Patent ID: 8284032

Claim:
An apparatus for signal detection of a reader in a Radio Frequency IDentification (RFID) system, the apparatus comprising: a low-noise amplifier for low-noise amplifying a received signal of an antenna; a receiver unit for detecting a Continuous Wave (CW) signal and a tag signal in the low-noise amplified signal; a transmitter unit for frequency up-converting an input signal, and outputting the up-converted signal; a Phase Locked Loop (PLL) for generating a frequency signal according to a transmission signal band or a reception signal band, and transferring the generated frequency signal to the transmitter unit or a receiver unit; a receiver unit switch for connecting the receiver unit with the low-noise amplifier or a directional coupler; an antenna switch for connecting the antenna with the directional coupler or the low-noise amplifier; and a controller unit for controlling a frequency of the frequency signal generated by the PLL, turning off transmission power in a case of a Listen Before Talk (LBT) scheme, controlling the receiver unit switch to connect the receiver unit with the low-noise amplifier, controlling the antenna switch to connect the antenna with the low-noise amplifier, and determining if a corresponding channel is an idle channel, by using a power value of the signal output from the transmitter unit, wherein the controller unit controls the PLL to frequency shift a signal of the corresponding channel by a prescribed frequency or converts a frequency response characteristic of a Direct Current (DC) remover provided in the receiver unit into a low-pass filter characteristic corresponding to a fundamental frequency of the corresponding channel, thereby enabling the receiver unit to detect the signal of the corresponding channel where the LBT scheme is to be performed.