中文摘要：

针对星座卫星前向链路数字上调频部分最后一级梳状滤波器（CIC滤波器）频谱特点，设计了一个低通补偿滤波器，它能有效弥补CIC滤波器通带内的频谱衰减，两者合成一个较理想的低通滤波器，与前一级基带成形滤波器配合能有效抑制码间干扰，整体阻带旁瓣也较小。最后将该补偿滤波器与基带成形滤波器合成一个滤波器，与后面CIC滤波器组成二级内插，这样可以不用任何乘法结构单元实现基带成形，从仿真结果上看效果较好。这种频谱补偿设计的思路，可以推广应用在数字下调处理、陷波器、均衡等领域。

英文摘要：

In consideration of the characteristics of the last cascaded intergrator-comb （CIC） filter in the digital up converter （DUC） of the forward link of constellation satellite communication systems, this paper presents a practical design of a lowpass compensation filter. This filter can compensate the gain !oss in the pass band and compose an ideal low pass filter with the CIC filter. Also, it can help the pulse shapi~ng filter to reduce intersymbol interference （ISI） and side lobe in the stop band. The compensation filter works with the pulse shaping filter and the CIC filter to form a second order intepolator, thus th_e.base band shaping can be realized without any multiplication. The simulation results showa good performance. This idea of frequency compensation can be implemented in the digital down converter （DDC）, notch filter, equalization and so on.