Antenna Impedance Matching via Negative Inductance

Solution Overview

Problem

Existing antenna devices for communication terminal apparatuses face challenges in achieving impedance matching over a wide frequency band due to increased insertion loss and complex circuit configurations, particularly with multiple resonant circuits and tunable antennas.

Innovation Solution

An antenna device with an impedance converting circuit that includes a first and second inductance element transformer-coupled to generate an equivalent negative inductance component, reducing the effective inductance of the antenna element and achieving impedance matching across a wide frequency band.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple resonant circuits are used in the matching circuit, then impedance matching can be achieved, but insertion loss increases and sufficient gain cannot be obtained

Engineering Contradiction:

Improveimpedance matchingVSAvoidinsertion loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the electrical parameters of the matching circuit by using a single resonant circuit with variable inductance and capacitance values. The inductance is changed by switching between different coil elements (L1a, L1b, L1c) and the capacitance is changed by switching between different capacitor elements (C1a, C1b, C1c), allowing the circuit to achieve impedance matching across multiple frequency bands without requiring multiple resonant circuits, thereby reducing insertion loss.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If a switching circuit for variable capacitance element is used in tunable antennas, then frequency band switching is enabled, but circuit configuration becomes complicated and loss and distortion increase

Engineering Contradiction:

Improvefrequency band switchingVSAvoidcircuit configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the capacitance function into multiple discrete capacitor elements (C1a, C1b, C1c) that can be independently switched. Each capacitor element provides a specific capacitance value, and by selectively connecting different combinations of these segmented capacitor elements, the circuit achieves multiple frequency band switching capabilities with a relatively simple switching structure.

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If a switching circuit for variable capacitance element is used in tunable antennas, then frequency band switching is enabled, but loss and distortion in the switching circuit are large

Engineering Contradiction:

Improvefrequency band switchingVSAvoidloss and distortion

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent changes the electrical parameters of the matching circuit by using a single resonant circuit with variable inductance and capacitance values. The inductance is changed by switching between different coil elements (L1a, L1b, L1c) and the capacitance is changed by switching between different capacitor elements (C1a, C1b, C1c), allowing the circuit to achieve impedance matching across multiple frequency bands without requiring multiple resonant circuits, thereby reducing insertion loss.

Inventive Principle:

Principle #35Parameter changes

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 effectively suppresses impedance changes over a wide band, enabling impedance matching with a power-supply circuit and compatibility with various communication systems, thereby enhancing the antenna's frequency characteristics and radiation efficiency.

Implementation Method 1

a second inductance element L2 transformer-coupled to the first inductance element L1 so as to generate an equivalent negative inductance component

Methodology Applied

Scientific EffectTransformer coupling: Electromagnetic Induction

Data Source

PatentUS9711848B2Antenna device and communication terminal apparatus

Publication Date: 2017.07.18 MURATA MFG CO LTD

AI summary

An antenna device includes an antenna element and an impedance converting circuit connected to the antenna element. The impedance converting circuit is connected to a power-supply end of the antenna element. The impedance converting circuit is interposed between the antenna element and a power-supply circuit. The impedance converting circuit includes a first inductance element connected to the power-supply circuit and a second inductance element coupled to the first inductance element. A first end and a second end of the first inductance element are connected to the power-supply circuit and the antenna, respectively. A first end and a second end of the second inductance element are connected to the antenna element and ground, respectively.