Multiband Antenna with Series Loops for Low-Profile Cellular Devices
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Solution Overview
Problem
Planar inverted F antennas (PIFA) in hand-portable cellular devices require a minimum height of 6 mm above the ground plane to adequately cover the EGSM band, but this increases the antenna's volume, and reducing the height below 6 mm results in insufficient bandwidth and efficiency, making it challenging to achieve a low-profile, multi-band antenna solution.
Innovation Solution
A multiband antenna design featuring a ground plane, feed point, and an antenna track comprising a series of small and large loops, allowing for a reduced separation distance of 3-4 mm between the antenna track and the ground plane while maintaining sufficient bandwidth and efficiency across multiple frequency bands, including EGSM, USGSM, DCS, and PCS bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the height of the antenna element above the ground plane is increased, then the bandwidth increases and the antenna is able to adequately cover both USGSM and EGSM bands, but the volume occupied by the antenna increases
Solution Approach 1:
The antenna element is divided into multiple segments including a first small loop, a large loop, and a second small loop connected in series. This segmentation allows each loop to contribute to different frequency bands, achieving multiband coverage without requiring increased height above the ground plane.
Solution Approach 2:
The patent transitions from a traditional vertical PIFA structure to a planar loop structure that operates parallel to the ground plane. This dimensional change allows the antenna to achieve resonance at multiple frequencies within a constrained height profile by utilizing the loop configurations and their electromagnetic characteristics.
2Volume of moving object
If the height of the antenna element above the ground plane is decreased, then the volume occupied by the antenna is reduced, but the bandwidth decreases and the antenna is unable to adequately cover EGSM band
Solution Approach 1:
The patent changes the electrical parameters of the antenna by introducing loops with different sizes and configurations. The first small loop, large loop, and second small loop have different inductances and capacitances, creating multiple resonant frequencies that provide adequate bandwidth coverage for EGSM and other bands while maintaining a reduced height profile.
Solution Approach 2:
The antenna employs a composite structure combining multiple loop types (small loops and large loop) with different electrical characteristics. This composite configuration creates a multiband resonant system that achieves sufficient bandwidth and efficiency at reduced heights where a single-structure antenna would fail.
Data Source
AI summary
An antenna having a plurality of resonant frequencies and including a feed point; a ground point; and an antenna track extending between the feed point and the ground point and including, in series, a first small loop, a large loop and a second small loop. In one embodiment, the extension of the antenna track through the first U-shaped small loop displaces the antenna track in a first direction, then the extension of the antenna track through the large U-shaped loop displaces the antenna track in a second direction opposite to the first direction and the extension of the antenna track through the second U-shaped small loop displaces the antenna track in the first direction. A bridge element may be used.