Patent ID: 7965781

Claim:
A filter apparatus for extracting a specific signal from a group of multi-carrier modulated signals, the filter apparatus comprising: a subcarrier selecting unit configured to select a subcarrier; a signal selecting unit configured to select and output a specific group of signals from among an input group of signals in accordance with the selected subcarrier; and a frequency offset compensating unit configured to compensate a frequency offset of a signal selected by the signal selecting unit, wherein the signal selecting unit includes: a phase offset adjusting unit configured to shift a phase of the input group of signals in accordance with the selected subcarrier, a symbol delaying unit configured to delay the input group of signals by N/2 (m+1) symbols, and an adding unit configured to add an output signal of the symbol delaying unit and an output signal of the phase offset adjusting unit to calculate one symbol string between symbol strings alternately positioned on a frequency axis in a multiplexed signal input to a signal selecting and outputting unit, wherein m is a parameter indicating a position of a stage of each of a plurality of branching circuits, N is a number of symbols existing within one modulation time, and k is a parameter indicating that a group of signals having the frequency offset of the subcarrier is input with a reference of 0 Hz.