基于FPGA协同控制的无人机多模终端射频功率实时校准系统设计

摘要:

无人机多模终端可支持多种频段通信模式,保障无人机在不同环境下与外部控制中心通信链路的稳定。但多模终端多种模式信号间相互作用产生的互调失真,会降低射频功率校准后的通信质量系数。为此,本研究设计了一种高效、精确的基于FPGA协同控制的无人机多模终端射频功率实时校准系统。硬件系统经过优化设计,包括改装射频功率测量仪以支持多终端同步测试,加设无人机蜂群自组网多模终端信号滤波器,过滤多模信号中的干扰成分,以减少互调失真对射频功率测量的干扰,构建包含射频功率放大器、数字步进衰减器及校准电路的射频功率校准执行器,增设以FPGA为核心的主控元件实现智能化协同控制,实现校准硬件系统的优化。通过模拟多模终端工作过程,确定其发射和接收终端校准目标,测量终端实时射频功率。经硬件优化和校准目标的准确确定,对比实时射频功率与校准目标,可得出含精确校准量的控制指令,执行该指令实现射频功率校准功能。通过系统测试实验得出结论:优化设计系统校准后的信号互调失真产物功率电平降低了7dBc,综合静态和动态环境,优化设计系统的射频功率校准误差减小2.53dBm,在校准系统作用下,无人机多模终端通信质量系数明显提升。

Abstract:

The multi-mode terminal of the drone can support multiple frequency band communication modes, ensuring the stability of the communication link between the drone and the external control center in different environments. However, the intermodulation distortion generated by the interaction between multiple mode signals in multi-mode terminals will reduce the communication quality coefficient after RF power calibration. Therefore, this study designed an efficient and accurate real-time RF power calibration system for multi-mode terminal of unmanned aerial vehicles based on FPGA collaborative control. The hardware system has been optimized and designed, including the modification of an RF power measuring instrument to support multi terminal synchronous testing, the addition of a drone swarm self-organizing network multi-mode terminal signal filter to filter out interference components in multi-mode signals to reduce the interference of intermodulation distortion on RF power measurement, the construction of an RF power calibration actuator including an RF power amplifier, a digital step attenuator, and a calibration circuit, and the addition of a main control component with FPGA as the core to achieve intelligent collaborative control and optimize the calibration hardware system. By simulating the working process of a multi-mode terminal, determine the calibration targets for its transmitting and receiving terminals, and measure the real-time RF power of the terminal. Through hardware optimization and accurate determination of calibration targets, comparing real-time RF power with calibration targets, control instructions containing precise calibration quantities can be obtained, and the RF power calibration function can be achieved by executing these instructions. The conclusion drawn from the system testing experiment is that the optimized design system reduces the power level of signal intermodulation distortion products by 7dBc after calibration. Taking into account both static and dynamic environments, the RF power calibration error of the optimized design system is reduced by 2.53dBm. Under the action of the calibration system, the communication quality coefficient of the multi-mode terminal of the drone is significantly improved.