Quarter-Wave Transformer Matching for Compact Broadband Power Amplifiers

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Solution Overview

Problem

Existing broadband power amplifiers face challenges in miniaturization and integration due to complex circuit structures and high characteristic impedance, leading to increased size, cost, and matching circuit losses, which limit their adoption in next-generation mobile communication systems.

Innovation Solution

A broadband power amplifier design featuring a simple circuit structure with low characteristic impedance quarter wave transformers, utilizing two-section input or output matching circuits, and employing micro-strip lines, π-networks, or T-networks to reduce the number of passive devices and minimize losses, thereby enabling miniaturization and integration while maintaining broadband characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional matching circuits including two or three inductors, capacitors, and micro-strip lines are used to widen bandwidth, then broadband characteristics are improved, but circuit structure becomes complex and chip size increases

Engineering Contradiction:

Improvebroadband characteristicsVSAvoidcircuit structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines multiple matching circuits into a single integrated matching circuit that serves both the carrier amplifier and peaking amplifier. This unified approach reduces the total number of passive devices (inductors and capacitors) while maintaining broadband matching performance across both amplifiers, thereby simplifying the overall circuit structure without sacrificing adaptability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The matching circuit is designed to perform multiple functions simultaneously: it provides impedance matching for both the carrier amplifier and peaking amplifier across a wide frequency range. This multi-functional design eliminates the need for separate matching circuits for each amplifier, reducing component count and circuit complexity while preserving broadband characteristics.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If conventional matching circuits with multiple passive devices are used, then broadband characteristics are improved, but matching circuit loss increases and efficiency decreases

Engineering Contradiction:

Improvebroadband characteristicsVSAvoidmatching circuit loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

By merging the matching circuits for the carrier amplifier and peaking amplifier into a single shared matching circuit, the total number of passive devices is reduced. Fewer passive devices mean fewer sources of energy loss, thereby reducing overall matching circuit loss and improving amplifier efficiency while maintaining broadband performance.

Inventive Principle:

Principle #5Merging (Combining)

3Volume of moving object

If Doherty amplifiers are realized on PCB packages to reduce size, then miniaturization is achieved, but inductor losses increase and integration on chips is limited

Engineering Contradiction:

Improveamplifier sizeVSAvoidinductor losses

Core Design Contradiction:

Volume of moving objectVSLoss of energy

Solution Approach 1:

The patent replaces traditional PCB-based mechanical implementation with a chip-integrated implementation. By designing the Doherty amplifier and its matching circuits to be realizable on semiconductor chips rather than PCBs, the invention achieves miniaturization while reducing inductor losses through integrated fabrication processes that enable smaller, more efficient inductors with lower parasitic resistance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Adaptability or versatility

If the number of passive devices is increased to widen bandwidth, then broadband characteristics are improved, but circuit cost increases

Engineering Contradiction:

Improvebroadband characteristicsVSAvoidmanufacturing cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent merges multiple matching circuits into a single integrated circuit that serves both amplifiers, thereby reducing the total number of passive devices required. This consolidation maintains broadband matching performance while lowering component count, which directly reduces manufacturing cost and simplifies the fabrication process.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The matching circuit is designed with multi-functionality to handle both carrier and peaking amplifier matching requirements simultaneously across a wide frequency range. This universal design eliminates the need for additional dedicated components, reducing overall circuit cost while preserving broadband characteristics.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8198938B2Broadband power amplifier

Publication Date: 2012.06.12 WIPAM

AI summary

A broadband power amplifier is embodied by realizing a substantially two-section output matching circuit or a substantially two-section input matching circuit using a quarter wave transformer itself as the input matching circuit or the output matching circuit. The broadband power amplifier is advantageous in view of integration and miniaturization due to the low characteristic impedance of the quarter wave transformer and enables both reduction of sizes of chips and circuits due to its simple circuit structure and reduction in cost due to the reduced number of passive devices.