In this paper, we proposed three types of binomial filter for spectrum sensing in cognitive radio system. Three filters are binomial, negative binomial and composite binomial filters and the frequency responses of their transfer functions are analyzed and the numbers of stages to meet the required attenuation are driven. As a result of performance analysis in terms of the number of stages, negative and composite binomial filters are superior to the binomial filter. Since the proposed three

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... rs have a unified cascaded structure and are easy to be implemented without any multiplier, it is expected that they will have wide applications.