GPS Receiver Signal Splitter for Memory-Constrained Acquisition
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Solution Overview
Problem
Low-cost GPS/GNSS receivers face limitations in signal bandwidth, sampling rate, and multipath mitigation, leading to reduced performance in acquiring and tracking satellite signals, especially in weak signal environments and dynamic conditions.
Innovation Solution
A low-cost GPS/GNSS receiver design that splits the satellite signal into high and low bandwidth paths, allowing for efficient signal acquisition and tracking using a small snapshot memory, while incorporating a multipath mitigation filter and concurrent FLL and PLL carrier tracking loops to maintain robust signal tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the RF bandwidth is increased to improve positioning accuracy and tracking sensitivity, then the snapshot memory size must be increased, which increases receiver cost
Solution Approach 1:
The patent divides the wideband signal processing into two separate paths: a narrowband path for acquisition using snapshot memory, and a wideband path for tracking. This segmentation allows each path to use optimized bandwidth, enabling accurate tracking with smaller memory requirements in the acquisition path.
Solution Approach 2:
Different bandwidth characteristics are applied to different functional sections of the receiver. The acquisition section uses narrowband filtering appropriate for its purpose, while the tracking section uses wideband filtering. This local optimization allows each section to operate efficiently with appropriate memory resources.
2Reliability
If the RF bandwidth is increased to improve tracking sensitivity, then the snapshot memory size must be increased, which increases receiver cost
Solution Approach 1:
The patent separates acquisition and tracking functions into distinct signal paths with different bandwidth requirements. The tracking path receives wideband signals for high sensitivity, while the acquisition path uses narrowband signals stored in snapshot memory, decoupling the memory size requirement from tracking sensitivity.
Solution Approach 2:
The patent transitions from a single-dimensional approach (storing wideband signals in memory) to a two-dimensional approach (separate narrowband and wideband processing paths). This allows the system to achieve wideband tracking performance without requiring wideband memory storage.
3Ease of manufacture
If a reference oscillator frequency that is an integer multiple of the PN code chipping rate is used to simplify design, then oscillatory errors occur in near-zero Doppler conditions, degrading positioning accuracy
Solution Approach 1:
The patent changes the reference oscillator frequency from an integer multiple of the chipping rate (e.g., 16.368 MHz) to a non-integer multiple (e.g., 16.36767 MHz). This parameter change eliminates the beat phenomenon and oscillatory errors in near-zero Doppler conditions while maintaining design practicality.
Data Source
AI summary
A low-cost GPS/GNSS receiver receives a satellite signal at an RF frequency (fRF). The GPS/GNSS receiver includes a front end section for receiving the satellite signal and generating a digital complex signal having a first bandwidth, the received satellite signal being converted into a complex signal before digitizing, a signal capturing section for searching for and acquiring the satellite signal, the signal capturing section including a capture memory, a baseband processor for tracking the acquired satellite signal, and a signal splitter coupled to the front end section. The signal splitter splits the digital complex signal into two bandwidths, by generating a narrowband digital complex signal having a second bandwidth substantially smaller than the first bandwidth. The signal splitter provides the narrowband digital signal to the capture memory and the wider first bandwidth digital complex signal to the baseband processor.