Microstrip Array Antenna Impedance Matching

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Solution Overview

Problem

Conventional series-feed microstrip array antennas face challenges in achieving high gain at high frequencies due to large transmission loss and limited adjustable range of coupling factors, leading to difficulties in achieving desired directivity and impedance matching, which results in increased cross-polarized radiation and reflection.

Innovation Solution

The microstrip array antenna design incorporates a dielectric substrate with a conductive ground plate and strip conductors featuring a linear main feeding strip line and array elements connected via sub-feeding strip lines and stubs, allowing for controlled coupling factors and impedance matching by adjusting the size and position of radiating antenna elements and stubs, thereby reducing cross-polarized components and reflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the element width of radiating antenna elements is increased to achieve a larger coupling factor, then the coupling factor is improved, but the radiation level of cross-polarized waves increases

Engineering Contradiction:

Improvecoupling factorVSAvoidcross-polarized radiation

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The radiating antenna element is segmented into two separate components: a rectangular radiating antenna element and a stub. The stub is connected to the sub-feeding strip line at a position between the main feeding strip line connection and the radiating antenna element connection. This segmentation allows independent optimization of coupling factor (controlled by stub dimensions and position) and cross-polarized radiation (controlled by radiating antenna element geometry), resolving the contradiction between achieving large coupling factor and suppressing cross-polarized radiation.

Inventive Principle:

Principle #1Segmentation

2Device complexity

If a series-feed microstrip array antenna is used to reduce design complexity, then design simplicity is improved, but transmission loss increases at high frequency

Engineering Contradiction:

Improvedesign complexityVSAvoidtransmission loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

A sub-feeding strip line is introduced as an intermediary component between the main feeding strip line and the radiating antenna element. This sub-feeding strip line acts as a matching transformer that improves impedance matching and reduces reflection, thereby reducing transmission loss while maintaining the design simplicity of the series-feed configuration. The stub connected to the sub-feeding strip line further enhances the matching capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If each radiating antenna element is designed independently to achieve desired directivity, then directivity is improved, but the adjustable range of coupling factor becomes limited

Engineering Contradiction:

ImprovedirectivityVSAvoidadjustable range of coupling factor

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

By segmenting the radiating structure into a radiating antenna element and a stub connected via a sub-feeding strip line, the coupling factor becomes adjustable through multiple parameters: stub length, stub width, stub position on the sub-feeding strip line, and sub-feeding strip line dimensions. This provides a much broader adjustable range for coupling factor while maintaining independent design capability for desired directivity patterns.

Inventive Principle:

Principle #1Segmentation

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

This design achieves a larger coupling factor with reduced cross-polarized radiation and improved impedance matching, resulting in enhanced directivity and efficiency of the microstrip array antenna.

Implementation Method 1

allowing for controlled coupling factors and impedance matching by adjusting the size and position of radiating antenna elements and stubs

Methodology Applied

Scientific EffectImpedance matching:

Implementation Method 2

resulting in reduced cross-polarized radiation and reflection

Methodology Applied

Scientific EffectCross-polarized radiation suppression:

Data Source

PatentUS8193990B2Microstrip array antenna

Publication Date: 2012.06.05 DENSO CORP

AI summary

The microstrip array antenna includes a dielectric substrate formed with a conductive ground plate at a back surface thereof, and strip conductors formed on a front surface of the dielectric substrate. The strip conductors includes a linear main feeding strip line, and a plurality of array elements connected to the main feeding strip line, the array elements being disposed at least one of both sides of the main feeding strip line at a predetermined interval along a longitudinal direction of the main feeding strip line. Each of the array elements includes a sub-feeding strip line connected to the main feeding strip line, a rectangular radiating antenna element connected to a terminal end of the sub-feeding strip line, and a stub connected to the sub-feeding strip line. The stub is disposed between the main feeding strip line and the radiating antenna element.