Chopper-Stabilized Sampled-Data Receiver With AC Coupling

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Solution Overview

Problem

Wireless communication devices face challenges with flicker noise and voltage offset in RFFE circuitry, particularly in direct-conversion scenarios, which can be exacerbated by chopper stabilization, leading to additional noise interference.

Innovation Solution

The implementation of alternating current (AC) coupling circuits between chopper circuits in the transmitter or receiver chain to reduce or eliminate flicker noise and voltage offset, while enabling selection of distinct common-mode levels at each stage and minimizing signal loss at direct current frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If chopper stabilization is employed to overcome flicker noise and voltage offset, then flicker noise and voltage offset are reduced, but additional noise is introduced due to chopper sampling operations

Engineering Contradiction:

Improveflicker noise and voltage offsetVSAvoidadditional noise from chopper sampling

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

An AC-coupling circuit is introduced as an intermediary component between the first and second chopper circuits. This circuit includes capacitors coupled to the differential input terminals of the amplifier and a resistor coupled in series between these input terminals. The AC-coupling circuit mediates the signal path to reduce the harmful effects of chopper sampling noise while preserving the benefits of chopper stabilization.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If discrete-time circuits are used to process sampled data, then power consumption is reduced and linearity is increased, but flicker noise and voltage offset from buffers or amplifiers limit performance in narrowband applications

Engineering Contradiction:

Improvepower consumptionVSAvoidflicker noise and voltage offset

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The AC-coupling circuit serves as a mediator that allows discrete-time processing to continue while mitigating the harmful effects of flicker noise and voltage offset from the amplifier, enabling narrowband applications to achieve both low power consumption and acceptable noise performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The circuit modifies the signal parameters by coupling AC signals through capacitors while blocking DC components. This parameter change allows the system to operate in discrete-time mode with reduced power consumption while the AC-coupling prevents DC offset and reduces flicker noise from affecting the narrowband signal processing.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250105807A1Sampled-data receiver with chopper stabilization

Publication Date: 2025.03.27 APPLE INC

AI summary

Embodiments herein provide various apparatuses and techniques to reduce flicker noise and voltage offset from the buffers and/or amplifiers while avoiding additional alias components in a sampled-data receiver with chopper stabilization. Additionally, a direct-conversion baseband chain may be improved by disposing alternating current (AC) coupling circuits between chopper circuits in the transmitter or receiver chain to enable selection of a distinct common-mode level at each stage of the direct-conversion chain, while reducing or eliminating signal loss at direct current (DC) frequencies.