We can reduce Side Band levels so, what is the difference between Time Modulated Antenna Arrays and general Antenna arrays which, can radiate by synthesizing the currents of elements?
An antenna array is a group of antennas connected and arranged in a regular structure to form a single antenna that is able to produce radiation patterns not produced by individual antennas. Antenna arrays are groups of isotropic radiators of electromagnetic frequency and energy.
However, TMAs (Time-modulated arrays) are electromagnetic systems whose radiated power pattern is controlled by the application of variable-width periodical pulses to the individual elements.
You can refer to the following links for more details
As you say, an array is a group of smaller antennas, but usually not isotropic antennas. I think there are no isotropic antennas. All that is needed is that the smaller antennas each have a wide enough beam to cover all the scan directions that are required for the array.
SBLs in Time Modulated Arrays are due to the inherently generated harmonics.
The "Target" should be the reduction of SBLs as low as possible, because energy is wasted in unwanted directions (because of harmonic patterns generated simultaneously with the desired pattern)
So, you can minimize your SBLs as low as possible.
There is no specific target for reduction of SBLs.
The main aim is to transfer the maximum percentage of power (increase the overall efficiency) to the desired radiation pattern, and minimize the radiation in any other directions.
You can any time refer my papers where I have simultaneously minimized the SLLs as well as SBLs of a Time-modulated linear array:
1) Article Optimal Pulse Shifting in Timed Antenna Array for Simultaneo...
2) Article Time-modulated Linear Array Synthesis with Optimal Time Sche...