Sampling rate increase and decrease in wave digital filters

In addition to the regular input terminal at the input port and the regular output terminal at the output port, wave digital filters have available a second input terminal at the output port and a second output terminal at the input port. These additional terminals can be made use of for realizing efficient wave digital filters for sampling rate increase and decrease. An exact computation of the conversion (transfer) functions shows that their analytic expressions are strongly reminiscent of the conversion functions for analog conversion circuits. Among the advantages thus obtainable are improved loss performance for a given filter structure, increased dynamic range, and low passband sensitivity for the coefficients.