[IEEE 2016 13th International Conference on Modern Problems of Radio Engineering. Telecommunications and Computer Science (TCSET) - Lviv, Ukraine (2016.2.23-2016.2.26)] 2016 13th International Conference on Modern Problems of Radio Engineering, Telecommunications and Computer Science (TCSET) - Optimal algorithm for estimation of radio brightness of an extended source of radio thermal radiation in the ultra-wideband radiometric complex with a three-element-antenna system