GNSS Antenna Vertical Screen for Multipath Suppression
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Solution Overview
Problem
Existing GNSS antennas face challenges in achieving low directivity patterns in the bottom hemisphere while maintaining compact dimensions, leading to increased antenna size and height, which affects multipath signal suppression and precision.
Innovation Solution
A patch antenna system with a vertical semitransparent screen featuring slots with pre-set impedance elements that subtract additional electromagnetic fields in the nadir direction, ensuring low directivity patterns in the bottom hemisphere without causing antenna mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lateral dimension of the ground plane is increased to reduce directivity pattern level in the bottom hemisphere, then multipath signal rejection is improved, but the overall antenna size increases
Solution Approach 1:
The patent transitions from controlling directivity solely through the ground plane's lateral dimension to using a vertical dimension by introducing a transparent screen with specific impedance characteristics. This vertical screen element provides additional control over the bottom hemisphere radiation pattern without requiring an increase in the ground plane's lateral dimensions, thus resolving the contradiction between multipath rejection and antenna size.
Solution Approach 2:
The patent employs a composite structure combining the ground plane with a transparent screen that has specific electromagnetic impedance properties. This composite arrangement creates a system where the transparent screen's impedance characteristics work in conjunction with the ground plane to achieve superior directivity control in the bottom hemisphere, improving multipath rejection without proportionally increasing the overall antenna footprint.
2Area of stationary object
If the lateral dimension of the ground plane is reduced to decrease antenna size, then compactness is improved, but directivity pattern level in the bottom hemisphere increases
Solution Approach 1:
By introducing the vertical transparent screen element, the patent adds a new dimension for controlling the radiation pattern. This allows the ground plane's lateral dimension to be reduced for compactness while the transparent screen's vertical impedance characteristics compensate by maintaining low directivity pattern levels in the bottom hemisphere, thus preserving multipath rejection performance.
3Reliability
If the height of the antenna is increased to improve multipath rejection, then directivity control is improved, but the vertical dimension of the receiver increases
Solution Approach 1:
The patent uses a transparent screen that functions as a thin, flexible electromagnetic control element. This screen provides effective directivity control and multipath rejection with minimal vertical thickness, avoiding the need for tall antenna structures while maintaining performance. The screen's thin profile ensures it does not significantly increase the receiver's overall height.
4Reliability
If the transparent screen impedance is optimized to reduce bottom hemisphere directivity, then multipath rejection is improved, but antenna impedance matching becomes more difficult
Solution Approach 1:
The patent systematically varies the transparent screen's impedance parameters (such as sheet resistance or capacitive loading) to achieve the optimal balance between multipath rejection and impedance matching. By treating impedance as a tunable parameter, the design allows for optimization of both performance metrics without requiring overly complex matching networks, as the screen's impedance can be directly adjusted during the design phase.
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 design enables compact antenna dimensions with effective multipath signal suppression, maintaining high precision and reducing the overall size of the antenna system.
Implementation Method 1
current in the vertical semitransparent screen provides additional electromagnetic field which is subtracted from the antenna field in the nadir direction
Implementation Method 2
slots with a set of elements with such pre-set impedance that their availability does not cause antenna mismatch
Data Source
AI summary
An antenna system includes a right-hand circularly polarized antenna for receiving Global Navigation Satellite System (GNSS) signals and located on a receiver housing; a vertical semitransparent screen for providing an Down/Up ratioDU90=DU(θe=90∘)=F(-90∘)F(90∘)of −13 dB or better for at least some GNSS frequencies; the semitransparent screen being connected to a ground plane of the antenna; the ground plane being connected to a conductive receiver housing; the semitransparent screen further comprising a horizontal slot to which sets of lumped impedance elements are connected. Each set includes several lumped elements; where the lumped elements are capacitors and/or inductors and/or resistors; where the lumped elements in each set are connected in parallel or series; and the semitransparent screen including at least 4 segments arranged symmetrically around the center of the antenna and connected to each other.