Integrated Antenna Filtering for Harmonic Band Isolation
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Solution Overview
Problem
Existing antenna elements face challenges in minimizing energy reradiation and feedback into the feeding structure due to harmonic overlap between frequency bands, particularly between the HB and CB bands, which affects isolation and RF performance.
Innovation Solution
Incorporating a filter within the antenna element to specifically filter out harmonics of the operating frequency band, allowing the antenna element to attenuate energy from overlapping frequency bands and improve isolation, which can be integrated into a compact design using conductive patterns and parasitic arms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a filter is placed in the feeding network (phase shifter or power divider) to filter out harmonics, then the energy coupled to the feeding network is reduced, but the energy reradiated in the CB frequency band is not reduced
Solution Approach 1:
The patent introduces an intermediary filtering mechanism (band rejection filter) placed between the radiating element and feeding structure. This filter acts as a mediator that selectively blocks harmonic frequencies from being reradiated while allowing fundamental frequencies to pass through, thereby improving isolation between frequency bands without affecting the feeding network performance
Solution Approach 2:
The filter is designed with specific local properties to reject only certain frequency bands (harmonics) while maintaining transparency for the operating band. The filter's frequency-selective characteristics enable it to differentiate between desired and undesired signals at the radiating element level, addressing the isolation problem locally at the antenna element rather than system-wide
2Reliability
If the antenna element is designed to be electrically invisible to each other, then isolation between antenna elements is improved, but the physical dimensions and geometrical configuration become constrained
Solution Approach 1:
The patent modifies the electrical parameters of the antenna element by integrating a filter that changes the impedance and resonance characteristics of the radiating element. This parameter modification enables the element to maintain its physical dimensions while achieving electrical isolation from other elements operating in harmonic bands, effectively decoupling the isolation performance from geometric constraints
3Volume of moving object
If the antenna element is compact in design, then the overall geometrical dimensions are reduced, but the isolation between frequency bands becomes more difficult to maintain
Solution Approach 1:
The patent implements a nested structure where the filter is integrated within the radiating element assembly. The filter is positioned between the radiating element and feeding structure, nesting the filtering function within the existing antenna geometry. This nested configuration enables compact overall dimensions while maintaining the isolation function through the filter's frequency-selective properties
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
The solution effectively reduces energy reradiation and feedback, enhancing isolation between frequency bands, improving the radiation pattern and gain of coexisting antenna elements while allowing for a compact and cost-effective integration within base station antenna systems.
Implementation Method 1
a filter connected to the radiating element and configured to filter out harmonics of the operating frequency band
Data Source
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AI summary
In a first aspect the present invention refers to an antenna element preferably for a base station antenna, the antenna element comprising: a support structure; a radiating structure arranged on or within the support structure, said radiating structure comprising: a radiating element having a resonant frequency inside an operating frequency band of the antenna element; and a filter connected to the radiating element and configured to filter out harmonics of the operating frequency band. In a second aspect the present invention refers to an antenna system comprising a first antenna element according to the first aspect configured to radiate in a first operating frequency band, and a second antenna element configured to radiate in a second operating frequency band, wherein the second operating frequency band overlaps with harmonics of the first operating frequency band.