针对在定点运算平台(比如可编程逻辑器件FPGA)上进行数字下变频的过程中截位操作不当产生的误差会引起输出的基带信号出现零点漂移现象,造成接收机动态范围下降的问题,文中分析了数字下变频中的直接截位产生零点漂移现象的原因,并提出了趋向截位和舍入截位两种截位方法,可以使截位误差的均值近似为零,有效地抑制了零点漂移现象。

DDC is the key technique of acquiring baseband signal in the digital radar receiver. The data calculated by digital down conversion (DDC) need to be truncated in the fixed-point platform such as field programmable gate array (FPGA). However, the error of inappropriate truncation may result in the zero-drift in the output signal and leads to the degradation of dynamic range of radar receiver. In this paper, the zero-drift caused by direct LSBs truncation is analyzed, and the tending truncation method and the round-up truncation method are proposed. Both of these methods can make the truncation error approach to zero and restrain the zero-drift effectively.

TN957