An Efficient and Modular Transmultiplexer Design

A new transmultiplexer design is presented in which reliability is achieved by adopting a tree structure. A working principle based upon analytic signals results in a modular structure. The usage of FIR filters designed to have coefficients which are sums of a limited and prescribed number of powers of two together with an efficient, low-sensitivity interpolating structure results in a very efficient design. When these interpolators are used to implement all processing functions required, a highly modular design is obtained which is based solely upon the elementary all-pass cell. Simulation results for a four-channel transmultiplexer are presented together with a performance evaluation for the translation between two 30 channel TDM primary groups and one 60 channel FDM supergroup and for the translation between one 24 channel North American TDM unit and two 12 channel FDM groups. The design is found to have the reliability and modularity attributes which can be obtained from a tree structure, and at the same time its efficiency compares favorably with that of transform-based transmultiplexers.