Multi-Band Antenna Elements With Resonance Suppression Filter
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Solution Overview
Problem
Multiband antennas suffer from interband effects, particularly unwanted resonances in higher band elements at lower frequencies, which disrupt the low band radiation pattern and coupling between polarizations.
Innovation Solution
The introduction of a resonance suppression filter comprising an inductive and capacitive component, positioned to decouple the stalk from the ground plane at lower frequencies, inhibiting quarter-wavelength resonances and suppressing undesirable resonances in higher band elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the higher frequency band radiating elements are arranged close to the lower frequency band elements, then the antenna size is reduced and multi-band operation is enabled, but unwanted resonances occur in the higher band elements at the lower band frequency disrupting the radiation pattern
Solution Approach 1:
An intermediate ground plane is introduced between the lower frequency band ground plane and the higher frequency band radiating elements. This intermediate ground plane acts as a mediator that enables close spacing of antenna elements for compact size while preventing unwanted resonances through frequency-selective coupling - it is coupled to the lower band ground plane at high frequencies but decoupled at low frequencies.
Solution Approach 2:
The electrical coupling between ground planes is changed based on frequency. The intermediate ground plane is designed to be electrically coupled to the lower band ground plane at high frequencies (enabling compact arrangement) but electrically decoupled at low frequencies (suppressing unwanted resonances). This frequency-dependent parameter change resolves the contradiction between compact size and resonance suppression.
2Reliability
If the stalk is coupled to the ground plane, then proper grounding is achieved for signal reference, but quarter-wavelength resonances are excited at lower frequencies causing radiation pattern distortion
Solution Approach 1:
The intermediate ground plane serves as an intermediary grounding reference for the stalk at high frequencies, providing proper signal reference while preventing low-frequency resonance. The stalk remains coupled to the intermediate ground plane for reliable signaling, but the intermediate ground plane's selective coupling to the lower band ground plane blocks the resonance path at low frequencies.
Solution Approach 2:
The grounding system is segmented into multiple ground planes (lower band ground plane, intermediate ground plane) that operate at different frequencies. This segmentation allows the stalk to have a reliable grounding reference at high frequencies while the overall system prevents low-frequency resonances through the frequency-selective properties of the segmented ground structure.
3Object-affected harmful factors
If resonance suppression filters are placed in the signal feed circuit, then unwanted resonances are suppressed, but the signal being fed to the antenna is affected
Solution Approach 1:
The intermediate ground plane acts as an intermediary that provides resonance suppression without interfering with the signal feed circuit. By placing the frequency-selective coupling in the ground plane structure rather than in the signal path, unwanted resonances are suppressed while the signal integrity maintained - the filter function is achieved through the ground structure's electromagnetic properties rather than through circuit elements in the signal path.
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 reduces distortion of the lower frequency radiation pattern and beamwidth by tuning the quarter-wave resonances outside the band of interest, improving signal performance and flexibility in antenna design.
Implementation Method 1
at least one resonance suppression filter, said at least one resonance suppression filter comprising an inductive component and a capacitive component arranged in parallel, said at least one resonance suppression filter being configured to suppress signals in a frequency band that is lower than said higher frequency band
Implementation Method 2
a balun mounted on said stalk and configured to receive and convert an unbalanced signal from an unbalanced signal feed to a balanced signal and to supply said balanced signal to said at least one radiating element
Data Source
AI summary
Antenna elements for multiband antennas are disclosed. A multiband antenna is configured to operate in at least two frequency bands. The antenna element is configured to receive a signal from an unbalanced signal feed and comprises: a stalk configured to be mounted on a ground plane; at least one radiating element extending from the stalk; a balun configured to receive and convert an unbalanced signal from an unbalanced signal feed to a balanced signal and to supply the balanced signal to the at least one radiating element; and at least one resonance suppression filter. The at least one resonance suppression filter comprises an inductive component and a capacitive component arranged in parallel, and in some embodiments a resistive component in series with the inductive component.