The role of impedance matching for power transfer efficiency in HF RFID systems An important aspect that should be taken into consideration when we talk about RFID systems is the antenna impedance matching. When a mismatch occurs in the antenna circuit, the power transferred from the RFID reader to its antenna is reflected, causing drastically decreasing of the tags reading distance. In this paper are analyzed some matching impedance circuits for an HF RFID reader antenna and are proposed few methods to achieve the desired impedance. The obtained results confirm that when a standard RFID reader antenna is used and the impedance isn’t matched, the maximum reading distance decreases up to 60% towards when is well matched.