FRM Filter Design with Group Delay Constraint Using Second-Order Cone Programming

This paper presents an improved method for the design of frequency-response masking (FRM) FIR filters with reduced passband group delays. Expressions of the group delay and its gradient for an FRM filter are derived. To directly and effectively control the group delay error, a group delay constraint is formulated and incorporated into the overall optimization. The effectiveness and flexibility of the proposed design method are demonstrated by an example, which shows that significant reduction in group delay error could be achieved at the cost of slight increase in magnitude error.