1/4 lamda length of feedline at each port. My design has only about 1/20 lamda feedline...
2. The filter is physically too small, i.e., 5 milimeter in length. That is too small for UTF, as the two jaws are too closed up when holding the filter. Hence huge coupling between the two jaws could be affecting thing.
3. The LTCC filter, being ceramics in nature, is too brittle and fragile. It simply breaks when we put it in the UTF.
Any input on why the measurement did work out please?
Any comments, suggestions, speculations or questions are all very appreciated.
Thank you very much!
Adun