Patent ID: 7466780

Claim:
A filter unit for filtering a prescribed real impulse constant r satisfying 2−√3−0.1≦r≦2−√3+0.1, the filter unit comprising: an input terminal that accepts input of a Chebyshev chaos-type spreading code sequence X n , wherein 1≦n≦N, and N is an integer equal to 1 or more, the spreading code sequence being an input signal of chip length D; a delay section that includes (N−1) series-connected delay circuits for delaying by the chip length D of the spreading code sequence X n whose input was accepted, and outputs a plurality of signals produced by delaying the spreading code sequence by a delay time T=0, D, 2D, 3D, . . . , (N−1)D; an amplifying section that includes N series-connected amplifiers for amplifying the delayed signals output from the delay circuits by amplification factors (−r) N−T/D when the delay time is T, and outputs the amplified signals; an adder section that sums the amplified signals output from the N amplifiers and outputs the resulting sum signal; and an output terminal that outputs the sum signal as a signal of an optimal chaotic spreading sequence.