An autoreconfigurable circular polarization (Auto-RCP) antenna is proposed for enhanced radio frequency identification (RFID) coverage. It consists of a high-efficiency rectifier, directional coupler, circularly polarized antenna, and autopolarization reconfiguration circuit. During the reader operation, the rectifier samples the reader's power signal to generate a pair of control signals synchronized with the duty cycle. This pair of signals drives an RF switch to exchange the circular polarization between pulses. In this way, autoswitching functionality between left-hand circular polarization and right-hand circular polarization is achieved, eliminating the need for manual adjustment or programmable control. To demonstrate the proof-of-the concept, a prototype validates performance through simulation and measurement. Compared to the fixed counterparts, at certain distance, the Auto-RCP antenna achieves 30% higher RFID tag detection rates and improves 30% detection rate beyond in operational power range. The Auto-RCP antenna provides robust, adaptable wireless connectivity between RFID readers and tags, enhancing functionality for current and emerging RFID applications in a cost-effective package.