Multiplex communications – Wide area network – Packet switching
Patent
1988-09-20
1989-06-13
Griffin, Robert L.
Multiplex communications
Wide area network
Packet switching
370 50, H04J 102
Patent
active
048398896
ABSTRACT:
The invention relates to a digital filter tree composed of a plurality of digital filter banks arranged in a tree structure one behind the other to branch out in stages with a separation into L.sub..nu. individual signals taking place in each stage and the sampling rate being reduced each time by the factor M.sub..nu. where .nu.=1,2, . . . identifies the .nu.th stage. The filter tree employs a prototype filter with half-band functions for channel center frequencies f.sub.l =l.multidot.B+B/2, with a real frequency multiplex input signal being separated into L.sub..nu. complex channel signals for further processing by means of a discrete Fourier transformation. For all stages M.sub..nu. =2 and L.sub..nu. =4 are fixed, with only two signals of the L.sub..nu. =4 being utilized. The arrangement permits adaptation of a hierarchical multi-stage method also to numbers of channels which are not equal to a power of two without changing the input sampling frequency and without the causing channels, whose number is fixed by the difference from the next higher power of two, to idle.
REFERENCES:
patent: 4393456 (1983-07-01), Marshall, Jr.
patent: 4412325 (1983-10-01), Molo
J. H. McClellan et al., "A Computer Program for Designing Optimum FIR Linear Phase Digital Filters," IEEE Transactions on Audio and Electroacoustics, vol. AU-21, No. 6, Dec. 1973, pp. 506-526.
ANT Nachrichtentechnik GmbH
Chin Wellington
Griffin Robert L.
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