Stub-Loaded Loop Antenna for Multiband Mobile Terminals
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Solution Overview
Problem
Existing antenna devices struggle to achieve a widened frequency bandwidth and multiband construction, particularly for mobile terminal equipment, as signals in lower frequency bands require longer antenna lengths, making it difficult to support multiple frequency bands like 800 MHz, 900 MHz, 1500 MHz, and 1900 MHz simultaneously.
Innovation Solution
The integration of a loop antenna connected to a feed point and ground, with additional stub antennas extending from the loop antenna to cover overlapping and distinct frequency bands, allowing the combination of frequency bands and enhancing bandwidth and multiband capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the antenna length is increased to support lower frequency bands, then the frequency bandwidth is widened, but the device size increases and multiband capability becomes difficult to achieve
Solution Approach 1:
The antenna is divided into multiple functional segments: a loop antenna for the first frequency band and stub antennas extending from the loop for the second frequency band. Each segment is optimized for specific frequency ranges, allowing the overall antenna to cover multiple bands without requiring a single excessively long structure.
Solution Approach 2:
Instead of extending the antenna length linearly to cover lower frequencies, stub antennas are added as dimensional extensions from the loop structure. This transforms the problem from a one-dimensional length issue to a two-dimensional structural configuration, enabling multiband operation within a compact form factor.
2Adaptability or versatility
If a single loop antenna is used for multiband operation, then the structure is simple, but the bandwidth coverage is insufficient
Solution Approach 1:
The loop antenna structure serves multiple functions: it acts as the primary radiating element for the first frequency band while simultaneously providing the base structure from which stub antennas extend to cover the second frequency band. This multi-functional design achieves broad bandwidth coverage without proportionally increasing structural complexity.
Solution Approach 2:
The stub antennas are integrated with the loop antenna structure, sharing common feed points and ground connections. This merging approach allows both the loop and stub elements to work together as a unified antenna system, achieving combined bandwidth coverage while minimizing the number of separate components and connections required.
3Adaptability or versatility
If the loop antenna is extended to cover multiple frequency bands, then the multiband capability is achieved, but the current distribution and gain characteristics deteriorate
Solution Approach 1:
Different parts of the antenna structure are optimized for different frequency bands: the loop antenna portion is optimized for the first frequency band with its specific current distribution pattern, while the stub antenna portions are optimized for the second frequency band. This local optimization ensures that each segment maintains good current distribution and gain characteristics for its designated frequency range.
Solution Approach 2:
The loop antenna structure acts as an intermediary that couples the feed point to both the first and second frequency band operations. By providing a common resonant structure that interacts with both frequency bands, the loop antenna mediates between the different operational requirements, maintaining acceptable current distribution across bands without requiring completely separate antenna systems.
Data Source
AI summary
There is provided an antenna device which includes: a loop antenna connected at one end to a feed point and connected at the other end to ground, and provided to correspond to a first frequency band; and at least one stub antenna provided in the form of extending a part of the loop antenna and provided to correspond to a second frequency band overlapping with a partial frequency band of the first frequency band to which the loop antenna corresponds.