Patent ID: 7660361

Claim:
A filter apparatus for extracting a specific signal from a group of multi-carrier modulated signals, the filter apparatus comprising: a signal component demultiplexing apparatus including a plurality of branching circuits connected in stages and hierarchically by a branching method, each branching circuit having symbol delaying means for delaying an input group of signals by N/2 (m+1) symbols, phase offset adjusting means for shifting a phase of the input group of signals by −π(k/2 m ) radians with a reference of 0 Hz, adding means for adding an output signal of the symbol delaying means and an output signal of the phase offset adjusting means to calculate one symbol string alternately positioned on a frequency axis in a multiplexed signal input to a signal selecting and outputting means, and subtracting means for subtracting the output signal of the phase offset adjusting means from the output signal of the symbol delaying means to calculate another symbol string alternately positioned on the frequency axis in the multiplexed signal input to the signal selecting and outputting means, wherein m is a parameter indicating a position of a stage of each branching circuit, N is a number of symbols existing within one modulation time, and k is a parameter indicating that a group of signals having a frequency offset of a subcarrier is input with the reference of 0 Hz; signal selecting means for selecting and outputting a group of symbols of a specific subcarrier from among the symbol strings demultiplexed at the signal component demultiplexing apparatus; and frequency offset compensating means for compensating for the frequency offset of the group of symbols selected and output by the signal selecting means.