Multi-Band Ranging Using FFT-Aligned Sub-Band Signals
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Solution Overview
Problem
Multi-band communication systems face inaccuracies in range estimation due to limited bandwidth in each sub-band, leading to coarse resolution, which is exacerbated by noise when averaging estimates from different sub-bands.
Innovation Solution
Transmitting the same signal across all sub-bands in different time intervals and processing the received signals to achieve a time resolution proportional to the total bandwidth, using techniques like fast Fourier Transform (FFT) to align and refine the outputs of matched filters, and leveraging phase information to enhance precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the same signal is transmitted in all sub-bands simultaneously, then the time resolution would be proportional to the inverse of the total bandwidth, but interference between sub-bands would occur
Solution Approach 1:
The patent applies periodic action by transmitting the same signal across all sub-bands in different time intervals rather than simultaneously. Each sub-band transmits the signal in alternating time slots, creating a periodic transmission pattern that eliminates inter-sub-band interference while still allowing the receiver to process all sub-bands to achieve time resolution proportional to the inverse of the total bandwidth.
2Ease of manufacture
If conventional correlation method is used in a single sub-band, then the implementation is simple, but the achieved resolution is coarse and proportional to the inverse of the sub-band bandwidth
Solution Approach 1:
The patent merges the outputs of matched filters from all sub-bands by aligning them in time and combining them coherently. This combination allows the system to achieve time resolution proportional to the inverse of the total bandwidth across all sub-bands, rather than being limited to the resolution of a single sub-band, while maintaining implementation feasibility through systematic processing.
3Reliability
If estimates from different sub-bands are averaged to reduce noise effect, then noise reduction is achieved, but the resolution determination remains inaccurate
Solution Approach 1:
The patent replaces the simple averaging method with a coherent combining approach using fast Fourier transform (FFT). Instead of merely averaging the magnitude of estimates from different sub-bands, the system aligns the complex outputs of matched filters and applies FFT to exploit phase information, achieving both noise reduction and accurate resolution determination proportional to the total bandwidth.
Data Source
AI summary
System and methods include transmitting the same signal in all sub-bands in different time intervals and processing the corresponding received signals to achieve a time resolution proportional to the inverse of the whole bandwidth as opposed to that of a single sub-band. The systems and methods refine the coarse resolution that is achieved by conventional approaches, such as the correlation method, in a single sub-band by aligning the outputs of the matched filters to the received signals from all sub-bands and applying a fast Fourier Transform (FFT) in each time bin along the sub-band index.