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StatusOngoing
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Status date2024-04-22
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Activity Code7A.071
This project activity aims at developing a C-Band reconfigurable notch filter breadboard, suitable for Very Small Aperture Terminal (VSAT) applications. A review of reconfigurable notch filter concepts suitable for C-Band implementation will be carried out with emphasis on filter and tuning concepts offering high quality factor and low complexity. The activity trades off and selects at least one baseline concept for the reconfigurable notch filter and produces a detailed design of a breadboard based on the selected baseline. Finally, a filter breadboard is manufactured and tested. The activity seeks also synergies with other technologies, products, and developments (outside the scope of this activity), related to sub-6GHz interference mitigation strategies.
The main challenge of TUNO project is to fulfil both the in-band low-loss and the out-of-band high-rejection requirements. The selection of advanced technologies forces to push at the limit some fabrication processes introducing several manufacturing challenges both in term of outcomes and achievable tolerances.
An electronically reconfigurable notch filter would be an optimal solution in the Sub-6GHz interference mitigation toolkit. Agility in suppressing the 5G interference would be obtained real-time, depending on the varying interference conditions. This in turn would remove the need of filter customization, switching networks and/or manual feed adjustments, thus simplifying the operation of VSATs. A fully automatic interference mitigation strategy could also be considered, where the notch filter is continuously adjusted electronically, while the interference is being monitored by a spectrum analyser.
The TUNO prototype is based on Nth mechanical tunable notch filter composed by N adjustable resonators whose resonance frequency can be changed in frequency by a motor and a control board.
Nowadays, part of the sub-6 GHz 5G spectrum overlaps with the standard and extend C-band (3.4 ÷ 4.2 GHz), which is used by Very Small Aperture Terminals (VSATs) for Maritime and Fixed Satellite Services. The sub-6GHz 5G carriers are narrow band (<100 MHz), can fall very close to the satellite C-Band (up to 20MHz), and are much stronger than signals received from a satellite. Moreover, these 5G interferers are difficult to predict, as their magnitude, frequency and timing depend on the actual VSAT location and operating conditions. Other sources of sub-6GHz variable interference do exist, such as airplane altimeters and high-power radars.
In this scenario of widespread deployment of terrestrial 5G systems, a large user base of C-Band VSATs is severely affected by adjacent-channel interference and Low-Noise Block (LNB) saturation. The use of a filter in front of the LNB input can protect the satellite carriers within its passband and isolate unwanted carriers located out of the passband. Unfortunately, conventional filter solutions require a high degree of customization and possibly a frequent replacement, due to the variable nature of sub-6GHz interferers. Filter replacement is a major concern for many C-Band VSAT users, as it requires manual feed adjustments in high-risk situations (e.g., ship decks, high-rise buildings).
The entire work of the project is organized and divided into two technical parts.
In the first parts, the most promising technology concepts are planned to be tested at BB level, leading to the final design concept selection. In the second part, elegant BBs close to a final product have to be designed and subjected to an extensive environmental and RF test campaign.
The project is at TRB. The FR meeting of the project is scheduled by 2025.
