This thesis proposes a new baseband clock recovery algorithm for π/4-QPSK modulated signals. Conventional non-data-aided clock recovery methods for π/4-QPSK modulated signals are based on square devices. The proposed algorithm uses absolute rectifier and special pattern of the phase transition of π/4-QPSK modulated signals. This paper shows the simulation results of this clock recovery algorithm and the jitter performance. The jitter performance of the proposed algorithm is superior to the conventional squaring algorithm.