Bi-directional rate converting apparatus for converting a clock rate of

Abstract

Bi-directional rate converting apparatus up-converts a digital signal having a clock rate f.sub.B to a digital signal having a clock rate f.sub.A and also down-converts a digital signal having a clock rate f.sub.A to a digital signal having the clock rate f.sub.B. The digital signal having the clock rate f.sub.B is interpolated to produce a signal having the clock rate f.sub.A which is supplied to a filter during up-conversion. The digital signal having the clock rate f.sub.A is supplied to the filter during down-conversion, which after being filtered is thinned to produce a digital signal having the clock rate f.sub.B. The digital signal supplied to the filter is filtered in accordance with a frequency characteristic which has '0' points at frequencies of (f.sub.C /M)*x, where x equals an integer value from 1 to (M-1), and which also has '0' points at frequencies of (f.sub.C /L)*y, where y equals an integer value from 1 to (L-1). The value f.sub.C being the least common multiple of f.sub.A and f.sub.B such that f.sub.C =M*f.sub.A =L*f.sub.B, where M and L have respective integer values.