Method and Apparatus For Hybrid Digital Filtering

Abstract

New hybrid filters are presented based on time and transform domain structures. The hybrid filters have a combined benefit from the advantages obtained by the time and transform domain structures. The overall efficiencies are drawn from combining the pre- and post-processing of the time domain and block based transform domain structures. Further improvements are obtained by interchanging block construction and transforms with linear operations in the pre- and post-processors. The hybrid structures apply to single input, single output, multiple input, and multiple output structures. For the multi input and multi output structures further improvements are obtained by having common processing blocks for the input(s) and common processing blocks for the output(s). They hybrid filters are also efficient in topologies where filter outputs are combined via linear operation(s) generating combined results. The efficiencies of the new hybrid filter may lead to significant fardware, power, silicon area, or somputational savings.

What is claimed is: 
     
         1 . A digital filter comprising:
 a first time domain element acting on a main input stream, generating a plurality of first streams, wherein at least one of said plurality of first streams has a sample rate which is less than that of the main input stream;   a pre-processor for processing said plurality of first streams to produce a plurality of second streams, said pre-processor performing at least one linear operation;   a plurality of processors performing processing on said plurality of second streams to produce a plurality of third streams, wherein at least one of said plurality of processors is a transform domain processor;   a post-processor for processing said plurality of third streams to produce a plurality of fourth streams, said post-processor performing at least one linear operation and said processing of post-processor corresponds to said processing of pre-processor;   a single element delay in at least one of said pre-processor or said post-processor; and   a second time domain element producing a main output stream by acting on said plurality of fourth streams.   
     
     
         2 . The digital filter of  claim 1 , wherein said pre-processor comprises:
 an input block constructor; and   an input transform.   
     
     
         3 . The digital filter of  claim 2 , wherein said input block constructor and said input transform act on at least one of said plurality of first streams prior to said at least one linear operation. 
     
     
         4 . The digital filter of  claim 1 , wherein said post-processor comprises:
 an output transform; and   an output stream constructor.   
     
     
         5 . The digital filter of  claim 4 , wherein said output transform and said output constructor act on said plurality of third streams after said at least one linear operation. 
     
     
         6 . The digital filter of  claim 1 , wherein said transform domain processor is a partitioned transform domain processor. 
     
     
         7 . The digital filter of  claim 6 , wherein said pre-processor comprises:
 an input constructor; and   an input transform.   
     
     
         8 . The digital filter of  claim 7 , wherein said input constructor and said input transform act on said plurality of first streams prior to said at least one linear operation. 
     
     
         9 . The digital filter of  claim 6 , wherein said post-processor comprises:
 an output transform; and   an output constructor.   
     
     
         10 . The digital filter of  claim 9 , wherein said output transform and said output constructor act on said plurality of third streams after said at least one linear operation. 
     
     
         11 . The digital filter of  claim 1 , wherein the said main input stream corresponds to a signal to be decimated or interpolated. 
     
     
         12 . A digital filter comprising:
 a first time domain element acting on a main input stream, generating a plurality of first streams, wherein at least one of said plurality of first streams has a sample rate which is less than that of the main input stream;   a pre-processor for processing said plurality of first streams to produce a plurality of second streams, said pre-processor performing at least one linear operation;   a plurality of hybrid filter sections, wherein said hybrid filter section is comprised of a) a hybrid filter section processor performing processing on said plurality of second streams to produce a plurality of third streams, b) a hybrid filter section post-processor for processing based on said plurality of third streams to produce a plurality of fourth streams, said post-processor performing at least one linear operation and said processing of post-processor corresponds to said processing of pre-processor, and wherein at least one of said filter section processor of said plurality of hybrid filter sections is a transform domain processor, and c) a single element delay in at least one of said pre-processor or said hybrid filter section post-processor; and   a second time domain element producing a plurality of main output streams by acting on said plurality of fourth streams from each of said hybrid filter section.   
     
     
         13 . The digital filter of  claim 12 , wherein said pre-processor comprises:
 an input constructor; and   an input transform.   
     
     
         14 . The digital filter of  claim 13 , wherein said input constructor and said input transform act on said plurality of first streams prior to said at least one linear operation. 
     
     
         15 . The digital filter of  claim 14 , wherein said transform domain processor is a partitioned transform domain processor. 
     
     
         16 . The digital filter of  claim 12 , wherein at least one of said plurality of hybrid filter section's post-processor comprises:
 an output transform; and   an output constructor.   
     
     
         17 . The digital filter of  claim 16 , wherein said output transform and said output constructor act on said plurality of third streams after said at least one linear operation. 
     
     
         18 . The digital filter of  claim 17 , wherein said transform domain processor is a partitioned transform domain processor. 
     
     
         19 . The digital filter of  claim 12 , wherein said main input stream corresponds to a signal to be decimated or interpolated. 
     
     
         20 . The digital filter of  claim 19 , wherein at least one of said plurality of hybrid filter sections corresponds to polyphase component of a filter. 
     
     
         21 . A method for performing digital filtering, comprising the steps of:
 acting on a main input stream by a time domain element to generate a plurality of first streams, wherein at least one of said plurality of first streams has a sample rate which is less than that of the main input stream;   processing by a pre-processor on said plurality of first streams to produce a plurality of second streams, said pre-processor performing at least one linear operation;   processing by a plurality of processors on said plurality of second streams to produce a plurality of third streams, wherein at least one of said plurality of processors is a transform domain processor;   processing by a post-processor on said plurality of third streams to produce a plurality of fourth streams, said post-processor performing at least one linear operation and said processing of post-processor corresponds to said processing of pre-processor; and   producing a main output stream by acting on said plurality of fourth streams by a second time domain element, wherein a single element delay is present in at least one of said pre-processor or said post-processor.   
     
     
         22 . A multiple input and multiple output digital filter comprising:
 a first time domain element acting on at least one of a plurality of main input streams, generating a plurality of first streams, wherein at least one of said plurality of first streams has a sample rate that is less than said at least one main input stream;   a pre-processor for processing said plurality of first streams to produce a plurality of second streams, said pre-processor performing at least one linear operation;   a plurality of processors performing processing on said plurality of second streams to produce a plurality of third streams, wherein at least one of said plurality of processors is a transform domain processor;   a combiner for processing based on said plurality of third streams to produce a plurality of fourth streams;   a post-processor for processing based on said plurality of fourth streams to produce a plurality of fifth streams, said post-processor performing at least one linear operation and said processing of post-processor corresponds to said processing of said pre-processor;   a single element delay in said pre-processor or said post-processor; and   a second time domain element producing at least one of a plurality of main output streams by acting on said plurality of fifth streams.   
     
     
         23 . The multiple input and multiple output digital filter of  claim 22 , wherein said pre-processor comprises an input block constructor and an input transform; said post-processor comprises of an output transform and output constructor; at least one of said transform domain processors is a partitioned transform domain processor; and said combiner comprises of at least one linear operation. 
     
     
         24 . The multiple input and multiple output digital filter of  claim 23 , wherein said input constructor and said input transform act on said plurality of first streams prior to said at least one linear operation. 
     
     
         25 . The multiple input and multiple output digital filter of  claim 23 , wherein said output transform and said output constructor act on said plurality of fourth streams after said at least one linear operation. 
     
     
         26 . The multiple input and multiple output digital filter of  claim 22 , wherein at least one of said main input streams corresponds to a signal to be decimated or interpolated. 
     
     
         27 . The digital filter of  claim 26 , wherein at least one of plurality of processors performing processing on said plurality of second streams to produce a plurality of third streams corresponds to polyphase component of a filter.