Dual-Fed Patch Antenna Structure for High Port Isolation
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Solution Overview
Problem
Dual-fed patch antennas face challenges in achieving sufficient isolation between ports, particularly in compact designs with omnidirectional patterns and the same polarization, which affects signal-to-noise ratio and noise correlation in wireless communication systems.
Innovation Solution
A dual-fed patch antenna design where a capacitive gap splits the patch into two halves, each shorted to the ground with discrete pins, and a decoupling structure comprising a capacitive meander-shaped gap and shifted periodic linear arrays of shorting pins is used to achieve high isolation without increasing the antenna's height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two closely spaced patch antennas are used to provide radiation pattern diversity, then signal reception in multipath environments is improved, but mutual coupling between antennas increases causing deterioration of receive performance
Solution Approach 1:
A decoupling structure comprising a capacitive meander-shaped gap and two parallel periodic linear arrays of shorting pins is introduced as an intermediary element between the two patch antennas. This decoupling structure acts as a mediator that cancels mutual coupling through mode cancellation, allowing the antennas to operate with high isolation (better than -15 dB) while maintaining compact spacing for diversity operation
2Reliability
If a decoupling structure is added to reduce mutual coupling between ports, then isolation between ports is improved, but device complexity increases
Solution Approach 1:
The patch antenna is segmented into two half-sized patches separated by a capacitive gap. Each half-sized patch is independently fed and shorted to ground with discrete pins. This segmentation allows the antenna to function as a dual-fed system with inherent decoupling capabilities, reducing the need for additional complex decoupling structures while achieving better than -15 dB isolation between ports
Solution Approach 2:
The decoupling mechanism is achieved by transitioning from a full-sized patch to two half-sized patches arranged in a specific geometric configuration with capacitive gap and periodic pin arrays. This dimensional reorganization enables mode cancellation effects that provide high port isolation without requiring additional volumetric space or height, maintaining compactness while improving isolation
3Volume of moving object
If the patch antenna is miniaturized by placing a dielectric slab between the patch and ground plane, then antenna size is reduced, but tuning complexity increases
Solution Approach 1:
The antenna is miniaturized by introducing a dielectric slab between the patch and ground plane, which increases the effective permittivity and reduces the resonant frequency for a given physical size. The resonant frequency is tuned by adjusting the dielectric permittivity parameter of the slab, providing a straightforward method to achieve miniaturization without complex tuning mechanisms
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 effectively cancels mutual coupling between the two ports, allowing them to operate within the same bandwidth as a single half-sized patch, achieving isolation better than −15 dB and maintaining compactness while maintaining radiation pattern diversity.
Implementation Method 1
The two ports are decoupled thanks to the decoupling structure represented by a capacitive meander-shaped gap between the two metal plates
Implementation Method 2
The pins shorting the neighboring half-patches introduce additional inductive coupling
Implementation Method 3
A dielectric slab can be placed between the patch and the ground for miniaturization
Data Source
AI summary
Dual-fed antenna includes a ground plane; first and second metal patch radiators positioned over the ground plane, the first and second metal patch radiators are mirror images of each other; the first and second metal patch radiators separated by a meander-shaped gap, thereby forming an interdigitated structure, with each radiator having at least three digits; each digit shorted to the ground plane using a corresponding metal pin; each radiator having a coaxial feed implemented as a connector connected to it through the ground plane, or an aperture-coupled feed. Matching networks can be connected to the coaxial feeds at both ports or to microstrip lines connected to the slots of the aperture-coupled feeds. Each radiator can have tuning pins on an opposite side of the radiator from the digits, where each tuning pin can have a capacitive load. A dielectric plate can be placed between the radiators and the ground plane.