Patent ID: 7889057

Claim:
An RFID reader which reads data from an RFID tag using a wireless connection over a specified frequency bandwidth, comprising: a transmitting unit which sequentially and cumulatively synthesizes a specific frequency signal from frequency control signals generated every clock, mixes the synthesized specific frequency signal and a fixed frequency signal, and outputs an RF signal as a result, wherein the transmitting unit comprises: a frequency synthesizing unit which sequentially and cumulatively synthesizes the specific frequency signal from the frequency control signals generated every clock, and outputs the specific frequency signal; a fixed frequency generating unit which generates and outputs the fixed frequency signal, which is fixed to a specified level; a modulating unit which modulates the fixed frequency signal outputted from the fixed frequency generating unit with the specific frequency signal outputted from the frequency synthesizing unit, and outputs an RF signal as a result; and an amplifying unit which amplifies the RF signal outputted from the modulating unit to a specific level and transmits the amplified signal through an antenna, wherein the modulating unit comprises: a first phase shifting unit which phase-shifts the specific frequency signal by 90 degrees and outputs an in-phase signal as a result; a second phase shifting unit which phase-shifts the fixed frequency signal by 90 degrees and outputs a signal; a first mixer which mixes the in-phase signal from the first phase shifting unit and the signal output from the second phase shifting unit; a second mixer which mixes the fixed frequency signal and a quadrature-phase signal of the specific frequency signal; and an adding unit which adds a signal output from the first mixer and a signal output from the second mixer, and outputs the RF signal as a result.