Frequency Hopping Receiver Architecture for Navigation Signal Tracking
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Solution Overview
Problem
Existing receiver architectures face challenges in acquiring and tracking spread spectrum navigation signals with changing subcarriers, particularly Frequency Hopping (FH) CDMA signals, due to vulnerability to jamming and multipath propagation, and require flexible predetection integration times to optimize signal-to-noise ratio and mitigate multipath effects.
Innovation Solution
A receiver architecture that allows independent selection of predetection integration time, using a carrier wipe off unit, frequency hopping wipe off unit, replica signal generation, and correlation/integration unit to generate and combine replica signals based on sojourn time and user environment, enabling optimal signal processing and phase jump anticipation through ionospheric TEC evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency hopping is used to transmit navigation signals, then resistance to jamming is improved, but signal acquisition and tracking complexity increases
Solution Approach 1:
The receiver divides the frequency hopping signal processing into separate functional blocks: a carrier wipe-off unit that processes carrier frequency, a code correlation unit that processes spreading codes, and a frequency hop detection unit that tracks frequency changes. This segmentation allows each unit to handle specific aspects of FH signal processing independently, reducing overall system complexity while maintaining anti-jamming performance.
Solution Approach 2:
The patent introduces an intermediary frequency wipe-off unit that removes the frequency hopping component from the received signal before correlation processing. This intermediary step simplifies the subsequent correlation operation by converting the FH signal into a form that can be processed using conventional correlation techniques, thereby reducing acquisition and tracking complexity.
2Measurement precision
If predetection integration time is increased to improve signal-to-noise ratio, then weak signal detection is improved, but multipath degradation increases
Solution Approach 1:
The receiver implements dynamic predetection integration time adjustment based on signal conditions and multipath environment. The system can adaptively select integration time periods that optimize the balance between noise filtering and multipath mitigation, allowing longer integration for weak signals in benign environments and shorter integration when multipath is present.
Solution Approach 2:
The patent enables change of the integration time parameter according to detected signal characteristics and environmental conditions. By making the integration time a variable parameter rather than a fixed value, the system can optimize performance for different signal strengths and multipath scenarios, improving weak signal detection while limiting multipath effects.
Data Source
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AI summary
The invention relates to a receiver (10.1-10.4) for acquiring and tracking a spread spectrum navigation signal with changing subcarriers, wherein the spread spectrum navigation signal has a carrier signal changing between several subcarriers according to a hopping frequency and being modulated with data and a pseudorandom noise code signal, wherein the receiver comprises a carrier wipe off unit (16; 17) for down converting a received spread spectrum navigation signal from its carrier frequency to a baseband frequency, a frequency hopping wipe off unit (36; 17) for wiping off the hopping frequency from the received spread spectrum navigation signal, a replica signal generation unit (26, 28, 30, 32, 34) for generating at least one replica signal of the pseudorandom noise code signal for acquiring and tracking the received spread spectrum navigation signal after carrier wipe off, wherein the generation of the at least one replica signal is performed depending on a sojourn time THi of the spread spectrum navigation signal at a subcarrier and a selected predetection integration time Tint, and a correlation and integration unit (24) for correlating and integrating the received spread spectrum navigation signal after carrier wipe off with the at least one replica signal for the selected predetection integration time Tint.