Multiband Antenna Impedance Matching LC Resonance Circuit
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Solution Overview
Problem
Existing multiband antennas face challenges in achieving wide-band characteristics on the low frequency band side, particularly in mobile phone terminals, due to size and thickness limitations, making it difficult to simultaneously cover multiple frequency bands like GSM 850 and GSM 900 without increasing the physical volume of the antenna.
Innovation Solution
The integration of an impedance matching unit, specifically an LC parallel resonance circuit, into the high band antenna element allows it to operate and tune to the low band frequency, effectively enhancing the wide-band characteristics on the low band side while maintaining high band performance, by optimizing the inductance and capacitance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single antenna element is used to cover multiple frequency bands, then the device complexity is reduced, but the antenna efficiency on the low band side deteriorates due to size and thickness limitations
Solution Approach 1:
The patent changes the electrical parameters of the antenna element by introducing an LC parallel resonance circuit that creates an open-circuited impedance at the resonance frequency. This transforms the antenna element's electrical characteristics, making it appear electrically shorter at high frequencies while maintaining physical dimensions suitable for low band operation, thereby improving low band antenna efficiency without increasing physical size
Solution Approach 2:
The LC parallel resonance circuit acts as an intermediary component inserted into the antenna element. It mediates between the physical antenna structure and the electromagnetic waves at different frequencies, creating frequency-dependent impedance transformations that enable the single antenna element to efficiently operate across multiple bands, particularly improving low band performance
2Reliability
If the antenna element length is increased to improve low band characteristics, then the antenna efficiency on the low band side is improved, but the physical volume of the antenna increases
Solution Approach 1:
The patent transforms the electrical length of the antenna element through the LC parallel resonance circuit, which creates an open-circuited impedance at the resonance frequency. This allows the antenna to achieve the electrical characteristics of a longer antenna for low band operation while maintaining a compact physical size suitable for mobile phone terminals, effectively decoupling electrical length from physical length
3Adaptability or versatility
If an LC parallel resonance circuit is inserted into the antenna element to widen the band, then the wide-band characteristics on the high band side are improved, but the antenna efficiency on the low band side deteriorates
Solution Approach 1:
The patent optimizes the parameters of the LC parallel resonance circuit, specifically positioning it at a frequency between the low and high bands and adjusting its inductance and capacitance values. This creates an impedance transformation that improves high band characteristics while the resonance circuit's specific configuration prevents deterioration of low band efficiency, allowing the antenna to maintain good performance across both bands
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances antenna efficiency on the low band side, reduces the physical size of the antenna, and allows for simultaneous coverage of multiple frequency bands, addressing the limitations of existing designs by making the high band antenna element operable across both low and high bands.
Implementation Method 1
an LC parallel resonance circuit is provided on an intermediate part of an antenna element. In the case that the LC parallel resonance circuit is provided on the intermediate part of the antenna element, its impedance is open-circuited at a resonance frequency of parallel resonance, so that current hardly flows to the open end side of the antenna element beyond the LC parallel resonance circuit
Implementation Method 2
the antenna elements on the lower frequency band side and the higher frequency band side are capacitive-coupled together in their respective operation bands
Data Source
Figure 1~2
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Figure 4
AI summary
A multiband antenna includes at least two antenna elements for use in a low frequency band and a high frequency band, a feeding point unit configured to be shared by both of the antenna elements for use in the low frequency band and the high frequency band and an impedance matching unit configured to be inserted into and connected to a position between an end of the antenna element for use in the high frequency band on the side of the feeding point unit and an open end thereof.