In these days, radio frequency identification (RFID) has been widely believed that it brings a revolution in the main distribution industry substituting barcodes. Especially, as the demands for mobile RFID applications increase, there has been strong need for integrating RFID system keeping small size and low power dissipation. Thus, digital, RF, and analog chips have been integrated into one package under the name of system-in-package (SiP). However, there are various problems to integrate the RFID system into a package. One of those problems is undesired noise coupling from digital to analog circuitries through power distribution network (PDN). In this paper, we analyze the effect of power distribution network design in mixer output by using both simulation result and measurement result.