Digital RF Transmitter Harmonic Cancellation Using SC-DAC

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Solution Overview

Problem

Recent wireless communication systems face challenges in minimizing intermodulation distortion due to non-linear amplification in digital RF transmitters, particularly as they support multiple bands and modes, leading to increased costs and layout complexities with the use of multiple filters.

Innovation Solution

A digital RF transmitter is designed with a switched-capacitor digital-to-analog converter (SC-DAC) that generates pattern signals with specific phase differences to remove harmonic components, thereby reducing intermodulation distortion by synthesizing these signals into the RF analog signal before amplification, using processing circuitry to create inverted-phase components that cancel out unwanted harmonic frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If filters are added to remove intermodulation distortion components, then signal quality is improved, but device complexity and cost increase

Engineering Contradiction:

Improvesignal qualityVSAvoidnumber of filters

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent converts the harmful non-linear amplification effect into a beneficial one by intentionally generating inverted-phase harmonic components that cancel out the unwanted intermodulation distortion. The power amplifier's non-linearity, which normally creates harmful distortion, is exploited to generate cancellation signals that eliminate the distortion without requiring additional filters.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent performs preliminary action by generating the inverted-phase harmonic components before the signal enters the power amplifier. The processing circuitry creates these cancellation signals in advance, so that when the amplified signal and cancellation signals combine, the intermodulation distortion is already neutralized, eliminating the need for post-amplification filtering.

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If multiple filters are used to cover multiple bands, then frequency band coverage is improved, but layout area and cost increase

Engineering Contradiction:

Improvefrequency band coverageVSAvoidlayout area

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The patent implements a universal solution that works across multiple frequency bands without requiring band-specific filters. The processed RF analog signal with removed harmonic components can be amplified by a single power amplifier for multiple bands, eliminating the need for separate filtering circuits for each frequency band and reducing overall layout area.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Use of energy by moving object

If non-linear amplification is used, then power efficiency is improved, but intermodulation distortion increases

Engineering Contradiction:

Improvepower efficiencyVSAvoidintermodulation distortion

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The processing circuitry acts as an intermediary that introduces cancellation signals with inverted phase and appropriate magnitude. These intermediary signals mediate between the power amplifier's output and the final transmitted signal, neutralizing the harmful intermodulation distortion while preserving the useful signal components.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively blocks intermodulation distortion components, improving communication performance and reducing the need for multiple filters, thus simplifying the design and reducing costs while maintaining effective signal transmission across multiple bands.

Implementation Method 1

processing circuitry configured to generate first through third pattern signals based on a pattern of an inphase (I)-quadrature (Q) binary data pair and a pattern of an inverted I-Q binary data pair, the first through third pattern signals having a same pattern and different phases

Methodology Applied

Scientific EffectPhase difference:

Implementation Method 2

a switched-capacitor digital-to-analog converter (SC-DAC) configured to remove an n-th harmonic component of an RF analog signal by amplifying the first through third pattern signals to have a certain magnitude ratio and synthesizing the amplified first through third pattern signals into the RF analog signal

Methodology Applied

Scientific EffectSignal synthesis:

Implementation Method 3

using processing circuitry to create inverted-phase components that cancel out unwanted harmonic frequencies

Methodology Applied

Scientific EffectDestructive interference: Interference

Data Source

PatentUS11552655B2Digital radio frequency transmitter and wireless communication device including the same

Publication Date: 2023.01.10 SAMSUNG ELECTRONICS CO LTD

AI summary

A digital radio frequency (RF) transmitter including processing circuitry configured to generate first through third pattern signals based on a pattern of an inphase (I)-quadrature (Q) binary data pair and a pattern of an inverted I-Q binary data pair, the first through third pattern signals having a same pattern and different phases, and a switched-capacitor digital-to-analog converter (SC-DAC) configured to remove an n-th harmonic component of an RF analog signal by amplifying the first through third pattern signals to have a certain magnitude ratio and synthesizing the amplified first through third pattern signals into the RF analog signal, where “n” is an integer of at least 3, may be provided.