Multi-Path Receiver Sub-Band Digitization for Lower IP2 Distortion
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Solution Overview
Problem
High-frequency receivers face challenges in effectively reducing second-order intermodulation products while maintaining signal quality, especially at large bandwidths, due to limitations in existing pre-selection filter approaches which either narrow the usable bandwidth or result in signal energy reduction.
Innovation Solution
A receiver design featuring a filter unit with multiple sub-octave filters arranged in two filter banks, each coupled to an analog-to-digital converter, divides the frequency band into sub-bands for digitization, allowing for minimal signal loss and improved IP2 values by reducing intermodulation products through narrow filter characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pre-selection filters are used to reduce second-order intermodulation products, then intermodulation products are reduced, but the usable bandwidth is significantly narrowed
Solution Approach 1:
The frequency band to be digitized is divided into multiple sub-bands using several pre-selection filters with different center frequencies and bandwidths. Each sub-band is processed separately by its own ADC, allowing the system to maintain narrow filter characteristics for intermodulation reduction while collectively covering a wide frequency range for high usability
2Adaptability or versatility
If the preselection filter bandwidth is widened to increase usability, then more frequency range is available, but second-order intermodulation products increase
Solution Approach 1:
Instead of using a single wide-bandwidth filter, the system segments the frequency band into multiple narrower sub-bands, each filtered by its own pre-selection filter. This maintains the sub-octave filter criterion (relative bandwidth < 1:2) for each filter to suppress intermodulation products, while the collection of filters provides wide overall coverage
3Object-affected harmful factors
If multiple narrow-band filters are used to reduce intermodulation products, then intermodulation products are reduced, but signal energy is lost
Solution Approach 1:
The frequency band is segmented into sub-bands that are processed in parallel through separate reception paths, each with its own narrow-band filter and ADC. This preserves signal energy within each sub-band while suppressing intermodulation products, and the digital combining of sub-bands reconstructs the full signal without energy loss
Solution Approach 2:
The system transitions from a single-channel analog processing approach to a multi-channel parallel processing architecture. By distributing the frequency band across multiple independent reception paths and combining them in the digital domain, the system achieves both intermodulation suppression and signal energy preservation through dimensional expansion
Data Source
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AI summary
The invention relates to a receiver for receiving an analog signal having a frequency band to be digitized, comprising a filter unit having at least two filters for at least two reception paths, one AD converter per reception path, and a digital signal processing unit. The filters are coupled to a common signal source in order to receive the analog signal having the frequency band to be digitized and are designed to divide the frequency band to be digitized into at least two sub-bands for the at least two reception paths. The analog-digital converters are designed to digitize the signals of the at least two sub-frequency bands. The digital signal processing unit is coupled to the at least two analog-digital converters in order to receive the at least two digitized signals and to merge the at least two signals to be digitized. The at least two filters are designed, in respect of the filter characteristics thereof, such that the at least two sub-frequency bands have a relative bandwidth of < 1:2.