5G antennas (or antenna arrays) are designed to generate dedicated stream of data to every single user with more capacity, speed and low latency rate. Depending upon the direction of the user demanding Internet access, the beam can be steered in that direction. However, the apparition of side lobes in such systems can be menacing. What is the SLL (side lobe level) target required for 5G applications ?
Dear Mohamed Lamine Tounsi ,
Welcome!
The problem which you raised concerning the radiation pattern of antenna array to direct the maximum possible radiations towards a specific user and then try to decrease the radiation of the side lobes to the other users to achieve the minimum level of interference.
It is so that an array of antennas has a major lobe, side lobes and nulls where the radiation can be considered at its lowest value.
Physically as one narrows the major beam the side lobes grow.
So, in order to reduce the sidelobes radiation one has to restrict the number of the elements in the array.
But this is not a smart solution.
The solution to this problem is to position the nulls in the directions of the other users. This will be a wise solution.
Best wishes
Dear Abdelhalim,
Thank you for your response. As you know, in 5G multibeam antennas, the tilt is controlled electronically depending on targeted user. So, the SLL cannot be easily evaluated because the side lobes level vary versus the user direction. Are there general methods which allow to reduce the SLL whatever this direction particularly in 5G ?.
best regards
I don't know the limitation set in 3GPP specs for the side lobe level, but regardless of any communication standards, we would like to be able to create a very narrow beam and very small sidelobes. These two are always conflicting. However, there is a way to choose an appropriate trade-off between these two, WINDOWING the array in the spatial domain.
In reality, you multiply the N-element array weights with a finite length-N window w(m). If this w(m) is all ones, i.e. uniform weighting or uniform window, there is no amplitude tapering, and the sidelobes are always 13 dB lower than the main lobe.
Alternatively, there are well-known filters such as Dolph-Chebyshev, Taylor-Kaiser, Binomial, etc. that can be used instead of a uniform filter. In fact, Binomial filtering results in no sidelobes at all, however at the expense of a large beamwidth. DC and TK filters can have any sidelobe levels by tweaking their parameters.
You can check Chapter 23 of Prof. Orfanidis' book for further discussion on the topic:
http://eceweb1.rutgers.edu/~orfanidi/ewa/ch23.pdf
Hopefully, that clarifies the concept.
Mohamed Lamine Tounsi try to use the concept of sparse array arrangement or read about non- uniform array/aperiodic array and Fermal spiral array concept. this method proven help to reduce the SLL by controlled the array elements.
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