Patent ID: 7728714

Claim:
A method of detecting an End of Signal (EOS) of a response signal from a Radio Frequency Identification (RF-ID) tag which is received in response to a first command signal transmitted to the RF-ID tag, to enable transmission of a next command signal by an RF-ID reader within a predetermined period of time, the method comprising: obtaining, by the RF-ID reader, a threshold based on a continuous wave signal generated by the RF-ID reader in a first time section where there is no response signal; sliding, by an RF-ID reader, a sliding window in a second time section where the response signal is received and measuring a variance value of the sliding window; comparing, by the RF-ID reader, the variance value within the sliding window with the threshold and counting a number of times that the variance value is smaller than the threshold; and determining, by the RF-ID reader, the EOS of the response signal if the number of times exceeds a predetermined value; wherein the first time section is a time section between the transmission of the first command signal and the reception of the response signal, wherein the sliding window is a window at a predetermined time interval to measure the variance value, and wherein the variance value is a variance regarding a frequency of the response signal.