I. Introduction
Short-range communication attracts lots of applications as cable replacement, personal ad hoc network, and digital convergence. In the future, more and more electronic devices will try to connect with each other by using short-range wireless communication chips. Bluetooth is one of such products serving as a short-range radio link intended to replace cables among electronic devices [1]. Bluetooth uses Gaussian Frequency Shift Keying (GFSK) [2] as the modulation, whose 3dB bandwidth-symbol time product is 0.5, FM modulation index is between 0.27 to 0.35, and Symbol rate is 1 Ms/s.