Rational sampling rate conversion structures with minimum delay requirements

Recent developments on multirate system design show that a rational (L/M) sampling rate conversion system can be reconfigured into a three-dimensional polyphase structure. However, the delay requirements associated with each subfilter path in such a structure have not sufficiently been considered. The paper presents a detailed analysis of the delay requirements, and shows that a reduction by a factor of L on the number of data stores can be achieved. A design approach is introduced for efficient structures based on the minimisation of the total number of delay units. Two transformation rules are derived which directly lead to a homogeneous system configuration. This approach is general and simple so that any rational sampling rate conversion system can be specified by a set of parameters calculated by a small computer program. A hardware implementation is also presented, which demonstrates the usefulness of the present approach.