https://asp--eurasipjournals-springeropen-com.translate.goog/articles/10.1186/1687-6180-2014-159?_x_tr_sl=en&_x_tr_tl=ro&_x_tr_hl=ro&_x_tr_pto=op,sc https://www.radartutorial.eu/07.waves/wa51.en.html