Design of Ranging Communication Coding and Noise Suppression Methods in Space Gravitational Wave Detection

A ranging communication system is a key technology for achieving precise ranging and scientific data exchange in space gravitational wave detection, with the aim of realizing the symmetry of interferometer arms. This system is integrated into the phase measurement payload, the 'phasemeter'. Achieving high-ranging accuracy and low-bit error rate communication while mitigating the impact of phase noise has become a focus of current research. This paper starts with the coding methods for ranging communication and analyzes phase modulation noise based on Binary Phase Shift Keying (BPSK). The study found that the main lobe phase noise caused by BPSK modulation is approximately 158 mu rad/Hz, which is two orders of magnitude higher than the phase-tracking criteria for gravitational wave detection. To address this, this paper proposes a Bit-Balanced Code (BBC) sequence design and optimization method aimed at eliminating main lobe noise. The experimental results show that the optimized BBC sequence improves the metrics of even autocorrelation, odd autocorrelation, maximum spectral amplitude, and even cross-correlation by 7.17, 2.83, 1.22, and 7.16, respectively, compared to the original sequence. Furthermore, experiments have demonstrated that the BBC sequence is insensitive to random data and can achieve dynamic bit balancing to eliminate the DC component. The proposed BBC sequence design method can serve as a reference for technologies related to space gravitational wave detection.