The Tore-Supra doppler reflectometer (TSDR) aims at measuring the poloidal wave number spectrum (k spectrum) of the density fluctuations. To evaluate the performance and the sensitivity of the TSDR, simulations were made using a global full-wave code. The TSDR modeling with a finite-difference time-domain scheme and the required constraints of the simulation are presented, namely the account of the real size of the system: Distance horn plasma and plasma size. Particular attention is given to the role of the radiation pattern both on the TSDR spatial resolution and the wave number detection.