In engineering, ami or hdb3 code digital signals are generally rectified to obtain a unipolar return-to-zero code with a duty cycle of 0.5 (rz|τ=0.5ts). The power spectrum of this signal is also given in Figure 2. Since the rectified ami and hdb3 codes contain the discrete spectrum fs, a frequency-selective network can be used to obtain a sine wave with a frequency of fs. After shaping, limiting, and amplification, the bit synchronization signal can be obtained.