单通道干涉仪测向系统中的高精度数字移相技术研究

A novel high-precision digital phase shifting technique in single-channel direction-finding interferometer

为解决单通道干涉仪测向系统中传统数字移相器对参考天线输出信号移相时移相精度不高的问题,基于直接数字频率合成技术(DDS)和混频技术,提出了一种新的数字移相技术。该技术采用两级混频结构,分别进行下变频和上变频。两级混频器的本振信号均由DDS信号发生器产生,通过调节本振信号的相位差,实现对一定频率范围内的输入信号进行0°~360°相位偏移。采用FPGA评估板、DAC FMC子卡、混频器、滤波器等模块制作了输入频率范围为432~434 MHz的移相器样机,对该方法进行了验证,实现了输入信号的0°~360°移相,移相步进小于0.09°,实测误差的均方根(RMS)小于0.8°。

Since traditional digital phase shifters are not accurate enough to phase the reference antenna’s output signals in single-channel direction-finding interferometers,we propose a novel digital phase shifting technique based on direct digital frequency synthesis(DDS)technology and mixing technology.A two-stage mixing structure is employed for down-conversion and up-conversion respectively.The signals of the two-stage mixer’s local oscillators are generated by DDS.By adjusting the phase difference of the local oscillators,the input signal can be shifted from 0 to 360 degree in a certain frequency range.The technique was validated by a prototype with the input frequency ranging from 432 MHz to434 MHz,which was fabricated using the modules of FPGA evaluation board,DAC FMC sub-card,mixer and filter,etc.The prototype achieved a phase shifting range of 0°~360°,a step of less than 0.09°,and the root mean square(RMS)value of measured error was less than 0.8°in the actual test.