Just as the half-band decimator is an optimized version of the more general polyphase decimation filter, the half-band interpolator is a special case of a polyphase interpolator. This Figure shows the half-band interpolator.
The coefficient set for a true half-band interpolator is identical to that of a half-band decimator with the same specifications. The large number of zero entries in the impulse response is exploited in exactly the same manner as with the half-band decimator to produce hardware-optimized half-band interpolators. The process is presented in This Figure . This Figure (a) is the impulse response, This Figure (b) shows the polyphase partition, and This Figure (c) is the optimized architecture that has taken full advantage of the 0 entries in the coefficient data, along with coefficient symmetry.
The high density of zero-valued filter coefficients is exploited in the FPGA realization to produce a minimal area implementation.
