The digital channelizer processing on-board is adopted by the broadband flexible transponder, which is the next generation communication satellite payload. This payload can flexibly transpond signals within any frequency band and any bandwidth, which can not be well solving by the traditional payloads. Based on analyzing performance of the modulated filter banks in flexible transponder, an algorithm for designing prototype filter with Near Perfect Reconstruction (NPR) is proposed through converting the filter banks to the design of prototype filter. This method include two step:Firstly, the low order two-subchannel filter h(2)(n) and the real symmetric FIR filter g(n) are designed using the Parks-McClellan algorithm. Then the desired NPR prototype filter h(M)(n) is calculated through upsampling non-zero values to the coefficients of h(2)(n) with a factor of M and factor-2 downsampling according filter g(n). So the proposed algorithm can efficiently avoid the performance loss caused by image components with Interpolated Finite Impulse Response (IFIR) approach. The simulation results prove that the modulated filter banks designed by the proposed algorithm present better performance than conventional methods.% 宽带柔性转发器作为下一代卫星通信有效载荷，采用星上数字信道化处理，可以很好地解决传统有效载荷存在的问题，实现卫星信号任意频段、任意带宽之间的灵活交换。该文分析了柔性转发器中调制滤波器组的性能特性，将滤波器组的设计转换为原型滤波器的设计，提出了一种近似精确重构的原型滤波器设计方法。该方法通过间接设计的思想，首先采用Parks-McClellan算法设计得到低阶的双通道滤波器h(2)(n)和实对称FIR滤波器g(n)，然后利用g(n)实现对h(2)(n)的非零值M倍内插与2倍抽取，得到近似精确重构的原型滤波器h(M)(n)，从而避免了IFIR法设计过程中镜像分量产生的性能损失。仿真结果表明，采用该文方法设计得到的调制滤波器组较传统设计方法表现出良好的性能。
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