Since the impedance of the chip is Zc = 14.8-j127.1Ω the impedance of the antenna should be 14.8+j127.1 Ω,which is conjugate complex to the chip impedance From Fig.14,it can be seen that at 921 MHz, the impedance of the antenna is approximately Za = 12.4 + j128.4 Ω, which is 98% match to the chip impedance. In order to calculate how much the impedance of the antenna is matched to the chip impedance, the formula of power transfer coefficient, τ in (2) is used.