Patent ID: 6493358
Filing Date: 2002-12-10
Classification: H04J,H04L

Abstract:
A polyphase digital filter network based on a linear phase prototype filter for use in a group demultiplexer for generating N output data signals associated with N channels from a corresponding Frequency Division Multiplexed input signal Y(n), said linear phase prototype filter comprising N sub-filters being characterized by L coefficients forming NL coefficients for said prototype filter, said polyphase digital filter network comprising:Lâˆ’1 Zâˆ’N shift registers in series receiving said multiplexed input signal Y(n) to produce Lâˆ’1 corresponding shifted signals Y(nâˆ’rN), with r=1, . . . , Lâˆ’1; a set of p first adder sections each receiving a distinct pair of signals from said multiplexed input signal Y(n) and said shifted signals Y(nâˆ’rN); a set of q multiplier sections including p first multiplier sections each being coupled to a respective output of a corresponding one of said first adder sections for combining each said output with a corresponding set of N transformed filter coefficients gi derived from said coefficients of said linear phase prototype filter; said set of q multiplier sections including a further multiplier section receiving shifted signal Y&it;(n-(L-12)&it;N)â€ƒwhere L is odd for combining thereof in parallel with a corresponding set of s further transformed filter coefficients gi derived from the coefficients of said linear phase prototype filter; a set of N second adder sections each being coupled to distinct outputs of said multiplier sections for producing a corresponding set of N transformed signals Ck(n), with k=0, . . . , Nâˆ’1; and a set of t third adders each receiving a distinct pair of signals {CT(n),CTâ€²(n)} from said transformed signals Ck(n) for producing a first filtered signal A0(n) and a set of Nâˆ’1 filtered signals Ak(n+k), with k=1, . . . , Nâˆ’1.