Hi,
Many wideband DVBT antennas has integrated filter for filtering LTE and 5G signals. I have disassembled few of them and found internal filter inside antenna boom. Some kind of filtering can be done by not having resonators for specific length. Internal filter will have insertion loss, while specific construction I believe will be better, because no filter insertion loss. Is there any measurement methods to do to know why antenna filtering (due to construction or due to discrete component filter hidden). Let's treat antenna as black box and we need to determine filtering type by not seeing antenna construction.
Thank you in advance
Dear Audrius Merfeldas ,
I suppose this has already occurred to you... but a somewhat rudimentary way, at least to get a rough idea, is to do a frequency sweep over a wide frequency spectrum and measure the s11.
If there is any odd resonance or a band where the s11 tends to 0 dB, it may be an indication that there is some kind of filtering going on.
Whether a log-periodic LDPA antenna has an internal filter or filters due to its construction depends on the specific antenna. Some log-periodic LDPA antennas have an internal filter that is designed to reject unwanted frequencies. This filter is typically located at the feed point of the antenna. Other log-periodic LDPA antennas do not have an internal filter, and instead, the filtering is done by the physical construction of the antenna. The spacing of the dipole elements in the antenna can act as a filter, rejecting frequencies that are not in the desired band.
To know whether a specific log-periodic LDPA antenna has an internal filter, you can consult the product documentation or contact the manufacturer.
Here are some of the things to look for in the product documentation or when contacting the manufacturer:
- Does the product documentation mention an internal filter?
- If so, what frequencies does the filter reject?
- If the product documentation does not mention an internal filter, ask the manufacturer if the antenna has any filtering properties.
In addition to the product documentation, you can also look for clues about the presence of an internal filter by examining the antenna itself. If the antenna has a metal housing, it is more likely to have an internal filter. You can also look for a small, black box near the feed point of the antenna. This box may contain the internal filter.
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