Reconfigurable Acquisition Engine for Spread Spectrum Signals
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Solution Overview
Problem
Direct sequence spread spectrum receivers, such as GNSS receivers, face inefficiencies due to fixed-size Fast Fourier Transform (FFT) implementations that result in increased size, weight, power, and cost (SWaP-C), as they require large memory for varying time-frequency uncertainties and jamming mitigation, leading to manufacturing yield issues and high costs.
Innovation Solution
A reconfigurable acquisition engine with a frequency-domain decimation filter that reduces output frequency points while maintaining information from all frequency bins, allowing for software-controllable parameters to enhance time and frequency coverage without increasing memory size, thereby reducing SWaP-C and enabling flexible operation across different use cases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed-size FFT with NCI memory is used for the worst case scenario, then the acquisition engine can find the DS SS signal position with sufficient accuracy, but the size, weight, power, and cost (SWaP-C) of the receiver increases
Solution Approach 1:
The patent implements a reconfigurable acquisition engine that dynamically adjusts FFT size and NCI memory configuration based on operational requirements. The system can switch between different FFT sizes (e.g., 64-point, 128-point, 256-point) and memory depths, allowing it to optimize for worst-case scenarios only when necessary, rather than always operating with maximum resources allocated. This dynamic reconfiguration resolves the contradiction by making the system adaptive to actual signal conditions.
Solution Approach 2:
The system changes key parameters including FFT size, coherent integration time, and frequency bin spacing based on operational mode. By adjusting these parameters, the system can reduce memory requirements and computational load when worst-case conditions do not exist, while maintaining sufficient signal acquisition capability. The patent specifically mentions reconfiguring integration times and frequency coverage to reduce memory growth by four times.
2Adaptability or versatility
If time coverage and frequency coverage are increased, then the search space coverage is improved, but the memory size on the ASIC increases multiplicatively
Solution Approach 1:
The patent segments the frequency spectrum into multiple bands and processes them using different FFT sizes and memory configurations. Instead of allocating memory for the entire frequency range at maximum resolution simultaneously, the system divides the search space and allocates resources segmentally, reducing overall memory requirements while maintaining comprehensive coverage capability.
Solution Approach 2:
The system introduces frequency decimation as an additional dimension of processing. By decimating frequency bins selectively, the system extends frequency coverage without proportionally increasing memory requirements. This dimensional approach allows the system to cover broader frequency ranges by processing at different frequency resolutions in different regions of the spectrum.
3Ease of manufacture
If a fixed coherent integration time is used, then the integrator is optimized for one CONOP, but it cannot adapt to varying time-frequency uncertainties and jamming threats
Solution Approach 1:
The patent creates a universal acquisition engine that can perform multiple functions across different concepts of operation (CONOPs). The reconfigurable integrator can adapt its coherent integration time and frequency coverage parameters to suit different operational scenarios, including weak signal acquisition, jamming mitigation, and rapid re-acquisition. This multi-functionality eliminates the need for separate optimized integrators for each CONOP.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor signal conditions and automatically adjust integration parameters. Based on detected signal strength, frequency offset, and potential jamming conditions, the acquisition engine dynamically modifies its integration time and frequency bin spacing, enabling adaptive optimization without manual reconfiguration for each CONOP.
Data Source
AI summary
A configurable acquisition engine for direct sequence (DS) spread spectrum (SS) is provided that is reconfigurable without increasing memory size for several use cases having different time-frequency uncertainties. The acquisition engine utilizes a frequency-domain decimation filter to reduce the number of output frequency points while still utilizing information from all frequency bins.