Patent ID: 6512798
Filing Date: 2003-01-28
Classification: H04L

Abstract:
A digital signal communication system comprising:a transmission circuit for transmitting two types of signals digitally by orthogonal modulation, wherein said transmission circuit includes an orthogonal modulator and a non-recursive digital low-pass filter having the same frequency characteristic as a predetermined frequency characteristic of the output signal of said orthogonal modulator, wherein assuming that the total number of taps required for determining the frequency characteristic of said nonrecursive digital low-pass filter is H and the series of tap coefficients is set as C1, C2, C3, . . . , CH, where H is an arbitrary odd number of not less than 3, said nonrecursive digital low-pass filter includes a first low-pass filter for filtering one of said two types of signals, and a second low-pass filter for filtering the other of said two types of signals, wherein said first low-pass filter has taps approximately one half of H including the tap coefficient series of C1, C3, C5, . . . , CODD, and said second low-pass filter has taps approximately one half of H including the tap coefficient series of C2, C4, C6, . . . , CEVEN, wherein the number of taps of said first low-pass filter is different by one from that of said second low-pass filter, and wherein the tap coefficients of said first and second low-pass filters are set in such relations that C1=CH, C2=CHâˆ’1, C3=CHâˆ’2, . . . Cn=CHâˆ’(nâˆ’1), where n is an arbitrary integer not less than 1.