基于中波导航机的“北斗二”差分数据传输研究

Research on BD2 Differential Data Transmission Based on Non-Directional Beacon

针对"北斗二"卫星导航系统的差分数据传播需求,提出了在中波导航机的发射信号中进行差分信号传输的方案.分析了DPSK调制对现有机载无线电罗盘的工作带宽、定向及台识别等性能指标的影响.分别在有、无噪声干扰两种条件下,对采用DPSK调制的差分数据传输特点进行了对比分析,得出有噪声干扰条件下进行差分信号传播的特点.研究了在中波导航机发射点划信号时间内,AM调制信号对DPSK的解调以及误波特率的影响,并提出了利用差分数据信号与音频信号进行同步来克服相应的影响.仿真结果表明,DPSK不会对现有机载无线电罗盘的基本功能产生影响,利用差分数据信号与音频信号进行同步的方法进行"北斗二"差分数据传播可以有效克服AM调制对DPSK解调的影响.

The differential data transmission method based on Non-direction Beacon（NDB） for the BD2 Global Navigation Satellite System （GNSS）was proposed. The DPSK signal＇ s influences on the performance of airborne radio compass including bandwidth, direction finding and beacon recognition, were analyzed in detail. The characteristics of DPSK-based differential data transmission were compared under both the noise-free circumstance and the additive WGN （White Gaussian Noise） circumstance, and the corresponding conclusions were drawn explicitly. During the period of Morse codes transmission, the influences of Amplitude Modulation （AM） on the demodulation process and the Baud Error Rate （BER） of DPSK were also analyzed, and the synchronization between DPSK and the audio frequency signal was proposed to ameliorate the influences mentioned above. The simulation results are given that, the beacon identification function and the direction finding of the radio compass cannot be influenced by DPSK modulation,and the synchronization between DPSK and the audio frequency signal is an effective approach to overcome the AM＇s influences on the DPSK demodulation.