Interference Detection in Narrowband and Wideband Radios
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Solution Overview
Problem
Current avionics communication and navigation radios face high costs due to the need for high-end processors and crystal filters in FFT-based techniques and narrowband IF filters, making it challenging to achieve low-cost signal interference rejection, especially in aerial vehicles like UAM and UAS.
Innovation Solution
A radio receiver system utilizing tunable RF notch filters, a low-noise amplifier, a splitter, a processor, a surface acoustic wave filter, and analog-to-digital converters to detect and reject interference signals without requiring high-end processors or crystal filters, allowing for cost-effective interference frequency estimation and rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If FFT-based techniques are used for interference rejection, then interference rejection capability is improved, but processor cost and complexity increase
Solution Approach 1:
The patent extracts the interference rejection function from the main signal processing path by using a separate detection path with dedicated components (detector, SAW filter, ADC) that operate independently. This allows interference detection and notch filter configuration without burdening the main processor, resolving the contradiction between interference rejection capability and processor cost.
Solution Approach 2:
The patent introduces intermediary components including a detector, SAW filter, and ADC that bridge the gap between RF signal reception and processor-based control. These intermediaries perform preliminary processing and filtering, reducing the computational burden on the main processor while maintaining effective interference rejection.
2Reliability
If narrowband IF crystal filters are used for interference rejection, then interference rejection is improved, but component cost increases
Solution Approach 1:
The patent replaces expensive narrowband IF crystal filters with tunable RF notch filters that can be reconfigured electronically. This substitution uses lower-cost components that achieve the same interference rejection function through software-controlled tuning rather than expensive fixed-frequency crystal filters.
Solution Approach 2:
The patent transitions from static crystal filters with fixed frequency responses to dynamic RF notch filters that can be electronically tuned to different frequencies. This dynamic capability allows a single filter component to replace multiple fixed-frequency crystal filters, reducing overall component cost while maintaining interference rejection effectiveness.
3Productivity
If high-speed processing is used in wideband receivers, then processing capability is improved, but processor cost and ADC requirements increase
Solution Approach 1:
The patent segments the signal processing function into two separate paths: a main signal path for desired signal processing and a detection path for interference detection. The detection path uses lower-speed processing with dedicated simple components, while the main path handles the primary signal processing. This segmentation allows the system to achieve effective interference rejection without requiring high-speed processing throughout the entire system, reducing processor cost and ADC requirements.
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 system effectively rejects interference signals in both narrowband and wideband receivers, reducing costs and improving accuracy in aerial vehicles by using low-cost components and processing methods, while maintaining signal quality and interference detection precision.
Implementation Method 1
a surface acoustic wave (SAW) filter in signal communication with an output of the mixer, wherein the SAW filter is configured to reject any IF signal generated due to a desired received RF signal and to improve an accuracy and resolution of a detected interference frequency
Data Source
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AI summary
A system comprises a radio receiver including an antenna, tunable RF notch filters that receive a desired RF signal and reject an interference signal, a LNA, a splitter, and a processor. A received RF signal is divided by the splitter and directed along a main signal path and an interference detection path. The interference detection path comprises a mixer that converts the received RF signal to an IF band, a synthesizer, and a SAW filter in communication with the mixer. The SAW filter rejects any IF signal generated due to a desired received RF signal and improves an accuracy/resolution of a detected interference frequency. The processor estimates the interference frequency based on a detected amplitude of signal samples and a synthesizer tuned frequency for that amplitude. If the detected amplitude is more than a threshold, then a control signal is sent to configure the notch filters at the interference frequency.