A receiver receiving a Radio Frequency (RF) signal and generating a baseband signal is provided. An RF module receives the RF signal and down convert the RF signal according to a first oscillation frequency to generate an Intermediate Frequency (IF) signal. An IF module is coupled to the RF module and arranged to receive the IF signal and down convert the IF signal according to a second oscillation frequency to generate the baseband signal. A calibration module is coupled to the RF module and arranged to calculate the IF signal according to a third oscillation frequency to detect an I/Q mismatch, and generate an adjustment signal, accordingly, to calibrate the I/O mismatch.