Interleaved Digital Down-Conversion for Narrowband RF Acquisition
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Solution Overview
Problem
Conventional test and measurement instruments, such as oscilloscopes and spectrum analyzers, have limited real-time bandwidth and triggering capabilities, restricting their ability to acquire and process wide bandwidth RF signals effectively, especially when requiring high sample rates and spectral resolution.
Innovation Solution
A distributed digital down-conversion method is implemented across multiple time-interleaved acquisition components, allowing for high sample rates and bandwidths by distributing digital down-conversion functionality, enabling efficient acquisition and reconstruction of spectral data from a narrow frequency band within the aggregate bandwidth, and supporting longer time spans with lower spectral resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single ADC is used for acquisition, then the system is simpler to implement, but the real-time bandwidth and sample rate are limited
Solution Approach 1:
The acquisition system is segmented into multiple ADCs operating in parallel with time-interleaved sampling. Each ADC captures a portion of the total bandwidth, and the combined output achieves a higher aggregate sample rate and bandwidth than a single ADC could provide alone.
2Ease of manufacture
If analog down-conversion is used prior to ADC, then the bandwidth span can be reduced, but expensive RF oscillator and mixer components are required
Solution Approach 1:
The patent replaces analog down-conversion using RF oscillators and mixers with digital down-conversion performed after ADC conversion. This substitution eliminates the need for expensive analog RF components while maintaining the ability to process wide bandwidth signals.
3Duration of action of moving object
If the acquisition memory size is fixed, then the system is more compact, but the acquisition time span is limited
Solution Approach 1:
The system acquires data at a higher sample rate than strictly necessary for the final display bandwidth, capturing more data points than needed. This excessive acquisition is then reduced through digital down-sampling to fit within the fixed memory size while still providing the desired time span and spectral resolution.
4Speed
If time-interleaved acquisition is implemented, then the sample rate and bandwidth are scalable, but the reconstruction of coherent waveform becomes more complex
Solution Approach 1:
The patent merges the down-conversion operations from multiple time-interleaved ADC paths into a single digital down-converter that processes the combined input. This unified approach simplifies the reconstruction process by consolidating what would otherwise be multiple separate down-conversion chains.
Data Source
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AI summary
A digital down-conversion acquisition function includes a key spectral analysis function in a time-interleaved acquisition system (200) to enable acquisitions at very high sample rates and bandwidths. Digital down-conversion (225) allows data compression into acquisition memory for down-converted complex baseband I/Q data within a given frequency range of interest. With a fixed-size acquisition memory, this enables acquisitions over a longer time span, thus enabling a lower spectral resolution bandwidth. These approaches allow down-converted complex baseband I/Q data from a narrow frequency band of interest to be acquired efficiently. Reconstruction of the acquired down-converted waveform from the time-interleaved components stored in each acquisition memory (220) of each distributed acquisition component to result in a coherent waveform is also disclosed.