HCIS Ground Plane Multipath Suppression for GNSS
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Solution Overview
Problem
Global navigation satellite systems (GNSS) face significant errors in position determination due to multipath reception, where antennas receive direct and reflected satellite signals, leading to inaccuracies in time delay and carrier phase measurements.
Innovation Solution
An antenna system featuring a high capacitive impedance surface (HCIS) ground plane and an antenna positioned above it, with specific design parameters to maximize sensitivity to low-elevated satellites while minimizing multipath signal reception, achieved by optimizing the down/up ratio and antenna pattern levels at defined elevation angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional choke-ring antennas are used, then multipath reception is reduced to some extent, but positioning accuracy is limited to 1 cm
Solution Approach 1:
The patent changes the electrical parameters of the ground plane by introducing a periodic structure with specific dimensions (period d, height h) to create high capacitive impedance at GNSS frequencies. This transforms the ground plane from a simple reflective surface to an impedance-based multipath suppression structure, achieving 1 mm positioning accuracy by preventing reflected signals from reaching the antenna while maintaining direct signal reception.
Solution Approach 2:
The patent employs a composite structure combining a periodic array of conductive elements (pins, posts, or plates) mounted on a conductive ground plane. This composite configuration creates the high capacitive impedance surface needed for multipath suppression while maintaining structural integrity and electrical performance, enabling significant improvement over conventional single-material ground planes.
2Object-affected harmful factors
If the ground plane size is increased to reduce multipath, then multipath suppression improves, but the device complexity and space requirements increase
Solution Approach 1:
The patent segments the ground plane into a periodic array of discrete conductive elements spaced at distance d. This segmentation creates multiple localized impedance points that collectively suppress multipath signals across the desired angular range, achieving effective multipath rejection without requiring a uniformly large continuous ground plane structure.
Solution Approach 2:
The patent adds vertical dimension to the ground plane design by mounting conductive elements at height h above the ground plane surface. This three-dimensional configuration creates impedance effects in the vertical dimension that translate to angular selectivity in the horizontal plane, suppressing multipath signals from specific elevation angles without expanding the horizontal footprint excessively.
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 significantly reduces multipath errors, enhancing positioning accuracy to within 1 mm, a substantial improvement over conventional choke-ring antennas which achieve 1 cm accuracy.
Implementation Method 1
the antenna receives signals reflected from the environment around the antenna
Implementation Method 2
An antenna system featuring a high capacitive impedance surface (HCIS) ground plane
Data Source
AI summary
An antenna system for a global navigation satellite system reference base station is disclosed. The antenna system includes an antenna positioned above a high capacitive impedance surface (HCIS) ground plane. Over a specific range of the lateral dimension of the HCIS ground plane and the height of the antenna above the HCIS ground plane, a high level of multipath suppression and high sensitivity for low-elevated satellites can be simultaneously maintained. The HCIS ground plane can be fabricated as a flat conducting plate with an array of conducting elements such as pins, pins with expanded tips, or mushroom structures. Alternatively, the HCIS can be fabricated as a flat conducting plate with a concentric series of choke rings. The antenna system can provide a positioning accuracy of +/â1 mm, an order of magnitude improvement over previous designs.