Tunable Transformer Matching Circuit for Stable RF Power Tuning

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Solution Overview

Problem

Conventional transceiver designs face challenges in covering wider frequency bands due to the limited and fixed passband of matching networks, requiring multiple paths that consume die area and incur high design costs.

Innovation Solution

A tunable transformer with capacitive tuning and additional coils, allowing adjustable resonant frequency through switched coils and multi-tap architecture, enabling a single path to cover multiple frequency bands.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If additional coils are inserted and switched in the transformer to adjust resonant frequency, then resonant frequency tunability is improved, but output power stability deteriorates

Engineering Contradiction:
Improveresonant frequency tunabilityVSAvoidoutput power stability
Core Design Contradiction:
Adaptability or versatilityVSPower

Solution Approach 1:

The patent changes the electrical parameters of the transformer by selectively switching different coil combinations and adjusting the DC inductance through multi-tap connections. This allows the resonant frequency to be tuned across a range while the system dynamically adjusts parameters to maintain output power stability.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The transformer configuration is made dynamic through electronic switching of different coil combinations and real-time adjustment of DC inductance. This dynamic reconfiguration allows the system to adapt to different resonant frequency requirements while maintaining stable output power through automated control.

Inventive Principle:
Principle #15Dynamics

2Power

If DC inductance is made adjustable through multi-tap transformer coils, then output power stability is improved, but device complexity increases

Engineering Contradiction:
Improveoutput power stabilityVSAvoidtransformer structure complexity
Core Design Contradiction:
PowerVSDevice complexity

Solution Approach 1:

The transformer coils are designed with multiple taps that serve dual purposes: they enable DC inductance adjustment for power stability and provide different resonant frequency configurations. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If transformer configuration is changed to tune resonant frequency, then frequency adaptability is improved, but mutual inductance changes causing power variation

Engineering Contradiction:
Improvefrequency adaptabilityVSAvoidoutput power consistency
Core Design Contradiction:
Adaptability or versatilityVSPower

Solution Approach 1:

The system employs feedback control to monitor output power and automatically adjust the DC inductance and coil switching configuration. This feedback mechanism compensates for mutual inductance changes that occur during frequency tuning, maintaining consistent output power across different resonant frequencies.

Inventive Principle:
Principle #23Feedback

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

Reduces the number of required transceiver paths, decreases die area and production costs, and simplifies design complexity while maintaining output power at resonance.

Implementation Method 1

a first coil (102) having a first inductance and coupled to a first node (101), a second coil (104) having a second inductance and coupled to a second node (103)

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a capacitive element (105) having a capacitance and coupled between the first node (101) and the second node (103)

Methodology Applied
Scientific EffectCapacitance: Capacitance

Implementation Method 3

resonant frequency within RF transceiver matching networks to be adjusted

Methodology Applied
Scientific EffectResonance: Resonance

Data Source

PatentEP3716475B1Transmit circuit with a tunable transformer
Publication Date: 2026.04.15 INTEL CORP
  • EP3716475B1 patent drawingFigure 1A
  • EP3716475B1 patent drawingFigure 1B~1C
  • EP3716475B1 patent drawingFigure 2

AI summary

Techniques are disclosed implementing a tunable transformer (L1-L3) with additional taps in at least one of the three coils (102, 104, 106). The tunable transformer enables the resonant frequency within RF transceiver matching networks to be adjusted without substantially impacting the output power at resonance. The tunability of the transformer is partially driven by the insertion of additional coils (106) within the transformer, which are selectively switched and may be further coupled with a tunable capacitance (108). The tunability of the transformer is further driven via the use of at least one multi-tap transformer coil (104), which allows electronic components to be coupled to different coil taps to thereby facilitate an adjustable DC inductance. Doing so counteracts changes in mutual inductance between the non-switched coils, and facilitates the stabilization of output power with shifts in resonant frequency.