Circularly Polarized Antenna Array for GNSS Multipath Cancellation
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Solution Overview
Problem
Existing antennas and systems for receiving circularly polarized signals, such as those used in GPS and other GNSS systems, suffer from multipath errors due to changes in signal phase, amplitude, and timing delays caused by reflection or refraction, leading to suboptimal performance and accuracy.
Innovation Solution
The antenna system features a series of conductive antenna elements positioned at zero, 90, 180, and 270 degrees radially about a center point, with an impedance matching network and 90-degree phase shifting elements to align and amplify signals, and transformer elements to cancel left-hand circularly polarized signals, ensuring optimal reception of right-hand circularly polarized signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional antennas are used to receive circularly polarized signals, then signal reception is achieved, but multipath errors occur due to reflection and refraction causing phase, amplitude, and timing changes
Solution Approach 1:
The antenna system divides the reception function into four separate antenna elements positioned at 0, 90, 180, and 270 degrees. Each element processes signals independently through dedicated impedance matching networks and phase shifters, allowing precise control over the combined output to eliminate multipath errors while maintaining reliable signal reception.
Solution Approach 2:
The patent employs asymmetric phase shifting where three of the four antenna elements have their phases shifted by 90 degrees relative to the reference element. This asymmetric configuration creates constructive interference for direct signals while producing destructive interference for multipath signals, thereby improving measurement precision without sacrificing reception reliability.
2Reliability
If antenna elements are positioned at multiple angular increments to improve signal reception, then reception coverage is enhanced, but device complexity increases due to additional impedance matching networks and phase shifting elements
Solution Approach 1:
Each antenna element serves multiple functions: it receives signals, undergoes impedance matching, and applies phase shifting. The impedance matching networks and phase shifters are designed to handle both impedance transformation and phase adjustment in a single integrated structure, reducing overall system complexity while maintaining four-element angular diversity for reliable reception.
Solution Approach 2:
The patent systematically varies the phase shift parameter across the four antenna elements (0, 90, 180, and 270 degrees) while maintaining identical physical structures for each element. This parameter-based differentiation allows the system to achieve complex reception patterns without proportionally increasing structural complexity, as each element uses the same hardware configuration with different electrical parameters.
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 effectively cancels multipath errors, enhancing the accuracy and performance of GNSS devices by aligning and amplifying right-hand circularly polarized signals while isolating left-hand circularly polarized signals, thereby improving signal reception and reducing interference.
Implementation Method 1
an antenna array having multiple antenna elements generating input signals successively 90 degrees out of phase
Implementation Method 2
each phase shifting element is coupled to a pair of antenna elements in the antenna array to receive their associated input signals, shift the phase on one signal 90 degrees
Implementation Method 3
The first transformer element comprising a first inductor coupled to both low noise amplifiers that outputs right-hand circularly polarized signals at a second inductor
Data Source
AI summary
Antenna systems for receiving right and left hand circularly polarized signals are disclosed. An antenna system embodiment includes a top printed circuit board (PCB), a ground plane, and an antenna array including four conductive antenna elements positioned at relative zero, 90, 180, and 270 degree increments radially about a shared center point on the PCB, with each antenna element sloping upward in a left-handed direction from the ground plane towards the top PCB and connected to the ground plane and top PCB.