Programmable RF Front End for Wideband ADC Dynamic Range
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Solution Overview
Problem
Wideband ADCs face challenges with reduced dynamic range due to smaller input voltage swings, increased signal observation, and susceptibility to interfering signals, with existing solutions limited in handling multiple interferers through notch filtering.
Innovation Solution
A programmable RF front end is implemented in an RFSoC-based receiver system, allowing flexible allocation of ADC resources by programming each signal channel with tunable bandpass filters and mixer frequencies to mitigate interference and maintain wideband frequency coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If wideband ADCs are used to capture wide signal bandwidth, then bandwidth coverage is improved, but dynamic range is reduced due to smaller input voltage swings
Solution Approach 1:
The system divides the wide frequency bandwidth into multiple sub-bands using banked bandpass filters, with each filter handling a specific frequency range. This segmentation allows the ADC to process each sub-band separately with optimized dynamic range, avoiding the need to handle the entire wide bandwidth simultaneously at full voltage swing requirements.
Solution Approach 2:
The system dynamically switches between different bandpass filters based on the frequency content of the incoming signal. By adapting which filter is active according to the signal characteristics, the system maintains optimal dynamic range for the current operating frequency while preserving wideband coverage capability.
2Speed
If multiple signals are observed to increase bandwidth coverage, then frequency coverage is improved, but voltage swings increase further stressing the dynamic range
Solution Approach 1:
The bandpass filter bank segments the total frequency spectrum into multiple non-overlapping or minimally overlapping sub-bands. Each filter passes only its designated frequency range to the ADC, ensuring that signals from different frequency ranges are processed separately. This prevents simultaneous large voltage swings from multiple frequency components that would otherwise stress the ADC's dynamic range.
Solution Approach 2:
Each bandpass filter is designed with specific frequency selectivity characteristics tailored to its designated sub-band. This local optimization of filter characteristics ensures that each frequency region is handled with appropriate filtering properties, maximizing signal fidelity while maintaining dynamic range constraints for each local frequency region.
3Object-affected harmful factors
If notch filters are created for each interferer to remove interfering signals, then interference rejection is improved, but the number of interferers that can be handled is limited
Solution Approach 1:
Instead of creating individual notch filters for each interferer, the system segments the frequency spectrum into broad sub-bands using bandpass filters. This approach can reject entire bands of interfering signals simultaneously, handling many more interferers than the number of available filter notches would allow.
Solution Approach 2:
Rather than trying to preserve specific frequency components by creating narrow notches around interferers, the system inverts the approach by blocking broad frequency bands and allowing only desired sub-bands to pass. This band-rejection strategy is more scalable for handling multiple interferers across wide frequency ranges.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively avoids interfering signals while maximizing dynamic range, enabling efficient utilization of multiple ADCs and maintaining near-optimal frequency coverage, particularly in radar and communication systems under difficult interference conditions.
Implementation Method 1
a selection of one of a set of tunable bandpass filters with fixed bandwidths
Implementation Method 2
a down-converter block connected and configured to down-convert conditioned electrical signals
Data Source
AI summary
A receiver includes an antenna block configured to transduce impinging electromagnetic signals into electrical signals; a signal conditioning block configured to condition electrical signals received from the antenna block; and a down-converter block configured to down-convert conditioned electrical signals received from the signal conditioning block. The down-converter block comprises a plurality of signal channels. The receiver further includes a plurality of analog-to-digital converters (ADCs) respectively connected to the signal channels of the down-converter block; and a field-programmable gate array (FPGA). The FPGA is configured to program the down-converter block by selecting a set of mixer frequencies and a set of bandwidths designed to remove interference signals in each signal channel. The selections are calculated to mitigate reductions in dynamic range in the ADCs due to interference. The FPGA is further configured to process digital signals received from the ADCs after the down-converter block has removed the interference signals.