Phase-Offset Switching Amplifier for Harmonic Cancellation

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Solution Overview

Problem

Amplifiers face challenges in achieving high power efficiency while minimizing co-existence issues with other radio receivers, as polar switching power amplifiers have high power efficiency but generate harmful harmonics, and linear power amplifiers have low efficiency and spectral purity issues.

Innovation Solution

A switched capacitor power amplifier with semi-digital filtering using a modulated sine wave carrier suppresses out-of-band spurs and harmonics by offsetting signal components in phase, allowing for high power efficiency and spectral purity without analog filtering, facilitating integration and increased data rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If polar switching power amplifiers are used to achieve high power efficiency, then power efficiency is improved, but harmful harmonics are generated causing co-existence issues with other radio receivers

Engineering Contradiction:

Improvepower efficiencyVSAvoidharmful harmonics

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The amplifier output is segmented into multiple parallel switching amplifiers (first, second, third amplifiers) that process the same input signal with different phase shifts. This segmentation allows individual amplifiers to maintain high efficiency while their combined output achieves spectral purity through destructive interference of harmonics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different phase shifts (first phase shift, second phase shift, third phase shift) are applied to each amplifier path, creating asymmetric signal processing paths. This asymmetry in phase manipulation enables selective cancellation of harmful harmonics while preserving the desired fundamental frequency components.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 3:

The harmful harmonics generated by switching amplifiers are converted into a benefit through constructive and destructive interference. By carefully controlling phase shifts, the harmonics from individual amplifiers interfere destructively at the output, transforming the harmful byproduct into a mechanism for spectral purification.

Inventive Principle:

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

2Object-generated harmful factors

If linear power amplifiers are used to achieve spectral purity, then harmful harmonics are reduced, but power efficiency deteriorates

Engineering Contradiction:

Improvespectral purityVSAvoidpower efficiency

Core Design Contradiction:

Object-generated harmful factorsVSUse of energy by moving object

Solution Approach 1:

The system segments the amplification function across multiple switching amplifiers rather than using a single linear amplifier. Each segment operates efficiently as a switching amplifier while the collective output achieves linear-like spectral purity through phase-controlled combination.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The phase shift parameters (first phase shift, second phase shift, third phase shift) are adjusted to optimize the balance between power efficiency and spectral purity. By changing these parameters, the system can achieve desirable power efficiency combined with spectral purity comparable to linear amplifiers.

Inventive Principle:

Principle #35Parameter changes

3Object-generated harmful factors

If analog filtering is used to suppress harmonics, then harmful emissions are reduced, but integration difficulty increases and cost rises

Engineering Contradiction:

Improveout-of-band emissionsVSAvoidintegration difficulty

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical/analog filtering approach with a signal processing approach using multiple switching amplifiers and phase shift control. This substitution eliminates the need for external analog filters, enabling direct integration with matching networks and on-chip auto-matching circuits.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The phase-shifting amplifier structure serves multiple functions simultaneously: it provides signal amplification, harmonic suppression, and impedance matching capabilities. This multi-functionality integrates filtering, matching, and amplification into a single unified structure, reducing overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8928401B2Amplifier with filtering

Publication Date: 2015.01.06 NXP BV

AI summary

Signals are processed to facilitate the mitigation and/or cancellation of undesirable components within the signal. As consistent with one or more embodiments, input/delay circuits offset the phase of an input signal, as presented to respective amplifiers. The phase offset is used, upon combination of the outputs of the respective amplifiers, to cancel the undesirable components of the signal. Such an approach may, for example, involve phase offset in a digital domain, with correction upon combination of the signals as presented in an analog domain.