Vehicular Half Loop Antenna Bandwidth and Isolation
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Solution Overview
Problem
Monopole antennas used in low profile vehicular antenna devices for cellular signals fail to meet bandwidth and gain requirements, especially at lower frequency bands, and require improved isolation between multiple cellular antennas.
Innovation Solution
The implementation of vehicular half loop antennas with a ground section and a feed section, where the feed section has a tapered or curved outer edge, and the antennas are arranged to face each other's ground sections to increase isolation, allowing for wider bandwidth and improved impedance matching across frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If monopole antennas are used in low profile vehicular antenna devices, then the device can be compact, but bandwidth and gain requirements cannot be met, especially at lower frequency bands
Solution Approach 1:
The antenna is divided into two separate feed portions (first feed portion and second feed portion) that are connected via a corner portion. This segmentation allows each portion to be optimized for different frequency ranges, with the first feed portion handling lower frequencies and the second feed portion handling higher frequencies, thereby achieving wide bandwidth performance in a compact low-profile structure
Solution Approach 2:
The antenna transitions from a traditional monopole structure to a half-loop configuration that utilizes the vertical dimension more effectively. The loop structure extends in the vertical direction, creating additional electrical length without increasing horizontal footprint, which improves gain and bandwidth performance at lower frequencies while maintaining a compact form factor
2Adaptability or versatility
If multiple cellular antennas are utilized in the LPA device, then MIMO functionality is achieved, but sufficient isolation between these cellular antennas needs to be ensured
Solution Approach 1:
The ground section acts as an intermediary element between the two half-loop antennas. By positioning the ground sections to face each other, they create an electromagnetic barrier that reduces coupling between the antennas, thereby maintaining sufficient isolation for MIMO operation while allowing the antennas to be placed in close proximity for compact device design
3Reliability
If the corner portion has a curved or tapered outer edge, then impedance matching is improved across frequency bands, but manufacturing complexity increases
Solution Approach 1:
The corner portion is designed with a curved or tapered outer edge instead of a sharp angle, which gradually transitions the impedance along the feed section. This geometric parameter change creates a smooth impedance transformation that improves matching across a wide frequency range, reducing reflections and enhancing bandwidth performance
Data Source
AI summary
A vehicular half loop antenna is provided that includes a ground section and a feed section. The ground section has a ground point that is configured to be electrically grounded. The feed section is configured to be electrically connected to the ground section. The feed section includes a first feed portion having a feed point that is configured to be electrically connected to an antenna feed, and a second feed portion connected to the first feed portion via a corner portion therebetween, with the corner portion being located farther from the ground point than the feed point and having a curved or tapered outer edge.