Patent ID: 7984092

Claim:
A method of demodulating a sound signal using an FIR filter process which is capable of being controllably and switchably operated in a single mode for filtering a single signal when the sound signal is a single signal and in at least one multiplex mode for filtering a multiplexed signal when the sound signal is a multiplexed signal, the method comprising: generating, in a pre-summation stage, partial sums from intermediate filter signals obtained by an input signal by summing, from said intermediate filter signals, subsets which are assigned to a given component of the multiplexed input signal, wherein in said at least one multiplexed mode partial summations are carried out and controlled in conformity with a multiplex structure underlying said multiplexed signal in order to obtain the partial sums as accordingly filtered single signals; generating, from said partial sums, an entire sum by adding an entirety of said partial sums in a controllable manner if and only if a single signal is given as said input signal in the single mode such that a single-signal sound signal is filtered using a large filter; and generating, from said partial sums, said filtered single signals represented by the partial sums in a controllable manner if and only if a multiplexed signal is given as said input signal in the at least one multiplex mode such that each component of a multiplexed sound signal is filtered using short filters.