# US 5,710,763 A · Filtered fast Fourier transmultiplexer and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,710,763 A - Document ID: US5710763A - Status: Granted - Kind: A - Application number: 08/509,123 - Filed: 1995-07-31 - Granted: 1998-01-20 - Earliest claimed: 1995-07-31 - Assignees: Motorola, Inc. - Inventors: Robert Mark Harrison - Web page: https://patentgrep.com/patent/US5710763A ## CPC - H04J 4/005: {Transmultiplexing} - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) ## Abstract A filter fast Fourier transmultiplexer divides a multi-channel communication signal into single channel communication signals through a cascade of filters and mixers. The output sample rate is maintained at the input sample rate and memory requirements and computations are substantially reduced. ## Claims ### Claim 1 A method of transmultiplexing a multi-channel information signal at a first sample rate into a plurality of selected communication channels at the first sample rate, the method comprising the steps of: (a) commutating the information signal to a first plurality of filters and commutating a delayed sample of the information signal to a second plurality of filters, each filter of the first plurality of filters corresponding with a filter of the second plurality of filters; (b) summing an output of each filter of the first plurality of filters with an output from the corresponding filter of the second plurality of filters to form a first plurality of summed outputs; (c) summing a scaled output of each of the second plurality of filters with an output of the corresponding filter of the first plurality of filters to form a second plurality of summed outputs; (d) scaling each output of the second plurality of summed outputs by a time varying value; (e) commutating the first plurality of summed outputs to form a first output signal at the first sample rate; and (f) commutating the scaled second plurality of summed outputs to form a second output signal at the first sample rate. ### Claim 2 (depends on 1) The method of claim 1 wherein the step of scaling each of the second plurality of summed outputs by a time varying value comprises scaling each of the second plurality of summed outputs by a complex exponential. ### Claim 3 (depends on 1) The method of claim 1 wherein the step of commutating the information signal to a first plurality of filters comprises commutating the information signal to a first plurality of substantially identical filters. ### Claim 4 (depends on 1) The method of claim 1 wherein the step of commutating a delayed sample of the information signal to a second plurality of filters comprises commutating a delayed sample of the information signal to a second plurality of substantially identical filters. ### Claim 5 (depends on 1) The method of claim 1 wherein the step of summing a scaled output of each of the second plurality of filters with an output of the corresponding filter of the first plurality of filters to form a second plurality of summed outputs comprises subtracting an output of each of the second plurality of filters from an output of the corresponding filter of the first plurality of filters. ### Claim 6 (depends on 1) The method of claim 1 further comprising the step of communicating the plurality of selected communication channels to a multi-channel communication system. ### Claim 7 An apparatus for transmultiplexing a multi-channel information signal at a first sample rate into a plurality of selected communication channels at the first sample rate comprising: (a) means for commutating the information signal to a first plurality of filters and commutating a delayed sample of the information signal to a second plurality of filters, each filter of the first plurality of filters corresponding with a filter of the second plurality of filters; (b) means for summing an output of each filter of the first plurality of filters with and output from the corresponding filter of the second plurality of filters to form a first plurality of summed outputs; (c) means for summing a scaled output of each of the second plurality of filters with an output of the corresponding filter of the first plurality of filters to form a second plurality of summed outputs; (d) means for scaling each output of the second plurality of summed outputs by a time varying value; (e) means for commutating the first plurality of summed outputs to form a first output signal at the first sample rate; and (f) means for commutating the scaled second plurality of summed outputs to form a second output signal at the first sample rate. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the means for commutating the information signal further comprises means for commutating the first output signal. ### Claim 9 (depends on 8) The apparatus of claim 8 wherein in the means for commutating the first output signal to a first plurality of filters is operable for commutating the first output signal to a third plurality of filters and the means for commutating a delayed sample of the first output signal to a second plurality of filters is operable for commutating a delayed sample of the first output signal to a fourth plurality of filters. ### Claim 10 (depends on 7) The apparatus of claim 7, wherein the means for commutating the information signal further comprises means for commutating the second output signal. ### Claim 11 (depends on 10) The apparatus of claim 10 wherein in the means for commutating the second output signal to a first plurality of filters is operable for commutating the second output signal to a third plurality of filters and the means for commutating a delayed sample of the second output signal to a second plurality of filters is operable for commutating a delayed sample of the second output signal to a fourth plurality of filters. ### Claim 12 (depends on 7) The apparatus of claim 7 wherein the time varying value comprises a complex exponential. ### Claim 13 (depends on 7) The apparatus of claim 7 wherein the first plurality of filters comprises a plurality of substantially identical filters. ### Claim 14 (depends on 7) The apparatus of claim 7 wherein the second plurality of filters comprises a plurality of substantially identical filters. ### Claim 15 (depends on 7) The apparatus of claim 7 wherein the means for summing a scaled output of each of the second plurality of filters with an output of the corresponding filter of the first plurality of filters to form a second plurality of summed outputs is operable for subtracting an output of each of the second plurality of filters from an output of the corresponding filter of the first plurality of filters. ### Claim 16 A filtered fast Fourier transmultiplexer comprising: a commutator having an input and a first output and a second output, wherein the first output selectively couples a sample of a multi-channel information signal to inputs of a first plurality of filters, and the second output selectively couples a delayed sample of the multi-channel information signal to inputs of a second plurality of filters; the first and second plurality of filters each having an output; a first plurality of combiners each coupled to an output of one the first plurality of filters and to an output of a corresponding filter of the second plurality of filters, each of the first plurality of combiners having an output; a second plurality of combiners each coupled to an output of one of the second plurality of filters and to an output of the corresponding filter of the first plurality of filters, each of the second plurality of combiners having an output; a plurality of scalers each having an input coupled to an output of one of the second plurality of combiners and an output; a second commutator for commutating the outputs of the first plurality of filters to a first output signal at the sample rate; and a third commutator for commutating the outputs the plurality of scalers to a second output signal at the sample rate.