This paper presents a method for predicting the angle-of-arrival (AOA) using ultrawideband time-difference-of-arrival technique, when the received signal is corrupted by antenna noise. To predict the accuracy of the AOA, the probability density function of the estimated AOA and the standard deviation (rms error) are derived. Numerical simulations and measurements for AOA, in thermal noise conditions, are carried out for three different SNRs. The rms error of the measured and simulated AOAs is then compared with the theoretical standard deviation. The measurements are done with two ridged-horn antennas placed on a turn-table and the received signals are recorded (50 times) at intervals of 1° between -20° and +20°. Accuracy of the proposed AOA estimation model is validated by simulations and measurements.