This paper presents a low cost system based on FPGA (Field Programmable Gate Array) technology to obtain the localization and orientation of a robot in a 2D indoor space. The system is based on the measurement of the propagation delay of an ultrasonic signal between known points, implementing a new DTOA (Difference Time Of Arrival) technique. The extracted information is used to estimate the reception angles of an ultrasonic signal, instead of calculating the intersection of hyperboloids used in classical DTOA techniques. Therefore, the computational cost of the algorithm is notably reduced.