为满足滤波正交频分复用系统中子带滤波器的要求，基于升余弦函数，设计满足目标频率响应的通带边缘滚降到截止幅度且可自由调节滚降带宽的线性相位滤波器，并采用窗函数法软截断其时域冲激响应，得到缩短型-修正软截断升余弦子带滤波器。所设计的子带滤波器的性能可仅通过滚降带宽和滚降系数进行调节，实现较为简单。仿真结果表明，所设计的子带滤波器相比于软截断SinC型子带滤波器有较小的通带波纹系数、较大的阻带衰减和较高的时域集中度，相比于软截断升余弦子带滤波器RC-Filter有较窄的过渡带。
In order to satisfy requirements for the subband filter in Filtered-OFDM (filtered-orthogonal frequency division multiplexing) systems, the TMRC-Filter (truncate modified raised-cosine filter) is proposed based on the window function method. Compared with the traditional SinC-Filter (windowed sinc function filter) and RC-Filter (raised-cosine filter) whose linear phase filter ends with 0, the linear phase filter of the proposed TMRC-Filter ends with a non-zero roll-cut-off-amplitude factor, and the rolled-off bandwidth of the proposed TMRC-Filter can be flexibly adjusted. Moreover, the performance of the rpoposed TMRC-Filter is totally determined by the rolled-off bandwidth which is independent of the system parameter and roll-off factor, and it is simple to implement. The simulation results show that the TMRC-Filter achieves the lower ripple, larger stop-band attenuation, and better time localization than the SinC-Filter and the narrower transition band than the RC-Filter.
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