Differential Power Amplifier Harmonic Tuning for Multi-Band Linearity

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Solution Overview

Problem

Differential power amplifiers in cellular handsets face challenges in achieving linear operation across multiple frequency bands, leading to the need for costly duplex filters, and there is a requirement for improved linearity to reduce the number of power amplifiers and duplexers needed.

Innovation Solution

A differential power amplifier design incorporating an output transformer with a harmonic tuning network, featuring a common-mode inductor and an electronically tunable capacitor, controlled by a digital controller to resonate at the second harmonic frequency, enhancing linearity and power-added efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If duplex filters are added to address second harmonic generation, then linearity is improved, but device complexity and cost increase

Engineering Contradiction:

ImprovelinearityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent converts the harmful second harmonic generation into a beneficial resonance condition by tuning the common-mode inductor and capacitor to resonate at the second harmonic frequency. This resonance creates a high impedance path that naturally suppresses the second harmonic, transforming the harmful effect into a useful filtering mechanism without requiring external duplex filters

Inventive Principle:

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

Solution Approach 2:

The patent introduces a common-mode inductor as an intermediary element in the differential power amplifier circuit. This inductor, combined with a capacitor, forms a resonant circuit that mediates the second harmonic signals, providing natural harmonic suppression without needing additional duplex filter components

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If more power amplifiers are used to cover all frequency bands, then adaptability is improved, but device complexity and real estate usage increase

Engineering Contradiction:

Improvefrequency band coverageVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent makes a single differential power amplifier universal across multiple frequency bands by implementing an electronically tunable harmonic suppression mechanism. The common-mode inductor and capacitor combination, controlled by a digital-to-analog converter, allows the same amplifier to maintain linearity and suppress harmonics across different frequency bands, eliminating the need for multiple dedicated amplifiers

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If more power amplifiers are used to cover all frequency bands, then adaptability is improved, but area of stationary object increases

Engineering Contradiction:

Improvefrequency band coverageVSAvoidhandset real estate

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Manufacturing precision

If fixed tuning capacitors are used in differential power amplifiers, then manufacturing precision is improved, but adaptability worsens

Engineering Contradiction:

Improvetuning precisionVSAvoidfrequency band adaptability

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent replaces fixed tuning capacitors with electronically tunable capacitors that can dynamically adjust their capacitance values. These tunable capacitors, controlled by digital-to-analog converters, allow the power amplifier to adapt to different frequency bands while maintaining precise tuning, combining the benefits of both fixed and variable capacitor approaches

Inventive Principle:

Principle #15Dynamics

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

The solution significantly improves linearity and power-added efficiency, reducing the need for additional duplexers and power amplifiers across various frequency bands, thereby optimizing the use of cellular handset real estate.

Implementation Method 1

tune the first electronically tunable capacitor to resonate with the common-mode inductor at a second harmonic frequency of a signal being amplified

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS20190296703A1Differential power amplifier

Publication Date: 2019.09.26 QORVO US INC

AI summary

A differential power amplifier is disclosed. The differential power amplifier includes an output transformer having a primary winding with a first primary terminal, a center-tap terminal, and a second primary terminal. The differential power amplifier further includes a positive amplifier having a first signal output terminal coupled to the first primary terminal and a negative amplifier having a second signal output terminal coupled to the second primary terminal. A harmonic tuning network is made up of a common-mode inductor coupled between the center-tap terminal and a tuning node and a first electronically tunable capacitor coupled between the tuning node and a fixed voltage node. A controller is configured to tune the electronically tunable capacitor to resonate with the common-mode inductor at a second harmonic frequency of a signal being amplified by the positive amplifier and the negative amplifier.