SAR ADC With Embedded IIR Feedback for Blocking Signal Rejection

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Solution Overview

Problem

Wireless local area network (WLAN) wake-up radios face challenges in reducing power consumption and circuit size due to the presence of blocking signals, which existing technologies address inadequately using large and costly resistor-capacitor or active filters.

Innovation Solution

Implementing a successive approximation register (SAR) analog-to-digital converter (ADC) with an embedded infinite impulse response (IIR) filter that attenuates blocking signals using digital sample feedback to a capacitive digital-to-analog converter (CDAC), eliminating the need for additional filters and reducing die area and cost.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If resistor-capacitor or active filters are used to attenuate blocking signals, then signal filtering performance is improved, but circuit size and cost increase

Engineering Contradiction:

Improveblocking signalsVSAvoidcircuit size

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The patent combines the filtering function with the existing SAR ADC structure by implementing the IIR filter using the CDAC and SAR control circuit that are already present in the converter. The feedback path from the SAR control circuit to the CDAC is utilized to create the infinite impulse response filter, eliminating the need for separate filter components and reducing overall circuit size.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The SAR control circuit and CDAC are designed to perform multiple functions: they serve both as the core components of the SAR ADC for analog-to-digital conversion and as the elements that implement the IIR filter for blocking signal attenuation. This multi-functionality eliminates the need for dedicated filter hardware, reducing circuit complexity and area.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Object-affected harmful factors

If resistor-capacitor or active filters are used to attenuate blocking signals, then signal filtering performance is improved, but device cost increases

Engineering Contradiction:

Improveblocking signalsVSAvoiddevice cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The filtering function is merged into the existing SAR ADC architecture, eliminating the need for separate filter components. The IIR filter is implemented using the same CDAC and control circuitry that perform the ADC function, reducing component count and manufacturing cost.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses digital sample feedback to create the IIR filter effect, essentially copying and processing the digital representation of the signal through the feedback path. This digital-based approach avoids the need for additional analog filter components, reducing manufacturing complexity and cost.

Inventive Principle:

Principle #26Copying

3Object-affected harmful factors

If additional filters are added to attenuate blocking signals, then signal filtering performance is improved, but device complexity increases

Engineering Contradiction:

Improveblocking signalsVSAvoiddevice complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The IIR filter is merged with the SAR ADC structure, using the existing feedback path from the SAR control circuit to the CDAC. This integration eliminates the need for separate filter stages and reduces overall device complexity while maintaining effective blocking signal attenuation.

Inventive Principle:

Principle #5Merging (Combining)

4Object-affected harmful factors

If larger filters are used to attenuate blocking signals, then filtering effectiveness is improved, but power consumption increases

Engineering Contradiction:

Improveblocking signalsVSAvoidpower consumption

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The patent implements the IIR filter using digital sample feedback processed through the existing CDAC and SAR control circuit. This digital-based filtering approach consumes less power than traditional analog filters, as it leverages the low-power SAR ADC architecture already in place rather than requiring additional power-hungry filter components.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS11424756B2Successive approximation register analog-to-digital converter with embedded filtering

Publication Date: 2022.08.23 TEXAS INSTRUMENTS INC

AI summary

A successive approximation register (SAR) analog-to-digital converter includes a capacitive digital-to-analog converter (CDAC), a comparator, and a SAR control circuit. The comparator is coupled to an output of the CDAC. The SAR control circuit is coupled to an input of the CDAC and to an output of the comparator. The SAR control circuit is configured to provide a feedback signal to the CDAC. The CDAC is configured to apply the feedback signal to form an infinite impulse response filter.