Multi-Branch Receiver Bandwidth Combining Without Guard Bands
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Solution Overview
Problem
Wideband radio receivers face issues with blocking signals causing saturation and inefficiencies due to filter roll-off skirts and the need for guard bands when using multiple narrowband filters to approximate a wider bandpass, resulting in significant bandwidth wastage.
Innovation Solution
A variable bandwidth receiver with multiple branches, each equipped with a narrowband filter, digitally combines signals after analog-to-digital conversion to eliminate guard bands and filter roll-off skirts, allowing for efficient use of bandwidth and minimizing the impact of blocking signals by selecting branches without interference and adjusting automatic gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wideband bandpass filter is used to receive signals over a large frequency band, then the receiver can accommodate variable bandwidth flexibility, but blocking signals with high amplitude can saturate and overpower the entire operation of the wideband receiver
Solution Approach 1:
The wideband frequency range is divided into multiple narrower frequency bands, each handled by a separate receiver branch with its own bandpass filter. This segmentation prevents a single blocking signal from saturating the entire receiver system, as each branch operates independently with its own dynamic range.
Solution Approach 2:
The system dynamically selects and combines receiver branches based on signal conditions. The controller adjusts which branches are active and how their outputs are combined, allowing the receiver to adapt to varying signal environments and avoid blocking signals while maintaining bandwidth flexibility.
2Adaptability or versatility
If multiple narrowband filters are combined to approximate a wider bandpass, then bandwidth flexibility is achieved, but guard bands must be provided between adjacent frequency bands to prevent interference, resulting in wasted bandwidth
Solution Approach 1:
The patent replaces the traditional analog guard band approach with digital signal processing. After analog-to-digital conversion, digital filters and processing techniques eliminate the need for analog guard bands, allowing adjacent frequency bands to be combined more efficiently without physical separation requirements.
Solution Approach 2:
The system changes the operating parameters of the receiver branches dynamically. By adjusting gain, frequency tuning, and combination weights based on detected signal conditions, the system optimizes bandwidth utilization and eliminates the need for fixed guard bands between frequency allocations.
3Measurement precision
If the filter roll-off is narrowed to make the filter more selective, then frequency selectivity is improved, but the passband begins to ripple and the filter becomes more difficult to manufacture with higher precision requirements
Solution Approach 1:
Instead of using a single filter with a steep roll-off, the patent segments the frequency filtering into multiple narrower bands, each with gentler roll-off characteristics. This makes each individual filter easier to manufacture while achieving the same overall frequency selectivity through the combination of multiple filters.
Solution Approach 2:
The patent introduces digital signal processing as an intermediary between the analog filters and the final output. Digital filters and processing techniques compensate for the gentler analog filter roll-off, achieving the required frequency selectivity without requiring extremely steep analog filter characteristics that would be difficult to manufacture.
Data Source
AI summary
A variable bandwidth receiver uses allocated bandwidth more efficiently and ensures that blocking signals do not overload receiver components. The receiver includes multiple branches for receiving a first bandwidth signal. Each receiver branch has a filter for passing signals in a frequency band corresponding to a second bandwidth less that the first bandwidth and an analog-to-digital converter for converting the baseband signal into a digital signal. A controller digitally combines the digital signals from two or more of the receiver branches to produce a received signal having a bandwidth substantially wider than the first bandwidth. Because combining is done after analog-to-digital conversion in the digital domain, the controller can combine the digital signals from two or more of the receiver branches having adjacent corresponding frequency bands without the normal guard band separating them.