Audio Processor FIR Filter Circuits for Single-Cycle Execution

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Solution Overview

Problem

Existing digital signal processing systems face inefficiencies in implementing finite impulse response (FIR) filters, particularly in requiring multiple instruction cycles and resource allocation, which can slow down processing and limit the performance of audio filtering operations.

Innovation Solution

The implementation of dedicated FIR filter circuits within a processor, each associated with a specific FIR filter instruction, allowing for the execution of FIR filter operations within a single execution cycle, with input data being processed as pulse density modulation (PDM) and output provided at a reduced sample rate through a decimation ratio, optimizing processing efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If dedicated FIR filter circuits are implemented within the processor, then processing speed and execution efficiency are improved, but device complexity and resource allocation become more challenging

Engineering Contradiction:

Improveprocessing speedVSAvoiddevice complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The processor is segmented into multiple execution units, each with dedicated FIR filter circuits for specific FIR filter instructions. This segmentation allows parallel processing of different filter operations simultaneously, improving overall productivity while managing complexity through modular design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

FIR filter functionality is extracted from general-purpose execution units and implemented as dedicated hardware circuits within specific execution units. This extraction enables single-cycle execution of FIR filter instructions, significantly improving processing speed for audio signal filtering operations.

Inventive Principle:

Principle #2Taking out (Extraction)

2Loss of time

If multiple instruction cycles are required for FIR filter execution, then resource allocation is simplified, but processing time increases

Engineering Contradiction:

Improveprocessing timeVSAvoidresource allocation

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

FIR filter circuits are pre-configured and dedicated within execution units before instruction execution. This preliminary preparation allows the circuits to be ready to process audio data immediately when FIR filter instructions are invoked, eliminating the need for multiple instruction cycles and reducing processing time.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Multiple identical FIR filter circuits are copied into different execution units, each capable of executing FIR filter instructions independently. This copying approach enables parallel processing and single-cycle execution, dramatically reducing the time loss associated with sequential processing in shared resources.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS10243581B1System and method for implementing finite impulse response filter in an audio processor

Publication Date: 2019.03.26 APPLE INC

AI summary

A method and apparatus for implementing FIR filters in a processor includes a plurality of execution units executing instructions of an instruction set. The execution units include a number of FIR filter circuits, each of which is associated with a corresponding one of a number FIR filter instructions. Furthermore, each of the FIR filter circuits is and dedicated exclusively to executing its corresponding one of the FIR filter instructions. Each FIR filter execution unit receives input data and provides filtered output data.