A 108-tap 1:4 interpolation FIR filter device for digital mobile telecommunication
having a single bit input that employs a look-up table minimum scheme and a pipeline
structure in which the size of the entire look-up tables is significantly reduced
by dividing four coefficient groups into three parts, respectively, and effectively
using the symmetry of the 108-tap filter coefficient and the symmetry within the
look-up table. The FIR filter includes an input shift register and selector for
processing a single bit input of four channels, an address generator for producing
addresses of the look-up table, look-up table group 03 for producing filter
outputs group by group via the look-up table and the calculator using the address
as an input, a pipeline register I for delaying the filter outputs for coefficient
group which are outputted in parallel, a group selector for converting the delayed
outputs in serial channel by channel, and a pipeline register II for matching the
time of filter output channel by channel.
