Radio-frequencies (RF) antennas for use in micro-localization systems are described. The RF antennas described herein may enable localization of objects with high resolutions, such as in the order of one centimeter or less. The RF antennas may be further configured to reduce range error variability across different directions, so that the accuracy of a micro-localization system is substantially the same regardless of the position of the object. An illustrative RF antenna includes an emitting element having first and second conductive traces patterned to reduce the angular impulse delay variability of the RF antenna. The first conductive trace may form a first arm of a spiral and the second conductive trace may form a second arm of the spiral. At least one parameter of the spiral may be selected to reduce the angular impulse delay variability of the RF antenna.