Folded Monopole Antenna for MIMO Mode Isolation
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Solution Overview
Problem
Mobile devices face challenges in accommodating multiple wireless communication applications with limited space, leading to coupling and mode isolation issues among antennas, which disrupt MIMO performance and make it difficult to cover various frequency bands with a single radiator.
Innovation Solution
A compact, three-dimensional folded monopole antenna design with high mode isolation, allowing independent adjustment of operational frequency bands and low coupling between radiation elements, enabling coverage of multiple frequency bands such as GSM, UMTS, GPS, and LTE within a small form factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple antennas are placed in close proximity to support multiple wireless applications, then the device can cover more frequency bands and applications, but coupling and mode isolation problems occur which disrupt MIMO performance
Solution Approach 1:
The patent employs three-dimensional folded monopole structures that extend in multiple spatial dimensions rather than simple planar configurations. The antennas are folded back on themselves in 3D space, creating complex spatial arrangements that increase mode isolation while maintaining compact footprint. This dimensional approach allows multiple antennas to coexist in limited space without excessive coupling.
Solution Approach 2:
The antenna elements are divided into multiple segmented sections that are folded and arranged in specific three-dimensional configurations. Each segment can be independently optimized for different frequency bands, and the segmentation allows for better control of current distribution to reduce coupling between adjacent antenna elements.
2Device complexity
If a single radiator is used to cover multiple frequency bands, then the device complexity is reduced, but it becomes difficult to independently adjust specific frequency bands and cover all required bands such as GSM 900 and GSM 1880/1900 together
Solution Approach 1:
The folded monopole antenna structure serves multiple functions simultaneously: it provides impedance transformation, frequency band selection, and radiation functionality all within a single integrated element. The same folded structure that reduces size also enables independent adjustment of different frequency bands through strategic placement of feed points and grounding schemes.
Solution Approach 2:
Different sections of the folded monopole antenna have locally optimized properties for different frequency bands. Specific segments are dimensioned and positioned to resonate at particular frequencies, allowing each local region of the antenna to be tailored for specific band coverage while the overall structure maintains compactness.
3Adaptability or versatility
If monopole antenna size is increased to operate at lower resonant frequency bands, then the antenna can cover lower frequency bands, but the antenna size increases which is not desirable for handheld devices
Solution Approach 1:
Instead of increasing antenna length in a single dimension to achieve lower frequency operation, the patent folds the monopole structure into three-dimensional configurations. This allows the electrical length to be extended while the physical footprint remains compact, enabling lower frequency band coverage without proportionally increasing overall antenna volume.
Solution Approach 2:
The folded monopole structure contains multiple electrical lengths nested within a compact physical envelope. The antenna folds back on itself, creating a nested configuration where the effective electrical path length is much greater than the external dimensions, enabling lower frequency operation in a small volume.
Data Source
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AI summary
A multi-band antenna (108) comprising a dielectric substrate (104), a ground plane formed on a first area of the dielectric substrate, a radiation part arranged in a second area of the dielectric substrate where the ground surface is not formed, a feed section (112) formed of a metallic trace and having one end connected to the radiation part and an opposite end disposed near an edge of the ground plane for forming a feed point and the radiation part having a pair of monopole antenna elements formed of conductive metallic traces (110).