The method described works with a linear array by using filters that strongly attenuate the edge elements at higher frequencies, so that the effective aperture is smaller at higher frequencies. For it to work at all the array has to be wide enough to give the beamwidth you want at the lowest frequency. That is not possible at 0 Hz, because the beamwidth is approximately wavelength/(array width), and at zero frequency the wavelength is infinite. Using fixed filters whose attenuation depends on their position in the array will also not work if you have a circular array and want to sweep the beam all around. In that case you will need to use different software filters for each element depending on the direction you want to scan. However, that is not difficult, as it can be included in the steering algorithm.

Okay, but please do you know any code for constant beamwidth of circular array? Thank you for your answer again