We combine DC bias and RF signals at 10mK using a bias-tee before sending them to the chip. Infrared filters are used at both the common port of the bias tee and the readout line to effectively absorb infrared radiation. Furthermore, a cryogenic u-metal shield is utilized on the sample port for shielding purposes. This combined solution can isolate infrared and magnetic radiation remarkably and is consistent with observations reported by other research groups.