Abstract: As a new intelligent spectrum sharing technology, Cognitive Radio (CR) technology could effectively improve the spectrum utilization. It allows the cognitive user to use the idle spectrum of licensed user under the premise of free interference. Because of the high sidelobe attenuation, the traditional physical layer transmission technology in cognitive radio system, that is Orthogonal Frequency Division Multiplexing (OFDM) multi-carrier modulation technology, suffers from the the interference between the adjacent subbands and the interference among licensed users and cognitive users, an alternative multi-carrier modulation technology, filter bank based multi-carrer technology, was introduced in this paper to eliminate the interferences. An indirect design method for designing the prototype filter in filter bank was proposed while formulating the filter bank as an unconstrained linear optimization problem of prototype filter.Firstly,two low-order and linear lowpass filters were designed by using the Parks-McClellan algorithm, and then the prototype filter was optimally designed through the interpolation and cascade operation. Compared to the conventional direct method, the simulation results show that the modulated filter banks designed by the proposed method in this paper present better performance in the length of filter coefficients and the alias errors.

Key words: Cognitive Radio (CR), filter bank based multicarrier modulation, modulated filter bank, prototype filter, Interpolated FIR filter (IFIR)

摘要： 作为一种新的智能频谱共享技术，认知无线电(CR)技术允许认知用户在不干扰授权用户的前提下使用其空闲的频谱而有效提高频谱利用率。为克服传统认知无线电系统物理层传输技术即正交频分复用(OFDM) 多载波调制技术因高的旁瓣衰减带来的相邻带间干扰和认知用户对授权用户的干扰，研究了一种可以替代的多载波调制技术,即滤波器组多载波调制技术。将滤波器组的设计归结为一个无约束的线性优化设计原型滤波器问题，并提出一种间接设计的方法。该方法首先采用Parks-McClellan算法设计两个低阶的线性低通滤波器，然后通过插值和级联操作优化设计需要的原型滤波器。仿真结果表明，相对传统的直接设计方法，所提方法能够明显降低滤波器系数长度和改善滤波器组的混叠误差。

关键词: 认知无线电, 滤波器组多载波调制, 调制滤波器组, 原型滤波器, 插值的FIR滤波器