Memory-Based Digital Filter for Variable Shift Register Emulation

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Solution Overview

Problem

Existing digital filters in communication systems are expensive due to the large number of electronic components required for implementing shift registers, which are necessary for performing filtering operations like FIR and IIR filtering.

Innovation Solution

A digital filter that uses memory to emulate a variable shift register, where data samples are stored in memory, read, multiplied with coefficients, logically shifted, and written back, mimicking the behavior of a shift register without the need for physical flip-flops, thereby reducing hardware requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a traditional N-stage shift register is used in an N-tap FIR filter, then the filter can perform filtering operations, but the number of electronic components increases significantly

Engineering Contradiction:

Improvefilter configuration flexibilityVSAvoidnumber of electronic components

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines the shift register functionality with memory structures by using the same memory to store both filter coefficients and data samples. The memory serves dual purposes: storing coefficient values and performing the shift register function through address manipulation, thereby reducing the total number of electronic components while maintaining filter adaptability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The memory structure is designed to perform multiple functions: it stores filter coefficients, stores data samples, and emulates shift register behavior through address generation and data retrieval operations. This multi-functionality eliminates the need for separate shift register components, reducing device complexity while preserving filtering capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If a 128-tap FIR filter with 16-bit data is implemented using traditional shift registers, then filtering performance is achieved, but the hardware cost increases

Engineering Contradiction:

Improvefiltering performanceVSAvoidhardware cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent creates a virtual shift register by copying data samples between memory locations using address manipulation rather than physical shift register stages. This virtual emulation achieves the same filtering performance with fewer physical components, reducing hardware manufacturing costs while maintaining reliability.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The invention changes the operational parameters of the memory by using different address generation schemes and data retrieval patterns to emulate shift register behavior. By changing how memory is accessed and manipulated, the system achieves traditional shift register functionality with reduced hardware complexity and lower manufacturing costs.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7548941B2Digital filter using memory to emulate variable shift register

Publication Date: 2009.06.16 ANALOG DEVICES INC

AI summary

A digital filter uses memory to emulate a variable shift register. Data samples are stored in a memory. The data samples are read from the memory, multiplied with corresponding coefficients stored in the same or a different memory, logically shifted, and written back into the memory so as to emulate a variable shift register. The data samples can be logically shifted by one or more bits at a time.