Receiver Equalization for Out-of-Channel Interference Cancellation
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Solution Overview
Problem
Narrowband receivers face challenges in maintaining signal integrity due to nonlinear distortion caused by out-of-channel interferers, which create in-channel intermodulation products that degrade the spurious-free dynamic range and are difficult to distinguish from desired signals.
Innovation Solution
A method and system utilizing a wideband receiver to estimate and cancel undesired in-channel responses in a narrowband receiver by determining out-of-channel interferers and applying a predetermined model to correct the output signal, employing digital nonlinear equalization techniques and Volterra representations to model nonlinear behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrowband receiver is used to demodulate one channel, then channel selectivity is improved, but the spurious-free dynamic range deteriorates due to in-channel intermodulation products from out-of-channel signals
Solution Approach 1:
A wideband receiver acts as an intermediary device to detect out-of-channel interferers that would otherwise cause intermodulation products in the narrowband receiver. The wideband receiver captures signals across a broader frequency range, identifying interferers before they can corrupt the narrowband channel reception, thus protecting the spurious-free dynamic range while maintaining channel selectivity
Solution Approach 2:
The system uses feedback by continuously monitoring the wideband receiver's detection of out-of-channel signals and using this information to adjust or cancel intermodulation products in the narrowband receiver's output. This closed-loop approach allows the system to dynamically compensate for nonlinear distortion effects, maintaining both channel selectivity and spurious-free dynamic range
2Reliability
If a wideband receiver is used to detect out-of-channel interferers, then the spurious-free dynamic range of the narrowband receiver is improved, but the device complexity increases due to requiring multiple receivers and signal processing systems
Solution Approach 1:
The wideband receiver is designed to serve multiple functions: it not only detects out-of-channel interferers for the narrowband receiver but can also independently process multiple narrowband channels. This multi-functionality reduces the need for separate dedicated interferer detection systems for each channel, thereby managing overall system complexity while maintaining improved spurious-free dynamic range
Solution Approach 2:
The system merges the interferer detection function with the channel reception function by using the wideband receiver to simultaneously perform broad spectrum monitoring and specific channel demodulation. This consolidation eliminates the need for completely separate interferer detection hardware, reducing device complexity while still providing the spurious-free dynamic range improvement
3Reliability
If nonlinear distortion compensation is applied to remove intermodulation products, then signal integrity is improved, but the difficulty of detecting and measuring interferers increases due to the need for predetermined models and estimates
Solution Approach 1:
The system performs preliminary action by using the wideband receiver to detect and characterize out-of-channel interferers before they can cause intermodulation distortion in the narrowband receiver. By identifying interferers in advance and estimating their impact using predetermined nonlinear models, the system simplifies the subsequent compensation process and makes interferer detection more straightforward
Data Source
AI summary
Methods and systems for equalization of a first receiver. A method may include receiving an input signal at the first receiver. The method may also include receiving the input signal at a second receiver. The method may further include determining, from an output response of the second receiver, an estimate of an out-of-channel interferer present in the input signal. The method may also include determining an estimate, of an undesired in-channel response of the first receiver to the out-of-channel interferer present in the input signal. The method may include applying the estimate, of the undesired in-channel response of the first receiver to the out-of-channel interferer present in the input signal, to an output signal of the first receiver to substantially cancel an instance of an undesired in-channel response of the first receiver to the out-of-channel interferer.