Antenna Module Ground Electrode Structure for Bandwidth
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Solution Overview
Problem
Existing antenna modules face challenges in reducing transmission line loss and suppressing cross polarization discrimination (XPD) due to the influence of substrate thickness, which degrades antenna characteristics when the feed line is shortened.
Innovation Solution
The antenna module incorporates a substrate with a ground electrode featuring a first and second ground pattern, where the second ground pattern is provided above the first and includes a through hole for the feed line, allowing the feed line to be surrounded by a ground conductor, thereby increasing the distance between the radiation electrode and the ground electrode, reducing electric field density, and improving antenna characteristics while shortening the feed line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the substrate thickness is reduced to shorten the feed line, then transmission line loss is suppressed and XPD is improved, but the distance between the radiation electrode and ground electrode decreases, degrading antenna characteristics (bandwidth)
Solution Approach 1:
The ground electrode is configured with a stepped structure having a first ground pattern and a second ground pattern at different heights. The feed line passes through a through-hole in the second ground pattern, allowing the feed line to be surrounded by ground conductors. This three-dimensional ground electrode structure increases the effective distance between the radiation electrode and ground electrode in the vertical dimension while maintaining a thin overall substrate profile, thereby improving bandwidth without increasing substrate thickness.
Solution Approach 2:
The feed line is nested within the ground electrode structure by passing through the through-hole of the second ground pattern. The ground conductors surrounding the feed line are integrated into the ground electrode, creating a nested configuration where the feed line is enclosed by ground structures. This nesting allows the feed line to be effectively shielded and positioned optimally without increasing the overall substrate thickness.
2Length of moving object
If the feed line is shortened by thinning the substrate, then transmission line loss is suppressed, but the radiation electrode and ground electrode become closer, degrading antenna characteristics
Solution Approach 1:
The ground electrode utilizes vertical dimensionality with stepped patterns at different heights. The first ground pattern is at a lower height while the second ground pattern with the through-hole is at a higher height. This vertical arrangement creates an effective larger separation distance between the radiation electrode and the ground electrode structure, improving bandwidth characteristics even when the substrate thickness is reduced to shorten the feed line.
3Area of stationary object
If the second ground pattern is expanded outside the radiation electrode, then the distance between ground electrode and radiation electrode is reduced, but this hinders improvement of antenna characteristics
Solution Approach 1:
The second ground pattern is strategically positioned and sized to be substantially within the radiation electrode in plan view. This localized configuration ensures that the ground electrode provides effective electromagnetic coupling and grounding function while maintaining appropriate distance from the edges of the radiation electrode. The local quality of the ground electrode structure is optimized to improve bandwidth without degrading antenna characteristics.
Data Source
AI summary
An antenna module includes a substrate, a RF signal processing circuit provided on the substrate, a ground electrode provided on the substrate above the RF signal processing circuit, a radiation electrode provided on the substrate above the ground electrode, and a feed line provided in an overlapping area where the radiation electrode and the RF signal processing circuit overlap, the feed line connecting the radiation electrode and the RF signal processing circuit, wherein the ground electrode includes a first ground pattern, a second ground pattern, and a peripheral wall connecting the first ground pattern and the second ground pattern, the peripheral wall surrounds part of the feed line, and the second ground pattern has a through hole through which the feed line penetrates.