A majority of existing single-anchor localization algorithms make use of antenna arrays or special antenna systems. However, the need for specialized antenna systems incurs higher costs, complexity and power consumption. This paper presents a novel single-anchor localization algorithm, which does not require antenna arrays or special antennas. The algorithm is implemented in a two-robot system, where one of the robots acts as the anchor and the other acts as the target. The localization algorithm uses velocity measurements of each robot and distance measurements between robots. Using the change in distance between the robots and the velocity of the target robot relative to the anchor robot, the target robot can be localized relative to the anchor robot. The localization algorithm uses a Kalman filter as a state estimator of the movement of the target robot and a Savitzky-Golay filter to filter the distance measurements. A simulation with Gaussian noise in the distance measurements is performed to display the impact of the filtering methods. Another simulation showed an average localization error of 1.38 meters when the distance measurements are acquired through RSSI measurements, which is comparable to existing RSSI-based localization methods.