GNSS Receiver Layout for Signal Separation
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Solution Overview
Problem
GNSS directional receivers face signal interference issues due to cross-coupling between RF signals from antennas and inherent noise in digital signals, which affect the accuracy of heading and position calculations, and are exacerbated by coaxial cable routing and digital harmonics.
Innovation Solution
The solution involves rearranging the layout of a GNSS directional receiver to place all RF signals underneath the antennas and maintaining a central digital area, using low-voltage differential signals (LVDS) for communication, and separating digital and RF signals to minimize noise and interference, with components mounted on a single printed circuit board to enhance signal reception and processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RF signals are routed through coaxial cables in traditional GNSS receiver layout, then signal transmission is achieved, but digital harmonics interfere with RF signals and noise increases
Solution Approach 1:
The receiver is divided into separate RF and digital signal sections on the circuit board. RF signals are routed through dedicated RF traces away from digital signal paths, physically segmenting the signal domains to prevent digital harmonics from interfering with RF signals.
Solution Approach 2:
The harmful digital harmonic emissions are extracted and isolated from the RF signal path by using separate trace routes and shielding, removing the source of interference from the critical RF processing area.
2Quantity of substance
If cross-coupling between master and slave antenna RF signals is allowed, then signal reception is maintained, but heading and position calculation accuracy deteriorates
Solution Approach 1:
A signal isolating structure is introduced as an intermediary between the master and slave antenna RF signal paths. This structure blocks the cross-coupling path that would otherwise allow RF signals to leak between antennas, preventing measurement errors while maintaining individual signal reception.
3Speed
If digital signals with fast rising edges are used for communication, then data transmission speed is improved, but high harmonics are generated that increase noise in RF bands
Solution Approach 1:
The circuit board layout segments digital signal traces from RF signal traces. Digital signals with fast rising edges are routed on separate layers or adjacent to shielding, preventing their high harmonics from coupling into the RF signal paths while maintaining high-speed data transmission.
4Ease of manufacture
If receiver components are distributed over multiple boards, then ease of assembly is improved, but signal interference and noise increase
Solution Approach 1:
The receiver integrates both RF and digital signal processing components on a single circuit board, merging previously separated functional blocks. This consolidation eliminates inter-board connection paths that would propagate digital harmonics and noise, while the modular functional design maintains ease of assembly.
Data Source
AI summary
An RF/digital signal-separating receiver is provided for GNSS and other RF signals. The receiver includes a first master antenna and a second slave antenna, which are positioned in spaced relation for directional, radio compass applications. First and second downconverters and first and second ADCs are located under the first and second antennas in analog signal areas, which configuration minimizes cross-coupling RF signals from the antennas and reduces noise. The first and second ADSs are connected to respective first and second correlators in a digital signal location, which is centrally located relative to the antennas. The correlators are connected to a microprocessor for computing distances for the received signals, from which the receiver's orientation or attitude is determined. A method of manufacturing receivers with this configuration is also disclosed.