基于相位编码体制的电离层垂测仪系统设计

Design of phase-code ionosonde system

该文介绍了一种电离层垂测仪的设计方法,分析了发射信号的选择要求,给出了实际电路模块。系统利用FPGA的IP核DDS产生正弦载波信号,经巴克码调相后,通过DAC和功放产生发射信号;接收机采用射频开关和直接ADC采样技术采集回波信号,避免了模拟正交解调时相位不平衡产生的问题。通过外场实验验证,表明该设计是切实可行,具有较好的实用价值。

The design method of an ionosonde system and transmit signal is introduced and practical circuit system is implemented. Source signal is generated by the IP core of DDS in the FPGA. Barker code is used as the modulating code to obtain the Phase-modulated signal and transimtted after DA converting and power amplifying.The echo through RF-switch is directly numeralized with ADC, Hence, the difficulty to garantee orthogonal between the signals from I and Q channels in hardware demodulation is avoided. The test experiment is performed with the ionosonde. Good result was obtained which verify the effectiveness of our method and practicability.