Digital Spectrometer Interferer Excision
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Solution Overview
Problem
Current communication systems face challenges in receiving small signals due to large unwanted signals in the same frequency band, leading to co-site interference, which limits spectrum efficiency, reduces the detection of small signals, and increases vulnerability to interception, especially in military and maritime communications.
Innovation Solution
A digital spectrometer with autocorrelation capabilities and a mixed-signal RF architecture that uses coarse and fine resolution ADCs to determine the location of large signals, allowing for the excision of interferers through tunable notch filters, enabling real-time spectral monitoring and efficient processing of signals of interest.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a nonlinear analog mixer is used for frequency translation, then the signal can be downconverted to baseband for analysis, but spectral pollution occurs including intermodulation distortion and harmonics
Solution Approach 1:
The patent replaces the nonlinear analog mixer with a digital signal processor that performs frequency translation through mathematical operations (mixing with complex exponentials in the digital domain). This substitution eliminates the physical nonlinearities of analog components while achieving the same frequency conversion function, thereby removing the source of intermodulation distortion and spectral pollution.
Solution Approach 2:
The patent introduces a digital buffer and digital signal processing stage as an intermediary between the analog antenna and the final spectral analysis. This digital intermediary processes the signal in the digital domain where precision is maintained, avoiding the spectral pollution that would occur with direct analog mixing while still enabling frequency translation and baseband conversion.
2Measurement precision
If a swept narrowband spectrometer is used, then frequency translation can be performed, but real-time spectral analysis cannot be achieved due to limited sweep speed
Solution Approach 1:
The patent replaces the periodic mechanical sweep of a narrowband spectrometer with continuous real-time digital processing. Instead of periodically sweeping through frequencies, the system continuously processes the entire bandwidth using digital signal processing techniques (such as FFT), achieving both high frequency resolution and real-time spectral analysis capability simultaneously.
Solution Approach 2:
The patent replaces the mechanical frequency sweep mechanism with a digital signal processor that can analyze the entire spectrum simultaneously through mathematical transformations. This substitution eliminates the speed limitation of mechanical sweeps while maintaining or improving frequency resolution through digital processing algorithms.
3Adaptability or versatility
If the entire band is downconverted to baseband using a nonlinear mixer, then wideband spectral analysis is enabled, but spectral pollution from the mixer affects all frequency components
Solution Approach 1:
The patent replaces the broadband nonlinear analog mixer with a digital signal processing system that handles wideband signals. By performing frequency translation and spectral analysis in the digital domain, the system achieves wideband coverage without introducing the spectral pollution that would result from broadband analog mixing, as digital operations do not generate intermodulation distortion.
4Measurement precision
If a high dynamic range digitizer is used to handle both large interferers and small signals, then the full spectrum can be digitized, but the digitizer becomes saturated or dominated by large signals
Solution Approach 1:
The patent segments the signal processing into multiple stages: an initial stage that handles large signals and identifies interferers, followed by a second stage that focuses on detecting small signals of interest. This segmentation allows the system to process signals across a wide dynamic range without saturation, as each stage is optimized for its specific signal level range rather than requiring a single digitizer to handle the entire range simultaneously.
Solution Approach 2:
The patent performs preliminary processing to identify and characterize large interferer signals before attempting to detect small signals of interest. By first analyzing the spectrum to locate dominant interferers and then using this information to guide subsequent detection efforts, the system prevents large signals from dominating or saturating the detection process, thereby improving the reliability of small signal detection.
Data Source
AI summary
A processor, comprising a first data input configured to receive a stream of samples of a first signal having a spectral space, the stream having a data rate of at least 4 GHz; a second data input configured to receive a stream of samples of a second signal; a multitap correlator, configured to receive the first stream of samples and the second stream of samples, and producing at least one correlation output for each respective sequential sample of the first signal received; and a programmable control configured to alter a relationship of the stream of samples of the first signal and the stream of samples of the second signal, to thereby select, under program control, an alterable correlation output.