Wideband Multi-Channel Receiver With Fixed-Frequency Notch Filter
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Solution Overview
Problem
Conventional aviation communication and navigation receivers face challenges in handling wideband RF signals with varying signal strengths, particularly in the VHF communications band, where strong interfering signals can overwhelm weak desired signals, limiting the ability to receive multiple channels simultaneously.
Innovation Solution
A wideband multi-channel receiver architecture utilizing a narrowband fixed-frequency notch filter and digital control to align interfering signals with the filter's rejection frequency, combined with a high-speed analog-to-digital converter to sample the entire band, allowing for simultaneous reception of multiple channels while minimizing signal attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wideband receiver processes signals across the entire VHF COM band simultaneously, then multiple channels can be received at once, but strong interfering signals overwhelm weak desired signals due to excessive dynamic range
Solution Approach 1:
The receiver divides the wideband VHF COM band into multiple narrower frequency segments using multiple parallel narrowband fixed-frequency band-pass filters. Each filter handles a specific frequency portion, allowing the system to process multiple channels simultaneously while maintaining appropriate signal levels for each segment, thus resolving the dynamic range issue.
Solution Approach 2:
The patent introduces an intermediate frequency conversion stage that translates RF signals to a lower IF frequency before they reach the narrowband filters. This intermediate stage allows the system to maintain strong signal rejection capability while preserving weak desired signals, acting as a mediator between the wideband input and the selective filtering stage.
2Object-affected harmful factors
If a single-channel receiver uses a narrowband fixed-frequency band-pass filter for strong signal rejection, then interference is effectively blocked, but only one channel can be received at a time
Solution Approach 1:
The patent segments the single narrowband filter into multiple parallel narrowband filters, each tuned to different frequency centers within the VHF COM band. This allows the system to maintain the strong signal rejection capability of narrowband filters while enabling simultaneous reception of multiple channels through frequency division.
Solution Approach 2:
The receiver system is designed to perform multiple functions simultaneously: it can reject strong interferers on any given channel while also receiving multiple other channels at once. The parallel filter architecture enables the system to serve multiple reception needs concurrently, making it universally applicable for multi-channel operation with interference rejection.
3Object-affected harmful factors
If tunable RF band-stop filters are used to reduce strong interferer strength, then some signal attenuation is avoided, but the transition band is too broad and desired signals are overly attenuated
Solution Approach 1:
The patent replaces broad tunable RF band-stop filters with multiple narrowband fixed-frequency band-pass filters, each tuned to specific frequency centers. This segmentation of the filtering function into narrowband stages provides precise frequency selectivity, allowing strong interferers to be rejected while preserving the transition band sharpness needed to avoid attenuating adjacent desired signals.
Solution Approach 2:
Instead of using a single broad band-stop filter to reject interferers, the patent inverts the approach by using multiple narrowband band-pass filters centered on desired channels. The interferers are rejected indirectly through the frequency selectivity of these narrowband passes, achieving both precise selectivity and effective interference rejection without the transition band problems of tunable RF filters.
Data Source
AI summary
A wideband multi-channel receiver comprises an antenna configured to receive a radio frequency band. A band-pass filter is in signal communication with the antenna, and a low-noise amplifier is in signal communication with the band-pass filter. A mixer is in signal communication with the low-noise amplifier and is configured to translate a radio frequency band to an intermediate frequency (IF) band. A tunable local oscillator is in signal communication with the mixer. At least one fixed-frequency notch filter is in signal communication with the mixer, with the notch filter configured to reject at least one interference signal in the IF band while passing remaining signals in the IF band. An analog-to-digital converter is in signal communication with the notch filter and is configured to convert the remaining signals in the IF band to digital signals.